Research On Switching Of Operation Mode In A 35MW Oxy-fuel Combustion Coal-fired Power Plant Boiler

With the increasingly serious environmental problems,such as the greenhouse effect,smog&haze and so on,it is urgent to optimize the energy structure and develop clean and efficient coal burning technology.Compared with other Carbon Capture and Storage?CCS?technology,oxy-fuel combustion technology due to the technical compatibility,lower operation cost and other advantages,is considered as the most feasible technical means to solve the coal-fired boiler air pollutant generation and reduce the emission of greenhouse gases?GHG?such as CO₂.This paper is based on the differences of the principles and technological process between traditional air and oxy-fuel combustion in the 35WM_th Oxy-fuel Combustion Demonstration Project,designed an air-fuel combustion/oxy-fuel combustion switch control system,put forward a corresponding control strategy for combustion mode transition and furnace pressure adjustment,and established a set of dynamic models based on the field test data.Under the premise of ensure the safety,stability and economy of the unit,the air-fuel combustion/oxy-fuel combustion switch control system should meet the needs of load regulation,and coordinate control the Air Distribution System and the Air Separation System?ASU?.Maintain the full combustion of pulverized coal,primary air flow and oxygen concentration stability,furnace pressure stable,by adjusting the oxygen injection from ASU,the amount of air flow into the furnace and recirculation flue gas amount,which can guarantee the system smooth switch from the air combustion to oxy-fuel combustion mode.The switching control system includes 3 subsystems,namely the Furnace Pressure Control System,Load Control System,Recirculation Ratio-Oxygen Concentration Regulation System,the last one is the core of the switch control system.Based on the pilot-scale oxy-fuel combustion test platform,it has successfully completed a number of full process experiments,stable switch combustion mode from air-fuel to oxy-fuel combustion.Under the oxy-fuel condition,the furnace chamber pressure is gradually adjusted from negative to micro-positive pressure,and finally achieved the stable oxy-fuel combustion under the micro-positive pressure.Chosen data from one experiment,which last a long time and the boundaries among of different combustion conditions are well-defined during switching operation,including 39 important data of 5 types operating parameters for analysis,cover valve opening,temperature,pressure,flow rate and gas composition and so on.In addition,the influence of the flue gas recirculation rate?and the O2 concentration in inlet stream?_2O on the combustion of pulverized coal and the CO2in flue gas is also discussed,some conclusions:when?and?_2O in the range of 0.6⁰.7 and29.5%³0.5%respectively,it is more conducive the enrichment of CO₂ in the flue gas.Lower?_2O can lead the coal powder burnout to worse;when?_2O be too high,the excess oxygen will dilute the CO₂ in flue gas.