Chemicals, Paint & Ink
Keep tanks covered to minimise
evaporation
Covering tanks is common practice but it
must be done well to be effective. Plastic covers kept on with
elastic are the best option.
Switch off extraction when its not needed
Extraction is often necessary for safety reasons, to protect
operators and the internal environment of the factory. Extraction
from tanks containing solvent-based products such as paint is
needed during dispensing of powders and during agitation. At other
times it only serves to increase evaporation losses. Therefore,
switch off extraction and stirring when not strictly necessary.
Keep agitation time of paint tanks to a
minimum
Agitation puts energy into the tank, increasing temperature and
hence evaporation. Constant agitation results in considerable
losses. Agitation should be reduced to a minimum consistent with
avoiding separation.
Dilute to the middle of the solids range
Solids content, the expensive part of most paints and inks, is
often given away to customers by under diluting in the final
stages. Adding a bit more solvent at the dilution stage may help
increase output by 0.5-1 % at marginal cost.
One-way valves can prevent fallback of
materials
Suction pipes are often used for lifting liquids from drums. Where
the pump is higher than the drum, the liquid will inevitably fall
back into the drum from the pipe, with a loss of up to 1-2 kg per
operation. A one-way valve will prevent the fall back; the liquid
in the tube can be recovered by lifting the pipe higher than the
pump.
Reduce the numbers of transfers per batch
In paint and ink production batch size is often less than finished
batch size, since large batches are often made out of several small
mill bases, each of which may use several tanks. Reducing the
number of mobiles used per batch reduces yield losses and dirty
solvent generation.
Milling waste is valuable waste
A kilogram of product wasted at the milling stage can be worth
twice as much as a kilogram wasted at filling.
Check intermediate process yields
Many chemical processes are multistage reactions. Ensure
consistency of yield and batch sizes throughout the process. This
can significantly improve downstream efficiency and consistency,
and reduce waste significantly.
Reduce solvent waste in cleaning
mills
Trials have shown that the best way to clean a
mill is to wash out at the end of milling with at least three
system-volumes of batch solvent, passing it into the batch. This
leaves the mill clean enough to require a pre-wash of only one
system-volume. More of the solvent and product ends up in the batch
and less in the waste.
Contacts
Chemical Industries Association (CIA) Scotland
13 Northumberland Street,
Edinburgh
EH3 6LL
Tel: 0131 557 4321
Institute of Chemical Engineers (IChemE)
Website includes information on training, membership services,
diary of events, information, affiliated sites and safety and the
environment.
165-289 Railway Terrace
Rugby
CV21 3HQ
Tel: 01788 578214
Website: www.icheme.org 