| With the rapid development of the cement industry in our country, the total amount of nitrogen oxides formed from the cement industry have become the third largest, besides the power plant and automobile. It has strongly influenced the quality of atmosphere and become the restriction factor of sustainable development of cement industry. Now, developing lowNOX technology and low NOX equipment have become the inexorable trend with strict NOXemission standards. Precalciner is a key equipment to implement the low NOx technology because it can achieve the goal of reducing NOX as well as carry out the decomposition of cement raw meal.Advance in NOX formation and control in the world was analyzed in this paper. It shows that a lot of foreign researchers paid more attention to theNOX control technology but less on mechanism of NOX formation, and the study on this field is not carried out nearly in our country. Therefore, the mechanism of NOX formation and the technology of staging combustion in the precalciner were further studied in current work with combination methods of theoretic analysis, simulated experiment, test in cement plant and CFD simulation. As the result, the technologies of staging combustion for precalciner were presented firstly to reduce theNOX from the cement industry, which have filled in blanks of this research field domestically. This thesis has carried on innovative research from the several following respects mainly:In this paper, the coals and chars from the cement plants were selected as research target. Their physics and chemical characteristics were investigated comprehensively by means of proximate analysis, ultimate analysis, specific surface analysis and X-ray photoelectron spectroscopy (XPS) analysis. The results indicate that the volatile content, carbon content, chemical composition and coal-N functional groups are strongly dependent on coal type.Mechanisms of NOX emission during coal combustion for precalciner were studied under various conditions in experimental bench scale precalciner. The results reveal that coal type, temperature, O2 concentration all have markedly effects on the formation of NOX, and the rate and amount ofNOX formation clearly rise in presence of cement raw meal, which suggests the cement raw meal has distinct catalytic effect on NOX formation. In addition, it should be noted that the cement raw meal also has the same catalytic effect on the reaction of the NOX-char.The staging combustion experiments were carried out to investigate the effects of the temperature in reducing area, excess air coefficient, residence time and raw meal in a one-dimension pulverized coal furnace for a wide range of coal rank. The regularity of NOX formation is obviously influenced by various combustion conditions. On the basis of staging combustion experiments mentioned above, the pilot-scale combustion tests were carried out to further determine the operating parameters. The tests show nitrogen oxides decrease 30% when the proportion of fuel is 50% and the proportion of air is 30% in reducing area.By building the models of gas flow, heat transfer, combustion, decomposition and NOX formation, the computer three-dimensional numerical simulation system for pollution formation in precalciner was used first to study the effects of the output, temperature of exhaust gas from rotary kiln, NOXcontent in exhaust gas from rotary kiln and temperature of tertiary air on NOX emission. The computer three-dimensional numerical simulation system has been proved reliable by comparing the calculating results with experimental results. The simulation results indicate that temperature of tertiary air has strong effect on NOX emission.In addition, In terms of the computer three-dimensional numerical simulation system for NOX formation in precalciner, air staging, fuel staging, simultaneous fuel and air staging were studied by comparing the values of targets (e.g. burn-out ratio, decomposition ratio and amount of NOX formation). The results show the amount of NOX formation during fuel stagi...
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