Upgrading of low-grade metallurgical coke by CH_4 cracking

1.为了对焦炭进行改性，提高焦炭的抗氧化性，采用甲烷裂解法对焦炭进行了渗透改性。观察了冶金焦在渗透和氧化过程中孔结构的变化。实验证明，渗透后的焦炭氧化后的机械强度高于未渗透的焦炭。结果表明：1）渗透后焦炭的反应性指数（CRI）从32左右降低到18左右; 2）对渗透后焦炭的反应后强度（CSR）进行了测定。CSR指数从56左右增加到77，与极高品位焦炭的CSR指数相当。3）CSR的增强是由于中孔中的碳沉积，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，以活性炭为样品。采用N2吸附-脱附法对介孔和微孔（包括亚微孔）进行了表征。中孔和大孔也具有压汞孔隙率的特征。结果表明：1）浸渍后活性炭的微孔体积和比表面积分别减少到原始样品的0.1%和0.2%左右;在微孔中，底层被完全填充。中孔和大孔的体积和比表面积分别减少3%和32%左右; 2）氧化时，大孔中沉积的碳几乎燃烧殆尽，而中孔和微孔中沉积的碳仅部分燃烧;微孔中的碳比表面积增加最小。从这些实验结果可以推断，微孔中的沉积碳起着阻挡CO2侵入的主要作用，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.