A comparative study of the reaction mechanism for deep reduction hydrogen production using two special steel solid wastes and a chemical looping hydrogen production scheme

Abstract

Pickling sludge (PS) and presintered waste (PW) are two special steel solid wastes that have potential as oxygen carriers due to their Fe content. Using these raw materials to produce hydrogen allows for the resource utilization of solid waste, which has good environmental effects. Here, we studied the deep reduction-hydrogen production characteristics. Specifically, the effects of temperature, papermaking sludge (PMS) blended ratio, and reaction time on the deep reduction characteristics of Fe in pickling sludge and presintered waste were studied. On this basis, the study also aimed to investigate the effects of temperature and PMS blended ratio on hydrogen production. The results indicated that when exposed to high temperature, PMS shows the ability to effectively reduce pickling sludge and presintered waste. The maximum Fe recovery rate can reach 65.63 and 96.94 % in a fixed bed reactor operating at 700 °C and a blended ratio of approximately 10 %. Under the conditions of 900 °C and 15 %/50 % papermaking sludge addition, the Fe content within pickling sludge and presintered waste was reduced to FeCr2O4 and FeO, respectively. Subsequently, during the reaction with steam, Fe2O3 and Fe3O4 were generated in PS and PW, respectively. The hydrogen production per unit mass of Fe2O3 in pickling sludge is higher due to the existence of the FeCr2O4 spinel structure in the reduction product of pickling sludge. According to the above results, two hydrogen production strategies of PS and PW through different deep reduction paths are proposed.