75t/h CFB Boiler’s Structure Parameters Of Furnace On The Solid Phase Concentration Distribution And Transformation

CFB boiler has been developed rapidly since the 1970 s. It has such features as extensive fuel flexibility, high combustion efficiency, low NOX emissions, rapid load change ability and good comprehensive utilization of ash. And as the key component, the furnace’s design parameters is very important to the CFB boiler, it affects the CFB boiler’s burning,heat diffusion, output, combustion efficiency, the carbon content of fly ash and so on. But for the research, its development is still in the initial stage, the experience is still dominant. So the design and analysis of the CFB boiler furnace is necessary.At first, this paper sets up two different models of the substructure of the 75t/h CFB boiler and calculates theoretically that under the condition of the same substructure of the CFB boiler: the lower the distance between secondary air nozzle and the air distributor is, the higher the flow velocity of gas in dense-phase zone is. If the substructure is different(the distance between the secondary air nozzle and the air distributor is exactly equal), the smaller the secondary air plane area is, the higher the flow velocity of gas is. At the same time, the paper analyzes the gas flow velocity at the bottom of the 75t/h CFB boiler’s furnace.Secondly, the paper sets up different models of the substructure of the 75t/h CFB boiler,then analyze that: The concentration in the dense-phase zone is high and it is low in the dilute-phase zone by ANSYS Fluent. Ring-nuclear particles exists in the dilute- phase zone.In dense-phase zone, the higher the gas flow rate is, the lower the particulate fluidization velocity is higher; the particles of bed void fraction increases,the concentration of particulate is. In the condition that the substructure of the 75 t/h CFB is equal,it can improve the fluidizing velocity in dense-phase zone if we reduce the distance between the secondary air nozzle and the air distributor appropriately.If we reduce the particle concentration in the dense-phase area and increase the particle concentration in the dilute-phase zone, the boiler circulating rate will be increased. In the condition that the substructure of the 75t/h CFB isdifferent(the distance between the secondary air nozzle and air distributor is equal),the smaller the scetion of secondary air nozzle is,the higher the particle fluidization velocity is.And the particle voidage will be increased. If the particle concentration is reduced, the particle concentration in the dilute-phase will be increases, the boiler circulating rate will also be increased.Finally, the paper analyzes the drop of a power plant of 4 units of 75t/h CFB boiler.It is found that if we change the charging coal quality, the combustion share in dense-phase zone will be increasd, the boiler circulating rate will be declined. Then we transform the substructure of the 75t/h CFB boiler,adopt tapered flaring above the secondary air nozzle, and reduce the distance between secondary air nozzle and the air distributor. After this, the output is increased;the differential pressure chamber of a stove and furnace outlet temperature are improved,the combustion share and particle concentration in the dilute-phase are increased,the boiler circulating rate and the output are increased. At the same time, the secondary air nozzle area and range are increased; the range of fly ash carbon content is reduced, the carbon content of fly ash is reduced. And the air backflow can improve the combusition share in the dilute-phase zone.