Simulation Studies Of Biomass/Coal Co-firing Ash Interaction In ESP

At the present,China is facing with dual challenge of environmental pollution and energy crisis.Therefore,new energy development partly instead of coal is one of important direction of China energy optimization reformation.China is the agricultural country,biomass energy as a clean,rich and renewable energy can partly replace coal.Meanwhile due to the fine particulate matter by coal firing too much emission to the atmosphere,causing a serious problem such as fog.Fine particle emission produce a great threat to human survival environment.So research fine particulate matter interaction of biomass/coal co-combustion ashes in the electric dust catcher to achieve the particle reduction is indispensable.This is significant for coal-fired power plants to develop new energy,and can it is substituted to seek the best biomass energy replacing coal.The biomass(corn stalk)and anthracite coal two kinds of fuels were selected in this paper to research.First,the corn stalk fuel was broken into fine particles and mixed with anthracite coal according to biomass proportion of 0,10%,15%,20%,100%,and formed a series of ashes by co-combustion.First through the experiment of physical and chemical characteristics of mixed burning ash(true density,particle size distribution),so on had made preparation for subsequent mixed burning ash interaction in ESP.The experimental results shown that as the corn stalk co-combustion ratio increasing,the true density of co-combustion ashes showed a trend of gradual decline.Meanwhile with the co-combustion of corn stalk and anthracite coal,made its particle size distribution had made some changes compared with pure anthracite coal ash or pure corn stalk ash,but the change was not obvious,the peak of particle size distribution was the same or nearly.This paper mainly discussed the internal mechanism of three kinds of aggregation interaction mechanism in ESP(thermal aggregation,turbulence aggregation,electricity aggregation).turbulence is simulated research,first of all,the three aggregation kernel functions were determined according to the particle size under different aggregation mechanisms.Known by three kinds of aggregation functions,the thermal aggregation effect was related to the two particle size,the greater the particle size difference,the greater the thermal aggregation function,and the effect of sub-micron particles is better than micro particles under thermal aggregation.The turbulence effect was related to the particle size,the bigger the particle size,the better turbulence aggregation effect,and micron particles coalescence effect was better than that of sub-micron particles under turbulence aggregation.Electricity aggregation effect was related to particle size,the bigger particle size,the greater the particle charge capacity,leading to the more obvious electricity effect,electric coalescence effect is obvious for micron and sub-micronparticles.After determined the aggregation kernel function,the aggregation interaction simulation of co-combustion corn stalk/anthracite coal ashes in ESP was studied by Fluent software.First of all,the different aggregation kernel function were brought into the user defined function(UDF)into Fluent,and then the particle balance model(PBM)and eule-euler double fluid model were used,adopting Sectional partition algorithm to solve.The results shown that when the flow velocity was 1.0 m/s and the particle volume fraction was 1.4%,the thermal aggregation effect is best.And the corn stalk/anthracite coal co-combustion ratio was 10%,the thermal aggregation effect is optimal.When the flow velocity of 1.5 m/s and the particle volume fraction was 1.4%,the turbulence aggregation effect was best.When the flow velocity of 1.0m/s and the particle volume fraction is 1.4%,the electricity together effect was best.While the biomass/anthracite coal co-combustion ratio was 10%,the electricity aggregation had best effect.Particles coalescence in ESP was mainly electricity aggregation,thermal aggregation and turbulence aggregation were supplemented,all three together played a very important role in promoting micro particles aggregation.So the development new technologies for ultra-fine particles reduction emissions,it was significant to pay attention to electricity aggregation technology,thermal aggregation and turbulent aggregation technology.The optimum operation condition for ESP was under flow velocity of 1.0 m/s,number density of particle volume fraction 1.4%,and corn stalk/anthracite coal co-combustion ratio 10%.It's of great significance for the subsequent modification of ESP and fuel selection.