Recovering water from spent sulfite liquor

Abstract

Abstract SPENT SULFITE LIQUOR USED IN THE CALCIUM BASE SULFITE PULPING PROCESS IS DILUTED BY ABOUT SIX PARTS WATER TO ONE PART OF SPENT LIQUOR AS IT EXISTS IN THE PULP. TO RECOVER THE WATER FOR RE-USE, THE PH OF THE DILUTED LIQUOR IS FIRST ADJUSTED TO ABOUT 6.4 BY ADDITION OF 30% NAOH. THE LIQUOR IS THEN PUT IN AN ELECTROLYTIC CELL HAVING ELECTRODES OF MILD STEEL ABOUT 1/2 INCH APART AND IS SUBJECTED TO DIRECT CURRENT VOLTAGE OF ABOUT 27-36 VOLTS BETWEEN ELECTRODES WITH ENOUGH CURRENT TO BRING THE TEMPERATURE WITHIN A RANGE OF 140*F. TO 200*F. IN ABOUT TWO MINUTES. CURRENT IS CUT OFF AND THE LIQUID IS COOLED FOR TWO TO FIVE MINUTES TO ENABLE A DARK GREEN PRECIPITATE TO FORM. THEN, THE LIQUID IS FILTERED. THE RECOVERED LIQUID IS BROUGHT TO A PH OF 11 USING NAOH AND THEN IS SUBJECTED TO DIRECT CURRENT OF 30 VOLTS IN A SECOND ELECTROLYTIC CELL HAVING A MILD STEEL CATHODE AND A LEAD DIOXIDE ANODE 1/2 INCH APART, UNTIL THE TEMPERATURE IS AGAIN RAISED TO BETWEEN 140*F. AND 200*F. THE TREATED LIQUID IS ALLOWED TO COOL TO FORM ANOTHER DARK GREEN PRECIPITATE. THIS IS AGAIN FILTERED. THEN, THE COOLED LIQUID IS NEUTRALIZED, USING SULFURIC ACID, TO A PH OF 7. A WHITE PRECIPITATE FORMS AND IS FILTERED OUT. THE WATER REMAINING IS NOW RE-USABLE.

Inventors

• 👤 Bernard J Stralser

Bibliographic Details