# US 2015/0285494 A1 · Powered fuel conversion systems

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- Number: US 2015/0285494 A1
- Document ID: US20150285494A1
- Status: Published application
- Kind: A1
- Application number: 14/688,263
- Filed: 2015-04-16
- Published: 2015-10-08
- Earliest claimed: 2006-11-17
- Inventors: James K. McKnight; Edward Bacorn; Ken W. White
- Web page: https://patentgrep.com/patent/US20150285494A1

## CPC

- F23N 5/00: Systems for controlling combustion (regulating fuel supply F23N1/00, regulating air supply or draught F23N3/00)
- F23C 1/12: gaseous and pulverulent fuel
- F23C 6/02: in parallel arrangement
- F23C 6/045: {with staged combustion in a single enclosure}
- F23D 1/005: {burning a mixture of pulverulent fuel delivered as a slurry, i.e. comprising a carrying liquid}
- F23D 1/02: Vortex burners, e.g. for cyclone-type combustion apparatus
- F23G 5/033: comminuting or crushing
- F23G 5/444: {for solid waste (F23G5/448 takes precedence)}
- F23G 5/46: Recuperation of heat
- F23G 5/50: Control or safety arrangements
- F23G 7/10: of field or garden waste {or biomasses}
- F23N 1/02: conjointly with air supply
- F23C 2900/06041: Staged supply of oxidant
- F23G 2202/106: with recirculation of unburned solid or gaseous matter into combustion chamber
- F23G 2203/00: Furnace arrangements
- F23G 2205/20: using airblast or pneumatic feeding
- F23G 2206/203: with a power/heat generating installation
- F23G 2207/101: for temperature
- F23G 2207/102: for pressure
- F23G 2207/104: for CO or CO2
- F23G 2207/112: for waste supply flowrate
- F23G 2207/113: for oxidant supply flowrate
- F23G 2207/20: Waste supply
- F23G 2207/30: Oxidant supply
- Y02E 20/12: Heat utilisation in combustion or incineration of waste
- Y02E 50/10: Biofuels, e.g. bio-diesel
- Y02E 50/30: Fuel from waste, e.g. synthetic alcohol or diesel
- F23N: REGULATING OR CONTROLLING COMBUSTION (control devices specially adapted for combustion apparatus in which combustion takes place in a fluidised bed of fuel or other particles F23C10/28; condition responsive controls for regulating combustion in domestic stoves with open fires for solid fuel F24B1/187)
- F23C: METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN {A CARRIER GAS OR} AIR (burners F23D)
- F23D: BURNERS
- F23G: CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

The burner preferably exclusively burns substantially explosible solid fuels and preferably has instant ON-OFF thermostat control, wastes no energy preheating the enclosure or external air supply, achieves stable combustion the moment the powder-air mix is ignited in our burner, is used in the upward vertical mode except for oil burner retrofits, burns a solid fuel in a single-phase regime as if it were a vaporized liquid or gas, is designed to complete combustion within the burner housing itself rather than in a large, high temperature furnace enclosure which it feeds, has an ultra-short residence time requirement, is a recycle consuming burner with self-contained management of initially unburned particles, is much smaller, simpler and lower cost, has a wider dynamic range/turndown ratio, is more efficient in combustion completeness and thermal efficiency, and operates with air-fuel mix approximately at the flame speed.

## Claims

### Claim 1

A burner for two-stage combustion by deflagration of a dispersion of an explosible powder consisting of a plurality of solid particles having a size distribution substantially in an explosible size range for the solid particles in a carrier gas, the burner comprising:
a) a first enclosure sidewall having a closed inlet end and an open exhaust end opposite the closed inlet end, the first enclosure sidewall forming a first enclosure having a substantially cylindrical shape, the first enclosure including a first combustion stage;
b) an inlet nozzle having an exit into the first enclosure at the closed inlet end of the first enclosure, wherein the inlet nozzle opens unobstructedly and freely into the first enclosure to deliver a moving stream of the solid particles in the carrier gas to the first enclosure;
c) an ignition source located in the first enclosure downstream from the inlet nozzle;
d) a first flow-altering discontinuity, formed by a first diameter step increase from an inner diameter of the inlet nozzle to an inner diameter of the first enclosure sidewall, with a first discontinuity ratio of the inner diameter of the first enclosure sidewall to the inner diameter of the inlet nozzle in a range of 4.67 to 12;
e) at least one first radially-symmetrical flame-stabilizing opening permitting flow of a first controlled secondary gas through the first radially-symmetrical flame-stabilizing opening into the first enclosure, the first radially-symmetrical flame-stabilizing opening being located at the closed inlet end of the first enclosure, wherein the first radially-symmetrical flame-stabilizing opening is formed to direct the first controlled secondary gas along and then outward from a flow direction axis of the dispersion and recirculating along the first enclosure sidewall;
wherein the first flow-altering discontinuity and the first radially-symmetrical flame-stabilizing opening provide, in combination, turbulent mixing of the carrier gas, the first controlled secondary gas, and the solid particles, to promote initial particle heating, to shorten a length of a pre-heat zone, to promote flow of the first controlled secondary gas, and to provide combustion flame stabilization;
wherein the first enclosure is designed such that when the moving stream of the solid particles in the carrier gas enters the first enclosure from the inlet nozzle, a backflow causes the moving stream to diverge, thereby forming an explosible dispersion having a symmetrical mushroom-like shape and slowing to a flame speed of the explosible dispersion by virtue of the first flow-altering discontinuity and the first radially-symmetrical flame-stabilizing opening, wherein through turbulent recirculation mixes with the first controlled secondary gas to form the explosible dispersion at an equivalence ratio in an explosible range, and wherein the ignition source initially ignites the explosible dispersion; and
wherein a stream flow of the moving stream is regulatable to maintain an instantaneously stable stationary deflagrating flame wave front by combustion of the explosible dispersion, thermally sustained with non-radiative, gas-to-particle, conductive heat transfer, while emulating fluid mechanics of single phase gas combustion;
f) a second enclosure sidewall having an inlet end and an open exhaust end opposite the inlet end, the second enclosure sidewall extending downstream beyond the open exhaust end of the first enclosure sidewall to the open exhaust end of the second enclosure sidewall, the second enclosure sidewall forming a second enclosure having a substantially cylindrical shape, the second enclosure including a second combustion stage;
g) a second flow-altering discontinuity, formed by a second diameter step increase from the inner diameter of the first enclosure sidewall to an inner diameter of the second enclosure sidewall, with a second discontinuity ratio of the inner diameter of the second enclosure sidewall to the inner diameter of the first enclosure sidewall being in a range of 1.14 to 2.29 at the open exhaust end of the first enclosure sidewall;
h) at least one second radially-symmetrical flame-stabilizing opening permitting flow of a second controlled secondary gas through the second radially-symmetrical flame-stabilizing opening, the second radially-symmetrical flame-stabilizing opening being located downstream of the exhaust end of the first enclosure sidewall, wherein the second radially-symmetrical flame-stabilizing opening is formed to initially direct a radially symmetrical stream of the second controlled secondary gas inward in the second enclosure in a direction non-parallel to a central axis of the second enclosure, wherein the second controlled secondary gas is not externally pre-heated, is pressurized, and is actively provided at a velocity up to about 10 times the flame speed;
wherein the second flow-altering discontinuity and the second controlled secondary gas entering through the second radially-symmetrical flame-stabilizing opening provide, in combination, an induced backflow recirculation to further combust any remaining solid particles and to promote a turbulent flow inside the second combustion stage to mix an efflux from the first enclosure with the second controlled secondary gas, to increase a rate of heating of the second controlled secondary gas by the efflux, to decrease a length of a final burnout zone, to sustain flame stabilization, and to insure combustion completion;
wherein the carrier gas, the first controlled secondary gas, and the second controlled secondary gas comprise, in combination, sufficient oxidizing gas to completely combust the solid particles; and
wherein heating of the solid particles in the first stage relies on gas-to-particle conduction and heating of the second controlled secondary gas in the second stage relies on particle-to-gas conduction, not on any thermal refractory structure for heat retention or radiative heating or any external thermal energy, and flame stabilization does not rely on any active mechanical swirl inducing apparatus common to cyclonic and vortex suspension systems for increasing path length and residence time.

### Claim at position 2

2-6. (canceled)

### Claim 7 (depends on 1)

The burner of claim 1, wherein the first and second enclosures are vertically oriented such that the open exhaust end of the second enclosure is at the top.

### Claim at position 4

8-11. (canceled)

### Claim 12 (depends on 1)

The burner of claim 1, further comprising a de-agglomerization system comprising a screen located in the first enclosure and a vibrating transducer connected to the screen to break up agglomerates of the solid particles.

### Claim 13 (depends on 1)

The burner of claim 1, wherein the first controlled secondary gas comprises a first portion mechanically controlled by the at least one first radially-symmetrical flame-stabilizing opening and a second portion actively supplied adjacent to the closed inlet end of the first enclosure sidewall arranged to create turbulent flow in the first enclosure.

### Claim at position 7

14-15. (canceled)

### Claim 16 (depends on 1)

The burner of claim 1, further comprising a flow restriction at the exhaust end of the second enclosure sidewall.

### Claim 17

(canceled)

### Claim 18

A burner system comprising:
a) a gas feed system supplying a flow of a carrier gas;
b) a powder fuel feed system supplying an explosible powder having a size distribution substantially in an explosible size range;
c) a mixing zone having inputs coupled to the gas feed system and the powder fuel feed system and an output comprising a moving stream of a dispersion of the solid particles in the carrier gas;
d) a burner comprising:
i) a first enclosure sidewall having a closed inlet end and an open exhaust end opposite the closed inlet end, the first enclosure sidewall forming a first enclosure having a substantially cylindrical shape, the first enclosure including a first combustion stage;
ii) an inlet nozzle coupled to the output of the mixing zone and having an exit into the first enclosure at the closed inlet end of the first enclosure, wherein the inlet nozzle opens unobstructedly and freely into the first enclosure to deliver the moving stream of the dispersion of the solid particles in the carrier gas to the first enclosure;
iii) an ignition source located in the first enclosure downstream from the inlet nozzle to initially ignite the dispersion;
iv) a first flow-altering discontinuity, formed by a first diameter step increase from an inner diameter of the inlet nozzle to an inner diameter of the first enclosure sidewall, with a first discontinuity ratio of the inner diameter of the first enclosure sidewall to the inner diameter of the inlet nozzle in a range of 4.67 to 12;
v) at least one first radially-symmetrical flame-stabilizing opening permitting flow of a first controlled secondary gas through the first radially-symmetrical flame-stabilizing opening into the first enclosure, the first radially-symmetrical flame-stabilizing opening being located at the closed inlet end of the first enclosure, wherein the first radially-symmetrical flame-stabilizing opening is formed to direct the first controlled secondary gas along and then outward from a flow direction axis of the dispersion and circulating along the first enclosure sidewall;
vi) a second enclosure sidewall having an inlet end and an open exhaust end opposite the inlet end, the second enclosure sidewall extending downstream beyond the open exhaust end of the first enclosure sidewall to the open exhaust end of the second enclosure sidewall, the second enclosure sidewall forming a second enclosure having a substantially cylindrical shape, the second enclosure including a second combustion stage;
vii) a second flow-altering discontinuity, formed by a second diameter step increase from the inner diameter of the first enclosure sidewall to an inner diameter of the second enclosure sidewall, with a second discontinuity ratio of the inner diameter of the second enclosure sidewall to the inner diameter of the first enclosure sidewall being in a range of 1.14 to 2.29 at the open exhaust end of the first enclosure sidewall; and
viii) at least one second radially-symmetrical flame-stabilizing opening permitting flow of a second controlled secondary gas through the second radially-symmetrical flame-stabilizing opening, the second radially-symmetrical flame-stabilizing opening being located downstream of the open exhaust end of the first enclosure sidewall, wherein the second radially-symmetrical flame-stabilizing opening is formed to initially direct a radially-symmetric stream of the second controlled secondary gas inward in the second enclosure in a direction non-parallel to a central axis of the second enclosure, wherein the second controlled secondary gas is not externally pre-heated, is pressurized, and is actively provided at a velocity up to about 10 times the flame speed; and
e) a control system coupled to the gas feed system and the powder fuel feed system, wherein the control system regulates the flow of the carrier gas such that the moving stream slows to a flame speed of the moving stream at an equivalence ratio in the explosible range downstream of the inlet nozzle to maintain a stable stationary flame front within the first enclosure.

### Claim 19 (depends on 18)

The system of claim 18, wherein the gas feed system supplies the second controlled secondary gas and the control system further regulates the flow of the second controlled secondary gas from the gas feed system to achieve a predetermined level of combustion completeness of the explosible powder at the open exhaust end.

### Claim 20 (depends on 18)

The system of claim 18, further comprising at least one additional air inlet to the mixing zone for entry of an accelerating gas to accelerate the moving stream and break up agglomerates of the solid particles prior to entry into the first enclosure.

### Claim at position 13

21-22. (canceled)

### Claim 23 (depends on 18)

The system of claim 18, wherein the control system comprises at least one sensor.

### Claim at position 15

24-27. (canceled)

### Claim 28 (depends on 18)

The system of claim 18, wherein the powder fuel feed system comprises an auger.

### Claim 29 (depends on 18)

The system of claim 18, wherein, for a preset BTU per hour output, the control system also regulates the first controlled secondary gas to maintain the moving stream at the equivalence ratio in the explosible range downstream of the inlet nozzle and to maintain the stable stationary flame front within the first enclosure, wherein the first controlled secondary gas is actively provided by the gas feed system.

### Claim 30

A furnace comprising:
a) a gas feed system supplying a flow of a carrier gas;
b) a powder fuel feed system supplying an explosible powder having a size distribution substantially in an explosible size range;
c) a mixing zone having inputs coupled to the gas feed system and the powder fuel feed system and an output comprising a moving stream of a dispersion of the solid particles in the carrier gas;
d) a burner comprising:
i) a first enclosure sidewall having a closed inlet end and an open exhaust end opposite the closed inlet end, the first enclosure sidewall forming a first enclosure having a substantially cylindrical shape, the first enclosure including a first combustion stage;
ii) an inlet nozzle coupled to the output of the mixing zone and having an exit into the first enclosure at the closed inlet end of the first enclosure, wherein the inlet nozzle opens unobstructedly and freely into the first enclosure to deliver the moving stream of the dispersion of the solid particles in the carrier gas to the first enclosure;
iii) an ignition source located in the first enclosure downstream from the inlet nozzle to initially ignite the dispersion;
iv) a first flow-altering discontinuity, formed by a first diameter step increase from an inner diameter of the inlet nozzle to an inner diameter of the first enclosure sidewall, with a first discontinuity ratio of the inner diameter of the first enclosure sidewall to the inner diameter of the inlet nozzle in a range of 4.67 to 12;
v) at least one first radially-symmetrical flame-stabilizing opening permitting flow of a first controlled secondary gas through the first radially-symmetrical flame-stabilizing opening into the first enclosure, the first radially-symmetrical flame-stabilizing opening being located at the closed inlet end of the first enclosure, wherein the first radially-symmetrical flame-stabilizing opening is formed to direct the first controlled secondary gas along and then outward from a flow direction axis of the dispersion and recirculating along the first enclosure sidewall;
vi) a second enclosure sidewall having an inlet end and an open exhaust end opposite the inlet end, the second enclosure sidewall extending downstream beyond the open exhaust end of the first enclosure sidewall to the open exhaust end of the second enclosure sidewall, the second enclosure sidewall forming a second enclosure having a substantially cylindrical shape, the second enclosure including a second combustion stage;
vii) a second flow-altering discontinuity, formed by a second diameter step increase from the inner diameter of the first enclosure sidewall to an inner diameter of the second enclosure sidewall, with a second discontinuity ratio of the inner diameter of the second enclosure sidewall to the inner diameter of the first enclosure sidewall being in a range of 1.14 to 2.29 at the open exhaust end of the first enclosure sidewall; and
viii) at least one second radially-symmetrical flame-stabilizing opening permitting flow of a second controlled secondary gas through the second radially-symmetrical flame-stabilizing opening, the second radially-symmetrical flame-stabilizing opening being located downstream of the open exhaust end of the first enclosure sidewall, wherein the second radially-symmetrical flame-stabilizing opening is formed to initially direct a radially-symmetric stream of the second controlled secondary gas inward in the second enclosure in a direction non-parallel to a central axis of the second enclosure, wherein the second controlled secondary gas is not externally pre-heated, is pressurized, and is actively provided at a velocity up to about 10 times the flame speed;
e) a control system coupled to the gas feed system and the powder fuel feed system, wherein the control system regulates the flow of the carrier gas such that the moving stream slows to a flame speed of the moving stream at an equivalence ratio in the explosible range downstream of the inlet nozzle to maintain a stable stationary flame front within the first enclosure;
f) a heat exchanger thermally coupled to the exhaust end of the burner; and
g) a heating fluid circulation system thermally coupled to the heat exchanger.

### Claim 31 (depends on 30)

The furnace of claim 30, further comprising a flue gas particle filtration system for filtering flue gases from the burner.

### Claim 32 (depends on 30)

The furnace of claim 30, wherein the heating fluid is air, and the heating fluid circulation system comprises a blower blowing air through an air plenum.

### Claim at position 21

33-45. (canceled)

### Claim 46 (depends on 1)

The burner of claim 1, wherein flow of the first controlled secondary gas is passive and wherein the first flow-altering discontinuity and the first radially-symmetrical flame-stabilizing opening, in combination with the flow driven by eduction from the moving stream of the solid particles in the carrier gas flowing into the first enclosure, further energized by gas expansion as a result of combustion of a portion of the solid particles in a portion of at least one oxidizing gas in the carrier gas or the first controlled secondary gas, provide a reverse turbulent flow within the first enclosure.

### Claim 47 (depends on 1)

The burner of claim 1, wherein the first controlled secondary gas is actively provided.

### Claim 48 (depends on 18)

The system of claim 18, wherein the first controlled secondary gas is passively provided.

### Claim 49 (depends on 18)

The system of claim 18, wherein the first controlled secondary gas is actively provided.

### Claim at position 26

50-53. (canceled)