| 摘要 |
<p>Conc. sulphuric acid and/or oleum is made from impure, 30-60% waste H2SO4 (I), by (a) concentrating at 50-150 degrees C. in the presence of a gas stream (d) to obtain over 60-75 wt.% H2SO4, which is then thermally cracked to obtain gas contg. SO2; converting the SO2 catalytically to SO3; (c) absorbing SO3 to form conc. H2SO4 and/or oleum, plus a gas (d) which is free from SO3 and is used in (a). Pref. (a) is carried out at 65-100 degrees C. and part of the acid obtd. is reheated and recycled. Gas (d) is pref. used in one to three stages in (a), esp. by using 1-3 packed columns in which gas (d) flows in counter current to (I). The gas leaving (a) is pref. fed through a final gas washer and the soln. obtd. from the latter is fed to the thermal cracking appts. Used in recovery of H2SO4 in chemical processes. e.g. in the prodn. of methylacryl-ether; or in TiO2 mfr. Process provides economic use of energy. Impurities are not transferred from (I) to gas (d) which is finally released to the environment. Plant corrosion during (a) is avoided.</p> |
