FACTORS AFFECTING DEPOSIT FORMATION IN FOUL CONDENSATE STRIPPING SYSTEMS

ABSTRACT
In kraft pulp mills, foul condensates are often steam-stripped to produce clean condensate for use
as process water. The formation of organic deposits in the stripped condensate is a common
problem. A systematic study was conducted to examine the deposit composition and the most
likely operating parameters responsible for stripped condensate contamination in a kraft mill in
Brazil. Daily averaged data of 170 operating parameters over a 15-month period were analyzed
by means of multivariate discriminant analysis and random forest classification analysis. The
results show that the deposit formation is related to high temperature, pressure and dry solids
operations in various evaporator effects. These conditions, combined with the poor demisting
efficiency in these effects, may have increased black liquor carryover mist in the vapor. Deposit
formation appeared to be also related to increased throughput of the foul condensate stripping
system, as well as increased pressure in the stripper. Results of FTIR and Py-GCMS analyses
show that the deposit consists of mostly organic matter that likely originated from wood extractives
and lignin.
Keywords: Foul Condensate, Stripper, Evaporators, Precipitate, Residue, Liquor Carryover. 

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