Method and apparatus for producing polyphosphoric acid

Claim 1

IN A PROCESS FOR PRODUCING POLYPHOSPHORIC ACID BY COMBUSTING ELEMENTARY PHOSPHORUS IN A REACTOR IN THE PRESENCE OF OXYGEN AND ABSORBING P2O5 COMBUSTION PRODUCT IN AN ABSORBENT THE IMPROVEMENT COMPRISING INITIALLY TRANSFERRING AND ABSORBING THE HEAT OF REACTION AND THE COMBUSTION PRODUCT IN TWO SEPARATE CIRCUITS A MAJOR AMOUNT OF THE HEAT OF REACTION AND PART OF THE P2O5 COMBUSTION PRODUCT BEING ABSORBED IN A FIRST CIRCUIT CONSISTING ESSENTIALLY OF A SEPARATELY RECYCLED COOLED COOLANT DISTRIBUTED OVER THE INSIDE WALLS OF SAID REACTOR, SAID COOLANT BEING MAINTAINED AT VOLUME AND A CONCENTRATION OF ABOUT 105-107% H3PO4 BY THE OUTSIDE ADDITION OF WATER OR PHOSPHORIC ACID, ESSENTIALLY SEPARATELY ABSORBING THE REST OF THE P2O5 COMBUSTION PRODUCT AND TRANSFERRING A MINOR AMOUNT OF HEAT OF REACTION IN A SECOND CIRCUIT COMPRISING A SEPARATELY RECYCLED COOLED LIQUID ABSORBENT CONSISTING ESSENTIALLY OF POLYPHOSPHORIC ACID HAVING A HIGHER CONCENTRATION OF H3PO4 THAN SAID COOLANT, WITHDRAWING RESULTING ENRICHED POLYPHOSPHORIC ACID ABSORBENT AS A FINAL PRODUCT, MAINTAINING VOLUME AND CONCENTRATION OF ABSORBENT BY ADDING WATER AND PHOSPHORIC ACID.