Session and Paper Number: . - 6 C -

Aerosol Reduction from Episodic Releases of Anhydrous Hydrofluoric

Acid by Modifying tlr.. Acid Catalyst with L i q u i d Oniurn

Po ly ( ~ ~ d r o g e ~ Fluorides)

Kenneth R. Comey 111, Lee K. Gilmer, and George P. PartxidgeS

Texaco R&D, Port Arthur, Texas 77640

David W. Johnson Quest Consultants, Norman, OK 73070

Prepared for presentation at

AIChE 1993 Summer National Meeting Mitigation of Hazardous Chemical Releases (11):

Design Changes

Copyright 1993 Texaco Zncorporated

UNWBLISHED

A X C ~ E s h a l l not be responsible far statenents or opiniona in papers or printed in its publications.

'currently with Penn State University, Middletown, PA 17057

The safe handling and storage of anhydrous hydrofluoric

acid (HF) in refinery alkylation units is an important

concern in the refining industry. Releases of HF could

result in the formation of an aerosol jet. Current

mitigation methods for HF releases involve the use of

active systems such as barriers or water sprays. These

systems, used after a leak has occurred, attempt tc

contain the released material or scrub the material from

the air stream. In this paper, a passive technology is

discussed. This technology minimizes the formation of an

aerosol by modifying the circulating hydrofluoric acid

with the use of liquid onium poly (hydrogen fluoride)

complexes. A small scale apparatus designed and built at

the Texaco Research Laboratory in Port Arthur, Texas was

used to investigate the aerosol reduction capability of

several complexing materials. Based on the small-scale

results, large scale tests were performed at Quest

Consultants' outdoor test facility in Oklahoma. This

paper presents results quantifying the liquid rainout at

several release conditions along with a comparison of

small versus large scale releases.

INTRODUCTION

Anhydrous hydrofluoric acid (HF) is used in the

petroleum refining industry as a catalyst for the

production of high octane gasoline by the isobutane-

isobutylene alkylation reaction. Accidental releases of

pressurized, superheated, anhydrous hydrofluoric acid

predominantly produce an aerosol. The aerosol cloud

formed may contain concentrations above acceptable

exposure criteria. Accidental releases of HF at several

refineries have resulted in increasing political pressure

to replace existing HF alkylation units with sulfuric

acid alkylation units. The estimated cost of converting

a single HF alkylation unit to sulfuric acid ranges from

10 to more than 100 million dollars, depending upon the

unit capacity.

BACKGROUND

Previous hydrofluoric acid testing concentrated on

examining the basic phenomena contr.olling a flashing

release of anhydrous HF and hydrocarbons, or the

mitigation of an HF release using water spray systems.

Two large-scale outdoor test series have been conducted,

the Goldfish ~rries and the Hawk series. Smaller,

laboratory scale testing has been conducted to as- .ss the

effectiveness of passive mitigation measures such as the

use of additives complexed with HF.

1986 Goldfish HF Test Series

During the summer of 1986, Amoco Oil Company and

Lawrence Livermore National Laboratory conducted a series

of six experiments involving large-scale atmospheric

releases of anhydrous hydrofluoric acid. This series of

atmospheric dispersion experiments is known as the

Goldfish Test ~eries~,~,~'~. These experiments were

conducted at the Department of Energy Liquefied Gaseous

*~lewitt, D. N., J. F. Yohn, R. P. Koopman, and T. C. Brown, "Conduct of Anhydrous Hydrofluoric Acid Spill Experiments,lV International CoriSerence of Vapor Cloud Modeling, CCPS/USEPA, New York, pp. 1-38 (1987).

3~lewitt, D. N., J. F. Yohn, and D. L. Ermak, "An Evaluation of SLAB and DEGADIS Heavy Gas Dispersion Model Using the HF Spill Test Data," AIChE International Conference on Vapor Cloud Modeiing, Boston, MA (1987).

'Chan, S. T., H. C. Rodean, and D. N. Blewitt, IvFEM3 Modeling of Ammonia and Hydrofluoric Acid Dispersion," AIChE International Conference on Vapor Cloud Modeling, Boston, MA (1987).

'~lewitt, D. N., J. F. Yohn, R. P. Koopman, and T. C. Brown, "Conduct of Anhydrous Hydrofluoric Acid Spill Experiments," AIChE International Conference on Vapor Cloud Modeling, Boston, MA (1987).

Fuels Facility located on the Nevada Test Site at

Frenchman's Flats.

The tests were conducted because considerable

uncertainty existed as to the amount of material that

might become airborne after a release of superheated HF.

This uncertainty made the accurate calculation of hazard

zones resulting from a release of superheated HF

difficult. Thus, the purpose of the Goldfish Test Series

was threefold.

(1) Obtain basic information regarding the source

characteristics during an atmospheric release of HF

stored at an elevated pressure and temperature.

(2) Provide downwind measurements of HF concentrations

in both the dense gas and trace gas regions against

which the performance of dense gas dispersion

models could be tested.

(3) Provide information regarding the effectiveness of

water spray systems in reducing the downwind

concentrations of HF.

The Goldfish tests demonstrated that flashing

occured for accidental releases of HF at alkylation unit

temperatures and pressures (above the boiling point) . No liquid dropout of HF was observed. All of the released

material became pirborne as an aerosol-vapor cloud. The

resulting HF cloud was cold and much denser than ambient

air. The entire release remained cold, dense, and

compact as it initially moved downwind. At about 700 to

1000 meters downwind HF cloud breakup was seen to occur.

The last three tests in the Goldfish Test Series

were devoted to the evaluation of several water spray

configurations. Water sprays were found to be effective,

but the complications and uncertainties of large-scale

testing in the open atmosphere did not allow good

quantitative information to be obtained. Thus, a need

existed for quantitative information on water spray

effectiveness as a function of such parameters as

water/acid ratio, water droplet size, and water spray

configuration. This led to further tests called the Hawk

Tnst Series.

1988 L a b o r a t o r y and Hawk HF T e s t series'

In 1987, the participants in the 1986 Goldfish HF

Test Series formed the Industry Cooperative HF Miti-

gation/Assessment Program (ICHMAP). By 1988 this program

was supported by 20 major petroleum and chemical

companies, including Texaco. The program addressed three

areas: water sprays, vapor barriers, and ambient impact

assessment.

The objective of the water spray study was to

investigate the effectiveness of water sprays in

mitigating HF releases as a function of flow conditions,

acid and spray properties, and geometric factors. The

water spray study was divided into laboratory and field

studies. The laboratory studies involved 42 tests of HF

releases on a small scale to help define the test matrix

for the larger field testing, to evaluate design criteria

for the larger flow chamber, and to gain operating

experience for the larger unit.

6Schatz, K. W. and R. P. Koopman, "Effectiveness of Water Spray Mitigation Systems for Accidental Releases of Hydrogen FluorideI1' Summary Report and Volumes I-XI NTIS, Springfield, Virginia (1989).

During August and September of 1988, 87 field tests

were carried out in a newly designed flow chamber erected

on the Nevada Test Site at Frenchman's Flats. Over 20

different combinations of operating conditions and

geometric variables were tested.

1990 Laboratory T e s t s

Although the Hawk Test Series showed that water

sprays can be highly effective in mitigating an

accidental HF release, any delay in activating the water

spray system could allow an unmitigated HF cloud to

escape the immediate release area. In late 1989, Texaco

initiated research involving passive means of mitigation

through the use of additives. The objective of using

additives was to alter physical properties including the

vapor pressure and thereby reduce the aerosol forming

tendencies of the HF/additive mixture, while still

maintaining catalytic activity for the alkylation

reaction.

In early 1990, Texaco and Mobil jointly carried out

laboratory experiments to evaluate the aerosol forming

tendencies of mixtures of HF with ,I7 different chemicals.

Results from these tests were sufficiently encouraging to

pursue further research and obtain kinetic information

regarding the effects of chemical additives.

Olah's Patent

In 1991, George A. Olah, Director of the Loker

Hydrocarbon Research Institute at the University of

Southern California, was issued a patent' titled

"Environmentally Safe Catalytic Alkylation Using Liquid

Onium Poly(Hydrogen Fluorides)." This invention

describes a process for alkylating an aliphatic

hydrocarbon with an alkyl hydrocarbon in the presence of

a liquid onium polyhydrogen fluoride complex as the

reaction medium. Some examples of polyhydrogen fluoride

complexes include those of ammonia, methylamines,

ethyamimes , propylamfnes , butylamines , pyridine , and

picolines. The concentration of the amine components of

the hydrofluoric acid complex is between 5 and 30 wt%.

'olah, George A, "Environmentally Safe Catalytic Alkylation Using Liquid Onium Poly(Hydrogen Fluorides)", US Patent Number 5,073,674.

The hydrofluoric acid complex reduces the tendency

of an HF/additive release to form an aerosol by two

mechanisms. First, the Olah patent illustrates the

concept that a reaction is occurring between the

hydrofluoric acid and the additive to form a polyhydrogen

fluoride complex. The polyhydrogen fluoride complex

contains a long chain consisting of strongly associated

HF molecules. This reduces the tendency of the HF

molecules to form an aerosol upon a superheated,

pressurized release. Second, the physical vapor pressure

of the polyhydrogen fluoride complex is lower than that

of anhydrous HF.

1991 Laboratory T e s t s

Texaco constructed test facilities at its Port

Arthur Laboratory to release small quantities of HF in

order to quantify the aerosol reduction capabilities of

candidate additives. A simplified flow diagram is shown

in Figure 1. The screening chamber consists of a

rectangular chamber constructed of Lexan. The chamber is

designed for a horizontal release with provisions for

nitrogen injection co-currently with the release stream.

The nitrogen injection provides additional air

CHAMBER

I SCRUBBERS I

ADDITIVE STORAGE VESSEL

HF STOR&GE HF N2 NITROGEN

- - ELECTRIC HEATER

30D nl REACTOR

Figure 1

Simplified Schematic of Screening Cha&er

entrainment and allows for purging of the chamber prior

to conducting a release. The dimensions of the chamber

are 91.4 cm (36 inches) by 30.5 cm (12 inches) by 24.6 cm

(9.7 inches) . An exhaust line from the chamber is

attached to the bubbler system to scrub any HF vapors

before they are released to the atm~sphere.

The results of the HF/additive releases are reported

as the amount of HF reduction according to the following

equation:

where R = HF aerosol reduction; wt%

V = mass of airborne HF; grams

L = total mass of release; grams

A summary of the results from the screening chamber

is found in Table I. The baseline experiment is an

anhydrous HF release at 45°C (113 OF) and 690 kPa (100

psig) . There is an average of 0.9 wt% HF recovery. This

corresponds to similar results obtained in the HF Hawk

Test Series. However, these experiments are not meant to

simulate field-scale releases; but, to measure relative

-12-

differences between the effectiveness of different

additives. Many other factors are not accounted for with

these laboratory tests including wind velocit.~, amount of

air entrainment, humidity, time of flight, release

geometry, release orifice size, and ambient temperature.

Although many additives were tested, results are

only reported an one of the best additives. A s shown in

the table, greater than 80 wt% HF reduction can be

accomplished with relatively small concentrations oE

additive.

TABLE I

SUMMARY OF HF REDUCTION - SCREENING CHAMBER

OVERVIEW OF HFIADDITIVE TE-

In the spring of 1992, Mobil Research and

Development Corporation designed a flow chamber at the

Quest Consultants test site in ~klahoma" The chamber is

designed to study the effect of several variables on the

liquid rainout or pooling of HF/additive complexes and

anhydrous HF releases. A simplified flow diagram is

presented in Figure 2.

The following information can be obtained with the

Quest Chamber: the effect of orifice size, release

temperature, release pressure, and additive concentration

on percent HF recovery. With some minor modifications,

pool evaporation rates and emulsified HF/hydrocarbon

mixtures can be investigated.

The flow chamber is designed with a high degree of

turbulence, similar to the turbulence found at an

-industria-1 - 1 d i a n . Fans at the end of the chamber

provides an average air velocity of about 5 mph inside

'schatz, K. W., G. R. Jersey, and M. K. Chalam, **Apparatus for Field Testing of HF release^,^^ AIChE Summer National Meeting, 1993.

FRESH A D D I T I V E

RECYCLE A D D I T I V E

C RELEASE VESSEL

r

ADDITIVE CQUH

ANHYDROUS HF

VATEQ SPRAYS

ORIFICE PLATE

COLLECTION VESSEL

Figure 2

Simplified Schematic of Quest Chamber

the chamber. Temperature controlled liquid for each test

is released from a pressurized vessel through an orifice

into the chamber. The release vessel is supported by

load cells so that the release rate can be quantified.

Eight collection pans are placed side by side inside the

flow chamber. The liquid collected in the pans is

drained into a collection tank mounted on load cells.

The weights of the release vessel and capture tank are

monitored and recorded during each test. Most of the

airborne material not collected in the capture pans is

removed in a two-stage water spray system. Each water

spray stage has a collection sump and spray pump for

recirculation of the water to a spray header. The water

spray system is located directly downstream of the

capture pans. HF detectors are located downwind fromthe

flow chamber to monitor the concentration of unmitigated

fumes .

The testing permit allowes a maxirtum HF release rate

of 11.3 kg/minute (25 pounds/min) into the atmosphere.

Release conditions are controlled so that this release

rate is never exceeded. In most tests, emissions are

below 1 kg/minute (2 pounds/min) .

For each test, a material balance is calculated for

each of the liquid components: NF, additive, and water.

Analyses of the collected liquid rainout permit

quantification of the disproportionate loss of HF and

gain of water from the liquid released. Sump levels and

sump water analyses provides a nearly complete cl~sure of

the material balance, with only minor quantities escaping

to the atmosphere.

Local wind conditions deternine the frequency of

test runs to ensure safe operating conditions relative to

surrounding areas. Adherence to safe execution of oper-

ations, proper use of safety equipment, and safe handling

of materials at the test site is insured by the use of

contract safety professionals.

DESCRIPTION OF TEST EOUIPMENT

The test equipment is designed to study the effect

of several variables on the liquid rainout or pooling of

HF/additive mixtures and anhydrous HF releases. A flow

chamber was constructed to mitigate the effects of local

weather conditions and to provide containment for the

airborne HF until it could be scrubbed from the air. The

chamber houses the liquid capture equipment and the water

spray system. The major processing areas at the site

include : flow chamber; HF storage, transfer, and

conditioning; liquid capture and weighing; HF spray

system; waste disposal; control and data acquisition; and

chemical laboratory.

Flow Chamber

The chamber is constructed of 1/2-inch prefabricated

resin-coated plywood panels and built on a leveled C-

channel steel footing . Each of the panels, 2 . 4 m (8 it. )

by 4.9 m (16 ft.) high, has an exterior framework of 2

x 6 inch wooden studs and a 0.6 m (2 ft. ) by 1.2 m ( 4

ft.) plexiglass window. The windows are covered on the

inside with a 1-mil layer of Halar, an HF resistant,

transparent fluorocarbon.

Inside the chamber, eight collection pans, each 3.0

m (10 ft.) by 4.6 m (15 ft.), are set up side by side to

cover a downwind length of 2 4 . 4 m (80 feet). The pans

extend from one side of the chamber to the other side

with approximately 1/2-inch of space on each side. Each

pan has a sloping bottom with a 3/4-inch drain line.

Each drain line has a sample valve so that the contents

of the pan can be individually sampled, if required. The

pans are loosely lined with a 4-mil polyethylene liner

secured around each drain line with roofing mastic. The

liner minimizes HF contact with the steel pan surfaces.

The two water sprays, located sequentially near the

end of the pans, remove airborne HF from the chamber air

stream. A polypropylene demister between the last spray

and the chamber fans minimizes the loss of acidic water

to the atmosphere. The water system over-sprays

slightly into the last pan. This pan is drained through

a 3-inch PVC line directly into the first collection

sump. The collection sumps are dug below grade and are

approximately 2.4 m (8 ft.) wide, 5.2 m (17 ft.) long,

and 1.5 m (5 ft. ) deep. The inside of the sumps is

coated with two-component epoxy resin.

At the front of the chamber, a square edge,

rectangular opening is used to admit air to the chamber.

Smoke tests during commissioning of the chamber showed

that this design resulted in high turbulence inside the

chamber. This turbulence correlates to turbulence levels

typically found around a commercial alkylation unit.

Air flow into the chamber is induced by two 1.2 m

(48-inch), 1079 scmm (38,100 scfm) axial fans mounted at

the rear of the chamber. Chutes, with 45" angled bottom

plates, direct the outflowing air in an upward direction.

This helps to rapidly disperse any HF emissions during

testing.

HF Storage, Transfer, and Conditioning

Anhydrous HF is delivered in one ton cylinders

containing 590 kg (1,300 pounds) of HF. Four cylinders

are connected through a common manifold. The cylinders

charge HF through a 1/2-inch flexible, teflon lined,

metal hose into the transfer pipe manifold.

The transfer of HF fror~ a cylinder to the release

tank is accomplished by pressurizing the cylinder to

approximately 483 kPa (70 psig) with nitrogen and

discharging the pressurized liquid HF through the

manifold and piping. After transfer of HF, the manifold

and transfer piping is purged with nitrogen. The weight

of material in the release tank is measured using 3 load

cells that support the entire vessel weight with a

capacity is 3,400 kg (7,500 pounds).

Once charged to the release tank, the HF or

HF/additive mixture is circulated by a pump through a

heat exchanger with a heat transfer area of 9.6 m2 (103

ft2). Refrigeration is provided by a 35,160 W (120,000

Btu/hour) glycol/water chiller unit. Heat is supplied by

a commercial 27,015 W (92,200 Btu/hour) electric water

heater.

Liquid Capture and Weighing Area

The liquid collected in the flow chamber capture

pans is gravity drained to a 3785 liter (1000 gallon)

tank. The drain lines from each capture pan are

constructed of 3/4-inch PVC piping. The drain lines are

connected into a 1 1/2-inch manifold attached to the

capture tank. The capture tank is located in a 61 cm

(24-inch) deep concrete pit. This allows an adequate

slope on the drain lines to the tank and simultaneously

provides a sump for the tank contents. The tank is

mounted on 4 load cells with a combined capacity of 7,257

kg (16,000 pounds).

During collection, the capture tank is vented to the

inside of the flow chamber through a 2-inch vent line.

The tank is equipped with a thermocouple, a differential

pressure transmitter, and a pressure indicator. The tank

contents are sampled at a port on the tank discharge

piping. Piping is provided to route the tank contents to

either the neutralization tank, the recycle tank, or back

to the capture pans.

HF Spray System and F i r e Water

A water spray system is used to remove HF from the

air flowing in the chamber. This allows HF/additive

releases greater than 11.3 kg/minute (25 lb/minute) to be

made while remaining within the permitted release rate of

KF to the ambient atmosphere. The water spray system

consists of two separate water sprays installed

sequentially at the end of the flow chamber. The sprays

are constructed of 4-inch schedule 80 PVC piping with

eight spray nozzles in a horizontal run across the

ceiling of the flow chamber. The nozzles are mounted

directly into drilled and tapped holes in the PVC pipe.

Nozzles in the spray nearest the end of the capture

system (north end) point straight down, while the headers

of the other spray (nearest chamber entrance) are turned

450 upwind to reduce water loss past the edges of the

sump.

Two pumps with a nominal capacity of 1,893 lpm (500

gpm) at 690 kPa (100 psig) discharge are used to

recirculate spray water from the individual sumps through

the spray headers. The discharge lines from the pumps

contained valving tq allow the acid water to be pumped to

the neutralization ta.nk, to the spray headers, or between

sumps. Acidic water in the sumps can be pumped to the

neutralization tank. The transfer from sump to

neutralization tank is made when the HF concentration in

the sump increases 2-5 weight percent.

Mater monitors are used as standby prokection in

case of an accidental HF release or fire. A fire water

system, constructed of 4-inch steel pipe, extends from

the firewater tank along the east side -of the chamber and

then along the north side of the chamber. The fire water

pressure is supplied by a 1,893 lpm (500 gpmj, 590 kPa

(100 psig) water pump. One and one half inch brass ball

valves are placed at several locations along the fire

main to supply water for fire hoses and portable

monitors. Two portable monitors, located near the front

of the flow chamber, each of 946 lpm (250 gpm) capacity

are always connected to the fire water system. During

any transfer operation involving HF or during a test, the

fire water system is always operational and at pressure.

Waste Disposal

Waste products are neutralized and treated in a

46,940 liter (12,400 gallon) tank lined with two layars

of 20-mil high density polyethylene. Before waste

products are added to the tank, the tank is partially

filled with a caustic solution. Prior to the addition of

any waste product containing HF, the tank is filled with

13,250 liters (3,500 gallons) of water and caustic

solution. During any addition of acid to the tank, the

pH of the solution is monitored and caustic added as

required to maintain a pH of 11-13. Maintenance of the

relatively high pH insures that all HF is bound by the

neutralization process.

Waste products are added to the neutralization tank

until the liquid level is within one foot of the top.

For binding the fluoride ions, calcium chloride is added,

which causes precipitation of calcium fluoride. The

precipitate is allowed to settle for sever 1 days and the

supernatant liquor is pumped off and taken to a licensed

disposal site. The remaining sludge is mixed with

concrete, pumped into dumpsters, and allowed to form a

solid. The solid waste is taken to a non-hazardous waste

landfill for disposal.

At the end of the test series, the equipment is

decontaminated by first purging with nitrogen, washing

twice with a solution of sodium bicarbonate, and followed

by a final water rinse. All liquid generated by the

decontamination is collected and neutralized as described

above.

Control and Data Acquisition

The equipment used to control fluid storage

conditions, videotape each test, and record data from

each test is housed in a portable trailer. The data

acquisition system receives 4-20 ma or 0-5 volt dc

signals from the process instrumentation. The 4-20 ma

signals are converted to 1-5 volt signals using 250 ohm

precision resistors located near the data acquisition

multiplexerr.

Chemical Laboratory

A chemical laboratory is on-site to allow for rapid

analyses of the test and neutralization samples. The lab

is fully equipped with all equipment necessary to analyze

forhydrofluoric acid concentration, water concentration,

and- additive coneent~ation. The -1-ab -is air - conditioned,

equipped with a safety hood, and has running water.

The results for ten of the HF releases at the Quest

Test site are presented in Table 11. The first

experiment (No. 1) was a baseline test case of anhydrous

HF released at representative alkylation conditions

(approximately 32°C and 590 kPa). At these storage

conditions, only 2.1 w t % of the HF released was captured

(fell to the capture pans) . This result is consistent

with the results from the laboratory chamber and results

previously reported in the literature.

The next eight experiments (Nos. 2 through 9) were

HF/additive releases at various temperatures, pressures,

orifice diameters, and additive concentrations. The

amount of HF reduction ranged from 64 to 87 wt%. The

general trend observed is that HF reduction increased

with lower releasetemperatures, lower release pressures,

larger orifice diameters, and higher additive

concentrations. A larger test matrix of these parameters

needs to be completed to fully understand the interaction

of all these parameters. This testing is scheduled for

the Summer of 1993.

There was some concern that the metal collection

pans provided a heat source for re-evaporation of the

liquid rainout. Theref ore, the next experiment (No. 10)

was a release of HF and additive at typical alkylation

conditions with a known quantity of water in each of the

collection pans. The vapor pressure suppression of

aqueous HF should offset the heat pickup from the

collection pans. Each pan was drained individually with

a representative sample taken and analyzed. A

substantial increase in HF aerosol reduction was observed

(greater than 10%). Due to time limitations during the

1992 test series, only one experiment was completed with

water in the pans. Additional experiments are planned

for 1993 to verify this phenomenon.

TABLE I1

BUMMARY OF BF REDUCTION - QUEST CIIAMBER

TABLE PI (CONTINUED)

SUMMARY OF HF REDUCTION - QUEST CKAMBER

ORIFICE DIAMETER, IM.

HF REDUCTION, WT8

The liquid rainout was collected and analyzed for

additive concentration. The analyses of the liquid

rainout indicated that essentially all of the additive

released went into the liquid phase. The remaining

aerosol was essentially anhydrous HF. Therefore, all

water mitigation spray design methodologies and

dispersion modeling procedures applicableto anhydrous HF

are also applicable to HF/additive systems. Figure 3

also shows the calculated combined effect of HF/additive

technology and perimeter water spray mitigation systems.

Assuming a well designed water mitigation system with an

efficiency of 90%, total HF reduction percentages are

greater than 98%.

A comparison of the results from the laboratory

screening chamber and Quest chamber is presented in

Figure 3. Although the releases from the two chambers

are at different release temperatures and orifice

diameters, there is only a slight decrease in HF aerosol

reduction going to the larger chamber.

ALKYLATION RESULTB

UOP conducted pilot plant experiments using the

HF/additive technology which indicated no degradation in

alkylate quality. A plant trial using the HF/additive

was successful in confirming unit operability with the

target additive concentration in the circulating acid.

ADDITIVE CONCENTRATION (MOL PERCENT)

Figure 3

Summary of HF/Additive Aerosol Reduction

The trial resulted in no degradation of alkylate quality.

A demonstration run is scheduled for 1994 at a Texaco

refinery after installation of facilities to recover and

recycle the additive.

The results from Table I1 and Figure 3 clearly show

that the complexed HF polyhydrogen fluoride catalyst

substantially reduces the quantity of HF aerosol

transported downwind should an accidental release occur.

HF reductions greater than 80 wt% are observed at

additive concentrations resulting in no degradation in

alkylate quality. With the combination of the additive

technology and a well designed perimeter water mitigation

system with 90 wt% efficiency, the total amount of HF

reduction can be greater than 98 wt%.

Work is continuing to expand the test matrix

parameters during 1993. Also, a first principles theory

mathematical model is being developed to predict HF

reduction for any HF/additive system.

Data analyses on the results obtained in this study

were based on a single system geometry. Scale-up or

application of this data to other site-specific system

configurations must be done cautiously with good

engineering judgement.

REFERENCES

Blewitt, D. N., J. F. Yohn, and D. L. Ermak, "An Evaluation of SLAB and DEGADIS Heavy Gas Dispersion Model Using the HF Spill Test Data," AIChE International Conference on Vapor Cloud Modeling, Boston, MA (1987).

Blewitt, D. N., J. F. Yohn, R. P. Koopman, and T. C. Brown, "Conduct of Anhydrous Hydrofluoric Acid Spill Experiments," International Conference of Vapor Cloud Modeling, CCPS/USEPA, New York, pp. 1-38 (1987).

Chan, S. T., H. C. Rodean, and D. N. Blewitt, "FEM3 Modeling of mania and Hydrofluoric Acid Dispersion," AIChE International Conference on Vapor Cloud Modeling, Boston, MA (1987).

Olah, George A, "Environmentally Safe Catalytic Alkylation Using Liquid Onium Poly(Hydrogen Fluorides)~', US Patent Number 5,073,674.

Schatz, K. W. and R. P. Koopman, "Effectiveness of Water Spray Mitigation Systems for Accidental Releases of Hydrogen Fluoride, Summary Report and Volumes I-XI NTIS, Springfield, Virginia (1989).