Fines recirculating fluid bed combustor method and apparatus

Claim 3

A method according to claim 1 wherein said fluid bed combustor is refractory lined, whereby said recycling path of fine particles can be maintained at said substantially constant temperature even though substantially no combustion takes place in either said freeboard or separator.

Claim 4

A method according to claim 1 wherein said fluid bed combustor is operated such that afterburning of fuel particles above said fluidizing bed amounts to no more than about 100° F.

Claim 5

A method according to claim 1 wherein said fluid be combustor is operated such that afterburning of fuel particles above said fluidizing bed amounts to no more than about 20° F.

Claim 6

A method according to claim 1 wherein said generally horizontal bed of inert particles, ash and partially burned solid fuel maintained on said distribution plate has an average particle size in the range of 100 microns to 800 microns with 20% to 40% less than 200 microns and wherein said continuous stream of fluidizing gas is directed upward within said combustion chamber and below said distribution plate at a superficial velocity in the range of 0.5 to 7 feet per second.

Claim 7

A method according to claim 1 including the step of feeding a sulphur oxide sorbent into said fluidizing bed along with the other particles therein and maintaining the fluidizing bed of inert particles, ash, partially burned fuel particles, partially spent sulphur sorbent and spent sulphur sorbent with an average particle size in the range of 100 to 800 microns.

Claim 8

A method according to claim 1 wherein said fluid bed combustor is operated such that the temperature within said fluidizing bed and the temperature along said recycle path is between about 1400° F. and 1500° F. whereby to encourage minimum nitrogen oxide formation during the combustion of said fuel and to encourage char production with the attendant suppression of nitrogen oxide by hot char in said fluidizing bed and along said recycle path.

Claim 9

A method according to claim 1 wherein said fluidizing bed is operated such that particulate fuel particles which is within the bed and which is sufficiently fine to be carried by said stream of fluidizing gas is located sufficiently deep within the bed to substantially completely combust before reaching the top of the bed where it can be carried off by said gas stream.

Claim 10

A method according to claim 1 wherein said recycle separator is a recycle cyclone.

Claim 11

A method according to claim 1 wherein said fluid bed combustor is operated such that substantially no cooling of particles within either said freeboard or said recycle separator takes place.

Claim 12

A method according to claim 10 wherein no heat transfer surfaces are provided within said combustion chamber between said fluidizing bed and said recycle separator.

Claim 13

A method according to claim 1 including the steps of feeding fine particulate fuel into said bed, said fine fuel being fed only into the bottom of said bed, and feeding large, non-fine particulate fuel onto the top of said bed only.

Claim 14

A method according to claim 12 wherein said fine particulate fuel is 1/4"- and wherein large particulate fuel is 1/4"+.

Claim 15

A method according to claim 1 wherein said fluid bed combustor is operated such that the temperature within the fluidizing bed and the temperature along said recycling path are substantially equal.

Claim 16

A method according to claim 6 wherein the temperature of said fluidizing bed and said recycling path is about 1400° F.

Claim 17

A method according to claim 14 wherein the temperature of said fluidizing bed and said recycling path is about 1600° F.

Claim 18

A method according to claim 1 wherein said fluid bed combustor is operated such that the temperature within said fluidizing bed is maintained between about 1450° F. and 1650° F. and afterburning of fuel particles above said bed amounts to no more than about 150° F., whereby to promote the efficient suppression of nitrogen oxide from fuel containing fuel bound nitrogen in the presence of ammonia, without the need for a catalyst.

Claim 19

A method according to claim 17 including the step of spraying ammonia into said recycle path of particle-laden gas immediately upstream of the inlet to the recycle separator, without a catalyst.

Claim 20

A method according to claim 17 wherein said fluid bed combustor is operated such that the temperature within said fluidizing bed is about 1450° F., whereby to promote the efficient suppression of nitrogen oxide from fuel having a high percentage of fixed carbon.

Claim 21

A fluid bed combustion apparatus for burning solid particulate fuel or liquid fuel and recovering useful energy therefrom, comprising: (a) a fluid bed combustor including means for maintaining a generally horizontal bed of inert particles, ash and some partially burned solid fuel particles on a distribution plate within an internal combustion chamber defined by said fluid bed combustor, said combustor also defining a freeboard immediately above the bed of particles; (b) means for directing a continuous stream of fluidizing gas upward within said combustion chamber from below said distribution plate so that the stream passes through the plate and said bed of particles for fluidizing the latter, the velocity of said stream of gas being such that the stream carries fine particles of a certain size and smaller upward with it into the freeboard from the fluidizing bed; (c) means including a particle recycle separator for capturing substantially all of said fine particles carried upward by said stream of fluidizing gas within said recycle separator which is positioned above said freeboard, and for returning most of the captured particles to the fluidizing bed while exhausting the gas from said separator, whereby the captured and returned fine particles define a recycling path of movement from the bed, through the freeboard and separator and back into the bed; (d) means for recovering heat energy from combustion taking place in said fluidizing bed but not from said recycling path of fine particles; and (e) said fluid bed combustor including its fluidizing bed and separator being configured such that substantially all combustion of said fuel particles takes place only within said bed and not in either the freeboard or the separator and such that said recycling path of fine particles is maintained at a substantially constant temperature.

Claim 22

A fluid bed combustion apparatus for burning solid particulate fuel or liquid fuel and recovering useful energy therefrom, comprising: (a) a fluid bed combustor including means for maintaining a generally horizontal bed of inert particles, ash and some partially burned solid fuel particles on a distribution plate within an internal combustion chamber defined by said fluid bed combustor, said combustor also defining a freeboard immediately above the bed of particles; (b) means for directing a continuous stream of fluidizing gas upward within said combustion chamber from below said distribution plate so that the stream passes through the plate and said bed of particles for fluidizing the latter, the velocity of said stream of gas being such that the stream carries fine particles of a certain size and smaller upward with it into the freeboard from the fluidizing bed; (c) means including a particle recycle separator for capturing substantially all of said fine particles carried upward by said stream of fluidizing gas within said recycle separator which is positioned above said freeboard, and for returning most of the captured particles to the fluidizing bed while exhausting the gas from said separator, whereby the captured and returned fine particles define a recycling path of movement from the bed, through the freeboard and separator and back into the bed; (d) means for recovering heat energy from combustion taking place in said fluidizing bed but not from said recycling path of fine particles; and (e) said fluid bed combustor including its fluidizing bed and separator being configured such that substantially all combustion of said fuel particles takes place only within said bed and not in either the freeboard or the separator and such that said recycling path of fine particles is maintained at a substantially constant temperature.

Claim 23

An apparatus according to claim 20 wherein said fluid bed combustor is such that the temperature within the fluidizing bed and the temperature along said recycling path are substantially equal.

Claim 24

An apparatus according to claim 20 wherein said fluid bed combustor is configured such that afterburning of fuel particles above said fluidizing bed amounts to no more than about 100° F.

Claim 25

An apparatus according to claim 20 wherein said fluid bed combustor is configured such that afterburning of fuel particles above said fluidizing bed amounts to no more than about 20° F.

Claim 26

An apparatus according to claim 20 including means for spraying ammonia into said recycle path of particle-laden gas immediately upstream of the inlet to the recycle separator without a catalyst.

Claim 27

An apparatus according to claim 20 wherein said generally horizontal bed of inert particles, ash and partially burned solid fuel maintained on said distribution plate has an average particle size in the range of 100 microns to 800 microns width 20% to 40% less than 200 microns and wherein said continuous stream of fluidizing gas is directed upward within said combustion chamber and below said distribution plate at a superficial velocity in the range of 0.5 to 7 feet per second.

Claim 28

An apparatus according to claim 20 including means for feeding a sulphur oxide sorbent into said fluidizing bed along with the other particles therein and maintaining the fluidizing bed of inert particles, ash, partially burned fuel particles, partially spent sulphur sorbent and spent sulphur sorbent with an average particle size in the range of 100 to 800 microns.

Claim 29

An apparatus according to claim 20 wherein said fluidizing bed is configured such that particulate fuel particles which are within the bed and which are sufficiently fine to be carried by said stream of fluidizing gas are located sufficiently deep within the bed to substantially completely combust before reaching the top of the bed where it can be carried off by said gas stream.

Claim 30

An apparatus according to claim 20 wherein said recycle separator is a recycle cyclone.

Claim 31

An apparatus according to claim 20 wherein said fluid bed combustor is configured such that substantially no cooling of particles within either said freeboard or said recycle separator takes place.

Claim 32

An apparatus according to claim 29 wherein no heat transfer surfaces are provided within said combustion chamber between said fluidizing bed and said recycle separator.

Claim 33

An apparatus according to claim 20 including means for said fine fuel being fed only into the bottom of said bed, and including means for feeding large, non-fine particulate fuel onto the top of said bed only.

Claim 34

An apparatus according to claim 31 wherein said fine particulate fuel is 1/4"- and wherein large particulate fuel is 1/4"+.

Claim 35

An apparatus according to claim 20 wherein said fluid bed combustor is refractory lined, whereby said recycling path of fine particles can be maintained at said substantially constant temperature even though substantially no combustion takes place in either said freeboard or separator.

Claim 36

An apparatus according to claim 33 wherein the temperature of said fluidizing bed and said recycling path is about 1400° F.

Claim 37

An apparatus according to claim 33 wherein the temperature of said fluidizing bed and said recycling path is about 1600° F.

Claim 38

A fluid bed combustion apparatus, comprising: (a) housing means defining an internal combustion chamber; (b) means including a distribution plate for maintaining a generally horizontal bed of inert particles, ash and partially burned solid fuel particles on said distribution plate and within said internal combustion chamber directly below a freeboard within the chamber; (c) means for directing a continuous stream of fluidizing gas upward within said combustion chamber from below said distribution plate so that the stream passes through the plate and said bed of particles for fluidizing the latter, the velocity of said stream of gas being such that the stream carries fine particles of a certain size and smaller upward with it into the freeboard from the fluidizing bed; (d) means including a particle recycle separator located within said combustion chamber above said freeboard for capturing substantially all of said fine particles carried upward by said stream of fluidizing gas and for returning most of the captured particles to said fluidizing bed while exhausting the gas from said separator, whereby the captured and returned particles define a recycling path of movement from the bed, through the freeboard and separator and back into the bed; (e) means for recovering heat energy only from within said fluidizing bed and not from said recycling path of fine particles; and (f) said fluidizing bed, separator and freeboard therebetween being configured such that substantially all combustion of said fuel particles takes place only within said bed and not within either the freeboard or the separator and such that said recycling path of fine particles is maintained at a substantially constant temperature.

Claim 39

A fluid bed combustion apparatus, comprising: (a) housing means defining an internal combustion chamber; (b) means including a distribution plate for maintaining a generally horizontal bed of inert particles, ash and partially burned solid fuel particles on said distribution plate and within said internal combustion chamber directly below a freeboard within the chamber; (c) means for directing a continuous stream of fluidizing gas upward within said combustion chamber from below said distribution plate so that the stream passes through the plate and said bed of particles for fluidizing the latter, the velocity of said stream of gas being such that the stream carries fine particles of a certain size and smaller upward with it into the freeboard from the fluidizing bed; (d) means including a particle recycle separator located within said combustion chamber above said freeboard for capturing substantially all of said fine particles carried upward by said stream of fluidizing gas and for returning most of the captured particles to said fluidizing bed while exhausting the gas from said separator, whereby the captured and returned particles define a recycling path of movement from the bed, through the freeboard and separator and back into the bed; (e) means for recovering heat energy only from within said fluidizing bed and not from said recycling path of fine particles; and (f) said fluidizing bed, separator and freeboard therebetween being configured such that substantially all combustion of said fuel particles takes place only within said bed and not within either the freeboard or the separator and such that said recycling path of fine particles is maintained at a substantially constant temperature.

Claim 40

An apparatus according to claim 36 including first means for feeding fine particulate fuel into the bottom of said bed and second means for feeding large particulate fuel onto the top of said bed.

Claim 41

An apparatus according to claim 36 wherein said fluidizing bed is operated such that particulate fuel which is within the bed and which is sufficiently fine to be carried by said stream of fluidizing gas is located sufficiently deep within the bed to substantially completely combust before reaching the top of the bed where it can be carried off by said gas stream.

Claim 42

An apparatus according to claim 36 wherein said recycle separator is a recycle cyclone.

Claim 43

An apparatus according to claim 36 wherein said first and second particulate fuel feed means are the only feed means forming part of said apparatus.

Claim 44

An apparatus according to claim 40 wherein said fine particulate fuel is 1/4"- and where said large particulate fuel is 1/4"+.