Sodium sulfite recovery process

Claim 1

THE METHOD OF CONTINUOUSLY CONVERTING THE SODIUM SULFIDE AND SODIUM CARBONATE CONTENT OF GREEN LIQUOR, DERIVED FROM A SMELT OF THE WASTE LIQUOR FROM THE PULPING OF WOOD, TO SODIUM SULFITE FOR RE-USE IN THE PULPING PROCESS, WHICH METHOD COMPRISES, A CO2 AND H2S ABSORPTION STAGE (A), A CARBONATION STAGE (B), AND H2S CONVERSION STAGE (C), A NA2CO3, NAHSO3 MIXING STAGE (D), AND A SULFITATION SATAGE (E), PASSING A GAS CONTAINING NITROGEN, HYDROGEN SULFIDE AND CARBON DIOXIE COUNTERCURRENTLY THROUGH A DESCENDING FLOW OF THE GREEN LIQUOR AT A TEMPERATURE OF FROM 60*-90* C. IN THE SAID ABSORPTION STAGE (A), WHEREBY THE CARBON DIOXIDE AND HYDROGEN SULFIDE ARE SEPRATED ALMOST QUANTITATIVELY FROM THE SAID GAS BY REACTING WITH SOME OF THE SODIUM SLUFIDE AND SODIUM CARBONATE OF THE LIQUOR TO PRODUCE SODIUM HYDROSULFIDE AND SODIUM BICARBONATE, WITHDRAWING THE REMAINDER OF SAID GAS COMPRISNG ALMOST ENTIRELY NITROGEN FROM SAID STAGE (A) BY MAINTAINING THE SYSTEM UNDER A SLIGHT VACUUM, SUBJECTING THE RESIDUAL LIQUOR FROM THE SAID ABSORPTION STAGE (A) CONTAINING SODIUM HYDROSULFIDE, SODIUM SULFIDE, SODIUM CARBONATE, AND SODIUM BICARBONATE AND HAVING A RELATIVELY CONSTANT AND HIGHER H2S VAPOR PRESSURE THAN THE ORIGINAL GREEN LIQUOR IN SAID CARBONATION STAGE (B) TO THE COUNTERCURRENT ACTION OF A GAS COMPRISING PRINCIPALLY CARBON DIOXIDE, SOME NITROGEN AND WATE VAPOR, SAID GAS HAVING A FLOW RATE SUFFICIENT TO MAINTAIN A RATIO OF CARBON DIOXIDE TO SULFIDE ENTERING SAID STGE (B) OF AT LEAST 8 MOLS TO 1, WHEREBY TO CONVERT THE SODIUM SULFIDE AND SODIUM HYDROSULFIDE TO A NON-INFLAMMABLE GAS PRODUCT CONTAINING HYDROGEN SULFIDE UP TO 6% AND A LIQUOR PRODUCT CONTAINING SODIUM BICARBONATE AND SODIUM CARBONATE, DIVIDING THE GAS PRODUCT OF SAID CARBONATION STAGE INOT TWO PORTIONS, ONE OF WHICH IS RECYCLED TO THE SAID ADSORPTION STAGE (A) TO PROVIDE THE GAS REACTANT OF THAT STAGE, AND THE OTHER MAJOR PROVIDE THE GAS REACTANT OF THAT STAGE, STAGE (C) WHERE THE HYDROGEN SULFIDE IS MIXED WITH AIR AND CATAYLTICALLY OXIDIZED AT A TEMPERATURE OF FROM 200400*C. TO A MEMBER SELECTED FROM THE GROUP CONSISTING OF ELEMENTAL SULFUR AND SULFUR DIOXIDE, PASSING ANY ELEMENTAL SULFUR PRODUCED TO A SULFUR CONVERSION STAGE WHEREIN IT IS OXIDIZED TO SULFUR DIOXIDE, HEATING THE GAS ENTERING THE SAID CONVERSION STAGE (C) WITH THE HOT GASES LEAVING SAID STAGE (C) TO MAINTAIN AN EVEN TEMPERATURE DURING THE CONVERSION, CONTACTING AT LEAST A MAJOR PORTION OF THE EFFLUENT GAS FROM THE CONVERSION STAGE WITH THE LIQUOR PRODUCT OF THE CARBONATION STAGE (B), AND THE REMAINDER OF THE SAID EFFLUENT GAS, WITH THE LIQUOR OF SAID SULFITATION STAGE (E), REACTING SODIUM BISULFITE FROM THE SAID STAGE (E) WITH THE LIQUOR PRODUCT OF SAID STAGE (B) CONTAINING THE SODIUM CARBONATE AND SODIUM BICARBONATE IN SAID MIXING STAGE (D) TO PRODUCE A GAS PRODUCT CONTAINING ESSENTIALLY CARBON DIOXIDE AND A LIQUOR PRODUCT CONTAINING ESSENTIALLY SODIUM SULFITE, RETURNING THE LAST-MENTIONED GAS PRODUCT TO THE CARBONATION STAGE (B) TO PROVIDE THE CARBON DIOXIDE REACTANT OF THAT STAGE, REMOVING FROM THE SYSTEM A FIRST PORTION OF THE LASTMENTIONED LIQUOR PRODUCT CONTAINING ESSENTIALLY SODIUM SULFITE, SAID PORTION BEING EQUAL TO THE GREEN LIQUOR FLOW AS PRODUCED SODIUM SULFITE LIQUOR, AND PASSING A SECOND PORTION OF IT IN THE SAID SULFITATION STAGE (E) COUNTERCURRENTLY TO A FLOW OF SULFUR DIOXIDE GASES WHEREBY TO PRODUCE A GAS PRODUCT CONSISTING ESSENTIALLY OF NITROGEN AND A SODIUM BISULFITE LIQUOR PRODUCT, RETURNING THE LATTER TO SAID MIXING STAGE (D) TO PROVIDE THE SODIUM BISULFITE REACTANT OF THAT STAGE, AND RELIEVING THE SAID GAS PRODUCT FROM SAID STAGE (E).

Claim 2

THE METHOD OF CONTINUOUSLY CONVERTING THE SODIUM SULFIDE AND SODIUM CARBONATE CONTENT OF GREEN LIQUOR, DERIVED FROM A SMELT OF THE WASTE LIQUOR FROM THE PULPING OF WOOD, TO SODIUM SULFITE FOR RE-USE IN THE PULPING PROCESS, WHICH METHOD COMPRISES, A CO2 AND H2S ABSORPTION STAGE (A), A CARBONATION STAGE (B), AND H2S CONVERSION STAGE (C), A NA2CO3, NAHSO3 MIXING STAGE (D), AND A SULFITATION SATAGE (E), PASSING A GAS CONTAINING NITROGEN, HYDROGEN SULFIDE AND CARBON DIOXIE COUNTERCURRENTLY THROUGH A DESCENDING FLOW OF THE GREEN LIQUOR AT A TEMPERATURE OF FROM 60*-90* C. IN THE SAID ABSORPTION STAGE (A), WHEREBY THE CARBON DIOXIDE AND HYDROGEN SULFIDE ARE SEPRATED ALMOST QUANTITATIVELY FROM THE SAID GAS BY REACTING WITH SOME OF THE SODIUM SLUFIDE AND SODIUM CARBONATE OF THE LIQUOR TO PRODUCE SODIUM HYDROSULFIDE AND SODIUM BICARBONATE, WITHDRAWING THE REMAINDER OF SAID GAS COMPRISNG ALMOST ENTIRELY NITROGEN FROM SAID STAGE (A) BY MAINTAINING THE SYSTEM UNDER A SLIGHT VACUUM, SUBJECTING THE RESIDUAL LIQUOR FROM THE SAID ABSORPTION STAGE (A) CONTAINING SODIUM HYDROSULFIDE, SODIUM SULFIDE, SODIUM CARBONATE, AND SODIUM BICARBONATE AND HAVING A RELATIVELY CONSTANT AND HIGHER H2S VAPOR PRESSURE THAN THE ORIGINAL GREEN LIQUOR IN SAID CARBONATION STAGE (B) TO THE COUNTERCURRENT ACTION OF A GAS COMPRISING PRINCIPALLY CARBON DIOXIDE, SOME NITROGEN AND WATE VAPOR, SAID GAS HAVING A FLOW RATE SUFFICIENT TO MAINTAIN A RATIO OF CARBON DIOXIDE TO SULFIDE ENTERING SAID STGE (B) OF AT LEAST 8 MOLS TO 1, WHEREBY TO CONVERT THE SODIUM SULFIDE AND SODIUM HYDROSULFIDE TO A NON-INFLAMMABLE GAS PRODUCT CONTAINING HYDROGEN SULFIDE UP TO 6% AND A LIQUOR PRODUCT CONTAINING SODIUM BICARBONATE AND SODIUM CARBONATE, DIVIDING THE GAS PRODUCT OF SAID CARBONATION STAGE INOT TWO PORTIONS, ONE OF WHICH IS RECYCLED TO THE SAID ADSORPTION STAGE (A) TO PROVIDE THE GAS REACTANT OF THAT STAGE, AND THE OTHER MAJOR PROVIDE THE GAS REACTANT OF THAT STAGE, STAGE (C) WHERE THE HYDROGEN SULFIDE IS MIXED WITH AIR AND CATAYLTICALLY OXIDIZED AT A TEMPERATURE OF FROM 200400*C. TO A MEMBER SELECTED FROM THE GROUP CONSISTING OF ELEMENTAL SULFUR AND SULFUR DIOXIDE, PASSING ANY ELEMENTAL SULFUR PRODUCED TO A SULFUR CONVERSION STAGE WHEREIN IT IS OXIDIZED TO SULFUR DIOXIDE, HEATING THE GAS ENTERING THE SAID CONVERSION STAGE (C) WITH THE HOT GASES LEAVING SAID STAGE (C) TO MAINTAIN AN EVEN TEMPERATURE DURING THE CONVERSION, CONTACTING AT LEAST A MAJOR PORTION OF THE EFFLUENT GAS FROM THE CONVERSION STAGE WITH THE LIQUOR PRODUCT OF THE CARBONATION STAGE (B), AND THE REMAINDER OF THE SAID EFFLUENT GAS, WITH THE LIQUOR OF SAID SULFITATION STAGE (E), REACTING SODIUM BISULFITE FROM THE SAID STAGE (E) WITH THE LIQUOR PRODUCT OF SAID STAGE (B) CONTAINING THE SODIUM CARBONATE AND SODIUM BICARBONATE IN SAID MIXING STAGE (D) TO PRODUCE A GAS PRODUCT CONTAINING ESSENTIALLY CARBON DIOXIDE AND A LIQUOR PRODUCT CONTAINING ESSENTIALLY SODIUM SULFITE, RETURNING THE LAST-MENTIONED GAS PRODUCT TO THE CARBONATION STAGE (B) TO PROVIDE THE CARBON DIOXIDE REACTANT OF THAT STAGE, REMOVING FROM THE SYSTEM A FIRST PORTION OF THE LASTMENTIONED LIQUOR PRODUCT CONTAINING ESSENTIALLY SODIUM SULFITE, SAID PORTION BEING EQUAL TO THE GREEN LIQUOR FLOW AS PRODUCED SODIUM SULFITE LIQUOR, AND PASSING A SECOND PORTION OF IT IN THE SAID SULFITATION STAGE (E) COUNTERCURRENTLY TO A FLOW OF SULFUR DIOXIDE GASES WHEREBY TO PRODUCE A GAS PRODUCT CONSISTING ESSENTIALLY OF NITROGEN AND A SODIUM BISULFITE LIQUOR PRODUCT, RETURNING THE LATTER TO SAID MIXING STAGE (D) TO PROVIDE THE SODIUM BISULFITE REACTANT OF THAT STAGE, AND RELIEVING THE SAID GAS PRODUCT FROM SAID STAGE (E).