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US 3,944,462 AGranted
Coking of waste kraft pulping liquors at lowered pH
AssigneeTexaco Inc.
InventorsHoward V. Hess, Edward L. Cole, William F. Franz
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Abstract
The liquid phase coking of waste kraft pulping liquors can be effected with a shorter residence time in the coking means at lower temperature, and lower pressure by reducing the pH of such liquors by at least one pH unit before coking. Products are lower in malodorous organic sulfur components than those produced at a higher pH. The lowering of the pH is achieved by adding sulfur dioxide to the liquor either as free SO.sub.2 or as an aqueous solution of SO.sub.2.
Claims8
In combination in a process for treating alkaline Kraft pulping liquors, the steps of:
- flowing said liquors to an adsorbing zone and adding extraneous SO.sub.2 to said liquors in said zone to lower the pH thereof by at least one unit then coking said liquors in the liquid phase in the absence of air in a coking zone by heating to a temperature in the range of 450.degree. to 700.degree.F. under a pressure of about 1000 to about 3000 psig for 0.5 minutes to 6 hours thereby forming coke, gases including H.sub.2 S and an aqueous effluent;
- separating in a separating zone said coke from said effluent;
- burning said coke to produce said sulfur dioxide;
- adding lime and said H.sub.2 S to said effluent in a second absorbing zone to form new Kraft cooking liquor.
1 more element
Dependencies are inferred from the claim text.