Waste coal gasification fine slag disposal mode via a promising “efficient non-evaporative dewatering & mixed combustion”: A comprehensive theoretical analysis of energy recovery and environmental benefits

Abstract

Coal gasification technology is an important starting source for the clean conversion and utilization of coal. Gasification fine slag (GFS) is the waste produced in the coal gasification process, its production and storage volume are increasing with the large-scale promotion of coal gasification technology. Currently, the GFS black water is processed by the horizontal belt filter and the moisture content of the obtained filter cake exceeds 50%, which has posed challenges to the environment and energy security. The study aims to solve the problems of environmental pollution and resource waste caused by high moisture GFS filter cake. The analysis of the basic physical properties of GFS and the recommendation of a high-efficiency dehydration technology of GFS under the combined action of “vacuum force-mechanical pressure-vibration force” was promoted, and the moisture of filter cake was reduced to 30% at lower energy consumption. By establishing a thermodynamic model, the quality and energy balance of GFS dehydration and mixed combustion process were studied, and the energy consumption and calorific value characteristics of mixed combustion in the two dehydration routes of “horizontal belt filter dehydration-high moisture filter cake mixed combustion” and “multi-energy field dehydration-low moisture filter cake mixed combustion” were compared. Based on comparing the energy consumption of multi-energy field dehydration and evaporation drying, the CO2 emission reduction was evaluated by unifying energy grades and a high-efficiency energy-saving path was analyzed. The studies showed that the GFS can be efficiently dehydrated through the multi-energy field, and the energy-saving is 47.3% compared with the current dehydration method. Through the establishment and analysis of thermodynamic models, it is found that the low-moisture GFS filter cake mixed combustion with coal has energy advantages. With standard coal consumption compared and CO2 emissions estimated, the multi-energy field dehydration technology reduces carbon dioxide emissions by 87.09% compared with evaporation drying. The research results will provide theoretical and technical support for the technical integration of efficient dewatering, carbon resource utilization and energy recovery of GFS.