» Modification of Black Liquor Properties
for Improved Chemical Recovery Efficiency
Nature
of Evaporator Scale |
In depth studies were conducted to
find the reasons of evaporator scaling and boiler deposits formation in the
chemical recovery section. Number of scales and deposit samples collected
from different mills based on single wood species, agro residues, bamboo,
combination of wood and bagasse etc. clearly revealed that the prominent
reasons responsible for evaporator scaling are the build up of fibres,
silica, calcium and at times the burkeite deposits, which indicates that the
operating condition are required to be monitored individually for different
mills with respect to evaporator scaling.
The results of the
studies have been communicated to the mills, which are found to be very
informative and useful in controlling evaporator scalings in the mills.
Studies conducted on recovery boiler deposit formation have clearly shown
that in case of mills having frequent deposit formation, the accumulation of
potassium and chlorides is one of the prime reasons of deposit accumulation
as with increased system closures, the purge points are getting reduced,
which leads to increased build up of these non- process elements in the
recovery boiler.
The reasons for corrosion in the recovery boiler,
colloidal instability of the black liquors in evaporators at substantially
low black liquor solids concentrations and poor burning behaviour of the
black liquor , etc. were explored. Process optimization studies were also
taken up for mills based on agro based raw materials and proposing to adopt
an integrated system by incorporating a suitable chemical recovery system at
their mill site. The reports along with the observations have been sent to
the respective mills.
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