Sewage treatment system and method using steam turbine exhaust steam waste heat

Abstract

The present application relates to steam turbine exhaust steam waste heat utilization and sewage treatment technical field, provide a kind of sewage treatment system and method using steam turbine exhaust steam waste heat.The system in which steam turbine exhaust steam side is connected with the exhaust steam main pipeline of air cooling island, and is communicated with preheating condenser, deaerator, low-temperature evaporator gas inlet in exhaust steam side and is equipped with valve;Low-temperature evaporator gas outlet, deaerator and preheating condenser gas inlet are communicated;Waste water adjusting dosing device, preheating condenser, deaerator are communicated, and deaerator shell side outlet is connected with deaeration front liquid tank, and deaeration front liquid tank is connected with deaerator spray pipe, low-temperature evaporator, and low-temperature evaporator shell side outlet is connected with concentrated water tank, and concentrated water tank is connected with low-temperature evaporator spray pipe;Preheating condenser and deaerator outlet are connected with condensate water buffer tank, and buffer tank, low-temperature evaporator outlet are connected with condensate water pool.The present application can make full use of steam turbine exhaust steam waste heat, efficiently treat sewage, and make full use of sewage evaporation concentration secondary steam, improve energy utilization, reduce operating cost.

Description

Technical Field

[0001] This invention relates to the fields of waste heat utilization from steam turbine exhaust and wastewater treatment, and in particular to a wastewater treatment system and method utilizing waste heat from steam turbine exhaust. Background Technology

[0002] Traditional industrial steam turbines are widely used. Typically, in these systems, thermal energy is used to generate high-temperature, high-pressure steam. This steam drives the turbine rotor, converting the thermal energy of the high-pressure steam into mechanical energy to perform work. This mechanical energy can be used directly or used to generate electricity. To achieve high energy conversion efficiency, the lower the back pressure of the turbine exhaust steam, the better. For turbine exhaust steam, water-cooled or air-cooled condensation is commonly used. Water-cooled condensation involves condensing the exhaust steam through a shell-and-tube heat exchanger, directly condensing it into water without utilizing its latent heat. Air-cooled condensation involves condensing the steam into water through heat exchange between the fins and the ambient temperature. This traditional condensation process typically results in a loss of over 50% of the total heat, with a large amount of latent heat in the exhaust steam being wasted. Although the hot water produced during condensation can be used for some process heating, improving thermal energy utilization efficiency to some extent, this method is still inefficient. Therefore, existing turbine exhaust steam waste heat treatment technologies do not fully utilize the latent heat of turbine exhaust steam, resulting in low waste heat utilization and significant energy waste. Wastewater, especially high-salinity wastewater, requires a series of heat treatment processes, and existing wastewater treatment technologies increase treatment costs due to the need for a large amount of heat. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a wastewater treatment system and method that utilizes the waste heat of steam turbine exhaust. This system can fully utilize the waste heat of steam turbine exhaust, efficiently treat wastewater, and fully utilize the secondary steam waste heat generated by wastewater evaporation and concentration, thereby improving energy efficiency and reducing operating costs.

[0004] The technical solution of this invention is as follows:

[0005] A wastewater treatment system utilizing the waste heat of steam turbine exhaust includes a wastewater regulating and dosing device, an air-cooled island 8, a preheating condenser 9, a deaerator 11, a low-temperature evaporator 14, and a controller. The exhaust steam outlet of the steam turbine is connected to the air inlet of the air-cooled island 8 through a main exhaust steam pipeline.

[0006] A main electric switch valve 17-1 is installed on the exhaust steam main pipeline. On the side of the main electric switch valve 17-1 closest to the steam turbine, the exhaust steam main pipeline is connected to the shell-side inlet of the preheating condenser 9, the tube-side inlet of the deaerator 11, and the tube-side inlet of the low-temperature evaporator 14 via three exhaust steam branch pipes. The shell-side outlet of the low-temperature evaporator 14, the tube-side inlet of the deaerator 11, and the shell-side inlet of the preheating condenser 9 are connected to the secondary steam main pipeline via three first and second steam branch pipes. The other shell-side outlet of the low-temperature evaporator 14 and the shell-side outlet of the deaerator 11 are connected to the inlet of the air-cooled island 8 via two second and second steam branch pipes. Each exhaust steam branch pipe and secondary steam branch pipe is equipped with a separate electric switch valve 17-2.

[0007] The outlet of the wastewater regulating and dosing device is connected to the tube-side inlet of the preheating condenser 9. The tube-side outlet of the preheating condenser 9 is connected to the shell-side inlet of the deaerator 11. The shell-side outlet of the deaerator 11 is connected to a pre-deaeration liquid tank 12. The outlet of the pre-deaeration liquid tank 12 is connected to the spray pipe inlet of the deaerator 11 via a first spray pipe. Another outlet of the pre-deaeration liquid tank 12 is connected to the shell-side inlet of the low-temperature evaporator 14 via a first concentrated water pipe. The shell-side outlet of the low-temperature evaporator 14 is connected to a concentrated water tank 15. The outlet of the concentrated water tank 15 is connected to the spray pipe inlet of the low-temperature evaporator 14 via a second spray pipe. Another outlet is connected to a second concentrate pipe; the shell-side outlet of the preheating condenser 9 is connected to a first condensate buffer tank 10, and the tube-side outlet of the deaerator 11 is connected to a second condensate buffer tank 13. The outlets of the first condensate buffer tank 10, the second condensate buffer tank 13, and the tube-side outlet of the low-temperature evaporator 14 are respectively connected to the condensate pool 18 via the first condensate pipe, the second condensate pipe, and the third condensate pipe; a spray pump, a concentrate pump, and a condensate pump are respectively installed on the spray pipe, the concentrate pipe, and the condensate pipe; the shell-side and tube-side of the low-temperature evaporator 14 are respectively connected to water ring vacuum pumps 19-8; all valves and pumps are electrically connected to the controller.

[0008] Furthermore, including a thickener 16, another outlet of the concentrate tank 15 is connected to the inlet of the thickener 16 via a second concentrate pipe; the wastewater conditioning and dosing device includes a wastewater tank 1, a pH adjustment tank 2, a slurry tank 3, and a pre-evaporation liquid tank 4 connected in sequence. The pH adjustment tank 2 is connected to a sulfuric acid storage tank 5 via a sulfuric acid pipe. The slurry tank 3 is connected to an emulsification tank 6. A belt scale 7 is installed above the emulsification tank 6, and the outlet of the belt scale 7 is connected to the inlet of the emulsification tank 6. The outlet of the thickener 16 is connected to the inlet of the slurry tank 3 via an underflow pipe, and the outlet of the pre-evaporation liquid tank 4 is connected to... The inlet of the preheating condenser 9 is connected to the tube side; the slurry tank 3 is sealed with nitrogen; the emulsification tank 6, the slurry tank 3, and the pre-evaporation liquid tank 4 are all equipped with stirring devices; the pipes connecting the wastewater tank 1, the pH adjustment tank 2, the slurry tank 3, the pre-evaporation liquid tank 4, the preheating condenser 9, and the emulsification tank 6, as well as the underflow pipe, are all equipped with lift pumps 19-9; the sulfuric acid pipe is equipped with a metering pump 19-10; the pH adjustment tank 2 is equipped with a pH meter; the slurry tank 3 is equipped with a level gauge; the belt scale 7, lift pump 19-9, metering pump 19-10, pH meter, and level gauge are all electrically connected to the controller.

[0009] Furthermore, the pH meter is used to measure the pH value of the mixed solution of sewage and concentrated sulfuric acid in the pH adjustment tank 2 and transmit the obtained pH value data to the controller. The controller is used to control the metering pump 19-10 to shut down when the pH value reaches a preset pH threshold. The level gauge is used to measure the liquid level of the solution in the slurry tank 3 and transmit the measured liquid level data to the controller. The controller is used to calculate the volume of the solution in the slurry tank 3 based on the liquid level and calculate the amount of scale inhibitor to be added based on the volume, thereby controlling the belt scale 7 to weigh the corresponding amount of scale inhibitor.

[0010] Furthermore, the pipes connecting the wastewater tank 1, pH adjustment tank 2, slurry tank 3, pre-evaporation liquid tank 4, and preheating condenser 9 all have common pipes and spare pipes, and common booster pumps and spare booster pumps are respectively installed on the common pipes and spare pipes.

[0011] Furthermore, it includes a cooling condenser 20, which includes an open cooling tower, a first water condenser, and a second water condenser. The first water condenser and the second water condenser are both connected to the open cooling tower. The other shell-side outlet of the low-temperature evaporator 14 and the shell-side outlet of the deaerator 11 are respectively connected to the inlets of the first water condenser and the second water condenser.

[0012] A method for treating wastewater using the aforementioned wastewater treatment system that utilizes the waste heat from a steam turbine includes the following steps:

[0013] Step 1: pH adjustment and dosing

[0014] Wastewater is pumped from wastewater tank 1 into pH adjustment tank 2 via lift pump 19-9. While stirring in pH adjustment tank 2, 98% concentrated sulfuric acid is added from sulfuric acid storage tank 5 using metering pump 19-10. The controller interlocks the pH meter and metering pump 19-10 to ensure the pH value of the wastewater in pH adjustment tank 2 reaches the preset pH threshold. The pH-adjusted wastewater is then pumped from pH adjustment tank 2 into slurry tank 3 via lift pump 19-9. While stirring in slurry tank 3, the controller interlocks the level gauge and belt scale 7 to ensure the belt scale 7 weighs the required amount of scale inhibitor and sends it to emulsification tank 6. The emulsified scale inhibitor is then pumped from emulsification tank 6 into slurry tank 3 via lift pump 19-9. Finally, the slurry-treated wastewater is pumped from slurry tank 3 into pre-evaporation liquid tank 4 via lift pump 19-9.

[0015] Step 2: Preheating

[0016] A water ring vacuum pump is used to establish negative pressure in the exhaust steam branch pipe to introduce the turbine exhaust steam into the shell side of the preheating condenser 9. The slurry-processed wastewater is sent from the pre-evaporation liquid tank 4 into the tube side of the preheating condenser 9. The waste heat of the exhaust steam is used to preheat the wastewater in the preheating condenser 9. The preheated wastewater is sent into the shell side of the deaerator 11. The condensate after the exhaust steam is condensed enters the first condensate buffer tank 10.

[0017] Step 3: Deoxygenation

[0018] Exhaust steam from the turbine is introduced into the tube side of the deaerator 11, and wastewater in the deaerator 11 is sent to the pre-deaeration liquid tank 12. The wastewater is pumped from the pre-deaeration liquid tank 12 into the spray pipe of the deaerator 11 using a spray pump. The spray pipe is controlled to repeatedly spray the tube side of the deaerator 11 to deoxygenate the wastewater. The deoxygenated wastewater is pumped from the pre-deaeration liquid tank 12 into the shell side of the low-temperature evaporator 14 using a concentrate pump. The condensate after the exhaust steam is condensed enters the second condensate buffer tank 13.

[0019] Step 4: Evaporation and Concentration

[0020] Exhaust steam from the turbine is introduced into the tube side of the low-temperature evaporator 14. Wastewater in the low-temperature evaporator 14 is sent to the concentrate tank 15. The wastewater is pumped from the concentrate tank 15 into the spray pipe of the low-temperature evaporator 14 using a spray pump. The spray pipe is controlled to repeatedly spray the tube side of the low-temperature evaporator 14 to evaporate and concentrate the wastewater. The concentrated wastewater is sent from the concentrate tank 15 to the thickener 16 using a concentrate pump. The condensate after the exhaust steam is condensed is pumped into the condensate pool 18 by a condensate pump.

[0021] Step 5: Secondary steam condensation

[0022] The secondary steam generated by the evaporation of wastewater in the deaerator 11 and the low-temperature evaporator 14 is sent to the air-cooled island 8 for condensation.

[0023] Furthermore, when the total amount of condensate generated reaches the preset condensate volume threshold, the electric switch valve 17-2 on the exhaust steam branch pipe and the second secondary steam branch pipe connected to the deaerator 11 and the preheating condenser 9 is closed, and the electric switch valve 17-2 on the first secondary steam branch pipe is opened, thereby sending the secondary steam generated by the evaporation of sewage in the low-temperature evaporator 14 into the tube side of the deaerator 11 and the shell side of the preheating condenser 9, and switching the heat source used for sewage treatment from exhaust steam to secondary steam.

[0024] Furthermore, when turbine exhaust steam is introduced as a heat source, the gas pressure in the exhaust steam branch pipe is controlled at -0.090 to -0.002 MPa and the temperature at 45℃ to 99℃; when secondary steam is introduced as a heat source, the pressure of the secondary steam in the evaporation chamber of the low-temperature evaporator 14 is controlled at -0.093 MPa to -0.014 MPa and the temperature at 40℃ to 95℃.

[0025] Furthermore, when the liquid level in the first condensate buffer tank 10 reaches a preset liquid level threshold, the condensate in the first condensate buffer tank 10 is sent to the condensate pool 18 using a condensate pump; when the liquid level in the second condensate buffer tank 13 reaches a preset liquid level threshold, the condensate in the second condensate buffer tank 13 is sent to the condensate pool 18 using a condensate pump.

[0026] Furthermore, the preset pH threshold is 4-7; if the wastewater in wastewater tank 1 is softened wastewater, the slurrying process is skipped and the pH-adjusted wastewater is directly pumped from pH adjustment tank 2 into pre-evaporation liquid tank 4.

[0027] The beneficial effects of this invention are as follows:

[0028] (1) This invention introduces turbine exhaust steam into the wastewater treatment process by setting a main electric switch valve on the exhaust steam main pipeline connecting the turbine exhaust steam outlet and the air-cooled island, and setting an exhaust steam branch pipe on the exhaust steam side of the main electric switch valve to connect to the wastewater treatment device. This can make full use of the waste heat of the turbine exhaust steam, ensure that the turbine drive condition is not affected, maintain the turbine's high working efficiency, and efficiently treat wastewater. This greatly reduces the cost of exhaust steam treatment and wastewater treatment, and solves the technical problems of low waste heat utilization rate in existing turbine exhaust steam waste heat utilization technology and increased treatment cost in existing wastewater treatment technology due to the need for more heat.

[0029] (2) By setting up a wastewater regulating and dosing device, a preheating condenser, a deaerator, and a low-temperature evaporator, this invention can regulate and dosing, preheat, deaerator, and evaporate and concentrate wastewater, thereby improving the wastewater treatment effect. In addition to setting up a main electric switch valve and a waste steam branch pipe to introduce waste steam into the wastewater treatment process, a secondary steam main pipeline is also set up to connect the outlet of the low-temperature evaporator, the inlet of the deaerator, and the preheating condenser through secondary steam branch pipes. A controller is set up and a sub-electric switch valve is set up on the steam branch pipe. During the initial start-up, the turbine waste steam can be used as a heat source for preheating, deaerator, and evaporation and concentration of wastewater. After the operation is stable, it automatically switches to the secondary steam generated by the evaporation and concentration of wastewater as the heat source. This fully utilizes the waste heat of the waste steam and the secondary steam generated by the evaporation and concentration of wastewater, thereby improving energy utilization and reducing operating costs.

[0030] (3) By connecting the shell-side outlet of the low-temperature evaporator and the deaerator to the air-cooled island, the present invention can condense the secondary steam generated by the evaporation of sewage in the low-temperature evaporator and the deaerator. The condensate is high-quality water with stable water quality, which meets the water quality standards for water replenishment and circulating water replenishment, which is conducive to recycling and reuse, and further improves the energy utilization rate.

[0031] (4) This invention sets up a cooling and condensing device consisting of an open cooling tower and two water condensers, and connects the shell outlets of the low-temperature evaporator and the deaerator to the two water condensers respectively. It can be used in conjunction with the air-cooled island to condense secondary steam according to the working conditions, thus making up for the shortcomings of the air-cooled island alone in condensing secondary steam. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the wastewater regulating and dosing device in the wastewater treatment system utilizing the waste heat of steam turbines according to a specific embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the structure of the wastewater treatment system utilizing the waste heat of a steam turbine according to a specific embodiment of the present invention, after removing the wastewater regulating and dosing device.

[0034] In the diagram, 1—wastewater tank, 2—pH adjustment tank, 3—slurry tank, 4—pre-evaporation liquid tank, 5—sulfuric acid storage tank, 6—emulsification tank, 7—belt scale, 8—air-cooled island, 9—preheating condenser, 10—first condensate buffer tank, 11—deaerator, 12—pre-deaerator liquid tank, 13—second condensate buffer tank, 14—low-temperature evaporator, 15—concentrate tank, 16—thickener, 17-1—main electric switch valve, 17-2—individual electric switch valve, 18—condensate tank, 19-1—first spray pump, 19-2—second spray pump, 19-3—first concentrate pump, 19-4—second concentrate pump, 19-5—first condensate pump, 19-6—second condensate pump, 19-7—third condensate pump, 19-8—water ring vacuum pump, 19-9—lift pump, 19-10—metering pump, 20—cooling condenser. Detailed Implementation

[0035] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0036] See Figure 1 , Figure 2 The wastewater treatment system utilizing the waste heat of steam turbine exhaust includes a wastewater regulating and dosing device, an air-cooled island 8, a preheating condenser 9, a deaerator 11, a low-temperature evaporator 14, and a controller (not shown in the figure). The exhaust steam outlet of the steam turbine is connected to the air inlet of the air-cooled island 8 through the exhaust steam main pipeline.

[0037] like Figure 2 As shown, a main electric switch valve 17-1 is installed on the main exhaust steam pipeline. The main exhaust steam pipeline is connected to the shell-side air inlet of the preheating condenser 9, the tube-side air inlet of the deaerator 11, and the tube-side air inlet of the low-temperature evaporator 14 via three exhaust steam branch pipes on the side of the main electric switch valve 17-1 near the steam turbine. The exhaust steam generated during turbine operation has a temperature of 57℃ to 59℃, representing a huge latent heat resource. Failure to utilize this resource would result in significant waste. This invention addresses this by installing a main electric switch valve 17-1 on the exhaust steam main pipeline connecting the turbine exhaust steam outlet to the air-cooled island 8, and by establishing an exhaust steam branch pipe on the exhaust steam side of the main electric switch valve 17-1 connected to the wastewater treatment device. This allows the turbine exhaust steam to be introduced into the wastewater treatment process, fully utilizing the waste heat of the turbine exhaust steam while ensuring that the turbine's traction operation is unaffected and maintaining high power efficiency. It also enables efficient wastewater treatment, significantly reducing the costs of exhaust steam and wastewater treatment. This invention solves the technical problems of low waste heat utilization rates in existing turbine exhaust steam waste heat utilization technologies and the increased treatment costs of existing wastewater treatment technologies due to the need for large amounts of heat.

[0038] The shell-side outlet of the low-temperature evaporator 14, the tube-side inlet of the deaerator 11, and the shell-side inlet of the preheating condenser 9 are respectively connected to the secondary steam main pipeline through three first and second steam branch pipes. This invention, by setting up a wastewater regulating and dosing device, a preheating condenser 9, a deaerator 11, and a low-temperature evaporator 14, can regulate and dosing chemicals, preheat, deaerate, and evaporate and concentrate wastewater, thereby improving the wastewater treatment effect. In addition to setting up a main electric switch valve 17-1 and a waste steam branch pipe to introduce waste steam into the wastewater treatment process, a secondary steam main pipeline is also set up to connect the outlet of the low-temperature evaporator 14, the inlet of the deaerator 11, and the preheating condenser 9 through secondary steam branch pipes. A controller is set up, and a sub-electric switch valve 17-2 is set up on the steam branch pipe. During the initial start-up, the turbine waste steam can be used as a heat source for preheating, deaeration, and evaporation and concentration of wastewater. After the operation is stable, it automatically switches to the secondary steam generated by the evaporation and concentration of wastewater as the heat source. This makes full use of the waste heat of both the waste steam and the secondary steam generated by the evaporation and concentration of wastewater, improving energy utilization and reducing operating costs.

[0039] The shell-side outlet of the low-temperature evaporator 14 and the shell-side outlet of the deaerator 11 are respectively connected to the air inlet of the air-cooled island 8 through two second and secondary steam branch pipes; each of the exhaust steam branch pipe and the secondary steam branch pipe is equipped with a separate electric switch valve 17-2. By connecting the shell-side outlets of the low-temperature evaporator 14 and the deaerator 11 to the air-cooled island 8, this invention can condense the secondary steam generated by the evaporation of wastewater in the low-temperature evaporator 14 and the deaerator 11. The condensate is high-quality product water with stable water quality, which meets the water quality standards for water replenishment and circulating water, and is conducive to recycling and reuse, further improving energy utilization.

[0040] The outlet of the wastewater regulating and dosing device is connected to the tube-side inlet of the preheating condenser 9. The tube-side outlet of the preheating condenser 9 is connected to the shell-side inlet of the deaerator 11. The shell-side outlet of the deaerator 11 is connected to a pre-deaeration liquid tank 12. The outlet of the pre-deaeration liquid tank 12 is connected to the spray pipe inlet of the deaerator 11 via a first spray pipe. Another outlet of the pre-deaeration liquid tank 12 is connected to the shell-side inlet of the low-temperature evaporator 14 via a first concentrate pipe. The shell-side outlet of the low-temperature evaporator 14 is connected to a concentrate tank 15. The outlet of 5 is connected to the inlet of the spray pipe of the low-temperature evaporator 14 through the second spray pipe. The other outlet of the concentrate tank 15 is connected to the second concentrate pipe. The shell outlet of the preheating condenser 9 is connected to the first condensate buffer tank 10. The tube outlet of the deaerator 11 is connected to the second condensate buffer tank 13. The outlets of the first condensate buffer tank 10, the second condensate buffer tank 13, and the tube outlet of the low-temperature evaporator 14 are respectively connected to the condensate pool 18 through the first condensate pipe, the second condensate pipe, and the third condensate pipe.

[0041] Spray pumps, concentrate pumps, and condensate pumps are respectively installed on the spray pipes, concentrate pipes, and condensate pipes. Specifically, for example... Figure 2 As shown, a first spray pump 19-1 and a second spray pump 19-2 are respectively installed on the first and second spray pipes; a first concentrate pump 19-3 and a second concentrate pump 19-4 are respectively installed on the first and second concentrate pipes; and a first condensate pump 19-5, a second condensate pump 19-6, and a third condensate pump 19-7 are respectively installed on the first, second, and third condensate pipes. A water ring vacuum pump 19-8 is connected to both the shell side and tube side of the low-temperature evaporator 14. All valves and pumps are electrically connected to the controller.

[0042] In this embodiment, as Figure 2 As shown, the wastewater treatment system utilizing the waste heat of a steam turbine of the present invention also includes a thickener 16, and another outlet of the concentrate tank 15 is connected to the inlet of the thickener 16 through a second concentrate pipe; as Figure 1 As shown, the wastewater conditioning and dosing device includes a wastewater tank 1, a pH adjustment tank 2, a slurry tank 3, and a pre-evaporation liquid tank 4 connected in sequence. The pH adjustment tank 2 is connected to a sulfuric acid storage tank 5 via a sulfuric acid pipeline. The slurry tank 3 is connected to an emulsification tank 6. A belt scale 7 is installed above the emulsification tank 6, and the outlet of the belt scale 7 is connected to the inlet of the emulsification tank 6. The outlet of the thickener 16 is connected to the inlet of the slurry tank 3 via an underflow pipeline. The outlet of the pre-evaporation liquid tank 4 is connected to the tube-side inlet of the preheating condenser 9. The slurry tank 3 is sealed with nitrogen. A stirring device is installed in the emulsification tank 6, the slurry tank 3, and the pre-evaporation liquid tank 4. A booster pump 19-9 is installed on the pipes connecting the wastewater tank 1, the pH adjustment tank 2, the slurry tank 3, the pre-evaporation liquid tank 4, the preheating condenser 9, and the emulsification tank 6, as well as on the underflow pipe. A metering pump 19-10 is installed on the sulfuric acid pipe. A pH meter (not shown in the figure) is installed in the pH adjustment tank 2. A level gauge (not shown in the figure) is installed in the slurry tank 3. The belt scale 7, the booster pump 19-9, the metering pump 19-10, the pH meter, and the level gauge are all electrically connected to the controller.

[0043] The pH meter is used to measure the pH value of the mixed solution of sewage and concentrated sulfuric acid in the pH adjustment tank 2 and transmit the obtained pH value data to the controller. The controller is used to control the metering pump 19-10 to shut down when the pH value reaches a preset pH threshold. The level gauge is used to measure the liquid level of the solution in the slurry tank 3 and transmit the measured liquid level data to the controller. The controller is used to calculate the volume of the solution in the slurry tank 3 based on the liquid level and calculate the amount of scale inhibitor to be added based on the volume, thereby controlling the belt scale 7 to weigh the corresponding amount of scale inhibitor.

[0044] In this embodiment, as Figure 1 As shown, the pipes connecting the wastewater tank 1, pH adjustment tank 2, slurry tank 3, pre-evaporation liquid tank 4, and preheating condenser 9 all have main and backup pipes. Main and backup booster pumps are respectively installed on the main and backup pipes. When the main booster pump fails, the backup booster pump is activated, ensuring that the wastewater treatment process is not affected by the booster pump failure, thereby guaranteeing the continuous and stable operation of the wastewater treatment process. It should be noted that, unless otherwise specified, all pumps in the attached diagram are booster pumps. In this embodiment, the booster pumps are fluoroplastic chemical pumps, and valves are installed on the corresponding pipes on both sides of all booster pumps 19-9 and metering pumps 19-10.

[0045] In this embodiment, as Figure 2 As shown, the wastewater treatment system utilizing the waste heat of steam turbine exhaust steam of the present invention further includes a cooling condensing device 20. The cooling condensing device 20 includes an open cooling tower, a first water condenser, and a second water condenser. Both the first and second water condensers are connected to the open cooling tower. The other shell-side outlet of the low-temperature evaporator 14 and the shell-side outlet of the deaerator 11 are respectively connected to the inlets of the first and second water condensers. By setting up a cooling condensing device 20 consisting of an open cooling tower and two water condensers, and connecting the shell-side outlets of the low-temperature evaporator 14 and the deaerator 11 to the two water condensers, the present invention can condense secondary steam in conjunction with an air-cooled island, compensating for the shortcomings of a purely air-cooled island for condensing secondary steam.

[0046] The method for wastewater treatment using the wastewater treatment system utilizing the waste heat from a steam turbine, according to the present invention, includes the following steps:

[0047] Step 1: pH adjustment and dosing

[0048] Wastewater is pumped from wastewater tank 1 into pH adjustment tank 2 via lift pump 19-9. While stirring in pH adjustment tank 2, 98% concentrated sulfuric acid is added from sulfuric acid storage tank 5 using metering pump 19-10. The pH value of the wastewater in pH adjustment tank 2 is brought to the preset pH threshold using the interlocking control of the pH meter and metering pump 19-10 by the controller. The pH-adjusted wastewater is then pumped from pH adjustment tank 2 into slurry tank 3 via lift pump 19-9. While stirring in slurry tank 3, the required amount of scale inhibitor is weighed by the belt scale 7 and sent to emulsification tank 6 using the interlocking control of the level gauge and belt scale 7 by the controller. The emulsified scale inhibitor is then pumped from emulsification tank 6 into slurry tank 3 via lift pump 19-9. Finally, the slurry-treated wastewater is pumped from slurry tank 3 into pre-evaporation liquid tank 4 via lift pump 19-9.

[0049] In step 1, the preset pH threshold is 4-7. In another embodiment of the present invention, the pH adjustment tank 2 is connected to the pre-evaporation liquid tank 4 through a pipe, and a lift pump 19-9 is installed on the connected pipe. When the sewage in the wastewater tank 1 is softened sewage, the slurrying process is skipped and the pH-adjusted sewage is directly pumped from the pH adjustment tank 2 into the pre-evaporation liquid tank 4. The controller's interlocking control of the pH meter and metering pump 19-10 is as follows: the pH meter measures the pH value of the solution in the pH adjustment tank 2 and transmits the obtained pH value data to the controller. When the pH value reaches the preset pH threshold, the controller controls the metering pump 19-10 to stop adding acid. The controller's interlocking control of the level gauge and belt scale 7 is as follows: the level gauge measures the liquid level of the solution in the slurry tank 3 and transmits the measured liquid level data to the controller. The controller calculates the volume of the solution in the slurry tank 3 based on the liquid level and calculates the amount of scale inhibitor to be added based on the volume, thereby controlling the belt scale 7 to weigh the required amount of scale inhibitor. The scale inhibitor is used to induce the directional crystallization of calcium sulfate, thereby preventing scale formation on the heat exchange tubes. The scale inhibitor dosage per ton of water in the emulsification tank 6 is fixed, and the amount of scale inhibitor added to the emulsification tank 3 is also fixed. The scale inhibitor entering the thickener 16 returns to the emulsification tank 3 via the underflow pipe for recycling and reuse. The amount of scale inhibitor added to the emulsification tank 3 = scale inhibitor dosage in the emulsification tank 3 + underflow return scale inhibitor dosage + scale inhibitor added to the emulsification tank 6 = 40-60 kg / m³ 3 .

[0050] Step 2: Preheating

[0051] A water ring vacuum pump is used to create negative pressure in the exhaust steam branch pipe, introducing the turbine exhaust steam into the shell side of the preheating condenser 9. Slurry-processed wastewater is sent from the pre-evaporation liquid tank 4 into the tube side of the preheating condenser 9, utilizing the waste heat of the exhaust steam to preheat the wastewater in the preheating condenser 9. The preheated wastewater is then sent to the shell side of the deaerator 11. The condensate from the condensation of the exhaust steam enters the first condensate buffer tank 10. When the liquid level in the first condensate buffer tank 10 reaches a preset threshold, the first condensate pump 19-5 sends the condensate in the first condensate buffer tank 10 into the condensate pool 18.

[0052] Step 3: Deoxygenation

[0053] Exhaust steam from the turbine is introduced into the tube side of deaerator 11, and wastewater in deaerator 11 is sent to pre-deaeration liquid tank 12. A first spray pump 19-1 pumps the wastewater from pre-deaeration liquid tank 12 into the spray pipes of deaerator 11, controlling the spray pipes to repeatedly spray the tube side of deaerator 11 to deoxygenate the wastewater. A first concentrate pump 19-3 pumps the deoxygenated wastewater from pre-deaeration liquid tank 12 into the shell side of low-temperature evaporator 14. The condensate from the condensed exhaust steam enters the second condensate buffer tank 13. When the liquid level in the second condensate buffer tank 13 reaches a preset threshold, a second condensate pump 19-6 sends the condensate in the second condensate buffer tank 13 into condensate pool 18.

[0054] Step 4: Evaporation and Concentration

[0055] Exhaust steam from the turbine is introduced into the tube side of the low-temperature evaporator 14. Wastewater from the low-temperature evaporator 14 is sent to the concentrate tank 15. A second spray pump 19-2 pumps the wastewater from the concentrate tank 15 into the spray pipes of the low-temperature evaporator 14, controlling the spray pipes to repeatedly spray the tube side of the low-temperature evaporator 14 to concentrate the wastewater. Specifically, wastewater in the concentrate tank 15 is sent to the top of the low-temperature evaporator 14 by the second spray pump 19-2, and sprayed onto the heat exchange tube bundle through nozzles. It flows down the heat exchange tube bundle layer by layer from top to bottom, evaporating under the heating of the tube bundle. The negative pressure of the steam generated by the wastewater evaporation is controlled by a water ring vacuum pump. A second concentrate pump 19-4 sends the concentrated wastewater from the concentrate tank 15 to the thickener 16. The condensate from the condensation of the exhaust steam is pumped into the condensate pool 18 by a third condensate pump 19-7. The low-temperature evaporator 14 creates a low-temperature and negative-pressure environment through the condensation of secondary steam. As the exhaust steam exchanges heat with the wastewater to form condensate, its volume suddenly shrinks, creating a large suction force. The exhaust steam can then continuously flow into the low-temperature evaporator 14 by gravity, stopping the water ring vacuum pump 19-8. The temperature and pressure differences between the exhaust steam and the secondary steam from the wastewater evaporation process ensure a continuous flow of exhaust steam to the low-temperature evaporator 14 by gravity.

[0056] Step 5: Secondary steam condensation

[0057] The secondary steam generated from the evaporation of wastewater in the deaerator 11 and the low-temperature evaporator 14 is sent to the air-cooled island 8 for condensation. In this embodiment, because a cooling condenser 20 is installed, when the summer wind temperature is too high to support the condensation of secondary steam by the air-cooled island 8, the secondary steam is introduced into the cooling condenser 20 by switching valves, and the cooling condenser 20 is used to condense the secondary steam, compensating for the inadequacy of the air-cooled island alone in condensing secondary steam. When the winter wind temperature is low, the cooling condenser 20 is shut off, and the air-cooled island 8 simultaneously condenses both exhaust steam and secondary steam, making full use of wind energy and avoiding the heat consumption of the cooling condenser 20 in cooling the secondary steam.

[0058] In this embodiment, after the low-temperature evaporation operation is established, the heat source is changed to the secondary steam from wastewater evaporation by switching valves. Specifically, when the total amount of condensate generated reaches the preset condensate volume threshold, the electric switch valve 17-2 on the exhaust steam branch pipe and the second secondary steam branch pipe connected to the deaerator 11 and the preheating condenser 9 is closed, and the electric switch valve 17-2 on the first secondary steam branch pipe is opened. This allows the secondary steam generated from wastewater evaporation in the low-temperature evaporator 14 to be sent to the tube side of the deaerator 11 and the shell side of the preheating condenser 9, switching the heat source for wastewater treatment from exhaust steam to secondary steam. When turbine exhaust steam is introduced as a heat source, the gas pressure in the exhaust steam branch pipe is controlled at -0.090 to -0.002 MPa, and the temperature at 45°C to 99°C. When secondary steam is introduced as a heat source, the pressure of the secondary steam in the evaporation chamber of the low-temperature evaporator 14 is controlled at -0.093 MPa to -0.014 MPa, and the temperature at 40°C to 95°C.

[0059] In this embodiment, in addition to controlling the wastewater pH and reagent metering, the controller also controls the vacuum and temperature of the turbine exhaust steam by controlling the operating frequency of the fan on the air-cooled island 8. Based on the evaporation and condensation rates, the controller controls the vacuum of the shell side of the low-temperature evaporator 14 through the water ring vacuum pump, and controls the vacuum of the tube side of the low-temperature evaporator 14 by controlling the operating frequency of the fan on the air-cooled island 8. The controller also controls the secondary gas pressure and temperature by controlling the air-cooled island 8 and the water ring vacuum pump, and controls the evaporation water production rate and adjusts the valve opening. This achieves the interlocked control of the cryogenic oxygen production process turbine unit and exhaust steam recovery system, turbine mode, low-temperature evaporation device process, wastewater conditioning and dosing, preheating and deoxygenation heat source.

[0060] Obviously, the above embodiments are merely some, not all, of the embodiments of the present invention. The above embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without inventive effort, that is, all modifications, equivalent substitutions, and improvements made within the spirit and principle of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A wastewater treatment system utilizing the waste heat of steam turbine exhaust, characterized in that, It includes a wastewater conditioning and dosing device, an air-cooled island (8), a preheating condenser (9), a deaerator (11), a low-temperature evaporator (14), and a controller. The exhaust steam outlet of the steam turbine is connected to the air inlet of the air-cooled island (8) through the exhaust steam main pipeline. The main exhaust steam pipeline is equipped with a main electric switch valve (17-1). The main exhaust steam pipeline is connected to the shell-side inlet of the preheating condenser (9), the tube-side inlet of the deaerator (11), and the tube-side inlet of the low-temperature evaporator (14) via three exhaust steam branch pipes on the side of the main electric switch valve (17-1) near the steam turbine. The shell-side outlet of the low-temperature evaporator (14), the other tube-side inlet of the deaerator (11), and the other shell-side inlet of the preheating condenser (9) are connected to the secondary steam pipeline via three first and second steam branch pipes. The other shell-side outlet of the low-temperature evaporator (14) and the shell-side outlet of the deaerator (11) are connected to the inlet of the air-cooled island (8) via two second and second steam branch pipes. Each exhaust steam branch pipe and secondary steam branch pipe is equipped with a separate electric switch valve (17-2). The outlet of the wastewater regulating and dosing device is connected to the tube-side inlet of the preheating condenser (9), the tube-side outlet of the preheating condenser (9) is connected to the shell-side inlet of the deaerator (11), the shell-side outlet of the deaerator (11) is connected to a pre-deaeration liquid tank (12), the outlet of the pre-deaeration liquid tank (12) is connected to the spray pipe inlet of the deaerator (11) through a first spray pipe, the other outlet of the pre-deaeration liquid tank (12) is connected to the shell-side inlet of the low-temperature evaporator (14) through a first concentrated water pipe, the shell-side outlet of the low-temperature evaporator (14) is connected to a concentrated water tank (15), the outlet of the concentrated water tank (15) is connected to the spray pipe inlet of the low-temperature evaporator (14) through a second spray pipe, the concentrated water tank (15) is connected to the concentrated water tank (15) through a second spray pipe, the concentrated water tank (15) is connected to the spray pipe inlet of the low-temperature evaporator (14) through a second spray pipe, the concentrated water tank (15) is connected to the concentrated water tank (15) through a first concentrated water pipe, the shell-side outlet of the deaerator (14) is connected to the pre-deaeration liquid tank (15) through a first concentrated water pipe, the shell-side outlet of the deaerator (14) is connected to the pre-deaeration liquid tank (15) through a first concentrated water pipe, the shell-side outlet of the deaerator (15 ... The other outlet of 15) is connected to a second concentrate pipe; the shell outlet of the preheating condenser (9) is connected to a first condensate buffer tank (10), and the tube outlet of the deaerator (11) is connected to a second condensate buffer tank (13). The outlets of the first condensate buffer tank (10), the second condensate buffer tank (13), and the tube outlet of the low-temperature evaporator (14) are connected to the condensate pool (18) through the first condensate pipe, the second condensate pipe, and the third condensate pipe, respectively. Spray pumps, concentrate pumps, and condensate pumps are respectively installed on the spray pipes, concentrate pipes, and condensate pipes. The shell and tube sides of the low-temperature evaporator (14) are respectively connected to water ring vacuum pumps (19-8). All valves and pumps are electrically connected to the controller. The system includes a thickener (16), with another outlet of the concentrate tank (15) connected to the inlet of the thickener (16) via a second concentrate pipe; the wastewater conditioning and dosing device includes a wastewater tank (1), a pH adjustment tank (2), a slurry tank (3), and a pre-evaporation liquid tank (4) connected in sequence; the pH adjustment tank (2) is connected to a sulfuric acid storage tank (5) via a sulfuric acid pipe; the slurry tank (3) is connected to an emulsification tank (6); a belt scale (7) is installed above the emulsification tank (6); the outlet of the belt scale (7) is connected to the inlet of the emulsification tank (6); the outlet of the thickener (16) is connected to the inlet of the slurry tank (3) via an underflow pipe; and the outlet of the pre-evaporation liquid tank (4) is connected to a preheating cooler. The tube side inlet of the condenser (9) is connected; the slurry tank (3) is sealed with nitrogen; the emulsification tank (6), the slurry tank (3), and the pre-evaporation liquid tank (4) are all equipped with stirring devices; the wastewater tank (1), pH adjustment tank (2), slurry tank (3), pre-evaporation liquid tank (4), preheating condenser (9), and emulsification tank (6) are all connected by lift pumps (19-9) and underflow pipes; the sulfuric acid pipe is equipped with a metering pump (19-10); the pH adjustment tank (2) is equipped with a pH meter; the slurry tank (3) is equipped with a level gauge; the belt scale (7), lift pump (19-9), metering pump (19-10), pH meter, and level gauge are all electrically connected to the controller; The device includes a cooling condenser (20), which includes an open cooling tower, a first water condenser, and a second water condenser. The first water condenser and the second water condenser are both connected to the open cooling tower. The other shell-side outlet of the low-temperature evaporator (14) and the shell-side outlet of the deaerator (11) are respectively connected to the inlets of the first water condenser and the second water condenser.

2. The wastewater treatment system utilizing exhaust steam heat from a steam turbine according to claim 1, characterized in that, The pH meter is used to measure the pH value of the mixed solution of sewage and concentrated sulfuric acid in the pH adjustment tank (2) and transmit the obtained pH value data to the controller. The controller is used to control the metering pump (19-10) to shut down when the pH value reaches the preset pH threshold. The level gauge is used to measure the liquid level of the solution in the slurry tank (3) and transmit the measured liquid level data to the controller. The controller is used to calculate the volume of the solution in the slurry tank (3) based on the liquid level and calculate the amount of scale inhibitor to be added based on the volume, thereby controlling the belt scale (7) to weigh the corresponding amount of scale inhibitor.

3. The wastewater treatment system utilizing exhaust steam heat from a steam turbine according to claim 1, characterized in that, The pipes connecting the wastewater tank (1), pH adjustment tank (2), slurry tank (3), pre-evaporation liquid tank (4), and preheating condenser (9) all have common pipes and spare pipes, and common booster pumps and spare booster pumps are respectively installed on the common pipes and spare pipes.

4. A method for treating wastewater using the wastewater treatment system utilizing exhaust steam heat from a steam turbine as described in claim 1, characterized in that, Includes the following steps: Step 1: pH adjustment and dosing Wastewater is pumped from wastewater tank (1) into pH adjustment tank (2) via lift pump (19-9); while stirring in pH adjustment tank (2), 98% concentrated sulfuric acid is added from sulfuric acid storage tank (5) using metering pump (19-10); the pH value of wastewater in pH adjustment tank (2) is brought to the preset pH threshold by the interlocking control of pH meter and metering pump (19-10) by the controller; the pH-adjusted wastewater is pumped from pH adjustment tank (2) into slurry tank (3) via lift pump (19-9); while stirring in slurry tank (3), the required amount of scale inhibitor is weighed by the belt scale (7) and sent to emulsification tank (6) by the interlocking control of level gauge and belt scale (7) by the controller; the emulsified scale inhibitor is pumped from emulsification tank (6) into slurry tank (3) via lift pump (19-9); the slurry-processed wastewater is pumped from slurry tank (3) into pre-evaporation liquid tank (4) via lift pump (19-9); Step 2: Preheating A water ring vacuum pump is used to establish negative pressure in the exhaust steam branch pipe to introduce the turbine exhaust steam into the shell side of the preheating condenser (9). The slurry wastewater is sent from the pre-evaporation liquid tank (4) into the tube side of the preheating condenser (9). The waste heat of the exhaust steam is used to preheat the wastewater in the preheating condenser (9). The preheated wastewater is sent into the shell side of the deaerator (11). The condensate after the exhaust steam is condensed enters the first condensate buffer tank (10). Step 3: Deoxygenation The exhaust steam from the turbine is introduced into the tube side of the deaerator (11), and the sewage in the deaerator (11) is sent into the pre-deaeration liquid tank (12). The sewage is pumped from the pre-deaeration liquid tank (12) into the spray pipe of the deaerator (11) using a spray pump. The spray pipe is controlled to repeatedly spray the tube side of the deaerator (11) to deoxygenate the sewage. The deoxygenated sewage is pumped from the pre-deaeration liquid tank (12) into the shell side of the low-temperature evaporator (14) using a concentrate pump. The condensate after the exhaust steam is condensed enters the second condensate buffer tank (13). Step 4: Evaporation and Concentration The exhaust steam from the turbine is introduced into the tube side of the low-temperature evaporator (14), and the wastewater in the low-temperature evaporator (14) is sent into the concentrate tank (15). The wastewater is pumped from the concentrate tank (15) into the spray pipe of the low-temperature evaporator (14) using a spray pump. The spray pipe is controlled to repeatedly spray the tube side of the low-temperature evaporator (14) to make the wastewater evaporate and concentrate. The concentrated wastewater is sent from the concentrate tank (15) to the thickener (16) using a concentrate pump. The condensate after the exhaust steam is condensed is pumped into the condensate pool (18) by a condensate pump. Step 5: Secondary steam condensation The secondary steam generated by the evaporation of sewage in the deaerator (11) and low-temperature evaporator (14) is sent to the air-cooled island (8) for condensation.

5. The wastewater treatment method according to claim 4, characterized in that, When the total amount of condensate generated reaches the preset condensate volume threshold, the electric switch valve (17-2) on the exhaust steam branch pipe and the second secondary steam branch pipe connected to the deaerator (11) and the preheating condenser (9) is closed, and the electric switch valve (17-2) on the first secondary steam branch pipe is opened, so that the secondary steam generated by the evaporation of sewage in the low temperature evaporator (14) is sent to the tube side of the deaerator (11) and the shell side of the preheating condenser (9), and the heat source used for sewage treatment is switched from exhaust steam to secondary steam.

6. The wastewater treatment method according to claim 5, characterized in that, When the exhaust steam from the steam turbine is introduced as a heat source, the pressure in the exhaust steam branch pipe is controlled at -0.090 to -0.002 MPa and the temperature is controlled at 45℃ to 99℃. When the secondary steam is introduced as a heat source, the pressure of the secondary steam in the evaporation chamber of the low-temperature evaporator (14) is controlled at -0.093 MPa to -0.014 MPa and the temperature is controlled at 40℃ to 95℃.

7. The wastewater treatment method according to claim 4, characterized in that, When the liquid level in the first condensate buffer tank (10) reaches the preset liquid level threshold, the condensate in the first condensate buffer tank (10) is sent to the condensate pool (18) by the condensate pump; when the liquid level in the second condensate buffer tank (13) reaches the preset liquid level threshold, the condensate in the second condensate buffer tank (13) is sent to the condensate pool (18) by the condensate pump.

8. The wastewater treatment method according to claim 4, characterized in that, In step 1, the preset pH threshold is 4-7; if the wastewater in the wastewater tank (1) is softened wastewater, the slurry process is skipped and the pH-adjusted wastewater is directly pumped from the pH adjustment tank (2) into the pre-evaporation liquid tank (4).

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