Effect of gasifying agents and calcium oxide on gasification of low-rank coal and wastes

The process of gasification is one of the promising technologies of clean combustible gas production from low-grade coals, such as lignite, coal mud and subbituminous LR coals, and from biomass and waste. However, depending on the type of gasification material, the following aspects require investigation and development: the selection of a gasification technology (including parameters and gasifying agents) and the removal of the components constituting a burden and contamination from the raw gas. This paper presents the results of research on the gasification of lignite and sludge with added refuse derived fuel and the gasification of both these substances with added calcium sorbents. Two gasifying agents, water vapour and carbon dioxide, were used in the experiments, which were carried out in a fixed bed reactor at the temperatures of 600, 700, 800, 900, and 1000 ◦C. The effects of process temperature, the calcium oxide addition and the gasifying agent composition and quantity on fuel conversion and product gas composition have been determined. Higher process temperatures in both atmosphere of gasification (H2O and CO2) cause an increase in the volume fraction of hydrogen and carbon monoxide in the resulting gas. The effect of the addition of calcium oxide (CaO) for carbon dioxide gasification of sewage sludge exhibits the positive effect. The increase in the volume of hydrogen and carbon monoxide in the syngas from gasification of sewage was observed. The gasifying agent has a different effect on the composition of the gas depending on the temperature. The gasification process in the atmosphere of water vapour starts faster than in the atmosphere of carbon dioxide and hydrogen formation is significantly higher.