Chongqing city, which is located in the southwest of China, suffers from acid rain damage caused by SO2 in coal combustion gas. Particularly, stoker type boilers in medium and small factories have no emission control facility in spite of using coal with high sulfur content (3-5%), so that a suitable countermeasure is required in angles of the cost, technological level and social conditions.
We proposed a coal briquette combustion with the additive of limestone or slaked lime as one of the countermeasure. The possibility of coal briquette combustion methods was examined experimentally and compared with other methods from points of view of the cost and energy saving effect. The desulfurization rate of 70% was obtained in the briquette combustion method with the additive of limestone and 80% for slaked lime. Most of sulfur in the coal (both organic and pyritic) was trapped as gypsum anhydride (CaSO4). The desulfurization rate slightly depended on initial oxygen concentration in the supplied gas and size of limestone, while it was not influenced by briquetting pressure.
The desulfurization cost of coal briquette was calculated as 20-30% of semi-dry or fluidized bed process. The briquette combustion method was expected to be effective in improving the human health and forest conservation in Chongqing city.
