| Mixed fuel coal burner for gas turbine engines -> Monitor Keywords |
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Mixed fuel coal burner for gas turbine enginesRelated Patent Categories: Power Plants, Combustion Products Used As Motive Fluid, Process, Having Fuel Conversion (e.g., Reforming, Etc.)Mixed fuel coal burner for gas turbine engines description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060236702, Mixed fuel coal burner for gas turbine engines. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] This invention is in the technical field of coal burners for furnaces and gas turbine engines. [0002] Prior efforts to burn coal in gas turbine engines, such as by use of pulverized coal, or coal in water slurries, have been unsatisfactory due to turbine blade maintenance problems, caused by coal ash particles being carried into the turbine blades, with the hot gases flowing therethrough. [0003] As a result, gas turbine engines, such as are used for electric power generation in combined cycle plants, today burn natural gas, or petroleum distillate fuels, and these fuels are increasingly in short supply, and thus expensive. [0004] As of October 2004, coal cost is about one-fifth of natural gas cost, per unit of energy. Known coal reserves are much greater than known petroleum and natural gas reserves, both nationally, and internationally. SUMMARY OF THE INVENTION [0005] In a mixed fuel coal burner of this invention, coal chunks pass through two separate reaction chambers in series. In the first, ODD, reaction chamber the coal is heated by a throughflow of hot gas, containing some oxygen, in order to carry out oxidative destructive distillation, ODD, of the coal volatile matter. The oxygen content of these hot gases is less than stoichiometric, relative to the coal volatile matter, so that partial oxidation of only the volatile matter occurs in the ODD reactor. Two fuel products thus emerge from the ODD reactor, a devolatilized coke product, which is passed into the second coke reactor, and a partially oxidized coal volatile matter gas. The partially oxidized coal volatile matter gas is mixed with an overfire air, and fully burned, in an ODD overfire burner, and the resulting burned gases pass into the turbine. Partially oxidized volatile matter can thus be burned cleanly in the ODD overfire burner, with greatly reduced creation of undesirable soot or tar, and this is one of the beneficial objects of this invention. [0006] The devolatilized coal chunks are delivered, by overfeed, into the top, or gas exit end of a bed of hot burning coke, in the second coke reactor. Primary air flows upward through the coke reactor and countercurrent to the coal chunk flow direction. The coke reacts rapidly with oxygen in the counterflowing primary air, and the resulting very hot burned gases quickly heat up entering coke chunks by connective heat transfer. The coke is thus burned up rapidly, and completely, to carbon monoxide and carbon dioxide while passing through coke reactor. This coke burn rate is proportional to the rate of supply of primary air into the coke reactor. Thus the power output of a gas burning engine, using this coal burner, can be controlled by control of the primary air flow rate into the coke reactor over a very wide range of engine power output, and corresponding coal burn rates. [0007] The exit gases from the second coke reactor are rich in carbon monoxide fuel, and these are mixed with additional overfire air, and burned fully to carbon dioxide, in a carbon monoxide overfire burner, and these fully burned gases flow into the turbine inlet nozzles. [0008] Prior art underfeed coal burners used a single reaction chamber to achieve similar clean burning of high volatile matter bituminous coals. With these underfeed burners, the coal and primary air moved in the same direction through the reactor. As a result, the fresh coal volatile matter evaporates into the oxygen rich incoming primary air. In this way the evaporating volatile matter receives the partial oxidation, needed for clean burning thereof, without soot and tar formation. But the entering coal chunks are heated up to rapid burning temperatures, by slow radiation heat transfer between chunks, and not by rapid convective heat transfer from hot burned gases. This radiation heat transfer rate, and hence the coal burn rate, is not only slow, but cannot be controlled by control of the primary air flow rate, as is needed for control of the power output of a gas turbine engine. [0009] This is another beneficial object of this invention, over the prior art, that high volatile matter bituminous coals can be burned cleanly, at a high burn rate, and that this burn rate can be controlled, over a wide range, by control of the rate of flow of primary air into the second coke reactor. [0010] With overfeed supply of coal chunks into the coke reactor final coke burnup to ashes occurs at the bottom of the second coke reactor, and the ash particles, which are smaller than the coal chunks, are restrained from being blown out of the coke reactor, and into the gas turbine engine, by the overlying coke bed. With prior art, underfeed coal burners, the small ash particles are formed at the top of the fuel bed, and can thus be blown out of the fuel bed, and into the gas turbine engine, resulting in turbine blade damage. [0011] It has been this carryover of ash particles, into the gas turbine engine, and resulting turbine blade damage, which has previously prevented the use of low cost, and readily available, coal fuels in gas turbine engines. At present, gas turbine engines, such as are widely used in combined cycle electric power generating plants, operate only on expensive natural gas, or petroleum distillate fuels. This is a principal beneficial objet of this invention, that low cost, ash containing, coals can be cleanly burned, in a gas turbine engine, without ash carryover into the turbine blades. [0012] A mixed fuel coal burner of this invention can additionally comprise a supplementary fuel air mixture overfire burner, which burns a gas or liquid fuel, such as natural gas, in the overfire space, above the coke fuel bed. This supplementary fuel burner can be used to control gas turbine engine speed very closely, as such burners can respond quickly to speed changes. The coal burner, while readily governable, responds slowly to speed changes, whereas in most applications, such as electric power generation, very close speed control is needed. [0013] This supplementary fuel air mixture overfire burner also provides a method for adjusting the relative fuel quantities being used by the gas turbine engine, and these quantities can then be changed, in response to changes in fuel prices and availability. BRIEF DESCRIPTION OF THE DRAWINGS [0014] A schematic diagram of an example form of mixed fuel coal burner, of this invention, is shown in FIG. 1. [0015] In FIG. 2 an example controller, for controlling a mixed fuel burner of this invention, is shown schematically for use on a gas turbine engine. [0016] Additional related controls are shown schematically on FIG. 3. [0017] The preferred operating regions, for the ODD reactor portion, of a mixed fuel coal burner of this invention, are shown graphically in FIG. 4. [0018] The preferred operation regions for the coke reactor portion, of a mixed fuel coal burner of this invention, are shown graphically in FIG. 5. [0019] The operating characteristics of an example generator of hot oxygen containing gases is shown graphically on FIG. 6. [0020] An example refuel mechanism for use on a mixed fuel coal burner is shown schematically in FIGS. 7 and 8. FIG. 8 is the cross section, A-A, of FIG. 7. FIG. 7 is the cross section, B-B, of FIG. 8. [0021] An example gas manifold and inlet ports system for admitting hot oxygen containing gases into an ODD reaction chamber is shown in cross section in FIG. 9. Continue reading about Mixed fuel coal burner for gas turbine engines... Full patent description for Mixed fuel coal burner for gas turbine engines Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Mixed fuel coal burner for gas turbine engines patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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