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The laboratorial researches on the rate of oxygen consumption by coal during its self-heating |
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The laboratorial researches on the rate of oxygen consumption by coal during its self-heating Authors: H. Qilin, Y. Shujie
In the laboratory of Shanghai Energy Company Ltd in China the investigations of coal samples from layer No. 8 of Kongzhuang Coal Mine were taken, aiming at marking the rate of oxygen consumption by coal during its self-heating. The investigations were conducted for different grain sizes of coal, at different temperatures and different contents of oxygen in circumjacent atmosphere. Based on the results got from the investigations, the dependence of the rate of oxygen consumption by coal in function of diameter of grains, the temperature and content of oxygen was worked out. The dependence permits to count the rate of oxygen consumption by coal in real conditions, which can facilitate the more exact qualification of susceptibility of coal to self-heating. In the paper the authors described the methodology and original apparatus for marking the rate of oxygen consumption by coal samples.(Fig.1). Some physical characteristics of coal from the layer No. 8 are following: the free moisture W sup ex = 3.1%, the analytic moisture W sup a = 2.3%, the content of ash A sup a = 20.3%, the content of volatile matter V sup a =28.38 %, the content of sulphur S sup t = 0.49%, the content of pyretic sulphur S sup p = 0.26%, the content of hydrogen H = 6.49%, the content of oxygen O = 39.62 %, the content of the element of carbon C = 48.6%. After the samples of coal were crushed, before the investigations they were dried in gas of nitrogen at temperature 35 sup oC, and weighed once a day, so until when the samples don't reduce their weight in next two days. The investigations were conducted at programmed temperatures in thermostatic chamber (round tubular containers). The conditions of investigations were shown in Table 1. The investigations were conducted for different diameters of grains, at different temperatures and different contents of oxygen in flowing air. The grain distributions were accepted as: 6.5--9 mm, 4.5--6.5 mm, 2.5--4.5 mm, 0.9--2.5 mm, 0.25--0.8 mm. (Table 1). Oxygen concentration in inlet air varied from 0.95% to 21%, and the temperature of coal in reaction chamber changed from 30.1 to 195.6 sup oC. From the theory of chemical dynamics and chemical equilibrium it results, that the rate of oxygen consumption by coal is directly proportional to content of oxygen. The rate of oxygen consumption by coal from provided fresh air (C sup ś sub O2 = 9,375 x 10 sup --6 mol/cm sup 3) is presented as formula (5). After the investigations the following dependences connecting with the rate of oxygen consumption by coal samples were worked out: *The dependence of the rate of oxygen consumption by coal sample from dimensionless diameter of grains (Fig. 2, Formula (6)); *The dependence of the dimensionless rate of oxygen consumption from dimensionless temperature (Fig. 3, Formula (8)); *The dependence of ln(V sub O2(T, C sup w sub O2,)) from lnC sup w sub O2, at temperature 80 sup oC (Fig. 4, Formula (9)). *Correcting function psi (d) to the foundation of standard diameter d sub 0 = l cm (Formula (6)); *Correcting function fi (T/T sub 0) to the foundation of standard temperature T sub 0 = 40 sup oC (Formula (8)); *Correcting function fi (C sub O2)to the foundation of standard concentration of oxygen in air delivered as 9.375x10 sup -6 mol/cm sup 3 (Formula(10)). From the investigations in results, that the rate of oxygen consumption by coal depends on diameters of the grains of coal, the temperatures and concentrations of oxygen. Taking into account of the factors above-mentioned in common working, the formula (11) for calculating the rate of oxygen consumption by coal was worked out.
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2011