260 



REPORTS ON THE STATE OP SCIENCE.— 1920. 



through, a ' heat exchanger ' situated so near the ovens that its temperature can 

 be raised to between 60° and 80° C. at the expense of some of the sensible heat 

 in the hot crude gas leaving the ovens. The strong acid (95 per cent.) used for 

 the absorption is also pre-heated to the same temperature. The scrubbing 

 process for the removal of ethylene is carried out on the counter-current prin- 

 ciple, and the time of contact between the pre-heated gas and acid is 2^ minutes, 

 which is sufficient to effect absorption of 70 per cent, of the total ethylene 

 present. The acid can be used until it has absorbed up to 5 per cent, of its 

 weight of ethylene with the formation of a corresponding quantity of ethyl 

 hydrogen sulphate. 



The strong acid from the ethylene absorption towers containing the ethyl 

 hydrogen sulphate is next taken to a special form of distilling column where 

 it meets a current of steam which dilutes the acid to about 75 per cent, strength 

 and simultaneously hydrolyses the ethyl hydrogen sulphate forming ethyl alcohol 

 and sulphuric acid. The heat produced during the dilution is sufficient to raise 

 the temperature of the diluted acid to between 90° and 100" C, under which con- 

 ditions the resulting alcohol distils over and is subsequently condensed, finally 

 leaving the plant as a 95 per cent, alcohol. 



The diluted acid is finally pumped to the top of a Gaillard concentration 

 tower where it is concentrated to a 95 per cent, strength, which is then used 

 ever again for the absorption of ethylene. Any small quantity of sulphurous 

 acid formed by the reducing action of the gases upon acids in the absorption 

 tower is, during the dilution process, decomposed, and the resulting sulphur 

 dioxide is (as aforesaid) utilised for the elimination of sulphuretted hydi-ogen 

 from the debenzolised gas. 



From figures given in Messrs. Bury and Ollander's paper {loc. cit.) the com- 

 position of the debenzolised gas from a Durham coking coal, before and after 

 the removal of the greater parts of its ethylene content in the manner proposed, 

 is as follows : — 



Carbon Dioxide 



Carbon Monoxide 



Ethylene, &c. . 



Methane . 



Hydrogen 



Nitrogen and Water Vapour, 



100-0 



100-0 



Gross 

 Net 



W. A. Bone. 



