A urea high - tuning device waste heat coupling natural gas differential pressure power generation system and operation method

Abstract

The application discloses a kind of urea high-tuning device waste heat coupling natural gas pressure difference power generation system and operating method, including heat exchange system;Heat exchange system includes high-pressure scrubber, circulating water pump and cooling water heat exchanger;High-pressure scrubber is connected with cooling water heat exchanger by high-tuning water heat section pipeline, and cooling water heat exchanger is connected with circulating water pump by high-tuning water cooling section pipeline;Natural gas pressure difference power generation system includes natural gas expander;Water gas heat exchanger inlet, outlet are connected with high-tuning water hot, cold section pipeline by inlet, outlet pipeline respectively;Water gas heat exchanger gas inlet is connected with high-pressure pipe network natural gas pipeline, and water gas heat exchanger exhaust port is connected with expander gas inlet by natural gas inlet pipeline, and natural gas outlet pipeline one end is connected with expander gas outlet, and its other end is connected with subsequent process system.The application realizes the utilization of residual pressure and waste heat simultaneously, reduces additional investment, and can ensure that the parameters of high-pressure natural gas after expansion meet the requirements of subsequent process.

Description

Technical Field

[0001] This invention belongs to the field of natural gas differential pressure power generation, specifically a waste heat coupling natural gas differential pressure power generation system and its operation method for a urea high-pressure adjustment device. Background Technology

[0002] In the natural gas-to-urea scenario, the raw material natural gas comes from a high-pressure pipeline network, and the pressure energy of the high-pressure natural gas can be used to generate electricity. However, for natural gas differential pressure power generation technology, the temperature of the natural gas drops by about 20°C after it expands through the turbine. The parameters of the expanded natural gas will not meet the requirements of subsequent processes. Therefore, an additional heat source is needed to reheat the low-pressure natural gas to make its parameters meet the process requirements. This not only increases the cost of heat sources and related equipment, but also wastes the waste heat of the urea high-pressure unit in the natural gas-to-urea scenario.

[0003] Currently, the most common methods for reheating low-temperature natural gas are circulating water reheating or heat pump reheating. Both of these methods require additional heat sources, which increases system investment. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a waste heat coupling natural gas differential pressure power generation system and its operation method that utilizes the waste heat resources in the natural gas urea process to heat natural gas, thereby achieving simultaneous utilization of waste pressure and waste heat, reducing additional investment, and ensuring that the parameters of the expanded high-pressure natural gas meet the requirements of subsequent processes.

[0005] The technical objective of this invention is achieved through the following technical solution: A waste heat coupling natural gas differential pressure power generation system for a urea high-pressure regulating unit includes a heat exchange system, a natural gas differential pressure power generation system, and a water-gas heat exchanger. The heat exchange system includes a high-pressure scrubber, a circulating water pump, and a cooling water heat exchanger. The high-pressure scrubber and the cooling water heat exchanger are connected via a high-pressure regulating water-heat section pipeline, the cooling water heat exchanger and the circulating water pump are connected via a high-pressure regulating water-cooling section pipeline, and the circulating water pump and the high-pressure scrubber are connected via a circulating water pipeline. The natural gas differential pressure power generation system includes a natural gas expander, a natural gas inlet pipeline, and a natural gas outlet pipeline. The inlet and outlet of the water-gas heat exchanger are connected to the high-pressure regulating water-heat section pipeline and the high-pressure regulating water-cooling section pipeline, respectively, via inlet and outlet pipelines. The gas inlet of the water-gas heat exchanger is connected to the natural gas pipeline of the high-pressure pipeline network, the gas outlet of the water-gas heat exchanger is connected to the gas inlet of the expander via a natural gas inlet pipeline, and one end of the natural gas outlet pipeline is connected to the gas outlet of the expander, while the other end is connected to the subsequent process system.

[0006] Preferably, the high-adjustment water-heat section pipe and the high-adjustment water-cool section pipe are respectively equipped with a first valve and a second valve at the high-adjustment water inlet and high-adjustment water outlet near the cooling water heat exchanger; one end of the water inlet pipe is connected to the water inlet of the water-air heat exchanger, and the other end is connected to the high-adjustment water-heat section pipe between the first valve and the high-pressure scrubber, and the water inlet pipe is equipped with an inlet pipe valve; one end of the drain pipe is connected to the drain outlet of the water-air heat exchanger, and the other end is connected to the high-adjustment water-cool section pipe between the second valve and the circulating water pump, and the drain pipe is equipped with a drain pipe valve.

[0007] Preferably, the natural gas differential pressure power generation system further includes a bypass, wherein the bypass inlet end of the bypass is connected to the natural gas inlet pipeline, and the bypass outlet end of the bypass is connected to the natural gas outlet pipeline; a bypass valve is provided on the bypass.

[0008] Preferably, the natural gas differential pressure power generation system further includes a pressure-reducing bypass pipeline, wherein the inlet end of the pressure-reducing bypass pipeline is connected to the natural gas inlet pipeline of the high-pressure pipeline network, and the outlet end of the pressure-reducing bypass pipeline is connected to the natural gas outlet pipeline and is located between the bypass outlet end and the subsequent process system; a pressure-reducing valve is provided on the pressure-reducing bypass pipeline.

[0009] Preferably, the natural gas expander is a turbine expander.

[0010] Preferably, the cooling water heat exchanger includes a high-adjustment water inlet connected to a high-adjustment hot section pipeline, a high-adjustment water outlet connected to a high-adjustment cold section pipeline, a cooling water inlet connected to a cooling water inlet pipeline, and a cooling water outlet connected to a cooling water outlet pipeline.

[0011] An operation method for a urea high-pressure regulating unit waste heat coupled with natural gas differential pressure power generation system as described above. During normal power generation operation: The bypass valve is closed, the pressure reducing valve is closed, the first valve and the second valve are closed, and the inlet pipe valve and the drain pipe valve are opened, allowing the high-temperature, high-pressure water discharged from the high-pressure scrubber to enter the water-gas heat exchanger to release heat; the high-pressure natural gas absorbs waste heat and heats up in the water-gas heat exchanger; the heated natural gas enters the natural gas expander through the natural gas inlet pipe for expansion and power generation, and then enters the subsequent process system through the natural gas outlet pipe. When a natural gas expander experiences an emergency malfunction: Close the inlet and outlet valves, open the first and second valves, and close the natural gas expander and pressure reducing valve. At the same time, open the bypass valve to allow high-pressure natural gas to enter the natural gas outlet pipeline directly via the bypass. When the natural gas expander needs to be shut down for maintenance: Close the inlet and outlet valves, and open the first and second valves; close the natural gas expander and bypass valves; at the same time, open the pressure reducing valve to allow high-pressure natural gas to enter the natural gas outlet pipeline through the pressure reducing bypass pipeline.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. The urea high-pressure regulating unit waste heat coupled with natural gas differential pressure power generation system of the present invention includes a heat exchange system, a natural gas differential pressure power generation system, and a water-gas heat exchanger. The natural gas temperature after heat exchange in the water-gas heat exchanger can reach approximately 35°C. After expansion, the temperature of the natural gas at this temperature drops to approximately 10°C, a parameter that meets the requirements of subsequent processes. By using the water-gas heat exchanger to preheat the high-pressure pipeline natural gas through the high-temperature, high-pressure regulating water of the high-pressure scrubber, and driving the natural gas expander to generate electricity, the system achieves dual high-efficiency utilization of waste heat recovery from the urea unit and natural gas differential pressure energy, while simultaneously improving the power generation efficiency of the natural gas expander, thus combining energy saving and economic benefits. This technical measure achieves simultaneous utilization of waste pressure and waste heat, reduces additional investment, and ensures that the parameters of the expanded high-pressure natural gas meet the requirements of subsequent processes.

[0013] 2. The natural gas differential pressure power generation system of the present invention also includes a bypass, wherein the bypass inlet end of the bypass is connected to the natural gas inlet pipeline, and the bypass outlet end of the bypass is connected to the natural gas outlet pipeline; a bypass valve is provided on the bypass. By setting a bypass path with a valve between the inlet and outlet pipelines of the expander, the natural gas flow direction can be quickly switched in the event of expander failure or maintenance, ensuring uninterrupted direct supply of high-pressure natural gas to the subsequent process system, significantly improving the operational reliability and process continuity of the power generation system.

[0014] 3. The natural gas differential pressure power generation system of the present invention also includes a pressure-reducing bypass pipeline. The inlet end of the pressure-reducing bypass pipeline is connected to the natural gas inlet pipeline of the high-pressure pipeline network, and the outlet end of the pressure-reducing bypass pipeline is connected to the natural gas outlet pipeline and is located between the bypass outlet end and the subsequent process system. A pressure-reducing valve is provided on the pressure-reducing bypass pipeline. By setting a pressure-reducing bypass pipeline with a pressure-reducing valve as an independent backup channel, high-pressure natural gas can be safely depressurized and delivered to the subsequent process system when both the natural gas expander and the conventional bypass fail simultaneously, providing a final safety guarantee for the power generation system and ensuring process continuity and equipment safety under extreme operating conditions. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system structure of the present invention; Figure reference numerals: 1—High-pressure washer; 11—High-pressure water heating section pipe; 12—First valve; 2—Circulating water pump; 21—High-pressure water-cooled section piping; 22—Second valve; 23—Circulating water piping; 3—Cooling water heat exchanger; 31—Cooling water inlet pipe; 32—Cooling water outlet pipe; 4—Natural gas expander; 41—Natural gas inlet pipeline; 42—Natural gas outlet pipeline; 5—Water-gas heat exchanger; 51—Water inlet pipeline; 52—Drainage pipeline; 53—Water inlet pipeline valve; 54—Drainage pipeline valve; 6—High-pressure pipeline natural gas inlet pipeline; 7—Subsequent process system; 8—Bypass; 81—Bypass valve; 9—Pressure reducing bypass pipeline; 91—Pressure reducing valve. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0018] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0019] like Figure 1As shown, a waste heat coupling natural gas differential pressure power generation system for a urea high-pressure regulating unit includes a heat exchange system, a natural gas differential pressure power generation system, and a water-gas heat exchanger 5. The heat exchange system includes a high-pressure scrubber 1, a circulating water pump 2, and a cooling water heat exchanger 3. The high-pressure scrubber 1 and the cooling water heat exchanger 3 are connected by a high-pressure regulating water-heat section pipe 11, the cooling water heat exchanger 3 and the circulating water pump 2 are connected by a high-pressure regulating water-cooling section pipe 21, and the circulating water pump 2 and the high-pressure scrubber 1 are connected by a circulating water pipe 23. The natural gas differential pressure power generation system includes a natural gas... The gas expander 4, natural gas inlet pipe 41, and natural gas outlet pipe 42 are connected to the high-pressure water-cooling section pipe 11 and the high-pressure water-heating section pipe 21 respectively via inlet pipe 51 and outlet pipe 52. The gas inlet of the water-gas heat exchanger 5 is connected to the high-pressure natural gas pipeline 6, and the gas outlet of the water-gas heat exchanger 5 is connected to the expander inlet via natural gas inlet pipe 41. One end of the natural gas outlet pipe 42 is connected to the expander outlet, and the other end is connected to the subsequent process system 7. In specific implementation, the natural gas expander 4 includes an expander inlet for introducing natural gas and an expander inlet and outlet for discharging natural gas. The expander inlet is connected to the natural gas inlet pipe 41, and the expander inlet and outlet are connected to the natural gas outlet pipe 42. The temperature of the natural gas after heat exchange in the water-gas heat exchanger 5 can reach about 35°C. After expansion, the temperature of the natural gas at this temperature drops to about 10°C, which meets the requirements of the subsequent process. The high-temperature, high-adjustment water waste heat from the high-pressure scrubber 1 is used by the water-gas heat exchanger 5 to preheat the high-pressure pipeline natural gas and drive the natural gas expander 4 to generate electricity. This achieves dual high-efficiency utilization of waste heat recovery from the urea plant and the energy from the natural gas pressure difference, while simultaneously improving the power generation efficiency of the natural gas expander 4, thus combining energy saving and economic benefits. This technical measure enables the simultaneous utilization of waste pressure and waste heat, reduces additional investment, and ensures that the parameters of the expanded high-pressure natural gas meet the requirements of subsequent processes.

[0020] like Figure 1As shown, the high-adjustment water-heat section pipe 11 and the high-adjustment water-cooling section pipe 21 are respectively equipped with a first valve 12 and a second valve 22 at the high-adjustment water inlet and outlet near the cooling water heat exchanger 3; one end of the inlet pipe 51 is connected to the inlet of the water-air heat exchanger 5, and the other end is connected to the high-adjustment water-heat section pipe 11 between the first valve 12 and the high-pressure scrubber 1, and the inlet pipe 51 is equipped with an inlet pipe valve 53; one end of the drain pipe 52 is connected to the drain outlet of the water-air heat exchanger 5, and the other end is connected to the high-adjustment water-cooling section pipe 21 between the second valve 22 and the circulating water pump 2, and the drain pipe 52 is equipped with a drain pipe valve 54. In actual use, the high-adjustment water-heat section pipe 11 is equipped with a first valve 12 at the high-adjustment water inlet near the cooling water heat exchanger 3, and the high-adjustment water-cooling section pipe 21 is equipped with a second valve 22 at the high-adjustment water outlet near the cooling water heat exchanger 3. When generating electricity using waste heat, and heating natural gas through the water-gas heat exchanger 5, close the first valve 12 and the second valve 22, and open the inlet water pipe valve 53 and the drain water pipe valve 54; allowing the high-temperature high-pressure water to enter the water-gas heat exchanger 5 along the high-pressure water-heat section pipe 11 to heat the natural gas. When it is necessary to inspect / maintain the water-gas heat exchanger 5 / natural gas expander 4, close the inlet water pipe valve 53 and the drain water pipe valve 54, and open the first valve 12 and the second valve 22, allowing the high-temperature high-pressure water to enter the cooling water heat exchanger 3 along the high-pressure water-heat section pipe 11 for cooling, then enter the high-pressure water-cooling section pipe 21, and finally enter the circulating water pump 2. By coordinating the opening and closing of the first valve 12 and the second valve 22 with the inlet pipe valve 53 and the outlet pipe valve 54, the high-speed water cooling path can be flexibly switched between the original cooling water heat exchanger 3 and the newly added water-air heat exchanger 5. This ensures that the system can safely isolate the original cooling equipment when recovering waste heat for power generation, and can quickly restore the original cooling process when maintenance is required, thereby improving the adaptability and reliability of the system operation.

[0021] like Figure 1 As shown, the cooling water heat exchanger 3 includes a high-pressure water inlet connected to the high-pressure hot section pipe 11, a high-pressure water outlet connected to the high-pressure cold section pipe 21, a cooling water inlet connected to the cooling water inlet pipe 31, and a cooling water outlet connected to the cooling water outlet pipe 32. This technology clearly distinguishes the independent inlet and outlet channels for the high-pressure water and cooling water, achieving physical isolation and efficient, controllable heat exchange between the two water flows within the heat exchanger. This ensures both the purity of the process medium and the stable transfer of waste heat to the cooling water system, maintaining the thermal balance of the core processes in the urea plant.

[0022] like Figure 1As shown, the natural gas differential pressure power generation system also includes a bypass 8. The bypass inlet of the bypass 8 is connected to the natural gas inlet pipeline 41, and the bypass outlet of the bypass 8 is connected to the natural gas outlet pipeline 42. A bypass valve 81 is installed on the bypass 8. By setting a bypass path with a valve between the inlet and outlet pipelines of the expander, the natural gas flow direction can be quickly switched in case of expander failure or maintenance, ensuring that high-pressure natural gas is supplied directly to the subsequent process system 7 without interruption, which significantly improves the operational reliability and process continuity of the power generation system.

[0023] like Figure 1 As shown, the natural gas differential pressure power generation system also includes a pressure-reducing bypass valve pipeline 9. The inlet end of the pressure-reducing bypass valve pipeline 9 is connected to the natural gas inlet pipeline 6 of the high-pressure pipeline network, and the outlet end of the pressure-reducing bypass valve pipeline 9 is connected to the natural gas outlet pipeline 42, located between the bypass outlet end and the subsequent process system 7. A pressure-reducing valve 91 is installed on the pressure-reducing bypass valve pipeline 9. By setting the pressure-reducing bypass valve pipeline 9 with pressure-reducing valve 91 as an independent backup channel, the high-pressure natural gas can be safely depressurized and delivered to the subsequent process system 7 when both the natural gas expander 4 and the conventional bypass 8 fail simultaneously, providing a final safety guarantee for the power generation system and ensuring process continuity and equipment safety under extreme operating conditions.

[0024] In practical use, the pressure reducing valve 91 can be a P / V valve or the like.

[0025] An operation method for a urea high-pressure regulating unit waste heat coupled with natural gas differential pressure power generation system. During normal power generation operation: Bypass valve 81 is closed, pressure reducing valve 91 is closed, first valve 12 and second valve 22 are closed; inlet pipe valve 53 and drain pipe valve 54 are opened to allow the high-temperature, high-pressure water discharged from high-pressure scrubber 1 to enter water-gas heat exchanger 5 to release heat; high-pressure natural gas absorbs waste heat and heats up in water-gas heat exchanger 5; the heated natural gas enters natural gas expander 4 through natural gas inlet pipe 41 for expansion and power generation, and then enters subsequent process system 7 through natural gas outlet pipe 42; When the natural gas expander 4 experiences an emergency malfunction: Close the inlet valve 53 and the outlet valve 54, open the first valve 12 and the second valve 22, and close the natural gas expander 4 and the pressure reducing valve 91; at the same time, open the bypass valve 81 to allow high-pressure natural gas to directly enter the natural gas outlet pipeline 42 via the bypass valve 8. When natural gas expander 4 needs to be shut down for maintenance: Close the inlet valve 53 and the outlet valve 54, and open the first valve 12 and the second valve 22; close the natural gas expander 4 and the bypass valve 81; at the same time, open the pressure reducing valve 91 to allow high-pressure natural gas to enter the natural gas outlet pipeline 42 through the pressure reducing bypass valve pipeline 9.

[0026] In actual operation, the mode can be flexibly switched according to the actual situation. Through precise valve control and process switching, the triple guarantee of waste heat recovery power generation, continuous operation of core processes and safety handling of extreme failures is achieved, which maximizes the balance between energy cascade utilization efficiency, system operation reliability and inherent safety of the device.

[0027] In practical implementation, the natural gas expander 4 is a turbine expander. Taking a urea plant with an annual production capacity of 600,000 tons as an example, its hourly natural gas consumption is approximately 50,000 Nm³ / h, the pipeline gas pressure is 8 MPa, and the temperature is 20°C. The natural gas process requires a pressure of 4 MPa and a temperature of 5°C. By installing an 800kW turbine expander to recover this pressure energy, the annual power generation revenue is approximately 2.6384 million yuan. Specific turbine generator unit parameters are shown in Table 1.

[0028] Table 1 Turbine Generator Set Parameters The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A urea high-temperature unit waste heat coupled natural gas pressure differential power generation system, characterized in that, This includes heat exchange systems, natural gas differential pressure power generation systems, and water-gas heat exchangers; The heat exchange system includes a high-pressure scrubber, a circulating water pump, and a cooling water heat exchanger; the high-pressure scrubber and the cooling water heat exchanger are connected by a high-pressure water-heat section pipe, the cooling water heat exchanger and the circulating water pump are connected by a high-pressure water-cool section pipe, and the circulating water pump and the high-pressure scrubber are connected by a circulating water pipe. The natural gas differential pressure power generation system includes a natural gas expander, a natural gas inlet pipeline, and a natural gas outlet pipeline; The inlet and outlet of the water-gas heat exchanger are connected to the high-pressure water-heat section pipeline and the high-pressure water-cool section pipeline respectively through the inlet pipe and the outlet pipe; the air inlet of the water-gas heat exchanger is connected to the high-pressure pipeline network natural gas pipeline; the exhaust port of the water-gas heat exchanger is connected to the air inlet of the expander through the natural gas inlet pipe; one end of the natural gas outlet pipe is connected to the air outlet of the expander, and the other end is connected to the subsequent process system. The high-adjustment water heating section pipeline and the high-adjustment water cooling section pipeline are respectively equipped with a first valve and a second valve at the high-adjustment water inlet and high-adjustment water outlet near the cooling water heat exchanger; One end of the water inlet pipe is connected to the water inlet of the water-air heat exchanger, and the other end is connected to the high-pressure water-heat section pipe between the first valve and the high-pressure scrubber. The water inlet pipe is equipped with a water inlet valve. One end of the drainage pipe is connected to the drain outlet of the water-air heat exchanger, and the other end is connected to the high-adjustment water-cooled section pipe between the second valve and the circulating water pump. A drainage pipe valve is also provided on the drainage pipe. The natural gas differential pressure power generation system also includes a bypass, wherein the bypass inlet end of the bypass is connected to the natural gas inlet pipeline, and the bypass outlet end of the bypass is connected to the natural gas outlet pipeline. A bypass valve is provided on the bypass; The natural gas differential pressure power generation system also includes a pressure reducing bypass pipeline. The gas inlet end of the pressure reducing bypass pipeline is connected to the natural gas inlet pipeline of the high-pressure pipeline network, and the gas outlet end of the pressure reducing bypass pipeline is connected to the natural gas outlet pipeline and is located between the bypass gas outlet end and the subsequent process system. The pressure-reducing bypass pipeline is equipped with a pressure-reducing valve.

2. The urea high-pressure regulating device waste heat coupled with natural gas pressure differential power generation system as described in claim 1, characterized in that: The natural gas expander is a turbine expander.

3. The urea high-pressure regulating device waste heat coupled with natural gas differential pressure power generation system as described in claim 1, characterized in that: The cooling water heat exchanger includes a high-adjustment water inlet connected to the high-adjustment hot section pipeline, a high-adjustment water outlet connected to the high-adjustment cold section pipeline, a cooling water inlet connected to the cooling water inlet pipeline, and a cooling water outlet connected to the cooling water outlet pipeline.

4. A method for operating a urea high-pressure regulating unit waste heat coupled with natural gas differential pressure power generation system as described in any one of claims 1-3, characterized in that, During normal power generation operation: The bypass valve is closed, the pressure reducing valve is closed, the first valve and the second valve are closed, and the inlet pipe valve and the drain pipe valve are opened, allowing the high-temperature, high-pressure water discharged from the high-pressure scrubber to enter the water-gas heat exchanger to release heat; the high-pressure natural gas absorbs waste heat and heats up in the water-gas heat exchanger; the heated natural gas enters the natural gas expander through the natural gas inlet pipe for expansion and power generation, and then enters the subsequent process system through the natural gas outlet pipe. When a natural gas expander experiences an emergency malfunction: Close the inlet and outlet valves, open the first and second valves, and close the natural gas expander and pressure reducing valve. At the same time, open the bypass valve to allow high-pressure natural gas to enter the natural gas outlet pipeline directly via the bypass. When the natural gas expander needs to be shut down for maintenance: Close the inlet and outlet valves, and open the first and second valves; close the natural gas expander and bypass valves; at the same time, open the pressure reducing valve to allow high-pressure natural gas to enter the natural gas outlet pipeline through the pressure reducing bypass pipeline.

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