海藻生物质颗粒流化床燃烧试验研究

在小型流化床试验台上研究了海藻颗粒(条浒苔与马尾藻)的流化床燃烧。海藻在流化床内的挥发分析出燃烧时间都在1 min左右。条浒苔颗粒在流化床中燃烧先进行脱水和挥发分的燃烧,接着发生焦炭燃烧,其燃烧过程符合缩核模型,炭核由外向内逐层燃烧,而灰层半径几乎不变。但马尾藻颗粒由于挥发分的大量快速释放而迅速膨胀破碎成屑。另外通过对条浒苔颗粒及不同燃烧时间后收集的焦炭颗粒剖面的SEM扫描电镜观察,发现随着燃烧的进行,颗粒内孔隙增大,微孔表面粗糙。进一步详细研究了两种海藻颗粒(条浒苔与马尾藻)在流化床内单次投料下的燃烧。随着床温的升高,条浒苔释放NO_x相对浓度增加,CO相对浓度减少。而马尾藻释放气体中SO₂与NO_x含量相对条浒苔有所增加;随着床温的升高,CO相对浓度减少。床温的升高使得床内传热速率加快,两种海藻挥发分的析出提前,燃尽时间缩短。风速、床高的升高使得两种海藻燃烧容易,燃尽时间缩短。

Fluidized bed combustion of seaweed biomass particles

Fluidized bed combustion experiment of two seaweed particles(Enteromorpha clathrata and Sargassum natans)was carried out in a bench-scale combustor.When seaweed particles were fed into the fluidized bed, dehydration and release of volatile matter happened.Devolatilization and burning of volatile matter of seaweed particles during fluidized bed combustion happened in about 1 min, followed by combustion of char.Combustion of char accorded with the shrinking core model in which carbon nucleus burned layer by layer from outside to inside and ash layer radius remained almost constant.As volatile matter was released at the beginning of combustion, Sargassum natans particles fractured immediately after they were fed into the fluidized bed.SEM analysis was used to study the cross-sections of Enteromorpha clathrata particles and their chars collected at different combustion periods.During the combustion process of Enteromorpha clathrata particles, internal porosity of particles increased gradually.The micro-pore surface became rougher.By feeding a few seaweed particles at a time,combustion of two seaweed particles(Enteromorpha clathrata,Sargassum natans)was also studied in the fluidized bed.During combustion of Enteromorpha clathrata particles, relative concentration of NO_x increased, while relative concentration of CO decreased.The SO₂ and NO_x released from Sargassum natans particles were more than those from Enteromorpha clathrata particles.CO concentration also decreased with increasing bed temperature.Increasing bed temperature intensified heat transfer in the combustor. Devolatilization of two kinds of seaweed happened earlier, and burnout time both shortened.Increase of air velocity and bed height facilitated combustion of two kinds of seaweed and shortened their burnout time.