Transfer line burner using gas of low oxygen content

Claim 2

IN AN EDOTHERMIC PROCESS CARRIED OUT IN A FLUIDIZED BED WHEREIN A STREAM OF CARBONACEOUS SOLIDS IS CONTINUOUSLY WITHDRAWN FROM THE FLUIDIZED BED AND INTRODUCED INTO THE LOWER END OF A TRANSFER LINE BURNER FOR THE GENERATION OF HEAT AND WHEREIN UNBURNED SOLIDS ARE WITHDRAWN FROM THE SAID TRANSFER LINE BURNER NEAR THE UPPER END THEREOF AND RETURNED TO THE SAID FLUIDIZED BED, THE IMPROVEMENT WHICH COMPRISES INTRODUCING A GAS OF LOW OXYGEN CONTENT CONTAINING UP TO AOUT 10 VOLUME PERCENT OF OXYGEN INTO SAID TRANSFER LINE BURNER CONTAINING SAID CARBONACEOUS SOLIDS NEAR THE LOWER END THEREOF IN A QUANTITY SUFFICIENT TO PRODUCE DILUTE PHASE FLOW OF SAID CARBONACEOUS SOLIDS UPWARDLY WITHIN SAID TRANSFER LINE BURNER AND INTRODUCING A GAS HAVING A HIGHER OXYGEN CONTENT THAN SAID GAS OF LOW OXYGEN CONTENT INTO AN UPPER PORTION OF SAID TRANSFER LINE BURNER IN AN AMOUNT SUFFICIENT TO RAISE THE TEMPERATURE OF SAID UNBURNED SOLIDS TO A LEVEL AOVE THE TEMPERATURE IN SAID FLUIDIZED BED.

Claim 3

A process as defined by claim 1 wherein said gas of low oxygen content is a flue gas.

Claim 4

A process as defined by claim 1 wherein said gas of higher oxygen content is air.

Claim 5

A process as defined by claim 1 wherein said gas of higher oxygen content is introduced into said transfer line burner at a plurality of points spaced about the periphery of said transfer line burner.

Claim 6

A process as defined by claim 1 wherein said gas of higher oxygen content is introduced into said transfer line burner at at least two points sufficiently far apart to permit the consumption of substantially all of the oxygen introduced at one of said points before the oxygen introduced at the other of said points contacts said carbonaceous solids.

Claim 7

A process as defined by claim 1 wherein said gas of low oxygen content is a mixture of flue gas and air containing less than about 6 percent oxygen by volume.

Claim 8

A process as defined by claim 1 wherein at least part of said gas of higher oxygen content is introduced into said transfer line burner at a point near the upper end thereof.

Claim 9

A process as defined by claim 1 wherein said gas of higher oxygen content is introduced into said transfer line burner in a quantity sufficient to raise the temperature of said solids about 50.degree. to about 300.degree. F. above the temperature of said fluidized bed.

Claim 10

A process as defined by claim 1 wherein said carbonaceous solids comprise coal char particles.

Claim 11

In a coal gasification process wherein coal char particles are continuously withdrawn from a fluidized bed gasifier, passed to a transfer line burner for the combustion of carbon and the generation of heat, and the heated particles are thereafter returned to said gasifier, the improvement which comprises introducing a gas of low oxygen content containing up to about 10 percent oxygen by volume and comprising flue gas into said transfer line burner containing said char particles near the lower end thereof in an amount sufficient to effect a transition in the flow of said particles from dense phase flow to dilute phase flow, introducing air into an upper portion of said burner in an amount sufficient to heat said char particles to a temperature about 50.degree. to about 300.degree. F. above the temperature of said fluidized bed, withdrawing a gas stream containing entrained particles from the upper end of said burner, separating entrained particles from said gas stream, and returning the separated particles to said gasifier.

Claim 12

In a coal gasification process wherein coal char particles are continuously withdrawn from a fluidized bed gasifier, passed to a transfer line burner for the combustion of carbon and the generation of heat, and the heated particles are thereafter returned to said gasifier, the improvement which comprises introducing a gas of low oxygen content containing up to about 10 percent oxygen by volume and comprising flue gas into said transfer line burner containing said char particles near the lower end thereof in an amount sufficient to effect a transition in the flow of said particles from dense phase flow to dilute phase flow, introducing air into an upper portion of said burner in an amount sufficient to heat said char particles to a temperature about 50.degree. to about 300.degree. F. above the temperature of said fluidized bed, withdrawing a gas stream containing entrained particles from the upper end of said burner, separating entrained particles from said gas stream, and returning the separated particles to said gasifier.

Claim 13

A process as defined by claim 10 wherein said gas of low oxygen content is a flue gas containing less than 1 percent oxygen by volume.

Claim 14

A process as defined by claim 10 wherein said gas of low oxygen content is introduced into said burner in an amount between about 0.1 and about 5 cubic feet per pound of char solids, measured at the burner temperature and pressure conditions.

Claim 15

A process as defined by claim 10 wherein the superficial gas velocity in said burner above the point at which said gas of low oxygen content is introduced is maintained between about 15 and about 100 feet per second.

Claim 16

A process as defined by claim 10 wherein said air is introduced into said burner at at least two vertically-spaced points sufficiently far apart to permit the consumption of substantially all of the oxygen introduced at the lowermost of said points before oxygen introduced at a higher point contacts said char particles.

Claim 17

A process as defined by claim 10 wherein said gas of low oxygen content is a mixture of flue gas and air containing less than about 6% oxygen by volume.