Apparatus and method for continuous pickling and regeneration of contact acid

Claim 1

A CONTINUOUS CYCLIC PROCESS FOR THE PICKLING OF IRON AND STEEL AND FOR REGENERATING THE USE PICKLE LIQUOR WHICH COMPRISES CONDUCTING THE PICKING OPERATION WITH A PICKLE LIQUOR HAVING AN ACID CONCENTRATION MAINTAINED WITHIN THE RANGE OF FROM ABOUT 14% TO ABOUT 22% BY VOLUME OF SULFURIC ACID AND MAINTAINING THE LIQUOR AT A TEMPERATURE OF FROM ABOUT 180* F. TO ABOUT 220* F. WHEREBY TO PERMIT RAPID AND UNIFORM PICKLING AT A RELATIVELY HIGH FERROUS SULFATE CONCENTRATION; CONTINUOUSLY WITHDRAWING USED PICKLE LIQUOR FROM THE PICKLING STEP FOR REGENERATION AND CONTINUOUSLY CONCENTRATING THE USE LIQUOR BY EVAPORATION; CONTINUOUSLY ADDING FRESH SULFURIC ACID TO THE PICKLE LIQUOR BEING REGENERATED WHILE AT THE SAME TIME MAINTAINING THE CONCENTRATED LIQUOR AT A TEMPERATURE OF FROM ABOUT 180* F. TO ABOUT 220* F. WHEREBY TO EFFECT RAPID CRYSTALLIZATION AND PRECIPITATION SULFATE SOLELY IN THE MONOHYDRATE FORM AS A RESULT OF THE COMBINED EFFECTS OF SAID TEMPERATURE AND INCREASED ACIDITY IN LOWERING THE SOLUBILITY OF FERROUS SULFATE MONHYDRATE; CONTINUOUSLY SEPARATING CRYSTALLIZED AND PRECIPITATED FERROUS SULFATE MONOHYDRATE AND THUS OBTAINING A RESULTANT CONCENTRATED LIQUOR HAVING A SULFURIC ACID CONCENTRATION ABOVE SAID RANGE; CONTINUOUSLY DILUTING SAID RESULTANT CONCENTRATED LIQUOR WITH SUFFICIENT WATER TO OBTAINED A REGENERATED PICKLE LIQUOR HAVING AN ACID CONCENTRATION WITHIN SAID RANGE; MAINTAINING THE PICKLE LIQUOR AT ALL TIMES THROUGHOUT THE AFOREMENTIONED REGENERATION STEPS AT A TEMPERATURE OF FROM ABOUT 180* F. TO ABOUR 220* F. WHEREBY TO PROVIDE A REGENERATED PICKLE LIQUOR ADAPTED FOR CONTINALL TIMES THROUGHOUT THE AFOREMENTIONED REREHEATING; AND CONTINUOUSLY RECIRCULATING THE REGENERATED PICKLE LIQUOR DIRECTLY TO THE PICKLING STEP WHEREBY TO PROVIDE A CONTINUOSLY RECICULATING THE AND REGENERATION SYSTEM CHARACTERIZED BY HIGH HEAT ECONOMY AND LOW HEAT INPUT REQUIREMENTS AS A RESULT OF THE MAINTENANCE OF SUBSTANTIALLY THE SAME OPERATING TEMPERATURE DUTING BOTH PICKLING AND REGENERATION.