Numerical Simulation Of Two-phase Flow In W-type Flame Boiler And Fluidized Bed Compound Boiler

Coal resources has been playing a very important role in industrial development all the time.Anthracite and lean coal have a large proportion of coal,so in recent years,China's power plant has adopted W type flame combustion technology,specially used for burning anthracite.W-type flame boiler has a series of advantages such as high combustion efficiency,but the exposed structure is complex,and NO_x emissions,combustion stability and other issues have been restricting and affecting the development of W-type flame boiler.The introduction of composite combustion technology and composite boiler transformation technology program is a good choice to improve the W-type flame boiler.In this paper,a 350 MW subcritical W-type flame boiler is used to carry out the technological transformation of the composite boiler.The scheme of adjusting the cold ash bucket angle and continuing the bubbling fluidized bed is used,which can make full use of the stable combustion,high desulfurization efficiency,large adjusting scope of the fluidized bed.The scheme can make up for the lack of W-type flame boiler.Due to the time and financial problems,we only carry out the numerical simulation calculation,studying and analyzing the flow field characteristics of the W-type pulverized coal-fluidized bed composite boiler and the combustion characteristics of the heterogeneous reaction.In this paper,we use the Euler-Euler two-fluid model to simulate the different flow velocity in the original W-type flame boiler with the same wind distribution.The paper studied the effects of different fluidized on the flow field characteristics of the fluidized bed composite furnace.By analyzing the flow field and concentration field distribution of the central cross section of different working conditions,the fluidization velocity can affect the formation of "W" type airflow,the spatial position and the symmetry of the flow field.By observing the velocity profile of the air in the cross section of the third air outlet and the velocity of the small particles,the position change of the "W" type air flow can be analyzed more intuitively.By analyzing the concentration distribution and velocity distribution of air and particles with different particle sizes at different height,we can conclude the effects of reasonable working conditions and different fluidization rates on the whole flow field.In the flow field reasonable conditions,cut off a number of cross-section,observe and analyze of the entire composite furnace flow field characteristics.Select the fluidized bed fluidization speed of 1.3m/s working conditions,maintain the same wind rate,only change the third wind down angle of down angle of 0°,15°,30°,45° and 60°,we study the effects of the three wind dip on the composite furnace flow field.By comparing the concentration and velocity distributions on the cross section of the five working conditions,we can see that the distribution of the flow field is symmetrical.And the influence of the third dip angle on the flow field of the composite furnace is further studied by analyzing the descending velocity decay curve and the velocity distribution on different height intercepts.For the simulation of combustion in W-type pulverized coal-fluidized bed composite furnace,the combustion process is simplified and designed.The simplified combustion process is mainly the heterogeneous reaction between carbon particles and oxygen and carbon dioxide,and we write a UDF compute the chemical reaction rate.The flow rate is 1.3m/s,and the reasonable boundary condition is used to simulate the combustion.The distribution of flow field,temperature field and concentration field is analyzed.The velocity and temperature distribution at the center of the third wind reflects the flow distribution and combustion.Select the data on the center of the three different cross sections to analyze the temperature,velocity and concentration distribution in the furnace.At the same time,we select the different height intercepts in three different areas of the composite furnace to study the velocity and temperature distribution in the W-type flame boiler,fluidized bed and the transition zone between the two.