【作者】 王剑；

【导师】 刘海峰；

【作者基本信息】 华东理工大学 ， 热能工程， 2013， 博士

【摘要】 工业气化炉在长期运行中经常出现渣块堵塞气化炉渣口的现象,严重威胁着装置的经济、安全、稳定运行。根据合成气和熔渣的流向,液态熔渣在气化炉渣口有气渣并流和气渣逆流两种排渣方式。本文采用冷模实验的方法研究了熔渣在渣口下方空间的流动特征,运用数值模拟的方法研究了熔渣在渣口下方水冷壁面上的沉积、相变和生长过程,探讨了Shell气化炉渣口大渣块形成的原因,提出了相应的消除大渣块的措施,同时分析了气渣并流冷模实验装置渣口下方水冷壁面上熔渣的沉积规律。(1)熔渣在Shell气化炉渣口排渣属于气渣逆流过程。本文采用糖浆作为模拟介质模拟液态熔渣流动,建立了Shell气化炉渣口区熔渣流动行为冷模实验装置,研究结果表明,模拟熔渣在Shell气化炉渣口并非自由沉降落入渣池,而是破裂形成细长的液丝,部分液丝因高速旋流气流的作用而沉积在渣裙壁面上。模拟熔渣在渣裙壁面上的沉积率随渣口气速的增大而增大,随渣流速的增大而减小；随着粘度的降低和操作负荷的增加,模拟熔渣液丝的数目和模拟熔渣在渣裙壁面上的沉积率都增大；喷嘴使用情况对模拟熔渣在渣口区的流动特征有较大影响。相邻喷嘴和三喷嘴实验条件下,模拟熔渣会集中沉积在渣裙壁面某一区域上。(2)建立了Shell气化炉渣口区壁面上熔渣流动、相变和生长的动态模型,研究结果表明,当渣层表面温度低于临界温度时,熔渣全部凝固成固态渣层,平衡时,固态渣层表面覆盖了一层液态渣层且其表面温度高于临界温度；固态渣层的厚度沿着熔渣流动的方向增加；当操作温度和沉积率降低时,固态渣层厚度和特征时间增加,当操作温度和沉积率一定时,粘温特性对固态渣层厚度和特征时间没有影响；固态渣层厚度可以通过增加操作负荷和操作温度来降低,当操作负荷和操作温度增加时,固态渣层厚度一直降低直至达到一个稳定值,相应的特征时间需要数百小时甚至更多。(3)本文同时搭建了气化炉渣口气渣并流冷模实验装置,采用糖浆作为模拟介质,研究了突扩比对熔渣在渣口下方流动特征和在突扩圆管壁面上沉积行为的影响。冷模实验研究结果表明,突扩比对熔渣在渣口下方的流动行为有很大影响。当渣口气速、操作负荷、渣流速和模拟介质粘度等因素保持不变时,随着突扩比的增大,模拟熔渣液膜破裂形成的液丝数目减少,模拟熔渣在渣口下方水冷壁面上的沉积率减小,同时熔渣沉积区域远离渣口。(4)在气渣并流排渣情况下,系统地研究了熔渣在辐射废锅上方的流动行为。冷模实验研究结果表明,操作负荷和渣口气速较低时,模拟熔渣不会沉积在辐射废锅壁面上,但是当操作负荷和渣口气速较高时,因废锅入口气体的射流和回流区气流的卷吸作用,部分模拟熔渣将会沉积在废锅壁面上；随着操作负荷和渣口气速的增大,模拟熔渣的液丝数量增加,模拟熔渣在废锅壁面上的沉积率增大,同时熔渣沉积区域向渣口靠近；随着模拟介质粘度和渣流速的降低、模拟熔渣的液丝数量增加,模拟熔渣在废锅壁面上的沉积率增大,同时熔渣沉积区域向渣口靠近。更多还原

【Abstract】 There was slag blockage at the slag tap hole during long tome operation of gasifier sometimes, which is a great threat to the economic, safe and stable operation of device. According to the flow direction of syngas and slag, there were two ways of slag discharge: gas-slag countercurrent flow and gas-slag concurrent flow. Cold model experiment was carried out for observing the simulated slag flow characteristic under the slag tap hole. A dynamic model was developed to clarify the slag deposition、transition and growth on the membrane wall. The reason of slag blockage at the slag tap hole of Shell gasifier was tried to explore and corresponding measures to eliminate slag block were also put forward. The deposition behavior on the membrane wall under the slag tap hole of cold model experiment of gas-slag concurrent flow was also analysised.The slag discharge at the slag tap hole of Shell gasifier is gas-slag countercurrent flow process. Cold model experiment study on slag flow at the tap hole region of Shell gasifier was set up and the syrup was used as medium. The results indicate the simulated slag was broke up to slender liquid fragments and a part of the liquid fragments deposit on the screen wall, other than flow into the slag bath under the force of gravity. The deposition rate of slag deposition on the screen wall increases with increasing air velocity at the slag tap hole, whereas it decreases with increasing slag velocity; the liquid fragments of simulated slag and the deposition rate on the screen wall increase with decreasing viscosity and increasing operating load; the use of nozzle has a great influence on the simulated slag flow characteristic at the tap hole region. The simulated slag deposit on certain region of screen wall under experimental conditions using adjacent nozzle or three nozzle.A dynamic model of slag flow、transition and growth on the wall of slag tap hole region of Shell gasifier was performed. When the slag surface temperature is lower than critical temperature, the molten slag is totally solidified. When the slag surface temperature is above critical temperature, the solid slag layer is coated with a molten slag layer at equilibrium. the solid slag thickness increases along slag flow; as the operating temperature and deposition rate are decreased, the solid slag thickness and characteristic time increase. When the operating temperature and deposition rate keep constant, viscosity-temperature characteristic has no effect on the solid slag thickness and characteristic time; increasing the operating load and operating temperature make the solid slag become thin, when the operating load and operating temperature increase, the solid slag thickness keeps decreasing until it stabilizes after hundreds of hours or more.Cold model experiment of gas-slag concurrent flow was carried out for studying the effect of sudden expansion ratio on the slag flow behavior under the slag tap hole and deposition behavior on the membrane wall. The syrup as used as medium. The results indicate the sudden expansion ratio has a great effect on the flow behavior under the slag tap hole. When the gas velocity at the slag tap hole、operatong load、slag velocity and viscosity of simulated medium keep constant, the liquid fragments of simulated slag and the deposition rate on the membrane wall decrease with increasing sudden expansion ratio, while the distance between deposition region and slag tap hole increases with increasing sudden expansion ratio.Cold model experiment of gas-slag concurrent flow was systematacially carried out for observing the simulated slag flow behavior in the upper region of radiant syngas cooler. The results indicate that when the air velocity and operating load is fairly low, the simulated slag doesn’t deposit on the wall, but as the air velocity and operating load is fairly high, a part of the simulated slag deposit on the wall by an air jet in the inlet zone and the air entrainment in the recirculation region; the liquid fragments of simulated slag and the deposition rate on the wall increase with increasing operating load and air velocity at the slag tap hole, whereas the distance between deposition region and slag tap hole increases with decreasing operating load and air velocity; the liquid fragments of simulated slag and the deposition rate on the wall increase with decreasing viscosity and slag velocity, whereas the distance between deposition region and slag tap hole increases with increasing viscosity and slag velocity.更多还原