Numerical Simulation of Coal Combustion in a1000MW Ultra-Supercritical Opposed Swirling Fired Utility Boiler
|School||Huazhong University of Science and Technology|
|Course||Thermal Power Engineering|
|Keywords||ultra-supercritical opposed swirling fired utility boiler combustion of coal blends NO_x numerical simulation|
Ultra-supercritical coal-fired power generation technology is mature and advanced. Ithas been widely employed in commercial large-scale power plants. With the technologies,high efficiency and low pollution emission combustion of pulverized-coal can successfullyimplemented by installing desulfurization, denitrification and high effective dust removalequipments at the end of boilers. Therefore, ultra-supercritical coal-fired power generationtechnology becomes the quite perfect clean power generation technology. Due to thehistory of ultra-supercritical thermal power unit in China is really short, there still existsome problems in the operation process. Coal blends combustion technology has beenwidely used in China, but the problems such as fluctuation on service、boiler efficiencyreduction、slagging seriously caused by irrational blended is frequently happened. It isnecessary to carry out more research to solve and improve the problems. This paper carriedout coal blended combustion numerical simulation researches on a1000MWultra-supercritical pulverized-coal opposed swirling combustion utility boiler. This workhas some theoretical importance and application value in engineering.Firstly, taking consideration of the actual structure and size of HT-NR3burner, a newmeshing method was put forward to integrate the furnace and48burners as a wholecompute field. Taking into account the45degree angle of expansion flow cone and the wall,this paper adopted a meshing method keeping grid line at the burner outlet consistent withthe flow direction, to reduce the influence on the calculation accuracy of the false diffusionphenomenon. Based on the meshing method, the characteristics of the flow, combustion,heat transfer and NO_x emission were numerical simulated for a1000MWultra-supercritical pulverized-coal opposed swirling combustion utility boiler under ratedload. The calculated results agree well with the experimental values.Secondly, multi-case numerical simulations were conducted to study the effects ofswirl intensity, quality of OFA, boiler load and different operational modes of mills inservice on the characteristics of the flow, combustion and NO_x emission for the boiler. Theresults show that increasing boiler swirl intensity，five mills of A, B, C, D, E in service canincrease the burnout ratio and combustion efficiency, also decrease the NO_x emission. Byincreasing the quality of OFA and decreasing the load appropriately, the NO_x emission can be effectively reduced.Finally, numerical simulations for combustion of blended Indonesia coal were alsocarried out. The results indicate that the combustion efficiency decreases, fly ash carboncontent increases and NO_x emission reduces by blending Indonesia coal under rated load.Besides, combustion of Indonesia coal blended in the upper furnace is better than that in thelower furnace. Therefore, Indonesia coal can be blended with designed coal ensuring thesafe and stable operation of the unit. During combustion of coal blends, high volatile coalshould be burnt in the upper furnace to increase the combustion efficiency and reduce theNO_x emission.