Cleaning cooling apparatus used in the production of (meth)acrylic acid by two-stage catalytic gas phase oxidation involves purging with hot, oxygen-containing gas while increasing the oxygen content in a controlled manner

摘要

Cooling apparatus used between stages 1 and 2 in the catalytic gas phase oxidation of propene or isobutene to (meth)acrylic acid is cleaned by hot purging with oxygen-containing gas while increasing the oxygen content from 3-5 to 21 vol.% in such a way that the off-gas temperature is always at least 20 degrees C below the temperature limit for the material in the apparatus. A method for cleaning a cooling system with heat transfer surfaces as used in the production of (meth)acrylic acid by 2-stage catalytic gas-phase oxidation of propene or isobutene, i.e. for cooling the gas mixture from reaction zone 1 (production of (meth)acrolein) before it enters zone 2 (production of (meth)acrylic acid). This involves passing gas with a controllable oxygen content through the cooler with the heat transfer surfaces at a temperature of at least 380 degrees C, using an oxygen content which is increased from 3-5 vol.% to 21 vol.% during the cleaning process and regulated in such a way that the temperature of the off-gas from the cooler is always at least 20 degrees C below the maximum temperature allowed by the thermal stability of the material in the cooler.