GB837611A - Improvements in or relating to the manufacture of soap - Google Patents

Abstract

A process for washing soap comprises (a) continuously supplying soap and fresh lye or nigre to a vessel in which they are intimately mixed; (b) separating the soap from the lye or nigre, and then (c) recycling and remixing with the soap a portion of the separated lye or nigre which is at least equal in weight to, but preferably 3 or more times the weight of the quantity of fresh lye or nigre introduced. <PICT:0837611/III/1> The principle is illustrated in Fig. 1 which shows a layer of molten soap S floating on lye L, the soap being introduced through 3 and lye through 1. The soap and lye separate by gravity in countercurrent, soap being removed through 2 and lye enriched with glycerol through 4. Some of the separated lye, however, is recycled through 5 by pump 6 and reintroduced to the soap layer by diffuser 7, which mixes it with fresh lye entering through 1. Fig. 5 illustrates an arrangement of four washing units A, B, C, D, each of which contains a funnel 28 (see unit A) which really belongs to the unit following the one in which, for convenience, it is disposed. Thus, funnel 28 belongs to unit B. Fresh lye enters funnel 41 by conduit 27, while crude curd soap passes by line 29 to funnel 28. Lye in unit B is the richest in glycerol, so some is removed by means of pump 39 and line 30, while the rest is passed through mixer 37, which mixes it with the crude soap, and is thereby returned to unit B where it separates, the soap eventually spilling over into funnel 40 where it is later mixed with recycled lye from unit C. In this way the soap finds its way in turn from units B, C, and D to A, in each unit being washed with lye which passes in turn from units D, C, and B to A, i.e. the soap and lye flow in countercurrent. The quantity of lye recycled in each unit is controlled by interfacial floats such as 33, 36 which operate valves 32, 35. Soap which finds its way eventually into the last unit A rises to the top on separating and overflows into gutter 42, whence it is removed (see also Fig. 6). Nigre, if used, is suitable only for the later stages of a multistage process, when the amount of glycerol has been reduced to the level normally present in nigre. Specifications 612,014 and 623,224 are referred to.