Continuous purificn. of waste gas contg. phenol - by two=stage scrubbing with sodium hydroxide soln. with higher sodium phenolate concn. in first stage

摘要

Purificn. is carried out by 2-stage scrubbing. In the first stage, the gas is scrubbed with a soln. (I) contg. Na phenolate (II) and NaOH, with supply of NaOH soln. from the second stage, the (II) concn. being kept at min. 5 wt.% by circulating (I). In the second stage(s), the gas is scrubbed with a circulating NaOH soln. (III) with a (II) concn. kept below 5 wt.% Pt of the soln. from each stage is transferred to the previous stage (dis)continuously and fresh NaOH soln. is supplied to the last stage. The process is useful for purifying waste gas from chipboard mfr. etc. It is efficient and cheaper than usual and allows the phenol content to be reduced from 100-2000 mg/Nm3 to max. 20 mg/Nm3. Pref. (I) contains 5-30 wt.% (II) and is kept at pH 8-12 by controlling the.