GB656910A - Pretreatment of distillation and cracking apparatus - Google Patents

Abstract

<PICT:0656910/IV (b)/1> The formation of coke during the production of ketene by cracking organic compounds in apparatus wherein the surfaces which come into contact with the material being treated are composed of high-chromium and high-nickel steel, is reduced by preliminarily treating the surfaces with a gas containing a substantial proportion of carbon monoxide at a temperature within the range 1200-1800 DEG F. and a pressure between 0 and 100 pounds per square inch. The steels to which the invention particularly relates contain 23 to 27 per cent chromium, 12 to 20 per cent nickel, and less than 0.2 per cent carbon. The apparatus shown is suitable for cracking acetone to make ketene. The acetone is vaporized in coil 2, and is then preheated to about 1200 DEG F. in coil 4 which is of large diameter and is composed of the alloy referred to above. Alternatively the preheater may consist of rows of straight tubes connected in series or in parallel. The preheated acetone is cracked in coil 6 which is of less diameter than the preheater, and is made of the alloy referred to above. The contact time is between 0.25 and 0.75 seconds, the mass velocity being about 10-40 pounds per square foot per second; and the outlet temperature is between 1300 DEG and 1400 DEG F. The products are discharged into tower 8 where the ketene is reacted with acetic acid which is introduced through conduit 9. Prior to the cracking process, the apparatus is treated with carbon monoxide or a mixture of carbon monoxide and hydrogen at a temperature of 1200 DEG F. and a pressure of 5 pounds per square inch g. for a period of 1 to 24 hours. The production of ketene from acetic acid and acetic anhydride is also referred to.ALSO:<PICT:0656910/III/1> The formation of coke during the distillation or cracking of organic compounds in apparatus wherein the surfaces which come into contact with the material being treated are composed of high-chromium and high-nickel steel, is reduced by preliminarily treating the surfaces with a gas containing a substantial proportion of carbon monoxide at a temperature within the range 1200-1800 DEG F., and a pressure between 0 and 100 p.s.i.g. The steels to which the invention particularly relates, contain 23 to 27 per cent chromium, 12 to 20 per cent nickel, and less than 0.2 per cent carbon. The apparatus shown is suitable for cracking acetone to make ketene. The acetone is vaporized in coil 2, and is then preheated to about 1200 DEG F. in coil 4 which is of large diameter and is composed of the alloy referred to above. p Alternatively the preheater may consist of rows of straight tubes connected in series or in parallel. The preheated acetone is cracked in coil 6 which is of less diameter than the preheater and is made of the alloy referred to above; the contact time being between 0.25 and 0.75 seconds, the mass velocity being about 10-40 pounds per square inch per second, and the outlet temperature being between 1300 DEG and 1400 DEG F. The products are discharged into tower 8 where the ketene is reacted with acetic acid which is introduced through conduit 9. Prior to the cracking process, the apparatus is treated with carbon monoxide or a mixture of carbon monoxide and hydrogen at a temperature of 1200 DEG F. and a pressure of 5 pounds per square inch g. for a period of 1 to 24 hours. The production of ketene from acetic acid and acetic anhydride is also referred to.ALSO:The formation of coke during the distillation or cracking of organic compounds in apparatus wherein the surfaces which come into contact with the material being treated are composed of high-chromium and high-nickel steel, is reduced by preliminarily treating the surfaces with a gas containing a substantial proportion of carbon monoxide at a temperature within the range 1200 DEG -1800 DEG F and a pressure between 0 and 100 lb. per square inch. The steels to which the invention particularly relates contain 23 to 27 per cent chromium, 12 to 20 per cent nickel, and less than 0.2 per cent carbon. In the cracking of acetone to make ketene (see Group IV (b)), it has been found suitable to condition the apparatus using carbon dioxide or a mixture of carbon monoxide and hydrogen in the ratio of 1:1 to 2:1 H2/CO, at a temperature of about 1200 DEG F and a pressure of 5 lb. per square inch for a period of 1 to 24 hours.