熔渣气化炉喷嘴燃烧区行为的数值模拟研究

Numerical study on combustion zone behaviors of a slagging gasifier

燃烧区是熔渣气化炉的重要区域,其对熔渣气化炉的工作状态具有明显影响。基于双欧拉模型探究了燃烧区的速度场、温度场和组分场的分布特征及燃烧区空腔的形成过程。研究发现:工业级熔渣气化炉燃烧区呈“羽”状,其先向炉中心延伸再斜向上发展;气体在熔渣气化炉中心区域的流动速度为2.5 m/s左右,但未形成“高速对撞区”;高温区出现在燃烧空腔外表面附近特别是正对喷嘴且靠近炉中心的区域,该区域的温度可以达到约2000℃;氧气主要分布在气化剂喷嘴前端约0.5 m的空腔内,一氧化碳的分布区域与水蒸气在空间上有较大程度重叠,二氧化碳主要在喷嘴前端空腔外壳附近生成,氢气浓度较高的区域则出现在燃烧区对应空腔的上沿;沿喷嘴轴线方向,气体温度呈先升至峰值再逐渐下降的趋势。随着气化剂流量的增大,燃烧温度极大值出现的位置逐渐朝炉中心处移动,并呈较明显的线性变化规律。

The combustion zone is an important region in a slagging gasifier,as it determines the working state of a coal gasifier.This study applies the Eulerian-Eulerian model to study the gas-coal behaviors in this region in an industrial-scale coal gasifier.The model considers the flow,heat transfer and chemical reactions for both gas and coal phases.The model is also used to explore the formation process of the combustion zone and the distribution of velocity,temperature,and species in and around it.It is found that the combustion zone is of a plume-like shape,extending to the centre of the gasifier and then towards the top obliquely;the gas velocity is about 2.5 m/s in the central regions of the gasifier,without forming a high-speed collision zone;the high-temperature zone appears near the surface of the combustion zone,especially that facing the nozzle and near the centre of the gasifier,where the temperature can reach as high as 2000℃.Besides,it is found that oxygen is mainly distributed at about 0.5 m in front of the nozzle,while the distribution of carbon monoxide and water vapor overlap in space to a large extent;carbon dioxide is mainly generated near the outer surface of the combustion region while a higher concentration of hydrogen appears above the combustion region.Along the direction of the nozzle axis,the gas temperature first increases to a peak and then gradually decreases.With increasing gasification agent flow rate,the position where the maximum value of combustion temperature appears gradually moves to the centre of the gasifier,showing an obvious linear change pattern.