819 ISSN 1990-7931, Russian Journal of Physical Chemistry B, 2021, Vol. 15, No. 5, pp. 819–826. © Pleiades Publishing, Ltd., 2021. Russian Text © The Author(s), 2021, published in Khimicheskaya Fizika, 2021, Vol. 40, No. 9, pp. 27–34. Energy Efficiency of the Gasification of a Dense Layer of Solid Fuels in the Filter Combustion Mode V. M. Kislov a, *, M. V. Tsvetkov a , A. Yu. Zaichenko a , D. N. Podlesniy a , and E. A. Salgansky a a Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Russia *e-mail: vmkislov@icp.ac.ru Received February 25, 2021; revised March 18, 2021; accepted March 22, 2021 Abstract—The energy efficiency of the gasification of various solid fuels in the filtration combustion mode is evaluated. The modes of gasification of carbon and organic fuels with the moisture content of up to 70% and ash content of up to 90% are considered. The efficiency of air gasification of low-moisture carbon fuels does not exceed 70%; and of organic fuels, 85%. The efficiency of the air gasification of high-moisture fuels can reach 85–90%. The addition of steam to the gaseous oxidizer increases the efficiency of the process. The effi- ciency of steam-air the gasification of low-moisture low-ash carbon fuels reaches 85%. In the case of organic fuels, the maximum efficiency of steam-air gasification is observed for fuels with an ash content of 20 to 40%. For highly reactive fuels, the maximum efficiency is observed for ashless fuels. If the reactivity of the fuel is low, the highest gasification efficiency will be for high ash fuels. Keywords: filtration combustion, gasification, solid fuel, high ash fuel, high moisture fuel, efficiency DOI: 10.1134/S1990793121050055 INTRODUCTION Filtration combustion is one of the promising methods for processing solid fuels. Studies of the fil- tration combustion of various types of coal, peat, wood, and some types of solid combustible waste have shown that this mode has a wider range of fuels accept- able for processing the ash and moisture content than the other known methods [1–3]. This is achieved as a result of the heat exchange between flows of solid and gaseous substances moving towards each other relative to the front of the chemical reaction [4, 5]. Depending on the thermophysical characteristics of the flows of the solid and gas phases, various ther- mal combustion modes can be realized [6, 7]. The most efficient heat exchange occurs when the heat capacities of the phases’ flows are equal; therefore, the presence of a noticeable amount of mineral compo- nents in the fuel is not always a disadvantage [8, 9]. During filtration combustion, due to the countercur- rent flow of reagents, the oxidizer entering through one of the ends of the reactor is heated during filtra- tion through a layer of hot ash residue leaving the com- bustion zone, and hot gaseous combustion products transfer their heat to the original fuel entering through the opposite end of the reactor [10, 11]. Thus, most of the heat released in chemical reactions is not removed from the reactor but concentrated in the combustion zone. Due to the intensive heat recovery from the combustion products to the initial reagents, the com- bustion temperature can be significantly higher than the calculated adiabatic temperature [12, 13]. It has been experimentally established that the effi- ciency of processing a number of hardly combustible materials with a low ash content, for example, viscous hydrocarbon liquids, can be significantly increased by mixing the initial fuel with a solid noncombustible material [14, 15]. The energy parameters of gasifica- tion obtained in this case have higher values than when burning fuel with the addition of wood or peat [16, 17]. At the same time, the composition of products, tem- perature, and combustion rate determined as a result of experiments do not provide comprehensive infor- mation on the nature of the process [18, 19]. For a cor- rect comparison of filtration combustion with other methods, it is also necessary to take into account the energy efficiency of the process [20, 21]. The parame- ter for such an assessment is the coefficient of perfor- mance (COP) of the process [22]. However, the com- parison of the COP values given in various works is complicated by the fact that in its calculation the boundaries of the power system under consideration are set to a large extent arbitrarily [23, 24], and the authors themselves decide which energy flows at the input and output from the system should be taken into account. For example, when evaluating the COP of a gas- ifier, is it important to decide whether the physical heat of the gasification products entering the burner should be considered useful? As an example, let us give COMBUSTION, EXPLOSION, AND SHOCK WAVES