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PIGMENT QUESTION



Dear P2Tech,

I got the request below and was wondering if anyone could help.  I spent
about 2 hours on the web and found little infomration on pigments.  Any help
would be greatly appreciated!

Dear UNEP,

Can you help me with the following?

Information on the above-referenced facility: 
Name: C.S. Pigmenti S.A. 
Products: inorganic pigments (used, for example, to make paints, at another
facility), filling materials, additives for plastic production 
Employees: 300 
Process Profile 
synthesis of inorganic pigments: 
1) precipitation pigments: chromium yellow, chromium green, iron blue, black
iron oxide, zinc chromate, chromium phosphate, zinc phosphate 
2) calcination pigments: green chromium oxide, brownish iron oxide 
The plant is only operating at about 15 to 20 % of design capacity since
1990. In 1997, the plant produced 1,255 tons of inorganic pigments, about 50
% of which was brownish iron oxide; 119 tons of zinc chromate; and 43 tons
of green chromium oxide. The inorganic pigments are the main concern for
this study, especially concerning the chromium containing pigments. Chromium
is the main contaminant in the waste water. 
A 'CP' audit was implemented at the facility in early November 1998. The
process for green chromium oxide, the principle process under study,
consists of the following steps: 
- grinding of raw materials (including sodium bichromate - Na2Cr2O7) 
- homogenization (mixing) of raw materials 
- calcination & oxidation 
- washing and decantation 
- filtration 
- drying 
- sizing (grinding) of product 
- separation of product by size 
- packaging 
About 50 % of the energy consumption was attributed to the air compressors
discharging at 6 to 7 atmospheres pressure (air is heated and used to dry
the pigments). This represents an opportunity for energy savings. 
Pigmenti management is interested in a new process that has been installed
at a pigments plant in Hungary ('Tiszamenti Vegyimuvek Szolnok'), which was
visited by Pigmenti managers. The principal change is that it reduces the
use of sodium bichromate, and runs under alkaline (rather than acidic)
conditions, using sodium hydroxide (NaOH). The new process dramatically
reduces water consumption (by about 60 %). 

The new process requires a new reactor. However, no contact has been
possible with the Hungarian facility, and so the technical feasibility of
the new process cannot be confirmed. 

It would be great if anyone has heard of this new process, as it seems to be
very advantageous (that is, relatively short payback period). Otherwise,
what other CP measures have been applied at a facility like this one, other
than energy savings? 

Please let me know if you have any questions.