Process for the recovery of ammonium sulfate

Claim 1

IN A PROCESS FOR THE RECOVERY OF AMMONIA AND PYRIDINE FROM COKE-OVEN GAS IN LOW DIFFERENTIAL SATURATORS IN WHICH THE DIFFERENTIAL PRESSURE ACROSS THE GAS-LIQUID CONTACT MEANS OF THE SATURATOR IS LESS THAN 18 INCHES WATER COLUMN THE STEPS OF: CONTINUOUSLY BRINGING COKE-OVEN GAS IN CONTACT WITH SATURATOR SOLUTION IN SAID GAS-LIQUID CONTACT MEANS AT A RATE SUCH THAT AT LEAST 75 PER CENT OF THE AMMONIA IS ABSORBED AND INCORPORATING FRESH SULFURIC ACID IN THE SATURATOR SOLUTION TO MAINTAIN THE ACIDITY OF SAID SATURATOR SOLUTION; WITHDRAWING SATURATOR SOLUTION FROM SAID GAS-LIQUID CONTACT MEANS AND TREATING IT TO RECOVER AMMONIUM SULFATE AND PYRIDINE, SAID PYRIDINE RECOVERY BEING SUFFICIENT TO KEEP THE PYRIDINE CONTENT OF THE SATURATOR SOLUTION BELOW 5 PER CENT PYRIDINE; PREPARING A MAKE-UP LIQUOR BY ADDING AT LEAST A PART OF SAID FRESH SULFURIC ACID TO AN AMMONIUM SULFATE SOLUTION WHICH IS SEPARATE FROM SAID SATURATOR SOLUTION BUT WHICH IS OBTAINED THEREFROM IN THE OPERATION OF THE PROCESS, SAID MAKE-UP LIQUOR BEING UNSATURATED WITH RESPECT TO AMMONIUM SULFATE AND THE AMOUNT OF FRESH SULFURIC ACID ADDED THERETO BEING SUFFICIENT TO PROVIDE AN ACIDITY GREATER THAN THE ACIDITY OF SAID SATURATOR SOLUTION BUT LESS THAN 40 PER CENT SULFURIC ACID; CONTINUOUSLY WITHDRAWING COKE-OVEN GAS FROM SAID GAS-LIQUID CONTACT MEANS AFTER CONTACT WITH SAID SATURATOR SOLUTION THEREIN, BRINGING THE WITHDRAWN GAS INTO CONTACT WITH SAID MAKE-UP LIQUOR IN A SECOND GAS-LIQUID CONTACT MEANS, AND COLLECTING SAID MAKE-UP LIQUOR AFTER CONTACT WITH SAID GAS; WITHDRAWING MIST-LADEN COKE-OVEN GAS FROM SAID SECOND GAS-LIQUID CONTACT MEANS AFTER CONTACT WITH THE MAKE-UP LIQUOR THEREIN AND PASSING SAID MIST-LADEN GAS THROUGH A MIST SEPARATOR TO CONDENSE SAID MIST, THE WITHDRAWAL OF MIST-LADEN GAS FROM SAID SECOND GAS-LIQUID CONTACT MEANS AND THE CONDENSED MIST TO RECOVER PYRIDINE THERESEPARATOR ACTING TO PROLONG THE GAS-LIQUID CONTACT TIME AND TO PROMOTE EFFECTIVE LOW DIFFERENTIAL SCRUBBING OF THE RESIDUAL PYRIDINE FROM THE GAS; AND TREATING THE COLLECTED MAKE-UP LIQUOR AND THE CONDENSED MIST TO RECOVER PYRIDINE THEREFROM.