Sewage steam stripping heat self-circulation system

Abstract

The invention provides a sewage steam stripping thermal self-circulation system which is characterized in that a first heat exchanger receives acidic water and is connected with a hot feed inlet of a steam stripping tower through a second heat exchanger, a first gas outlet of the steam stripping tower outputs ammonia gas through the second heat exchanger, and a second gas outlet outputs hydrogen sulfide; a purified water outlet of the stripping tower is respectively connected with a steam reboiler and a purified water inlet of a steam generator, a liquid outlet of the steam reboiler is connected with a condensed water inlet of the steam generator, a purified water outlet of the steam generator outputs purified water through a first heat exchanger, and a steam outlet and a condensed water outlet of the steam generator are connected with a steam compressor. And a steam outlet of the steam compressor is connected with a steam inlet of the steam reboiler. The problem of heat waste of purified water and condensed water can be solved, full utilization of medium-high temperature waste heat is achieved, the heat exchange process of raw material water is improved, the to-be-cooled temperature of the purified water is reduced, and energy loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and more specifically, to a wastewater stripping heat self-circulation system. Background Technology

[0002] The production processes in industries such as oil refining and coal chemical manufacturing generate acidic wastewater containing pollutants such as H2S (hydrogen sulfide) and NH3 (ammonia). Direct discharge of such wastewater would cause serious environmental pollution. Since H2S and NH3 are recyclable resources, their efficient separation and recovery have both environmental and economic value.

[0003] Currently, a heating unit is usually installed at the bottom of the stripping tower to provide a heat source for the stripping tower, so that H2S and NH3 in the wastewater are separated in gaseous form. High-concentration hydrogen sulfide is collected at the top of the tower, and the ammonia-rich gas phase is collected in the middle of the tower and purified by condensation to obtain liquid ammonia.

[0004] However, the existing process has the following drawbacks: On the one hand, the high-temperature purified water discharged from the stripping tower is directly cooled by the air cooler and then sent out or reused, resulting in a large amount of heat being released into the environment, causing energy waste, while increasing the operating load and power consumption of the air cooler, and increasing the energy consumption and operating cost of the unit; on the other hand, after the high-grade steam condensate of the stripping tower is flashed, some of the flash steam is cooled by the air cooler or vented, and the heat is not fully recovered and utilized.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a wastewater stripping heat self-circulation system to solve the problem of heat waste in purified water and condensate, realize the full utilization of medium and high temperature waste heat, and improve the heat exchange process of raw water to reduce the cooling temperature of purified water and reduce energy consumption.

[0007] According to one aspect of the present invention, a wastewater stripping heat self-circulation system is provided, comprising: a stripping tower; a first heat exchanger and a second heat exchanger, wherein a first flow path of the first heat exchanger receives acidic water and is connected to the hot feed inlet of the stripping tower via the first flow path of the second heat exchanger, a first gas outlet of the stripping tower outputs ammonia gas via the second flow path of the second heat exchanger, and a second gas outlet of the stripping tower outputs hydrogen sulfide; a steam reboiler, a steam generator, and a steam compressor, wherein the purified water outlet of the stripping tower is divided into two paths and connected to the purified water inlet of the steam reboiler and the steam generator, respectively. The purified water inlet of the steam reboiler is connected to the vapor-liquid two-phase inlet of the stripping tower. The liquid outlet of the steam reboiler is connected to the condensate inlet of the steam generator. The purified water outlet of the steam generator outputs purified water through the second flow path of the first heat exchanger. The steam outlet of the steam generator is connected to the steam inlet of the steam compressor. The condensate outlet of the steam generator is divided into two paths, one of which is connected to the condensate inlet of the steam compressor and the other outputs condensate. The steam outlet of the steam compressor is connected to the steam inlet of the steam reboiler.

[0008] In some embodiments, the wastewater stripping heat self-circulation system further includes: a balance tank, wherein the liquid outlet of the steam reboiler is connected to the liquid inlet of the balance tank, the liquid outlet of the balance tank is connected to the condensate inlet of the steam generator, and the gas outlet of the balance tank is connected to the steam inlet of the steam reboiler.

[0009] In some embodiments, the wastewater stripping heat self-circulation system further includes: a first liquid level control valve, wherein the liquid outlet of the balance tank is connected to the condensate inlet of the steam generator via the first liquid level control valve.

[0010] In some embodiments, the wastewater stripping heat self-circulation system further includes a condensate pump, wherein the condensate outlet of the steam generator is connected via the condensate pump to the condensate inlet and the output condensate of the steam compressor respectively.

[0011] In some embodiments, the wastewater stripping heat self-circulation system further includes: a second level control valve, wherein the condensate outlet of the steam generator is connected to the condensate pump via the second level control valve; and a first pressure control valve, wherein the condensate pump is connected to the condensate inlet of the steam compressor via the first pressure control valve.

[0012] In some embodiments, the wastewater stripping heat self-circulation system further includes: a first flow control valve, wherein the steam outlet of the steam compressor is connected to the steam inlet of the steam reboiler via the first flow control valve; a second pressure control valve, wherein the steam outlet of the steam generator is connected to the steam inlet of the steam compressor via the second pressure control valve; a second flow control valve, wherein externally supplied steam is input to the steam inlet of the steam reboiler via the second flow control valve; a third flow control valve, wherein acidic water is input to the first flow path of the first heat exchanger via the third flow control valve; and a temperature control valve, wherein the inlet of the temperature control valve is connected to the first flow path of the first heat exchanger and the two outlets are respectively connected to the first flow path of the second heat exchanger and the hot feed inlet of the stripping tower.

[0013] In some embodiments, the wastewater stripping heat self-circulation system further includes: a fourth flow control valve and a first cooler connected in series, wherein acidic water is input to the cold feed inlet of the stripping tower via the fourth flow control valve and the first cooler.

[0014] In some embodiments, the second gas outlet of the stripping tower is located at the top of the stripping tower, the purified water outlet of the stripping tower is located at the bottom of the stripping tower, and the cold feed inlet, the hot feed inlet, the first gas outlet and the vapor-liquid two-phase inlet are respectively located on the side of the stripping tower and their heights decrease sequentially.

[0015] In some embodiments, the wastewater stripping heat self-circulation system further includes: an air cooler and a second cooler connected in series, wherein the second flow path of the first heat exchanger outputs purified water through the air cooler and the second cooler.

[0016] In some embodiments, the operating temperature at the top of the stripping tower is in the range of 30°C to 50°C and the operating pressure is in the range of 0.4 MPa g to 0.5 MPa g; the operating temperature at the bottom of the stripping tower is in the range of 155°C to 165°C and the operating pressure is in the range of 0.45 MPa g to 0.55 MPa g; the ratio of the cold feed flow rate to the hot feed flow rate of the stripping tower is in the range of 0.05 to 0.2, wherein the cold feed temperature is in the range of 30°C to 40°C and the hot feed temperature is in the range of 110°C to 140°C; the steam saturation temperature at the steam inlet of the steam reboiler is greater than or equal to 170°C, and the steam production temperature at the steam outlet of the steam generator is in the range of 100°C to 140°C.

[0017] The wastewater stripping heat self-circulation system of the present invention, through the cooperation of a stripping tower, a first heat exchanger, a second heat exchanger, a steam reboiler, a steam generator, and a steam compressor, can achieve the following beneficial effects.

[0018] Constructing a waste heat steam generation system: Utilizing the waste heat from purified water and high-grade condensate, a steam generator and steam compressor work together to produce usable low-pressure steam, solving the problem of wasted heat from purified water and condensate, and achieving full utilization of medium- and high-temperature waste heat. The steam compressor pressurizes the waste heat steam and reuses it in the steam reboiler, which can also reduce the amount of external steam required and lower system operating costs.

[0019] Improve the feed water heat exchange process: Adjust the heat exchange sequence of the hot feed, and utilize the first and second heat exchangers to achieve cascaded heat utilization, reduce the cooling temperature of the purified water, and reduce energy consumption. After two stages of heat exchange, the temperature of the hot feed stabilizes, improving the temperature gradient and separation efficiency within the stripping tower.

[0020] The wastewater stripping heat self-circulation system of this invention reduces energy consumption and carbon emissions through waste heat recovery; the purified water is treated throughout the entire process and then sent out or reused after meeting the standards, avoiding environmental pollution caused by the direct discharge of acidic wastewater, and achieving multiple goals of environmental protection, resource recovery, and energy conservation.

[0021] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0023] Figure 1 This diagram illustrates the structure of the wastewater stripping heat self-circulation system in an embodiment of the present invention. Figure 2 This diagram illustrates the fluid flow during operation of the wastewater stripping heat self-circulation system in an embodiment of the present invention. Detailed Implementation

[0024] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to those described herein. Rather, these embodiments are provided to make the invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0025] The accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. The terms "first," "second," and similar words used in the specific description do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Furthermore, in the description of the invention, unless otherwise expressly specified and limited, the term "connection" should be interpreted broadly, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can refer to the internal connection of two elements.

[0026] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features of different embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0027] Reference Figure 1 As shown, the wastewater stripping heat self-circulation system provided in this embodiment of the invention includes: a stripping tower 100; a first heat exchanger 200 and a second heat exchanger 300, wherein a first flow path of the first heat exchanger 200 receives acidic water and connects to the hot feed inlet 110 of the stripping tower 100 via the first flow path of the second heat exchanger 300; a first gas outlet 120 of the stripping tower 100 outputs ammonia gas via the second flow path of the second heat exchanger 300; a second gas outlet 130 of the stripping tower 100 outputs hydrogen sulfide; a steam reboiler 400; a steam generator 500; and a steam compressor 600; wherein the purified water outlet 140 of the stripping tower 100 is divided into two branches and connected to the purified water inlet of the steam reboiler 400 respectively. The purified water inlet of the steam generator 500, the vapor-liquid two-phase outlet of the steam reboiler 400 is connected to the vapor-liquid two-phase inlet 150 of the stripping tower, the liquid outlet 410 of the steam reboiler 400 is connected to the condensate inlet 510 of the steam generator 500, the purified water outlet of the steam generator 500 outputs purified water through the second flow path of the first heat exchanger 200, the steam outlet of the steam generator 500 is connected to the steam inlet of the steam compressor 600, the condensate outlet of the steam generator 500 is divided into two paths, one of which is connected to the condensate inlet of the steam compressor 600 and the other path outputs condensate, and the steam outlet of the steam compressor 600 is connected to the steam inlet of the steam reboiler 400.

[0028] The stripping tower 100, as the core carrier for the separation and resource recovery of acidic wastewater, achieves efficient separation of H2S and NH3 through an internal gas-liquid mass and heat transfer mechanism. Specifically, the second gas outlet 130 of the stripping tower 100 outputs a high-concentration H2S gaseous component, while the first gas outlet 120 of the stripping tower 100 outputs an ammonia-rich gaseous component. Furthermore, the purified water outlet of the stripping tower 100 delivers high-temperature purified water in two separate paths: one providing heat exchange medium to the steam reboiler 400, and the other providing waste heat to the steam generator 500.

[0029] The first heat exchanger 200 adopts a dual-flow-path design. The first flow path of the first heat exchanger 200 receives upstream acidic water, providing initial preheating for the acidic water (hot feed). The second flow path of the first heat exchanger 200 receives purified water that has been cooled by the steam generator 500. Through counter-current heat exchange between the hot and cold fluids, the temperature of the acidic water is initially raised, reducing subsequent heating energy consumption. Simultaneously, waste heat in the purified water is recovered, lowering the temperature of the purified water to be cooled and reducing the cooling energy consumption of subsequent air coolers, etc. The first heat exchanger 200 establishes a heat transfer bridge between the preheating of the hot feed and the cooling of the purified water, achieving initial waste heat recovery.

[0030] The second heat exchanger 300 also adopts a dual-flow-path design. It receives the preheated acidic water (hot feed) from the first heat exchanger 200 and efficiently exchanges heat with the ammonia-rich gas phase component discharged from the stripping tower 100. This allows the hot feed side to absorb heat from the ammonia-rich gas phase, achieving a second-stage temperature increase and ensuring the hot feed temperature entering the stripping tower 100 remains stable within the process requirements, thus promoting gas-liquid separation efficiency within the tower. The ammonia-rich gas phase side, on the other hand, releases heat for cooling, providing preconditions for subsequent condensation and purification to obtain qualified liquid ammonia products, ensuring the purity of NH3 recovery. The second heat exchanger 300 achieves heat coupling between hot feed preheating and ammonia-rich gas phase cooling, improving the system's heat utilization rate.

[0031] The reboiler 400 receives high-temperature purified water from the stripping tower 100. Under the effect of thermosiphon self-balancing, it efficiently exchanges heat with steam, generating a vapor-liquid two-phase flow that returns to the stripping tower 100. This provides a continuous and stable heat source for the stripping process within the tower, ensuring the complete separation of H2S and NH3 from the wastewater. The high-temperature condensate produced after heat exchange in the reboiler 400 is transported to the steam generator 500 as its steam-producing water, achieving a secondary heat transfer from the reboiler 400 to the steam generator 500 and avoiding heat loss caused by direct discharge or inefficient use of condensate.

[0032] The steam generator 500, as the core equipment for waste heat recovery, simultaneously receives two high-temperature fluids: purified water from the stripping tower 100 and condensate from the steam reboiler 400. Through the thermal coupling effect of these two fluids, it efficiently produces low-pressure clean steam, solving the problem of direct discharge of waste heat from purified water and high-grade condensate. The purified water, cooled by heat exchange in the steam generator 500, is then transported to the first heat exchanger 200 to further explore the potential for waste heat recovery. The condensate outlet of the steam generator 500 is designed with two paths: one to provide condensate for cooling the steam compressor 600, and the other to send excess condensate externally, preventing condensate accumulation and achieving reasonable recycling of condensate, forming a closed-loop chain for waste heat recovery.

[0033] The steam compressor 600 receives low-pressure clean steam from the steam generator 500 and boosts the steam pressure to a set range through a pressurization mechanism, ensuring the steam temperature meets the saturation temperature requirements of the steam reboiler 400. The condensate inlet of the steam compressor 600 receives condensate from the steam generator 500. Through heat exchange between the condensate and the pressurized steam, the steam temperature is precisely controlled, preventing temperature fluctuations from affecting the heat exchange efficiency of the steam reboiler 400. The steam, pressurized and cooled by the steam compressor 600, is then delivered to the steam reboiler 400, enabling the reuse of waste heat for steam generation and reducing the consumption of externally supplied steam.

[0034] Therefore, the wastewater stripping heat self-circulation system of the present invention, through the cooperation of the stripping tower 100, the first heat exchanger 200, the second heat exchanger 300, the steam reboiler 400, the steam generator 500 and the steam compressor 600, can achieve the following beneficial effects.

[0035] Constructing a waste heat steam generation system: Utilizing the waste heat from purified water and high-grade condensate, a steam generator 500 and a steam compressor 600 work together to produce usable low-pressure steam, solving the problem of wasted heat from purified water and condensate, and achieving full utilization of medium- and high-temperature waste heat. The steam compressor 600 pressurizes the waste heat steam and reuses it in the steam reboiler 400, which also reduces the amount of external steam required and lowers system operating costs.

[0036] Improved feed water heat exchange process: Adjust the heat exchange sequence of the hot feed, and utilize the first heat exchanger 200 and the second heat exchanger 300 to achieve cascaded utilization of heat, reduce the cooling temperature of the purified water, and reduce energy consumption. After two stages of heat exchange, the temperature of the hot feed stabilizes, improving the temperature gradient and separation effect within the stripping tower 100.

[0037] Furthermore, this invention can also achieve optimal energy consumption of the unit by intelligently controlling multiple process parameters in conjunction with algorithms, while ensuring that all indicators of the stripping tower 100 meet the requirements.

[0038] The wastewater stripping heat self-circulation system of this invention reduces energy consumption and carbon emissions through waste heat recovery; the purified water is treated throughout the entire process and then sent out or reused after meeting the standards, avoiding environmental pollution caused by the direct discharge of acidic wastewater, and achieving multiple goals of environmental protection, resource recovery, and energy conservation.

[0039] In some embodiments, the wastewater stripping heat self-circulation system further includes: a balance tank 700, the liquid outlet 410 of the steam reboiler 400 being connected to the liquid inlet of the balance tank 700, the liquid outlet of the balance tank 700 being connected to the condensate inlet 510 of the steam generator 500, and the gas outlet of the balance tank 700 being connected to the steam inlet 420 of the steam reboiler 400.

[0040] The balance tank 700 receives and stores condensate generated by the reboiler 400, acting as a buffer and pressure stabilizer to prevent fluctuations in condensate supply flow and pressure. This ensures the stability of the feed to the steam generator 500 and prevents unstable steam production from the generator due to condensate fluctuations. Consequently, it guarantees the quality of the input steam to the steam compressor 600 and the stability of the heat source for the reboiler 400, improving the overall system reliability. The steam generated in the balance tank 700 is reused in the reboiler 400 to further recover waste heat from the condensate, reducing the amount of external steam required and heat waste, thus further enhancing the system's energy-saving effect and economic benefits.

[0041] In some embodiments, the wastewater stripping heat self-circulation system further includes: a first liquid level control valve K1, wherein the liquid outlet of the balance tank 700 is connected to the condensate inlet 510 of the steam generator 500 via the first liquid level control valve K1.

[0042] The first level control valve K1 achieves precise and quantitative delivery of condensate to the steam generator 500 through level control, preventing unstable steam production and pressure due to feed fluctuations. The first level control valve K1 can precisely control the condensate flow rate from the balance tank 700 to the steam generator 500. By monitoring the condensate level in the balance tank 700 in real time, it automatically adjusts the valve opening to ensure the condensate feed flow rate remains stable within the set range, guaranteeing the safe and stable operation and stable steam production of the steam generator 500, and ensuring that the pressure, temperature, and flow rate of the produced steam meet the feed requirements of the steam compressor 600.

[0043] In some embodiments, the wastewater stripping heat self-circulation system further includes: a condensate pump 800, wherein the condensate outlet of the steam generator 500 is connected via the condensate pump 800 to the condensate inlet and the output condensate of the steam compressor 600 respectively.

[0044] The condensate pump 800 receives condensate from the steam generator 500 after steam production and increases the condensate pressure to a set value through pressurization. One path provides a cooling medium to the steam compressor 600. Through heat exchange between the condensate and the pressurized steam, the temperature of the steam produced by the steam compressor 600 is effectively controlled, ensuring that the temperature of the steam entering the steam reboiler 400 remains stable within a reasonable range. The other path sends the condensate out, allowing for the rational use of the condensate produced by the steam generator 500, avoiding condensate accumulation. At the same time, the temperature of the discharged condensate has been reduced, minimizing heat waste and meeting energy-saving requirements.

[0045] In some embodiments, the wastewater stripping heat self-circulation system further includes: a second level control valve K2, through which the condensate outlet of the steam generator 500 is connected to the condensate pump 800; and a first pressure control valve K3, through which the condensate pump 800 is connected to the condensate inlet of the steam compressor 600.

[0046] The second level control valve K2 can monitor the condensate level in the steam generator 500 in real time. By adjusting the valve opening, it controls the condensate discharge flow rate, ensuring that the condensate level in the steam generator 500 is maintained within a reasonable range, thus guaranteeing the safe and stable operation of the steam generator 500 and continuous and efficient steam production.

[0047] The first pressure control valve K3 can precisely control the condensate pressure entering the steam compressor 600, so that the condensate pressure matches the operating requirements of the steam compressor 600, ensuring that the condensate can efficiently cool the pressurized steam, ensuring that the outlet steam temperature of the steam compressor 600 is stable within the set range, providing a qualified heat source for the steam reboiler 400, and preventing abnormal pressure from damaging the steam compressor 600.

[0048] In some embodiments, the wastewater stripping heat self-circulation system further includes: a first flow control valve K4, wherein the steam outlet of the steam compressor 600 is connected to the steam inlet 420 of the steam reboiler 400 via the first flow control valve K4.

[0049] The first flow control valve K4 can precisely control the steam flow rate delivered by the steam compressor 600 to the steam reboiler 400. Based on the heat source requirements of the steam reboiler 400 and the operating conditions of the stripping tower 100, the valve opening is adjusted in real time to ensure that the steam supply matches the heat exchange requirements of the steam reboiler 400 and to ensure the normal operation of the stripping tower 100.

[0050] In some embodiments, the wastewater stripping heat self-circulation system further includes: a second pressure control valve K5, wherein the steam outlet of the steam generator 500 is connected to the steam inlet of the steam compressor 600 via the second pressure control valve K5.

[0051] The second pressure control valve K5 can control the pressure of the steam output from the steam generator 500, so that the steam pressure is stabilized within the feed requirement range of the steam compressor 600, avoiding abnormal operating load of the steam compressor 600 due to pressure fluctuations, ensuring the pressurization effect and operating safety of the steam compressor 600, and ensuring that the pressurized steam can meet the pressure requirements of the steam reboiler 400.

[0052] In some embodiments, the wastewater stripping heat self-circulation system further includes: a second flow control valve K6, wherein externally supplied steam is input into the steam inlet 420 of the steam reboiler 400 via the second flow control valve K6.

[0053] The second flow control valve K6 is used to control the input flow rate of externally supplied steam to the steam reboiler 400. It can adjust the externally supplied steam flow rate in real time according to the steam supply of the steam compressor 600 and the total heat source demand of the steam reboiler 400, so as to achieve a reasonable match between externally supplied steam and waste heat steam generation. Under the premise of meeting the heat source demand of the steam reboiler 400, the amount of externally supplied steam is minimized, thereby reducing operating costs.

[0054] In some embodiments, the wastewater stripping heat self-circulation system further includes: a third flow control valve K7, wherein acidic water is input into the first flow path of the first heat exchanger 200 via the third flow control valve K7.

[0055] The third flow control valve K7 can precisely control the flow rate of acidic water (hot feed) entering the first heat exchanger 200. According to the processing scale and operating conditions of the stripping tower 100, the hot feed flow rate is adjusted to ensure that the ratio of hot feed to cold feed is maintained within a reasonable range, optimize the temperature gradient and separation effect in the tower, and avoid instability in the tower conditions caused by fluctuations in the hot feed flow rate.

[0056] In some embodiments, the wastewater stripping heat self-circulation system further includes a temperature control valve K8, the inlet of which is connected to the first flow path of the first heat exchanger 200 and the two outlets are respectively connected to the first flow path of the second heat exchanger 300 and the hot feed inlet 110 of the stripping tower.

[0057] Temperature control valve K8 can adjust the ratio of hot feed entering the second heat exchanger 300 to hot feed directly entering the stripping tower 100 based on the temperature detection results of the hot feed, so as to ensure that the temperature of the hot feed entering the stripping tower 100 is stable within a reasonable range, and to ensure the stability and separation effect of the stripping process in the tower.

[0058] In some embodiments, the wastewater stripping heat self-circulation system further includes: a fourth flow control valve K9 and a first cooler 910 connected in series, wherein acidic water is input into the cold feed inlet 160 of the stripping tower via the fourth flow control valve K9 and the first cooler 910.

[0059] The fourth flow control valve K9 is installed on the pipeline of the cold feed inlet 160 of the acid water input stripping tower 100. It can precisely control the cold feed flow rate. According to the hot feed flow rate and the operating conditions of the stripping tower 100, the cold feed flow rate is adjusted to ensure that the ratio of cold feed to hot feed is maintained within a reasonable range. The tower top temperature is controlled by adjusting the cold feed flow rate to ensure the purity of H2S at the top of the tower and avoid abnormal tower top temperature caused by fluctuations in the cold feed flow rate.

[0060] The first cooler 910 is used to cool the cold feed entering the stripping tower 100, so that the temperature of the cold feed is stabilized within a reasonable range. Through the cooling effect of the cold feed, the temperature control at the top of the tower is further optimized, ensuring that the NH3 content in the gas phase at the top of the tower meets the requirements, improving the separation purity of H2S, and at the same time providing a guarantee for the formation of temperature gradient in the tower, promoting the efficient separation of H2S and NH3.

[0061] In some embodiments, the second gas outlet 130 of the stripping tower 100 is located at the top of the stripping tower 100, the purified water outlet of the stripping tower 100 is located at the bottom of the stripping tower 100, and the cold feed inlet 160, the hot feed inlet 110, the first gas outlet 120 and the vapor-liquid two-phase inlet 150 are located on the side of the stripping tower 100 and their heights decrease sequentially.

[0062] The cold feed enters from a higher position, contacting the rising gas phase inside the tower, thus cooling the gas phase at the top and controlling the top temperature. The hot feed enters from below the cold feed, ensuring full contact with the gas and liquid phases inside the tower, promoting the separation of H2S and NH3. The ammonia-rich gas outlet is located below the hot feed, corresponding to the NH3-rich area inside the tower, allowing for efficient extraction of the ammonia-rich gas phase component and improving the liquid ammonia product yield. The vapor-liquid two-phase inlet is located at a lower position, ensuring full contact with the purified water at the bottom of the tower, providing a continuous and stable heat source to maintain the bottom temperature and ensure the efficient operation of the entire stripping process. The top outlet outputs hydrogen sulfide, and the bottom outlet discharges purified water, achieving precise positioning for pollutant separation and resource recovery.

[0063] In some embodiments, the wastewater stripping heat self-circulation system further includes: an air cooler 920 and a second cooler 930 connected in series, wherein the second flow path of the first heat exchanger 200 outputs purified water through the air cooler 920 and the second cooler 930.

[0064] The air cooler 920 receives purified water that has been cooled by the first heat exchanger 200 and further reduces the temperature of the purified water through air cooling, reducing residual heat in the purified water and preventing problems during external delivery or reuse due to excessively high purified water temperature. Compared to directly sending purified water into the air cooler 920, the temperature of the purified water is significantly reduced after pretreatment by the steam generator 500 and the first heat exchanger 200 in this invention, which can greatly reduce the operating load and power consumption of the air cooler 920.

[0065] The second cooler 930 further cools the purified water after it has been cooled by the air cooler 920, ensuring that the temperature of the purified water meets the requirements for external delivery or reuse, avoiding the impact of the subsequent treatment or reuse process due to the temperature of the purified water not meeting the standard, and ensuring the integrity of the entire sewage treatment process.

[0066] In some embodiments, the operating temperature at the top of the stripping tower 100 is within the range of 30°C to 50°C, specifically 40°C, and can be adjusted according to production requirements; the operating pressure at the top of the stripping tower 100 is within the range of 0.4 MPa g to 0.5 MPa g, specifically 0.45 MPa g, and can be adjusted according to production requirements. By designing the operating temperature and pressure at the top of the stripping tower 100, the purity of H2S in the top gas phase can be ensured. Through reasonable temperature and pressure control, the content of NH3 in the top gas phase is suppressed, ensuring efficient recovery of H2S resources.

[0067] In some embodiments, the operating temperature at the bottom of the stripping tower 100 is within the range of 155°C to 165°C, specifically 160°C, which can be adjusted according to production requirements; the operating pressure at the bottom of the stripping tower 100 is within the range of 0.45 MPa g to 0.55 MPa g, specifically 0.5 MPa g, which can be adjusted according to production requirements. The design of the operating temperature and pressure at the bottom of the stripping tower 100 provides sufficient heat for the stripping process within the tower, promoting the full separation of H2S and NH3 in the wastewater, ensuring that the purified water discharged from the bottom of the tower meets the standards, and simultaneously providing a sufficient heat base for the waste heat recovery of the purified water and high-grade condensate at the bottom of the tower, ensuring that the steam generator 500 can stably produce low-pressure steam.

[0068] In some embodiments, the ratio of cold feed flow rate to hot feed flow rate of stripping tower 100 is in the range of 0.05 to 0.2, specifically 0.1, and can be adjusted according to production requirements; the cold feed temperature is in the range of 30°C to 40°C, specifically 35°C, and can be adjusted according to production requirements; the hot feed temperature is in the range of 110°C to 140°C, specifically 125°C, and can be adjusted according to production requirements. Through the synergistic effect of cold and hot feed parameters, the temperature gradient within the tower is optimized, resulting in a reasonable temperature distribution in different regions of the tower. This promotes efficient gas-liquid mass and heat transfer processes, avoids fluctuations in tower operating conditions due to improper cold / hot feed ratios or temperatures, ensures stable separation efficiency and product yield, and reduces energy waste.

[0069] In some embodiments, the steam saturation temperature at the steam inlet of the reboiler 400 is greater than or equal to 170°C, ensuring that the reboiler 400 can provide sufficient heat source for the stripping tower 100, maintain the set temperature at the bottom of the tower, and ensure the continuous and efficient operation of the stripping process. At the same time, it matches the pressurization effect of the steam compressor 600, ensuring that the waste heat steam production can meet the heat source requirements of the reboiler 400.

[0070] In some embodiments, the steam outlet temperature of the steam generator 500 is in the range of 100°C to 140°C, specifically 130°C. The actual temperature can be adjusted according to production requirements to ensure that the low-pressure steam produced by the steam generator 500 has sufficient heat. After being pressurized by the steam compressor 600, it can meet the usage requirements of the steam reboiler 400. At the same time, it can fully recover the waste heat of purified water and high-grade condensate, avoid heat waste, and improve the waste heat utilization efficiency.

[0071] In a specific example, refer to Figure 2 As shown, the working process of the wastewater stripping heat self-circulation system includes: Acidic water, i.e., sulfur-containing wastewater S-1, comes from upstream and enters the stripping tower 100 in two streams. One stream is a cold feed, which, after being regulated by the fourth flow control valve K9 and temperature-controlled by the first cooler 910, enters the stripping tower 100 as cold feed S-2 to control the top temperature of the tower within a set range. The other stream is a hot feed, whose flow rate is controlled by the third flow control valve K7 and after sufficient heat exchange with the purified water in the first heat exchanger 200 to become preliminary hot feed S-3; then, after the flow rate is regulated by the temperature control valve K8 and the second heat exchanger 300 achieves the second stage of heat exchange, the final hot feed S-4 enters the stripping tower 100.

[0072] The purified water drawn from the bottom of the stripping tower 100 is divided into two streams. One stream, as reboiler feed S-5, enters the steam reboiler 400. Under the thermosiphon self-balancing effect, it undergoes efficient heat exchange with steam to obtain a vapor-liquid two-phase mixture S-6, which returns to the lower region of the tower, maintaining the bottom temperature within the set range. The other stream, as steam generator feed S-7, enters the steam generator 500. The high-temperature purified water releases heat in the steam generator 500, reducing its temperature to the set range. After cooling, the purified water S-8 enters the first heat exchanger 200 for further cooling. Finally, it is cooled by the air cooler 920 and the second cooler 930 to form purified water at the target temperature S-10 before exiting the device. Ammonium sulfide gas S-20 is output from the top of the stripping tower 100, and ammonia-rich gas phase component S-21 is output from the side of the stripping tower 100. After heat exchange in the second heat exchanger 300, ammonia gas S-22 is output.

[0073] The feed steam S-11 to the reboiler 400 is supplied by two sources: one from the steam generated by the steam compressor 600 (S-12), and the other from external makeup steam (S-13). The steam generated S-12 primarily utilizes the condensate S-14 from the reboiler 400. After treatment in the balance tank 700 and level control by the first level control valve K1, it enters the steam generator 500, producing clean steam S-15 within a set pressure range. This clean steam S-15 is then processed by the second pressure control valve K5 into low-pressure steam S-16, which is then pressurized to the set pressure in the steam compressor 600. The steam temperature is then controlled by temperature-controlled condensate S-17, resulting in steam generated S-12 entering the reboiler 400 after being regulated by the first flow control valve K4. This achieves efficient utilization of waste heat from the purified water and effectively reduces the amount of external makeup steam S-13 required. The external makeup steam S-13 enters the reboiler 400 after being regulated by the second flow control valve K6. The steam condensate S-18 from the steam generator 500 is regulated by the second liquid level control valve K2 and pressurized by the condensate pump 800. Part of it is regulated by the first pressure control valve K3 to form temperature-controlled condensate S-17, which returns to the steam compressor 600 to cool the steam. The other part is discharged as condensate S-19.

[0074] The present invention can also monitor the indicators of the stripping tower 100 through an intelligent control system, such as the top temperature, bottom temperature, raw water quality and purified water quality, and automatically control parameters such as the raw material cold-heat ratio, the amount of steam generated by the heat integration waste heat and the external steam flow rate through intelligent algorithms, so as to achieve optimal energy consumption of the stripping tower 100 when the indicators are qualified.

[0075] To facilitate understanding of the present invention, the following examples are provided. Those skilled in the art should understand that the following examples are merely illustrative and should not be considered as specific limitations of the invention.

[0076] Case 1: In this case, the wastewater stripping treatment capacity is 75t / h, with an annual operating time of 8000h. The energy prices are: steam price 180 yuan / t, electricity price 0.6 yuan / kW; the energy consumption conversion factor is 1.0MPag: steam: 76, electricity: 0.23, as detailed below.

[0077] Table 1 - Changes before and after optimization in Case 1:

[0078] As shown in the data from Case 1, after the implementation of this invention, the temperature of purified water entering the air cooler decreased from 121.7℃ to 96.1℃, the condensate temperature decreased from 165℃ to 130℃, the external steam supply decreased from 15.04t / h to 10.54t / h, a reduction of 4.5t / h, the additional power consumption was 383kW, and the energy consumption (converted to standard coal equivalent) decreased from 13063.3t standard coal / a to 10160.2t standard coal / a, a reduction of 2903.1t standard coal / a, with an energy saving rate of approximately 22.2%; the operating cost decreased from 2707.2 yuan / h to 2126.7 yuan / h, a reduction of 580.5 yuan / h, with an operating cost reduction rate of 21.4%.

[0079] Case 2: In this case, the wastewater stripping treatment capacity is 125t / h, with an annual operating time of 8000h. The energy prices are: steam price 150 yuan / t, electricity price 0.6 yuan / kW; the energy consumption conversion factor is 1.0MPag: steam: 76, electricity: 0.23, as detailed below.

[0080] Table 2 - Changes before and after optimization in Case 2:

[0081] As shown in Case 2, after the implementation of this invention, the temperature of purified water entering the air cooler decreased from 122.1℃ to 96.3℃, the condensate temperature decreased from 165℃ to 130℃, the external steam supply decreased from 25.18t / h to 17.38t / h, a reduction of 7.8t / h, the additional power consumption was 663kW, and the energy consumption (converted to standard coal equivalent) decreased from 21870.6t standard coal / a to 16838.5t standard coal / a, a reduction of 5032.1t standard coal / a, with an energy saving rate of approximately 23%; the operating cost decreased from 3777 yuan / h to 3004.8 yuan / h, a reduction of 772.2 yuan / h, with an operating cost reduction rate of 20.4%.

[0082] Finally, it should be noted that the above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention and should not be construed as limiting the specific implementation of the invention to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A wastewater stripping and heat self-circulation system, characterized in that, include: Stripping tower; A first heat exchanger and a second heat exchanger, wherein the first flow path of the first heat exchanger receives acidic water and connects to the hot feed inlet of the stripping tower via the first flow path of the second heat exchanger, and the first gas outlet of the stripping tower outputs ammonia gas via the second flow path of the second heat exchanger, and the second gas outlet of the stripping tower outputs hydrogen sulfide. The system comprises a reboiler, a steam generator, and a steam compressor. The purified water outlet of the stripping tower is connected in two separate paths to the purified water inlet of the reboiler and the purified water inlet of the steam generator. The vapor-liquid two-phase outlet of the reboiler is connected to the vapor-liquid two-phase inlet of the stripping tower. The liquid outlet of the reboiler is connected to the condensate inlet of the steam generator. The purified water outlet of the steam generator outputs purified water through the second flow path of the first heat exchanger. The steam outlet of the steam generator is connected to the steam inlet of the steam compressor. The condensate outlet of the steam generator is divided into two paths, one of which is connected to the condensate inlet of the steam compressor and the other outputs condensate. The steam outlet of the steam compressor is connected to the steam inlet of the reboiler.

2. The wastewater stripping heat self-circulation system as described in claim 1, characterized in that, Also includes: The balance tank has its liquid outlet connected to the liquid inlet of the steam reboiler, its liquid outlet connected to the condensate inlet of the steam generator, and its gas outlet connected to the steam inlet of the steam reboiler.

3. The wastewater stripping and heat self-circulation system as described in claim 2, characterized in that, Also includes: The first liquid level control valve connects the liquid outlet of the balance tank to the condensate inlet of the steam generator.

4. The wastewater stripping heat self-circulation system as described in claim 1, characterized in that, Also includes: The condensate pump connects the condensate outlet of the steam generator to the condensate inlet and the condensate outlet of the steam compressor via two separate paths.

5. The wastewater stripping heat self-circulation system as described in claim 4, characterized in that, Also includes: The second liquid level control valve connects the condensate outlet of the steam generator to the condensate pump. A first pressure control valve is provided, through which the condensate pump is connected to the condensate inlet of the steam compressor.

6. The wastewater stripping heat self-circulation system as described in claim 1, characterized in that, Also includes: The first flow control valve connects the steam outlet of the steam compressor to the steam inlet of the steam reboiler. The second pressure control valve connects the steam outlet of the steam generator to the steam inlet of the steam compressor. The second flow control valve is used to input externally supplied steam into the steam inlet of the steam reboiler. A third flow control valve is used to input acidic water into the first flow path of the first heat exchanger; A temperature control valve, the inlet of which is connected to the first flow path of the first heat exchanger and the two outlets of which are respectively connected to the first flow path of the second heat exchanger and the hot feed inlet of the stripping tower.

7. The wastewater stripping heat self-circulation system as described in claim 1, characterized in that, Also includes: A fourth flow control valve and a first cooler are connected in series, wherein acidic water is introduced into the cold feed inlet of the stripping tower via the fourth flow control valve and the first cooler.

8. The wastewater stripping heat self-circulation system as described in claim 7, characterized in that, The second gas outlet of the stripping tower is located at the top of the stripping tower, the purified water outlet of the stripping tower is located at the bottom of the stripping tower, and the cold feed inlet, the hot feed inlet, the first gas outlet and the vapor-liquid two-phase inlet are located on the side of the stripping tower and their heights decrease sequentially.

9. The wastewater stripping and heat self-circulation system as described in claim 1, characterized in that, Also includes: The air cooler and the second cooler are connected in series, and the second flow path of the first heat exchanger outputs purified water through the air cooler and the second cooler.

10. The wastewater stripping heat self-circulation system as described in any one of claims 1 to 9, characterized in that, The operating temperature at the top of the stripping tower is in the range of 30°C to 50°C and the operating pressure is in the range of 0.4 MPa to 0.5 MPa, while the operating temperature at the bottom of the stripping tower is in the range of 155°C to 165°C and the operating pressure is in the range of 0.45 MPa to 0.55 MPa. The ratio of cold feed flow rate to hot feed flow rate of the stripping tower is in the range of 0.05 to 0.2, wherein the cold feed temperature is in the range of 30°C to 40°C and the hot feed temperature is in the range of 110°C to 140°C. The steam saturation temperature at the steam inlet of the steam reboiler is greater than or equal to 170°C, and the steam production temperature at the steam outlet of the steam generator is in the range of 100°C to 140°C.

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