Hydrocarbon cracking furnace and its operation

Claim 1

A FURNACE COMPRISING, IN COMBINATION, A COMBUSTION CHAMBER HAVING ENCLOSING WALLS, A FUEL BURNER OPERATIVELY POSITIONED IN ONE OF SAID WALLS, AN EXIT FOR COMBUSTION GASES FROM SAID COMBUSTION CHAMBER, A PLURALITY OF RADIANT HEATING TUBES DISPOSED OPERATIVELY IN SAID COMBUSTION CHAMBER, AN INLET COMMUNICATING WITH ONE END OF A FIRST HEATING TUBE OF SAID PLURALITY OF TUBES, A FIRST MANIFOLD COMMUNICATING THE OTHER END OF SAID FIRST HEATING TUBE WITH ADJACENT ENDS OF A PAIR OF SECOND HEATING TUBES OF SAID PLURALITY OF TUBES, SAID SECOND TUBES HAVING SMALLER INSIDE DIAMETERS THAN THE INSIDE DIAMETER OF SAID FIRST HEATING TUBE, A SECOND MANIFOLD COMMUNICATING THE OTHER ENDS OF SAID HEATING TUBES WITH ADJACENT ENDS OF THIRD HEATING TUBES OF SAID PLURALITY OF HEATING TUBES, SAID THIRD HEATING TUBES HAVING SMALLER INSIDE DIAMETERS THAN THE INSIDE DIAMETERS OF SAID SECOND HEATING TUBES, A THIRD MANIFOLD COMMUNICATING THE OTHER ENDS OF SAID THIRD HEATING TUBES WITH ADJACENT ENDS OF FOURTH HEATING TUBES, SAID FOURTH HEATING TUBES HAVING SMALLER INSIDE DIAMETERS THAN THE INSIDE DIAMETERS OF SAID THIRD HEATING TUBES, A FURNACE OUTLET, A FOURTH MANIFOLD COMMUNICATING THE OTHER ENDS OF SAID FOURTH HEATING TUBES WITH SAID OUTLET, SAID THIRD HEATING TUBES COMPRISING A PAIR AND AT LEAST ONE ADDITIONAL HEATING TUBE, AND SAID FOURTH HEATING TUBES COMPRISING AT LEAST ONE MORE HEATING TUBE THAN THE NUMBER OF THIRD HEATING TUBES.

Claim 3

A METHOD FOR CONVERTING IN A TUBE HEATER A VAPOROUS HYDROCARBON CONVERSION STOCK AT A MAXIMUM CONVERSION TEMPERATURE CONSISTENT WITH LONG OPERATING LIFE OF THE HEATER TUBES, COMPRISING PASSING SAID VAPOROUS HYDROCARBON STOCK THROUGH A FIRST HEATING TUBE, PASSING HYDROCARBON FROM SAID FIRST HEATING TUBE THROUGH A PLURALITY OF SECOND HEATING TUBES IN PARALLEL, THE LINEAR VELOCITY OF THE HYDROCARBON STOCK IN SAID SECOND TUBES BEING APPROXIMATELY THE SAME AS THE LINEAR VELOCITY THROUGH SAID FIRST HEATING TUBE, MAINTAINING THE SKIN TEMPERATURE OF SAID HEATER TUBES AT APPROXIMATELY THE MAXIMUM ALLOWABLE SKIN TEMPERATURE THEREOF AND WITHDRAWING CONVERTED HYDROCARBON PRODUCT FROM SAID SECOND HEATING TUBES.

Claim 4

A METHOD FOR CONVERTING IN A TUBE HEATER A VAPOROUS HYDROCARBON CONVERSION STOCK AT A MAXIMUM CONVERSION TEMPERATURE CONSISTENT WITH LONG OPERATING LIFE OF THE HEATER TUBES, COMPRISING PASSING SAID VAPOROUS HYDROCARBON STOCK THROUGH A FIRST HEATING TUBE, PASSING HYDROCARBON FROM SAID FIRST HEATING TUBE THROUGH A PLURALITY OF SECOND HEATING TUBES IN PARALLEL, THE LINEAR VELOCITY OF THE HYDROCARBON STOCK IN SAID SECOND TUBES BEING APPROXIMATELY THE SAME AS THE LINEAR VELOCITY THROUGH SAID FIRST HEATING TUBE, MAINTAINING THE SKIN TEMPERATURE OF SAID HEATER TUBES AT APPROXIMATELY THE MAXIMUM ALLOWABLE SKIN TEMPERATURE THEREOF AND WITHDRAWING CONVERTED HYDROCARBON PRODUCT FROM SAID SECOND HEATING TUBES.