A SOLUBLE SOLUTION FLUE GAS DESULFURIZATION AND DENOX PROCESS

PILOT PLANT WORK IS BEING CARRIED OUT ON THE REDUCTION OF SODIUM SULFITE CONTAINING SOME SODIUM SULFATE INTO SODIUM SULFIDE, A KEY STEP IN THE SOLUBLE SOLUTION PROCESS FOR REMOVAL OF SULFUR OXIDES, NITROGEN OXIDES, AND PARTICULATES FROM THE FLUE GAS OF COAL-FIRED UTILITIES. IN THE FLUE GAS ABSORPTION STEP, A SOLUTION OF SODIUM CARBONATE IS USED TO REACT WITH SULFUR DIOXIDE TO FORM PRIMARILY SODIUM SULFITE. EVAPORATION OF THE SOLUTION PRODUCES A CRYSTALLINE SODIUM SULFITE AND SOME SODIUM SULFATE. LABORATORY TESTS HAVE DEMONSTRATED THAT SODIUM SULFATE COMBINED WITH A REDUCING AGENT SUCH AS COAL AND HEATED TO ABOUT 1300 DEGREES FAHRENHEIT IN A CRUCIBLE IN A MUFFLE FURNACE CAN BE REDUCED TO SODIUM SULFIDE IN THE SOLID STATE. THIS TECHNOLOGY AVOIDS HANDLING THE SODIUM SULFIDE AS A LIQUID AT 1900 DEGREES FAHRENHEIT. IN THIS STATE, THE SODIUM SULFIDE IS SEVERELY EROSIVE AND CORROSIVE TO REFRACTORIES. IN PHASE I, PILOT PLANT TESTS ARE PLANNED TO DEMONSTRATE THE FEASIBILITY OF REDUCING SODIUM SULFITE WITH COAL IN A ROTARY KILN. IT IS NECESSARY THAT REDUCTION BE CARRIED OUT WITHOUT GENERATING FINES OR DUST. THEREFORE, THE CRYSTALLINE SODIUM SULFITE IS FIRST COMBINED WITH COAL TO FORM PELLETS. LABORATORY TESTS HAVE SHOWN THAT THESE PELLETS ARE REDUCED WITHOUT ANY DISINTEGRATION. PILOT PLANT TESTS IN A ROTARY KILN ARE NOW BEING CARRIED OUT TO ESTABLISH THE INTEGRITY OF THE PELLETS IN A MOVING BED. DIFFERENT BINDERS ARE USED IN PRODUCING PELLETS. THE CONVERSION OF SODIUM SULFIDE TO ELEMENTAL SULFUR AND SODIUM CARBONATE FOR RECYCLING TO THE ABSORPTION OPERATION IS A WELL-ESTABLISHED PROCESS THAT IS USED IN THE PULP AND PAPER FIELD.