Patent GB-283614-A (GB)
Title: Methods of, and apparatus for, removing, purifying and recovering oil from tin plate
IPC: C23G3/00
Filed: 1926-09-13
Abstract: 283,614. Ellis, G. B., (American Sheet & Tin Plate Co.). Sept. 13, 1926, Purifying fats and oils; recovering fats and oils from waste waters.-Oil, such as palm oil, is removed from tinned plates by washing, as with an alkaline solution to form an emulsion, the oil is separated from the bulk of the water, as by breaking the emulsion by addition of acid and the action of heat, and the separated oil is heated to vaporize and remove any remaining water before being returned to the tinning-pot for further use after removal, if desired, of foreign matters such as ash-forming material and tin particles, as by passage through a centrifuge. Sludge from the centrifuge may be furnaced for recovery of its tin content. As shown in Figs. 1 and 2, tinned plates from a pot A, after passage through a body of palm oil 9, are fed into a washing-tank C filled wih a hot soda ash solution and supplied constantly with water from a pipe 12 and with further soda ash as required. The plates are passed through the solution by pairs of rolls 15, 16, the lower roll of the first pair and the upper roll of the second pair being of smaller diameter and' having a greater surface speed than the remaining rolls and being fitted with a fabric or rubber covering 17, whereby the plates are scoured and freed from oil, and an emulsion of the latter with the solution formed. Similar pairs of rolls 19, 20, 21 serve to polish and dry the plates before they pass to a branner 24. Emulsion from the tank C, zinc chloride and other soluble impurities having passed from the oil into the aqueous solution, overflows through a pipe 29 and passes by a trough 31 into the heating and mixing chamber 33 of a tank D, where a measured quantity of sulphuric acid is added from a tank 42 by a pump 43, and into which steam is passed from a pipe 39 to heat the mixture to, say, 140‹ F. The emulsion, thus broken, overflows into a chamber 34<a> and separates by gravity, the oil rising to flow over the inclined top of a wall 35 into a chamber 35<a>, this action being assisted by a steam coil 38, and the water passing away by a pipe 45, the top of which is about 1¢ ins. below that of the wall 35. Acids other than sulphuric acid, nitre cake, waste pickle liquor, lime, calcium chloride, iron or sodium sulphate, or alum may alternatively be used to break the emulsion, but in some cases the oil then settles out with any precipitate formed and the water rises in the chamber 34<a>; or the emulsion may be broken by centrifugal means, or the oil be extracted therefrom by a solvent. The oil collecting in the chamber 35<a>, which contains about 60 per cent of water and is heated by a steam coil 41, is pumped on to a screen 48 which separates solid matter, and collects in a tank 50 fitted with a steam coil 51, from which it is pumped through a coil 54 located in a steam heated drying drum 55 which raises its temperature to 300' F., and vaporizes its water content before it is delivered to a stack 56. The water vapour passes up the stack, and the dry oil flows through tanks 59, 60, maintained at 300‹ F., to a centrifuge 62 for final purification.