JPS59131803A - Steam injection control system - Google Patents

Abstract

PURPOSE:To suppress the lowering of the heat efficiency by appropriately controlling the steam injection (S/I) quantity based on the performance of an exhaust gas denitration device, in a combined plant in which a gas turbine, an exhaust heat recovery type boiler, and a steam turbine are combined. CONSTITUTION:The NOX concentration C2 22 at the outlet port of the boiler is subtracted in a subtractor 23 from the NOX concentration C1 21 at the outlet port of the gas turbine, and the output X of the subtractor 23 is divided in a divider 24 by the difference Y between the NOX concentration C10 at the outlet port of the gas turbine and the NOX concentration C20 at the outlet port of the boiler prior to the aged deterioration of the denitration device so as to obtain a denitration performance coefficient K. Furthermore, an S/I injection quantity correction bias L is obtained by a function 25. On the other hand, an S/I steam flow quantity M is calculated from a fuel quantity F1 20 in a function 26, and integrated with the S/I steam flow quantity correction bias L in a multiplier 27 to calculate the S/I quantity to be injected. A difference between the calculated value and the S/I quantity detected by a detector 28 is obtained by a subtractor 29, and P+I operation is added to the deviation in an operation device 30 thereby to control an S/I control valve 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to I) an eNOx control method, and particularly to a steam (or water) injection method suitable for a combined plant.

[Prior art]

In the conventional steam injection method (hereinafter referred to as S/1 and abbreviated as -r), the function of the fuel flow rate G of the gas turbine is P = Func (
G) is calculated and controlled as follows.

In recent plants, flue gas denitrification equipment and 8/1
A DeNOx system in combination with the above is common, and considering the performance of the denitrification equipment, it is extremely important to keep the S/1 ratio as low as possible in order to completely suppress the decline in efficiency. Moreover, since this denitrification device is subject to deterioration over time, it is necessary to establish a DeNOx control system that takes into account this point.

[Purpose of the invention]

The purpose of the present invention is to suppress a decrease in thermal efficiency in a combined plant that combines a gas turbine, an exhaust heat recovery boiler, and a steam turbine by appropriately controlling the amount of S/1 based on the performance of the flue gas denitrification equipment. It is in.

[Summary of the invention]

In a combined plant, a flue gas denitrification device installed in the exhaust heat recovery boiler and S/1 (also UW7T), which injects steam (or water) into the gas turbine combustor, are used in combination.
Achieves denitrification effect. However, since the two systems target different main engines (gas turbine and exhaust heat recovery boiler), they have been controlled independently. For this reason, in order to achieve the regulation value of NOx in exhaust gas, the temperature is excessively increased to S/1 (or W/1)', resulting in a significant decrease in thermal efficiency.

In the present invention, the denitrification performance of the flue gas denitrification equipment is fully utilized,
By achieving a denitrification effect that exceeds the capacity of S/1 (straight W/1), it suppresses the decrease in thermal efficiency due to the recent drop in gas turbine combustion temperature due to S/1 (W/1). be.

[Embodiments of the invention]

Hereinafter, an example to which the present invention is applied (in the case of steam injection) will be explained using Figures 1 and 2. In FIG. 1, combustion gas from a gas turbine passes through a duct 2, enters a boiler 3, passes through a denitrification device 4 installed in the boiler 3, and then heads to a chimney via a duct 5. On the other hand, the feed water discharged from the water supply pump 6 passes through the water supply pipe 7 and is sent to the boiler 3, where it becomes steam after heat exchange, is sent to the steam turbine 9 through the steam pipe 8, and is condensed in the condenser 10. Returned to the water pump again.

Extracted air from the steam turbine passes through the steam pipe 11, is cooled down by the attemperator 12, is flow-controlled by the 8/1 control valve 13, and is injected into the combustor 15 through the steam pipe 148.

After adjusting the flow rate of the fuel with the fuel flow control valve 16, the fuel is transferred to the pipe 1.
7 to the combustor 15.

On the other hand, ammonia is sent to the boiler 3 via a pipe 19 after its flow rate is adjusted by an ammonia flow control valve 18 .

The fuel flow rate is detected by a detector 20, the gas turbine outlet N()x concentration is detected by a detector 21, and the boiler outlet NOx concentration is detected by a detector 22, and each signal is taken into the split section 1 device 23, as shown in FIG. Perform such control. The details will be explained below.

Gas turbine outlet NOx concentration C, 21, 1: Reboiler outlet NOx concentration C7227 Subtracted by subtractor 23, its output Concentration C2o
The difference Y (constant value given as a reference value) is divided by the divider 24 to obtain the denitrification performance coefficient ? obtain. Furthermore, all these inputs are used to obtain S/1 injection amount correction bias Lt using function 25.

On the other hand, fuel flow rate 1? ', 20rs, S/1 in function 26
Steam flow 1″
1 Calculate f%'. The subtractor 29 calculates the deviation between this value and S/1 t detected by the detector 28, and the arithmetic unit 30 adds the P+I operation to the difference, and the S/1 control (
Financial) Control valve 13.

〔Effect of the invention〕

According to the present invention, a change in performance of a flue gas denitrification device is detected, and (
This is reflected in ThS/1 control, and by achieving a control function that calculates the minimum required amount of 8/1 to control DeNOx as a total, It becomes possible to suppress the decrease in thermal efficiency due to S/1 of the steam turbine, and at the same time, by reducing steam turbine extraction, it is possible to achieve a large efficiency improvement compared to the conventional method.

In addition, from the perspective of environmental performance, performance-enhancing pipes can be used to suppress the amount of water vapor released into the atmosphere.
Accordingly, the amount of water consumed by the plant can be reduced.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a plant according to an embodiment of the present invention, and FIG. 2 is a control system diagram.

Claims (1)

[Claims] 1. In the NOx reduction technique of flue gas, which is performed by combining a flue gas denitrification device based on the dry ammonia catalytic reduction method and a steam injection method (or water injection method) that completely injects steam (or water) into the combustor, Based on the denitrification ability of the smoke denitrification equipment, this steam injection shaft system is characterized by suppressing the decline in thermal efficiency and achieving specified environmental performance.