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the recovery efficiency ratio, it would be possible to obtain from 175,000 to 439,000 t of aluminium, which

could be used as a raw material for the remelting industry.

This information also confirms that a more detailed understanding of commodity composition could be

directly useful in waste management and could improve the use of different commodity components as raw

materials.

During our work, many difficulties were met in quantifying the amount of aluminium semis (extrudes, casts

and laminates) contained into the final commodities. However some interesting information resulted from this

analysis, such as the total aluminium contained in durable commodities equal to 60 % of available Italian

aluminium (1.7 Mt). Moreover, the few examples reported show the utility of the suggested analysis. Indeed,

only a small number of commodities (cars, scooters, computers, colour TVs and refrigerators) allowed for the

“interception” of more than 10 % of the total aluminium available in Italy (1.7 Mt) and between 30 % and

90 % of domestic scrap collection (more than 0.55 Mt). In our opinion these data are useful for a better scraps

knowledge and management and to increase the use of secondary raw materials while reducing energy

consumption and the amount of waste lost in landfill. From this point of view, a double role could be played

by Commodity Science. First of all, we could improve our knowledge of commodity composition,

characterisation and quality. Secondly, Commodity Science peculiarities could be used to organise a uniform

and homogenous commodity classification system which would open up to a real possibility of following,

intercepting and analysing the circulation of different materials in an economic system.

* Vera Amicarelli, Giovanni Lagioia, Ottilia De Marco Università degli Studi di Bari, Dipartimento di Scienze Geografiche e

Merceologiche, Via C. Rosalba, 53 – I-70124 Bari (Italy) Tel.: +39 0805049080 (82, 86), Fax: +390805049019,

E-mail: v.amicarelli@dgm.uniba.it

This work is the result of the authors’ commitment, starting from the idea and ending with its accomplishment. Particularly, each

author contributed as follows: Amicarelli 40 %, Lagioia 40 % and De Marco 20 %.

ENVIRONMENTAL EVALUATION OF MODERNISATION OF THE

CHROMIUM TANNING AGENT PROCESS

Zygmunt KOWALSKY * , Michal KONOPKA * , Joanna KULCZYCKA ** , Anna HENCLIK **

Keywords: Chromium, tanning agent, environmental evaluation, technology, technical progress

Modernised technology of the chromal production

The chromium tanning agent 2Cr(OH)SO4+Na2SO4 containing basic chromium(III) sulphate and sodium

sulphate (trade name chromal), is a standard chromium tanning agent produced currently by the reduction of

sodium dichromate(VI) solution by using sulphur dioxide. In this paper the results of the modification of this

process are presented. The goal of this work was to find a substitute for the reducer used (i.e. gaseous SO2)

with liquid reducing agents. Best results were achieved by using ethylene glycol as reducing agent of the

Cr(VI) to Cr(III) in the sodium dichromate(VI) solution. This alternative of the new technology (potentially

possible for future introduction) was chosen for environmental impact analysis, which was made on the

process analysis in terms of cumulated calculation.

The sodium dichromate (VI) solution remains the basic raw material of the process. Due to this, the

solution will be not diluted after sodium sulphate precipitation. Energy could be saved during further

evaporation of water by use of a spray dryer. The main change is the substitute of sulphur dioxide with

ethylene glycol as the reducer of Cr(VI) to Cr(III). The consequence of this is elimination of the nodes of

obtaining of SO2 from powder sulphur and reduction of sodium chromate (VI) with sulphur dioxide.

Comparison of the environmental impact of the chromal production methods

The environmental assessment of chromal production process modernisation was made on the basis of the

process analysis in terms of cumulated calculation. Process analysis allowed the assessment of environmental

results of chromal technology modernisation (Tab.1). The hazard impact of this process on the natural

FORUM WARE 32 (2004) NR. 1 - 4

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