A heating system equipped with a composite phase-change heat exchanger to recover waste heat from flue gas

Abstract

The present invention discloses a heating system in the field of clean heating technology that is equipped with a composite phase-change heat exchanger to recover waste heat from flue gas, which solves the technical problem of energy waste caused by direct or indirect emission of waste heat from flue gas. The heating system includes a steam drum, an ejector, a condenser, an exhaust steam reheater, and a condensate cooler. The steam drum is a special heat exchanger that can ensure that the water in the heat exchange tube bundle is maintained above 100°C, thereby ensuring that the water vapor in the flue gas will not be liquefied and corrode the pipeline, and at the same time can further increase the circulating water supply temperature and reduce the amount of steam extraction; the ejector can use a small amount of high-temperature and high-pressure steam as a primary fluid to inject the exhaust steam in the turbine into the condenser; the exhaust steam reheater is the main source of high-temperature and high-pressure steam, and can also directly use the high-temperature and high-pressure steam of other steam turbines as a backup steam source; the condensate cooler can further improve the efficiency of waste heat recovery.

Description

Technical Field

[0001] The invention relates to the technical field of clean heating, and in particular to a heating system equipped with a composite phase-change heat exchanger to recover waste heat from flue gas. Background Art

[0002] Cogeneration is a centralized heating method currently commonly used in northern my country. Common methods include traditional extraction and condensation heating, absorption heat pump heating technology and high back pressure transformation technology. These technologies are all heating solutions for the exhaust steam or exhaust gas of steam turbines, but often ignore the recovery of waste heat from flue gas carrying a large amount of energy.

[0003] After passing through the air precooler, the flue gas usually needs special cooling water to further cool and reduce the heat of the flue gas. In this process, not only the waste heat of the flue gas cannot be effectively utilized, but also additional energy consumption is added. Summary of the invention

[0004] The purpose of the present invention is to provide a heating system with a composite phase change heat exchanger to recover waste heat from flue gas, so as to solve the problems in the above background technology that the installation angle of the components cannot be adjusted, the installation of fixed photovoltaic brackets is cumbersome, and the installation is not very firm.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a heating system with a composite phase-change heat exchanger added to recover waste heat from flue gas, used for recovering waste heat from flue gas, comprising a steam turbine, the steam turbine comprising a steam turbine 1 and a steam turbine 2, a steam drum and a heat exchange tube bundle, the steam drum comprising a cold side and a hot side, the inlet and outlet of the hot side of the steam drum being connected to the inlet and outlet of the heat exchange tube bundle arranged in the flue gas, the inlet and outlet of the cold side of the steam drum being connected to a circulating water return pipe, the inlet pipe of the cold side of the steam drum being connected to the inlet of a spike heater, and a butterfly valve being further arranged on the inlet pipe of the cold side of the steam drum;

[0006] It also includes condenser, ejector, exhaust steam reheater, condensate cooler, drain cooler, gate valve, connecting bypass and bypass.

[0007] Preferably, the primary fluid inlet of the ejector is connected to the steam outlet of the exhaust steam reheater, and the secondary fluid inlet of the ejector is connected to the exhaust device of the steam turbine.

[0008] Preferably, the inlet of the exhaust steam reheater is connected to the exhaust steam pipeline through a pipeline, and a butterfly valve and a ball valve are provided on the exhaust steam pipeline; the outlet of the exhaust steam reheater is connected to the primary fluid inlet of the ejector through a pipeline, and a butterfly valve is provided on the outlet pipeline of the exhaust steam reheater.

[0009] Preferably, the communication bypass is connected to the steam outlet, and a butterfly valve is provided on the communication bypass.

[0010] Preferably, the condenser includes a cold side and a hot side, the hot side inlet of the condenser is connected to the outlet of the ejector through a pipeline, the hot side outlet of the condenser is connected to the hot side inlet of the condensate cooler through a pipeline, and the cold side inlet of the condenser is connected to the circulating water return pipe and the cold side outlet of the condensate cooler.

[0011] Preferably, the condensate cooler includes a cold side and a hot side, the hot side inlet of the condensate cooler is connected to the hot side outlet of the condenser through a pipeline, the hot side outlet of the condensate cooler is connected to the water inlet of turbine 1 through a pipeline, the cold side inlet and outlet of the condensate cooler are connected to the circulating water return pipe, and butterfly valves are provided on the connecting pipelines of the cold side inlet and outlet and the hot side inlet and outlet of the condensate cooler.

[0012] Preferably, the spike heater includes a cold side and a hot side, the hot side inlet of the spike heater is connected to the scheduling device of the intermediate pressure cylinder of the turbine, and the cold side inlet of the spike heater is connected to the outlet pipe of the upper stage condenser and the cold side outlet pipe of the steam drum.

[0013] Preferably, the drain cooler includes a cold side and a hot side, the hot side inlet of the drain cooler is connected to the hot side outlet of the spike heater through a pipeline, the hot side outlet of the drain cooler is connected to the water inlet of turbine 2 through a pipeline, the cold side inlet and outlet of the drain cooler are connected to the circulating water return pipe, and butterfly valves are provided on the connecting pipelines of the cold side inlet and outlet and the hot side inlet and outlet of the drain cooler.

[0014] Compared with the prior art, the beneficial effects of the present invention are: the waste heat of the flue gas can be fully utilized and used for heating, and at the same time, there is no need to consume other energy to reduce the flue gas temperature; the back pressure in the condenser is jointly determined by the ejector and the exhaust device of the turbine, and the adjustment is more free; the back pressure in the condenser is higher than the exhaust back pressure of the turbine, the outlet water temperature of the cooling water of the condenser is higher, and the exhaust steam reheater generates high-temperature and high-pressure steam by heating the exhaust steam, thereby reducing the energy consumption of high-temperature and high-pressure steam. In addition, in order to ensure the safe and stable operation of the system, the invention provides other alternative pipelines for the supply of high-temperature and high-pressure steam; the setting of the condensate cooler can further reduce the temperature of the condensate, recover the waste heat to the greatest extent, eliminate the cold end loss, and make the energy utilization rate of the entire waste heat recovery device reach 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 It is a schematic diagram of the structure of the present invention;

[0017] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0018] 1a. Steam turbine 1 1b. Steam turbine 2 2. Ejector 3. Exhaust steam reheater 4. Condenser 5. Peak heater 6. Condensate cooler 7. Drain cooler 8. Steam drum 9. Heat exchange tube bundle 10. Flue gas 11. Butterfly valve 12. Gate valve 13. Ball valve 14. Communication bypass 15. Bypass 16 Circulating water return pipe 17. Circulating water supply pipe. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] See also Figure 1 The present invention provides a technical solution: a heating system with a composite phase-change heat exchanger to recover waste heat from flue gas, which mainly realizes its function through a steam drum 8 and a heat exchange tube bundle 9. The steam drum 8 is divided into a cold side and a hot side. The hot side inlet and outlet are connected to the inlet and outlet of the heat exchange tube bundle 9 arranged in the flue gas 10, and the cold side inlet and outlet are connected to the circulating water return pipe 16. The cooling water is taken from the inlet of the peak heater 5. A butterfly valve 11 is arranged on the inlet pipe. It also includes a condenser 4 and its auxiliary equipment:

[0021] Among them, the ejector 2 has its primary fluid inlet connected to the exhaust steam reheater 3 or other multiple selected high-temperature and high-pressure steam outlet, and its secondary fluid inlet connected to the exhaust device of the steam turbine;

[0022] Among them, the exhaust steam reheater 3, its inlet is connected to the exhaust steam pipeline through a pipeline and an electric butterfly valve 11 and an electric ball valve 13 are provided on the pipeline, and its outlet is connected to the inlet of the primary fluid of the ejector 2 through a pipeline and an electric butterfly valve 11 is provided on the pipeline;

[0023] Among them, the communication bypass 14 connects different high-temperature and high-pressure steam outlets and an electric butterfly valve 11 is provided on the pipeline;

[0024] The condenser 4 is divided into hot and cold sides, the hot side inlet is connected to the outlet of the ejector 2 through a pipeline, the hot side outlet is connected to the hot side inlet of the condensate cooler 6 through a pipeline, and the cold side inlet is connected to the circulating water return pipe 16 and the cold side outlet of the condensate cooler 6, which is the main device for waste heat recovery;

[0025] Among them, the condensate cooler 6 is also divided into hot and cold sides, the hot side inlet is connected to the hot side outlet of the condenser 4 through a pipeline, the hot side outlet is connected to the water inlet of the turbine through a pipeline, and the cold side inlet and outlet are connected to the circulating water return pipe 16. The pipeline is equipped with an electric butterfly valve 11, which is another device for waste heat recovery. It is mainly used for waste heat recovery of condensate water of the high back pressure condenser 4. Its main purpose is to eliminate condensation loss and further improve energy utilization.

[0026] The peak heater 5 has a similar connection mode and function to the condenser 4, but the difference is that the outlet temperature of the cold side is higher, which can meet the user's requirements for the circulating water temperature in cold weather. In addition, the hot side inlet is directly connected to the exhaust device of the intermediate pressure cylinder of the steam turbine, and the cold side inlet is connected to the outlet pipe of the upper stage condenser 4 and the outlet pipe of the cold side of the steam drum 8;

[0027] Among them, the drain cooler 7 and the condensate cooler 6 also have similar connection methods and functions, the difference between them is that the inlet temperature of the hot side is higher;

[0028] The drum 8 is a special heat exchanger, and its heat exchange mode is indirect heat exchange, which can ensure that the water vapor in the flue gas is not liquefied. Specifically, the water temperature in the hot side tube bundle of the drum 8 can be higher than 100°C by adjusting the cooling water flow rate according to the cooling water temperature and the temperature and emission of the flue gas. The cooling water of the drum 8 is taken from the heating circulating water, which can not only heat the circulating water temperature and thus reduce the amount of gas extraction of the peak heater 5 and its use time, but also eliminate the need to use special cooling water to cool the drum 8.

[0029] Among them, the heat exchange tube bundle 9 has a pressure inside the tube higher than the pressure at the saturation temperature of 100°C, ensuring that the temperature of the water inside the tube is higher than 100°C, in order to prevent the water vapor in the flue gas from liquefying and corroding the tube bundle;

[0030] The ejector 2 is a steam ejector 2, which uses high-temperature and high-pressure steam to eject exhaust steam and thereby increase the back pressure in the condenser 4; on the one hand, it can increase the discharge temperature of the condensed water, and on the other hand, it can achieve the purpose of flexibly adjusting the back pressure of the condenser 4 and reduce the thermal and electrical coupling effect of the steam turbine;

[0031] Among them, the exhaust steam reheater 3, which heats the exhaust steam discharged from the steam turbine to generate high-temperature and high-pressure steam as the primary fluid for the ejector 2, is also the most economical primary fluid acquisition scheme in the present invention;

[0032] Among them, other high-temperature and high-pressure steam is used as an alternative for the primary fluid of the ejector 2, the purpose of which is to prevent the failure of the exhaust steam reheater 3 from causing the heating system to fail to work normally;

[0033] Among them, the communication bypass 14 is a pipeline for communicating between different types of primary fluids of the ejector 2, which can be used as an emergency solution when different equipment is overhauled or fails;

[0034] The above-mentioned condenser 4 and its ejector 2, exhaust steam reheater 3, condensate cooler 6 and other auxiliary equipment can be used as the primary heating of the entire heating system. Its circulating water outlet temperature is relatively high and it is the preferred cooling water source for the cooling water of the steam drum 8.

[0035] The working principle of the heating system equipped with a composite phase change heat exchanger to recover waste heat from flue gas is as follows:

[0036] The exhaust steam with waste heat is discharged from the turbine and enters the condenser 4 under the injection of the ejector 2. In this process, the ejector 2 can freely adjust the back pressure in the condenser 4 by changing the parameters of the ejector 2, and flexibly adjust the outlet temperature of the cooling water and the outlet temperature of the condensed water of the condenser 4. Then the condensed water enters the condensate cooler 6 through the pipeline, and the temperature of the condensed water is further reduced by the condensate cooler 6, in order to improve the utilization efficiency of energy. As a carrier for waste heat recovery, the circulating water mainly obtains heat through heat exchange with the condenser 4, supplemented by the condensate cooler 6 and the steam drum 8. The circulating water return water is divided into three parts and enters the condenser 4, the condensate cooler 6 and the drain cooler 7 respectively. After passing through the condenser 4, the circulating water is divided into two parts and enters the steam drum 8 and the peak heater 5 respectively. The primary fluid of the ejector 2 is mainly obtained through the exhaust steam reheater 3. For safety reasons, other multiple high-temperature and high-pressure steam inlets are also set.

[0037] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0038] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A heating system with a composite phase change heat exchanger for recovering waste heat from flue gas, for recovering waste heat from flue gas (10), comprising a steam turbine, wherein the steam turbine comprises a steam turbine 1 (1a) and a steam turbine 2 (1b), characterized in that: It also includes a steam drum (8) and a heat exchange tube bundle (9), wherein the steam drum (8) includes a cold side and a hot side, the hot side inlet and outlet of the steam drum (8) are connected to the inlet and outlet of the heat exchange tube bundle (9) arranged in the flue gas (10), the cold side inlet and outlet of the steam drum (8) are connected to a circulating water return pipe (16), the cold side inlet pipe of the steam drum (8) is connected to the inlet of a spike heater (5), and a butterfly valve (11) is also provided on the cold side inlet pipe of the steam drum (8); It also includes a condenser (4), an ejector (2), an exhaust steam reheater (3), a condensate cooler (6), a drain cooler (7), a gate valve (12), a connecting bypass (14) and a bypass (15); The primary fluid inlet of the ejector (2) is connected to the steam outlet of the exhaust steam reheater (3), and the secondary fluid inlet of the ejector (2) is connected to the exhaust device of the steam turbine; The inlet of the exhaust steam reheater (3) is connected to the exhaust steam pipeline through a pipeline, and a butterfly valve (11) and a ball valve (13) are provided on the exhaust steam pipeline; the outlet of the exhaust steam reheater (3) is connected to the primary fluid inlet of the ejector (2) through a pipeline, and a butterfly valve (11) is provided on the outlet pipeline of the exhaust steam reheater (3); The communication bypass (14) is connected to the steam outlet, and a butterfly valve (11) is provided on the communication bypass (14); The condenser (4) comprises a cold side and a hot side, the hot side inlet of the condenser (4) is connected to the outlet of the ejector (2) through a pipeline, the hot side outlet of the condenser (4) is connected to the hot side inlet of the condensate cooler (6) through a pipeline, and the cold side inlet of the condenser (4) is connected to the circulating water return pipe (16) and the cold side outlet of the condensate cooler (6); The condensate cooler (6) comprises a cold side and a hot side, the hot side inlet of the condensate cooler (6) is connected to the hot side outlet of the condenser (4) through a pipeline, the hot side outlet of the condensate cooler (6) is connected to the water inlet of the turbine (1a) through a pipeline, the cold side inlet and outlet of the condensate cooler (6) are connected to the circulating water return pipe (16), and butterfly valves (11) are provided on the connecting pipelines of the cold side inlet and outlet and the hot side inlet and outlet of the condensate cooler (6); The spike heater (5) comprises a cold side and a hot side, the hot side inlet of the spike heater (5) is connected to the scheduling device of the intermediate pressure cylinder of the steam turbine, and the cold side inlet of the spike heater (5) is connected to the outlet pipe of the upper stage condenser (4) and the cold side outlet pipe of the steam drum (8); The drain cooler (7) comprises a cold side and a hot side. The hot side inlet of the drain cooler (7) is connected to the hot side outlet of the spike heater (5) through a pipeline. The hot side outlet of the drain cooler (7) is connected to the water inlet of the second steam turbine (1b) through a pipeline. The cold side inlet and outlet of the drain cooler (7) are connected to the circulating water return pipe (16). Butterfly valves (11) are provided on the connecting pipelines of the cold side inlet and outlet and the hot side inlet and outlet of the drain cooler (7).

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