The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 26, 1997
Filed:
Nov. 21, 1994
Bengt Nilsson, Skoghall, SE;
Chemrec Aktiebolag, Karlstad, SE;
Abstract
A method of preparing a digesting liquor having high sulphidity from a spent liquor obtained from digesting cellulosic fiber material, optionally without a conventional causticizing step is provided. Thermal decomposition of the spent liquor is conducted under reducing conditions in a reactor at a pressure of from atmospheric pressure up to about 150 bar and at a temperature of about 500.degree. to 1600.degree. C. so that a combustible gas phase containing hydrogen sulphide is formed in the reactor and extracted therefrom, and a phase of solid or molten material of substantially sodium sulphide or potassium sulphide, or mixtures thereof. The solid or molten material is dissolved in an aqueous liquid to produce said digesting liquor. The invention hydrogen sulphide is recovered from the gas phase and returned to the reactor to be present during the thermal decomposition of the spent liquor.