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Research and Numerical Simulation on Coal Blends High Efficiency and Low NO_x Combustion in the Calc

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Tutor: XuShunSheng
School: Xiangtan University
Course: Chemical Process Equipment
Keywords: coal blends,NO_x,precalciner,numerical simulation,high efficientcombustion
CLC: TK16
Type: Master's thesis
Year:  2013
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Abstract:
With the rapid development of China¡¯s cement industry, the demand for coalresources becomes greater and greater, especially for high-quality bituminous coal.However, the storage of bituminous coal becomes less and less. As low volatileanthracite demands high ignition temperature and is difficult to burn out, this will leadto various problems for the anthracite combustion in the calciner. Study oncombustion of anthracite mixing a certain amount of bituminous coal in the calcinerbegan in the1990s. Through the test of blending with anthracite done by productionenterprises, the demand for high-quality bituminous coal sharply reduced, whicheased the contradictions of the industrial development needs and the scarcity ofresources.For a long time, the NO_xemissions of coal-fired calciner have been the focus ofattention. In the entire precalciner kiln system£¬the amount of coal in the calcineraccounts for more than60%of the entire system, thus the control of NO_xis mainlyconcentrated on the calciner. In order to solve the problem of the shortage of coalresources and the control of the NO_xemission, study on mixed coal combustion incalciner is very important. Using coal blends combustion technology well, can notonly brings a positive influence on the coal-fired equipment operating performance,but also suppresses the generation of NO_xto some extent.In this paper regarded the Trinal-sprayed Calciner (TTF) as the research object,the combustion of the mixed coal was numerical simulation researched. The mainconclusions are as follows£º(1) Using the selected mathematical model needed in the simulation study tocarry out the numerical simulation of the actual conditions in TTF calciner. Comparedwith the measured data, the reliability of numerical simulation methods andmathematical models used in the paper is validated(2) In different tertiary air velocities, the temperature distribution in the calcinercan basically meet the actual needs of the production. From the changing trend of thetemperature contours, the average temperature in the calciner, the combustion rate andburnout rate of coke, and component field, we can know that the best tertiary airvelocity is26m/s. For mixed coal combustion under different flue gas velocities inkiln tail, when the flue gas velocity is27m/s the combustion zone of pulverized coalin the calciner is largest and the overall temperature is highest, and the burnout rate of coke is close to the rate under the velocity of25m/s but is higher than the otherconditions. So the best flue gas velocity in kiln tail is27m/s when the tertiary airvelocity is26m/s. The combustion numerical simulations for mixed coal in differentproportions show that the burning situation is basically well. With the proportion ofanthracite in mixed coal increasing, the combustion characteristics of mixed coal willdeteriorate.(3) With the tertiary air velocities increasing, the NO concentration of pre-calciner outlet also increases. With the flue gas velocities increasing, at first, the NOconcentration of precalciner outlet increases,and then decreases. when the flue gasvelocity is25m/s, the highest concentration of NO is482.3ppm.With the amount ofanthracite increasing,the emissions of NO decreases.The numerical simulation results provide an important theoretical basis for theuse of mixed coal in calciner, and also provide a reference for the optimization controlof thermal parameters when mixed coals are used in the calciner.
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