在用多孔性固體(ti)物質處理(li)流(liu)體(ti)混合物時(shi),流(liu)體(ti)中(zhong)的某(mou)一組(zu)分(fen)或某(mou)些組(zu)分(fen)可被吸表面并濃集(ji)其(qi)上(shang),此現象稱(cheng)為(wei)吸附。吸附處理(li)廢氣時(shi),吸附的對象是氣態污染物,氣固吸附。被吸附的氣體(ti)組(zu)分(fen)稱(cheng)為(wei)吸附質,多孔固體(ti)物質稱(cheng)為(wei)吸附劑(ji)。
吸收法采用(yong)(yong)低揮發(fa)(fa)或不揮發(fa)(fa)性(xing)溶(rong)劑(ji)對VOCs進行吸收,再利(li)用(yong)(yong)VOCs和吸收劑(ji)物理性(xing)質的差異進行分(fen)離。
含VOCs的(de)氣體(ti)(ti)自吸收(shou)(shou)塔(ta)(ta)底部進入塔(ta)(ta)內,在(zai)上(shang)升過(guo)程中(zhong)與來自塔(ta)(ta)頂的(de)吸收(shou)(shou)劑逆(ni)流接觸,凈(jing)化后(hou)的(de)氣體(ti)(ti)由塔(ta)(ta)頂排出(chu)(chu)。吸收(shou)(shou)了VOCs的(de)吸收(shou)(shou)劑通過(guo)熱交換器后(hou),廢氣處(chu)理(li)設備進入汽提塔(ta)(ta)頂部,在(zai)溫度(du)高于吸收(shou)(shou)溫度(du)或壓(ya)力低于吸收(shou)(shou)壓(ya)力的(de)條(tiao)件下(xia)解吸。解吸后(hou)的(de)吸收(shou)(shou)劑經過(guo)溶劑冷(leng)凝(ning)器冷(leng)凝(ning)后(hou)回到吸收(shou)(shou)塔(ta)(ta)。解吸出(chu)(chu)的(de)VOCs氣體(ti)(ti)經過(guo)冷(leng)凝(ning)器、氣液(ye)分離(li)器后(hou)以較純的(de)VOCs氣體(ti)(ti)離(li)開汽提塔(ta)(ta),被回收(shou)(shou)利用(yong)。該工藝(yi)適合于VOCs濃度(du)較高、溫度(du)較低的(de)氣體(ti)(ti)凈(jing)化,其他情況下(xia)需要作相應的(de)工藝(yi)調整。
固體表(biao)面(mian)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)了吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)質(zhi)后,一(yi)部(bu)被(bei)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)的吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)質(zhi)可從(cong)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)劑表(biao)面(mian)脫離,此(ci)現附(fu)(fu)(fu)(fu)(fu)(fu)。而當吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)進行(xing)一(yi)段時(shi)(shi)間(jian)后,由于表(biao)面(mian)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)質(zhi)的濃集,使(shi)其(qi)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)能力明顯下降而吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)凈化的要求,此(ci)時(shi)(shi)需要采用(yong)(yong)一(yi)定的措施使(shi)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)劑上(shang)已吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)的吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)質(zhi)脫附(fu)(fu)(fu)(fu)(fu)(fu),以協的吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)能力,這個過(guo)程(cheng)(cheng)稱為吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)劑的再生。因此(ci)在實(shi)際(ji)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)工程(cheng)(cheng)中(zhong)(zhong),正是利(li)用(yong)(yong)吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)一(yi)再生一(yi)再吸(xi)(xi)(xi)(xi)(xi)附(fu)(fu)(fu)(fu)(fu)(fu)的循環(huan)過(guo)程(cheng)(cheng),達(da)到除去廢(fei)氣(qi)中(zhong)(zhong)污染(ran)物質(zhi)并回收(shou)廢(fei)氣(qi)中(zhong)(zhong)有用(yong)(yong)組分。