| In a coal-domained power generation energy structure in China, controlling the formation of NOx during combustion process shows a great significance to environment protection and sustainable development. Among various technological means to reduce the discharge of NOx, SCR(Selective Catalytic Reduction) is the most mature and widely used technology. But the SCR equipment can’t be used under a temperature lower than 300℃, which makes lots of coal-fired power plants have to tackle with the problem that the denitrification system can not be put into use under a low unit-load. And that makes the discharge of NOx out of control in a long time which makes environment pollution, and the enterprises have to face a serious pressure of environment policy. Nowadays, lots of specialists, scholars and engineers begin to discuss how to improve the commissioning-capability of SCR device under low-load condition, and many technological means are proposed. The direct aim of these means is to rise the in-let fuel gas temperature of SCR under low-load condition.This paper compared the technological possibility, safety, reliability and economy of economizer with water-bypass plan, economizer with forced-recycling plan and split-economizer plan based on thermodynamic calculation according to the actual situation of a 600MW supercritical once through boiler in a firepower electricity generating enterprise in Guangdong province. The result shows that split-economizer plan can not only extend the the commissioning-capability of SCR device under low-load condition, but also have good efficiency and reliability. So an actual project is put into practice with this plan. The data of operating and efficiency experiment after the transformation shows that the SCR system can be used when the unit load is above 220MW. This fits the expectation well and creates a considerable social and financial benefit.The research and implementation of this project provides a very good sample to similar units in China to make a technical transformation of the same kind, and is valuable to be generalized and referenced. |
