FI96717B - Process for improving the responsiveness of a PFBC plant - Google Patents

Description

96717

A method for improving the responsiveness of a PFBC plant

The invention relates to a method for improving the responsiveness of a PFBC plant having a compressor 5 for pressurizing a pressure vessel in a PFBC plant and a turbine operated from the PFBC plant which is mechanically connected directly to the compressor.

The PFBC plant is of the type disclosed in US-A-4660375.

10 When the power of a PFBC plant is to be increased while maintaining the allowable (optimal) efficiency, which means that the PFBC plant is to be operated with a substantially constant excess air coefficient regardless of the load condition (low power should be at a lower mass flow rate and higher power should be higher). degree of mass flow to the combustion chamber), then the pressure in the pressure vessel must be increased - the pressure vessel must be "loaded" - to increase the mass flow into the combustion chamber including a fluidized bed dryer (burner) 20 enclosed inside the pressure vessel. This load is carried out according to the current technology by increasing the speed of the compressor, which means that the compressor is operated separately.

However, the turbine unit is simpler in design and more reliable if the compressor is driven directly from the turbine shaft, but since such single-shaft turbine units, including the compressor, rotate at a constant speed, the compressor intake air volume per unit time (m3 / s) is always 30, also the mass of air in units of time (kg / s) is always constant regardless of the change in the degree of mass flow due to changes in the density of the intake air (outdoor air). In order for such a turbine unit to have a high reactivity while meeting the above requirement 35 to maintain the same excess air coefficient under all 2 96717 load conditions, which means varying the mass flow rate into the combustion chamber - partial load operation may require a mass flow rate drop of 40% full mass flow a load-5 - requires that the compressor be reconstructed and equipped with a large number of rows of rotating blades. This is expensive and greatly reduces the economic cost of operating a single-shaft turbine unit while negatively affecting plant responsiveness, as the large number of rotating blades makes the plant complex and can cause operational disruptions.

US-A-4 170 874 discloses a turbine unit comprising an expansion turbine with adjustable inlet control vanes connected to a compressor driven by the turbine. The compressor supplies air to the burner, which supplies gas to the turbine. To obtain optimal efficiency over the entire load range of the turbine unit, the expansion turbine acts as a compressor with a full 20 loads of the turbine unit.

In order to provide a rapid change in mass flow in a PFBC plant as discussed above for rapid loading of the pressure vessel when the power is to be increased, and thus to increase the reactivity of the plant using a less complex turbine unit, the method of the invention comprises the features of claim 1.

The plant comprises a gas generator of the PFBC type, comprising a pressure vessel 10 containing a combustion chamber 30 11 with one or more fluidized bed dryers to which. supplying pressurized air - fluidizing air and combustion air - from a pressure vessel and having a flue gas outlet 12. The heating coils 13 in the combustion chamber produce steam which is fed to a turbine 14 in a uniaxial turbine unit connected to il; ib.f connected I it a 3 96717 to an electric generator 15 to generate electric power. The single-shaft turbine unit also comprises a compressor 16 operated by a steam turbine 14 or an expansion turbine in which 5 flues of combustion gas from the combustion chamber 11 are supplied, and this compressor is connected from its pressure side to a pressure vessel 10, the compressor suction side taking air from the environment. also connected to the turbine unit shaft. The turbine 17 has symmetrical vane profiles and is provided with a ring 18 of rotating inlet vanes 10.

When the PFBC operates at part load, the vane ring is adjusted to give a relatively large drop in air flow. The air drawn in by the compressor 16 then expands in the turbine 17, causing the pressure to drop upstream of the compressor 15 and thus the lower density (relative to the ambient air) of the air drawn in by the compressor. Since the compressor rotates at a constant speed and thus always draws in the same volume flow (m3 / s), the intake mass flow (kg / s) is correspondingly smaller than the mass flow that should be drawn in by the compressor when the air is taken in directly from the environment and not the turbine. 17 through.

If the vane ring 18 is fully opened, the expansion turbine acts as a compressor, i.e. a supercharger 25 of the compressor 16, which means that the compressor 16 draws in air at a higher pressure and thus supplies a higher mass flow into the pressure vessel 10. This control is thus intended when the PFBC plant operates at full load. The adjustment of the vane ring 18 can be accomplished rapidly by a rapid change in mass flow from the compressor. ; 16, which means that the reactivity of the plant is high, because the pressure vessel 10 can be pressurized, loaded, as quickly as necessary to change the plant from partial load to full load.

4,96717

The permissible efficiency, i.e. the maintenance of essentially the same excess air coefficient over the entire load range of the PFBC plant, can be achieved by correctly sizing the compressor 16 and the turbine 17, which is within the knowledge of the average professional 5.

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Claims (1)

96717 Claim: • A method for improving the responsiveness of a PFBC plant when the plant has a compressor (16) for pressurizing the pressure vessel 5 (10) and a turbine (14) mechanically connected directly to the compressor from the PFBC plant, characterized in that from a low value to a high value, preferably a maximum value, the pressure in the pressure vessel (10) is increased by mechanically converting the expansion turbine (17) connected directly to the compressor (16) to act as a supercharger to increase the air mass flow from the compressor to the PFBC plant pressure vessel. «96717 For use in the reaction to the PFBC process, in the case of the PFBC process (16) for the production of three or more presses (10) and in the case of the PFBC process driven turbine (14) direct coupling with compressor, entry of a total of PFCB-anthropogenic effect frin that l & gt värde account that högt värde, fördelak-10 tigt account to maximal fever, Höjer man trycket i tryck-kärlet (10) genom att ändra en mechanically direct compressor (16) expansion expansion turbine (17) account for the compressor for the air mass flow in the compressor account PFBC-anläggningens tryckkärl. 15 n (* «* sai« Ίΐι r i ftfl.. I