Study On Pulse Back Blowing System Of Ceramic Filter

Pulse backblowing system is one of the key components of ceramic filter.The performance of pulse backblowing system is directly related to the dust removal effect and stable operation of the dust collector.At present,the methods to improve the performance of the pulse backblowing system include increasing the backblowing pressure,prolonging the backblowing time and increasing the size of the nozzle,etc.Although these methods can improve the effect of the backblowing to a certain extent,they will increase the consumption of backblowing gas and lead to the increase of the operation cost of the dust collector.Nozzle and ejector are the key components of pulse backblowing system,which have great influence on the flow characteristics and energy conversion of backblowing air.The current commonly used pulse inverse blow soot cleaning nozzle ejected by the airflow speed limit,according to the principle of fluid expansion growth,no matter how to increase the back pressure,the internal air velocity are unable to reach or exceed the speed of sound,and blow air velocity is the important factors that affect the pulse counter blowing effect,which makes the pulse counter blowing effect is limited greatly improve.The supersonic nozzle can accelerate the subsonic flow to supersonic speed without increasing the backblowing pressure,and improve the effect of pulse backblowing effectively without consuming more backblowing gas.Therefore,this paper introduces the laval nozzle,a supersonic nozzle commonly used in aerospace and plasma spraying fields,and uses response surface method to explore the optimal structure parameters of laval nozzle.Through coupling experiments of laval nozzle and ejector,the influence of structural parameters and operating parameters on the ejection coefficient of pulse back blowing was studied.The influence of different types of nozzles,backblowing height and backblowing pressure on the deashing effect of ceramic filter elements was studied by changing pulse backblowing conditions.The specific research work is as follows:(1)In this paper,the structural size range of the new Laval nozzle is calculated based on the one-dimensional steady isentropical flow theory with variable cross section.The profile design of the taper section,throat section and the taper section of the Laval nozzle is optimized by the quintic curve profile.Then the optimal structural parameters of the Laval nozzle are optimized by the response surface method.The inlet diameter is 13 mm,the throat diameter is 8 mm,the outlet diameter is 12 mm and the extended section length is 10 mm,and the comparison with the selected reference nozzle is made.The results show that the outlet velocity is increased by 17.49% and the mass flow rate is increased by 1.04%.It can be seen that the optimized nozzle structure has been significantly improved in jet performance.(2)Through the method of numerical simulation,this paper studies the pulse blowback system composed of Laval nozzle and ejector,and finds that the ejector throat size has a significant influence on the ejector coefficient.The coefficient of ejection can be effectively improved by increasing the throat diameter of ejector,while the ratio of the throat length of ejector to the throat diameter of Laval nozzle should not exceed 5.0.The diameter of the reduced section of the ejector should not be too large,and the optimum diameter ratio between the diameter of the reduced section and the diameter of the laval nozzle throat is about 7.5.The diameter of the expansion section of the ejector should not be too large,and the ratio between the diameter of the expansion section and the diameter of the laval nozzle throat should be avoided between 9.0 and10.0.(3)Aiming at the problem that the best pulse backblowing condition of ceramic filter equipment in laboratory is not determined.This paper choose the convergent nozzle and the optimized laval nozzle,compared by the method of numerical simulation and field experiment analysis found that using pulse inverse blow soot cleaning of laval nozzle,although the peak pressure in the filter at the top of wall is lower than straight pipe nozzle and the convergent nozzle,but starting from the filter in the middle of the wall peak pressure than convergent nozzle,The peak pressure on the side wall at the bottom of the filter element is 637 Pa higher than that of the tapering nozzle,and the recovery rate of the flux of the filter element by a single pulse backblowing reaches97.49%.It can be seen that the effect of laval nozzle backblowing air on the filter element is much more uniform,and the cleaning effect is better;Through the study of different backblowing height,it is concluded that when the backblowing height is 80 mm,the amount of gas injected by the pulse backblowing air reaches the maximum,the ejector ratio reaches 1.68,the peak pressure of the side wall of the filter element is2057.16 Pa,and the effect of the pulse backblowing is the best.It is found that when the backblowing pressure is 0.3mpa,the peak pressure of each side wall of the filter element exceeds the critical average cleaning pressure of 500-600 Pa,and the gas consumption is relatively small.In this paper,the laval nozzle is applied to the pulse back blowing system of ceramic filter,the structural parameters of laval nozzle are optimized by response surface method,and the optimal structural parameters of the nozzle are obtained.In the simulation experiment of pulse backblowing system composed of laval nozzle and ejector,the influence of backblowing condition on ejection coefficient is studied.In addition,this paper studies the back blowing condition of the existing dust removal equipment in the laboratory,and obtains the best pulse back blowing condition of the equipment,and shows that laval nozzle has great application potential in the pulse back blowing dust cleaning.