Numerical Simulation Of Drag Reduction In 200MW DACCU Bag Filter System

Bag filter is one of the most common and efficient equipment to reduce dust emission in thermal power plants.In a self provided power plant,2# direct air cooled coal-fired units(DACCU)are difficult to meet the dust emission standard due to the use of electrostatic precipitator,so the bag filter is added afterwards to form the "electric + bag" dust removal system with Z-shaped flue.During operation,limited by technical conditions and site layout,the overall resistance of the system is far more than 1700 Pa,which seriously affects the safe and economic operation of the unit.Aiming at the problem that the resistance of bag filter system is too large,the field test is carried out.It is preliminarily determined that the reasons for the excessive resistance are the excessive local resistance loss in the bag filter system and the filter bag blockage.Combined with the measured data,the 1:1 physical model of the bag filter system is established by using Solid Works,and the numerical simulation is carried out by importing fluent to verify the rationality of the numerical simulation method.Therefore,in order to reduce the overall resistance of the bag filter system,the main transformation idea of changing the bag filter from the lower air inlet to the side air inlet,adding different numbers of guide plates and flue gas distribution plates in the Z-shaped flue is proposed,and three sets of improvement schemes are proposed for the internal filter bag layout,namely: Scheme 1,the filter bags in the third dedusting chamber are arranged in sequence;Scheme 2,the filter bags in the third dedusting chamber are arranged in fan shape;Scheme 3,the filter bags in the third and fourth dedusting chambers are arranged in fan shape.The simulation results show that: 1)the resistance of the bag filter system with side air inlet can be reduced partially;the resistance of the Z-shaped flue can be further reduced by installing a deflector and a flue gas distribution plate.2)At BMCR point,the drag reduction ratio between the inlet and outlet of the bag filter system reaches47.2%,34.31% and 45.79% respectively.3)Adding a deflector and a flue gas distribution plate in the Z-shaped flue,and arranging the filter bags in the third dedusting chamber in the way of side air inlet,the overall resistance of the dedusting system is the lowest,which is the optimal transformation scheme.According to the optimal transformation scheme,the economic analysis is carried out by using the power consumption analysis method and the total benefit present value method respectively,and the resistance and carbon emission are calculated.The results show that the retrofit scheme of bag filter system is feasible.On the basis of greatly improving the safe and economic operation performance of the unit,460 tons of carbon emission can be reduced every year.It can provide reference for the transformation of the same type of units.