Abstract A process for recovering useful chemicals from spent alkaline cooking liquor of high sulfide content produced in the course of wood pulp manufacture. The spent cooking liquor is concentrated and the concentrate burned in a recovery furnace to produce a smelt comprising mainly Na2CO3 and Na2S. Part or all of the Na2CO3 is separated from the smelt and reacted with SO2 from the recovery furnace flue gases and, if desired, SO2 from another source to produce Na2SO3. The Na2SO3 is burned in the recovery furnace with the concentrated cooking liquor where said Na2SO3 is converted to Na2S. The resultant smelt has a high sulfide content and, when it is dissolved in water, an alkaline cooking liquor of high-sulfide content is regenerated.
In a process for regenerating cooking chemicals from spent alkaline cooking liquor containing Na2S and Na2CO3 in which said spent alkalinE cooking liquor is concentrated and the concentrated spent cooking liquor is burned in a recovery furnace to produce a smelt comprising Na2S and Na2CO3 and a flue gas containing SO2, the improvement comprising: a. dissolving the smelt in water and contacting SO2 from the flue gas therewith to convert the Na2CO3 contained therein to Na2SO3 to form a solution containing Na2SO3 and Na2S; b. recycling the resultant solution from (a) to fresh concentrated spent cooking liquor prior to the burning thereof in said recovery furnace; and c. burning the resultant mixed solution in said recovery furnace whereby Na2SO3 contained therein is converted to Na2S to be used in cooking liquor.
Claim 2
Dependent Claim
31 words
The process of claim 1 wherein the Na2SO3 solution is used in a sulfite cooking process prior to being added to concentrated spent cooking liquor and burned in the recovery furnace.
Claim 3
Dependent Claim
30 words
The process of claim 1 wherein the spent alkaline cooking liquor contains in addition to Na2S and Na2CO3 at least one member of the group consisting of NaOH and NaHS.