Physicochemical processes with coal particles in liquid-phase reduction. I

Abstract

901 The reducing agent used in slag melt is coal, which enters the melt at temperatures of 1450‐1500 ° C. The coal undergoes coking here, with heating at 30‐50 K/s or more. The hydrogen, oxygen, and nitrogen in the coal’s organic mass enter the gas phase, along with some of the carbon and sulfur. The remainder of the carbon and the mineral components of the ash remain in the coke residue and subsequently participate in the processes occurring in the bath: combustion with the blast oxygen; and reduction by the metal oxides in the slag melt [1, 2]. To describe and control the processes in the slag bath, we require information on the quantitative and qualitative characteristics of coal coking at typical bath temperatures. There are extensive literature data on the coking of various coals [3, 4]. However, these data mainly refer to relatively low heating rates (10‐20 K/min) and coking temperatures of 900‐1000 ° C, whereas the temperature of the slag bath is 1400‐1500 ° C, with heating rates of 30‐50 K/s. Moreover, interest focuses here on the coking not of the bed but of individual particles. In that case, the following data are required for practical purposes: the yield and composition of the volatiles; the yield of coke and its content of solid carbon and ash; the removal of sulfur; the breakdown of the coal particles; the evaporation and conversion of water in pyrolysis. Because the processes occurring are so complex, it is not possible to obtain such information (except for the coke yield) in practice. Given the lack of experimental data, attempts have been made to calculate the corresponding characteristics [5]. The only remaining option is to formulate laboratory experiments corresponding to the operating conditions of the liquid-phase reduction system. In the present work, the experiments are conducted on OS Anzhersk coal from the Kuznetsk Basin, with the characteristics in Table 1. The yield and composition of volatiles are determined on equipment including a reactor, a flask with fiberglass for the absorption of tar, a flask with calcium chloride for the absorption of water, a flask with KOH for the absorption of CO 2 , a vessel with activated coal for the absorption of benzene and its derivatives, and a gasometer for gas collection. Before beginning the experiment, all the traps are weighed. In the experiment, the temperature of the trap for tar condensation is maintained at 125 ° C. To prevent further reaction of the decomposition products and the gaseous atmosphere of the reactor with the coke residue, pyrolysis is conducted in the volume of a slag (or metallic) melt. Tin is used as the metallic melt. A series of experiments on pyrolysis are also conducted in the reactor with no liquid phase. This corresponds to pyrolysis at the surface of the slag melt. The experimental results obtained here are identical.