01 Solid fuels (preparation)

97102581 Microscopic observation of coal demineraliration by Ca(OH), leaching Wanga, J. et 01. Fuel, 1997. 16, (5), 369-374. An investigation into coal demineralization by Ca(OH)? leaching followed by dilute HCI washing. Reflected light microscopy and scanning electron microscopy with energy-dispersive X-ray analysis were used primarily. A Hunter Valley coal was examined both in untampered form and after demineralization with varying levels of residual ash. The major minerals in the original coal are quartz and clay, but as the degree of Ca(OH)2 leaching increased, levels decreased. Some clay was fairly readily removed by demineralization; other clay and quartz, in general, appeared to be less reactive. Extensive leaching led to the removal of as much as 90% of the inorganic matter and few mineral inclusions were observable in the treated coal.

97102582 Microwave desulfurization of coal Zhao. Q. et 01. Meitm Zhumhua, 1996, 19, (3). 9-13. (In Chinese) The paper studies the microwave desulfurization of coal. Topics discussed include: (I) di-electrical property vs microwave desulfurization; (2) combined desulfurization by microwave irradiation and acid washing; and (3) role of microwave irradiation in coal desulfurization with fused caustic alkali.

97102583 Mild pyrolysis of coal in a dual Auger reactor (desulfurization) Lin. L. Diss. Ahstr-. Int.. B, 1997, 57, (IO). I36 pp.

97102584 The mulled coal process. An advanced fine coal preparation technology used to improve the handling character- istics of fine wet coal products Jamison. P. R. Proc. Annu. ItIt. Pittsburgh Coal Conf., 1996, 13, (2). 8hO- 865. The mulled coal process for improving the handling characteristics of fine wet coal is presented. Commercial demonstrations, applications, and operating costs are discussed.

97102585 New progress in the mechanism of coal pyrolysis Liao, H. et a/. Meitan Zhuanhua, lY96, 19. (3), l-8. (In Chinese) New progress in the mechanism of coal pyrolysis are reviewed, focusing on:(I) the formation and transport of volatile products, and (2) network models of coal macromolecules.

97102586 New stage of clean coal technology in Japan Kawaguchi, Y. Sekitan Riyo Gijutsu Kaigi Kmnshu 1996, 6th. I-IO, 279- 282 (In Japanese). The use of coal as an energy source and the development of advanced clean coal technologies including environmentally friendly coal combustion, coal thermal decomposition, and coal cleaning processes are reviewed.

97102587 NO reduction by potassium-containing coal bri- quets effect of mineral matter content and coal rank Garcia-Garcia, A. et 01. Emqp Furls, 1997, 11, (2), 292-298. The NO reduction activity of several potassium-containing coal briquettes obtained from different coal precursors is examined. with the purpose of understanding the effect of coal rank. Two bituminous coal fractions, with two very distinct ash contents. were selected to determine the influence of the mineral matter content of coals in NO reduction. The catalytic effect of potassium in this reaction was evaluated in a fixed-bed flow reactor. The effect of coal rank is manifested in two ways: larger amounts of potassium incorporated in coal briquettes and higher NO reduction activity as the coal rank precursor decreases, regardless of the reaction temperature during the experiment. Ash contents of the coals seem to have a negative effect in the NO-carbon reaction. The ash contents act as a sink that sinters and deactivates the potassium, forming potassium carbonate and silicates which are both inactive for the process.

97102588 Optimization of enrichment conditions of Zongul- dak hard coal with column flotation Dalahmetoglu. 0. and Kemal, M. Changing Scopes Miner. Process., Proc. Int. Miner. Process. Symp.. 6th, 1996. 355-360. Edited by Kemal, M. B., Rotterdam, The Netherlands. A study of Zonguldak coal column flotation, including such variables as feeding level. foam thickness, column height, wash water rate, and air rate.

97102589 A parametric study of dewatering of fine coal Sung, D. J. and Parekh, B. K. Coal Prep. (Gordon & Breach), 1996, 17, (l- 2), 25-38. An experimental design of pressure filtration was used to study fine coal dewatering. The effects of five major process parameters of the dewatering were investigated. The study was started with two factorial experiments to identify the most significant parameters in the filtration process, and concluded with response surface methodologies to establish optimum operating conditions for the dewatering of fine coal.

97102590 Pilot-scale evaluation of hyperbaric filtration of ultra fine clean coal Groppo, J. G. and Parekh, B. K. Coal Prep. (Gordon & Breach), 1996, Il. (l-2), 61-70. An Andritz-Ruthner trailer mounted hyperbaric filter was used to recover minus 200 mesh clean coal by column flotation. Continuous pressure filtration was conducted at pilot-scale on the recovered coal. Results showed that increasing vessel pressure for a given cake formation angle (CFA), increased cake thickness and throughput while decreasing cake moisture. The use of flocculants increased throughput but also increased cake moisture.

97102591 Possibility of securing uniform coal grade for thermal power generating plants by mining and storage process control Simic, R. D. et rd. hoc. Annu. Id. Pitt.~hrrrgh Coal Conf., lY96, 13, (2). 820-825. An analysis of coal grade variations was carried out for an open-pit coal mine at a power generation plant and measures were proposed for grade uniformity.

97102592 Pretreatment equipment for coal charge for coke oven Igai. K. et al. Jpn. Kokai Tokkyo Koho JP 09 31,471 197 31,471] (Cl. CIOBS7/10), 4 Feb 1997. Appl. 951177,620, 13 Jul 1995, 4 pp. (In Japanese) The paper introduces pretreatment equipment for feeding coal charge to a coke oven. It comprises a dryer with classification capability, a collecting apparatus for pulverized coal, a slurry tank, a wet-type granulating apparatus, a dewatering apparatus, and a coal transporting conveyor.

97102593 Pretreatment of coal before supplying in coke oven Igai, K. et al. Jpn. Kokai Tokkyo Koho JP OY 31,469 (97 31,469] (Cl. ClOB53/04), 4 Feb lYY7, Appl. 951177,619, I3 Jul 1995, 4 pp. (In Japanese) The separation of dry coal into coarse powder and fine powder, is then followed by the granulation of a slurry comprising the fine powder, heavy oil and water to give formed coal of particle size larger than the separation point. This is dehydrated and blended with the coarse powder to give product for charging to coke oven. The coal shows prevention of dust dispersion in carbonization.

97102594 Pyrite removal from coal by microbial leaching Shu. X.rt al. Mei!nn Zhuarthuu 199f1, 19, (4). 24-30. (In Chinehe)

97102595 Reducing the biased slurry feed subdivision in vertical pipe T-junctions using partition wall and stratifier Hu, S. et u[. Miner. Eng., 1997, 10, (2), 163-174. In the coal and mineral processing industry, biased subdivision of slurry feed to a number of unit operations in parallel has been recognized as a problem to be solved. This results in each unit in a multi-unit system to operate with different separation density, particle size distribution and solids concentration. Consequently, some of the units may operate under far from favourable conditions, leading to a significant decrease in the operating efficiencies of the sizing and cleaning units in coal preparation plants. The objective of thi\ work i< to develop new and more robust approaches or devices for unbiased slurry subdivision. The paper propose, the modification of simple T-type splitters with a partition wall or a stratifier to create new slurry flow splitters. A serie\ of rxperimcnts were carried out with a vertical pipe having a T-junction to compare the performance of various approaches to slurry splitting. Effects of flow rate, particle size, density, solids concentration and branch orientation were studied. and the results show that new splitters are very effective in reducing the degree of biased subdivision of slurry flows in vertical T-junctions.

97102596 Reflectance analysis of coal feedstocks: the desired and the actual Kiselev. B. P. Koks /(him. 1996, (Y). I l-14. (In Russian) The use of vitrinite reflectance for compounding coal charges for coking. Including the use of lower grade coals is discussed.

97102597 Rehabilitation of an anthracite-burning power plant in Ukraine with introduction of coal preparation Ruether, J. et ul. Proc. Annu. Int. Pittsburgh Cotrl Con/:, 1996. 13, (2). 1175-l 180. A joint study regarding the rehabilitation of an anthracite-burning power station in the Do&ass region of eastern Ukraine, is being conducted by the United States Department of Energy and the Ukrainian Ministry of Power and Electrification. The Luganskaya GRES power station is labouring under deteriorating coal quality and the physical plant is in need of repair. Approaches under consideration for the rehabilitation include upgrading the existing 200-MW, (gross) wall-fired boilers, re-powering with circulating fluidized bed comhustors, and the use of coal preparation. Results of coal washability tests indicate the coal is amenable to washing. Potential approaches for coal preparation are presented for design value coal for wall-fired boilers while minimizing rejection of Btus and generation of solid waste.

Fuel and Energy Abstracts July 1997 215

0 1 Solid fuels (preparation)

97lO2598 Role of carboxyl groups in the disintegration of brown coal briquettes by water sorption Ozaki. J.-i. CI nl. Fuel Protuc,. Techrrol.. 1997, 50. (I). 57-6X. By means of water sorption on model briquettes made from acid-washed, cation-exchanged. water vapour-conditioned. and heat-treated coals, the role of carboxyl groups in the disintegration of hrown coal briquettes was investigated. Cracks were observed on the surfaces of briquettes with initial sorption rates of >0.06 g-H20/g coal-minimum The results from acid- washed and cation-exchanged coals revealed that the carboxylate cations act as hydration sites to promote the disintegration. whereas carboxyl groups act as hydrogen bonding sites to prevent it. A negative correlation between r,,,, and the amount of carboxyl groups present demonstrated the effectiveness of carboxyl groups in preventing the disintegration. Heat- treated coals showed a rapid decrease in r,“, up to 2OO”C, in which there is no significant change in the carhoxyl group content. This was explained in terms of swelling suppression.

97/02599 Scanning electron microscopy analysis of coal products from different comminution methods Zhu, Q. et al. Fluidlfnr?. Sep. J.. 1996, 9, (3). 181-184. Products resulting from the comminution of four coals possessing different hardness, sulfur content, and mineral-matter distribution were analysed in this study. Physical property analyses and mineral liberation studies were conducted. The physical properties were studied using a scanning electron microscope (SEM) and SEM-IPS image analysis system. Mineral matter, pyrite. and carbonaceous material were identified, and the area fraction of each was determined from the backscattered electron images. The shape difference of coal particles from various comminution processes are described using a circular shape factor. The paper analyses the results of these laboratory studies.

97102600 Screen dewatering of coal-clay waste from prepara- tion plants Schemer. B. J. Coal Prep., lY96, 17, (l-2), 39-46. The author presents a flocculation-screening technique to dewater coal-clay waste, developed by the Bureau of Mines at Tuscaloosa Research Center. The technique involves flocculation of the waste stream with polyethylene oxide and dewatering of the resulting floes on a static screen. Test results are described from pilot plant and field testing of four different wastes. Coal dewatering is also discussed in general, with the effect of particle size on dewatering efficiency.

97102601 Separation of coal particles from Soma fly ash by flotation Bayat, 0. and Toraman, 0. Y. Changing Scopes Miner. Process., Proc. Int. Miner. f’mcess. Symp., 6th. 1996, 469-473. Edited by Kemal, M. B.. Rotterdam, Neth. Fly ash flotation from the Soma Power Plant gave a 65.06%burnable unburned carbon fraction with 37.56% ash at pH 6.0, 30’C and 6.24 lit concentration of kerosene + pine oil. The consumption of the reagents was comparatively high in all experiments and the process economy for operation on a technical scale may be unsatisfactory. Experiments should therefore be carried out using various reagent types to improve the process economy.

97102602 Solid state 13C CPIMAS-study of changes in coal structure after rapid heating Kawashima. H. et al. Shigen fo Kar~kyo, 1996, 5, (6), 397-402. (In Japanese). Changes in coal structure of Akabira coal were examined by solid state 13C NMR after heat-treatment at 3 Kimin or 100 Kimin at 723 K under nitrogen flow. The author suggests that the increase witnessed in molecular mobility and THFS with heating rate may have been due to enhanced thermal plasticity.

97102603 Solubilization of an Australian brown coal oxidized with hydrogen peroxide in conventionally used solvents at room temperature Mae, K. et rrl. Prepr. Pap. Am. Chem. SW., Div. Fuel Chem.. 1997, 42, (1). 176-l 80. The oxidization of an Australian brown coal took place with hydrogen peroxide at 60°C for 2 h. Subsequently, extraction with alcohol-based binary solvents at room temperature was undertaken, to give a maximum extract yield of >80 wt7c.

97102604 Status of foreign R&D programs in the area of ecologically clean coal technologies Vyskubenko, Y. A. 1~1,. Akad. Nauk, Energ., 1996, (S), 1 l-30 (In Russian) The current status of technlogical and R&D for decreased emissions from coal-fired power stations in the USA is evaluated. These include clean combustion, flue gas treatment, and coal treatment.

97102605 Studies on the use of perchloroethylene as a heavy medium for the removal of pyrites from coal Theme. T. L. rf crl. Proc.-Annu. fnt. Pitfshurgh Cool Cm/:. IYYh, l3.(2). 1030-I 035. Perchloroethylene (PCE) has shown promise for USC as a heavy medium tor the removal of pyrites from fine coal. Mixtures of PCE and kerosene arc investigated here to determine their effectiveness for coal cleaning. Floati sink experiments are undertaken for different medium densities obtained by varying the proportions of PCE and kerosene. Data taken from a long tube sampling apparatus is used to evaluate the mixtures. The data support\ scale-up predictions for a plant apparatus.

97102606 Study on factors affecting microbial solubilization of lignite. Tong, W. ef al. Mcrtan Zhrrarrhr~~. 1996, 19, (3), 63-68. (In Chinese) Zalainuoer and Pingzhuang lignites were subjected to soluhization tests. carried out with Polyporus versicolor and Candida ML-13. The conversion of microbial soluhilization of lignites was shown to he affected by the incubation conditions, such as the component of incubation medium. the amount of inoculum, and solubilization methods.

97102607 Study on multistage hydropyrolysis of coal by thermogravimetry Li, W. and Li. B. Run&o Huuxue X~tehuo, IYYh. 24. (6). 480-4X4 (In Chinese) Xianfeng lignite. Datong bituminous coal and Yanzhou high sulfur coal were subjected to multi-stage hydropyrolysis and the results were investigated. The results show that the conversion of coal at high heating rate in multi-stage hydropyrolysis is higher than that at constantly~ slow heating rate. The multi-stage hydropyrolysis process is an ideal deaulfur- ization method for pro-combustion utilization. The sulfur removal of Yanzhou coal can reach 90%.

97102608 mineral coal

Supercritical fluid extraction of a high-ash Brazilian

Rocha, S. R. P. et ul. Process Tech&. Proc.. 1906. I2 (High Pressure Chemical Engtneering), 185%IYO. Experiments were carried out to determine the effects of extraction temperature, solvent density and addition of co-solvents on the conversion, liquid yield and the characteristics of the extracts and residues from SCFE with toluene of a high-ash Brazilian mineral coal. investigated. The experiments were performed in a semi-hatch. laboratory-scale unit at 593-673 K and up to 1 I5 MPa.

97102609 Surface changes in coals after oxidation. 1. X-ray photoelectron spectroscopy studies Grzybek, T. and Kreiner, K. Langmuir, lY97, 13, (S) YOY-Yl2. The effect of liquid-phase oxidation on the surface structure of coal\ was studied by XPS. The surface composition changes. together with the content ratio of N/C, prove the applicability of the two-component model to describe the structure of coal. The mobile phase contains sulfur but no nitrogen compounds. Detailed discussion of the formation of oxygen- containing surface groups is facilitated by the analysis of the C( Is) peak shape.

97102610 Surface changes in coals after oxidation. 2. Hz0 sorption studies Grzyhek, T. et al. Langmuir. 1997, 13, (5), 1123-l 127. Quantitative characterization of the effects of oxidation on the surface of coal based on water sorption measurements were undertaken. Two coals of different rank were examined before and after oxidation with H202 and KMnO+ A theoretical model describing sorption equilibrium, as the effect of adsorption in submicropores and absorption in the elastic phase of coal. was applied to evaluate structural and energetic parameters of the sorption systems. A noticeable increase in the adsorption capacity of the studied coals followed oxidation and absorption was virtually unaffected by it. This is due to creation of new oxygen-containing surface groups on the coal surface, as was shown by XPS measurements. Results showed a significant increase in the adsorption energy, together with much smaller changes in water molecule concentration on the coal surface. This suggests an increase in the number of double bonds between adsorbed water molecules and oxygen-containing surface groups.

97102611 Surface chemical control of ultra-fine coal to improve dewatering Groppo, J. G. and Parekh, B. K. Coul Prep. (Gor-don & Brmch), lYY6, 17, (l-2), 103-116. A combination of metal ions and surfactants were used in conventional vacuum filtration to lower the filter cake moisture of ultra-fine coal to 20%. The moisture reduction results from the formation of hydrophobic micro- aggregates which facilitates dewatering.

97102612 Swelling of a German brown coal in acetone-water and methanol-water mixtures Jones, J. C. er al. Fuel, 1997, 76, (7), 567-573. The coal swelling that arose when German brown coal samples were treated with acetone-water and methanol-water mixtures of different compositions was measured. These mixtures have higher solubility parameters than

216 Fuel and Energy Abstracts July 1997