Cost-effective desulfurization technologies are urgently needed to control sulfur dioxide emissions from coal-fired boilers in countries heavily relying on coal as energy. Full-scale desulfurization process during combustion in boilers was investigated to develop a cost-effective desulfurization technology to control sulfur dioxide pollution from combustion of coal with high content of sulfur. A grate boiler system with steam capacity of 20 t/h in a factory was applied to conduct the research. The desulfurization agent applied is mainly composed of a solid waste of limestone. Blank test when no desulfurization agent was added was applied to determine the sulfur removal efficiency by the desulfurization in the combustion process. Important operation factors affecting desulfurization efficiency were investigated which included the particle size of the desulfurization agent and the mass ratio of the desulfurization agent to the feed coal. Results showed that the desulfurization efficiency increased with the decrease of the particle size, and with the increase of the mass ratio within the investigation range. When 10 % of the desulfurization agent was mixed with the feed coal, the effluent concentration of sulfur dioxide in the fiue gas at the boiler outlet was about 3460 mg per cubic meter. Compared with the effluent concentration in a blank test, 49.5 % of the sulfur in the fiue gas was removed by adding the desulfurization agent. There was not any apparent difference in the steam output per unit time between the combustion of the coal only and the mixture of the coal and the desulfurization agent. Accompanied by an additional scrubbing desulfurization process, the sulfur dioxide concentration in the flue gas was within the limit of permitted level. Practical operation has proved that this process is cost-effective to control fiue gas pollution from middle-small-sized coal-fired boilers burning coals with a high content of sulfur.
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