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449Three dimensional mathematical models for sim ulating furnace processes with clear 2D and 3D repre sentation of results, which have found wide use in recent years, serves as an essential aid for analyzing technical solutions used in designing equipment and experimental data obtained on boilers. Undoubtedly, applications of software systems implementing the methods of computational hydrodynamics for simu lating furnace processes will find growing use as these packages become more advanced and as solution of new problems is imposed on them. At the same time, one should not fully rely on trustworthiness of the results obtained from using complex scientifically sub stantiated models. This relates primarily to calcula tions carried out for arbitrary kinds of coal and boiler design, including determination of the total heat transfer in the furnace (the amount of absorbed heat and temperature of gas flow at the furnace outlet ).The results obtained from calculations of the total heat transfer in a furnace using both empirical meth ods and mathematical models depend to a determining extent on selection of the quantity characterizing the thermal resistance of waterwall tubes with deposits. In the standard method [1], the thermal efficiency coef ficient ψ 98 and ζ 98 = ψ 98 /x ww , where x ww is the water wall view factor, are used as indicators that take into account degraded absorption of heat by a waterwall covered with deposits (here and henceforth, the super script "98" means that the indicators correspond to the values specified in the third edition of the standard method of thermal design [1]). In the zone wise cal culation method [2] and in the mathematical models f '' ϑ of a furnace process, thermal resistance of waterwalls Ro (m 2 °C/kW) or a heat conductance coefficient or heat flux (quantities functionally connected with Ro) are specified.We point out once again that the normative thermal efficiency coefficient of waterwalls ψ 98 is not a suffi cient physical characteristic of external deposits (in particular, the same value of ψ 98 may correspond to real state of a waterwall ranging from its operationally clean to slagged state) [3][4][5]. Its values were selected as empirical coefficients intended for bringing the results obtained using this method in consistency with experimental data on the total heat transfer. It should be pointed out that the values of ψ 98 are underesti mated as compared with its true values if the waterwall thermal efficiency coefficient is understood to mean the experimentally determined and physically sub stantiated ratio between the absorbed q abs and incident q inc heat fluxes: ψ = q abs /q inc = (1 -q rev )/q inc , where q rev is the reverse heat flux. Figure 1 shows the values of the coefficient ψ 98 calculated using the standard method taking into account experimental data and ψ av = Σ(q abs /q inc ) determined from the results of zone wise calculation (summation by elements). It should be noted that the values of normative coefficients could be taken closer to their real valu...

It is shown that out-of-design coal should be used only after computational analysis of slagging of the boiler. The use of ash fusibility as a criterion for the analysis should be avoided because this property does not reflect the slagging properties of coal to an acceptable degree. Parameters characterizing the properties more appropriately are presented. It is shown that slagging of an actual furnace depends on many factors and the condition that "the thermal stresses should be lower than the limiting value" is insufficient. An algorithm for the analysis is suggested on the basis of the slagging conditions arising upon transition from one kind of fuel to another with allowance for the actual slagging situation.Keywords: out-of-design fuel, mixture of coals, joint firing, mineral part of coal, internal and external zones, slagging of a boiler, fouling based on active alkali, strength properties of deposits.Many thermal power plants fire out-of-design coals due to economic conditions or other factors or consider the possibility of using an alternative fuel in the future. Factors limiting the interchangeability of coals include the difference in their slagging properties. Neglect of this factor can lead not only to impermissible limitations in the operation of a boiler in the period when it fires out-of-design fuel but also to enhanced slagging and disturbed output of the boiler in subsequent operation on conventional or design coal. It is known that the range of coals applicable with respect to the slagging properties can be widened, if there is a possibility of replacing a part of the conventional coal by an out-of-design coal mixture, using the technology of joint firing [1], or operating at reduced loads in the period of firing the unconventional coal.It is obvious that in any situation the use of out-of-design coal should be preceded by a computational analysis of slagging of the boiler. When considering the possibility of the use of coal novel for the power industry the properties of the coal should be studied additionally. It is known that the fusibility of ash does not reflect appropriately the slagging properties of coal and cannot be recommended for analyzing the slagging capacity and ash tapping as is done, for example, in [2].The mineral part of coals. The slagging properties of coals depend primarily on the composition of their mineral part, which is represented by the set of mineral admixtures and mineral elements in the composition of the organic compounds. For low-ash coals like the Kansko-Achinskii ones the latter can exceed substantially half of the entire mineral part. In practice, the mineral part is frequently divided into internal and external ash. The external ash is understood as the fraction that separates easily from the coal substance during milling and contains particles of mineral admixtures and their concretions. The internal ash contains the mineral components of the organic compounds and fine mineral inclusions. As the particles of coal dust burn, the internal ash acquires their tem...

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Catalytic Liquid-Phase Oxidation of Cyclooctane.-The oxidation of cyclooctane (I) with oxygen in the presence of cobalt(III) or manganese(III) acetate catalysts affords the suberic acid (II). Side products are the C 7 -C 5 homologues (pimelic, adipic, and glutaric acid) as well as cyclooctanol and cyclooctanone. The reaction proceeds via a cyclooctylhydroperoxide which is oxidized via a cyclooctanone-catalyst complex to afford the diacid (II). When chromium(III) acetate is used as catalyst, the reaction exclusively affords cyclooctanone. Under oxygen-deficient conditions, the formation of the lower homologues, especially the adipic acid, is preferred. -(CHABUTKINA, E. M.; ARTEM'EVA, N. V.; KUNITSKII, A. A.; ZHUKOV, YU. P.; ANTONOVA, T. N.; Neftekhimiya 38 (1998) 2, 111-114; Yaroslavskii gos. tekh. univ., Yaroslavl' 150023, Russia; RU)