Patent Application
20120312889
The subject matter disclosed herein relates to gasification and combustors. More particularly, the subject disclosure relates to injector nozzles for gasification.
Many known integrated gasification combined-cycle (IGCC) plants include a gasification system that is integrated with at least one power-producing turbine system. For example, at least some known gasification systems convert a mixture of fuel, air or oxygen, steam, and/or CO2 into a synthetic gas, or “syngas”. The sysngas is channeled to the combustor of a gas turbine engine, which powers an electrical generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator (HRSG) that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.
At least some gasification systems include an injection system that supplies a gasifier reactor with process fluids to facilitate at least one exothermic reaction. Some gasification systems use multiple types of fuel to drive the gasification process. For example, a coal gasification plant primarily utilizes a coal slurry as fuel to drive gasification which converts the carbon in the coal into a gaseous fuel to produce electricity. When the gasifier is initialized, however, the system components downstream of the gasification chamber are not yet at a design point operating pressure, so the process efficiency is lacking. Thus, gasification of the coal slurry produces a higher amount of undesirable emissions such as sulfur and/or NOx until the downstream components are brought up to pressure.
In an attempt to alleviate these emissions issues, cleaner burning fuels, such as natural gas are often introduced into the gasification chamber during startup in place of the coal slurry. The natural gas is injected into the gasifier via a dedicated nozzle separate from that of the coal slurry.
According to one aspect of the invention, an injector tip for a gasifier combustor nozzle includes a center body having a plurality of center body openings at a distal end configured to inject a fuel flow into a combustion zone of the combustor. One or more fuel passages are arranged around the center body and are configured to inject a fuel slurry into the combustion zone. One or more oxygen passages are arranged around the center body and are configured to inject an oxygen flow into the combustion zone.
According to another aspect of the invention, a method of fuel injection into a combustor includes injecting a first portion of a fuel flow into a combustion zone of the combustor through a plurality of center body openings in a distal end of a center body of an injector tip. A second portion of the fuel flow is injected into the combustion zone via one or more fuel passages arranged around the center body. The injection of the second portion of the fuel flow is suspended and a fuel slurry is injected into the combustion zone via one or more fuel passages.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Shown in
A plurality of fuel passages, or lances, are arranged surrounding the center body 12. An inner passage 20 is located around the center body 12, and in some embodiments is concentric with the center body 12. A middle passage 22 is located around the center body 12 outboard of the inner passage 20, and in some embodiments is concentric with the center body 12 and/or the inner passage 20. As shown in
At startup of the gasifier, as shown in
Referring now to
During transitions in operation from, for example, startup operation and coal slurry mode operation, both fuel flow 32 and coal slurry 40 may be injected into the combustion zone 34, with the fuel flow 32 injected through the center body openings 16 and the coal slurry 40 injected through the middle passage 22. As the transition occurs from startup (all fuel flow 32) to coal slurry mode (all coal slurry 40), an amount of each flow can be gradually changed to provide a smooth transition between the two modes. For example, as the operation moves from startup to coal slurry mode, the amount of fuel flow 32 injected through the center body openings 16 is gradually decreased while the amount of coal slurry 40 injected through the middle passage 22 is gradually increased. Further, switching between coal slurry mode and a standby mode, where the flow of coal slurry 40 is stopped and injection of the fuel flow 32 is resumed, can occur quickly since the nozzle tip 10 has the ability to inject either or both types of fuel via the separate center body 12 and middle passage 22.
In some embodiments, the inner tip end 26, the middle passage end 28, and/or the outer passage end 30 are flush with the distal end 18 of the center body 12. Having the ends all flush with each other prevents premixing of the fuels with the primary oxygen, which may be detrimental to performance of the gasifier. Further, the flush end configuration prevents burnback during coal slurry mode operation.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
