CN102337936A - Flue gas reheating combined cycle power system - Google Patents

Abstract

The invention discloses a flue gas reheating combined cycle power system belonging to the technical field of fossil fuel power cycle power generation. The power system proposed by the present invention has both the inherent high-efficiency characteristics of the combined cycle and the high-efficiency characteristics of the gas turbine and steam turbine reheating technology. The gas turbines in the original combined cycle power system are divided into high-pressure gas turbines and medium-pressure gas turbines. With "reheat" before entering the intermediate pressure gas turbine, the average temperature of the endothermic heat of the entire gas turbine cycle is increased, and the performance of the gas turbine cycle will be improved. The flue gas reheating combined cycle power system of the invention has the advantages of high energy efficiency, low cost and low emission, and the net heat efficiency is increased by 4-5% compared with the traditional combined cycle power plant.

Description

A flue gas reheating combined cycle power system

technical field

The invention belongs to the technical field of fossil fuel power cycle power generation, and in particular relates to a flue gas reheating combined cycle power system.

Background technique

In the era of continuous rising energy prices, fossil fuel energy will play an important role in the power industry for a long time. Therefore, the power industry has been working hard to develop new types of fossil fuel power cycles to achieve high efficiency. Combined cycle power system is one of the important options to improve the efficiency of power plants.

It is well known that reheating the gas between two gas turbines increases the average endothermic temperature of the entire gas turbine cycle. Thus, the performance of the gas turbine cycle will be improved. Reheating the flue gas with a heat exchanger between two gas turbines is difficult in practice because the flue gas temperature is too high. The present invention proposes the concept of non-thermal surface reheating to solve this problem. The gas in a high-pressure gas turbine is only partially combusted by controlling the flow of oxygen (or air). The combustion temperature of the high-pressure gas turbine is controlled by pressurizing the flue gas at the outlet of the waste heat boiler (HRSG) and mixing it into the high-pressure gas turbine. The temperature and pressure of the flue gas (including unburned gas) at the outlet of the high-pressure gas turbine decrease. When designing the power system, optimize the flue gas pressure at the inlet and outlet of the high-pressure gas turbine. In the combustor of an intermediate pressure gas turbine, an additional supply of oxygen (or air) is required to completely combust the gas. Through combustion, at the outlet of the combustion chamber, the flue gas temperature reaches the design value.

Due to important changes in system configuration, the flue gas conditions of a flue gas reheat combined cycle power system are completely different from those of a traditional combined cycle gas turbine. One of the changes is the gas pressure at the inlet of the high-pressure gas turbine. The higher the gas pressure, the higher the efficiency of the power system. The gas pressure at the inlet of the high-pressure gas turbine is expected to reach 350bar or even higher. However, this does not affect the main configuration of current gas turbine designs. The only change is that the cylinder (outer jacket) of the gas turbine is thickened to accommodate the high gas pressure. The current steam turbine working at the same pressure level can be used as a high pressure gas turbine. The cylinder structure of the current high-pressure steam turbine can be used to process high-pressure gas. Regardless, the insulation and cooling configuration of current gas turbine jackets should still be used to handle the high temperatures of the gas.

Contents of the invention

The object of the present invention is to provide a flue gas reheating combined cycle power system.

Applied to the flue gas reheating combined cycle power system of pure gas or liquid fuel (accompanying drawing 1), the flue gas compressor 1 is coaxially connected with the first air compressor 2, the high-pressure gas turbine 3 and the first generator 9. The compressed and recirculated flue gas from the gas compressor 1 enters the high-pressure gas turbine 3 together with the compressed air and high-pressure fuel gas from the first air compressor 2 for partial combustion and partial expansion. The high-pressure gas turbine 3 and the medium-pressure gas turbine 4 are connected through flue gas pipelines , the high-pressure gas exhaust from the high-pressure gas turbine 3 contains under-combusted gas and the compressed air from the second air compressor 5 enters the medium-pressure gas turbine 4 for complete combustion, and the medium-pressure gas turbine 4 and the second air compressor 5 and the second air compressor The two generators 10 are coaxially connected, the medium-pressure gas turbine 4 and the waste heat boiler 8 are connected through a flue, part of the flue gas at the outlet of the waste heat boiler 8 enters the flue gas compressor 1 through the flue gas pipe, and the other part is discharged into the atmosphere through the chimney, and the steam turbine 6 is coaxially connected with the third generator 11, the steam turbine 6 is connected with the condenser 7 through a steam channel, the steam turbine 6 is also connected with the waste heat boiler 8 through a steam pipeline, and the water pump 12 is connected with the condenser 7 and waste heat through a water pipeline in turn. 8 boilers are connected.

The fuel used in the flue gas reheating combined cycle power system is pure gas or liquid fuel.

Beneficial effects of the present invention: the flue gas reheating combined cycle power system of the present invention has the advantages of high energy efficiency, low cost and low emission, and the net thermal efficiency is increased by 4-5% compared with traditional combined cycle power plants.

Description of drawings

Accompanying drawing 1 is the schematic diagram of flue gas reheating combined cycle power system;

In the accompanying drawings, 1-flue gas compressor, 2-first air compressor, 3-connected high-pressure gas turbine, 4-medium-pressure gas turbine, 5-second air compressor, 6-steam turbine, 7-condenser, 8-waste heat boiler, 9-first generator, 10-second generator, 11-third generator, 12-water pump.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example 1

A flue gas reheating combined cycle power system, as shown in Figure 1, the flue gas compressor 1 is coaxially connected with the first air compressor 2, the high-pressure gas turbine 3 and the first generator 9, and the gas from the flue gas compressor 1 The compressed recirculated flue gas, together with the compressed air and high-pressure fuel gas from the first air compressor 2, enters the high-pressure gas turbine 3 for partial combustion and partial expansion. The high-pressure gas turbine 3 and the medium-pressure gas turbine 4 are connected through flue gas pipelines. The high-pressure gas exhaust gas from the gas turbine 3 contains under-combusted gas and the compressed air from the second air compressor 5 enters the medium-pressure gas turbine 4 for complete combustion, and the medium-pressure gas turbine 4 and the second air compressor 5 and the second generator 10 are coaxially connected, the medium-pressure gas turbine 4 and the waste heat boiler 8 are connected through a flue, part of the flue gas at the outlet of the waste heat boiler 8 enters the flue gas compressor 1 through the flue gas pipe, and the other part is discharged into the atmosphere through the chimney, and the steam turbine 6 and the first The three generators 11 are coaxially connected, the steam turbine 6 is connected to the condenser 7 through a steam channel, the steam turbine 6 is also connected to the waste heat boiler 8 through a steam pipeline, and the water pump 12 is connected to the condenser 7 and the waste heat boiler 8 through a water pipeline in turn .

The gas in the high-pressure gas turbine 3 is only partially combusted by controlling the flow of oxygen (or air). The combustion temperature of the high-pressure gas turbine is controlled by pressurizing the flue gas at the outlet of the waste heat boiler 8 and mixing it into the high-pressure gas turbine 3 . The flue gas (including unburned gas) at the outlet of the high-pressure gas turbine 3 enters the medium-pressure gas turbine 4 after the temperature and pressure decrease. When designing the power system, the flue gas pressure at the inlet and outlet of the high-pressure gas turbine 3 is optimized. In the combustor of the medium-pressure gas turbine 4, additional oxygen (or air) needs to be supplied to completely burn the residual gas. Through combustion, at the outlet of the combustion chamber, the flue gas temperature should reach the design value.

The higher the gas pressure at the inlet of the high-pressure gas turbine 3, the higher the efficiency of the power system. The gas pressure at the inlet of the high-pressure gas turbine is expected to reach 350bar or even higher. However, this does not affect the main configuration of current gas turbine designs. The only change is that the cylinder (outer jacket) of the gas turbine is thickened to accommodate the high gas pressure. The current steam turbine working at the same pressure level can be used as a high pressure gas turbine. The cylinder structure of the current high-pressure steam turbine can be used to process high-pressure gas. Regardless, the insulation and cooling configuration of current gas turbine jackets should still be used to handle the high temperatures of the gas. The net thermal efficiency of the flue gas reheating combined cycle power system proposed in this embodiment can be 4-5% higher than that of a traditional combined cycle power plant.

Claims (2)

1. A flue gas reheating combined cycle power system is characterized in that the flue gas compressor (1) is coaxially connected with the first air compressor (2) and the high-pressure gas turbine (3) and the first generator (9) , the compressed and recirculated flue gas from the flue gas compressor (1) enters the high-pressure gas turbine (3) together with the compressed air and high-pressure fuel gas from the first air compressor (2) for partial combustion and partial expansion, and the high-pressure gas turbine (3 ) is connected to the medium-pressure gas turbine (4) through a flue gas pipeline, and the high-pressure gas exhaust from the high-pressure gas turbine (3) contains incompletely burned gas and the compressed air from the second air compressor (5) enters the medium-pressure gas turbine ( 4) complete combustion, the medium pressure gas turbine (4) is coaxially connected with the second air compressor (5) and the second generator (10), the medium pressure gas turbine (4) and the waste heat boiler (8) are connected through the flue, Part of the flue gas at the outlet of the waste heat boiler (8) enters the flue gas compressor (1) through the flue gas pipe, and the other part is discharged into the atmosphere through the chimney. The steam turbine (6) is coaxially connected with the third generator (11), and the steam turbine (6) is connected to the condenser (7) through a steam channel, the steam turbine (6) is also connected to the waste heat boiler (8) through a steam pipeline, and the water pump (12) is connected to the condenser (7) and the waste heat boiler through a water pipeline in turn (8) connected. 2. The flue gas reheating combined cycle power system according to claim 1, wherein the fuel used in the flue gas reheating combined cycle power system is pure gas or liquid fuel.

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