04 By-products related to fuels

97102816 New knowledge about effects of bituminous coal fly ash in concrete Haerdtl, R. ef al. VGB Krafiwerkstech., 1996, 76, (II), 953-956. (In German) The results of studies into the reaction of bituminous coal fly ash in concrete are reported, with specific focus on the mechanisms during the pozzolanic reaction of the fly ash and the resulting changes to the concrete structure. The investigation covered eight different cements representing the types of cement most commonly used in Germany.

97102817 Performance and durability of concrete made with demolition waste and artificial fly ash-clay aggregates Zakaria, M. and Cabrera, J. G. Wusre Wanage, 1996, 16, (l-3), 151-158. Two replacements of natural aggregates under consideration for concrete production are demolition aggregates and artificial aggregates made with waste materials. A laboratory study on the use of demolition waste and artificial aggregates made from fly ash-clay mixtures as coarse aggregates to make concrete is presented. The concretes made either with demolition waste or artificial aggregates are compared with a control mix made with natural gravel aggregates. The strength and durability characteristics of these concretes are evaluated using as a criteria compressive strength and transport properties. Concretes of good performance and durability can be produced using aggregates from demolition rubble or using artificial aggregates made with wastes such as fly ash.

97102818 Pitch mesophase and a new type of high strength carbon material Xia, J. and Zhou, S. Zhongguo Youse Jinshu Xuebuo, 1996, 6, (3) 50-53. (In Chinese) Heating stirring polymerization and pitch mesophase was prepared from petroleum pitch and coal-tar pitch. A new type of hinderless carbon material with self-sintering function was made from the pitch mesophase by grinding, activating adjustment, moulding, and sintering.

97102819 Potential use of fly ash in Colombian blended cements de Gutierrez, R. M. and Delvasto, S. A. Proc. Inr. Co@.’ Solid Was@ Technol. Manage.. 1995, I Ith, paper 3D2, 7pp. The disposal of Colombian coal combustion residues is quite a sizeable problem, as the annual production is currently about 800,000 tonnes. Four different fly ashes were examined and compared. The partial replacement of cement with fly ash reduced the coefficient of chloride diffusion. Fly ash of good quality and incorporated in an optimum proportion, was found to be an excellent cement replacement material.

97102820 Preparation and characterization of mesophase pitches as a matrix precursor of carbon fiber reinforced carbon composite Chung, H. J. and Lim, Y. S. Yoo[> Hukhoechi, 1996, 33, (l2), 1387-1393. (In Korean) The authors report a recently-completed study of mesophase pitch as a matrix precursor of carbon fibre-reinforced carbon (C/C) composite. This study is concerned with the production of mesophase pitch as matrix precursors for C/C composite from coal tar pitch. C/C composite production was found to require a mesophase pitch with about 30-40 ~01% mesophase spherulites to be infiltrated into a fibre preform without a filter effect as a matrix precursor condition. This condition was satisfied with mesophase pitch heat treated at 400°C for 2 h.

97102821 Preparation and testing of experimental batch of activated carbon Drozdnik, 1. D. et al. Koks Khrm., 1996. (ll), 33-36. (In Russian) Thermo-oxidation, carbonization, and activation were employed in the preparation of activated carbon from long-flame coal. The obtained product exhibited high adsorption activity to compounds soluble in CC14, to petroleum products, phenol, toluene, and copper ions. The sorbent is especially suitable in industrial wastewater purification.

97102822 Preparation of activated carbons from bituminous coals with CO* activation-influence of coal oxidation. Tong, H. et al. Carbon, 1997, 35, (2) 275-283. Three Australian bituminous coals were used for the preparation of activated carbons. The influence of coal oxidation on the carbonization and activation processes and on the structure of the resulting activated carbons were explored. For the carbons from the oxidized coals, the activation rate in CO2 was higher and the structure more accessible for CO? penetration.

97102823 Research on fly ash in China-its properties and engineering use Fan, W. Environ. Geotechnol., Proc. In?. Symp., 3rd, 1996, I, 445-454. Edited by Fang, H.-Y. Inyang, H. I., Technomic, Lancaster, Pa. This article focuses properties and major uses of coal-fired power plant fly ash in China over the last few years until 1989 is given. Topics discussed include: engineering properties of fly ash, macroscopic study, engineering uses of fly ash and current research on applications of fly ash and other wastes at Taiyuan University of Technology.

97102824 Sintering characteristics of low-rank coal ashes Jung, B. Korean .I. Chem. Eng., 1996, 13, (6). 633-639. Measurements wer made of the electrical resistance and compressive strength to gain a better understanding of the sintering characteristics of low-rank coal ashes involved in deposit formation in combustion systems. Low-rank coal ashes were prepared by the standard ASTM ashing procedures at 750°C and then separated into three different particle size fractions, The sinter point determined by the electrical resistance method decreased with decreasing particle size at three different particle size fractions of each coal ash. At a given sintering temperature, strength of the sintered ash was inversely proportional to particle size. For any given particle size of each coal ash, the strength increased with increasing sintering temperature. X-ray diffraction of the sintered coal ashes showed that, as sintering temperature increased, there was an inverse relationship between sinter strength and the amount of anhydrite in the sintered ash.

97102825 Sintering of powders of polyaromatic mesophase to high-strength isotropic carbons. 111. Powders based on an iron-catalyzed mesophase synthesis Braun, M. and Huettinger, K. J. Carbon, lY96, 34. (I?), 1473-1491. Coal tar pitch was subjected to iron-catalysed pyrolysis to synthesize a spherulitic mesophase pitch. The isotropic pitch is removed to v,arious extents by solvent extraction. The thermoplasticity of the resulting raw mesophase powders is adjusted by treatment with oxygen vvith respect to optimum sintering properties. The individual process steps and intermedi- ate products were analysed.

97102826 Strength of compacting mortar and concrete con- taining of micro grinding-high volume fly ash Tashiro. C. ef al. Sernento Konkuriiro, 1996. 598, 41-45. (In Japanese) Portland cement and finely ground, coal-burned fly ash and fine aggregate and NazS04 were mixed to prepare mortar specimens ot high-blended fraction of fly ash. The Na&i04 acted as an alkali activator for the pozzolanic reaction of the ash. Compressive strength of the hardened mortar specimens became lower for those having higher weight fraction of the ash. but it increased almost linearly with the progress of the curing period. The value was -400 kg/cm- after 7 days of curmg for the specimen having 0.6 wt fraction of the ash. Partial and progressive substitution of fluidized-bed ash for the fly ash resulted in gradual decrease of the compressive strength of the hardened mortar specimens. Similar results were obtained for the hardened concrete specimen\.

97102827 Studies on the synthesis of ZSM-5 molecular sieve using dacite and fine coal ash Jiao, Q. er al. Guisuanyan Tongbao, 1996, 15, (4), 29-31. 3X. (In Chincsc) The synthesis of a ZSM-S molecular sieve from dacite and fine coal ash took place in a hydrothermal system at autogenous pressure. The sieve showed opened pores and high thermal stability and may he used as catalyst at high temperature.

97102828 Study of the aperture material made from fly ash Wang, L. and Xiang, H. Proc. Int. Conf. Solid Waste Techno/. Munuge., 1996, 12, Paper 7A3, 9pp. Fly ash, binder, curing agent. foamer and modifier comprise the non- autoclaved fly ash aperture material used for industrial heat pipes. Simple processes, such as homogeneous mixing, casting and curing under atmos- pheric temperature are employed to produce the material. Its microstruc- ture was investigated by scanning electronic microscope, X-ray diffraction and DTA, and the factors that influence its strength and heat resistance are discussed. The low cost material is widely used in thermal insulation engineering.

97102829 Study on structure characteristics and computa- tional method of coal ash melts Xiong, Y. and Sun, X. M&an Zhuanhuu, 1996, 19, (4), 85-91. (In Chinese). Based on the ionization potential of ions, a structure property index PIM was proposed as a supplement to the NBOIT (non-bridging oxygen per tetrahedrally coordinate cation) index. This is intended for accessing the polymerization of Al silicate in the ash of Chinese bituminous coals which lack alkali and alkali earth elements. The PIM index takes the roles and contributions of each element in the structure into account and represents the Coulomb strength of an ash melt structure.

97102830 Sulfate resistance of concrete containing fly ash Schiessl, Peter et al/ Beronwerk Fertigteil-Tech.. 1996, 62, (12), 97-98, IOO- 105. (In English/German) An investigation into the sulfate resistance (SR) of concrete containing fly ash (FA). SR criteria and testing methods are described, followed with the results of the interaction of various concretes and FA. The same criteria are applied for the assessment of the influence of FA on SR that are used for the admission of cements with a high SR. Recommendations for the use of FA for the production of concretes with a high SR are outlined on the basis of the most unfavourable combination of cement and FA. The experimental results show that mixtures can be obtained which have a high SR comparable to an high sulfur cement according to DIN 1164.

232 Fuel and Energy Abstracts July 1997