Process and special equipment for reducing temperature of turbid circulating water by using LNG vaporization cold energy

Abstract

This invention discloses a process and specialized equipment for reducing the temperature of turbid circulating water using the cold energy of LNG vaporization. It consists of three parts: a closed circulating water LNG vaporizer, an LNG vaporization pipeline system, and a turbid circulating water supply and return system. The process involves heat exchange between liquid LNG and turbid circulating water, recovering and utilizing the cold energy released during the LNG vaporization process. This solves the problem that cooling towers used for hot rolling and heat treatment turbid circulating water cannot meet the on-site water temperature requirements during hot and humid summer weather. It improves the cooling effect of equipment and molds, enhances product quality, and simultaneously achieves cold energy recovery and utilization, reducing energy waste.

Description

Technical Field

[0001] This invention relates to the field of metallurgical auxiliary equipment technology. Specifically, it is a process and equipment for reducing the temperature of turbid circulating water by utilizing the cold energy of LNG vaporization. It is applied to situations where a large amount of cold energy released during the vaporization of liquid LNG is not recovered and utilized, and the temperature of the turbid circulating water cannot meet the requirements of on-site use by using a cooling tower. Background Technology

[0002] Currently, most metallurgical enterprises use liquefied LNG vaporized natural gas as fuel for heating raw materials in hot rolling and heat treatment, and cooling towers are used for cooling the circulating water in equipment and molds, as well as for water quenching in heat treatment. However, this approach has the following shortcomings: 1. The vaporization process of liquefied LNG can release a large amount of cold energy. Theoretically, 1 ton of LNG can release 830,000 * 10J of cold energy after vaporization, which is equivalent to 231 kWh of electrical energy. This cold energy can cool 1 ton of water by 197°C and can make 1.8 tons of ice. The vaporization of liquefied LNG uses an ambient air vaporizer. The liquefied LNG exchanges heat with the outside air, and the cold energy is directly released into the air without being collected and utilized, resulting in a large waste. 2. With the improvement of production capacity and efficiency, and the continuous improvement of processes, metallurgical enterprises have put forward new requirements for the supply water temperature of hot rolling and heat treatment circulating water: hot rolling circulating water temperature ≤34℃; heat treatment circulating water temperature ≤32℃, and special products require ≤28℃; the hot rolling circulating water system uses cooling towers for cooling, which can normally meet the ≤34℃ requirement, but due to the influence of local wet-bulb temperature, there is an overheating phenomenon in the hot and humid summer weather, which affects the rolling performance and the cooling effect of the tooling. The heat treatment turbid circulating water system uses a cooling tower for cooling. Due to the influence of local wet-bulb temperature, the temperature of the turbid circulating water in summer can reach 33-34℃, which makes it difficult to meet the on-site water temperature requirement of ≤32℃. In the extreme hot weather of July and August, the temperature exceeds 35℃ and the water temperature is unstable, resulting in abnormal fluctuations in the heat treatment performance. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of the prior art by providing a process for reducing the temperature of turbid circulating water using the cooling energy of LNG vaporization.

[0004] Another objective of this invention is to provide a device that utilizes the cooling energy of LNG vaporization to reduce the temperature of turbid circulating water.

[0005] The technical solution provided by this invention is a process for reducing the temperature of turbid circulating water using the cooling energy of LNG vaporization. Its unique feature is that it includes the following process steps: a includes a closed circulating water LNG vaporizer, with the liquid LNG inlet and NG outlet connected in parallel to the LNG storage tank liquid outlet manifold and vaporizer gas outlet manifold of the ambient temperature LNG vaporizer, respectively, and can be switched with the ambient temperature LNG vaporizer and serve as backups for each other; b. A hot rolling turbid circulating cold water pool is equipped with a hot rolling water supply pump set, and a heat treatment turbid circulating cold water pool is equipped with a heat treatment water supply pump set. A water supply pipeline and a return pipeline are laid from the turbid circulating cold water pool to the circulating water LNG vaporizer. The water supply pipeline is connected to the inlet of the circulating water LNG vaporizer, and the return pipeline is connected to the outlet of the circulating water LNG vaporizer. Liquid LNG flows through the evaporation pipe of the closed circulating water LNG vaporizer and becomes gas NG. At the same time, the cold energy released by the vaporization process of liquid LNG is replaced by the shell circulating water of the circulating water LNG vaporizer through the evaporation pipe, thereby reducing the temperature of the circulating water in the return pipeline. The water temperature of the hot rolling turbid circulating cold water pool and the heat treatment turbid circulating cold water pool is reduced through continuous water circulation in the water supply and return pipelines. c. The temperature, flow rate, and pressure detection data of the turbid circulating water supply and return pipelines are uploaded to the HMI screen respectively. When the circulating water at the outlet of the circulating water LNG vaporizer shows a low temperature alarm, the pneumatic emergency shut-off valve of the vaporizer LNG inlet control valve group of the interlock control valve group is activated, cutting off the vaporizer LNG inlet pipeline. The vaporizer NG outlet pipeline is equipped with a vaporizer NG outlet temperature sensor, which is linked with the pneumatic emergency shut-off valve. When the NG outlet temperature is lower than 8°C, an alarm is triggered. When the NG outlet temperature is lower than 3°C, the pneumatic emergency shut-off valves of the vaporizer LNG inlet control valve group and the vaporizer NG outlet control valve group are activated, cutting off the vaporizer LNG inlet pipeline and the vaporizer NG outlet pipeline.

[0006] The present invention is a special device for reducing the temperature of turbid circulating water by utilizing the cold energy of LNG vaporization. Its special feature is that it consists of three parts: a closed circulating water LNG vaporizer, an LNG vaporization pipeline system, and a turbid circulating water supply and return system. The enclosed circulating water LNG vaporizer is the core of the entire equipment, consisting of a support, a cylinder, an insulation layer, evaporation pipes, and lifting lugs. The evaporation pipes are placed inside the cylinder. The shell side is between the cylinder and the evaporation pipes. The bottom of the cylinder has an inlet and a drain valve, and the top has an outlet. The tube side is inside the evaporation pipes. The lower part of the evaporation pipes has a liquid LNG inlet, and the upper part has an LNG outlet. The top of the cylinder has an observation hole, and the lower part has a manhole. The middle of the cylinder is equipped with a vent valve, a full-opening safety valve, a thermometer, and a pressure gauge, all of which are connected to the shell side. The outer surface of the cylinder is covered with an insulation layer. The top of the cylinder has lifting lugs, and the bottom of the cylinder has a support. The LNG vaporization pipeline system includes an LNG inlet pipeline for the vaporizer, an NG outlet pipeline for the vaporizer, an LNG inlet control valve assembly for the vaporizer, an NG outlet control valve assembly for the vaporizer, and an NG outlet temperature sensor for the vaporizer. The LNG inlet pipeline and the NG outlet pipeline are made of 06Cr19Ni10 material. The LNG inlet pipeline connects to the LNG storage tank outlet manifold and is connected to the liquid LNG inlet of the circulating water LNG vaporizer via the LNG inlet control valve assembly. The vaporizer LNG inlet control valve group is equipped with two cryogenic shut-off valves, one pneumatic emergency shut-off valve, and one ultra-low temperature full-open safety valve; the vaporizer NG outlet pipeline is connected to the NG outlet of the circulating water LNG vaporizer, and is connected to the vaporizer outlet manifold through the vaporizer NG outlet control valve group, which is equipped with two cryogenic shut-off valves, two ultra-low temperature full-open safety valves, and one pneumatic emergency shut-off valve; the vaporizer NG outlet pipeline is equipped with a vaporizer NG outlet temperature sensor. The turbid circulating water supply and return system includes a hot rolling turbid circulating cold water tank, a heat treatment turbid circulating cold water tank, water supply pipelines, return water pipelines, hot rolling water supply pump sets, heat treatment water supply pump sets, hot rolling vacuum pump sets, heat treatment vacuum pump sets, hot rolling return water valve sets, heat treatment return water valve sets, vaporizer inlet butterfly valves, and vaporizer outlet butterfly valves. The hot rolling turbid circulating cold water tank is equipped with one set of hot rolling water supply pump sets and one set of hot rolling return water valve sets, and the heat treatment turbid circulating cold water tank is equipped with one set of heat treatment water supply pump sets and one set of heat treatment return water valve sets. A pipeline is laid from the turbid circulating cold water tank to the circulating water LNG vaporizer. The system includes a water supply pipeline and a return pipeline. The water supply pipeline is connected to the inlet of the circulating water LNG vaporizer via a butterfly valve at the vaporizer inlet, and the return pipeline is connected to the outlet of the circulating water LNG vaporizer via a butterfly valve at the vaporizer outlet. Two sets of water supply pump groups and return valve groups are interchangeable and serve as backups for each other, sharing the same water supply and return pipelines. The hot rolling vacuum pump group is installed at a high position on the inlet pipeline between the hot rolling circulating cold water pool and the hot rolling water supply pump group. The heat treatment vacuum pump group is also installed at a high position on the inlet pipeline between the heat treatment circulating cold water pool and the heat treatment water supply pump group. A cold water tank-side drain valve is installed on both the supply and return water pipelines on one side of the cold water tank, and a vaporizer-side drain valve is installed on both the supply and return water pipelines on the other side of the vaporizer. The drain valves are located at the bottom of the pipelines. A vent valve is installed in the middle of both the supply and return water pipelines, located at the top of the pipelines. A cold water tank-side temperature transmitter is installed on both the supply and return water pipelines on the cold water tank side for detecting the circulating water supply temperature. A vaporizer-side temperature transmitter and a vaporizer-side pressure transmitter are installed on both the supply and return water pipelines on the vaporizer side for detecting the circulating water return temperature and pressure. A flow meter is installed on the supply water pipeline on the vaporizer side for detecting the circulating water flow rate.

[0007] Furthermore, the hot rolling water supply pump group and the heat treatment water supply pump group draw water from the middle part of the hot rolling turbid circulating cold water pool and the heat treatment turbid circulating cold water pool, respectively, and filter screens are installed at the water inlets of the hot rolling water supply pump group and the heat treatment water supply pump group.

[0008] Furthermore, each water supply pump set is sequentially equipped with an inlet butterfly valve, a drain valve, a Y-type filter, an inlet flexible joint, an inlet reducer, an inlet pressure gauge, a circulating water pump, an outlet pressure gauge, an outlet reducer, an outlet flexible joint, a check valve, an electric regulating valve, and an outlet butterfly valve; the flow rate of the water supply pump set is adjusted by the electric regulating valve.

[0009] Furthermore, each vacuum pump set is equipped with a butterfly valve, a filter, a check valve, an electric valve, and a vacuum pump. The vacuum pump set is responsible for drawing a vacuum in the inlet pipe of the water supply pump set to assist in starting the circulating water pump.

[0010] Furthermore, each set of return water valve group is equipped with a butterfly valve and an electric valve. By switching the electric valve of the return water valve group, the return water is controlled to return to the corresponding cold water pool according to the corresponding water supply pipeline.

[0011] The beneficial effects of this invention are: 1. A set of water supply pumps and a set of return valves are installed in the hot rolling turbid circulating cold water pool and the heat treatment turbid circulating cold water pool, respectively. A water supply pipeline and a return pipeline are laid from the turbid circulating cold water pool to the circulating water LNG vaporizer. Liquid LNG is converted into gaseous LNG through the evaporation pipeline of the circulating water LNG vaporizer. At the same time, the cold energy released during the vaporization process of liquid LNG is replaced in the circulating water, thereby reducing the water temperature of the circulating water in the return pipeline. The continuous water circulation through the supply and return pipelines reduces the water temperature of the hot rolling turbid circulating cold water pool and the heat treatment line turbid circulating cold water pool. This solves the problem that the cooling tower cooling of the hot rolling and heat treatment turbid circulating water cannot meet the on-site water temperature requirements in the hot and humid summer. It not only improves the cooling effect of equipment and molds and enhances product quality, but also realizes the recovery and utilization of cold energy and reduces energy waste. 2. The temperature of the turbid circulating water is significantly reduced and is controllable. Under extreme high temperature and humidity conditions, the temperature of the heat treatment turbid circulating water can be reduced to below 28℃ according to the site requirements. When the online heat treatment is put into operation, the temperature of the turbid circulating water can also be maintained below 30℃. The temperature of the turbid circulating water can be adjusted in advance to meet the requirements of the site users. The temperature of the hot rolling turbid circulating water can be reduced to below 34℃, and the start-up time of the hot water booster pump and cooling tower fan in the hot rolling turbid circulating water system is reduced, thus reducing power consumption and achieving good results. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the connection structure of the present invention; Figure 2 This is a schematic diagram of the circulating water LNG vaporizer of the present invention.

[0013] In the diagram, 1. Ambient air LNG vaporizer; 2. Circulating water LNG vaporizer; 3. LNG storage tank outlet manifold; 4. Vaporizer outlet manifold; 5. Vaporizer LNG inlet pipe; 6. Vaporizer LNG outlet pipe; 7. Vaporizer LNG outlet temperature sensor; 8. Vaporizer LNG inlet control valve assembly; 9. Vaporizer LNG outlet control valve assembly; 10. Hot rolling turbid circulating cold water tank; 11. Heat treatment turbid circulating cold water tank; 12. Water supply pipeline; 13. Return water pipeline; 14. Hot rolling water supply pump assembly; 15. Hot rolling vacuum pump assembly; 16. Heat treatment water supply pump assembly; 17. Heat treatment vacuum pump assembly; 18. Hot rolling return water valve assembly; 19. Heat treatment return water valve assembly; 20. Vaporizer inlet butterfly valve; 21. Gas... 21. Vaporizer outlet butterfly valve; 22. Vaporizer side drain valve; 23. Cold water tank side drain valve; 24. Vent valve; 25. Cold water tank side temperature transmitter; 26. Flow meter; 27. Vaporizer side temperature transmitter; 28. Vaporizer side pressure transmitter; 2.1. Support; 2.2. Shell; 2.3. Evaporation pipe; 2.4. Insulation layer; 2.5. Shell side; 2.6. Tube side; 2.7. Lifting lug; 2.8. Observation hole; 2.9. Manhole; 2.10. Inlet; 2.11. Outlet; 2.12. Liquid LNG inlet; 2.13. NG outlet; 2.14. Drain valve; 2.15. Vent valve; 2.16. Full-lift safety valve; 2.17. Thermometer; 2.18. Pressure gauge. Detailed Implementation

[0014] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings.

[0015] like Figure 1 , 2 As shown, the process of using LNG vaporization cooling energy to reduce the temperature of turbid circulating water includes the following process steps: The first step includes a closed circulating water LNG vaporizer 2, with a liquid LNG inlet 2.12 and an NG outlet 2.13 connected in parallel to the LNG storage tank outlet manifold 3 and the vaporizer outlet manifold 4 of the ambient air LNG vaporizer 1, respectively, which can switch with the ambient air LNG vaporizer 1 and serve as backups for each other. In the second step, a set of hot rolling water supply pump group 14 is installed in the hot rolling turbid circulating cold water pool 10, and a set of heat treatment water supply pump group 16 is installed in the heat treatment turbid circulating cold water pool 11. A water supply pipeline 12 and a return water pipeline 13 are laid from the turbid circulating cold water pool to the circulating water LNG vaporizer 2, respectively. The water supply pipeline 12 is connected to the inlet 2.10 of the circulating water LNG vaporizer 2, and the return water pipeline 13 is connected to the outlet 2.11 of the circulating water LNG vaporizer 2. Liquid LNG flows through the tube side 2.6 of the evaporation pipe 2.3 of the closed circulating water LNG vaporizer 2 and becomes gas NG. At the same time, the cold energy released by the vaporization process of liquid LNG is replaced by the shell side 2.5 of the circulating water vaporizer 2 through the evaporation pipe 2.3, thereby reducing the temperature of the circulating water in the return water pipeline 13. The water temperature of the hot rolling turbid circulating cold water pool 10 and the heat treatment turbid circulating cold water pool 11 is reduced by the continuous water circulation through the water supply and return pipelines. The third step involves uploading the temperature, flow rate, and pressure data of the turbid circulating water supply and return pipelines to the HMI screen. When the circulating water at the outlet 2.11 of the circulating water LNG vaporizer 2 experiences a low temperature alarm, the pneumatic emergency shut-off valve of the vaporizer LNG inlet control valve group 8 of the interlock control vaporizer LNG inlet pipeline 5 is activated, shutting off the vaporizer LNG inlet pipeline 5. The vaporizer NG outlet pipeline 6 is equipped with a vaporizer NG outlet temperature sensor 7, which is linked with the pneumatic emergency shut-off valve. When the NG outlet temperature is below 8°C, an alarm is triggered. When the NG outlet temperature is below 3°C, the pneumatic emergency shut-off valves of the vaporizer LNG inlet control valve group 8 and the vaporizer NG outlet control valve group 9 are activated, shutting off the vaporizer LNG inlet pipeline 5 and the vaporizer NG outlet pipeline 6.

[0016] The present invention discloses a special device for reducing the temperature of turbid circulating water by utilizing the cold energy of LNG vaporization. It consists of three parts: a closed circulating water LNG vaporizer 2, an LNG vaporization pipeline system, and a turbid circulating water supply and return system. The closed-loop circulating water LNG vaporizer 2 is the core of the entire equipment, consisting of a support 2.1, a cylinder 2.2, an insulation layer 2.4, evaporation pipes 2.3, and lifting lugs 2.7. The evaporation pipes 2.3 are placed inside the cylinder 2.2; the shell side 2.5 connects the cylinder 2.2 and the evaporation pipes 2.3. The bottom of the cylinder 2.2 has an inlet 2.10 and a drain valve 2.14, and the top has an outlet 2.11. The inside of the evaporation pipes 2.3 is the tube side 2.6, and the lower part of the evaporation pipes 2.3... It has a liquid LNG inlet 2.12 and an NG outlet 2.13 at the top; the top of the cylinder 2.2 has an observation hole 2.8 and the bottom has a manhole 2.9; the middle of the cylinder 2.2 is equipped with a vent valve 2.15, a full-lift safety valve 2.16, a thermometer 2.17, and a pressure gauge 2.18, which are all connected to the shell side 2.5; an insulation layer 2.4 is installed on the outer surface of the cylinder 2.2; a lifting lug 2.7 is fixed at the top of the cylinder 2.2, and a support 2.1 is installed at the bottom of the cylinder 2.2. The closed circulating water LNG vaporizer 2 has a cylinder 2.2 made of Q245R material, welded with pickling and passivation treatment on the inner surface, and covered with a 50mm thick insulation layer 2.4 after anti-corrosion paint treatment on the outer surface; to avoid chloride ion corrosion of the evaporation pipe 2.3, the evaporation pipe 2.3 is made of S31603 material, and all evaporation pipes 2.3 are degreased; related valves and flanges are all made of stainless steel. The closed-loop circulating water LNG vaporizer 2 has a small footprint and high cold energy absorption rate. Turbid circulating water enters the shell side 2.5 through the bottom inlet 2.10 of the cylinder 2.2, flows through the shell side 2.5 and then flows out from the top outlet 2.11. The evaporation pipe 2.3 is completely submerged in the circulating water in the shell side 2.5. Liquid LNG enters the evaporation pipe 2.3 through the lower liquid LNG inlet 2.12, flows through the tube side 2.6 of the evaporation pipe 2.3 and becomes gas NG. At the same time, the cold energy released by the vaporization of LNG is replaced in the circulating water in the shell side 2.5, so that the temperature of the circulating water is reduced. When the gas NG outlet temperature reaches the design gas consumption requirements, it flows out from the upper NG outlet 2.13. The LNG vaporization pipeline system includes an LNG inlet pipe 5 for the vaporizer, an NG outlet pipe 6 for the vaporizer, an LNG inlet control valve assembly 8 for the vaporizer, an NG outlet control valve assembly 9 for the vaporizer, and an NG outlet temperature sensor 7 for the vaporizer. The LNG inlet pipe 5 and the NG outlet pipe 6 are made of 06Cr19Ni10 material. The LNG inlet pipe 5 connects to the LNG storage tank outlet manifold 3 and is connected to the liquid LNG inlet 2.12 of the circulating water LNG vaporizer 2 via the LNG inlet control valve assembly 8. The LNG inlet control valve assembly 8 is equipped with two cryogenic shut-off valves, one pneumatic emergency shut-off valve, and one cryogenic full-open safety valve. The NG outlet pipe 6 is connected to the NG outlet 2.13 of the circulating water LNG vaporizer 2, and is connected to the vaporizer outlet manifold 4 through the vaporizer NG outlet control valve group 9. The vaporizer NG outlet control valve group 9 is equipped with two cryogenic shut-off valves, two ultra-low temperature full-opening safety valves, and one pneumatic emergency shut-off valve. The vaporizer NG outlet pipe 6 is equipped with a vaporizer NG outlet temperature sensor 7, which is linked with the pneumatic emergency shut-off valve. An alarm is triggered when the NG outlet temperature is below 8°C. When the NG outlet temperature is below 3°C, the pneumatic emergency shut-off valves of the vaporizer LNG inlet control valve group 8 and the vaporizer NG outlet control valve group 9 are activated, cutting off the vaporizer LNG inlet pipe 5 and the vaporizer NG outlet pipe 6. The turbid circulating water supply and return system includes a hot rolling turbid circulating cold water tank 10, a heat treatment turbid circulating cold water tank 11, a water supply pipeline 12, a return water pipeline 13, a hot rolling water supply pump group 14, a heat treatment water supply pump group 16, a hot rolling vacuum pump group 15, a heat treatment vacuum pump group 17, a hot rolling return water valve group 18, a heat treatment return water valve group 19, a vaporizer inlet butterfly valve 20, and a vaporizer outlet butterfly valve 21. The hot rolling turbid circulating cold water tank 10 is equipped with one set of hot rolling water supply pump group 14 and hot rolling return water valve group 18; the heat treatment turbid circulating cold water tank 11 is equipped with one set of heat treatment water supply pump group 16 and heat treatment return water valve group 19. A water supply line is laid from the turbid circulating cold water tank to the circulating water LNG vaporizer 2. Water pipeline 12 and return water pipeline 13 are connected. Water supply pipeline 12 is connected to the inlet 2.10 of the circulating water LNG vaporizer 2 through vaporizer inlet butterfly valve 20, and return water pipeline 13 is connected to the outlet 2.11 of the circulating water LNG vaporizer 2 through vaporizer outlet butterfly valve 21. The two sets of water supply pump groups and return water valve groups can be switched and used as backups for each other according to the site conditions. The water supply pipeline and return water pipeline are shared. Hot rolling vacuum pump group 15 is installed at a high position on the inlet pipeline between hot rolling turbid circulating cold water pool 10 and hot rolling water supply pump group 14. Heat treatment vacuum pump group 17 is installed at a high position on the inlet pipeline between heat treatment turbid circulating cold water pool 11 and heat treatment water supply pump group 16. A cold water tank-side drain valve 23 is installed on the water supply pipe 12 and return pipe 13 on the cold water tank side, and a vaporizer-side drain valve 22 is installed on the water supply pipe 12 and return pipe 13 on the vaporizer side. The drain valves are located at the bottom of the pipes. A vent valve 24 is installed in the middle of the water supply pipe 12 and return pipe 13, and the vent valve is located at the top of the pipes. A cold water tank-side temperature transmitter 25 is installed on the water supply pipe 12 and return pipe 13 on the cold water tank side for temperature detection. A vaporizer-side temperature transmitter 27 and a vaporizer-side pressure transmitter 28 are installed on the water supply pipe 12 and return pipe 13 on the vaporizer side for temperature and pressure detection. A flow meter 26 is installed on the water supply pipe 12 on the vaporizer side for flow detection. The hot rolling water supply pump group 14 and the heat treatment water supply pump group 16 draw water from the middle part of the hot rolling turbid circulating cold water pool 10 and the heat treatment turbid circulating cold water pool 11, respectively. The inlet of the hot rolling water supply pump group 14 and the heat treatment water supply pump group 16 are respectively equipped with filter screens. Each water supply pump group is equipped with an inlet butterfly valve, a drain valve, a Y-type filter, an inlet flexible joint, an inlet reducer, an inlet pressure gauge, a circulating water pump, an outlet pressure gauge, an outlet reducer, an outlet flexible joint, a check valve, an electric regulating valve, and an outlet butterfly valve in sequence. The flow rate of the water supply pump group is adjusted by the electric regulating valve. Each vacuum pump group is equipped with a butterfly valve, a filter, a check valve, an electric valve, and a vacuum pump. The vacuum pump group is responsible for drawing a vacuum in the inlet pipeline of the water supply pump group to assist the starting of the circulating water pump. Each return water valve group is equipped with a butterfly valve and an electric valve. By switching the electric valve of the return water valve group, the return water is controlled to return to the corresponding cold water pool according to the corresponding water supply pipeline.

[0017] This invention relates to a process and specialized equipment for reducing the temperature of turbid circulating water using the cooling energy of LNG vaporization. It employs a 4000 Nm³ / h closed-loop circulating water LNG vaporizer, with its inlet and outlet connected in parallel to the liquid outlet manifold of the existing ambient temperature LNG vaporizer's LNG storage tank and the gas outlet manifold of the existing vaporizer, respectively. This allows for switching and backup between the two existing ambient temperature LNG vaporizers. A Q=150 m³ / h water supply pump set is installed in both the hot rolling turbid circulating cold water pool and the heat treatment line turbid circulating cold water pool. A DN200 water supply pipeline and a DN200 water return pipeline are laid from the turbid circulating cold water pool to the circulating water LNG vaporizer. Liquid LNG flows through the evaporation pipes of the closed-loop circulating water LNG vaporizer, transforming into gaseous LNG. Simultaneously, the cooling energy released during the vaporization process of the liquid LNG is transferred to the circulating water in the vaporizer shell side through the evaporation pipes. The system lowers the temperature of the circulating water in the return water pipeline by continuously circulating water through the supply and return water pipelines to reduce the temperature of the hot rolling turbid circulating cold water pool and the heat treatment line turbid circulating cold water pool. Each of the hot rolling and heat treatment turbid circulating cold water pools is equipped with a set of supply pumps and return valves. These two sets of pumps and valves can be switched and used as backups as needed. The return water is controlled by switching the electric valves of the return valves, allowing the return water to the corresponding cold water pools via the supply pipelines. Liquid LNG is used to exchange heat with the circulating water, recovering and utilizing the cold energy released during the vaporization of LNG. This solves the problem that cooling towers used for cooling the circulating water in hot rolling and heat treatment cannot meet the on-site water temperature requirements during hot and humid summer weather. This improves the cooling effect of equipment and dies, enhances product quality, and also achieves cold energy recovery and utilization, reducing energy waste.

[0018] It should be understood that any technical features not elaborated in detail in this specification belong to the prior art. Although the embodiments of this invention have been described above in conjunction with the accompanying drawings, this invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this invention without departing from the spirit and scope of the claims, and these all fall within the scope of protection of this invention.

Claims

1. A process for reducing the temperature of turbid circulating water using LNG vaporization cooling energy, characterized in that, The process includes the following steps: a includes a closed circulating water LNG vaporizer, with the liquid LNG inlet and NG outlet connected in parallel to the LNG storage tank liquid outlet manifold and vaporizer gas outlet manifold of the ambient temperature LNG vaporizer, respectively, and can be switched with the ambient temperature LNG vaporizer and serve as backups for each other; b. A hot rolling turbid circulating cold water pool is equipped with a hot rolling water supply pump set, and a heat treatment turbid circulating cold water pool is equipped with a heat treatment water supply pump set. A water supply pipeline and a return pipeline are laid from the turbid circulating cold water pool to the circulating water LNG vaporizer. The water supply pipeline is connected to the inlet of the circulating water LNG vaporizer, and the return pipeline is connected to the outlet of the circulating water LNG vaporizer. Liquid LNG flows through the evaporation pipe of the closed circulating water LNG vaporizer and becomes gas NG. At the same time, the cold energy released by the vaporization process of liquid LNG is replaced by the shell circulating water of the circulating water LNG vaporizer through the evaporation pipe, thereby reducing the temperature of the circulating water in the return pipeline. The water temperature of the hot rolling turbid circulating cold water pool and the heat treatment turbid circulating cold water pool is reduced through continuous water circulation in the water supply and return pipelines. c. The temperature, flow rate, and pressure detection data of the turbid circulating water supply and return pipelines are uploaded to the HMI screen respectively. When the circulating water at the outlet of the circulating water LNG vaporizer shows a low temperature alarm, the pneumatic emergency shut-off valve of the vaporizer LNG inlet control valve group of the interlock control valve group is activated, cutting off the vaporizer LNG inlet pipeline. The vaporizer NG outlet pipeline is equipped with a vaporizer NG outlet temperature sensor, which is linked with the pneumatic emergency shut-off valve. When the NG outlet temperature is lower than 8°C, an alarm is triggered. When the NG outlet temperature is lower than 3°C, the pneumatic emergency shut-off valves of the vaporizer LNG inlet control valve group and the vaporizer NG outlet control valve group are activated, cutting off the vaporizer LNG inlet pipeline and the vaporizer NG outlet pipeline.

2. The specialized equipment for reducing the temperature of turbid circulating water using LNG vaporization cooling energy as described in claim 1, characterized in that, It consists of three parts: a closed circulating water LNG vaporizer, an LNG vaporization pipeline system, and a turbid circulating water supply and return system; The enclosed circulating water LNG vaporizer is the core of the entire equipment, consisting of a support, a cylinder, an insulation layer, evaporation pipes, and lifting lugs. The evaporation pipes are placed inside the cylinder. The shell side is between the cylinder and the evaporation pipes. The bottom of the cylinder has an inlet and a drain valve, and the top has an outlet. The tube side is inside the evaporation pipes. The lower part of the evaporation pipes has a liquid LNG inlet, and the upper part has an LNG outlet. The top of the cylinder has an observation hole, and the lower part has a manhole. The middle of the cylinder is equipped with a vent valve, a full-opening safety valve, a thermometer, and a pressure gauge, all of which are connected to the shell side. The outer surface of the cylinder is covered with an insulation layer. The top of the cylinder has lifting lugs, and the bottom of the cylinder has a support. The LNG vaporization pipeline system includes an LNG inlet pipeline for the vaporizer, an NG outlet pipeline for the vaporizer, an LNG inlet control valve assembly for the vaporizer, an NG outlet control valve assembly for the vaporizer, and an NG outlet temperature sensor for the vaporizer. The LNG inlet pipeline and the NG outlet pipeline are made of 06Cr19Ni10 material. The LNG inlet pipeline connects to the LNG storage tank outlet manifold and is connected to the liquid LNG inlet of the circulating water LNG vaporizer via the LNG inlet control valve assembly. The vaporizer LNG inlet control valve group is equipped with two cryogenic shut-off valves, one pneumatic emergency shut-off valve, and one ultra-low temperature full-open safety valve; the vaporizer NG outlet pipeline is connected to the NG outlet of the circulating water LNG vaporizer, and is connected to the vaporizer outlet manifold through the vaporizer NG outlet control valve group, which is equipped with two cryogenic shut-off valves, two ultra-low temperature full-open safety valves, and one pneumatic emergency shut-off valve; the vaporizer NG outlet pipeline is equipped with a vaporizer NG outlet temperature sensor. The turbid circulating water supply and return system includes a hot rolling turbid circulating cold water tank, a heat treatment turbid circulating cold water tank, water supply pipelines, return water pipelines, hot rolling water supply pump sets, heat treatment water supply pump sets, hot rolling vacuum pump sets, heat treatment vacuum pump sets, hot rolling return water valve sets, heat treatment return water valve sets, vaporizer inlet butterfly valves, and vaporizer outlet butterfly valves. The hot rolling turbid circulating cold water tank is equipped with one set of hot rolling water supply pump sets and one set of hot rolling return water valve sets, and the heat treatment turbid circulating cold water tank is equipped with one set of heat treatment water supply pump sets and one set of heat treatment return water valve sets. A pipeline is laid from the turbid circulating cold water tank to the circulating water LNG vaporizer. The system includes a water supply pipeline and a return pipeline. The water supply pipeline is connected to the inlet of the circulating water LNG vaporizer via a butterfly valve at the vaporizer inlet, and the return pipeline is connected to the outlet of the circulating water LNG vaporizer via a butterfly valve at the vaporizer outlet. Two sets of water supply pump groups and return valve groups are interchangeable and serve as backups for each other, sharing the same water supply and return pipelines. The hot rolling vacuum pump group is installed at a high position on the inlet pipeline between the hot rolling circulating cold water pool and the hot rolling water supply pump group. The heat treatment vacuum pump group is also installed at a high position on the inlet pipeline between the heat treatment circulating cold water pool and the heat treatment water supply pump group. A cold water tank-side drain valve is installed on both the supply and return water pipelines on one side of the cold water tank, and a vaporizer-side drain valve is installed on both the supply and return water pipelines on the other side of the vaporizer. The drain valves are located at the bottom of the pipelines. A vent valve is installed in the middle of both the supply and return water pipelines, located at the top of the pipelines. A cold water tank-side temperature transmitter is installed on both the supply and return water pipelines on the cold water tank side for detecting the circulating water supply temperature. A vaporizer-side temperature transmitter and a vaporizer-side pressure transmitter are installed on both the supply and return water pipelines on the vaporizer side for detecting the circulating water return temperature and pressure. A flow meter is installed on the supply water pipeline on the vaporizer side for detecting the circulating water flow rate.

3. The specialized equipment for reducing the temperature of turbid circulating water using LNG vaporization cooling energy according to claim 2, characterized in that, The hot rolling water supply pump group and the heat treatment water supply pump group draw water from the middle part of the hot rolling turbid circulating cold water pool and the heat treatment turbid circulating cold water pool, respectively. The inlet of the hot rolling water supply pump group and the heat treatment water supply pump group are respectively equipped with filter screens.

4. The specialized equipment for reducing the temperature of turbid circulating water using LNG vaporization cooling energy according to claim 2, characterized in that, Each water supply pump set is sequentially equipped with an inlet butterfly valve, a drain valve, a Y-type filter, an inlet flexible joint, an inlet reducer, an inlet pressure gauge, a circulating water pump, an outlet pressure gauge, an outlet reducer, an outlet flexible joint, a check valve, an electric regulating valve, and an outlet butterfly valve; the flow rate of the water supply pump set is adjusted by the electric regulating valve.

5. The specialized equipment for reducing the temperature of turbid circulating water using LNG vaporization cooling energy according to claim 2, characterized in that, Each vacuum pump set is equipped with a butterfly valve, filter, check valve, electric valve, and vacuum pump. The vacuum pump set is responsible for drawing a vacuum in the inlet pipe of the water supply pump set to assist in starting the circulating water pump.

6. The specialized equipment for reducing the temperature of turbid circulating water using LNG vaporization cooling energy according to claim 2, characterized in that, Each set of return water valve group is equipped with a butterfly valve and an electric valve. By switching the electric valve of the return water valve group, the return water is controlled to return to the corresponding cold water pool according to the corresponding water supply pipeline.

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