Study on improving tar quality from staged pyrolysis of low rank coal in multistage fluidized bed

in order to improve tar quality from pyrolysis of low rank coal.the new technicue of low rank coal pyrolysisin mulistage fuidized bed withcal staed pyrolysis in the upper stage and char gasification in the lower stage was proosed. The efifcts on products distrbution an tar qualty were investigated under the conditon of different operation mode( the numbers of fuidized bed stages was sing e,cdouble and three respecivly excesivecoxygen raio and steam and coal mass raio h2results showed that the oxygen and steam as gasifying agert could promofe cracking of polycyeic aromat c hydrocaoon.The heay tar specis formed in the high temperature region was contacted with hot char when they passed the upper bed which cou d be furthery cracked and reformed under thecataysis of char to improve th ar qualit : With increasing the number of stages fromn singie to three.the yield of pyrolysis gas and ta,and the content of lghtail increased,whereas the char yield,the amount of component oftarthecontent of phenol oi nd wash oil decreased. The content of both helghtail and phenol oil oftarobtained from the tree-stage fuidizedbed pyrolysis reached 99.49%.Therefore,the tar with high content of light al could obtained by staged pyrolysis of low rank cal in muitistag fuidized bed.