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environment was reduced by 32.2 % in comparison with use of the classic process impact, which represents

100 % of impact. Such good results were achieved mainly by the elimination of the node of reduction of

sodium dichromate (VI) by using sulphur dioxide. Analysis of data from Table 1 allowed one to state that

besides the technology modification, there is also the need for the modification of equipment used in the


The emission of chromium compounds in fumes after the drying should be especially reduced, e. g. by using

a second stage of cleaning of after-drying gases. This, however, will require further studies and analysis and is

also closely connected with the amount and quality of liquid waste from production, a problem which also

needs to be solved. Recycling of liquid waste containing chromium (III) is, in this case, difficult because of the

high quality requirements of chromal regarding solubility or iron content in the final product.

Waste [kg/ton of product]

No Process phases

FORUM WARE 32 (2004) NR. 1 - 4

gaseous waste (air emissions) liquid waste

SO2 CO2 H2O NOX chromal

in fumes

H2SO4 Na2Cr2O7 glycol chromal

1. Transportation and storage of

raw materials

0.1 0.26 0.1 0.26


Mixing of the sodium

dichromate with H2SO4 and

cooling of the mixture

3. Reduction of Cr(VI) and


4. Pumping and spray drying 7.72 11.36

5. Transportation and packaging

6. Dry dedusting

7. Wet dedusting 0.02 400 100 0.04 12.20

8. Cumulated hazard index WS 0.02 400 100 0.04 12.20 0.1 0.26 0.1 0.26

9. Toxic coefficient K 3.89 0.002 3.89 69.05 4.85 3341.1 12.73 982.75


Cumulated hazard index

which allows for the toxic

coefficients WSk

0.078 0.8 0.156 842.41 0.485 868.69 1.273 255.515

11. Cumulated total hazard

coefficient GWS


Tab. 2: Data for GWS calculation of chromal production – modernised technology

Source: authors own calculation


Evaluation of the modernisation of the chromal tanning agent production process using the method of

process analysis in terms of cumulated calculation confirms the expected high reduction of negative impact on

the environment.

In the case of modified technology of chromal production, the relative coefficient of decrease of the hazard

to the natural environment WZZ will be 32.2 % lower than that created by the classic production method used,

which was assumed to be 100 % of the impact. Additionally, in the new technology there will be no solid

waste release. The modified technology will also be more effective than the classic one due to cost reduction,

resulting from the simplification of the process and lowering its energy- and labour-consumption.

The analysis performed using the method of cumulated calculation allowed one to identify the main source

of environmental hazard caused by the chromal production process. Consequently the proposals for

modification of equipment used in the process were presented, especially the reduction of emissions of

chromium compounds in the fumes, after the drying node by using a second stage of cleaning of after-drying


* Zygmunt KOWALSKY, Michal KONOPKA , Cracow University of Technology, Institute of Chemistry and Inorganic

Technology, Warszawska 24, 31–015 Krakow, Poland

** Joanna KULCZYCKA, Anna HENCLIK, Polish Academy of Sciences Wybickiego, Institute of Mineral and Energy Economy

Research, Wybickiego 7, 31–261 Krakow, Poland, Tel.: +48 12 632 22 45, Fax: +48 12 632 22 45,



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