工业炉小型液排渣燃烧器速度场浓度场及温度热流量的研究

STUDY ON THE VELOCITY AND CONCENTRATION FIELDS,TEMPERATURE AND HEAT FLUX OF THE ENTRAINED SLAGGING POWDER COAL COMBUSTOR OF THE FURNACES

本文介绍了工业炉小型液排渣粉煤旋风燃烧器热态试验结果,一次风旋流数S_1=1.5时冷态试验的速度场浓度场以及 S_1对流场四个回流区回流率的影响,计算了液排渣燃烧器前室火焰温度及热流量,热态测定与计算的火焰温度相符.

The entrained slagging coal combustor is a new model of the coal combustor.For the past four years,we have been developing an advanced pulverized coal combustor with entrained slagging for use in the retrofit of current coal-fired continuous furnaces.The combustor offers significant ad- vantages including high slag removal(80%),high carbon burnout(99.5%),high volume thermal flux(45×10~6KJ/m^3·h),low NO_x(250-450 ppm) and low heat rejection (5-8%).Firing is very easy and entrained slagging is very smooth. The entrained slagging coal combustor consists of a water-cooled right circular cylinder with a simple baffle located in the aft region to promote the appropriate mixing and combustion reactions and improve slag flow patt- erns.Powdered coal (70% through 200 mesh) is transported to the nozzle in a dense-phase fluidizcd condition,spirally injected into the combustor and burned in the cylindrical volume with slag impinging on the wall The slag is driven to the slag tap by combined force due to gas flow and gravity. It flows into a water-filled slag tank where fracture and size reduction are accomplished. V series of cold and hot experiments were carried out to investigate the distributions of the velocity and the first air concentration under the condi- tion of the whirlling number of the first air S_1=1.5,and to analyse the influence of S,on the central and annular reflux ratio. Generally the combustor is operated at an equivalence ratio in the range of 0.7-0.9,the resulted hot product gas which is rich in CO and H_2 is ducted to the aft chamber where secondary air is added.The combustion of the product gas is completed within the secondary burner,resulting in a stagewise combustion process which minimizes NO_x formation.Sufficient temperature and heat flux must be generated within the coal combustor volume to faciliate flow of liquid slag,but the classical high NO_x formation regime can be avoided by the combination of temperature and gas composition control.The calculated and measured flame temperature is 1750℃,and the calculated heat flux is 3.3×10~6kJ/m^2.h.Test results indicate there are four reflux regions in the axial direction,i.e.,the central reflux and the annular reflux of the front region,and the open central reflux and the annular reflux of the aft region The distributions of the tangential velocity show good similarity so that a single correlation is needed to represent the velo- city field. V=V_1(R/r)[1-exp(-)] where V_1-tangential velocity at first air duct R-radius of the combustor =r/R_1 R_1 is radius of the eddy nucleus. Tests results also show that the distributions of the first air concen- tration match well with those of the velocity.