Method for controlling the level of a gravitating compact bed of solids

Claim 1

A PROCESS FOR COUNTERCURRENY CONTACTING OF A HOT OIL-BEARING GRANNULAR ADSORBENT WITH A SOLVENT CAPABLE OF DISSOLVING SAID OIL, WHICH COMPRISES: MAINTAINING A DOWNWARDLY GRAVITATING, SUBSTANTIALKLY COMPACT BED OF THE ADSORBENT WITHIN THE LOWER SECTION OF A CONFINED CONTACTING ZONE; CONTINUOUSLY REMOVING ADSORBENT FROM THE LOWER SECTION OF SAID BED; SUPPLYING LIQUID SOLVENT TO THE LOWER SECTION OF SAID BED AND PASSING THE SOLVENT UPWARDLY THERETHROUGH TO DISSOLVE OIL FROM THE ADSORBENT AT A RATE SUCH THAT THE PRESSURE GRADIENT DUE TO LIQUID FLOW THROUGH THE BED IS NOT GREATER THAN 0.75 (1-F-R)(S-L) POUNDS PER SQUARE FOOD PER FOOT OF BED HEIGHT, WHERE F=VOID FRACTION OF THE ADSORBENT ON A BULK BASIS, R=PORE FRACTION OF THE ADSORBENT ON A BULK BASIS, S=TRUE DENSITY OF THE ADSORBENT IN POUNDS PER CUBIC FOOT; AND L=THE DENSITY OF THE SOLVENT IN POUNDS PER CUBIC FOOT; MAINTAINING A BODY OF LIQUID SOLVENT WITH DISSOLVED OIL ABOVE SAID BED AND PASSING SOLVENT FROM THE UPPER END OF SAID BED INTO SAID BODY; REMOVING SOLVENT WITH DISSOLVE OIL FROM THE UPPER END OF SAID LIQUID BODY; PASSING A STREAM OF ADSORBENT WITH ADHERING OIL THROUGH A CONFINED PASSAGE INTO SAID CONTACTING ZONE AND DISCHARGING SAID STREAM FROM SAID PASSAGE AT A LEVEL ABOVE SAID BED AND ALLOWING THE ADSORBENT TO FALL THROUGH SAID BODY ONTO THE UPPER SURFACE OF SAID BED THE TEMPERARTURE OF SUPPLY OF ADSORBENT BEING SUFFICIENTLY ABOVE THE TEMPERATURE OF THE LIQUID SOLVENT BODY THAT AS THE ADSORBENT REACHES THE UPPER SURFACE OF SAID BED IT IS AT LEAST 25* F. HIGHER IN TEMPERATURE THAN THE SOLVENT SUPPLIED TO SAID BED; MAINTAINING THE RELATIVE RATES OF LIQUID SOLVENT AND ADSORBENT SUPPLIED TO SAID BED SUCH THAT THE HEAT CONTENT OF THE SOLVENT SO SUPPLIED IS AT LEAST 10 PERCENT GREATER THAN ADSORBENT SO SUPPLIED; MAINTAINING THE UPPER SURFACE OF SAID BED WITHIN A NARROW RANGE OF LEVELS BY MEASURING THE TEMPERATURE OF THE LIQUID BODY AT A POINT ABOVE SAID NARROW RANGE AND THE TEMPERATURE OF SAID BED AT A POINT BELOW SAID NARROW RANGE AND, ALSO, MEASURING TEMPERATURES AT THE UPPER AND LOWER LIMITS OF SAID NARROW RANGE, AND CONTROLLING THE RATE OF REMOVAL OF ADSORBENT TO MAINTAIN THE TEMPERARURE MEASURED ABOVE SAID RANGE ABOUT THE SAME AS THE TEMPERATURE MEASURED AT THE UPPER LIMIT OF SAID RANGE, THE TEMPERATURE MEASURED BELOW SAID RANGE ABOUT THE SAME AS THE TEMPERATURE AT THE LOWER LIMIT OF SAID RANGE AND A TEMPERATURE DIFFERENTIAL OF GREATER THAN 5* F. BETWEEN THE TEMPERATURE MEASURED AT THE UPPER AND LOWER LIMITS OF SAID RANGE.