ZERMEG II – Zero emission retrofitting method ... - Fabrik der Zukunft

With the existing rinsing configuration of one two stage rinsing cascade after pickling andone after anodising, the actual amount of rinsing water, for the desired rinsing criterion, is alot higher than theoretically necessary. By concentration profile measurements in the rinsesit could be shown that due to the high density of the media and the partially badlyfunctioning circulation of the rinses (through compressed air) a pronounced concentrationprofile exists in the rinses. By stronger bath circulation with compressed air and theintroduction of a constant circulation also during production stops a clear improvement inform of a reduction of the concentration differences could be achieved.In the anodising baths a significantly increased consumption of sulphuric acid could be seencomparing to ideal consumptions. The retardation plant for the extraction of dissolvedaluminium could be identified as the cause. The retardation plant is based on the principle ofthe different surface absorption of sulphuric acid and aluminium on a resin. This resin wasvery old at the beginning of the work. After it had been replaced, a clear improvement of theperformance of the plant could be achieved, which led to a clearly reduced acid discharge.Through these two measures it was possible to reduce sulfuric acid by more than 30 %.The evaporating water quantities were calculated depending on the temperature and airspeeds in the hall. It was shown that with the quantities of water used currently, theevaporation from the baths contributes only to a small part of water consumption. To recyclewater from the first rinsing stage to the baths could only help as a sink for rinsing water if atenfold reduction of the fresh water consumption could be achieved.In order to reduce the huge quantities of cooling water to keep the temperature of theanodising baths within the required range, a closed cooling cycle with integratedrefrigerators was designed. Due to this measure the cooling water quantity was decoupledfrom the amount of rinsing water. Thus an adjustable, controlled amount of rinse water wasthe result. The necessary investment was 100,000 €. The savings from the reduction inwater consumption calcuted to 30.000 €/year based on the increased production.This does not consider the capacity increase and the quality improvement. Meanwhile thetotal specific water consumption could be reduced to less than 40 l/m².A systematic approach to describe and define Errors in the starting material Errors with the mechanical pre-treatment Pickling and rinsing errorswas developed in order to more exactly allocate errors and identify appropriate strategies fortheir prevention. Previously the first response to any quality problems always had been toincrease the water flow in rinsing. This knowledge serves also as basis for additional trainingactivities in the enterprise and considerations for the control automation of the water flowthrough the rinses.19