CHAIRMAN'S ADDRESS - Coke Oven Managers Association

196. THE COKE OVEN MANAGERS’ YEAR-BOOKremoves unsaturated hydrocarbons present and reduces the yield of motorbenzole.The author referred to the Manvers Main plant designed for thetreatment of acid tar (W.F. Carr, T.G. Woodhouse and W. Green,B.P. 501,077 (1937)). In this process, the tar is agitated with steam torecover the entrained benzole, and then a dilute acid suitable for use in thesulphate plant is run off. Finally, the residue of resinous material is drainedwhilst hot into a shallow tray, where it sets into a brittle solid and can bebroken up for disposal.Tests on plants using this boiling-up technique had shown that asurprisingly large amount of spirit was recovered, and this could be furtheraugmented if soda and water run off from the washer were also treated inthe system, which proved an economical method of disposing of a difficultwaste product.To conclude his review of the refining processes and the theme ofincreasing the make of benzole, the author referred to the inhibitor process,which aims to conserve the unsaturated hydrocarbons present in thebenzole. These compounds are valuable constituents of a motor fuel,provided that their gum-forming tendencies can be controlled.W.H. Hoffert and his colleagues of the National Benzole Associationobserved in laboratory studies some 65 years ago that the formation of gumfrom unsaturateds present in benzole occurs through an initial oxidationstep, and that the addition of quite small amounts (of the order of 0.01 to0.04%) of anti-oxidants would forestall the formation of gum. Theinhibitor can prevent oxidation almost completely for a limited time,known as the induction period, but as the anti-oxidant disappears gumformation then proceeds normally. However, induction periods of a year ormore proved possible by optimising the concentration and nature of theinhibitor, usually phenolic or cresolic in character. In practice, the inhibitoris added continuously during distillation to the benzole on its way tostorage. It is not necessary, therefore, to remove a major portion of theunsaturateds in order to produce a stable spirit, and by restricting acidwashingto the level necessary for thiophene reduction, improved yieldscould be obtained.