石炭をバインダーおよび還元剤として団鉱した硫化亜鉛精鉱の還元律速過程 ＩＩ 亜鉛炭化団鉱の還元律速過程に関する研究

Abstract

The rate-controlling step was examined for the reduction of zincsulfide in a coked briquette which was prepared from zinc sulfide concentrate, calcium oxide (or calcium carbonate) as a sulfur-scavenging agent, and coking coal as both a binder and a reducing agent.It has been found that the obtained data are best fitted byassuming the rate-controlling step of the reaction to be the diffusion of gases involved in the sulfur-scavenging reactions through pores in the solid calcium sulfide layer formed on the surf ce of a calcium oxide particle. From the temperature dependency of the reduction rate of zinc sulfide, the apparent activation energies of the diffusion were found to be 47.3 kcal/mol for the briquette prepared with calcium oxide and 28.5 kcal/mol for that prepared with calcium carbonate, respectively.The difference in the values has been supposedly attributed to the different sizes of pore diameters in the calcium sulfide layers.Though these activation energies seem too large for the pore diffusion of gases, no other rate-controlling step has been found which can better fit the data in the present study, can take into account the non-particulate shape of the carbon in the briquette, and can explain the difference between the effects of calcium oxide and calcium carbonate.