Evaporation Plant for Recycling of Caustic Soda

Yıl 2017, Cilt: 3 Sayı: 3, 176 - 185, 26.09.2017

Emin Taner Elmas

https://doi.org/10.19072/ijet.331578

Cited By: 1

Öz

     The most important problem that humanity
is expected to face in the coming century shall be environmental pollution. On
one hand, the population  of human beings
are using natural resources rapidly, on the other hand, they are adding
hundreds of pollutants in the form of metals, acids, bases and etc. Thus, they
have created an abnormal situation which 
has resulted in an imbalance in the natural systems.

    As the industrialization improves, it
creates pollution and also it creates jobs for the people. Especially in
developed countries, for instance European countries and U.S.A. there are also
many stringent restrictions for the environmental pollution, and there are many
laws, political arrangements. Of course , a pollution free environment will
require a high cost, often an expensive operation. However , it is much more
costlier trying to undo the damage done.

     On the basis of concept tried to mention
above human beings have studied on the subjects related with environmental
pollution. They have established waste water treatment plants, many kinds of
recycling and recovery plants, and etc.

     In this study , it has been tried to
establish such an idea that a pollution free environment may be available if
this  technical process is used properly.

     So, the first goal of this study is to
provide a concise statement of the requirements and opportunities for obtaining
environmental benefits.

     The second objective will be to provide
economical savings while providing the environmental benefits at the same time.

     To emphasize the great importance of above
mentioned subjects the application of recycle technology for the sodium
hydroxide (NaOH), which is named as caustic soda in industrial processes,
realized by means of an evaporation plant is used.

     Caustic soda is used in textile industry
for mercerizing process as it is used in many different processes. To give the
cotton more strength and to obtain a smoother surface and an improved affinity
the mercerizing is essential. After being finished the mercerizing operation,
generally the process solution (containing caustic soda) is discharged to the
environment,. e.g. , rivers, seas and sewage.

     In spite of the fact that this application
is widely spread in use, it is forbidden in all developed countries to
discharge the caustic soda solutions even at a 1% concentration since the
caustic soda is highly basic (highly alkaline). For this reason it is very
harmful for the environment.

     It is possible to extract the caustic soda
from the caustic soda solutions before discharging it to the environment for
preventing the harms of this material.

     The washing water containing NaOH will be
concentrated by H₂O evaporation and shall be recycled in the
mercerizing system. The concentration may take place in a single or multiple –
stage (double–stage) installation under vacuum or atmospheric pressure.

     The washing water to be concentrated is
moved from the storage tank to the first evaporation stage and the thermal
energy for evaporation operation is added by the steam. The vapor  coming from the first evaporation stage is
used for the next evaporation stage as the heating steam of this unit. The
vapor from the last stage is condensed in a condenser. The condensed vapor can
be safely discharged and the concentrated caustic soda can be reused for the
subsequent mercerizing operation. So, both economical profits and environmental
benefits can be provided by reusing the caustic soda for next processes , after
it is recovered by the help of this way.

     Desalination unit in Jeddah which is the
capital city of Saudi Arabia , is an example for this kind of operations.. This
plant was established 1970’s and has been used as both a power station and a
desalination unit. At this plant the exhaust steam coming from the steam
turbines is used as the heating steam for evaporators of desalination unit.

     Unfortunately, in our country, even in
İzmir, the waste water of textile industry is discharged to the environment.
Because ,  the  environmental laws are not adequate and the
enterprisers think that a recycling plant is not an economical investment.
However , it is  stated in this  study that such a  concept is not right.

     It has been  tried to show that such an investment, i.e.,
“An Evaporation Plant for Recycling of Caustic Soda” may be profitable if it is
installed and operated properly, and also it has been  tried to increase the attractivity of these
kinds of plants .

     It is hoped that, the laws and stringent
restrictions related with environment shall be arranged, so that  we shall live in a healthy world.

Anahtar Kelimeler

Evaporation, Recycling, Caustic soda, Sodium hydroxide, Vacuum, Steam

Kaynakça

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