CO_2回收式加压流化床煤气化建模与数值计算

Modeling and Numerical Calculation for Pressurized Fluidized Bed Coal Gasification with Carbon Dioxide Recovery

以新型CO2回收式煤气化系统为研究对象,建立了加压流化床煤气化动态数学模型,包括颗粒模型、气相模型、气泡模型和焓平衡模型,探讨了给煤速率、氧碳比以及水蒸气比等操作参数对碳转化率、产气量以及冷煤气效率的影响,由此确定了煤投入量的最佳操作范围。计算结果表明：在采用CO2回收循环系统下可获得70%以上的（CO＋H2）合成气;CO2气氛下的气化能力比在空气气氛下减少了约2%;反应压力为1.5 MPa时,给煤速率的最佳操作范围为1.3~1.8 kg/（m2·s）;氧碳摩尔比为0.5时冷煤气效率可达76%;气化温度与氧碳比基本呈线性关系,通过对氧碳比的控制可有效地调节气化温度;随着水蒸气比的增加,冷煤气效率会出现最大值,气体热值会逐渐增大;在气化温度为1073~1273 K时,CO2气氛下反应的操作范围比空气气氛下的范围大。

Based on new type pressurized coal gasification with carbon dioxide recovery, dynamic mathematical models of pressurized fluidized bed coal gasification were established including solid particle model, gas-side model, hydrodynamic model of bubbles and enthalpy balance model. The effects of following factors on the carbon conversion rate, gas production rate and cold gas efficiency were discussed, such as coal feed rate, oxygen carbon ratio and steam ratio, etc, and subsequently the optimum range of coal feed rate was determined. The results are as follows： In the carbon dioxide recycle system, more than 70% （CO＋H2） forming gas can be obtained. The gasification scale under CO2 atmosphere is less than under air atmosphere by about 2%. For an operation pressure of 1.5 MPa, the optimum range of coal rate is from 1.3 kg/（m2＇s） to 1.8 kg/（m2.s）. The cold gas efficiency may get up to 76% when the oxygen-carbon ratio is 0.5. The gasification temperature is in direct proportion to the oxygen-carbon ratio, and gasification temperature can be effectively regulated through controlling the ratio of oxygen-carbon ratio. The cold coal gas efficiency will get up a maximum value and the gas heating value will gradually increase with the increase of steam ratio. The operating range of reaction under carbon dioxide atmosphere is greater than under air atmosphere when gasification temperature is from 1073K to 1273K.