Closed flue gas waste heat utilization system

Abstract

The utility model provides a closed flue gas waste heat utilization system. Comprising a low-temperature economizer, a heating medium water input pipeline, a heating medium water output pipeline, a low-temperature economizer inlet valve, a low-temperature economizer outlet valve, a first bypass pipeline, a low-temperature economizer bypass valve, a heating medium steam heater, a heating medium steam heater inlet valve, a heating medium steam heating outlet valve and a second bypass pipeline. The utility model discloses a heating medium steam heater bypass valve and a heating medium water air heater. When the low-temperature economizer cannot operate, the heating medium water vapor heater is used for heating cold water, and heated hot water is used for heating cold air entering the heating medium water air heater, so that the temperature of hot air coming out of a hot air connector of the air pre-heater meets the requirement for entering the air pre-heater, and it is guaranteed that the comprehensive temperature of the cold end of the air pre-heater is met.

Description

Technical Field

[0001] The utility model belongs to the technical field of flue gas waste heat utilization in coal-fired thermal power plants, and more specifically, relates to a closed flue gas waste heat utilization system. Background Art

[0002] Boiler exhaust heat loss is one of the main heat losses in thermal power plants. The use of exhaust waste heat utilization system can reduce the exhaust temperature, greatly improve the economy of the power plant, and is one of the important ways to improve the thermal efficiency of the unit.

[0003] With the gradual development of flue gas waste heat utilization technology for coal-fired power units, one of the current mainstream flue gas waste heat utilization technologies is the low-temperature economizer-closed heat medium water heater combined with flue gas waste heat utilization technology, which uses closed heat medium water to absorb the flue gas waste heat of the low-temperature economizer to heat the air preheater inlet cold air required for boiler combustion. Figure 1 The existing low-temperature economizer-closed heat medium water heater combined with flue gas waste heat utilization system is demonstrated. The following problems are inevitable in the use of this system: 1) The exhaust temperature is too low at low load, and the flue gas waste heat utilization system cannot operate; 2) The low-temperature economizer is out of operation due to wear, corrosion and leakage, and the flue gas waste heat utilization system also cannot operate.

[0004] The above problems lead to the system being unable to heat the cold air at the air preheater inlet, resulting in the air preheater cold end comprehensive temperature failing to meet equipment requirements, leading to air preheater blockage, low temperature corrosion, and ammonium bisulfate cross-boundary corrosion. Therefore, it is necessary to design a reasonable and optimized flue gas waste heat utilization system that is suitable for closed, all-weather, and full-load operation. Utility Model Content

[0005] The purpose of the utility model is to provide a closed flue gas waste heat utilization system to ensure that the comprehensive temperature of the cold end of the air preheater is met, adapt to closed, all-weather, full-load working conditions, prevent the air preheater from clogging, low-temperature corrosion and ammonium bisulfate cross-boundary corrosion, and other problems, and the economic benefits are obvious.

[0006] To achieve the above-mentioned purpose, the utility model provides a closed flue gas waste heat utilization system, including a low-temperature economizer and a heat medium water heater, wherein the low-temperature economizer and the heat medium water heater are connected to form a circulation pipeline through a heat medium water input pipeline and a heat medium water output pipeline;

[0007] The low-temperature economizer is provided with a flue gas inlet, a flue gas outlet, a heat medium water inlet and a heat medium water outlet;

[0008] The heat medium water heater is provided with a cold air inlet, an air preheater hot air interface, a hot water inlet and a cold water outlet;

[0009] The two ends of the heat medium water input pipeline are respectively connected to the heat medium water inlet and the cold water outlet, and the heat medium water input pipeline is provided with a low-temperature economizer inlet valve;

[0010] The two ends of the heat medium water output pipeline are respectively connected to the heat medium water outlet and the hot water inlet; the heat medium water output pipeline is provided with a low-temperature economizer outlet valve, a heat medium water vapor heater inlet valve, a heat medium water vapor heater and a heat medium water vapor heater outlet valve in sequence;

[0011] A first bypass pipeline is also connected between the heat medium water input pipeline and the heat medium water output pipeline, and two ends of the first bypass pipeline are respectively connected to the inlet side of the low-temperature economizer inlet valve and the outlet side of the low-temperature economizer outlet valve; a low-temperature economizer bypass valve is provided on the first bypass pipeline;

[0012] The heat medium water output pipeline is also connected to a second bypass pipeline in parallel with the heat medium water vapor heater, and the two ends of the second bypass pipeline are respectively connected to the inlet side of the heat medium water vapor heater inlet valve and the outlet side of the heat medium water vapor heater outlet valve; the second bypass pipeline is provided with a heat medium water vapor heater bypass valve.

[0013] Furthermore, a heat medium water recirculation pump is provided on the heat medium water input pipeline.

[0014] Furthermore, the heat medium water recirculation pump is arranged at the inlet side of the low-temperature economizer inlet valve and the first bypass pipeline.

[0015] Furthermore, the steam inlet is connected to a steam pipeline for inputting heating steam into the heat medium water vapor heater.

[0016] Furthermore, the heat medium water vapor heater is provided with a steam inlet and a drain outlet. The steam inlet is connected to a steam pipeline for inputting heating steam into the heat medium water vapor heater; the drain outlet is connected to a drain pipeline for discharging condensed water after heat exchange cooling.

[0017] Furthermore, the flue gas inlet is connected to the flue gas pipeline at the air preheater outlet.

[0018] Furthermore, the low-temperature economizer inlet valve, the low-temperature economizer outlet valve, the heat medium water vapor heater inlet valve, the heat medium water vapor heater outlet valve, the low-temperature economizer bypass valve and the heat medium water vapor heater bypass valve are all electric valves.

[0019] Compared with the prior art, the utility model has the following technical effects:

[0020] The utility model discloses a closed flue gas waste heat utilization system. By adding a first bypass pipeline, a second bypass pipeline and a heat medium water vapor heater and other equipment on the circulation pipeline between the low-temperature economizer and the heat medium water heater, when the low-temperature economizer cannot operate, the heat medium water vapor heater can be used to heat the cold water, and the heated hot water can be used to heat the cold air entering the heat medium water heater, so that the temperature of the hot air coming out of the hot air interface of the air preheater meets the requirements for entering the air preheater, ensuring that the comprehensive temperature of the cold end of the air preheater is met, and can adapt to closed, all-weather, full-load working conditions, prevent the blockage of the air preheater, low-temperature corrosion and cross-boundary corrosion of ammonium bisulfate, and have obvious economic benefits.

[0021] The utility model provides a closed flue gas waste heat utilization system which can control the states of various devices and valves according to the specific situation and state of the unit, thereby ensuring the stable operation of the flue gas waste heat utilization system and improving the economic efficiency of the unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 A schematic diagram of the structure of an existing low-temperature economizer-closed heat medium water heater combined with flue gas waste heat utilization system provided as background technology;

[0024] Figure 2 A structural schematic diagram of a closed flue gas waste heat utilization system provided in an embodiment of the utility model.

[0025] Among them, the reference numerals in the figure are:

[0026] 1. Low-temperature economizer, 2. Heat medium water heater fan, 3. Heat medium water recirculation pump, 4. Low-temperature economizer inlet valve, 5. Low-temperature economizer outlet valve, 6. Low-temperature economizer bypass valve, 7. Heat medium water vapor heater outlet valve, 8. Heat medium water vapor heater inlet valve, 9. Heat medium water vapor heater bypass valve, 10. Heat medium water vapor heater, 100. Heat medium water input pipeline, 200. Heat medium water output pipeline, 300. First bypass pipeline, 400. Second bypass pipeline. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0029] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0030] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present invention, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0031] See also Figure 2 Now, a closed flue gas waste heat utilization system provided by an embodiment of the utility model is described.

[0032] In one embodiment, a closed flue gas waste heat utilization system of the utility model embodiment includes a low-temperature economizer 1 and a heat medium water heater 2, and the low-temperature economizer 1 and the heat medium water heater 2 are connected to form a circulation pipeline through a heat medium water input pipeline 100 and a heat medium water output pipeline 200; the low-temperature economizer 1 is provided with a flue gas inlet, a flue gas outlet, a heat medium water inlet and a heat medium water outlet; the heat medium water heater 2 is provided with a cold air inlet, an air preheater hot air interface, a hot water inlet and a cold water outlet; the two ends of the heat medium water input pipeline 100 are respectively connected to the heat medium water inlet and the cold water outlet, and the heat medium water input pipeline 100 is provided with a low-temperature economizer inlet valve 4; the two ends of the heat medium water output pipeline 200 are respectively connected to the heat medium water outlet and the hot water inlet; the heat medium water output pipeline 200 is provided with a low-temperature economizer outlet valve 4 in sequence. Door 5, heat medium water vapor heater inlet valve 8, heat medium water vapor heater 10 and heat medium water vapor heater outlet valve 7; a first bypass pipeline 300 is also connected between the heat medium water input pipeline 100 and the heat medium water output pipeline 200, and the two ends of the first bypass pipeline 300 are respectively connected to the inlet side of the low-temperature economizer inlet valve 4 and the outlet side of the low-temperature economizer outlet valve 5; a low-temperature economizer bypass valve 6 is provided on the first bypass pipeline 300; a second bypass pipeline 400 connected in parallel with the heat medium water vapor heater 10 is also connected to the heat medium water output pipeline 200, and the two ends of the second bypass pipeline 400 are respectively connected to the inlet side of the heat medium water vapor heater inlet valve 8 and the outlet side of the heat medium water vapor heater outlet valve 7; a heat medium water vapor heater bypass valve 9 is provided on the second bypass pipeline 400.

[0033] A closed flue gas waste heat utilization system of an embodiment of the utility model adds a first bypass pipeline 300, a second bypass pipeline 400 and a heat medium water vapor heater 10 and other equipment on the circulation pipeline between the low-temperature economizer 1 and the heat medium water heater 2. When the low-temperature economizer 1 cannot operate, the heat medium water vapor heater 10 can be used to heat the cold water, and the heated hot water can be used to heat the cold air entering the heat medium water heater 2, so that the temperature of the hot air coming out of the hot air interface of the air preheater meets the requirements for entering the air preheater, ensuring that the comprehensive temperature of the cold end of the air preheater is met, and can adapt to closed, all-weather, full-load conditions, prevent the air preheater from clogging, low-temperature corrosion and ammonium bisulfate cross-border corrosion, and the economic benefit is obvious.

[0034] Furthermore, a heat medium water recirculation pump 3 is provided on the heat medium water input pipeline 100 of this embodiment to provide circulation power for the circulating water.

[0035] Furthermore, the heat medium water recirculation pump 3 of this embodiment is arranged at the inlet side of the low-temperature economizer inlet valve 4 and the first bypass pipeline 300 .

[0036] Furthermore, the heat medium water vapor heater 10 of this embodiment is provided with a steam inlet and a drain outlet, and the steam inlet is connected to a steam pipeline for inputting heating steam into the heat medium water vapor heater 10. The drain outlet of the heat medium water vapor heater 10 is connected to a drainage pipeline for discharging condensed water after heat exchange cooling.

[0037] Furthermore, the flue gas inlet on the low-temperature economizer 1 of the present embodiment is connected to the flue gas pipeline at the air preheater outlet, and the flue gas at the air preheater outlet is used as the heating flue gas of the low-temperature economizer 1 .

[0038] Furthermore, the low-temperature economizer inlet valve 4, the low-temperature economizer outlet valve 5, the heat medium water vapor heater inlet valve 8, the heat medium water vapor heater outlet valve 7, the low-temperature economizer bypass valve 6 and the heat medium water vapor heater bypass valve 9 of this embodiment are all electric valves.

[0039] When a closed flue gas waste heat utilization system of this embodiment is in operation, it can be divided into two categories: normal operating conditions and abnormal accident operating conditions:

[0040] 1) Normal working conditions:

[0041] (1) When the outdoor calculated temperature for summer ventilation or the multi-year average temperature is used as the system ambient temperature and the unit is running at a load of 30% or less at startup, the outdoor calculated temperature for winter heating is used as the system ambient temperature and the unit is running at a load of 50% or less at startup, or the unit is in deep peak load regulation operation, the exhaust gas temperature of the air preheater is lower than 90°C, and the flue gas waste heat cannot be used to add cold air to the air preheater inlet, the system needs to close the low-temperature economizer inlet valve 4 and the low-temperature economizer outlet valve 5, open the low-temperature economizer bypass valve 6, cut off the low-temperature economizer 1, open the heat medium water vapor heater inlet valve 8 and the heat medium water vapor heater outlet valve 7, close the heat medium water vapor heater bypass valve 9, use the heat medium water vapor heater 10 and the heat medium water heater 2 to heat the cold air, and control the air preheater inlet cold air temperature to reach the design 40-100°C (typical preferred value 60°C). At the same time, monitor the air preheater flue gas side resistance so that the comprehensive temperature of the cold end of the air preheater meets the air preheater without low-temperature corrosion and ammonium bisulfate cross-boundary corrosion.

[0042] (2) When the outdoor calculated temperature for summer ventilation or the multi-year average temperature is used as the system ambient temperature and the unit operates at a load of 30% to 50% or above, and the outdoor calculated temperature for winter heating is used as the system ambient temperature and the unit operates at a load of 50% to 75%, the exhaust gas temperature of the air preheater is above 90°C, but the waste heat of the flue gas of the low-temperature economizer 1 is insufficient to heat the cold air at the inlet of the air preheater to the design temperature of 40 to 100°C (typically preferred value 60°C). The system needs to open the low-temperature economizer inlet valve 4 and the low-temperature economizer outlet valve 5, close the low-temperature economizer bypass valve 6, put the low-temperature economizer 1 into operation, keep the heat medium water vapor heater inlet valve 8 and the heat medium water vapor heater outlet valve 7 in the open state, and use the heat medium water vapor heater 10, the low-temperature economizer 1 and the heat medium water vapor heater 2 to heat the cold air to the design temperature of 40 to 100°C (typically preferred value 60°C) at the inlet of the air preheater. At the same time, the resistance on the flue gas side of the air preheater is monitored to ensure that the comprehensive temperature at the cold end of the air preheater satisfies the requirement that low-temperature corrosion and ammonium bisulfate cross-boundary corrosion will not occur in the air preheater.

[0043] (3) When the outdoor calculated temperature for summer ventilation or the multi-year average temperature is used as the system ambient temperature and the unit is running at 50% or more load, and the outdoor calculated temperature for winter heating is used as the system ambient temperature and the unit is running at 100% load, the exhaust gas temperature of the air preheater is above 90°C, and the flue gas waste heat of the low-temperature economizer 1 is sufficient to heat the air preheater inlet cold air to the design temperature of 40-100°C (typical preferred value 60°C). The low-temperature economizer inlet valve 4 and the low-temperature economizer outlet valve 5 are kept open, the heat medium water vapor heater inlet valve 8, the heat medium water vapor heater outlet valve 7 and the low-temperature economizer bypass valve 6 are closed, the heat medium water vapor heater bypass valve 9 is opened, and the heat medium water vapor heater 10 is shut down. At the same time, the air preheater flue gas side resistance is monitored to ensure that the comprehensive temperature at the cold end of the air preheater satisfies the air preheater and does not cause low-temperature corrosion and ammonium bisulfate cross-boundary corrosion.

[0044] 2) Abnormal accident conditions:

[0045] When the low-temperature economizer 1 cannot be put into operation due to wear and leakage, the system needs to close the low-temperature economizer inlet valve 4 and the low-temperature economizer outlet valve 5, open the low-temperature economizer bypass valve 6, cut off the low-temperature economizer 1, open the heat medium water vapor heater inlet valve 8 and the heat medium water vapor heater outlet valve 7, close the heat medium water vapor heater bypass valve 9, and only use the heat medium water vapor heater 10 and the heat medium water heater 2 to heat the cold air to the air preheater cold air to the design temperature of 40-100°C (typical preferred value 60°C), and monitor the air preheater flue gas side resistance at the same time, so that the comprehensive temperature of the cold end of the air preheater meets the air preheater without low-temperature corrosion and ammonium bisulfate cross-boundary corrosion.

[0046] A closed flue gas waste heat utilization system of this embodiment can cut off the low-temperature economizer 1 when the load is low or the low-temperature economizer 1 is worn, corroded or leaked, making it impossible to put the low-temperature economizer 1 into operation. The heat medium water vapor heater 10 can be used to heat the cold air to ensure a reasonable air temperature at the air preheater inlet.

[0047] A closed flue gas waste heat utilization system in this embodiment can adapt to closed, all-weather, full-load conditions by controlling the status of various devices and valves according to the specific conditions and status of the unit, and prevent problems such as air preheater blockage, low-temperature corrosion, and ammonium bisulfate cross-boundary corrosion, with obvious economic benefits.

[0048] A closed flue gas waste heat utilization system in this embodiment is suitable for the flue gas waste heat utilization system of supercritical or ultra-supercritical, single reheat or double reheat coal-fired thermal power plants. While ensuring that the flue gas waste heat utilization system can adapt to various working conditions and operate stably, it can also improve the economy of unit operation.

[0049] The above embodiments only express several implementation methods of the utility model, and the descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A closed flue gas waste heat utilization system, characterized in that: It includes a low-temperature economizer and a heat medium water heater, wherein the low-temperature economizer and the heat medium water heater are connected to form a circulation pipeline through a heat medium water input pipeline and a heat medium water output pipeline; The low-temperature economizer is provided with a flue gas inlet, a flue gas outlet, a heat medium water inlet and a heat medium water outlet; The heat medium water heater is provided with a cold air inlet, an air preheater hot air interface, a hot water inlet and a cold water outlet; The two ends of the heat medium water input pipeline are respectively connected to the heat medium water inlet and the cold water outlet, and the heat medium water input pipeline is provided with a low-temperature economizer inlet valve; The two ends of the heat medium water output pipeline are respectively connected to the heat medium water outlet and the hot water inlet; the heat medium water output pipeline is provided with a low-temperature economizer outlet valve, a heat medium water vapor heater inlet valve, a heat medium water vapor heater and a heat medium water vapor heater outlet valve in sequence; A first bypass pipeline is also connected between the heat medium water input pipeline and the heat medium water output pipeline, and two ends of the first bypass pipeline are respectively connected to the inlet side of the low-temperature economizer inlet valve and the outlet side of the low-temperature economizer outlet valve; a low-temperature economizer bypass valve is provided on the first bypass pipeline; The heat medium water output pipeline is also connected to a second bypass pipeline in parallel with the heat medium water vapor heater, and the two ends of the second bypass pipeline are respectively connected to the inlet side of the heat medium water vapor heater inlet valve and the outlet side of the heat medium water vapor heater outlet valve; the second bypass pipeline is provided with a heat medium water vapor heater bypass valve.

2. A closed flue gas waste heat utilization system as claimed in claim 1, characterized in that: The heat medium water input pipeline is provided with a heat medium water recirculation pump.

3. A closed flue gas waste heat utilization system as claimed in claim 2, characterized in that: The heat medium water recirculation pump is arranged at the inlet side of the low-temperature economizer inlet valve and the first bypass pipeline.

4. A closed flue gas waste heat utilization system as claimed in claim 1, characterized in that: The steam inlet is connected to a steam pipeline for inputting heating steam into the heat medium water vapor heater.

5. A closed flue gas waste heat utilization system as claimed in claim 1, characterized in that: The heat medium water vapor heater is provided with a steam inlet and a drain outlet. The steam inlet is connected to a steam pipeline for inputting heating steam into the heat medium water vapor heater; the drain outlet is connected to a drain pipeline for discharging condensed water after heat exchange cooling.

6. A closed flue gas waste heat utilization system as claimed in claim 1, characterized in that: The flue gas inlet is connected to the air preheater outlet flue gas pipeline.

7. A closed flue gas waste heat utilization system according to any one of claims 1 to 6, characterized in that: The low-temperature economizer inlet valve, the low-temperature economizer outlet valve, the heat medium water vapor heater inlet valve, the heat medium water vapor heater outlet valve, the low-temperature economizer bypass valve and the heat medium water vapor heater bypass valve are all electric valves.

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