Research On Integrated Control Technology Of Eliminating White Smoke Plume In Coal-fired

In the process of retrofitting coal-fired power plant units,as more than 90% of the plants adopt wet desulfurization technology,the desulfurization slurry,while removing sulfide from flue gas and reducing flue gas temperature,also makes the flue gas humidity become nearly saturated.A large amount of flue gas with near-saturated humidity is discharged directly into the surrounding environment through the stack without further treatment,causing some new environmental problems,such as white plume and gypsum rain.The white plume is not only a visual pollution,but the harmful substances contained in the flue gas also seriously endanger the health of the surrounding residents.In addition,the plume contains a lot of heat,which causes energy waste.Therefore,eliminating the white plume not only protects the environment,but also has great significance in improving energy efficiency.The key to plume whitening is to keep the flue gas temperature at the exit of the stack within a reasonable range.At present,the research on the whitening of smoke plume mainly focuses on the design of whitening process,the selection of process material and the design of key components.There are relatively few studies on the overall control of the plume whitening system,and even fewer studies on the control methods of the plume whitening system under the unavoidable non-Gaussian stochastic perturbations such as flue gas mass flow rate and heat source temperature.Therefore,based on non-Gaussian stochastic control theory,the control problem of the plume whitening system under non-Gaussian disturbances is solved in this paper.The main work is listed as follows.Firstly,the mechanism of white plume generation and elimination is analyed.The advantages and shortcomings of the routes of flue gas whitening,flue gas condensation and heating methods at the present stage are briefly introduced and summarized.Taking a coal-fired power plant in Shanxi as the research object,a water-mediated gas-gas heat exchanger(MGGH)+ condenser white-out system is established by the method of flue gas condensation and reheating.Then,the mathematical model of the white plume elimination control system is established according to the thermal theorems such as energy conservation.Based on non-Gaussian stochastic control theory,the minimum rational entropy(MRE)criterion is proposed and the MRE series controller is designed.The MRE based control algorithm is applied to the main regulator of the plume white-out flue gas temperature control system to make the flue gas reheater outlet discharge temperature consistent with the set value,so as to achieve the purpose of eliminating white plume.In addition,a single-neuron string controller design method based on Survival Information Potential(SIP)is proposed.And a new control optimization criterion is constructed by considering both the tracking error and the stochasticity of the control input.The cascade control structure is adopted,and the secondary loop is a PID controller.The main loop selects a SIP single neuron controller with low computational consumption and simple structure,and uses the stochastic gradient method to design the optimal control law of the plume elimination system.The simulation results show that the proposed control law finally makes the tracking error probability density function of the plume elimination control system present a sharp and narrow shape near zero,indicating that the exhaust temperature is kept near the set value with a small randomness,which satisfies Conditions for the elimination of white plume.In summary,this paper proposes two cascade control methods,minimum rational entropy and SIP,for the plume whitening system under non-Gaussian disturbances,and the simulation results show that the proposed control strategy can effectively suppress the influence of random disturbances and make the final exhaust temperature reach the set value,so as to eliminate the white plume.The control strategy proposed in this paper is of theoretical significance and practical value for protecting the environment and saving energy.