PNNL-70979 UC-8 1 0

Project Technical Information

Letter Report: Evaluation of Dryer/ Calciner Technologies for Testing

G. Sevigny

February 1996

Prepared for the U.S. Department of Energy under Contract DE-AC06-76RLO 1830

Pacific Northwest National Laboratory Richland, Washington 99352

R

PNNL- 10979 uc-810

Project Technical Information

Letter Report: Evaluation of Dryer/Calciner Technologies for Testing

G. Sevigny

February 1996

Prepared for the U.S. Department of Energy under Contract DE-AC06-76RLO 1830

Pacific Northwest National Laboratory Richland, Washington 99352

Reprint of historical document PVTD-C95M.W.C18. dated September 1995. Dad, formatting. and other conventions reflect standards at the original date of printing. Technical peer reviews and editorial reviews may not have been performed.

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor Battelle Memorial Institute, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy,.completenes, or.usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately own4 rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or Battelle Memorial Institute. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

PAClFlC NORTHWEST NATIONAL LABORATORY operated by BATTELLE

for the UNITED STATES DEPARTMENT OF ENERGY

under Contract DE-AC06-76RLO 7830

Printed in the United States of America

Available to DOE and DOE contractors from the Office of Scientific and Technical Information, P.O. Box 62, Oak Ridge, TN 37831;

prices available from (61 5) 576-8401.

Available to the public from the National Technical Information Service, US. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 221 61

@ The document was printed on recycled paper.

TABLE OF CONTENTS

INTRODUCTION . . . . . . . 4 . . . . . . . . . . . . . .

. *

. . . . . . . . . . . .

. .

. . . . . .

. * . . . .

.

.

. .

.

TECHNOLOGY DESCR I PT I ONS SPRAY CALCINER . . FLUID BED CALCINERS PLASMA CALCINATION

. 5 * 5 . 7 . a . a . 11 WIPED FILM EVAPORATOR ROTARY CALCINER . . .

ISSUES TO BE RESOLVED . . . 13 . . . . WFE

. . . ADVANTAGES AND DISADVANTAGES OF THE OR CALCINERS . 16 -

. 17

. 20

. 21

RECOMMENDATIONS FOR FUTURE TESTING AND RESOLVING ISSUES

. CONCLUSIONS . . . . . . . REFERENCES . . . . . . . ,APPENDIX A - BIBLIOGRAPHY

. . . . . . . . . . . . . * . . . .

FIGURES AND TABLES

Figure 1 . Wiped Film Evaporator Schematic . . . . . . . . . . . . . . . . 9 Figure 2 . Rotary Calciner Components . . . . . . . . . . . . . . . . . . . 12 Table 1 . Issues and Suggested Testing Scale . . . . . . . . . . . . . . . 20 .

INTRODUCTION

This letter report describes some past experiences on the drying and . calcination of radioactive materials or corresponding simulants and the information needed from testing. The report also includes an assessment of informational needs including possible impacts to a full-scale plant. This includes reliabil ity, maintenance, and overall size versus throughput. Much of the material was previously compiled and reported by Mike Ell iott of PNL “Melter Performance Assessment” and Larry Eisenstatt o f SEG on contract to WHC in a letter to Rod Powell. Also, an annotated bibliography was prepared by . Reagan Seymour of WHC and the bibliography is shown in Appendix A.

Descriptions o f the drying and calciner technologies, development status, advantages and disadvantages o f using a WFE or calciner, and recommendations for future testing are discussed in this report.

The vitrification of high level waste consists of various system designs. The designs in the United States o f America have been centered around continuous slurry fed melters since the earlier 1980‘s. Other systems involving calciners or dryers and semi -batch melters were tested earlier, but abandoned in favor of the simple s’lurry fed melter with robust operation and good glass quality. The system designs were based on relatively small glass throughput compared t o the present 10 to 20 ton/day throughput projected for the current high level waste plant. The calciner or dryer/melter system may provide a smaller footprint using more energy efficient processes than the simple slurry fed melter. The more complex system may provide advantages over a large slurry fed system that outweigh the disadvantages of a more complex system. The basic functions o f the flowsheet are to provide a high quality vitreous product in a reliable, reproducible manner as cost effectively as possible. The basic requirements are to produce a vitreous product acceptable for storage and disposal at the high level repository while complying with all radioactive and chemical permits. The dryer or calciner function is to produce a dry eas i 1 y hand1 ed product, i ncrease si gni f i cant 1 y the me7 ter production rate, and be less expensive than a simple slurry fed melter,

The flowsheet for the Hanford vitrification system includes an evaporator for concentrating the slurry from the pretreatment process, a1 though other methods of dewatering are being considered. The current characterization information suggests the vitrification plant will receive a slurry containing about 5 to 15% solids. The solids will have been washed numerous times removing the majority o f the soluble components. The concentration o f solids is based on initial testing indicating the concentration level at which the material can be hand’led easily in agitated tanks and transfer lines. The evaporator system would concentrate the material to a higher level and probably include the addition of glass formers. This material is pumped to the drying, calcining, or vitrification unit for processing. The glass formers can be added before or after the drying or calcining unit. Control of the final product quality from the melter may be more difficult if the glass formers are added after calcination but the feed stream would be smaller and less abrasive.

’

’

-

4

TECHNOLOGY DhSCRl PT I ONS

Waste dryfng and calcining can be accomplished by using wiped film evaporators (WE) , screw dryers , f i 1 ter dryers , tray dryers , rotary cal ci ners , spray calciners, fluidized bed calciners, and plasma calciners.

Combustion fuel heated units were not considered because of the additional offgas produced and because of the need for additional safety requirements.

Small electric rotary calciners have many years experience being operated remotely in high-level waste vitrification facilities. The waste processed was acidic with small quantities of undissolved solids. Hanford waste is initSally an alkaline stream with large quantities of undissolved solids. The rotary calciners require less building height and produce larger particles than spray calciners (Hull 1981). Therefore, for this report the rotary calciner is considered the basis for comparison.

Ft’lter dryers are not included in this evaluation for removing liquids because existing data indicates the primary particles in the slurries are very small, and may form compressible flocs. These are very difficult to filter and dead end fil tration is not presently considered the primary sol id-1 iquid separation device. If a filter were to be used that caused the formation of a non- pumpable cake, filter dryers should be considered as a viable final separation step in the vitrification cells instead of having the pretreatment process separating the solids and sluicing them from the filter for transportation. No previous process experience with Hanford type waste was identified.

Screw dryers were also not included because the experience with large systems for this type of appl ication were not found. at Hanford for small acid streams in the Plutonium Finishing Plant. experience was not directly appl icable.

Screw calciners have been used The

Tray and belt dryers typically use large quantities of air for drying which is considered undesirable for a radioactive system with rigid requirements on offgas cleanliness. The large quantities o f air could be and are recirculated but this is a complication to the overall process. wet solids that do not flow well instead of pumpable fluid streams. Little experience was found on fluid or radioactive waste systems. Therefore, these technologies were not considered further.

Agitated drying is a batch system for drying material in an agitated vessel. It has long residence times and different methods o f agitation as compared to a wiped film evaporator. The batch system has better processing flexibility. Disadvantages include not having the capability to be directly coupled to the melter and having periodic downtime for unloading that would decrease its availability. Therefore, it should not be considered further for pilot scale testing or plant operations. to obtain basic drying properties.

The standard use is for

Laboratory testing information would be valuable

5

. -

SPRAY CALCINER

Spray dryer/calciners are efficient devices providing the material to be dried can be atomized effectively w i t h o u t clogging o r abrading the nozzle, and solids carryover can be controlled easily. In comparison t o the rotary calciner, spray calciners are bulky, w i t h low energy efficiency, and produce a low density particulate product. There are h igh throughput designs that minimize some of the caking problems found i n other calciners. Spray calciners have been used for calcination of simulated waste slurries (Dierks 1980, Holton 1981, Larson 1976) and for actual waste i n a small demonstration system fo r Waste Solidification Engineering Prototypes (WSEP) project (Schneider 1969). A spray calciner consists of a spray chamber, cone section, vibrators, and gas f i l t e r assembly. A spray nozzle typically uses high velocity a i r t o atomize the waste slurry flowing i n t o the heated chamber where the water is evaporated and the so l ids dried. A combination of convective and radiant heat transfer from the heated walls is used t o dry and calcine the waste. The walls can be heated by a number of methods, b u t past experience is based on electrically resistance heaters outside the chamber walls.

I

After calcining, a large percentage of the particles formed are entrained and need t o be removed by cyclones and/or blowback f i l t e rs . The calcine then f lows i n t o a cone section a t the bottom for collection o r directly i n t o a melter. Glass formers can be added before or after calcining, bu t previous experience indicates the calciner operates better w i t h the glass formers added after cal ci nation ,

Past testing a t PNL has indicated the need for high efficiency corrosion resistant f i l t e r s a t the outlet t o control the fine particuTate produced. I f the nozzle atomization does not work correctly because of partial plugging or improper operation the calciner will 1 i kely plug causing extensive maintenance problems, The waste slurry w i t h glass formers added is very abrasive and causes operating problems for the spray nozzle a1 though most abrasion problems were solved by using a ceramic spray nozzle. Recently, a private company has used a sonic horn t o atomize low level waste simulant i n a combustion fired calciner test . The atomization was efficient, and the particulate produced was very fine. Radioactive acid waste was processed i n a 2 m h igh by 0.56 m diameter spray calciner for the WSEP project. The furnace operated a t 600 t o 800°C w i t h three zones of electric heaters. The calciner was directed coupled t o an induction heated melter. The calciner was equipped w i t h sintered metal f i l t e r s t h a t needed infrequent l i q u i d cleaning i n addition t o a i r blowback. The calciner operated a t 17 t o 36 l / h w i t h acid feeds and operated well except when sulfate levels were around 0.5M. problems and a h igh condensation p o i n t for sulfuric acid. As mentioned earlier a cri t ical requirement was good atomization of the feed especially i n a small system where the distance from the spray nozzles t o the walls is not very large.

The sulfate caused f i l t e r plugging

The large scale spray calciner tested a t PNL had calcination chamPer 3.2 m high, and 0.91 m i n diameter. The calcination chamber had 9.15 m of heat

6

transfer area w i t h a 0.64 cm thick stainless steel wall. I t used four zones of heaters w i t h the capability o f 150 kW each and a maximum temperature of 100O'C. The processing rate was about 300 l /h o f slurry producing 21 Kg/h of calcine from acid waste. The blowback f i l t e r s were 316 SS w i t h a 10 urn pore size. The calciner also used two vibrators t o help prevent bui ld-up of particulate i n the chamber. The calciner was directly coupled t o a joule heated melter and performed adequately. There was severe corrosion of the f i l t e r s and nozzles which were believed t o be controllable by selection of the. proper materials o f construction and better control of the operating parameters (Larson 1976).

FLUID BED CALCINERS

A f l u i d bed calciner consists of a heated chamber w i t h a d i s t r i b u t i o n screen on the bottom, and an inert bed (e.g., si l ica). The d i s t r i b u t i o n screen is used t o distribute the fluidizing air , collect large product particulate, and contain the bed during down times. The inert bed enhances heat transfer t o the feed material and provides some control o f the product particle size. The feed solution i.s sprayed i n t o the bed where i t is dried directly o r coats the bed particles, agglomerates, drys, and is abraded off because of collisions w i t h other particles.

F lu id bed calcination is a proven process using combustion fuels and air as the f lu id iz ing medium and energy source. Many variations on the bed material and heating method are available, bu t have not been used for calcining simulated Hanford type waste. Allied Chemical Corporation Performed an evaluation of heating methods for a new calciner a t the Idaho Falls plant and concluded direct combustion was superior t o hot a i r fluidization, steam fluidization, or offgas recycle w i t h hot a i r and in-bed electric heat(Freeby 1974). Extensive experience a t Idaho National Engineering Laboratory exists for processing acid waste using combustion fuels. vendors has been shown i n providing a fluidized bed system using electric heat sources for processing h i g h level waste supernate a t Hanford.

Interest from private

The tes ts a t Idaho indicate success w i t h acid feeds containing up t o 0.2 M Na . and up t o 1.1 M Na w i t h additives such as iron t o control sodium nitrate

formation (Freeby 1975). The problems noted were feed nozzle plugging and excessive agglomeration i n the bed. The calcination was performed using 4 and 12 in . diameter calciners, The calciner was heated using combustible fuel.

PNL tested a calciner vessel w i t h a 1.7 m total height and a 17-cm square cross section below a 19-cm square section -(Bjorklund 1976). The d i s t r i b u t o r plate had one hundred 0.12 cm holes on a 1.8 cm square g r i d pattern. An air atomized spray nozzle was supplied w i t h feed from a recirculation loop w i t h a centrifugal pump. The offgas flows through a cyclone chamber t o the sintered metal f i l t e rs . The processing rate was about 20 l/h w i t h acid feed containing around 150 g oxide/l. The product contains a wide variety of particles sizes from

The f lu id bed c a l c i n e r s can be operated w i t h hot wal l s o r a preheated a i r stream t o provide energy, but d e t a i l e d information on previous experience w i t h nuclear waste was not found. Fluidized bed c a l c i n e r s should be considered because of its po ten t i a l f o r high throughput, no moving parts, and p a r t i c l e sizes i n a range that should be easy t o handle.

PLASMA CALCINATION

The plasma to rch provides a high temperature energy source from compact equipment wi thout t h e use o f combustion fuels by using electricity t o c r e a t e a high temperature plasma i n an inept gas stream. The energy is t r a n s f e r r e d t o the product by the flowing gas. I t is t y p i c a l l y used f o r h igh temperature app l i ca t ions such a s c u t t i n g metal. A non-tsansferred plasma to rch has been used a s the heat source f o r a pseudo spray c a l c i n e r t es t f o r unwashed Hanford type waste containing Targe q u a n t i t i e s of Na (Goheen 1995). The goal o f the test was t o produce a calcined product w i t h a different chemical form o f aluminum hydroxide t o enhance the d i s so lu t ion of aluminum using sodium hydroxide. production r a t e o f a j o u l e heated s l u r r y fed melters by install ing them in the plenum space. The to rch could be used t o boost the melter production r a t e , bu t previous tests encountered numerous ret i ab i l i t y problems. Commerci a1 non- t r a n s f e r r e d plasma a r c systems a l s o need a l o t of maintenance time f o r the e l ec t rodes and plasma heads. Therefore, the plasma to rch is not recommended a s p a r t o f the c a l c i n a t i o n system f o r high leve l waste a t Hanford.

Plasma torches have a l s o been used t o directly boost the

WIPED FILM EVAPORATOR

Wiped f i l m evaporators can dry d i l u t e l i q u i d s t o powders and should be ab le t o dry high-level waste feed (Westinghouse Hanford Co. 1994). A WFE is constructed of a s t r a i g h t o r tapered l a r g e diameter pipe t h a t can be or ien ted either hor i zon ta l ly o r v e r t i c a l l y (Perry and Chilton 1973). The inside wall o f the pipe se rves a s the heat t r a n s f e r surface. Liquid i s spread on the inner surface by a r o t a t i n g assembly of blades tha t has a c l o s e to l e rance t o the wall o r a c t u a l l y rides on the film of l iquid. High a g i t a t i o n from the assembly r o t a t i n g a t a t i p speed o f up t o 12 m/sec (40 ft/sec) coupled w i t h power i n t e n s i t i e s of 2 t o 20 kW/m2 (0.25 t o 2.5 hp/ft2) g ives i t the c a p a b i l i t y t o dry extremely viscous l i qu ids . Residence times are of the order of only a few seconds. LCI Corporation (formerly LUWA) recommended t h a t Hanford waste be dried w i t h a v e r t i c a l WFE direct ly coupled t o a melter. LCf v e r t i c a l evaporator. Vert ical WFEs have less accumulation of dried phases than horizontal evaporators because the dried waste can break free and f a l l out of the e x i t . Also f o r a given diameter, v e r t i c a l u n i t s dry f a s t e r than horizontal ones, and therefore , have a higher throughput per u n i t volume. The waste should be dried t o a dry, flowable powder rather than t o chunks o r pas te t h a t could plug the discharge. If i t is decided t h a t the Hanford system will dry the waste t o a paste, r a t h e r t h a n t o a powder ( f o r example t o reduce the carry-over from the melter), the evaporator design must not have any

Figure 1 presents a schematic of

obstructions i n the ex5.t. This i s expected t o be more difficult t o control because of the radiant heat from the melter that would cause additional dpying. Such designs are available but would require demonstration w i t h waste types a t Hanford (Glover 1994).

Figure 1 - Wiped F i l m Evaporator Schematic For dilute waste streams an LCI WFE can remove 200 kg of water/hr/m' of heat transfer surface (40 1 bs/hr/ft2) (Glover 1994). In vertical evaporators the heat transfer surface can be up t o 40 mz (400 ft'). Horizontal systems can have a heat transfer surface up t o 7 m2 (80 ft'). If a wet granulated solid i s fed to the WFE, the water evaporation rate drops to 50 kg/hr/m2 (10 lbs/hr/ft2). According t o the Tank Waste Remediation System Process Flowsheet, (Orme 1994) the melter feed after glass former addition ( w i t h o u t an evaporator present) w i l l be dilute, greater than 70 w t % water. For a glass generation rate o f 400 kg/hr, about 2000 kg/hr o f feed will be processed. Therefore? one vert.ica1 WFE would be sufficient t o dry the high-level waste; one horizontal u n i t may be sufficient, but i t s capacity limit will be approached.

9

The r e l i a b i l i t y o f WFEs should be good based on uses i n industry and t e s t i n g t o da t e (Westinghouse Hanford Co. 1994). Wipe F i lm Evaporators a r e being used by commercial r ad ioac t ive waste processing companies t o d ry sludge f o r d i sposa l . However, the wiper blades need t o be ad jus ted o r replaced every s i x months, and mechanical seals have t o be serviced a t the same i n t e r v a l . The maintenance frequency needs t o be inves t iga ted f o r abras ive feeds. Other items such a s lubricated bear ings a l s o may limit t h e l i f e of the u n i t o r r equ i r e automated l u b r i c a t o r s . Remote maintenance is considered something tha t can be achieved w i t h manipula€ors. A remote design f o r a small u n i t is being tested at Oak Ridge National Laboratory (ORNL)(Boring 1994). However a large s c a l e remote u n i t design has not been completed and tested t o determine t h e effect on process a v a i l a b i l i t y . The a b i l i t y t o maintain opera t ions is an issue needing inves t iga t ion and evaluat ion. The se rv ices required t o operate the u n i t a r e instrumentat ion, steam, and electrical power.

P a c i f i c Northwest Laboratory (PNL) and Oak Ridge National Laboratory (ORNL) have been involved i n t e s t i n g WFEs f o r drying l i q u i d high-level waste.

PNL tested drying simulated PUREX so lu t ions (I t o 3 molar nitric ac id) i n horizontal and v e r t i c a l WFEs.

PNL's horizontal WFE had a hea t t r a n s f e r a r ea of 0.5 m2 (5 ft2) and had a t i p speed o f 6.7 m/sec (22 ft/sec) resulting from the fou r paddle r o t o r opera t ing a t 450 rpm (Dierks and Bonner 1975). The waste feed entered the evaporator near bo i l ing a t the l a r g e r end o f the drum t h a t was tapered about 2", and the dried feed exited ou t the smaller end. Water lubricated, g raph i t e - to - s t e l 1 i t e mechanical s e a l s on each end of the r o t o r shaft permitted the evaporator t o be operated a t -250 mm (-10 inches) water. The paddles were s t r a i g h t , 3 mm " (1/8 inch) thick, and p a r a l l e l t o the r o t o r axis . The c learance between the paddles and the evaporator wall was kept a t 0.8 mm (1/32 inch). A steam jacket surrounded the drum.

The simulated acid waste so lu t ion could only be concentrated t o 50 w t % s o l i d s , g r e a t e r than 50% s o l i d s caused operat ing problems w i t h the WFE. A t less than 50% s o l i d s the concent ra te was f l u i d , but beyond t h a t i t became more l i k e a paste. As the 50% concentrat ion l eve l was approached, the torque required t o maintain the set r o t o r speed increased sharp ly and scraping sounds were heard from w i t h i n the evaporator. Examination showed tha t a hard s c a l e co l l ec t ed between the paddles and the heat t r a n s f e r sur face from the midpoint o f the unit t o the discharge. The scraping sounds may have been the result of chunks of s c a l e having become lodged between the blades and hea t t r a n s f e r sur face as ind ica ted by c i rcumferent ia l s t r i a t i o n s .

When the concent ra te (5 5OwtX s o l i d s ) was discharged t o an unheated conta iner , there was no problem. However, when i t was fed directly t o a melter, the' r ad ian t hea t caused f u r t h e r evaporation and caking of the discharge nozzle u n t i l i t plugged. The X s o l i d s goal of g r e a t e r than 50% is expected t o be needed t o be a s i g n i f i c a n t bene f i t t o melter operat ion.

An experiment was performed i n which -325 mesh fri t was added t o the evaporator feed a t a frit t o metal oxide feed r a t i o of 2:l (McElroy 1975).

10

. The mixture was concentrated t o 35 w t % so l ids ' somewhat ge la t inous and d id not flow well out Other tests w i t h the following horizontal and performed (McElroy 1976):

when the concent ra te became of the evaporator.

vertical evaporators were

Rototherm Ar t i san - 0.08 d (0.88 ft2) horizontal LUWA D-210 - 1 m2 (10.8 ft2) horizontal LUWA CP-150 - 0,3 m2 (3 ft2) v e r t i c a l

Processing r a t e s were 22 t o 120 l/hr/m2 of evaporator heat transfer surface. The WFEs dr ied the waste t o 10% t o 20% l i q u i d (17 molar nitric ac id) g iv ing a free flowing powder w i t h 55 t o 58 w t % oxide. Oeni t ra t ion was minimal. The v e r t i c a l LUWA CP-150 had a higher solids bui ldup on the paddles of the r o t o r shaft t h a n either horizontal WFE,

ORMt is developing a v e r t i c a l WFE f o r concentrat ing r ad ioac t ive waste composed o f a 1M sodium n i t r a t e and 1M potassium n i t r a t e supernatant w i t h 0% t o 40 w t X s o l i d s cons i s t ing o f 74% calcium carbonate, 1894 magnesium hydroxide, and remainder aluminum hydroxide (Boring 1994). Tests a r e being performed t o produce a s ludge t h a t solidjfies on coo?ing and meets the requirements f o r disposal a t Waste I s o l a t i o n P i l o t Plant (WIPP). A t times a free flowing powder is obtained, b u t because this is not the desired product f o r the ORNL app l i ca t ion , so the operat ing condi t ions were changed during testing.

The evaporator shell is a 0.6 m (2 f t ) length o f 25 cm (10 in.) schedule 40 pipe. I t has a 0.5 m2 (5.4 ft2) heat t r a n s f e r area. Heat is suppl ied t o the WFE using 1.0 Mpasca? (150 psi) steam a t 181°C (358°F). The inside wall of the evaporatof has a set poin t o f 177°C (350°F) which has maintained a flow r a t e of simulated waste up t o 0.8 l /min (0.2 gpm). They use an ag i t a t ed kettle hea te r t o preheat their feed because sensible heat t a k e s 2X the amount of WFE heat t r a n s f e r a rea a s does l a t e n t heat. A t 3 l/min (0.8 gpm) the evaporator temperature i s 154°C (310°F). A t these temperatures t h e r e i s no t roub le w i t h low melting salts. The wiper t i p speed is 9 m/sec (30 ft/sec). The u n i t uses a 7.5 hp electric motor. The c learance between the blades and wall is 1.5 mm (0.060-in.), b u t the inves t iga to r s want t o lower i t t o 0.5 t o 1 nun (0.020 t o 0.040-in,). The blades v i b r a t e more when the simulated waste has no s o l i d s , suggesting t h a t the s o l i d p a r t i c l e s a c t as a lub r i can t . T h i s WFE has no lower bear ing allowing the blade assembly t o be remotely removable.

ROTARY CALC INER

The r o t a r y c a l c i n e r s used a t the v i t r i f i c a t i o n f a c i l i t i e s i n LaHague, France and S e l l a f i e l d , England a r e 3 in long by 0.3 m diameter pipes f a b r i c a t e d from a l loy Uranus 2520 (Moncouyoux, e t a l . 1991). Figure 2 shows the components of the r o t a r y c a l c i n e r (Chapman 1983). They r o t a t e a t 30 rpm and a r e t i l t e d about 3" from the horizontal such t h a t the feed slowly flows down. A 2.5 m long rabble bar inside the tube breaks up the c a l c i n e and keeps i t from sticking t o the walls. A fou r zone 94 kW r e s i s t a n c e furnace (two 32 kW and two 15 kW zones) hea t s the tube. The c a l c i n e r has a r e l i a b l e feed system f o r

11

l i q u i d waste, b u t would not be suitable for h igh s o l i d s slurries. Once the waste has been evaporated, calcining takes place a t 400°C for five minutes. Graphite sealing rings in each of the calciner end f i t t ings provide leak tightness allowing i t t o be operated under a vacuum of -1 kPa. The evaporative capacity i s 60 l/hr (70 l/hr w i t h recycle), b u t larger ones could be designed and b u i l t . Waste is fed t o the calciner through the upper end by P measuring wheel w i t h the amount fed determined by monitoring the revolutions. f i t t i n g . Frit is added through an a i r lock a t the calciner lower end

Figure 2 - Rotary Calciner Components A melter t h a t generates 200 kg/hr of glass would require a 250 t o 500 l/hr calciner, depending on the waste loading. T h i s is a five t o ten times increase over the current design.

12

Two main parts need to be replaced every six months .in the rotary calciner: the graphite seals and the rollers. Other rotary calciner parts usually last more than five years.

Rotary calciners have been used at Marcoule, France on a pilot scale in a radioactive environment starting in 1978, (Saverot and Laurent 1992). A l s o , they have been in use to treat acidic high-level waste at 50 l/hr in LaHague, France since 1989 and Sellafield, England starting in 1990 (Houghton 1992). The LaHague calciner is capable of 70 l/hr; treating 50 l/hr of waste generates 25 kg/hr of glass. Increasing the calciner diameter from 30 cm t o 40 cm would increase the glass generation rate from 25 kg/h to 45 kg/hr using approximations based on the square o f the diameter or directly proportional to the cross sectional area (Perrys 5th addition).

Hanford waste is a1 kal ine and incl udes organic compounds. When a1 kal i ne metals constitute 50% o f the waste, they can cause caking in the rotary calciner. This is probably due to the waste becoming sticky as it is heated through a temperature region lower than calcining temperatures. To prevent this caking aluminum can be added to the waste to achieve an aluminum to alkaline ratio o f 0.3 (molar). The current blended waste has considerable amounts of aluminum although it may be in a mineralized form. In other acid waste pi lot tests and 1 aboratory hydroxide simul ant tests, the addition of sugar has help break o f caking during calcining operations and should be considered in future tests. A test on Savannah River High Level waste indicated the alkaline waste could not be calcined with frit addition before calcination (Hull 1981). The frit had a much lower melting point than frits currently proposed for the high temperature melters and lower then the proposed frit for the Hanford Waste Vitrification Plant 1150°C melter. The rotary calciner is a very good candidate for calcination as long as maintenance and caking do not severely reduce equipment availabil ity. The effect on the typical canyon design would be minimal since the overall height would be within other equipment requirements.

In summary the systems described above have potential and some previous experience drying or calcining materials similar to the current proposed high level vitrification stream at Hanford. However the feed properties have some significant differences that have cause processing difficulties in the past. The main difficulties have been caking and/or plugging of the process equipment.

The processing systems have different processing issues. Many require atomization o f the feed slurry for drying to avoid the formation of hard cakes. Others rely on mechanical forces to break of the crusty material being formed and often using chemical additives to assist in the process. The equipment ability to operate reliably over a range of conditions without plugging or corroding is a key issue in demonstrating an improvement over a single slurry fed melter in addition to processing rate enhancements.

13

ISSUES TO BE RESOLYED

Before drying or calcination equipment is used in a high-level waste vitrification facility the following concerns need to be considered. Most o f the issues can be resolved by performing tests on simulated waste. them can only be definitively addressed after the melter is selected.

DRYING AND CALCINATION EQUIPMENT ISSUES IN GENERAL

Some of

Additional particulate entrainment from the melter caused by dry sol ids feeding needs to be determined. The off-gas and waste treatment systems would have. to be designed tu capture and recycl e ~ these part i cl es directly using hot filters or indirectly using filters.or wet scrubbers. For direct recycle, filter blinding and operating life are areas requiring information. solids, and the variations in the melter feed are issues as these recycle streams are returned to the process in batches.

Melter production increases by feeding dried or calcined waste requires verification. The value has not been determined for blended Hanford wastes.

For an indirect system, the handling of the

Processabil i ty of Hanford waste needs testing over a wide range. of expected Hanford waste compositions, generally up to pilot-scale. Almost all of the testing completed thus far has been on nitric acid waste; alkaline Hanford waste is untested. Tests might show that acid needs to be added to the Hanford waste which is a disadvantage overall because of the additional evaporation capacity needed and the increase in acid gas generation from the high temperature equipment;

Space savings, facility design constraifits, operational simp1 icity, reduced risk, and reduced overall cost for the optimum combination o f calciner and me1 ter need to be quantified.

Remote design features for much of the drying and calcining equipment is needed or the impact of replacing and disposing o f major parts needs evaluation. This evaluation would need to be performed in conjunction with the philosophy of remote maintenance (e.g., canyon remote versus hot cells serviced with robotic arms).

Glass former addition before drying or calcining requires evaluation as to the potential impact on glass qual ity and equipment re1 i abil i ty. The information available would indicate the frit should not be calcined with the waste because of an abrasion and caking problems.

Destruction of nitrates in the calciner and NOx emissions data from testing is needed to evaluate the technology.

14

WIPED FILM EVAPORATOR

Do salts with low melt-ing temperatures in Hanford waste cause plugging? Sodium nitrate/nitrite are such salts that are in the waste but in much lower quantities then the test described above; other salts may be present. Hanford HLW is not expected to have low melting salts.

Tests o f direct and indirect coupling to the melter are needed to allow f o r the most reliable, and cost-effective configuration of a WFE and me1 ter

Product characteristics (dryness, particle size, particle density, abrasiveness, etc.) that can be produced under various operating conditions need to be determined by pilot scale or larger tests.

Remote design features are needed for adjusting the wiper blades and rep1 acing seals

formation of cake on the blades and heat transfer surfaces that is not easy to remove is a likely possibility and testing is needed to determine if operating parameters can be adjusted to minimize the possi bil i ty.

Corrosionjerosion rates of the blades and' other materials contacting the waste slurries require quantification to estimate design 1 ife and 1 ife cycle costs.

The production,rate needs to be determined on a test system of sufficient size to allow scale-up calculations.

Testing is needed to determine the effect on production rates when the typically used preheater is not used. The existing preheater design may not be re1 i able for a1 kal ine feeds.

ROTARY CALC INER

The production capacity of the calciner requires testing using Hanford type wastes including expected variations that could impact the calciner production rate and reliability.

Quantity o f entrained particulate leaving the calciner and the impact on secondary treatment systems requires evaluation.

The scale-up capability of the calciner is undemonstrated for this type of waste. Many commercial plants exist with greater capacity but are not set up for remote maintenance. The Hanford melter is expected to have a capacity o f 400 to 800 kg/hr of glass, whereas the maximum capacity expected (but not demonstrated) from current design concepts is 90 kg/hr.

15

The configuration of the calciner and melter (calciner tilted 3" as at LaHague, direct or indirect coupling to the melter, glass formers added before or after the calciner, number of calciners per me1 ter) needs to be evaluated for functionality and impact on plant operations.

Testing is needed to determine the calciners ability to prevent scale formation by mechanically means and/or chemical additions.

Maintenance requirements for the calc.iner and seals need to be determined based on past experience and comparison with shorter tests on Hanford waste.

SPRAY CALCINER

Ability of spray nozzle design to operate reliably and control the product particle size needs to tested with the simulated Hanford feed.

Production rates for the calciner need to be tested with simulated Hanford feed and evaluated versus requirements that would be imposed on the cell height.

Life o f the spray nozzle and the require solids separation device (e.g., cyclones, filters) needs to be evaluated based on tests with simulated Hanford feed.

FLUID BED CALCINER

Production rates using an electrically heated (includes induction heating) chamber and/or fluidizing air requires determination based on testing.

Particulate size distribution o f the product is needed

Operating life of bed material (SiO, recommended)needs to be determined based on testing to evaluate functionality.

Testing of the systems under a range of conditions using Hanford type feeds are needed to ensure operating conditions can be maintained that prevent an excessive cake build-up,

ADVANTAGES AND DISADVANTAGES OF THE'WFE OR CALCINERS

The main advantage of using a dryer or calciner is that it would increase the glass melt rate for a given melter size. Therefore, the number and/or sizes of melters that would be needed to vitrify the Hanford waste would be reduced. Operation of the melter may be simpler, because the temperature gradients within the melter would not be as great and the atmosphere may not be as

,16

corrosive. Dry feed would allow the operation of some high temperature melters currently not considered viable for a slurry feeding.

The disadvantage for using a secondary device is the added monitoring and maintenance needed by another piece o f processing equipment. If the equipment is directly coupled, the calciner/dryer reliabil i ty affects the availability o f the entire vitrification system. For indirectly coupled equipment added lag starage is needed and the material would need t o be reheated i n the melter after storage. The wiped film evaporator has advantages i n the efficient heat transfer from an agitated surface and the lower operating temperatures typically allow for longer operating l i fe . The Tower operating temperature also allows for the use o f steam i n the cell t h a t results i n more reliable in-cell equipment than high temperature electrically heated equipment. The operation a1 so allows for greater control over the moisture i n the product that may allow easier handling than a very dry powder. The disadvantages are the blades and seal require considerable maintenance and a ‘dry” product may be diff icul t t o produce for some feeds. The final product will have more unreacted chemicals than the calciners b u t this could be an advantage or disadvantage i n the melter. The wipe film evaporator shows a Tot o f potential for processing Hanford waste rapidly i n a small volume. The main concerns are the maintenance and reliabil i ty of the equipment.

Comparing the calciners w i t h the WE has relative advantages and disadvantages. less of a thermal load on the melter, because less water would be sent t o the melter, and the calcine would be preheated t o a higher temperature. The will likely be small. The additional latent heat would only be useful i f the calciner were directly coupled t o the-melter. Also, the calciner would require more energy and operate a t a higher temperature which may mean faster corrosion and shorter equipment l i fe . The failed equipment will have t o be disposed of as contaminated waste w i t h costs varying greater depending on decontamination efforts and waste classification.

Use o f the calciner rather than the evaporator would place

. difference is expected t o be small because the difference i n water content

The rotary calciner has many years of experience i n processing waste feeds of a different nature, b u t is well developed system for maintenance i n cells w i t h robotic arms. The system does produce large quantities of small particles tha t can be entrained bu t not as much as i n the spray calciner. The rotary calciner has a rotating parts and an electrfc heater susceptible t o failure although experience on the current system is good. A large remote system f a r use a t Hanford has n o t been designed although commercial rotary calciners can be very large. The rotary calciner should be tested w i t h simulated Hanford waste as a potential enhancement t o the vitrification system. Spray calciner advantages include the a b i l i t y t o prevent cake formation by drying i n droplets. The droplets provide a h i g h surface area w i t h a short residence i n the heated vessel t o provide a high throughput. The disadvantages relative t o the rotary calciner are the production of fine particulate that are easily entrained i n the calciner and subsequently i n the melter. This almost requires the system t o be coupled t o minimize the cost of

17

particulate removal equipment such as sintered metal filters. The short residence time of the droplets in the heating chamber also requires more precise control to prevent wet droplets for impacting the sides and causing build-up within the vessel. Extensive solids build-up on the wall has occurred in previous tests. The spray calciner also requires a higher pressure pump than the rotary calciner or use o f another high'energy device (e.g. , centrifugal, sonic atomizer) to ensure adequate atomization of the feed slurry. The spray nozzle can be an unreliable device for slurry with high abrasive solids content. The spray calciner is a good process for testing provided the design considers re1 fable fluid atomization, high efficiency collection o f particulate, direct coupling to the melter, and cell height is not a major concern.

.The fluidized bed advantages as compared to the rotary calciner are fewer moving parts and may be less likely to form hard dry solids in the processing equipment. The fluidized bed is an efficient system with a l o t of experience processing acid waste in combustion fired unit at INEL. However, experience with electrically generated heat and requirements for particulate capture are a disadvantage.

RECOMMENDATIONS FOR FUTURE TESTING AND RESOLVING ISSUES

Tests need to be performed to evaluate the technology and decide the specific type of equipment to use in the high-level waste vitrification facility, e.g., WFE, or rotary, spray, fluidized bed, or plasma calciners. Testing performed thus far on the use of a WFE or calciner to increase a glass melter throughput included too many varying parameters other than moisture in the feed to quantify the effect. Also, there is a dearth of data on the ability to calcine or dry Hanford waste, which is alkaline and has a broad range of characteristics. Previous testing was generally performed using acid feed. The small number o f experiments performed using a1 kal ine feed can be used to demonstrate feasi bil i ty a1 though they were performed on waste with compositions significantly different from the feed presently projected for the Hanford high level vitrification plant. (e.g,, see Allemann and Johnson, 1961; and Hull, 1981).

The test strategy should reflect that testing costs escalate as test size increases, and that radioactive testing is much more expensive than nonradioactive testing. Therefore, to the extent possible, the smallest scale testing will be used to resolve the issues identified above using non- radioactive HLW feed simulants. Radioactive tests should be 1 imited to laboratory scale tests to compare the chemical and physical properties of the simul ant and the actual waste materi a1 . Laboratory and bench-scale testing generally focus on process chemistry and effects of changes in variables over a relatively wide range. typically investigates the process considerations and identifies process and equipment problems. Because costs per data point escalate with size, tests with the 1 arger-scal e systems are generally 1 imi ted to verifying scale-up behavior and at a relatively small number of conditions.

Pilot-scale

ia

The objective of the testing is to confirm that small-scale radioactive testing ca.n be extrapolated to full -scale plant operation by performing laboratory, pilot, and full-scale testing on simulants. Once this is- demonstrated, other HWVP feeds need only be tested on scale sufficient to evaluate equipment operating parameters.

Drying and calcining tests, some coupled with the melter, need to be performed to respond to these matters. Some of the confirmatory testing needs to be performed at pilot to full scale as shown in Table 1 to substantiate that there are no problems with scale-up. Full scale testing could be preformed in the actual plant melter and the results would not be required for the next round o f evaluations. Design of the WFE and/or calciner systems needs to be initiated after initial bench or pilot scale tests are performed. The early design work i s needed so the integrated process system can be evaluated. Some of the pilot scale tests can'be performed by the potential equipment. vendors.

The results o f these tests will be used to evaluate and select the technology for drying or calcining the waste. As the testing program progresses, preliminary evaluations should be performed from time to time to help set the direction for remaining tests and focus the limt'ted funds to the most promising technologies and address the most significant issues.

Future evaluation criteria should be based on providing a system that increases melt rate, minimizes maintenance and facility needs. The expected increase in waste processing rate in the melter has the highest ranking, because it is the main reason for considering this equipment. Operating, maintenance, equipment disposal costs, followed by capital costs are next in importance, due to the need to keep the cost as low as practicable. Operating complexity and ease of interfacing with other systems measures the ability to provide a reliable process. The next decision point f o r the technologies should be based on information up to the Engineering DeveTopment stage as defined by demonstrating cost/benefit advantages, pilot scale testing success, and design features for a full scale unit.

Without performing any additional tests, the rotary calciner appears the best choice for a secondary system because of low height requirements; maintenance is not expected to be as intensive as the wiped film evaporator; process flexibility i s good; and the particle size is not expected to be exceptionally small. The wipe film evaporator is the recommended highly because the processing is fast, the processing conditions are milder than the calciners and has a lot of flexibility. cal ci ner i s a good choice with previous radioactive experience . If hard cake formation is a problem, the spray

19

.

Table 1 - Issues and Suggested Test ing Sca le Potenti a i issue

CONCLUSIONS

The r o t a r y c a l c i n e r , wiped film evaporator, f l u i d i z e d bed, and spray c a l c i n e r show promise f o r enhancing c o s t e f f e c t i v e production of l a r g e q u a n t i t i e s o f glass . Tests should be performed w i t h a simulated Hanford waste blend t o determine processing r a t e s f o r the dryer /ca lc iners and a dry fed melter. Fas te r waste processing r a t e s per equipment c o s t and cell space requirements may be sufficient t o j u s t i f y the e x t r a equipment opera t ions and maintenance a c t i v i t i e s t ha t would be required f o r a c a l c i n e r o r dryer . Additional t e s t i n g i s needed w i t h Hanford waste types t o be able t o perform the eva lua t ion . Minimal c a l c i n e r tests should be performed u n t i l production r a t e enhancements f o r a dry fed me1 ter a r e determined. Previous experiments i nd ica t e dry feed would increase me1 ter throughput s i g n i f i c a n t l y and the t o t a l c a p t i t a l and disposal c o s t s would be less.

20

However, operating costs maybe higher dryerlcalciners than the me1 ters because of maintenance requirements. Calciners provide a dryer product than WFEs. Therefore, the product from calciners should process faster in the me1 ter although the difference i s not expected to be significant.

Several experiments on drying simul ated radioactive waste have been performed with WFEs. They have indicated that they can remove a. large amount o f moisture and generate a product that should be able to be delivered to the melter. Although before a dryer/calciner is used, some testing and/or effort $n designing the interface between the WFE and melter will be required. Also, additional information on the operating life of components is needed to ensure the maintenance requirements do not signifixantly affect avail abil ity.

Particulate carry-over from the melter was a problem with dry feed to the melter (McElroy 1975). During the performance of some of the PNL tests, additional off-gas treatment equipment was needed and may be required for an uncoupled system (e.g., cyclones, sintered metal filters). Additional testing is needed to determine the required equipment. - Based on testing to date on alkaline feeds, no drying/calciner system currently developed has shown enough reliable operation to justify its use to reduce the melter size.

21

REFERENCES

Allemann, R. T o ; B, M. Johnson, Jr., February 1961, "Radiant-Heat Spray- Calcination Process for the Sol id Fixation of Radioactive Waste", HW-65806 PT 1, General Electric Hanford Atomic Products Operation, Richland, WA.

Bjorklund, W.J.; Nov. 1976, "Fluidized Bed Calcination Experience with a Simulated Commercial High-Level Nuclear Waste", BNWL-2138, Pacific Northwest Laboratories, Richl and, WA.

Boring, M; November 22, 1994, Oak Ridge National Laboratory, Oak Ridge, TN, personal communication.

Chapman, C. C.; 1983, "Comparison of the Rotary Calciner-Metallic Melter and the Slurry-Fed Ceramic Melter Technologies for Vitrifying West Valley High- Level Wastes", DOE/NE/44139-6, West Val ley Nuclear Services eo., West Valley, NY.

Chotin, M. M.; et al., 1982, "Industrial Operating Experience at the Marcoule Vitrification Facility", Proceedinas of the ANS ToDical Meetina on the Jreatment and Handlina o f Radioactive Wastes, Battelle Press, Richland, WA, p. 72.

Dierks, R. D,; and W . F. Bonner, 1975, "The Performance of a Wiped Film Evaporator with Simulated High Level Waste Slurries", BNWL-SA-5454, Pacific Northwest Laboratories, Richland, WA.

Dierks, R.D.; G.B. Mellinger; F.A. Miller, T.A. Nelson, W.J. Bjorklund, August 1980, "Investigation of Corrosion in a Spray Calciner/Ceramic Me1 ter Vitrification System", PNL 3406, Pacific Northwest Laboratories, Richland, WA.

Freeby, W.A.; D.W. Rhodes, S.S. B0dner;D.G. Swink, April 1974, 'Summary Evaluation of Candidate Fluid-Bed Sol idification Processes for Use in the NWCF", A1 1 i ed Chemical Corporation, ICP-1046, Idaho Fa1 1 s, 'Idaho

Freeby, W.A., June 1975, 'Interim Report - Fluidized Bed Calcination of Simulated High-Level Comerical Wastes", Technical Report - Idaho National Engineering Laboratory, ICP-1075, Idaho Fa1 1 s, Idaho

Glover, W; November 21 and December 13, 1994, LCI Corporation, Charlotte, NC, personal communi cations.

Goheen, R.S. ; R.P. Taylor, S.A. Pirzada, M. Manruque, January 1995, "Thermal Reconstitution of a Hanford Tank Waste Simulant Via Plasma Calcination" TWRSPP-95-003

Holton, L.K, 1981, "Behavior of Mercury and Iodine During Vitrification of Simulated Alkaline PUREX Waste", PNL-3964, Pacific Northwest Laboratory, Richl and, WA

Houghton, T. ; 1992, "Operational Experience at the Windscale Vitrification Plant, BNFL, Sellafield, Eng1and";proc eedinas of the International ToDical

22

m z Meetino on Nuclear nd H tru '9 , American Nuclear Society, LaGrange Park, IL, p.459.

H u l l , H. T.; February 11, 1981, "Trip Report, Envirotech - S a l t Lake City, Rotary K i l n Test, January 8-9, 1981", DPST-81-270, Savannah River Laboratory.

McElroy, J. L.; June 1975, "Quar te r ly Progress Report, Research and Development Activities, Waste Fixation Program, January through March 1975", BNWL-1908, Pacific Northwest l abora to r i e s , Richland, WA.

McElroy, J. 1. ; September 1975, "Quar te r ly Progress Report, Research and Development Activities, Waste Fixation Program, AprTl through June 1975", BNWL-1932, Pacific Northwest Laboratories Richland, WA.

McElroy, J. L. ; January 1976, "Quar te r ly Progress Report, Research and Development Activities, Waste Fixation Program, Ju ly through September 1975" , BNWL-1949, Pacific Northwest Laboratories, R i chl and, WA.

Larson, D.E. ; W.F. Bonner (comp), Nov. 1976, "High-Level Waste V i t r i f i c a t i o n by Spray Calcination/In-can melting", BNWL-2092, Pac i f i c Northwest Laboratories, Rich1 and, WA.

Moncouyoux, 3. P.; e t a1 ., 1991, "New V i t r i f i c a t i o n Techniques", CEA-CONF- 10556, Jn terna t iona l d e Conferenc r Fu 1 R r cessin n W t Manaaement, Sendai , Japan. Ome, Re M.; 2994, "TWRS Process Flowsheet", WHC-SD-WM-TI-613, Rev. 0, Westinghouse Hanford Co. , Richland, WA. Perry R. H.; and C. H. Chilton (eds.) , 1973, Chemical Enaineers' Handbook, f i f t h ed i t i on , McGraw-Hill Book Company, Neb York, p. 11-30.

Saverot, P. M.; and J. P. Laurent, 1992, "Class Quality for Long Term Disposal.. An Overview o f the v i t r i f i c a t i o n Experience i n France," Proceedinqs

Manaaement.Soectrum, American Nuclear Society, LaGrange Park, IL, p.453. p p

Schneider K.J., V.P. Kelly "Waste Sol iddf ica t ion Program - Design Features of Waste S o l i d i f i c a t i o n Engineering Prototypes" Volume 11, February 1969, BNW, BNWL-968, Pacific Northwest Laboratories, Richland, WA. Westinghouse Hanford Co., August/September 1994, "High-Level Waste Me1 ter System Assessment Workshop, Sal ance of P1 ant Package" , Data Package 1, Appendix 8, "Low-Temperature, Joule-Heated, Ceramic-tined Me1 ter: Evaporator Coupled t o Melter", Richland, WA.

23

Appendix A

CALCINER\DRYER ANNOTATED BIBLIOGRAPHY

Sasaki, N., H. Sasaka, M. Ohba, Y. Hasebe, H. Nagaki, and N. Tsunoda. “Solidification of High Level Waste (5) - Fluidized Bed Calcination o f Simulated High-Level Waste by the Continuous Inert Bed Concept”. Tokai

February, 1979, pp. 124-128. &l 978 . PNCT-831-78-01,

Simuuary

This paper from a semi-annual progress report discusses fluidized bed calcination o f high sodium bearing waste using the inert bed concept. study simulated high level waste was fed into a 4 inch diameter fluidized bed ea1 ciner .

In this

The major constituents in the simulated waste were Na, Fe, Ni, Cr, K, SP, Ba, Zr, Mo, Co, Te, Y , and a rare earth mix. inert bed and aluminum nitrate was introduced as an additive to promote cal ci nat i on.

Fused silica was used as the

The major findings o f the paper in relation to composition and the additives were that:

1. The fluidized bed calcination under continuous inert bed concept in which aluminum nitrate is used as an additive and fused silica as a fluidized bed particle would be recommendable for the operating procedure o f calcination o f high level liquid waste containing high sodium nitrate.

2. Aluminum nitrate should be added to the feed at greater than 0.1M while operating the calciner at >6OO0C.

2. Sasaki, N., H. Sakata, M. Ohba, N. Tsunoda, Y . Hoshino, and Y . +lasebe. ‘Solidification of High Level Waste (4) - Fluidized Bed Calcination o f Simulated High-Level Liquid Waste by the Attri tion-Elutri ation and Particle Growth Concepts”. T b 1. PNCT-831-78-02, Tokai , Japan, July, 1978, pp. 95-97.

Sumnary

This paper from a semi-annual progress report discusses fluidized bed calcination of high sodium bearing waste. waste was fed into a 4 inch diameter fluidized bed calciner.

In this study, simulated high level

The composition of the simulated feed was not available, but because this study was carried at the same facility it is likely that the composition 'is similar to reference one. Iron nitrate and aluminum nitrate were used as additives to suppress the effects of sodium nitrate on the fluid bed ea7 cf nation.

The. major findings o f the paper in relation to composition and the

f . Simulated high level waste with a 1M sodium concentration is feasible when more than 0.7M iron nitrate is added to the feed and the calciner is operated at >700°C.

additives were that:

2. Particle growth coricept is more appropriate than the attrition-

3. Simulated high level waste with 1M sodium concentration is feasible

elutriation concept in the operation of the fluidized bed.

when more than 0,40M aluminum nitrate i s added to the feed and the calciner is operated at >65OoC.

4, Severe feed nozzle plugging was observed in the operation of the fluidized bed calciner.

3. Abrams, C.S. and L.C. Witbeck. 'Sodium Waste Technology - a Summary Report". T V y . ANL-86-50, Argonne, Illinois, January, 1987.

Sununary

This report discusses, in part, the MEDEC (me1 t-drain-evaporation- calcination) as it relates to the calcination o f sodium by a rotary drum calciner. possibility o f calcining sodium bearing wastes in this calciner as part of the MEDEC process.

Pure sodium was injected into a rotary drum calciner to assess the

The major findings o f this study in relation to the rotary calciner and the sodium content were that:

1. At approximately 20% bed volume or higher, it was observed that the large batch wetted the entire bed and formed a large cohesive mass which eventually overloaded the machinery.

2. The drum seals performed well for awhile, but eventually leaked particulates into the process cell atmosphere.

3. Finely divided product carry over in the calciner off gas caused major plugging problems.

4. Newby, B.J. "Calcining Sodium-Bearing Waste by Blending with Zirconium F1 uoride Waste". Techn ical ReDort - Exxon Nuclear Idaho Comoany. ENICO- 1006, Idaho Fa1 1 s , Idaho, November, 1979.

Surnnary

This report covers the pilot plant work performed to develop a flowsheet for calcining sodium bearing waste based on biends with zirconium wastes. Calcining runs were carried out in ten and thirty centimeter diameter fluidized be# calciners. DTA-X-Ray was also carried out in support of the cal ci nation runs.

Two different concentrations o f the constituents in the simulated first cycle zirconium waste were blended with one composition o f simulated sodium bearing waste. The two different zirconium wastes were representative of waste tanks WM-182 and WM185 at Idaho Chemical Processing Plant (ICPP). The major constituents of the zirconium wastes were Zr, Al, 6, Fe, No3, and F, while the major constituents of the sodium bearing waste were Al, 6, Na, K, Mn, Hg, Fe, No3, Cl, PO,. Calcium nitrate was added to the feed to reduce C1 and F volatility. Technically speaking, the Zr wastes were also introduced as additives to promote calcination.

The major findings of this study in relation to composition and the additives were that:

1. Sodium bearing waste can be effectively calcined with blends of Zr and Na wastes containing up to 5.3 mol% Na. decreases substantially above this limit.

Fluidized bed operability

2. Introduction of calcium nitrate to the feed substantially reduces F and C1 volatility during calcination o f the waste blends. An optimum mole ratio of 0.70 Ca/F is recommended.

3. The undissolved solids content of Zr-Na waste blends containing a Ca/F mole ratio of 0.7 is sufficiently low so that plugging of calciner feed equipment is less of a problem.

5. Bjorkland, W.J. "Fluidized Bed Calcination Experience with Simulated Commercial High-Level Nuclear Waste". Technical Reoort - Pacific Northwest Laboratories. BNWL-2138, Rich1 and, Washington, November, 1976.

Sgmmary

In this report calcination of simulated high level wastes representative of those to be generated by commercial fuel reprocessors has been tested in fluidized bed calciner using an inert material. The inert material improves

the operation o f $he bed since particle size control is not required, a low inventory o f fission products is maintained in the bed, high sodium bearing wastes can be calcined, and high feed rates are possible.

Several compositions of simulated waste were used in this studied. However, each csmpositlon contained concentrations o f Na, Fe, Cr, Ni, PO,, Gd, fission products, actinides, and HNO,. The sodium concentration was the only species that was varied widely, since the primary objective of this study was to show that high sodium wastes could be calcinated by this method. No additives were used to effect calcination in this study.

The major findings of this study in relation to composition were that:

1. Continuous inert bed calcination provides a significantly improved operating technique when applied to commercial HLLW sol idification.

2. Sodium levels up to 1M are calcinable with fluidized bed calcination using an inerts,

6. Newby, B.JI "Laboratory Flowsheet Development for ICPP WM-183 Waste". Technical Reo ort - Idaho National Enaineerina Laboratory. ICP-1124, Idaho Falls, Idaho, October, 1977.

Smary

This report describes flowsheets that were being developed to calcine waste stored in Idaho Chemical Processing Plant (ICPP) waste tank WM-183 without fluidized bed agglomeration or excessive corrosion of the off gas system caused by the presence o f sodium nitrate and chloride respectively. Two flowsheets were being considered: (1) adding calcium nitrate to a blend o f WM-183 waste with zirconium fuel waste, (2) adding powdered iron and silver nitrate to WM-183 waste. DTA-X-Ray was used to evaluate the calcinability o f the waste in each flowsheet.

The major constituents of the WM-183 waste are Al, Na, I(, F, C1, NO,, SO,, PO,, Ca, Cr, Cu, Fe, Mg, Mn, Ni, and B.

The major conclusion drawn from this study in relation to composition and the additives were that:

1. DTA-X-Ray studies show that calcination of WM-183 waste without additives would cause agglomeration o f the fluidized bed particles.

2. DTA-X-Ray studies show that the addition o f powered iron or blending o f zirconium waste with WM-183 waste shows promise for eliminating agglomeration during calcination. In addition, adding iron powder to

commercial waste shows much greater promise f o r el iminat ing f l u id i zed bed p a r t i c l e agglomeration than adding i ron t o WM-183 waste.

3 . Gas evolved from adding powder t o WM-183 waste does not contain enough hydrogen t o const i tu te an explosion hazard.

4. The. addi t ion o f aluminum n i t r a t e t o WM-183 waste t o which i ron has been added has potent ia l f o r keeping the chlor ide i n the calcine.

7, Newby, B.J. "Calcining Sodium-Bearing Waste Using Aluminum Nitrate". Technical Reoort - Westinahouse Nuclear Idaho Comoanv. WfNCO-1026, Idaho Fa1 1 s, Idaho.

Sumnary

I n t h i s repor t methods were studied f o r converting the sodium bearing wastes a t the Idaho Chemical Processing Plant (ICPP) i n t o granular, f ree f lowing so l ids by f l u id i zed bed calcination. Test runs were carr ied out i n a 10 and 30 cm diameter f l u id i zed bed calc iners i n which sodium bearing waste was blended wi th aluminum n i t r a t e and various additives. Aluminum n i t r a t e represents Fluor inal waste, which i s anticipated t o be blended wi th the sodium bearing waste.

One composition o f simulated sodium bearing high leve l waste was used. The major consti tuents o f the simulated waste were Na, A l , B, K, Mn, Fe, NO,, 61, PO,, SO,, and acid. Various addit ives were added t o the waste t o obtain desired ca lc iner operation, f l u id i zed bed character ist ics, propert ies o f calcined sol ids and chlor ide v o l a t i l i t y . The ca lc inat ion feed compositions were blends o f the sodium bearing waste and: (1) aluminum n i t r a t e and bor ic acid, (2) bor ic ac id and magnesium n i t ra te , (3) i r on metal, (4) bor ic acid and sugar, (5) bor ica acid and calcium n i t ra te , (6) phosphoric acid and calcium n i t ra te , (7) calcium n i t ra te , (8) phosphoric acid, (9) hydrof luor ic acid-boric acid-calcium n i t ra te , (10) aluminum powder.

The major f indings o f t h i s study i n re la t i on t o the composition and the addit ives were that:

1. A blend o f sodium bearing waste and 2.2M A1(N03) (2 : l vol.) with 0.10-0.20M bor ic acid added t o the feed i s read i l y calc inat le. Blends wi th 0.20-0.2531 bor ic acid resul ted i n d i f f i c u l t y i n cont ro l l ing p a r t i c l e size. Blends wi th 0.401rz bor ic acid tended form c l inkers i n the bed.

2. Too small o f a nozzle i n the f lu id ized bed w i l l cause frequent

3. Decreasing the 2:l volume r a t i o o f A1(N03), t o sodium bearing waste

plugging o f the nozzle.

with 0.20M bor ic acid resul ted i n frequent nozzle plugging.

I - . 4. The addition of magnesium nitrate to a blend o f Al(NO,), and sodium

bearing waste with 0.20M boric reduced particle size control, increased chloride volatilization, and decreased iota alumina and crystal1 ine sodium aluminate concentrations in the calcined sol ids.

5. A blend o f 2.2M Al(N0 0.52M iron powder is readily caicinable. However, iron addition to the acidic waste results in a vigorous chemical reaction, Caking o f this calcined product occurs in storage vessels over long periods o f time.

and sodium bearing waste (2:l vol.) with

6. Decreasing the volume ratio o f Al(N03)3. and sodium bearing waste with iron additive results in a decrease in particle control. In addition, the same amount o f nitrate that is decomposed by the iron in lower volume ratios i s replaced by the nitric acid needed to stabilize the solution and dissolve the iron powder.

7. Blends o f 2.2M aluminum nitrate and sodium bearing waste (2:l vol.) with 0,20M boric acid and one moTe o f sugar for each 10-20 moles o f nitrate present were calcined without bed agglomeration or product size control problems.

8. Plugging o f the off gas filters when calcining solutions containing sugar may be a problem with certain types o f filters..

9. Blends o f 2.2M aluminum nitrate and sodium waste with 0.24M calcium nitrate resulted in good retention o f chloride in the calcine, but difficult to control particle growth and high nitrate concentration in the calcine. Decreasing or increasing the calcium nitrate concentration substantially resul ted in severe aggl omerat i on.

10. Blends o f 2.2M aluminum nitrate and sodium waste containing 0.20M phosphoric acid is readily calcined. However, difficulty in particle growth control and low retention o f chloride in the calcine solids was observed.

llo Blends o f 2.2M aluminum nitrate and sodium waste with 0.15M phosphoric acid and 0.52M calcium nitrate resulted in doubling the percentage of chloride retained in the calcine solids when only calcium nitrate is added.

12. Blending aluminum powder, nitric acid, and sodium waste produces a violent reaction. destroys in the sodium waste ends up being added by the amount o f nitric acid need to maintain stability o f the solution.

In addition, the amount o f nitrate the aluminum powder

8, Domish, R . P . , and L.P. Hatch, "Continuous Calcination o f High-Level Radioactive Wastes by Rotary Ball Kiln". 1 National Laboratory. BNL-832, Long Island, New York, November, 1963.

Summary

This report studied the feasibility of using a rotary ball kiln in calcination of simulated HLW. A two kiln process was used to reduce corrosion o f the calciner materials. Steel balls were introduced into both kilns to aid in heat transfer and break up the calcine. This study was particularly interested in parameters such as corrosion and best materials to prevent corrosion, dust control , and leaching. However, typical operating parameters were also studied but in lesser detail.

This study only involved one feed composition, In which the main constituents were NO,, Al, Na, C1, and acid. Sodium content was less than 0.036M-

The onJy major finding in relation to the composition was that cake formation was observed when inadequate wall temperatures for decomposition of the salts occurred. Cake formation was not a problem over most of the runs.

9, Bonner, W.F., H.T. Blair, and L.S. Romero. "Spray Solidification of Nuclear Waste" T g . BNWL- 2059, Richland, Washington, August, 1976.

Sununary

This report summarizes the findings of the Waste Fixation Program (WFP) on spray calcination of simulated high level wastes. This study utilized a heated wall spray calciner fitted with top mounted vibrators. The primary purpose of this study was to demonstrate the spray calciners' ability to handle a variety of different waste types and investigate key processing vari ab1 es e

Spray calcination of six different types o f simulated high level waste were investigated in this study, including "clean" HLLW (a G.E. type waste from a plant wherein no chemical salts were added during reprocessing) "dirty" HLLW (an Allied General Nuclear Services (AGNS) type waste, moderately high in salts), AGNS waste (a relatively clean ILLW containing O.1M Fe and PO ), Combined HLLW and ILLW, Nuclear Fuel Services Waste (NFS), and combined NF3 HLLW and NFS sodium waste. The major constituents o f the simulated waste were K, Mo, Fe, CO, N i , rare earth mix, didymium, HNO,, Na, Cr, Ni, and PO,. Si.lica was used as an additive to enhance calcination of high sodium wastes.

The major findings of this study in relation to composition and the additives were that:

1. Encrustations o f calcine regularly form around the nozzle exit, but seemed not to significantly hinder atomization or calcination.

2. Significant abrasion o f the.303 SS nozzle was observed, but mostly corrected by using a 96% alumina nozzle.

3. Wastes containing up to 2.OM sodium maybe calcined, but calcfner capacity must be decreased as more sodium in the wastes is introduced into the feed .

4. Top mounted vibrators cannot effectively remove calcine buildup on the wall when high sodium content wastes are being process at high capacity. However, it is felt that side wall vibrators may overcome this problem.

5. Scal ing on the walls maybe caused by 1) partial me1 ting of the particle on contact with the wall, 2) sufficient particle moisture or acid content to cause stickiness but insufficient to cause desealing as vaporization occurs at the hot wall, 3) sintering.

6. Powdered silica may be added to the feed to promote calcination of high sodium wastes. This run was carried out with simulated feed other than the six primary simulated feeds used in the majority o f the study. This run was not entirely successful since a glaze formed on the inside of the calciner walls.

7. Feed nozzle plugs were common among high sodium feeds.

10. McElroy, J.L., C.R. Cooley, W.V. DeMier, and J.E. Mendel. "Pot Calcination Performance During First Radioactive Tests in Waste Sol idi f i cat i on Engineering Prototypes : Waste Sol idi f i cat i on Program, Volume 4". Technical ReDort - Pacific Northwest Laboratories. BNWL-814, Rich1 and, Washington, December, 1968.

Sumnary

This report presents results and analyses of the first six radioactive demonstration runs with the pot calcination system in waste solidification engineering prototypes (WSEP). Solidification of high level aqueous radioactive wastes containing approximately 4 mill ion curies was successfully completed in the six demonstration runs. The principal variables investigated in these runs were fission product power, pot -size and waste chemical composition.

Two types o f waste (low sulfate, high iron and high sulfate, low iron) were prepared from Hanford Purex Plant acidic waste (Purex 1WW) and I4,Ce-Pr solutions from the Hanford Fission Products Processing Plant, and some inert chemica7s. These two types of waste were named PW-1 and PW-2. Primary constituents of the waste were Na, A l , Fe, Y and rare earths, NO,, SO,, and fission products. Ca, SO,, and Na were added to the feed to either promote calcination, substitute for other constituents, or reduce volatilization of ceratin species .

The major findings of this study in relation to composition and additives were that:

1. Foaming of the PW-1 waste during feeding is a potential problem.

2. The presence o f sulfate tended to decrease foaming.

Foaming did not occur when using PW-2 waste.

3. Solutions high in nitric acid tended to foam more readily.

4 A1 umi num concentrations above 0.5M tended to aggravate the foami ng tendency e

5. High solids content in PW-2 waste caused severe plugging of the equipment.

6, Some scal ing was observed in processing both wastes.

If 0 Bond, W.R., J.N. Hartley, J.E. Mendel, J.L. McElroy, K.3. Schneider and M.R. Schwab. "Waste Solidification Program, Volume 6 - Spray Solidification Performance During First Radioactive Tests in Waste Solidification Engineering Prototypes". Technical Reoort - Pacific Northwest Laboratories. BNWL-1391+ Richland, Washington, August, 1970.

Summary

This report presents results and analyses of the first six radioactive demonstration runs with the spray solidification system in waste solidification engineering prototypes (WSEP) . Solidification of high level aqueous radioactive wastes containing approximately 7.8 mill ion curies was successfully completed in the six demonstration runs. The principal variables investigated in these runs were the heat generation rate in the solidified waste and the two waste types.

The two types o f waste (sulfate free and sulfate containin$ were prepared from Hanford Purex Plant acidic waste (Purex IWW) and Ce-Pr solutions from the Hanford Fission Products Plant, and some inert chemicals. These two types of waste were dubbed PW-1 and PW-2. 'Primary constituents of the waste were Na, A i , Fe, Y and rare earths, N O , SO,, and fission products. Al, Ca, Li, and Na were added to the feed to either promote calcination, substitute for other constituents, or reduce volatilization of ceratin species . additives were that:

The major findings of this study in relation to composition and the

1. Deposition of partially dried calcine on the walls and a t the bottom o f the spray calciner chamber was observed. T h i s problem could be partially corrected by using a different feed nozzle. Long term operation o f the spray ealciner revealed significant calcine buildup on the walls and bottom of the feed calciner. T h i s problem was attributed t o inadequate atomization o f the feed .

2. Plugging of the feed nozzle occurred many times when h igh sal t , high solids content feed (PW-2) was solidified. This problem can be overcome by sufficient periodic washing of the feed nozzle.

3. A wall vibrator can effectively be used t o prevent calcine bui ldup on the walls o f the calciner. However, the wall vibrator was subject t o occasional failure.

12. Kulichenko, V.V., V.F. Save1 'ev, V.A. Prokhodtsev, and A.A. Ryabova. "Calcination o f Model High-Level Wastes i n a Horizontal Apparatus". Soviet A t omic Eneruv. Volume 56, NO. 5, May, 1984, pp. 314-318.

Surmaary

This study describes the use o f a ro ta t i ng horizontal worm conveyor - ca lc iner i n s o l i d i f y i n g ac id ic high leve l radioactive waste. It i s stated

tha t a horizontal p lan t i s much less sensi t ive t o the waste composition than i s a f l u id i zed bed or sprayer. However, the design o f a horizontal p lant i s more compl icated due t o moving mechanisms i n the worm conveyor and the low surface area i n which t o t ransfer heat. The calc inator i s 27 cm i n diameter and 3.6 M long.

molasses were sol i d i f i e d in. the calciner. Some runs contained ?e(N03)3, Cr(NO,),, Mn(N03)2, and N i (NOJ2. Molasses was added t o accelerate decomposition o f the n i t ra tes.

Various compositions consist ing o f p r imar i l y A1 (NO),, NablO , and

The major f indings o f the study i n re la t i on t o composition and the addit ives was that:

1. The horizontal calc iner could s o l i d i f y high aluminum and sodium However, very high sodium wastes were wastes wi th and without additives.

observed t o s t i c k t o the wal ls o f the tube,

2, Up t o 260 g/l o f sodium n i t r a t e could be calcined i n the worm

N i t ra te content i n the calc inate was d i r e c t l y re la ted t o the amount

conveyor w i th the molasses additive.

o f molasses added t o the feed, 3 .

I 13. Cameron, W.A. and S. Merlin. "An Evaluation o f the AVM Process and i t s Appl i cabi 1 i t y t o West Val 1 ey" . Jech n ica l RePort - SGN/NumateC. pp. 542- 546. I

Sumnary I This repor t describes the operating experience o f the AVM v i t r i f i c a t i o n

p lant i n France f o r the l a s t three years. A comparison o f the AVM and West Valley wastes i s made and the app l i cab i l i t y o f the AVM technology t o the West Val ley high leve l waste i s p a r t i a l l y assessed.

The AVM p lant has been i n hot operation f o r the past three years, processing a wide range o f compositions. AVM high leve l waste i s ac id ic and pr imar i l y contains A I , Na, Mg, Fe, N i , C r , F. P, Gd, actinides, and f i ss ion

products. problems that have occurred during hot operation have been:

Sodium levels in the feed range .from 1' to 23 g/1. The major

1. Contamination o f a work area due to both a failure of the automatic feed valve supplying glass frit to the rotary kiln, and excess pressure in the cal ci ner .

2. Contamination o f the calciner lubrication oil recuperation circuit.

3. Replacement o f the two parts o f the dust scrubber for corrosion problems. Fluorine contained in the feed is to blame.

4, Replacement o f the driving motor o f the calciner tube.

Comparing the AVM waste with WVOP waste, the primary differences are that the WVDP waste i s neutralized and contains a very high sodium content. It is stated that the a clear advantage of adopting the AVM process at the WVDP is the availability of significant data accumulated during hot operation.

. . ,

14. Hull, H.T. "Trip Report on Rotary Kiln Test at Envirotech in Salt Lake City". J#. DPST-81-270, Savannah River, Georgia, January 8-9, 1981.

Sunmary

This trip report details the findings of a DWPF rotary kiln test at Envirotech in Salt Lake City, Utah. This .study investigated the feasibility o f using a rotary calciner to calcine simulated Savannah River alkaline high level waste. A 6.5 inch diameter three foot long rotary calciner was used to perform the experiments. A steel bar was inserted inside the calciner to break up the calcine.

Two alkaline solutions were prepared to simulate DWPF alkaline waste sludge. The first solution contained 19 ut% solids and 81 ut% water and the second contained 40 wt% solids and 60 wt% water. However, the solids in the second solution contained 35 wtX simulated sludge and 65 wt% Frit 211 (80 mesh). Common to both solutions was the composition of the waste sludge, which included Fe(OH),, A1 (OH),, MnO,, Ca(OH),, NaNO,, and Na,SO,. Azodicarbonamide was added to the feed to prevent decomposition outside o f the kiln.

The major findings of the study in relation to the composition and additives was that:

1. First feed solution calcined easily to a free flowing granular product. No scaling was observed on the inside of the kiln.

2. Second feed was uncalcinable due to frit melting in the kiln. A sticky bed and abundant scaling were observed.

15, Freeby, W.A. "Interim Report - Fluidized Bed Calcination of Simulated High-Level Commercial Wastes". Technical ReDort - Idaho National Enuineerinu Lab0 raitorv . ICP-1075, Idaho Falls, Idaho, June, 1975.

Sumnary

The purpose of this study was to develop and verify process flowsheets for converting All ied-General Nuclear Services (AGNS) and Nuclear Fuel Services (NFS) aqueous wastes to granular solids using the fluidized bed calcination prgcess. Tests were made using a four and twelve inch diameter cal ci ner e

Four different simulated compositions were studied, including a combined high level and intermediate level AGNS waste, concentrated AGNS waste containing specified concentrations of sodium, dilute AGNS waste containing minimal amounts of sodium, and NFS high level acid waste. The major constituents in the waste were Na, Fe, Al, Cr, Ni, NO,, K, Mo, Co, Cd, Te, Ba, Gd, PO,, and a rare earth mix. Iron powder was added to promote calcination and/or modify the properties of the calcined waste. The major findings of this study in relation to the composition and the additives were that:

1. Concentrated AGNS HLLW can be successfully solidified using fluid be calcination without additives, if the sodium concentration is below 0.20M feed nozzle plugging and moisture in the calcined product occurs with wastes containing more than 0.20M sodium and no additives.

2. Concentrated AGNS HLLW containing up to 1.1M sodium can be successfully solidified using fluid bed calcination, if iron is added to the waste to suppress sodium nitrate formation.

3. Dilute AGNS HLLW.can not be calcined successfully by conventional fluid bed methods since be particle size and bed inventory cannot be controlled in the desired operating range.

is feasible. 4. Fluid be calcination of combined AGNS HLLW-ILLW and NFS acid waste

5, NFS waste containing 1M sodium and no additives has a tendency to agglomerate .

16. A'Iford, M.D. "Fluidized Bed Calcination o f Simulated Purex High-Act iv i ty Level Wastes - In ter im Report". Technical ReDort - General E lec t r i c Hanford Laboratories. HW-66384, Rich1 and, Washington, September, 1960.

Sunmary

The Hanford e ight inch square f l u i d bed waste ca lc iner was operated f o r s i x months i n t h i s report, processing simulated Purex-type ac id ic waste. This report was aimed a t def in ing and improving major operational problems and qua l i t a t i ve l y def in ing the e f fec t o f various operating variables.

represent a low-acid, high s a l t waste from the formaldehyde-kill process, high sulfate, high iron waste, and two var iat ions on the Purex f i r s t cycle waste. The primary consti tuents i n fhe simulated waste were Nay Fe, Al., C r , N i , SO,, PO,, and NO,.

The major f indings o f the study re la t i ng t o composition were that:

Four feed compositions were tested, including compositions tha t

1. High sodium and high su l fa te wastes have a tendency t o fuse i n the bed, deter iously a f fec t ing the f l u i d bed operab i l i t y by scal ing o f the heat t ransfer surfaces above 6OOOC. Thus, feeds o f t h i s type must be calcined bel ow 6OOOC.

2. The most serious problem encountered i n f l u i d bed ca lc in ing o f Purex wastes was tha t o f sol'ids build-up and p a r t i c l e agglomeration a t and/or near the feed nozzle. Modif icat ion o f the nozzle was necessary, but d i d not y i e l d optimum resul ts. High su l fa te wastes severely agglomerated a t the nozzle.

3. Inadequate f l u i d i z a t i o n resul ts when a s u f f i c i e n t l y la rge number of agglomerates co l l ec t i n the bed (> 5 wt%) e

17. Allemann, R.T., and B.M. Johnson. "Radiant-Heat Spray Calcination Process f o r the Sol id Fixat ion Waste". Technical ReDort - General E lec t r i c Hanford L a borat o r ies. HW-65806 P t 1, Richland, Washington, February, 1961.

Sumnary

The spray ca lc inat ion o f simulated wastes has .been studied. i n a r e l a t i v e l y small scale reactor eight inches i n diameter and ten f e e t t a l l . A wide var ie ty o f compositions were handled, including Oarex, Z i r f l ex , TBP-25 and acidic and basic Purex wastes. Many process variables were studied, including feed composition, additives, thermal conduct iv i t ies , atomization , feed rate, reactor temperature, vo la t i l i za t ion , etc..

O f pa r t i cu la r in te res t i s the app l i cab i l i t y o f spray ca lc inat ion fo r high-level wastes containing sodium, such as the Purex wastes. Six dif ferent

L

compositions of simulated acidic and 'basic Purex waste were studied. Principle species present i n most of the simulated Purex wastes were Na, Fe, AI, Nt, Cr, NO,, and SO,. Several additives were used t o promote calcination and/or modify the properties of the calcined waste. The additives used were sugar, phosphate, boric acid, combinations of sugar and phosphate? combination of sugar and boric acid, and calcium.

The major findings of the study relating t o composition and the additives were that:

1. Feed high i n Na, NO,, SO,, particularly basic feeds, were nat cal ci nab1 e w i t h o u t add i t i ves .

2. Incompletely calcined powders, notably the product from high-sul fate Purex wastes, were difficult t o handle because of their tendency t o cake i n the f i l t e r system and cyclone. Th i s difficulty occurred principally w i t h the acidic waste and t o a lesser extent the neutralized waste. Build-up of calcine on the walls o f the cal