Process for treating waste liquors

Abstract

Abstract Closed circuit process for treating waste liquors, such as spent sulfite liquors from wood digestion by coking the liquors in the liquid phase under pressure under turbulent flow conditions to form coke and a clear effluent of low chemical oxygen demand. In the process, a heat exchange zone, a coking zone, a steam-and flue gas-producing zone, an absorbing zone, a wood digesting zone and a kilning zone are provided and interconnected by suitable conduits. Pressurized spent liquor is sent to the heat exchange zone where it absorbs heat from the coking zone effluent before coke separation, thereby absorbing also heat content contained in the coke. The coke is discharged to the kilning zone where it is dried by hot flue gases produced by burning previously dried coke in the steam producing zone. Sulfur dioxide containing warm, flue gas from the kilning zone is contacted in an absorbing zone with cool coker effluent to produce warm ammonium bisulfite solution which is passed to a wood digestion zone as well as cool flue gas substantially free of all air pollutants. Sulfur-containing gases produced by coking and wood digestion are burned in the steamproducing zone to manufacture sulfur dioxide for recycling. Use of a closed system reduces to a minimum odors in the digestion section of a pulp plant since all the odorous sulfur compounds are burned and the sulfur dioxide is recovered.

Inventors

• 👤 H Hess
• 👤 E Cole

Bibliographic Details