Mechanism Study On Cold Modeling Of Using Air Supplying To Alleviate Fouling And Slagging In The Gasification Waste Heat Boiler

Coal gasification technology is one of the main technologies for clean and efficient conversion of coal.It is the basis of integrated gasification combined cycle(IGCC)technology system and coal-based polygeneration system.The entrained-flow gasification technology has the characteristics of high efficiency,cleanliness and wide adaptability of coal.It is an important direction of the development of coal gasification nowadays.The entrained-flow gasifier device is composed of gasifier,radiation waste boiler and convection waste boiler.When the gasifier works,the gas enters the radiation waste boiler through the throat of the gasifier and exchanges heat through the inner water wall and the outer water wall.The high temperature air flow with ash from the gasifier has a certain amount of momentum,which will entrap the surrounding gas near the entrance of the radiation waste boiler,thus generating a negative pressure zone near the entrance(the negative pressure zone refers to the area where the pressure is slightly lower than that of the main gas flow).Under the influence of this pressure difference,the main gas flow deflects,causing the fly ash carried in the air flow to touch the inner water wall.If the fly ash is in a melting state,slagging will occur when the air flow deflects to hit the wall;if the fly ash has cooled,the air flow deflects to hit the wall and ash will accumulate.In order to solve this problem,this paper reduces the negative pressure inside the waste boiler by filling the air in the negative pressure zone,and reduces the deflection of air flow,so as to improve the phenomenon of fouling and slagging on the inner wall of the waste boiler.In this paper,the effect of different air supply quantity and different air supply modes on fouling and slagging of waste boiler was studied by cold modeling method.Firstly,the cold model experiment,load change experiment and improvement experiment were carried out to measure the particle adherence.The results show that the method of air supplying has a positive effect on reducing negative pressure and airflow deflection.The optimum filling air quantity in cold model experiment is 10% of the main airflow.After reaching the optimum filling air quantity,the effect of reducing negative pressure is not affected by the increase of filling air quantity.When the load decreases,the effect of filling air method is better,but when the load increases,the effect of slagging is greater,and the optimum filling air quantity is 16%.The results show that this method is suitable for the existing load and load reduction situations;when the air supply air flow is more uniform,i.e.it can cover the negative pressure area better,the effect of air supply on reducing negative pressure will be significantly improved,and the optimum air supply quantity in cold model experiment will be 3%.The effect of radial position of air supply hole on reducing negative pressure is not obvious,so air can be supplied according to the actual design requirements in practical application.Then,the airflow velocity and flow field are tested under selected working conditions,which confirms the above conclusions.