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There are two reasons for the rapid increase of FBC in combustors. First, the liberty of choice in respect of fuels in general, not only the possibility of using fuels which are difficult to burn using other technologies, is an important advantage of fluidized bed combustion. The second reason, which
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is used to precipitate out sulfate during combustion, which also allows more efficient heat transfer from the boiler to the apparatus used to capture the heat energy (usually water tubes). The heated precipitate coming in direct contact with the tubes (heating by conduction) increases the efficiency.
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Fluidized--bed combustion evolved from efforts to find a combustion process able to control pollutant emissions without external emission controls (such as scrubbers-flue gas desulfurization). The technology burns fuel at temperatures of 1,400 to 1,700 °F (750-900 °C), well below the threshold where
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etc.) through which jets of air are blown to provide the oxygen required for combustion or gasification. The resultant fast and intimate mixing of gas and solids promotes rapid heat transfer and chemical reactions within the bed. FBC plants are capable of burning a variety of low-grade solid fuels,
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Atmospheric fluidized beds use limestone or dolomite to capture sulfur released by the combustion of coal. Jets of air suspend the mixture of sorbent and burning coal during combustion, converting the mixture into a suspension of red-hot particles that flow like a fluid. These boilers operate at
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APFBC. In more advanced second-generation PFBC systems, a pressurized carbonizer is incorporated to process the feed coal into fuel gas and char. The PFBC burns the char to produce steam and to heat combustion air for the gas turbine. The fuel gas from the carbonizer burns in a topping combustor
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A 1½ generation PFBC system increases the gas turbine firing temperature by using natural gas in addition to the vitiated air from the PFB combustor. This mixture is burned in a topping combustor to provide higher inlet temperatures for greater combined cycle efficiency. However, this uses
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emissions below levels mandated by
Federal standards. However, they have some disadvantages such as erosion on the tubes inside the boiler, uneven temperature distribution caused by clogs on the air inlet of the bed, long starting times reaching up to 48 hours in some cases.
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The first-generation PFBC system also uses a sorbent and jets of air to suspend the mixture of sorbent and burning coal during combustion. However, these systems operate at elevated pressures and produce a high-pressure gas stream at temperatures that can drive a
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CHIPPS. A CHIPPS system is similar, but uses a furnace instead of an atmospheric fluidized-bed combustor. It also has gas turbine air preheater tubes to increase gas turbine cycle efficiency. CHIPPS stands for combustion-based high performance power
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has become increasingly important, is the possibility of achieving, during combustion, a low emission of nitric oxides and the possibility of removing sulfur in a simple manner by using limestone as bed material.
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linked to a gas turbine, heating the gases to the combustion turbine's rated firing temperature. Heat is recovered from the gas turbine exhaust in order to produce steam, which is used to drive a conventional
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to the gas turbine topping combustor. The gas turbine exhaust supplies combustion air for the atmospheric circulating fluidized-bed combustor that burns the char from the PCFB partial gasifier.
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FBC systems fit into essentially two major groups, atmospheric systems (FBC) and pressurized systems (PFBC), and two minor subgroups, bubbling (BFB) and circulating fluidized bed (
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power output. These systems are also called APFBC, or advanced circulating pressurized fluidized-bed combustion combined cycle systems. An APFBC system is entirely coal-fueled.
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pollutants); it also avoids the ash melting problems related to high combustion temperature. The mixing action of the fluidized bed brings the flue gases into contact with a
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GFBCC. Gasification fluidized-bed combustion combined cycle systems, GFBCC, have a pressurized circulating fluidized-bed (PCFB) partial gasifier feeding fuel
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emissions. FBC boilers can burn fuels other than coal, and the lower temperatures of combustion (800 °C / 1500 °F) have other added benefits as well.
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Commercial FBC units operate at competitive efficiencies, cost less than today's conventional boiler units, and have SO
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and woody biomass, at high efficiency and without the necessity for expensive fuel preparation (e.g.,
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due to 10 times more heat transfer than other combustion processes because of burning particle.
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FBC has a lower combustion temperature of 750 °C whereas an ordinary boiler operates at 850 °C.
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Iso-thermal bed combustion as temperature in free belt and active belt remain constant.
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Less area is required for FBC due to high coefficient of convective heat transfer.
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is also emitted. However, burning at low temperatures also causes increased
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In its most basic form, fuel particles are suspended in a hot, bubbling
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Since this allows coal plants to burn at cooler temperatures, less
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nitrogen oxides form (at approximately 2,500 °F / 1400 °C, the
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EU regulation: Pollution from large combustion plants
259:, resulting in a higher overall efficiency for the
327:JEA Northside Generating Station (Jacksonville)
167:FBC has low sintering process (melting of Ash).
354:Simulation of a commercial CFB coal combustor
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251:, usually a higher priced fuel than coal.
128:in the combustion air combine to form
344:National Energy Technology Laboratory
338:References (Requires update in links)
318:zero-emissions coal-fired power plant
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220:Pressurized Fluidized Bed Combustion
211:Atmospheric Fluidized Bed Combustion
16:Technology used to burn solid fuels
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53:and other particulate materials (
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102:polycyclic aromatic hydrocarbon
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136:-absorbing chemical, such as
181:due to capture by limestone.
301:Chemical looping combustion
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73:FBC reduces the amount of
306:Circulating fluidized bed
174:due to lower temperature.
369:Power station technology
38:technology used to burn
28:Fluidized bed combustion
77:emitted in the form of
332:Pulverised fuel firing
216:atmospheric pressure.
177:Lower production of SO
170:Lower production of NO
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311:Fluidized bed reactor
186:combustion efficiency
23:FBC smoke tube boiler
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379:Chemical processes
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374:Energy conversion
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241:Advanced PFBC
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384:Fluidization
322:Grate firing
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47:fluidity bed
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249:natural gas
227:gas turbine
86:emissions.
68:pulverising
40:solid fuels
363:Categories
64:coal waste
36:combustion
316:FutureGen
138:limestone
88:Limestone
59:limestone
279:See also
237:system.
142:dolomite
119:nitrogen
108:Benefits
274:system.
184:Higher
146:sorbent
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268:syngas
155:and NO
134:sulfur
123:oxygen
75:sulfur
199:Types
126:atoms
121:and
55:sand
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205:CFB
140:or
51:ash
49:of
32:FBC
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93:NO
79:SO
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179:x
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