Operating costs
Diaphragm filtration plants run fully automatically. All of
the relevant operating parameters, such as the temperature, flow rate,
operating pressure etc., are controlled via PLC. Back-flushing processes and cleaning processes are started automatically.
The initial investment for ceramic diaphragms is higher than
for polymer diaphragms. Thanks to their high temperature resistance and
chemical resistance, their lifetime is between 5 -10 years (note: Van Clewe /D
> 8 years). Conventional polymer diaphragms are used in the reverse osmosis
stage, and these have a lifetime of 2 - 3 years. The operating costs for a two-stage
diaphragm system are around 0.60 /m3, which includes both the initial
investment costs and the running costs of the plant. The amortisation period
for a diaphragm system for textile waste water is around 2 - 3 years for water
recycling and heat recovery. If the system is also used to recycle size and
recover caustic soda then the amortisation period is around 1 - 2 years.
However, rising energy costs and the increased shortage of
water will significantly reduce the amortisation period in future.
Solutions for passive and active protection against
emissions
There is no getting away from the image of textile finishing
being a major contributor to emissions. Even in the long term, it is not going
to be possible to replace wet chemical methods with physical methods. This is
reason enough to start looking for ways to reduce emissions. So what options
for passive and active protection against emissions are available?
Passive options include:
- Process changes, e.g. continuous dyeing instead of JET
treatments
- Optimisation of existing processes and recipes
- Use of highly efficient washing and finishing
technologies.
The list of active options includes the use of filtration
technology to recover water, energy and recyclable materials from the waste
water of wet finishing plants. For the first time, the ceramic diaphragms used
in the ultrafiltration stage enable reliable and continuous operation for the
treatment of waste water from textile finishing processes. At the same time,
they also act as a protective buffer for the downstream reverse osmosis stage,
which is used for filtration of dissolved dyestuffs and electrolytes. As well
as the recovery of water, energy and recyclable materials, the use of an
evaporator and an evaporation plant makes it possible to run textile finishing
plants which generate no waste water at all.
About the Author:
The author
is associated with Benninger AG Uzwil (CH).
