Chemistry: natural resins or derivatives; peptides or proteins; – Natural resins or derivatives – Recovery of tall oil or derivatives from papermaking waste,...
Patent
1998-01-26
1999-04-27
Nutter, Nathan M.
Chemistry: natural resins or derivatives; peptides or proteins;
Natural resins or derivatives
Recovery of tall oil or derivatives from papermaking waste,...
530206, 530208, C09F 1001, C11B 1302
Patent
active
058980652
DESCRIPTION:
BRIEF SUMMARY
The object of the present invention is a method for improving the separation of water in a tall oil preparation process comprising a neutralization step in which a mixture of tall oil soap and water is neutralized with carbon dioxide, a water separation step in which the aqueous phase containing bicarbonate is separated from the tall oil soap, and a cooking step in which the soap obtained from the preceding step is cooked with sulfuric acid to form tall oil. The invention also relates to a method for the preparation of tall oil, the method comprising the steps stated above.
In the alkaline digestion of softwood or hardwood, especially in the sulfate process, so-called black liquor is formed which contains crude tall oil soap, hereinafter called crude soap. This crude soap can be decomposed with sulfuric acid to form crude tall oil.
A tall oil preparation process of the type stated in the beginning of the present specification, based on carbon dioxide neutralization, is known from U.S. Pat. No. 3,901,869. In the first step of this known process, a neutralization with carbon dioxide is carried out. After this step, water is separated, and finally a tall oil cook with sulfuric acid is performed.
When crude soap is treated with carbon dioxide, the carbon dioxide dissolves in the soap-water emulsion, and the formed carbonic acid neutralizes the soap and the lye accompanying it. The neutralization lowers the pH of the soap-water mixture to a range of 7.5-8.2.
In terms of the separation of the inorganic phase and the organic phase, the pH should be lowered by 0.2-1.0 unit, but without using an excess of carbon dioxide, which would result in effervescence. In terms of the economy of the process, a maximally high efficiency of the use of carbon dioxide is a key factor.
A problem in the state-of-the-art technology is thus poor separation of water. Poor separation of water results in that too much sulfuric acid is consumed in the further cook and the excess water unnecessarily expands the process cycles. The excess CO.sub.2 -containing water also causes effervescence in the cook with sulfuric acid, since bicarbonate decomposes during the cook.
The applicant's previous patent application FI-940969 discloses a method in which a second neutralization with an addition of H.sub.2 SO.sub.4 is carried out after the neutralization with carbon dioxide. By this procedure it was possible to improve the separation of tall oil soap in the water separation step as compared with a method in which an intermediate neutralization with sulfuric acid was not carried out. However, this method still has the deficiency that the separation water is not completely sufficient.
An object of the invention is a method by means of which the separation of an aqueous phase containing bicarbonate in the water separation step following the neutralization with CO.sub.2 can be improved.
The principal characteristics of the invention are given in the accompanying claims.
In accordance with the invention, after the neutralization with carbon dioxide but before the water separation step, the pH is thus adjusted using an acidically reacting substance, provided, however, that this substance is not sulfuric acid alone. Thereby the separation of water is considerably improved as compared with a method in which such pH adjustment is not carried out, and is improved even as compared with a method in which intermediate neutralization with only sulfuric acid is carried out.
With an addition of an acidically reacting substance, the pH is lowered by approx. 0.2-1 pH unit, to an optimum pH range of approx. 7.0-8.0. The adding is done according to the pH.
When carried out in excess, pH adjustment releases an excess of fatty acids, in which case the fatty acids will act as emulsifiers, and tall oil soap will become slurried in the mother liquor.
Suitable acidically reacting substances include bisulfite, sulfur dioxide, hydrochloric acid, nitric acid, and carboxylic acids such as formic acid, as well as mixtures thereof. The acidically reacting substance used may also
REFERENCES:
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patent: 5286845 (1994-02-01), Huibers et al.
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TkT Raimo Alen, "Sulfaattikeitossa sivutuotteina syntyvien alifaattisten karboksyylihappojen hyodyntaminen", Kemia-Kemi, vol. 15 (1988) 6, pp. 565-569.
V.C. Uloth et al, "Crude Spent Sulphite Liquor as Soap Acidulation Additives to Improve Efficiency of Tall Oil Production," Pulp & Paper Canada, 85:5 (1984), pp. 69-71.
Aitta Eero
Varila Elias
L'Air Liquide Societe Anonyme pour l'Etude et, l'Exploitation de
Nutter Nathan M.
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