Method and apparatus for improved in situ combustion of pyrolysis gases in a kiln

Claim 2

In a process for pyrolysis of a carbonaceous material in a direct-fired rotary kiln wherein at least a portion of the thermal energy required for pyrolysis is obtained by the in situ combustion of the pyrolysis gases generated within the kiln with controlled quantities of an oxygen-containing gas admitted at the burner end of the kiln, said carbonaceous material undergoing pyrolysis being fed into the kiln at one end of the kiln and flowing toward the burner end of the kiln counter-current to the flow of the gaseous matter in the kiln, the improvement which comprises: (a) controlling the velocity of any burner combustion gases and the velocity of said oxygen-containing gas within the burner end of the kiln, and (b) distributing said oxygen-containing gas over a sufficiently large proportion of the internal radial cross-sectional area of said burner end of said kiln, so as to obtain a Craya-Curtet number of at least 0.2.

Claim 3

A process as in claim 1 wherein the Craya-Curtet number is at least 0.4.

Claim 4

A process as in claim 1 wherein the oxygen-containing gas is air.

Claim 5

A process as in claim 3 wherein at least a portion of said air is admitted to said burner end of the kiln through an annular space defined between the end of the kiln shell and a burner hood, said annular space extending circumferentially around at least 120° of the kiln proximate the upper portion therof.

Claim 6

A process as in claim 4 wherein the Craya-Curtet number is at least 0.4.

Claim 7

In a rotary kiln for the pyrolysis of carbonaceous materials comprising a refractory lined rotary kiln, a feed hood proximate one end thereof, a burner hood proximate the opposite end thereof, at least one burner disposed in said burner hood, a gas discharge conduit proximate said feed hood, and means for controllably admitting an oxygen-containing gas proximate said burner hood, whereby carbonaceous material charged to said kiln at said feed hood is caused to undergo pyrolysis and the resulting solid residue is discharged proximate said burner hood, at least a portion of the thermal energy required for pyrolysis being obtained by the in situ combustion of the pyrolysis gases within the kiln with controlled quantities of said oxygen-containing gas admitted to the kiln proximate the burner hood, the pyrolysis gases and the combustion products thereof flowing counter-currently to said heat decomposable organic material, the improvement which comprises: (a) means for controlling the velocity of any gases from the burner nozzle(s) and the velocity of said oxygen-containing gas within the kiln, and (b) said means for controllably admitting said oxygen-containing gas being such that said oxygen-containing gas is distributed over a sufficiently large proportion of the internal radial cross-sectional end of said burner end of said kiln, so as to provide a Craya-Curtet number of at least 0.2.

Claim 8

In a rotary kiln for the pyrolysis of carbonaceous materials comprising a refractory lined rotary kiln, a feed hood proximate one end thereof, a burner hood proximate the opposite end thereof, at least one burner disposed in said burner hood, a gas discharge conduit proximate said feed hood, and means for controllably admitting an oxygen-containing gas proximate said burner hood, whereby carbonaceous material charged to said kiln at said feed hood is caused to undergo pyrolysis and the resulting solid residue is discharged proximate said burner hood, at least a portion of the thermal energy required for pyrolysis being obtained by the in situ combustion of the pyrolysis gases within the kiln with controlled quantities of said oxygen-containing gas admitted to the kiln proximate the burner hood, the pyrolysis gases and the combustion products thereof flowing counter-currently to said heat decomposable organic material, the improvement which comprises: (a) means for controlling the velocity of any gases from the burner nozzle(s) and the velocity of said oxygen-containing gas within the kiln, and (b) said means for controllably admitting said oxygen-containing gas being such that said oxygen-containing gas is distributed over a sufficiently large proportion of the internal radial cross-sectional end of said burner end of said kiln, so as to provide a Craya-Curtet number of at least 0.2.

Claim 9

A rotary kiln as in claim 6 wherein said means for controllably admitting said oxygen-containing gas is such as to provide a Craya-Curtet number of at least 0.4.

Claim 10

A rotary kiln as in claim 6 wherein said means for controllably admitting an oxygen-containing gas comprises a plenum chamber circumferentially disposed around the outer shell of said kiln affixed to said burner hood so as to provide communication between said plenum chamber and the annular space defined between the end of the kiln shell and said burner hood circumferentially around at least 120° of the kiln proximate the upper portion thereof, said plenum chamber being further provided with means for admitting air into said plenum chamber.

Claim 11

A rotary kiln as in claim 8 wherein means are provided for adjusting the effective circumferential length and location of the air charging zone within the plenum chamber.

Claim 12

A rotary kiln as in claim 8 wherein said plenum chamber is partitioned, said partition being disposed within said plenum chamber and extending circumferentially with respect to the kiln so as to divide the plenum chamber into two concentric zones, said partition being provided with at least one opening for the flow of air from the first zone defined by said partition into the second zone defined by said partition.

Claim 13

A rotary kiln as in claim 10 wherein means are provided for adjusting the effective circumferential length and location of the air charging zone within the plenum chamber.