UNHAIRING TECHNOLOGY INVOLVING HAIR PROTECTION ADAPTATION OF A RECIRCULATION TECHNIQUE

The application of the hair-saving process has mainly resulted in a re duction of the organic content and suspended-settleable solids in the beamhouse effluent. Aiming at decreasing the volume of effluents from unhairing and at optimizing the amount of products used in such a proc ess in a tannery producing upholstery leather, a study concerning recy cling was made of the effluents from a hair-saving ''chemical unhairin g'' process that is in current use. By means of trials both at laborat ory scale and on a pilot plant, the recirculation of an effluent (''mi xed liquor'')-including unhairing liquid wastes and waste water from t he first discontinuous washing-was used at the stages of alkaline cond itioning, hair immunization, unhairing and liming. Fifteen unhairing t rials were performed at the CITEC's pilot plant with 7 bovine hides in each cycle; when the pelt stage was reached, the process was continue d at the tannery. The results obtained led to the following conclusion s: an adaptation of the recycling technique to a hair-saving process i s applicable at the liming, immunization and unhairing stages; the fea tures of the ''re-circulated leather'' are similar to those of the fin ished upholstery product made by the tannery; this recycling technique allows for an 88% reduction in the volume of unhairing wastes and for 43 and 20% reduction in the consumption of lime and sodium sulphide, respectively.