ISSN 1070-4272, Russian Journal of Applied Chemistry, 2016, Vol. 89, No. 5, pp. 787í792. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © V.G. Kazakov, P.V. Lukanin, O.V. Fedorova, D.E. Samoilenko, 2016, published in Zhurnal Prikladnoi Khimii, 2016, Vol. 89, No. 5, pp. 654í659.
AND POLYMERIC MATERIALS
Improvement of the Technology for Reprocessing
Black Liquors from Kraft Pulp Production
V. G. Kazakov, P. V. Lukanin, O. V. Fedorova*, and D. E. Samoilenko
Saint Petersburg State Technological University of Plant Polymers, ul. Ivana Chernykh 4, St. Petersburg, 198095 Russia
State University of Industrial Technologies and Design, ul. Bol’shaya Morskaya 18, St. Petersburg, 191186 Russia
* e-mail: email@example.com
Received April 29, 2016
Abstract—A way to improve the kraft pulp production process via acid–base treatment of black liquor was sug-
gested. Data on the process for kraft lignin production by the sulfuric acid procedure were substantiated.
The existing procedure for kraft pulp production is
characterized by high environmental hazard and low
power efﬁ ciency . Black liquor reprocessing followed
by recovery of alkalis deteriorates the quality of the
environment. This drawback of the process is often the
cause of decommissioning of pulp plants. Therefore,
this process requires improvement.
One of the main distinctive features of the process
that we suggest is removal of lignin and other organic
compounds before evaporation of weak black liquor.
Two methods for lignin precipitation are known:
treatment with sulfuric acid and with carbon dioxide .
The carbon dioxide method is based on acidiﬁ cation of
black liquor with carbon dioxide:
NaO–R–COONa + CO
ĺ HO–R–COOH + Na
In the carbon dioxide method for precipitation of
organic compounds, their yield does not exceed 30%.
The yield of organic compounds can be increased to
70% by saturation of the black liquor with carbon
dioxide under pressure. The authors of  suggest
a procedure for black liquor treatment with carbon
dioxide present in ﬂ ue gases from decarbonization
furnaces. However, the process implementation is thus
complicated. By carbon dioxide treatment, it is possible
to recover organic compounds when large circulation
streams of the black liquor are organized. The soda
recovery boiler (SRB) as the main source of capital and
power expenditures can be eliminated from the chain
of the apparatuses. However, problems of the power
efﬁ ciency and environmental safety of the technology
in the lime decarbonization process are not solved.
Preservation of lime as the agent for caustization of the
soda solution in the carbon dioxide process gives rise to
problems in the course of solution evaporation. Sodium
sulfates and carbonates and calcium sulfates formed in
the process incrust the heat-exchange surface at elevated
temperatures, decreasing the efﬁ ciency of the black
Sulfuric acid as a strong acid allows more complete
precipitation of lignin from black liquor:
NaO–R–COONa + H
ĺ HO–R–COOH + Na
A process for recovering organic compounds, based
on treatment of black liquor with sulfuric acid to pH 4,
has been developed .
However, this procedure has limitations with respect
to the amount of the black liquor being treated. This is
apparently caused by the following factors: (1) large
amounts of sodium sulfate are formed, and the sodium
sulfate stream is difﬁ cult to convert to demanded