低阶煤流化床热解气化新工艺

NEW PROCESS FOR PYROLYSIS AND GASIFICATION OF LOW RANK COAL BY FLUIDIZED BED

针对低阶煤流化床热解气化所遇到的问题,对热解炉供热模式、原料煤粒径与颗粒分级、热解气初级冷却与除尘、排灰方式等问题进行探讨,优化工艺过程。新工艺中,选择高温半焦为热解炉提供热量,将原料煤磨制成亚毫米级粉粒,磨煤产生的少量粒径小于0.1 mm的细颗粒被分离出来,送往配套的气流床气化炉,与流化床气化炉气体带出的细粉一起进行熔渣气化,提高碳转化率。大量粒径为0.1~1.0 mm的颗粒进热解炉,热解炉出来的气体经适当馏分煤焦油冷却、捕集颗粒物,使温度降至350℃左右,采用间接换热模式进一步降温,由此将有机废水产量降至近零水平,实现清洁高效热解气化。以低阶煤4600 t d规模的流化床热解气化新工艺为例,干基煤粗粉进热解炉,干燥单元取水约480 kt a,热解单元不产生有机废水,可产有效气体(一氧化碳和氢气)约1.09×10^9 m^3/a,产煤焦油约81 kt a,系统碳转化率大于95%,煤焦油、煤气、半焦的产率分别为8.97%,110 m^3/t,67.5%,半焦气化产物气中有效气体体积分数大于80%。

Aiming at the problems encountered in fluidized bed pyrolysis and gasification,the heating mode of pyrolysis furnace,coal particle size grading,primary cooling and dust removal of pyrolysis gas,and ash discharging mode were discussed to optimize the process.In the new process,the high temperature semicoke was chosen to offer heat for pyrolysis furnace.The low rank coal feed was grinded into submillimeter particle size in which the fine powder smaller than 0.1 mm was separated out and delivered to the matched entraind flow bed gasifier to conduct the melting slag gasify together with the fine powder from fluidized bed gasifier to raise the carbon conversion rate.The major powder with particle size between 0.1-1.0 mm was fed into the pyrolysis furnace.The outlet gas from furnace contacted with proper cut fraction of tar oil to remove the tiny particles and then cooled down to 350℃and further cooled by indirect heat transfer method.By this way the amount of organic wastewater could be lowered close to zero to realize clean and high efficiency pyrolysis and gasification.Taking the fluidized bed pyrolysis gasification process of low rank coal with a scale of 4600 t d as an example,the dry coal coarse powder entered the pyrolysis furnace,and the drying unit generated about 480 kt a water.No organic wastewater was produced in the pyrolysis unit,but about 1.09×10^9 m^3/a hydrogen and about 81 kt a coal tar were obtained.The carbon conversion rate of the system was up to over 95%.The yields of tar oil,coal gas,and semicoke reached 8.97%,110 m^3/t,and 67.5%,respectively and the volume fraction of effective gas in outlet gas of semicoke gasifier was more than 80%.