Flue gas waste heat utilization device of fuel gas-steam combined cycle system

Abstract

The utility model discloses a flue gas waste heat utilization device of a gas-steam combined cycle system, and relates to the technical field of energy conversion and heat energy recovery, in the device, a first generator is connected with a gas turbine, the other end of the gas turbine is connected with a waste heat boiler, and the waste heat boiler is connected with a circulating pump, a steam turbine and a second heat exchanger through a low-pressure steam pocket; the low-pressure steam drum is a component of the waste heat boiler; the other end of the second heat exchanger is connected with the chimney; the steam turbine is connected with the second generator and one end of the first condenser; the other end of the first condenser is connected with the circulating pump; the low-pressure steam pocket is connected with a first heat exchanger through a first valve, and the first heat exchanger is connected with a booster pump and a turbine and further connected with a circulating pump through a second valve. The turbine is connected with the third generator and the second condenser which is connected with the booster pump. By means of the device, waste heat in the gas-steam combined cycle system can be effectively recycled, and the heat efficiency of the whole system is improved.

Description

Technical Field

[0001] This application relates to the field of energy conversion and heat recovery technology, and in particular to a device for utilizing waste heat from flue gas in a gas-steam combined cycle system. Background Technology

[0002] A combined cycle gas-steam system can fully utilize the energy of natural gas. This system consists of major equipment such as a gas turbine, waste heat boiler, steam turbine, condenser, and generator. The waste heat boiler can be further divided into dual-pressure and triple-pressure waste heat boilers.

[0003] For dual-pressure waste heat boilers, the flue gas temperature is generally high, mostly exceeding 90℃, and some even reaching 130℃. However, the flue gas temperature of advanced triple-pressure waste heat boilers can be reduced to 70℃. Therefore, dual-pressure waste heat boilers have a large flue gas heat loss and there is still room for further reduction.

[0004] However, due to the use of a dual-pressure waste heat boiler, the feedwater flow rate of the waste heat boiler is limited in order to ensure that both high-pressure and low-pressure water can be fully vaporized. This results in the normal feedwater not being able to fully absorb the waste heat of the flue gas, thus causing the exhaust gas temperature to be high. Utility Model Content

[0005] The purpose of this application is to provide a waste heat utilization device for a gas-steam combined cycle system, which uses a waste heat power generation system with a low-boiling-point circulating working fluid to increase the water flow rate into the waste heat boiler, effectively reducing the flue gas temperature and achieving deep utilization of the flue gas waste heat.

[0006] To achieve the above objectives, this application provides the following solution:

[0007] In a first aspect, this application provides a waste heat recovery device for a gas-steam combined cycle system, comprising: a gas turbine, a first generator, a waste heat boiler, a circulating pump, a first condenser, a second generator, a first heat exchanger, a chimney, a low-pressure steam drum, a second heat exchanger, a turbine, a second condenser, a third generator, a booster pump, a first valve, and a second valve.

[0008] The first generator is connected to a gas turbine, and the other end of the gas turbine is connected to a waste heat boiler. The waste heat boiler is connected to a circulating pump, a steam turbine, and a second heat exchanger via a low-pressure steam drum at its upper end. The low-pressure steam drum is a component of the waste heat boiler. The other end of the second heat exchanger is connected to a chimney. The steam turbine is connected to the second generator and one end of the first condenser. The other end of the first condenser is connected to the circulating pump. The low-pressure steam drum is connected to the first heat exchanger via a first valve. The first heat exchanger is connected to a booster pump and a turbine, and also to the circulating pump via a second valve. The turbine is connected to the third generator and the second condenser, and the second condenser is connected to the booster pump.

[0009] Optionally, the hot water outlet of the second heat exchanger is connected to the inlet of the waste heat boiler; the inlet of the second heat exchanger is connected to the outlet of the circulating pump for heating the water pumped in.

[0010] Optionally, a pipe is installed on the low-pressure steam drum; the low-pressure steam drum is connected to the first heat exchanger through the pipe; and a first valve is installed on the pipe.

[0011] Optionally, the first heat exchanger is used to receive saturated water from the low-pressure steam drum and release heat in the first heat exchanger to turn the saturated water into room temperature water.

[0012] Optionally, the pressurizing pump is used to pressurize the low-boiling-point working fluid and send the pressurized working fluid into the heat exchanger to absorb the heat released by the saturated water and vaporize it.

[0013] Optionally, the pressurized low-boiling-point working fluid includes Freon.

[0014] Optionally, the vaporized steam is used to expand and do work in the turbine, and the turbine is used to discharge the exhaust steam into the second condenser.

[0015] Optionally, the second condenser is used to condense the exhaust steam in the turbine into liquid and feed the liquid into a booster pump.

[0016] Optionally, the first valve and the second valve are automatic control valves.

[0017] Optionally, the fuel for the gas turbine includes natural gas, liquefied petroleum gas, coalbed methane, and biomass gas.

[0018] According to the specific embodiments provided in this application, the following technical effects are disclosed:

[0019] This application provides a waste heat recovery device for a gas-steam combined cycle system. The device includes: a gas turbine, a first generator, a waste heat boiler, a circulating pump, a first condenser, a second generator, a first heat exchanger, a chimney, a low-pressure steam drum, a second heat exchanger, a turbine, a second condenser, a third generator, a booster pump, and first and second valves. The specific connections are as follows: the first generator is connected to the gas turbine, and the other end of the gas turbine is connected to the waste heat boiler. The waste heat boiler is connected to the circulating pump, the steam turbine, and the second heat exchanger via the low-pressure steam drum at its upper end; the low-pressure steam drum is a component of the waste heat boiler; the other end of the second heat exchanger is connected to the chimney; the steam turbine is connected to the second generator and one end of the first condenser; the other end of the first condenser is connected to the circulating pump; the low-pressure steam drum is connected to the first heat exchanger via the first valve; the first heat exchanger is connected to the booster pump and the turbine, and the first heat exchanger is also connected to the circulating pump via the second valve; the turbine is connected to the third generator and the second condenser, and the second condenser is connected to the booster pump. Through this carefully designed layout, the system can effectively recover the waste heat discharged from the gas turbine and turbine, which is used to heat water to generate steam, and then drive the steam turbine and turbine to generate electricity, significantly improving the energy utilization efficiency of the entire system. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a waste heat recovery device for a gas-steam combined cycle system provided in one embodiment of this application.

[0022] Explanation of reference numerals in the attached figures:

[0023] 1-Low-pressure steam drum, 2-First heat exchanger, 3-Turbine, 4-Second condenser, 5-Third generator, 6-Pressure pump, 7-First valve, 8-Second valve, 9-Second heat exchanger. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] like Figure 1 As shown, this embodiment provides a waste heat recovery device for a combined gas-steam system, comprising:

[0028] Gas turbine, first generator, waste heat boiler, circulating pump, first condenser, second generator, chimney, low-pressure steam drum 1, first heat exchanger 2, turbine 3, second condenser 4, third generator 5, pressurization pump 6, first valve 7, second valve 8, and second heat exchanger 9.

[0029] The first generator is connected to the gas turbine, and the other end of the gas turbine is connected to the waste heat boiler. The waste heat boiler is connected to the circulating pump, the steam turbine, and the second heat exchanger 9 via the low-pressure steam drum 1 at the upper end of the waste heat boiler. The low-pressure steam drum 1 is a component of the waste heat boiler. The other end of the second heat exchanger 9 is connected to the chimney. The steam turbine is connected to the second generator and one end of the first condenser. The other end of the first condenser is connected to the circulating pump. The low-pressure steam drum 1 is connected to the first heat exchanger 2 via the first valve 7. The first heat exchanger 2 is connected to the booster pump 6 and the turbine 3. The first heat exchanger 2 is also connected to the circulating pump via the second valve 8. The turbine 3 is connected to the third generator 5 and the second condenser 4. The second condenser 4 is connected to the booster pump 6.

[0030] In this embodiment, the gas turbine, the first generator, the waste heat boiler, the circulating pump, the first condenser, the second generator, the chimney, and the low-pressure steam drum 1 are the original equipment of the gas-steam combined cycle system. The first heat exchanger 2, the turbine 3, the second condenser 4, the third generator 5, the booster pump 6, the first valve 7, the second valve 8, and the second heat exchanger 9 are additional components added to the existing equipment to further utilize the exhaust waste heat of the waste heat boiler for power generation and improve the unit efficiency.

[0031] In this embodiment, the fuel for the gas turbine includes natural gas, liquefied petroleum gas, coalbed methane, and biomass gas.

[0032] Specifically, in this device, the first generator is connected to the gas turbine, and the other end of the gas turbine is connected to the waste heat boiler. The waste heat boiler is connected to the low-pressure steam drum 1, the circulating pump, and the chimney. The low-pressure steam drum 1 is connected to the first heat exchanger 2 via the first valve 7. The first heat exchanger 2 is connected to the booster pump 6 and the turbine 3. The first heat exchanger 2 is also connected to the circulating pump via the second valve 8. The turbine 3 is connected to the third generator 5 and the second condenser 4. The second condenser 4 is connected to the booster pump 6.

[0033] Pipelines are installed on the low-pressure steam drum 1 of the waste heat boiler. The pipelines are connected to the first heat exchanger 2. The first heat exchanger 2 is also connected to the turbine 3, the pressurization pump 6 and the inlet of the circulating pump. The outlet of the turbine 3 is connected to the second condenser 4. The second condenser 4 is also connected to the pressurization pump 6. The turbine 3 is connected to the third generator 5.

[0034] When the device is in operation:

[0035] For the existing equipment, natural gas operates within a gas turbine, powering a first generator. The hot flue gas from the gas turbine enters a waste heat boiler to produce steam. This steam then enters a steam turbine, expands, and drives a second generator. The exhaust steam from the waste heat boiler is discharged into the low-pressure steam drum 1. The exhaust steam from the steam turbine enters the first condenser and condenses into water. This water is pressurized by a circulating pump and heated by the second heat exchanger 9 before returning to the waste heat boiler to generate steam, which in turn drives the steam turbine to generate electricity. The entire gas turbine, waste heat boiler, and steam turbine system form a combined gas-steam power cycle, achieving full utilization of natural gas energy.

[0036] For the newly added equipment, a pipe is installed on the low-pressure steam drum 1 of the dual-pressure waste heat boiler to draw some of the saturated water from the steam drum into the first heat exchanger 2. In the first heat exchanger 2, heat is released, and the water becomes room temperature water. Then, after being depressurized by the second valve 8, it is discharged into the inlet of the circulating pump 7. Pressurized by the circulating pump, it re-enters the waste heat boiler to absorb heat. Simultaneously, a low-boiling-point working fluid, such as Freon, is pressurized by the booster pump 6 and enters the first heat exchanger 2 to absorb the heat released by the saturated water and vaporize. The vaporized steam then enters the turbine 3 to expand and do work. The exhaust steam is discharged into the second condenser 4, releases heat, condenses into liquid, and is pressurized again by the booster pump 6 before entering the first heat exchanger 2 to absorb heat, forming a low-temperature thermodynamic cycle. The turbine 3 drives the third generator 5 to generate electricity, thus achieving the purpose of utilizing the waste heat of the flue gas. When the first heat exchanger 2, turbine 3, second condenser 4, third generator 5, or booster pump 6 malfunction or require maintenance, closing the first valve 7 and the second valve 8 will disconnect the waste heat power generation part from the system, thus not affecting the normal operation of the original combined power cycle system.

[0037] Specifically, the first valve 7 and the second valve 8 are automatic control valves.

[0038] Specifically, the third generator 5 is directly driven by the turbine 3.

[0039] In summary, this application has the following beneficial effects:

[0040] This application adds a waste heat power generation system using a low-boiling-point circulating working fluid to the original gas-steam combined cycle system, which increases the water flow into the waste heat boiler, effectively reducing the flue gas temperature and realizing the deep utilization of flue gas waste heat.

[0041] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the device and its core ideas. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A waste heat recovery device for flue gas in a combined gas-steam cycle system, characterized in that, include: Gas turbine, first generator, waste heat boiler, circulating pump, first condenser, second generator, first heat exchanger, chimney, low-pressure steam drum, second heat exchanger, turbine, second condenser, third generator, booster pump, first valve and second valve; The first generator is connected to a gas turbine, and the other end of the gas turbine is connected to a waste heat boiler. The waste heat boiler is connected to a circulating pump, a steam turbine, and a second heat exchanger via a low-pressure steam drum at its upper end. The low-pressure steam drum is a component of the waste heat boiler. The other end of the second heat exchanger is connected to a chimney. The steam turbine is connected to the second generator and one end of the first condenser. The other end of the first condenser is connected to the circulating pump. The low-pressure steam drum is connected to the first heat exchanger via a first valve. The first heat exchanger is connected to a booster pump and a turbine, and also to the circulating pump via a second valve. The turbine is connected to the third generator and the second condenser, and the second condenser is connected to the booster pump.

2. The waste heat recovery device for a gas-steam combined cycle system according to claim 1, characterized in that, The hot water outlet of the second heat exchanger is connected to the inlet of the waste heat boiler; the inlet of the second heat exchanger is connected to the outlet of the circulating pump for heating the water pumped in.

3. The waste heat recovery device for a gas-steam combined cycle system according to claim 1, characterized in that, The low-pressure steam drum is equipped with a pipe; the low-pressure steam drum is connected to the first heat exchanger through the pipe; and a first valve is installed on the pipe.

4. The waste heat recovery device for a gas-steam combined cycle system according to claim 1, characterized in that, The first heat exchanger is used to receive saturated water from the low-pressure steam drum and release heat in the first heat exchanger to turn the saturated water into room temperature water.

5. The waste heat recovery device for a gas-steam combined cycle system according to claim 1, characterized in that, The pressurizing pump is used to pressurize the low-boiling-point working fluid and send the pressurized working fluid into the heat exchanger to absorb the heat released by the saturated water and vaporize it.

6. The waste heat recovery device for a gas-steam combined cycle system according to claim 5, characterized in that, The pressurized low-boiling-point working fluid includes Freon.

7. The waste heat recovery device for a gas-steam combined cycle system according to claim 4, characterized in that, The vaporized steam is used to expand and do work in the turbine, and the turbine is used to discharge the exhaust steam into the second condenser.

8. The waste heat recovery device for a gas-steam combined cycle system according to claim 1, characterized in that, The second condenser is used to condense the exhaust steam in the turbine into liquid and feed the liquid into a booster pump.

9. A waste heat recovery device for a gas-steam combined cycle system according to claim 1, characterized in that, The first valve and the second valve are automatic control valves.

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