SCR High Efficiency Denitration Research And Design Of Gas Steam Combined Cycle Unit

Gas-steam combined cycle unit is an efficient,clean,compact and relatively low-cost power production system.In western countries,related industries have been widely developed and applied,not only in the field of electric power,including mechanical power,heating and water supply,but also in the field of application.China has also adopted relevant national key projects to vigorously promote the development of gas turbine waste heat boiler system equipment.However,in recent years,more stringent NOx emission laws and regulations put forward new requirements for controlling NOx emission of gas steam combined cycle units.SCR denitration is a mature emission control technology.Its application in gas steam combined cycle unit can make the system adapt to more and more stringent emission standards,which is a more feasible control scheme.In order to better understand the SCR denitrification process of gas-steam combined cycle unit,it is necessary to study the reaction principle,flow field optimization,process route design and other aspects in the process,so as to make guidance and planning for its application in the follow-up industrial practice.The reaction principle of SCR denitrification is mainly carried out from two aspects,that is,urea pyrolysis to produce ammonia and catalytic reduction reaction.Through the simulation and experiment of urea pyrolysis to produce ammonia,we know that the pyrolysis of urea solution goes through three steps:droplet evaporation,urea particles become molten state,and finally urea particles pyrolysis completely under high temperature.The pyrolysis of urea is greatly affected by temperature and residence time.In this paper,the simulation of urea pyrolysis was carried out and verified with the experimental data.However,the catalytic reduction reaction is mainly affected by temperature,residence time,ammonia nitrogen ratio,water vapor and oxygen concentration.In this paper,the simulation of these factors is carried out,and the influence of these factors on the denitration Process Design of gas turbine waste heat boiler is analyzed.For the flow field optimization in SCR denitrification process of gas-steam combined cycle unit,this paper uses FLUENT software to simulate ammonia direct injection process and urea direct injection process,and compares them.It is found that the layout of ammonia injection grid can obtain a relatively more uniform mixing field,and the requirement for the overall flow field uniformity of gas turbine is lower than that of urea direct injection.However,the direct injection of urea requires higher self-mixing of gas flow field and more strict uniformity of flow field.Due to the rotating speed of gas turbine flue gas flow field,guide plate should be installed in both processes to guide the flow field,so as to obtain more uniform mixing field.If necessary,rectifying device and mixer should be installed to improve the mixing of reducing agent and flue gas.For the process design of SCR denitrification of gas-steam combined cycle unit,the design software is compiled by VB.Combined with the reaction principle and flow field optimization of SCR denitrification,the two processes of ammonia direct injection and urea direct injection are designed.The design software can play a guiding role in the practical application of SCR denitrification,including the structure design of catalyst layer,the consumption calculation of urea or ammonia,and the layout of ammonia injection grid and urea spray gun.