Research And Application On The Low-NO_x Combustion Of 130t/h CFB Boiler

China is the biggest country of coal consumption in the world,coal consumption promotes Chinese economic development,but simultaneously brings serious environmental pollution problems,especially the nitrogen oxides.The latest emission standard of air pollutants for thermal power plants is unveiled by state in 2011,then the ultra-low emission requirements for coal-fired utility is put forward,the emission of nitrogen oxides concentration in coal-fired utility should be controlled strictly within 50 mg/Nm3 in key areas.Compared with the pulverized coal combustion technology,circulating fluidized bed combustion technology has excellent environmental protection performance.With the help of reasonable low-NO_x combustion technologies and SNCR denitration technology,the emission concentration of nitrogen oxides in circulating fluidized bed boilers can meet the requirements of ultra-low emission.Firstly,a 130t/h circulating fluidized bed boiler is used as the model to simulate the gas-solid two-phase flow and the coal combustion process in the circulating fluidized bed boiler by using the software of Fluent.The flow field,temperature field and gas components concentration field are obtained to verify the correctness of the simulation model by comparing with engineering test data.Then,the low-NO_x combustion technology of 130t/h circulating fluidized bed boilers which includes adjusting the secondary air system,increasing heating surface,increasing the flue gas recirculation system and improving SNCR system etc,is obtained through the literature summary and thermodynamic design.Compare the flow field,temperature field and gas components concentration field before and after the low-NO_x combustion optimization of 130t/h circulating fluidized bed boiler by computational simulation,analyzing the effect of low-NO_x combustion optimization scheme to the boiler combustion temperature,the gas components concentration and the generation of nitrogen oxides.The feasibility of the low-NO_x combustion optimization scheme of the circulating fluidized bed boilers is proved.Finally,the low-NO_x combustion optimization scheme of 130t/h circulating fluidized bed boilers is applied in the 5#CFB boiler of Hangzhou United Thermoelectric co.,LTD.The results show:at rated load,the final concentration of NO_x emissions decreases from 100mg/Nm3 to less than 50mg/Nm3,the main steam temperature meets the design temperature by increasing 20?,the bed temperature and furnace outlet temperature have dropped 50 ?,the amount of ammonia slip which can be controlled within 8 mg/Nm3 has a slight increase,the boiler efficiency is almost invariant.Further optimization test has been used to solve the problem of high CO concentration after the air pre-heater.In order to optimize the boiler operation,different amount of flue gas recirculation should be chosen at different load,simultaneously the upper secondary air damper opening degree should be 100%,the lower secondary air damper opening degree should be distributed like that the middle is large and the both sides are small.