Abstract: A method and apparatus for quenching and scrubbing a hot gas using a liquid in a single packed column while controlling mist formation. Hot gas is introduced at the bottom of the column and drawn upward countercurrent to the scrubbing liquid. The column has three stages, each packed and fed liquid from above. The first stage is a quench region wherein the gas flow rate, liquid flow rate and liquid temperature are controlled such that the quench rate does not exceed 5.4° C./ft2 of packing to prevent formation of an aerosol mist. The second and third stages for scrubbing employ packed regions separately supplied with increasingly cooler and purer liquid.

Abstract: In this process for the preparation of ketene by the thermal, catalytic cracking of acetic acid under reduced pressure, the hot cracked gases are cooled to approx. 0.degree. to -10.degree. C. and, in the course thereof, water, unreacted acetic acid and acetic anhydride are condensed. The quantity of acetic acid employed for the thermal cracking reaction should be 0.5 to 2.5 t.times.hours.sup.-1 .times.m.sup.-3, relative to the volume V of a shell-and-tube heat exchanger through which the cracked gas is passed. The pressure drop in the tubular heat exchanger should be 50 to 150 mbars and the surface/volume ratio should be 60 to 120 m.sup.-1.