Chemistry: natural resins or derivatives; peptides or proteins; – Natural resins or derivatives – Recovery of tall oil or derivatives from papermaking waste,...
Patent
1996-11-29
1999-04-06
Killos, Paul J.
Chemistry: natural resins or derivatives; peptides or proteins;
Natural resins or derivatives
Recovery of tall oil or derivatives from papermaking waste,...
554157, C09F 100, C07C 5100
Patent
active
058919902
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 stage in which a mixture of tall oil soap and water is neutralized with carbon dioxide, a water separation stage in which the aqueous phase containing bicarbonate is separated from the soap, and a cooking stage in which the soap obtained from the preceding stage 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 stages presented above.
In the alkaline digestion of softwood, 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 at the beginning of the present specification, based on carbon dioxide neutralization, is known from U.S. Pat. No. 3,901,869. In the first stage of this known process, a neutralization with carbon dioxide is carried out. After this stage, 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 7.5-8.0.
In terms of the separation of the inorganic phase and the organic phase, the pH should be lowered 0.5-1.0 units, 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.
An object of the invention is to improve the separation of the bicarbonate-containing aqueous phase in the water-separation stage after the neutralization with CO.sub.2.
The principal characteristics of the invention are given in the accompanying claims.
The invention is based on the realization that, when a second neutralization with an addition of H.sub.2 SO.sub.4 is carried out after the neutralization with CO.sub.2, the separation of water in the water-separation stage is considerably improved. With an addition of H.sub.2 SO.sub.4 the pH is lowered by approx. 0.5-1 pH units, to an optimum pH range of approx. 7.2-7.6. The adding of sulfuric acid is done according to the pH.
The sulfuric acid is added into an unpressurized reactor, which is located at a point after the carbon dioxide neutralization reactor or reactors, before the separation vessel.
The CO.sub.2 neutralization can be carried out under normal pressure or under overpressure. The carbon dioxide used is preferably gaseous carbon dioxide.
DESCRIPTION OF THE DRAWING
The invention is described below in greater detail, with reference to the accompanying drawing, which is a block diagram of the tall oil preparation process according to the invention.
Crude soap and water are pumped into the CO.sub.2 neutralization reactor, and gaseous CO.sub.2 is introduced into it to neutralize the mixture. The mixture of soap and water is fed into the H.sub.2 SO.sub.4 neutralization reactor, into which sulfuric acid is fed for further neutralization of the mixture of soap and water. Next, the soap is fed into the separation vessel, in which the bicarbonate brine is separated from the soap. Finally, the soap is fed into the tall oil cooker, in which acidification with sulfuric acid is performed, whereupon crude tall oil is obtained.
Example
The experiments were performed in a 2-liter autoclave. A batch was prepared which contained 500 g of s
REFERENCES:
patent: 3901869 (1975-08-01), Bills
Chem. Abs. 120: 79894 (SU 1,766904A1) Jul. 10, 1992.
Raimo Alen, "Sulfaattikeitossa sivutuotteina syntyvien alifaattisten karboksyylihappojen hyodyntaminen", Kemia-Kemi, vol. 15, No. 6, pp. 565-569 (1988).
Rouvinen Tellervo
Varila Elias
Killos Paul J.
l'Air Liquide, Societe Anonyme pour l'Etude et Exploitation des
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