A natural gas heating system based on waste heat utilization of a blowdown flash tank

Abstract

The utility model provides a kind of natural gas heating system based on waste heat utilization of pollution expansion vessel, it is related to gas steam combined cycle power plant design technical field.The system includes continuous pollution expansion vessel, periodic pollution expansion vessel, continuous pollution water pipeline, pollution water bypass system, booster pump, natural gas pipeline, natural gas heater and natural gas leak detection device.Pollution water is guided to natural gas heater by pollution water bypass pipeline, and pollution water is discharged to periodic pollution expansion vessel after releasing heat and cooling down;natural gas comes from outside pressure regulating station, and temperature is promoted after being absorbed the heat released by pollution water by natural gas heater, then enters subsequent gas front-end module.The system can effectively recover the heat loss of gas steam combined cycle unit waste heat boiler pollution, reduce the energy consumption of in-plant cooling tower, improve the overall plant thermal efficiency, while avoiding natural gas dewing due to too low temperature, meet the unit operation demand.

Description

Technical Field

[0001] This utility model relates to the field of gas-fired steam combined cycle power plant design technology, and in particular to a natural gas heating system based on the utilization of waste heat from a blowdown expansion tank. Background Technology

[0002] Gas turbines are a symbol of a country's industrial level and technological capabilities. Developing the gas turbine industry and technology is of great strategic significance for promoting the adjustment and transformation of the national industrial structure and improving the quality and efficiency of economic development.

[0003] For gas turbine combined cycle units using natural gas, the temperature drop from the upstream natural gas pipeline and the temperature drop after pressure regulation due to the Joule-Thompson effect necessitate certain standards for the inlet natural gas temperature. These standards are typically around 200°C, and are influenced by factors such as temperature drops in the upstream natural gas pipeline and the Joule-Thompson effect. To prevent condensation and damage to the gas turbine due to excessively low natural gas temperature, or to meet the ignition requirements of the gas turbine during startup, the inlet natural gas temperature must meet certain standards. For example, a GE 9HA.02 gas turbine requires an inlet natural gas temperature of 227°C, while a Mitsubishi M701J gas turbine requires an inlet natural gas temperature of 215°C. Therefore, natural gas pipeline systems usually require the installation of natural gas heating units.

[0004] Natural gas heating units can be divided into preheating units and performance heating units according to their functions.

[0005] Common preheating units include water bath heaters and electric heaters. Water bath heaters are systems that heat water by burning natural gas, and then the hot water heats the natural gas. This system is relatively complex and requires a natural gas pressurization unit to meet the needs of the water bath. If the natural gas temperature is too low, an electric heater is also needed to raise the natural gas temperature to the temperature required to ignite the water bath and stabilize combustion. This method consumes additional natural gas resources, increasing overall plant energy consumption and making it less economical. Electric heater systems, while simple, have a fast thermal response, and high temperature control accuracy, and can heat natural gas to extremely high temperatures, require explosion-proof designs and are more expensive, so they are rarely used as natural gas heaters.

[0006] The heating source for the performance heating unit is generally hot water from the outlet of the medium-pressure economizer of the waste heat boiler. After heating the natural gas, the hot water returns to the inlet of the low-pressure economizer or the condenser. However, the hot water from the outlet of the medium-pressure economizer of the waste heat boiler has a high energy quality, and excessive consumption will affect the output of waste heat power generation and reduce the overall plant thermal efficiency.

[0007] To minimize the disadvantages of the preheating and performance heating units, the recovery of waste heat from the power plant for natural gas heating is considered. Conventional gas-fired combined cycle turbine units are equipped with continuous blowdown expansion tanks and periodic blowdown expansion tanks. After recovering some steam in the continuous blowdown expansion tank, the remaining saturated water enters the periodic blowdown expansion tank. The steam in the periodic blowdown expansion tank is directly discharged into the atmosphere, and the wastewater flows to a cooling pool before entering the plant's circulating cooling water system, where it is further cooled by a cooling tower. This thermal system not only fails to recover the heat from the blowdown water in the expansion tanks but also requires additional electricity to drive the cooling towers and circulating cooling water system to cool the blowdown water, resulting in energy waste.

[0008] Therefore, it is necessary to design a natural gas heating system based on the utilization of waste heat from power plant wastewater expansion tanks in order to recover waste heat from power plants and save energy. Utility Model Content

[0009] To address the aforementioned issues, this utility model aims to propose a natural gas heating system based on the utilization of waste heat from a sewage expansion container. By forming a drainage bypass for the sewage expansion container through a "natural gas heater + inlet / outlet water pipes," it directly achieves "recovery of waste heat from sewage hot water to heat natural gas," thus solving the problem of waste heat waste and meeting the natural gas heating requirements.

[0010] To achieve the above objectives, the technical solution of this utility model is implemented as follows: A natural gas heating system based on waste heat utilization from a sewage expansion container includes a natural gas heater. One end of the natural gas heater is connected to a natural gas inlet pipe, and the other end is connected to a natural gas outlet pipe. The natural gas heater is also connected to a water inlet pipe and a water outlet pipe. The natural gas heater, the water inlet pipe, and the water outlet pipe constitute a bypass system for the drainage pipeline from the continuous sewage expansion container to the periodic sewage expansion container. This system is used to recover the heat from the sewage hot water discharged from the continuous sewage expansion container and transfer the heat to the natural gas to increase its temperature.

[0011] Furthermore, a first shut-off valve and a second shut-off valve are respectively provided before and after the natural gas heater, and a natural gas heater bypass pipe and a third shut-off valve are also provided.

[0012] Furthermore, a drain shut-off valve is installed in the drainage pipe.

[0013] Furthermore, the water inlet pipe contains two branches, namely the first branch and the second branch, which can switch between operation; the first branch is equipped with a fourth shut-off valve; the second branch is equipped with a booster pump, with a first isolation valve and a filter screen before the booster pump, and a check valve and a second isolation valve after the booster pump.

[0014] Furthermore, the outlet pipe is equipped with a natural gas leak detection device and a third isolation valve for monitoring natural gas leaks to the water side.

[0015] Furthermore, the end of the periodic sewage discharge expansion container is connected to a cooling pool that discharges into the plant's circulating cooling water system.

[0016] Furthermore, the end of the natural gas outlet pipe is connected to the gas turbine fuel pre-loading module.

[0017] Beneficial effects: This utility model forms a drainage bypass for the sewage expansion container by using a "natural gas heater + inlet / outlet water pipe", which directly realizes "recovering waste heat from sewage hot water to heat natural gas", thus solving the problem of waste heat waste and meeting the natural gas heating requirements. Attached Figure Description

[0018] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings: Figure 1 This is a schematic diagram of the natural gas heating system based on the waste heat utilization of the sewage expansion container, as described in an embodiment of this utility model. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] Example 1 See Figure 1 A natural gas heating system based on the utilization of waste heat from a sewage expansion container includes a natural gas heater 4. One end of the natural gas heater 4 is connected to a natural gas inlet pipe 9, and the other end is connected to a natural gas outlet pipe 10. The natural gas heater 4 is also connected to a water inlet pipe 6 and a water outlet pipe 7. The natural gas heater 4, the water inlet pipe 6, and the water outlet pipe 7 constitute a bypass system for the drainage pipe 5 from the continuous sewage expansion container 1 to the periodic sewage expansion container 2. This system is used to recover the heat from the sewage hot water discharged from the continuous sewage expansion container 1 and transfer the heat to the natural gas to increase the natural gas temperature.

[0022] This embodiment uses a natural gas heater and inlet / outlet water pipes to form a drainage bypass for the sewage expansion container, which directly realizes the "recovery of waste heat from sewage hot water to heat natural gas". This solves the problem of waste heat waste and meets the natural gas heating requirements.

[0023] In a specific example, a first shut-off valve 91 and a second shut-off valve 101 are respectively provided before and after the natural gas heater 4, and a natural gas heater bypass pipe 11 and a third shut-off valve 111 are also provided.

[0024] This embodiment achieves flexible commissioning / shutdown switching of the natural gas heater by setting up a shut-off valve and a bypass pipe. When the heater fails, the bypass can ensure uninterrupted natural gas supply, improving system reliability and maintenance convenience. At the same time, the shut-off valve can achieve safe isolation and reduce maintenance risks.

[0025] In one specific example, a drain shut-off valve 51 is provided in the drain pipe 5.

[0026] The drain shut-off valve in this embodiment can control the opening and closing of the original drain pipe, ensuring that all hot water enters the heater (instead of being directly discharged) during waste heat recovery, thereby improving the waste heat utilization rate; when the system is not in operation, it can restore the original drainage path, ensuring the normal operation of the sewage system and achieving seamless switching between the "waste heat recovery" and "conventional sewage" modes.

[0027] In a specific example, the water inlet pipe 6 has two branches, namely the first branch 61 and the second branch 62, which switch between operation; the first branch 61 is equipped with a fourth shut-off valve 63; the second branch 62 is equipped with a booster pump 8, with a first isolation valve 81 and a filter screen 82 before the booster pump 8, and a check valve 83 and a second isolation valve 84 after the booster pump 8.

[0028] The dual-branch design of this embodiment adapts to different operating conditions: when the pressure is sufficient, the straight-through branch is used (energy saving); when the pressure is insufficient, the booster pump branch is activated (to ensure flow), improving the system's adaptability to different sewage discharge pressures. Meanwhile, accessories such as filters and check valves protect the equipment (preventing impurities from entering and avoiding water backflow), extending the system's lifespan.

[0029] In a specific example, the water outlet pipe 7 is equipped with a natural gas leak detection device 71 and a third isolation valve 72 for monitoring natural gas leaks to the water side.

[0030] The natural gas leak detection device in this embodiment can monitor in real time whether natural gas has been mixed into the water side. Once a leak occurs, it can be quickly shut off by an isolation valve to prevent natural gas leaks from causing safety accidents (such as explosions or poisoning), significantly improving system safety and meeting the explosion-proof requirements for gas equipment.

[0031] In a specific example, the end of the periodic sewage discharge expansion container 2 is connected to the cooling pool 3, which discharges into the plant's circulating cooling water system.

[0032] This embodiment clearly defines the final destination of the wastewater hot water, ensuring that the waste heat can still be discharged in compliance with regulations through the original cooling pool and circulating water system after utilization, avoiding the impact of waste heat recovery modification on the environmental protection and stability of the wastewater system, and ensuring the overall closed-loop process of the system.

[0033] In one specific example, the natural gas outlet pipe 10 is connected at its end to a gas turbine fuel pre-loading module.

[0034] This embodiment clarifies the application endpoint of the heated natural gas, directly connecting it to the gas turbine fuel system to ensure that the heated natural gas can meet the gas turbine's inlet temperature requirements (such as preventing condensation and ensuring combustion efficiency), thus enhancing the compatibility between the system and the main unit.

[0035] In the specific implementation: like Figure 1 As shown, when the natural gas heating system is put into operation, the hot wastewater discharged from the continuous blowdown expansion tank 1 enters the natural gas heater 4 through the water pipe 6. The drainage pipe 5 is bypassed and not flowing (the drainage shut-off valve 51 is closed). After releasing heat, the hot wastewater is discharged to the periodic blowdown expansion tank 2 through the outlet pipe 7. The water pipe 6 has a first branch 61 and a second branch 62. Since the drainage from the continuous blowdown expansion tank 1 is pressurized, the hot wastewater first reaches the natural gas heater 4 through the first branch 61 (the fourth shut-off valve 63 and the third isolation valve 72 are open, the first isolation valve 81 and the second isolation valve 84 are closed, and the booster pump 8 is not running). After the hot wastewater releases heat and cools down in the natural gas heater 4, it is discharged to the periodic blowdown expansion tank 2 through the outlet pipe 7, and then discharged into the cooling pool 3. like Figure 1 As shown, when the natural gas heating system is put into operation, if the drainage pressure of the continuous sewage expansion container 1 is low and the hot sewage cannot reach the natural gas heater 4 and be discharged into the periodic sewage expansion container 2 by its own pressure, the hot sewage will switch to the water pipe 62 (the fourth shut-off valve 63 is closed, the third isolation valve 72, the first isolation valve 81 and the second isolation valve 84 are open, and the booster pump 8 is put into operation). The hot sewage will be pressurized by the booster pump 8 configured in the second branch 62 and reach the natural gas heater 4. After the hot sewage releases heat and cools down in the natural gas heater 4, it will be discharged into the periodic sewage expansion container 2 through the water outlet pipe 7, and then discharged into the cooling pool 3. like Figure 1 As shown, when the natural gas heating system is put into operation, shut-off valves 91 and 101 are opened and shut-off valve 111 is closed. After the natural gas outside the plant is processed by the pressure regulating station, it is introduced into the natural gas heater 4 through the natural gas inlet pipe 9 for heat absorption and temperature rise. The natural gas after heat absorption and temperature rise enters the subsequent gas pre-processing module through the natural gas outlet pipe 10. like Figure 1 As shown, when the natural gas heating system cannot be put into operation, the drain shut-off valve 51 is opened, and all valves in the water pipe 6 and the outlet pipe 7 are closed. The hot wastewater discharged from the continuous sewage expansion tank 1 is directly discharged through the drain pipe 5 to the periodic sewage expansion tank 2, and then discharged into the cooling pool 3 before being discharged into the plant's circulating cooling water system. At this time, the first shut-off valve 91 and the second shut-off valve 101 are closed simultaneously, and the third shut-off valve 111 is opened. The natural gas from the external pressure regulating station is switched to the natural gas heater bypass pipe 11 and enters the subsequent gas pre-processing module.

[0036] like Figure 1As shown, a natural gas leak detection device 71 is installed in the water outlet pipe 7 to monitor natural gas leaks to the water side. When natural gas leaks to the water side from the natural gas heater 4, the natural gas heater 4 is shut down in an emergency, and the system operates in the mode when the upper natural gas heating system cannot be put into operation.

[0037] This system reduces waste heat emissions from the power plant and lowers system energy consumption, thereby improving the overall energy utilization rate of the plant and helping to reduce carbon emissions.

[0038] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

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