某电厂1000 MW机组双进双出钢球磨煤机出力低原因分析及优化改造

Analysis on the Reason of Low Output and Modification of Dual Inlet and Outlet Coal Mill of 1000 MW Boiler

双进双出钢球磨煤机在我国燃用无烟煤和贫煤的火力发电厂中被广泛使用。某电厂1000 MW机组双进双出钢球磨煤机长期存在出力低的问题,经过制粉系统各设备比较和分析,研究轴向分离器的设计规范,判断制粉系统出力低的原因主要为平锥式轴向煤粉分离器设计不合理。因全部更换分离器成本高,通过创新设计,改动分离器内部结构、优化流场来解决此问题。提出四种改动方案,利用CFD软件模拟流场、计算流速选择方案进行实验。循环倍率越低,分离器分离效果越弱,磨煤机出力越大,通过数值模拟优选出的最佳方案为延长风管的出口导流板,并在磨盘底部正对风管处添加圆锥导流。运行效果表明,所提改动方案大幅提高了磨煤机出力。实际改造表明,磨煤机出力大幅提高,创新改动后制粉系统出力达到了设计值。

Dual inlet and outlet coal mill is widely used in thermal power plants that burn anthracite and lean coal in China. The problem of low output of a 1 000 MW dual inlet and outlet coal mill in a power plant has been existed for a long time. Through comparison and analysis of each equipment in the pulverizing system, the design specification of axial separator has been studied. The main reason for the low output of pulverized coal system was the unreasonable design of the horizontal cone axial pulverized coal separator. Due to the high cost of completely replacing the separator, the problem could be solved by innovative design, changing the internal structure of the separator and optimizing the flow field. Four modification schemes were proposed, and CFD software was used to simulate the flow field and to calculate the selection of the flow rate. The lower the circulation ratio was,the weaker the separation effect of the separator was, and the greater the output of the coal mill was. The best scheme optimized by numerical simulation was to extend the outlet guide plate of the air duct, and add conical guide at the bottom of the grinding disc directly opposite the air duct. The actual verification has greatly increased the output of the coal mill. The actual transformation and verification showed that the output of the coal mill has been greatly improved and the output of the pulverizing system has reached the design value after innovation and modification.