Multiple fuel combustion system and method
According to embodiments, a co-fired or multiple fuel combustion system is configured to apply an electric field to a combustion region corresponding to a second fuel that normally suffers from poor combustion and/or high sooting. Application of an AC voltage to the combustion region was found to increase the extent of combustion and significantly reduce soot evolved from the second fuel.
1. A co-fired combustion apparatus, comprising:
a first fuel-introduction body configured to provide a gaseous or liquid first fuel to a first combustion reaction;
a crucible;
a second fuel-introduction body configured to provide a second fuel to a second combustion reaction in the crucible, wherein the first fuel introduction body is positioned below the second fuel introduction body to cause the first combustion reaction to at least intermittently provide heat to the second combustion reaction; and
an electrode assembly associated with the second fuel introduction body or a second combustion volume to which the second fuel introduction body provides the second fuel, the electrode assembly being configured to be driven to or maintained at one or more first voltages selected to provide an electric field to the second combustion volume;
wherein the first fuel assembly is configured to produce a flame temperature that is sufficiently high to ignite combustion of the second fuel when a reaction activation energy of the second combustion reaction is reduced by application of the first voltage.
2. The co-fired apparatus of claim 1 , wherein the electrode assembly includes one or more electrodes proximate or within the second combustion region.
3. The co-fired apparatus of claim 1 , wherein the electrode assembly includes the second fuel-introduction body.
4. The co-fired apparatus of claim 1 , wherein a portion of the apparatus is enclosed within a housing.
5. The co-fired apparatus of claim 4 , wherein a portion of the housing is operable to be driven to or held at one or more second voltages.
6. The co-fired apparatus of claim 4 , wherein the electrode assembly comprises a portion of the housing.
7. The co-fired apparatus of claim 1 , wherein the electrode assembly comprises the second fuel-introduction body.
8. The co-fired apparatus of claim 1 , wherein the electrode assembly comprises the crucible.
9. The co-fired apparatus of claim 1 , wherein the first fuel-introduction body comprises a burner assembly.
10. The co-fired apparatus of claim 1 , wherein the first fuel-introduction body is operable to be driven to or held at one or more second voltages.
11. The co-fired apparatus of claim 1 , wherein the electrode assembly associated with the second combustion region is operable to increase combustion efficiency of the second combustion when the electrode assembly is driven to or held at the one or more first voltages.
12. The co-fired apparatus of claim 1 , wherein the second combustion produces a combustion product stream having a flow; and
wherein the electrode assembly associated with the second combustion region is operable to generate a combustion product stream flow having turbulent flow when the electrode assembly is driven to or held at the one or more first voltages.
13. The co-fired apparatus of claim 1 , wherein the second fuel is substantially solid.
14. The co-fired apparatus of claim 13 , wherein the second fuel forms a portion of a fluidized bed.
15. The co-fired apparatus of claim 1 , further comprising a stoker configured to introduce the second fuel to the second combustion region.
16. The co-fired apparatus of claim 1 , wherein a portion of the apparatus is enclosed within a flue, stack, or pipe configured to convey a combustion product stream generated by at least the second combustion.
17. The co-fired apparatus of claim 1 , wherein the first fuel includes at least one of natural gas, propane, butane, coal, or oil.
18. The co-fired apparatus of claim 1 , wherein the second fuel includes one or more of rubber, wood, glycerin, an industrial waste stream, a post-consumer waste stream, an industrial by-product, garbage, hazardous waste, human waste, animal waste, animal carcasses, forestry residue, batteries, tires, waste plant material, or landfill waste.
19. The co-fired combustion apparatus of claim 1 , further comprising:
a first burner assembly configured to support the first combustion; and
a burner support configured to support the first burner assembly in a housing.
20. A method of co-fired combustion comprising:
maintaining a first combustion by combusting a gaseous or liquid first fuel at a first combustion region having a portion defined by a first fuel-introducing body;
maintaining a second combustion by combusting a second fuel at a crucible located in a second combustion region, located above the first combustion region and having a portion defined by a second fuel-introducing body;
positioning the first combustion region relative to the second combustion region to cause the first combustion to provide heat to the second combustion reaction; and
applying at least one first electrical potential, having a first value, proximate to the second combustion region;
wherein the first fuel produces a flame temperature that is sufficiently high to ignite combustion of the second fuel when a reaction activation energy of the second combustion is reduced by application of the first electrical potential.
21. The method of claim 20 , further comprising:
applying at least one second electrical potential, having a second value, proximate to the first combustion region.
22. The method of claim 20 , further comprising:
applying at least one second electrical potential at another location proximate to the second combustion region.
23. The method of claim 22 , further comprising:
conveying a combustion product stream generated by at least the second combustion through a flue, stack or pipe.
24. The method of claim 22 , wherein
the other location proximate to the second combustion includes the crucible,
the crucible is metallic, and
the second electrical potential is applied to the crucible.
25. The method of claim 22 , wherein the first fuel assembly is configured to produce a flame temperature that is at or above the autoignition temperature of the second fuel.
26. The method of claim 20 , wherein an electrode assembly is operable to apply the at least one first electrical potential, and wherein the electrode assembly comprises one or more electrodes proximate to the second combustion region.
27. The method of claim 26 , wherein the electrode assembly associated with the second combustion region is operable to increase combustion efficiency of the second combustion when the electrode assembly applies the one or more first electrical potential, compared to not applying the one or more first electrical potential.
28. The method of claim 20 , wherein the second combustion produces a combustion product stream comprising particulates; and
wherein the electrode assembly associated with the second combustion region is operable to increase combustion of the particulates in the combustion product stream when the electrode assembly applies the one or more first electrical potential.
29. The method of claim 20 , wherein the second combustion produces a combustion product stream having a flow; and
wherein applying the first electrical potential proximate to the second combustion region is operable to generate a combustion product stream flow having greater turbulence than another flow having substantially equal Reynolds number with no electrical potential applied.
30. The method of claim 20 , further comprising introducing the second fuel to the second combustion region with a stoker.
31. The method of claim 20 , wherein the second fuel is substantially solid.
32. The method of claim 20 , wherein the second fuel includes one or more of rubber, wood, glycerin, an industrial waste stream, a post-consumer waste stream, an industrial by-product, garbage, hazardous waste, human waste, animal waste, animal carcasses, forestry residue, batteries, tires, waste plant material, or landfill waste material.
33. The method of claim 20 , wherein the first fuel includes natural gas, propane, butane, or oil.
34. The method of claim 20 , wherein the first combustion region is separated from the second combustion region.
35. The method of claim 20 , wherein the first combustion region extends to overlap or occupy the second combustion region.
36. The method of claim 20 , wherein the second fuel includes one or more of rubber, wood, glycerin, an industrial waste stream, a post-consumer waste stream, an industrial by-product, garbage, hazardous waste, human waste, animal waste, animal carcasses, forestry residue, batteries, tires, waste plant material, or landfill waste.