Upgrading of low-grade metallurgical coke by CH_4 cracking

1.为了对焦炭进行改性以提高其抗氧化性，采用甲烷裂解法对焦炭进行渗碳处理。观察了冶金焦炭在渗透氧化过程中孔结构的变化。实验证明，渗碳焦氧化后的机械强度高于未经处理的焦炭。结果表明：1)渗焦后焦炭的反应性指数(CRI)由32降至18；2)渗焦后焦炭的机械强度(CSR)得到了测定。CSR指数从约56增加到77，相当于极高等级焦炭的值。3)CSR的提高是由于中孔中沉积了碳，阻止了氧化过程中微孔面积的增加。为了阐明微孔渗透的机理，以一种活性木炭为样品。用氮气吸附-脱附法对包括亚微孔在内的中孔和微孔进行了表征。中孔和大孔也具有汞孔特征。主要结论如下：1)浸渍后的活性炭微孔体积和比表面积分别减少到原来的0.1%和0.2%左右。在微孔中，亚微孔被完全填充。中孔和大孔的体积和比表面积的减少率分别约为3%和32%。2)氧化时，沉积在大孔中的碳几乎被烧毁，而沉积在中孔和微孔中的碳只被部分烧毁，浸渍样品的比表面积增加的比例对微孔最小。从这些实验结果可以推断，沉积在微孔中的碳起到了阻挡CO2入侵的主要作用，从而提高了抗氧化性。

1. In order to modify the coke so as to increase the oxidation resistance, coke was infiltration by methane cracking. The pore structure change of metallurgical coke accompanying infiltration and oxidation was observed. It was proved experimentally that the mechanical strength after oxidation for the infiltrated coke was higher than for untreated coke. The result is summarized as follows :1) Coke reactvity index (CRI) decreased from about 32 to 18 by infiltration.2) The mechanical strength of coke after reaction (CSR) was measured for the infiltrated coke. The index of CSR increased from about 56 to 77 which corresponds to the value of the extremely high grade coke.3) The enhancement of CSR is caused by the deposited carbon in meso-pores, preventing from increase in the area of micropores during oxidation.2. To ellucidate the mechanism of infiltration of micropores, an activated charcoa was used as a sample. The meso-and the micropores including submicropores were characterized by use of N2 adsorption-desorption method. The meso-and macropores were also characterized by mercury porosimety. The conclusions are summarized as follows.1) The volume and the surface area of micropores of the infiltrated activated charcoal are reduced to about 0.1 and 0.2% of those of the original sample, respectively. Among the micropores, the submicropore is filled completely. Concerning the mesopore and the macropore, the decrease ratio is about 3% and 32% for volume and surface area, respectively.2) When oxidized, the carbon which deposited in macropores is almost burned but that in meso-and micropores is only partly burned ; The ratio of increase in surface area of the infiltrated sample is smallest for the micropores. From these experimental results, it is deducible that the deposited carbon in micropores plays the major role for blocking CO2 intruding, thereby the resistance against oxidation is enhanced.