Closed recovery system for low-pressure steam condensed water

Abstract

A closed recovery system for low-pressure steam condensed water comprises a steam condensate pipe, a low-pressure flash tank, a normal-pressure flash tank, a cooler, a condensed water nipple, an ejector and a condensed water pump. The steam condensate pipe is communicated with an inlet of the low-pressure flash tank, a first outlet of the low-pressure flash tank is communicated with an inlet of the low-pressure steam pipe network, a second outlet of the low-pressure flash tank is communicated with an inlet of the normal-pressure flash tank through a liquid discharging pipe of the low-pressure flash tank, and a first outlet of the normal-pressure flash tank is communicated with the cooler. A second outlet of the normal-pressure flash tank is communicated with a first inlet of the ejector through a normal-pressure flash tank liquid discharging pipe, the ejector is communicated with the condensate pump through an ejector outlet pipe, the condensate pump is communicated with a second inlet of the ejector through a backflow pipe, and an outlet of the cooler is communicated with the condensate nipple through a cooler liquid outlet pipe. A first outlet of the condensed water short section is communicated with the condensed water short section exhaust pipe, and a third outlet of the condensed water short section is communicated with a reflux inlet of the normal-pressure flash tank through a condensed water short section liquid outlet pipe.

Description

Technical Field

[0001] This utility model relates to a closed-loop recovery system for low-pressure steam condensate, belonging to the field of low-pressure steam condensate recovery technology. Background Technology

[0002] With the rapid development of industrialization and the increasing scarcity of resources, the energy and environmental crisis has become a global problem that urgently needs to be solved. In particular, in industrial sites such as coal chemical industry, a large amount of low-pressure steam is used for heating steam reboilers and pipeline heat tracing, resulting in a continuous increase in the amount of low-pressure steam condensate produced.

[0003] Currently, there are two common methods for low-pressure steam condensate recovery in China: one is an open-loop condensate recovery system, where the flashed secondary steam is completely discharged into the atmosphere through a vertical pipe, wasting a large amount of water and polluting the environment. The other is a closed-loop condensate recovery system, where high-temperature condensate enters a flash tank. Although the flash tank is equipped with cooling facilities, a small amount of steam still cannot be discharged due to the coexistence of vapor and liquid in the tank. The condensate with a small amount of steam easily vaporizes at the pump inlet, causing pump cavitation. In addition, a large amount of air enters the condensate system through the condensate venting pipeline, and some gas dissolves into the condensate during transportation, causing corrosion to the transportation pipelines and heat exchange equipment.

[0004] For example, utility model CN206974219U provides an integrated steam condensate recovery system, including a steam condensate pipe, a vertical steam condensate tank, a steam condensate pump, and a condensate pump outlet tank. Because steam condensate dissolves certain gases, flash vapor in the condensate overflows during the condensate pump's transport process, causing water hammer and pump cavitation in the pipeline, affecting the long-term stable operation of the equipment.

[0005] Therefore, designing a closed-loop steam condensate recovery system is an important measure for energy conservation and emission reduction, and it plays a positive role in effectively preventing steam condensate corrosion, protecting the environment, and making rational use of water resources. Utility Model Content

[0006] The technical problem to be solved by this utility model is to provide a low-pressure steam condensate closed-loop recovery system to address the shortcomings of the existing technology. This system effectively eliminates the problem of direct steam discharge, avoids environmental pollution, reduces steam waste, and enables water recycling. It also solves the problems of pump cavitation and corrosion of equipment and pipelines, and reduces the occurrence of water hammer during condensate transportation.

[0007] The technical problem to be solved by this utility model is achieved through the following technical solution:

[0008] This utility model provides a closed-loop recovery system for low-pressure steam condensate, including a steam condensate pipe, a low-pressure flash tank, an atmospheric flash tank, a cooler, and a condensate short section. The closed-loop recovery system also includes an ejector and a condensate pump. The steam condensate pipe is connected to the inlet of the low-pressure flash tank, the first outlet of the low-pressure flash tank is connected to the inlet of the low-pressure steam network, and the second outlet of the low-pressure flash tank is connected to the inlet of the atmospheric flash tank via a low-pressure flash tank drain pipe. The first outlet of the atmospheric flash tank is connected to the... The cooler is connected, the second outlet of the atmospheric flash tank is connected to the first inlet of the ejector through the atmospheric flash tank drain pipe, the ejector is connected to the condensate pump through the ejector outlet pipe, the condensate pump is connected to the second inlet of the ejector through the return pipe, the outlet of the cooler is connected to the condensate stub through the cooler outlet pipe, the first outlet of the condensate stub is connected to the condensate stub exhaust pipe, and the third outlet of the condensate stub is connected to the return port of the atmospheric flash tank through the condensate stub outlet pipe.

[0009] To prevent system overpressure, the third outlet of the low-pressure flash tank is connected to the exhaust pipe of the low-pressure flash tank, and the exhaust pipe of the low-pressure flash tank is equipped with a safety valve assembly.

[0010] Preferably, the cooler is a water cooler or an air cooler.

[0011] In order to monitor the liquid levels in the low-pressure flash tank and the atmospheric flash tank locally or remotely, the low-pressure flash tank is equipped with a local liquid level gauge and a remote liquid level gauge, and the atmospheric flash tank is equipped with a local liquid level gauge and a remote liquid level gauge.

[0012] In order to control the flow rate and velocity of the fluid flowing through the drain pipe of the low-pressure flash tank, a first regulating valve is installed at the drain pipe of the low-pressure flash tank; in order to control the flow rate and velocity of the fluid flowing through the return pipe, a third regulating valve is installed at the return pipe.

[0013] In order to control the flow rate and velocity of the fluid flowing through the outlet pipe of the condensate pump, the condensate pump is connected to the outside through the outlet pipe of the condensate pump, and a second regulating valve is provided at the outlet pipe of the condensate pump.

[0014] To prevent air from coming into direct contact with condensate, the second outlet of the condensate section is connected to a low-pressure nitrogen pipeline.

[0015] In order to separate the trace flash vapor contained in the condensate into gas and liquid in the condensate section, the first outlet and the second outlet of the condensate section are located at the top of the condensate section, and the third outlet of the condensate section is located at the bottom of the condensate section.

[0016] To overcome the pressure drop of the cooler and the pressure drop of the cooler inlet pipeline, the bottom of the condensate stub is 4-10 meters higher than the top of the atmospheric pressure flash tank.

[0017] In summary, this invention effectively eliminates the problem of direct steam discharge, avoids environmental pollution, reduces steam waste, enables water recycling, and solves the problems of pump cavitation and corrosion of equipment and pipelines, thereby reducing the occurrence of water hammer during condensate transportation.

[0018] The technical solution of this utility model will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the low-pressure steam condensate closed-loop recovery system of this utility model;

[0020] Figure 2 This is a schematic diagram of another low-pressure steam condensate closed-loop recovery system of this utility model.

[0021] [Explanation of Labels in the Attached Image]

[0022] 1-Steam condensate pipe, 2-Low-pressure flash tank, 3-Atmospheric flash tank, 4-Water cooler, 5-Ejector, 6-Condensate pump, 7-Condensate stub, 8-Low-pressure steam network, 9-Low-pressure flash tank drain pipe, 10-First regulating valve, 11-Low-pressure flash tank vent pipe, 12-Cooler outlet pipe, 13-Condensate stub vent pipe, 14-Low-pressure nitrogen pipeline, 15-Condensate stub outlet Pipes: 16-Atmospheric flash tank drain pipe, 17-Return pipe, 18-Ejector outlet pipe, 19-Condensate pump outlet pipe, 20-Second regulating valve, 21-Air cooler, 22-Low-pressure flash tank local level gauge, 23-Low-pressure flash tank remote level gauge, 24-Atmospheric flash tank local level gauge, 25-Atmospheric flash tank remote level gauge, 26-Third regulating valve, 27-Atmospheric flash tank exhaust pipe. Detailed Implementation

[0023] Figure 1 This is a schematic diagram of the structure of the low-pressure steam condensate closed-loop recovery system of this utility model; Figure 2 This is a schematic diagram of another low-pressure steam condensate closed-loop recovery system according to this utility model. Figure 1 and Figure 2 As shown, this utility model provides a closed-loop recovery system for low-pressure steam condensate, which includes a steam condensate pipe 1, a low-pressure flash tank 2, an atmospheric pressure flash tank 3, a cooler, an ejector 5, a condensate pump 6, and a condensate stub 7.

[0024] The low-pressure flash tank 2 has one inlet and three outlets. The steam condensate pipe 1 is connected to the inlet of the low-pressure flash tank 2; the first outlet of the low-pressure flash tank 2 is connected to the inlet of the low-pressure steam network 8; the second outlet of the low-pressure flash tank 2 is connected to the inlet of the atmospheric pressure flash tank 3 via the low-pressure flash tank drain pipe 9; and the third outlet of the low-pressure flash tank 2 is connected to the low-pressure flash tank exhaust pipe 11.

[0025] The steam condensate enters the inlet of the low-pressure flash tank 2 through the steam condensate pipe 1. The pressure range inside the low-pressure flash tank 2 is preferably 0-0.6 MPaG.

[0026] The low-pressure steam generated by the flash evaporator 2 enters the inlet of the low-pressure steam pipeline 8 through the first outlet.

[0027] To control the flow rate and velocity of the fluid passing through the drain pipe 9 of the low-pressure flash tank, a first regulating valve 10 is installed at the drain pipe 9 of the low-pressure flash tank. The liquid phase of the low-pressure flash tank 2 enters the inlet of the atmospheric pressure flash tank 3 after passing through the first regulating valve 10 of the drain pipe 9 at the second outlet of the low-pressure flash tank 2.

[0028] To prevent system overpressure, the low-pressure flash tank exhaust pipe 11 is equipped with a safety valve group 26, and the outlet of the safety valve group 26 is connected to the atmosphere through a pipe.

[0029] In addition to the inlet connected to the drain pipe 9 of the low-pressure flash tank, the atmospheric flash tank 3 is also provided with two outlets and a return port. The first outlet of the atmospheric flash tank 3 is connected to the cooler (preferably, as shown in the figure, the two are connected through the atmospheric flash tank exhaust pipe 27), and the second outlet of the atmospheric flash tank 3 is connected to the first inlet of the ejector 5 through the atmospheric flash tank drain pipe 16.

[0030] The ejector 5 is connected to the condensate pump 6 via the ejector outlet pipe 18. The condensate pump 6 is connected to the outside (e.g., outside the boundary area) via the condensate pump outlet pipe 19. The condensate pump 6 is connected to the second inlet of the ejector 5 via the return pipe 17. In other words, the ejector 5 and the condensate pump 6 are connected in series.

[0031] In order to control the flow rate and velocity of the fluid flowing through the condensate pump outlet pipe 19 and the return pipe 17 respectively, a second regulating valve 20 is provided at the condensate pump outlet pipe 19 and a third regulating valve 26 is provided at the return pipe 17.

[0032] The liquid phase in the atmospheric flash tank 3 enters the first inlet of the ejector 5 through the second outlet of the atmospheric flash tank drain pipe 16, and then enters the condensate pump 6 through the ejector outlet pipe 18. The condensate at the pump outlet of the condensate pump 6 is partially returned to the ejector 5 through the return pipe 17, and the other part flows out of the boundary area after passing through the second regulating valve 20.

[0033] Condensate flowing outside the boundary area can be further treated through the plant-wide condensate refining system, and then sent to the boiler as boiler feedwater to generate steam.

[0034] This invention improves pressure by combining an ejector and a condensate pump at the outlet of an atmospheric pressure flash tank, effectively solving the problems of pump cavitation caused by the overflow of trace flash vapor in the water and water hammer during condensate transportation.

[0035] Specifically, when the liquid in the atmospheric flash tank 3 passes through the nozzle of the ejector 5, the cross-sectional area suddenly decreases, and the flow velocity increases significantly, forming a high-speed jet flow. This creates a low-pressure zone at the nozzle, drawing in the liquid phase from the atmospheric flash tank 3. The incoming liquid collides and mixes with the high-speed water flow. After the mixed fluid enters the diffuser of the ejector 5, the pipe gradually widens, the flow velocity slows down, and kinetic energy is converted into static pressure energy. This increases the fluid pressure output from the outlet of the ejector 5, thereby increasing the pump's effective net positive suction head (NPSHA), improving cavitation resistance, increasing the pump inlet pressure, reducing liquid vaporization, and making water hammer less likely to occur.

[0036] This invention does not limit the type of cooler; it can be a water cooler or an air cooler. Figure 1 In the example shown, the cooler is water cooler 4. Figure 2 In the example shown, the cooler is an air cooler 21.

[0037] To monitor the liquid levels in the low-pressure flash tank 2 and the atmospheric pressure flash tank 3 locally or remotely, both are equipped with local and remote level gauges. For example, the low-pressure flash tank 2 is equipped with a local level gauge 22 and a remote level gauge 23, while the atmospheric pressure flash tank 3 is equipped with a local level gauge 24 and a remote level gauge 25.

[0038] The cooler outlet is connected to the condensate stub 7 via the cooler outlet pipe 12. The first outlet of the condensate stub 7 is connected to the condensate stub exhaust pipe 13. The second outlet of the condensate stub 7 is connected to the low-pressure nitrogen line 14. The third outlet of the condensate stub 7 is connected to the reflux port of the atmospheric flash tank 3 via the condensate stub outlet pipe 15. The reflux port of the atmospheric flash tank 3 is located at the bottom of the atmospheric flash tank 3. The low-pressure nitrogen line 14 is, for example, a 0-1.6 MPaG nitrogen line.

[0039] The gas flashed out of the atmospheric flash tank 3 enters the cooler through the atmospheric flash tank exhaust pipe 27 at the first outlet of the atmospheric flash tank 3. The condensate at the cooler outlet enters the condensate section 7 through the cooler outlet pipe 12, and then enters the return port of the atmospheric flash tank 3 through the condensate section outlet pipe 15 at the third outlet of the condensate section 7.

[0040] In order to separate the trace flash vapor contained in the condensate into gas and liquid in the condensate section 7, the first and second outlets of the condensate section 7 are located at the top of the condensate section 7, and the third outlet of the condensate section 7 is located at the bottom of the condensate section 7.

[0041] In order to overcome the pressure drop of the cooler and the pressure drop of the cooler inlet pipeline (i.e., the exhaust pipe 27 of the atmospheric flash tank), a certain static liquid column height is required between the cooler outlet and the atmospheric flash tank 3. Therefore, the bottom of the condensate short section 7 is 4-10 meters higher than the top of the atmospheric flash tank 3.

[0042] During normal production, a small amount of nitrogen is introduced into the low-pressure nitrogen pipeline 14 to prevent air from directly contacting the condensate. This ensures the cleanliness of the condensate, saves on secondary treatment costs, and prevents corrosion of the pipeline and heat exchange equipment by dissolved gases during condensate transportation, thus extending the service life of the equipment and pipelines.

[0043] Based on actual operating experience, by adopting the above-mentioned low-pressure steam condensate closed-loop recovery system, the service life of condensate carbon steel pipelines and condensate pumps will be extended by 5-10 years. According to calculations, 15t / h of 1.0MPaG condensate can recover 2.38t / h of steam through this low-pressure steam condensate closed-loop recovery system. Based on a steam price of RMB 110 / ton and 8000 hours of operation per year, the annual cost savings will be approximately RMB 2.094 million.

[0044] In summary, this invention effectively eliminates the problem of direct steam discharge, avoids environmental pollution, reduces steam waste, enables water recycling, and solves the problems of pump cavitation and corrosion of equipment and pipelines, thereby reducing the occurrence of water hammer during condensate transportation.

Claims

1. A low pressure steam condensate closed recovery system comprising a steam condensate pipe, a low pressure flash tank, an atmospheric flash tank, a cooler, and a condensate spool, characterized by, The low-pressure steam condensate closed-loop recovery system also includes an ejector and a condensate pump; the steam condensate pipe is connected to the inlet of the low-pressure flash tank, the first outlet of the low-pressure flash tank is connected to the inlet of the low-pressure steam network, the second outlet of the low-pressure flash tank is connected to the inlet of the atmospheric pressure flash tank through the low-pressure flash tank drain pipe, the first outlet of the atmospheric pressure flash tank is connected to the cooler, the second outlet of the atmospheric pressure flash tank is connected to the first inlet of the ejector through the atmospheric pressure flash tank drain pipe, the ejector is connected to the condensate pump through the ejector outlet pipe, the condensate pump is connected to the second inlet of the ejector through the return pipe, the outlet of the cooler is connected to the condensate stub through the cooler outlet pipe, the first outlet of the condensate stub is connected to the condensate stub exhaust pipe, and the third outlet of the condensate stub is connected to the return port of the atmospheric pressure flash tank through the condensate stub outlet pipe.

2. The low pressure steam condensate closed loop recovery system of claim 1 wherein, The third outlet of the low-pressure flash tank is connected to the exhaust pipe of the low-pressure flash tank, and the exhaust pipe of the low-pressure flash tank is equipped with a safety valve assembly.

3. The low pressure steam condensate closed loop recovery system of claim 1 wherein, The cooler is either a water cooler or an air cooler.

4. The low pressure steam condensate closed loop recovery system of claim 1 wherein, The low-pressure flash tank is equipped with a local level gauge and a remote level gauge, while the atmospheric pressure flash tank is equipped with a local level gauge and a remote level gauge.

5. The low pressure steam condensate closed loop recovery system of claim 1 wherein, A first regulating valve is installed at the drain pipe of the low-pressure flash tank, and a third regulating valve is installed at the return pipe.

6. The low pressure steam condensate closed loop recovery system of claim 1 wherein, The condensate pump is connected to the outside through the condensate pump outlet pipe, and a second regulating valve is installed at the condensate pump outlet pipe.

7. The low pressure steam condensate closed loop recovery system of claim 1 wherein, The second outlet of the condensate short section is connected to the low-pressure nitrogen pipeline.

8. The low pressure steam condensate closed loop recovery system of claim 7 wherein, The first outlet and the second outlet of the condensate section are located at the top of the condensate section, and the third outlet of the condensate section is located at the bottom of the condensate section.

9. The low pressure steam condensate closed loop recovery system of claim 1 wherein, The bottom of the condensate stub is 4-10 meters higher than the top of the atmospheric pressure flash tank.

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