CHAIRMAN'S ADDRESS - Coke Oven Managers Association

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A REVIEW OF C.O.M.A. ACTIVITIES, 1939-1945 - CLARKE 189.by acid-washing of cyclopentadiene (C 5 H 6 ) and di-cyclopentadiene(C 10 H 12 ), present in crude benzole. Since cyclopentadiene boils at 42 0 C., itcan be eliminated in the forerunnings (together with carbon disulphide,boiling at 46 0 C.), using a Barbet fractionating column or other efficientdevice. However, cyclopentadiene rapidly polymerises to the dimer form(boiling point 170 0 C.) on storage, and accordingly it was recommendedthat cyclopentadiene should be separated from the crude benzoleimmediately on production. When benzole has been stored anddicyclopentadiene has been produced it was found that this compounddepolymerised during distillation, and the monomer then appeared innearly all the spirit fractions.The authors also showed that another means of reducing the acidity wasto use the lowest strength acid necessary to effect the required reduction insulphur content. For an acid of given strength, there was an optimumamount at which sulphur dioxide production was greatest. Beyond themaximum, the quantity of sulphur dioxide produced was shown to beinversely proportional to the acid used.With the realisation of the importance of making the best use of wartimesteel supplies, and of labour necessary to fabricate and erect steelplant, this paper made a valuable contribution to the conservation ofdistillation plant through the avoidance of corrosion.In a paper to the Midland Section in January 1942 (repeated before theSouthern Section in February 1942, Mr. G.J. Greenfield considered theprinciples and practice of benzole recovery from the gas. In his position asAdvisor on Benzole for the Department of Mines, Mr. Greenfield was inthe unique position of having visited every benzole plant at U.K. cokeovens, and his paper provided much useful information covering everyaspect of recovery. He stressed the importance of maintaining a lowviscosity of the absorbing oil, circulation at a rate sufficient to ensurethorough wetting of scrubber grids and cooling of the medium to theappropriate temperature in relation to that of the gas. The desirability ofturbulent flow conditions in oil coolers to achieve maximum efficiency wasdiscussed, and importance was attached to the supply of sufficient coolingwater of suitable quality for optimum results. Efficient stripping of the richoil requires the medium to be at a sufficiently high temperature (usuallyabout 120 0 C.) by heat exchange and closed steam before entering the still,
190. THE COKE OVEN MANAGERS’ YEAR-BOOKwhere open steam completes the process of debenzolising. These matterswere dealt with in some detail, attention also being devoted to steamsupplies and economies made possible by the use of exhaust steam, whereavailable. Other topics considered were conditions for the optimumrecovery of toluene, the testing of debenzolised oil, and the examination ofmethods for assessment of benzole slip.The paper led to a most useful discussion at both Sheffield and Cardiff,as the pages of the 1943 Year-Book show.PART IIAmong the war-time C.O.M.A. papers on benzole was a lengthycontribution by Mr. O.B. Wilson (Manager at Clay Cross coking plant,near Chesterfield, Derbyshire) entitled “Increasing the Make of Benzole”,presented to the Midland Section at a meeting in Sheffield on 21 February1940. Although this paper was preprinted (the present writer recalls havinga copy in his possession) and also appeared, in part, in The Gas WorldCoking Section for March and April 1940, it was not subsequentlypublished in the Year-Book. However, a modified version of the paper,under the title “Searching for more Benzole” was published by the authorin <strong>Coke</strong> and Smokeless-Fuel Age for May and June 1943, and the lattertwo sources have been used to prepare the following notes. The kindassistance of the Institution of Gas Engineers in providing relevant copiesof The Gas World Coking Section is gratefully acknowledged.The author first considered the quality of coal charged to the ovens,noting that water and ash present in the slack could not make anycontribution to benzole production. He then outlined the process operatedat his works for reducing both ash and moisture in the washed coal chargedto the ovens. The process concerned removal and recovery of the finesolids (less than about ½ mm.) from the coal washery water, which enabledcleaner water to be fed to the washery system and resulted in a betterseparation of the coal from the dirt present in the raw material. Theprocedure adopted by the author was to treat the effluent water from thewashery with starch and lime solutions to give a pH of 9.5. Thiscombination of reagents and alkalinity ensured rapid flocculation andprecipitation of the fine particles in settling tanks, from which a slurry waswithdrawn and dewatered on a vacuum filter. The clean water overflowing
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CHAIRMAN'S ADDRESS - Coke Oven Managers Association

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