Effect of the rate of pulverized coal preheating on char reactivity

Abstract

Abstract-The effect of the preheating rate of the char particles from Kuznetsk bituminous coal on their specific reaction rate was determined. The experiments were carried out with char samples with mean diameters of 0.15 and 0.35 mm heated to temperatures of 900-1000°C. It was found that the specific surface area of the initial coal, measured by CO 2 adsorption at 273 K, for rapid and slow heat treatments increased more that two times. According to the results of thermogravimetric analysis, it was established that rapid pyrolysis in a muffle furnace led to the production of char whose maximum specific reaction rate was higher than that of the samples after slow pyrolysis. DOI: 10.3103/S0361521917010037The efficient and environmentally appropriate use of coals for the generation of thermal and electrical power and the production of metallurgical coke is a problem of considerable current interest. A possible solution of this problem is the development of scientific fundamentals for a solid fuel preparation technology, which will make it possible to considerably increase the quality of fuel due to its partial gasification. The preliminary thermal preparation of fuel is one of such technologies [1]. On the thermal preparation of fuel, its partial gasification occurs in the burner volume, and a highly reactive mixture, which consists of combustible gases and coal char as the products of gasification, is formed at the inlet of the combustion chamber. As found experimentally [2][3][4][5][6][7], the pyrolysis temperature, the heating rate, and the pressure at the zone where volatile matter release and burning have an effect on the char reactivity and lead to changes in its structure. High-rank coals remain less sensitive to such a thermal activation/deactivation.A pyrolysis temperature increase and a decrease of the coal heating rate led to a decrease in the chemical reaction activity of char with reactant gases [2][3][4][5]. Senneca and Salatino [8] also noted a similar effect based on calculations performed with the use of bituminous coal sample; in this case, as the diameter of particles was increased, thermal deactivation came into play at a lower temperature and at a smaller degree of conversion of the sample.Data on changes in the properties of coals upon heating [9], on the dynamics of volatile matter release upon thermal destruction [10], and on changes in the porous structure of char during combustion [11] are widely available in the publications of Russian researchers; however, it is difficult to combine them for an integrated consideration of the effects on reactivity. As a successful example, Maistrenko et al. [12] reported in 1990 the results of an integrated study for anthracite concerning the effect of pyrolysis temperature on the subsequent rate of conversion in an atmosphere of CO 2 and O 2 .From a practical point of view, coal from the Kuznetsk Basin is of considerable current interest for the development of promising technologies with an integrated gasification combined cycle [13]. The conditions o...

Numerical Investigation of Coal and Biomass Co-Gasification Regimes in Entrained-Flow Oxygen-Steam Blown Reactor

“…1. Для других сортов топлива эти коэффициенты могут быть получены кинетическими методами термического анализа [16,17].…”

Potential of composite fuel application based on low-grade coal and wastes of forest and flour industry

“…Samples with 20 mg mass were used for experiments. The heating rate was 10 K/min and the maximal temperature was 1373 K [13,14].…”

Research of rheological properties improvement methods of coal-water fuel based on low-grade coal

“…Thus, domestic power plants are forced to use low-grade coal, which leads to environmental issues that require development and implementation of new efficient technologies that ensure full use of produced fuel and significant economic effect [6].…”