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Mixed Sulfate Soap Washing with Neutralized Spent Acid

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E.V. Starzhinskaya, A.M. Kryazhev, A.A. Glukhanov, S.I. Tret’yakov

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Sulfate soap, being a valuable by-product of pulp production by the sulfate process, is a mixture of saponified resin and fatty acids and unsaponifiables (sterols, fatty alcohols, aliphatic hydrocarbons, etc.). Sulfate soap micelles enlarge and during surfacing may entrain a portion of black liquor containing dissolved lignin, as well as impurities of calcium compounds; when settling the liquor formed in pulp washing. The main method of removing black liquor is additional settling of sulfate soap prior its processing. It is reasonable and cost effective to use for washing a solution of salts formed in decomposition of soap or spent acid neutralized to pH = 8–14. The article shows the necessity of washing of sulfate soap obtained from different wood species in pulping. Neutralized spent acid received in soap decomposition was used as a washing solution in an amount of 10, 20, and 30 % of sulfate soap volume. Washing was carried out at a temperature of 20–80 °C. The optimal conditions for mixed sulfate soap washing were determined: temperature (20–40 °C), and flow rate of the washing solution (10–20 %). It was found that under optimal washing conditions of mixed sulfate soap with neutralized spent acid, the yield of crude tall oil and its acid number increase, the alkali and lignin content decrease, and the decrease of resin acids in tall oil is prevented.


E.V. Starzhinskaya1, Process Engineer; ResearcherID: E-2862-2019, ORCID: 0000-0002-4989-264X
A.M. Kryazhev2, Doctor of Engineering, Chief Technologist; ORCID: 0000-0002-3287-6387
S.I. Tret’yakov3, Candidate of Engineering, Prof.; ResearcherID: S-2192-2019, ORCID: 0000-0003-1783-5349
A.A. Glukhanov3, Candidate of Engineering, Assoc. Prof.


1LLC “Tekhservis”, ul. Sovetov, 4, of. 300, Novodvinsk, 164900, Russian Federation; e-mail:
2LLC “Advis Plus”, nab. Obvodnogo kanala, 150, korp. 363, of. 232, Saint Petersburg, 191011, Russian Federation; e-mail:
3Northern (Arctic) Federal University named after M.V. Lomonosov, Naberezhnaya Severnoy Dviny, 17, Arkhangelsk, 163002, Russian Federation; e-mail:


sulfate soap, tall oil, black liquor, lignin, soap washing

For citation

Starzhinskaya E.V., Kryazhev A.M., Tret’yakov S.I., Glukhanov A.A. Mixed Sulfate Soap Washing with Neutralized Spent Acid. Lesnoy Zhurnal [Forestry Journal], 2019, no. 5, pp. 194–202. DOI: 10.17238/issn0536-1036.2019.5.194


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Received on February 07, 2019

Mixed Sulfate Soap Washing with Neutralized Spent Acid


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