| In recent years,because of the hazy weather,the national supervision requirements for flue gas pollutants have become increasingly stringent,then the sulfur dioxide emissions being one of the main control targets.At present,the flue gas desulfurization technology of coal-fired boilers in China is mainly based on the wet method which has the advantages such as high desulfurization efficiency and mature technology.However,the disadvantages are high operating cost,so it is mainly used in large-scale power plant boilers.Currently,due to the limited cost saving and technology of SMEs,etc.,the control of sulfur dioxide emitted by the medium-sized industrial boilers cannot be invested as much as large-scale power plants.Therefore,it's great significance on research and development of low investment,high efficiency,stable operation of flue gas purification technology for coal-fired industrial boilers.Based on this,the flue gas desulfurization technology of calcium-based desulfurizer in the pulverized coal industrial boiler was proposed,which uses the high desulfurization activity fly ash generated by the mild combustion of pulverized coal industrial boilers as a desulfurizing agent,and it is applied to the flue gas under conditions of humidification and high rate cycling.Sulfur dioxide in the gas is removed in the form of high Ca/S ratio,so as to achieve waste utilization purposes.In this paper,it's the first time to start the basic research on the production condition of calcium-based desulfurizer,optimized the design reactors and verified the industrial tests for the coal-fired industrial boiler ash-calcium circulating flue gas desulfurization technology.Firstly,the optimum conditions for the preparation of calcium-based desulfurizer were determined after the study of production conditions on the physical and chemical properties and desulfurization characteristics of fly ash using a drop tube furnace in the laboratory to simulate a pulverized coal industrial boiler.The reaction kinetics model was obtained after the research of kinetics of desulfurization reaction for calcium-based desulfurizer.The numerical simulation of the desulfurization reactor was carried out using computational fluid dynamics modeling software.The optimal design was proposed and the influence of the main factors affecting the desulfurization reaction on the desulfurization efficiency was studied.On the basis of the above,a fly ash circulation desulfurization industrial installation system with a processing capacity of 40000 Nm3/h pulverized coal industrial boiler was designed,debugging and operation were carried out to verify the desulfurization reaction model and the feasibility and reliability of the technology.It provides an effective design basis and operating experience for its industrial application.The research content and related results of this paper are as follows:?1?Effect of combustion conditions on physicochemical and desulfurization characteristics of fly ashDripper furnace test equipment was used to simulate the combustion process of a pulverized coal industrial boiler,combined with conventional characterization methods?scanning electron microscopy,particle size analyzer,X-ray diffractometer XRD,X-ray photoelectron spectrometer?,EDTA and The evaluation of the desulfurization activity to study the effect of combustion temperature,air classification,Ca/S ratio on the physical morphology,chemical composition,active calcium oxide content and desulfurization performance of the fly ash in the combustion conditions,so as to obtain the optimal operating conditions and get the high desulfurization activity of fly ash.Combustion temperature,air classification,and Ca/S ratio have a significant effect on sulfur combustion performance,chemical form,active calcium oxide content,and desulfurization activity of pulverized coal in the furnace.The effect on the microstructure of fly ash is temperature>Ca/S ratio>Air classification;Through the control of combustion can achieve the purpose of activating fly ash.The optimal operating conditions for the preparation of high-activity fly ash desulfurizer are:combustion temperature 800°C,secondary air ratio 95%,and Ca/S ratio 2.?2?Study on the kinetics of desulfurization.The desulfurization experiment was simulated by a fixed-bed bench experiment,and the activation energy and apparent frequency factor required for the desulfurization reaction of this experiment were calculated based on the experimental data.Theaccuracy of the model was verified by fitting the calculated and experimental values.The kinetic model for desulfurization of fly ash used in this experiment was established.The activation energy of high-activity fly ash flue gas desulfurization reaction was11.5655 kJ/mol,and the reaction kinetic equation was.????3?Numerical simulation of desulfurization reactor.The modeling,meshing,and numerical simulation of the desulfurization reactor were performed using computational fluid dynamics modeling software ICEM and general-purpose software Fluent.In view of the uneven distribution of the flow field in the original design reactor simulation results,an optimized design of the deflector was proposed.The results showed that the flow distribution of the optimized reactor was more uniform and the flow ability was more stable.At the same time,by analyzing the distribution of velocity field,turbulence intensity field and static pressure field in the reactor before and after optimization by cold simulation,the key factors of the stability of the flow field are analyzed to provide guidance for the design of the desulfurization reactor;The influence factors of desulfurization efficiency,such as adiabatic saturation degree,humidifying water content,Ca/S,were studied through hot simulation.The result shows that the temperature difference of adiabatic saturation of steam,the amount of humidified water,the Ca/S,and the solid-gas ratio have a significant effect on the desulfurization efficiency.With the reduction of AAST,the desulfurization efficiency is significantly increased;the increase in the amount of humidification water,Ca/S,and solid-gas ratio will increase the desulfurization efficiency,providing a theoretical basis for the determination of the actual desulfurization reaction operating conditions and the precise selection of system equipment.?4?Research on fly ash desulfurization.According to the laboratory basic research results and technical requirements,the first set of industrial boiler ash circulation and desulfurization industrial plant with a processing capacity of 40000 Nm3/h was designed,constructed,commissioned and operated.The influences of main parameters,such as the adiabatic saturation temperature difference,humidification water flow,Ca/S,flue gas flow,and solid-gas ratio,on the desulfurization efficiency were studied.The running test results show that the device stable operates conditions are:the reactor temperature is about 65°C and the pressure is about 600 Pa.SO2 can be effectively removed,the desulfurization efficiency is over 90%,and the operating cost is low.Ca/S is only 0.9.Flue gas near adiabatic saturation temperature difference,humidification water,Ca/S,solid-gas ratio has a significant effect on desulfurization efficiency.As AAST decreases,the desulfurization efficiency increases significantly.The increase in humidification water,Ca/S,and solid-gas ratio will increase the desulfurization efficiency.Under the premise of stable operation of the system,the optimal operating conditions are:coal with less than 0.5%sulfur content,and flue gas flow range of 30000 to 40000 Nm3/h,AAS is approximately13°C,the humidifying water flow is approximately 1500 kg/h,the Ca/S ratio is approximately 0.9,and the solid-gas ratio is approximately 2.6,verified the results of numerical simulation and bench test. |
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