| Coal is dominant in our country’s energy resources. However, mass use of coal, and comparatively low efficient production and consumption have created enormous pressure on the ecological environment. The combustion of coal can cause air pollutant of dust and sulfur dioxide, therefore may lead to acid rain and other disasters and endanger the ecological environment. Use of industrial waste slag-carbide slag as sulfur-fixing agent can achieve the aim of waste control by waste. Experimental studies have been carried out in this thesis on the sulfur-retention during coal combustion and effect on coal calorific value and combustion characteristics, studies on suitable proportion and promoting effect of effective sulfur-fixing additives during carbide slag and coal-blended combustion have also been conducted. The trend of change in coal calorific value and coal combustion characteristics are investigated according to the sulfur-fixing condition. The use of carbide slag as sulfur-fixing agent, not only has good sulfur-fixing effect, but also improve the coal calorific value. It is of great significance and has broad development prospect in our country from the aspects of economic and environmental protection.In this paper, automatic sulfur analyzer along with coulometer was used to determine the sulfur content released from flue gas during coal combustion and then the sulfur-fixing rate was calculated according to the sulfur total content and the sulfur emission content. Firstly, the influence of burning temperature, duration, ventilation volume and mole ratio of calcium to sulfur on sulfur retention efficiency of carbide slag were investigated. The optimum proportion of calcium-based sulfur-fixing agent was then determined. Based on the optimization of sulfur-fixing conditions, the effect from unitary, binary and ternary complex additives on the sulfur-retention during coal combustion was studied respectively at the temperature of1100℃. Lastly, the applications of combing carbide slag and other industrial waste slag to measure the effect on the sulfur-retention during coal combustion was investigated by mixing waste slags with sulfur-fixed additives according to a certain proportion.The results suggest that when burning temperature is1100℃, with duration of5min, ventilation volume of1.2L/min, Ca/S mol ratio of2.4, carbide slag-CaCO3compound sulfur-fixing agent mixed by the mass ratio of3:2as the main sulfur-fixing agent, the maximum value of sulfur-retention efficiency is obtained. The effect of sulfur-retention slightly increased by the addition of the selected sulfur-fixing additives, such as K2CO3, Al2O3, Na2CO3, MgO, Fe2O3, ZnO, KMnO4, SiO2, CeO2, NaCl. In the binary complex additives experiment, the effect of sulfur-retention of binary complex additives was better than that of one-component additive. When K2CO3mixed respectively with MgO and Na2CO3in the molar ratio of5.0; Al2O3mixed with SiO2in the molar ratio of5.0, with ZnO in the molar ratio of1.0; SiO2mixed ZnO in the molar ratio of3.0, mixed MgO in the molar ratio of0.2, the ratio of sulfur-retention was better. In the ternary complex additives experiment, when the mixtures of K2CO3, MgO and Na2CO3is in the molar ratio of5:1:1, Al2O3, SiO2and ZnO mixed in the molar ratio of1:3:1, and SiO2, MgO and ZnO mixed in the molar ratio of3:15:1, the maximum value of sulfur-retention efficiencies are38.1%,38.4%,40.9%respectively. In the experiment on the sulfur-retention effect of carbide slag blended with high-sulfur coal during combustion, the sulfur-retention rate was56.9%when K2CO3-Al2O3-Fe2O3mixed in the molar ratio of10:5:1. In the experiment on using industrial waste slag as sulfur-fixing additive, the effect of black liquor was the best where the sulfur-fixing rate was28.5%among all the one-component sulfur-fixing additives; When the black liquor and Al2O3mixed in the mass ratio of0.5, the sulfur-retention rate was35.3%; When K2CO3, MgO and black liquor mixed as complex additives, the sulfur-retention rate was39.7%. Parts of sulfur retention productions were characterized by XRD and the mechanism of promotion to the sulfur-retention reaction of additive are discussed.Automatic heat measuring apparatus was used to investigate the effect of the additives on coal calorific value. The coal with different sulfur-fixing additives was analyzed by TG-DTG-DSC technologies. The results indicate that addition of the majority of sulfur-fixing agent and additives can enhance the combustion characteristics of coal, reduce the igniting temperature, and therefore increase the enthalpy change value of the coal combustion reaction and coal calorific value. |
PDF Full Text Request