Carbon dioxide expansion power generation system

Abstract

This application discloses a carbon dioxide expansion power generation system, relating to the field of energy recovery technology. Its key technical points are: it includes a first conveying pipeline for transporting carbon dioxide exhaust gas to subsequent processes, with a first valve installed on the first conveying pipeline; characterized in that: a second conveying pipeline is connected in parallel to one side of the first conveying pipeline, with the connection points of the two ends of the second conveying pipeline to the first conveying pipeline located upstream and downstream of the first valve, respectively; an expansion generator set is installed on the second conveying pipeline; when pressurized carbon dioxide exhaust gas flows through the expansion generator set, the expansion generator set can utilize the pressure in the carbon dioxide exhaust gas to generate electricity. This application utilizes the pressure energy of the gas expansion in the preceding and following processes to drive a runoff turbine to do work, thereby driving the generator within the unit to generate electricity. This not only reduces the waste of pressure energy but also saves on the electricity costs of enterprise production.

Description

Technical Field

[0001] This application relates to the field of energy recovery technology, and in particular to a carbon dioxide expansion power generation system. Background Technology

[0002] In chemical manufacturing, pressurized carbon dioxide is often produced. Companies typically use equipment such as carbon dioxide compressors to recover and reuse this pressurized carbon dioxide. However, it is common for the inlet design pressure of the first stage of the carbon dioxide compressor to be lower than the pressure of the carbon dioxide tail gas, or for the tail gas pressure to be higher than the pressure required for subsequent carbon dioxide processes. Taking the applicant's production line as an example, the inlet design pressure of the first stage of the applicant's carbon dioxide compressor is 58 kPa(G), while the pressurized carbon dioxide tail gas pressure from the low-temperature methanol washing unit in the purification section is approximately 200 kPa(G). Due to the significant expansion, the pressure reduction of the carbon dioxide gas is generally achieved by adjusting the valve opening on the compressor's inlet side pipeline (approximately 20%) to ensure the smooth operation of the carbon dioxide compressor. However, this results in a significant waste of pressure energy. Utility Model Content

[0003] This application provides a carbon dioxide expansion power generation system that can effectively utilize the excess pressure in carbon dioxide exhaust gas, thereby reducing energy waste.

[0004] The above-mentioned objective of this application is achieved through the following technical solution:

[0005] A carbon dioxide expansion power generation system includes a first conveying pipeline for transporting carbon dioxide exhaust gas to subsequent processes, a first valve installed on the first conveying pipeline, and a second conveying pipeline connected in parallel to one side of the first conveying pipeline.

[0006] The connection points between the two ends of the second delivery pipeline and the first delivery pipeline are located upstream and downstream of the first valve, respectively.

[0007] An expansion generator set is installed on the second delivery pipeline;

[0008] When pressurized carbon dioxide exhaust gas flows through the expansion generator set, the expansion generator set can generate electricity using the pressure in the carbon dioxide exhaust gas.

[0009] Furthermore, a second valve and a third valve are respectively installed on the second delivery pipeline upstream and downstream of the expansion generator set.

[0010] Furthermore, a third conveying pipeline is connected in parallel to the second conveying pipeline, and the two connection points of the third conveying pipeline and the second conveying pipeline are located upstream of the second valve and downstream of the third valve, respectively; a fourth valve is installed on the third conveying pipeline.

[0011] Furthermore, a fifth valve and a sixth valve are added to the second conveying pipeline. The fifth valve is located upstream of the connection point between the third conveying pipeline and the second conveying pipeline, and the sixth valve is located downstream of the connection point between the third conveying pipeline and the second conveying pipeline.

[0012] Furthermore, a heat exchanger is installed on the second delivery pipeline, and the heat exchanger is located upstream of the second valve on the second delivery pipeline.

[0013] Furthermore, the heat source for the heat exchanger comes from the existing steam condensate in the plant.

[0014] Furthermore, a seventh valve is installed on the inlet pipe of the heat exchanger, an eighth valve is installed on the outlet pipe of the heat exchanger, a short-connecting pipe is provided between the inlet pipe and the outlet pipe of the heat exchanger, the connection point of the short-connecting pipe to the inlet pipe of the heat exchanger is located upstream of the seventh valve, the connection point of the short-connecting pipe to the outlet pipe of the heat exchanger is located downstream of the eighth valve, and a ninth valve is installed on the short-connecting pipe.

[0015] In summary, this application includes at least one of the following beneficial technical effects:

[0016] In this application, the second conveying pipeline is connected in parallel with the first conveying pipeline. After the first valve on the first conveying pipeline is closed, the carbon dioxide expansion generator set on the second conveying pipeline can replace the first valve (i.e., the inlet pressure reducing valve) on the original first conveying pipeline. When the high-pressure carbon dioxide exhaust gas passes through the expansion generator set, the unit can use the pressure energy of the gas expansion in the upstream and downstream sections to drive the runoff turbine to do work, thereby driving the generator in the unit to generate electricity. This not only realizes the conversion of high-pressure carbon dioxide exhaust gas into the carbon dioxide required for subsequent processes during the conveying of carbon dioxide exhaust gas, but also converts the pressure energy released during the carbon dioxide pressure change process into electricity for the enterprise's use. This not only reduces the waste of pressure energy, but also saves the enterprise's electricity costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a system diagram of a second transmission pipeline connected in parallel to the first transmission pipeline, which includes an expansion generator set.

[0019] Figure 2 Is Figure 1 The system diagram after adding a third delivery pipeline and related equipment to the existing system;

[0020] Figure 3 Is Figure 2 The system diagram is shown below (i.e., the overall structural diagram of this application) after a heat exchanger is further added to the second delivery pipeline.

[0021] Reference numerals in the attached diagram: 1. First conveying pipeline; 2. First valve; 3. Second conveying pipeline; 4. Expansion generator set; 5. Second valve; 6. Third valve; 7. Third conveying pipeline; 8. Fourth valve; 9. Fifth valve; 10. Sixth valve; 11. Heat exchanger; 12. Seventh valve; 13. Eighth valve; 14. Ninth valve. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0023] like Figure 1 The image shows a carbon dioxide expansion power generation system disclosed in this application, including a first conveying pipeline 1 for conveying carbon dioxide exhaust gas to subsequent processes. A first valve 2 is installed on the first conveying pipeline 1, and a second conveying pipeline 3 is connected in parallel to one side of the first conveying pipeline 1.

[0024] The connection points between the two ends of the second conveying pipeline 3 and the first conveying pipeline 1 are located upstream and downstream of the first valve 2, respectively.

[0025] An expansion generator set 4 is installed on the second transmission pipeline 3;

[0026] When pressurized carbon dioxide exhaust gas flows through expander generator set 4, expander generator set 4 can use the pressure in the carbon dioxide exhaust gas to generate electricity.

[0027] In the above embodiments, the expander generator set 4 of this application comprises at least the following components: a generator set main unit, a grid-connected electrical system, and an instrumentation and control system. The generator set main unit is a skid-mounted integrated device, integrating a high-speed run-of-river turbine expander, a high-speed gear reducer, a flexible coupling, an asynchronous generator, a motor shaft brake, a lubrication and cooling system, and pipeline, valve, flow, pressure, and temperature monitoring systems on the skid-mounted base. This product is preferably a product from Tianjin Fast Turbine Technology Development Co., Ltd. The high-voltage grid-connected system includes a grid-connected cabinet combining a PT (potential transformer) and a switch. This system connects the power generated by the expander generator set 4 to the plant's power grid for enterprise use, employing a standard high-voltage electrical cabinet type. The PT cabinet is equipped with an isolating switch and measuring instruments. The upper port of the switch is connected to the busbar, and the lower port is connected to the switch cabinet, which is connected to the generator. The high-voltage switch cabinet is equipped with a comprehensive generator protection device, providing overload, overcurrent, short-circuit, three-stage inverse-time current protection, and overvoltage and undervoltage protection. The instrument control system consists of detection instruments and control instruments. After being connected to the factory's DCS system, the generator set's data acquisition, data display, data calculation, automatic and manual instrument control, fault alarms, and data recording can be completed on the industrial control computer in the main control room. All of the above are existing technologies well-known to those skilled in the art when using the expander generator set 4, and related details will not be elaborated further here.

[0028] The first delivery pipeline 1 is the original carbon dioxide tail gas delivery pipeline. Pressurized carbon dioxide tail gas can be input into the subsequent carbon dioxide tail gas treatment process through the first delivery pipeline 1. Taking the applicant's company as an example, the core equipment in the subsequent carbon dioxide tail gas treatment process is a carbon dioxide compressor. The first valve 2 on the first delivery pipeline 1 is the original pressure reducing valve, mainly used to reduce the pressure of the carbon dioxide tail gas from the purification section, ensuring that it meets the inlet design pressure requirements when sent to the carbon dioxide compressor. The power generation system of this application, while retaining the original first delivery pipeline 1, connects a second delivery pipeline 3 in parallel. An expansion generator set 4 is installed on the second delivery pipeline 3. When the expansion generator set 4 is operating normally, the first valve 2 is closed, and the first delivery pipeline 1 is disconnected. All the pressurized carbon dioxide tail gas will first utilize the pressure energy of the gas expansion in the preceding and following sections at the expansion generator set 4 to drive the runoff turbine to do work, driving the generator to generate electricity, thus converting the pressure energy lost during the original throttling process into electricity. Then, the electricity is transmitted to the plant's power grid through the grid-connected system in the expansion generator set 4 for the company's production use. The carbon dioxide expansion power generation system of this application can not only convert high-pressure carbon dioxide tail gas into carbon dioxide at the pressure required by the subsequent processes during the transmission of carbon dioxide tail gas to the subsequent processes, but also convert the pressure energy released during the carbon dioxide pressure change process into electricity for the company's use. This not only reduces the waste of pressure energy, but also saves the company's electricity costs.

[0029] Furthermore, such as Figure 1 As shown, a second valve 5 and a third valve 6 are installed on the second delivery pipeline 3 upstream and downstream of the expansion generator set 4, respectively.

[0030] In the above embodiments, the second valve 5 is a regulating valve, which can not only regulate the flow rate of pressurized carbon dioxide into the expander generator set 4, but also temporarily shut down the generator set 4 by closing the second valve 5 upstream of the expander generator set 4. The third valve 6 is a shut-off valve. After the on-site technicians close the second valve 5 and the third valve 6 at the same time, the expander generator set 4 can be completely isolated, which facilitates the workers to troubleshoot and perform routine maintenance on the generator set.

[0031] Furthermore, such as Figure 2 As shown, a third conveying pipeline 7 is connected in parallel to the second conveying pipeline 3. The two connection points of the third conveying pipeline 7 and the second conveying pipeline 3 are located upstream of the second valve 5 and downstream of the third valve 6, respectively. A fourth valve 8 is installed on the third conveying pipeline 7.

[0032] In the above embodiments, if the residual pressure generator set experiences a major fault and needs to be shut down, and the first valve 2 on the first delivery pipeline 1 malfunctions, on-site technicians can open the fourth valve 8 (a regulating valve) on the newly added third delivery pipeline 7. When the fourth valve 8 is opened to the predetermined position, the second valve 5 before the expander generator set 4 is closed. This also achieves the effect of delivering carbon dioxide exhaust gas to subsequent processes when the expander unit is temporarily shut down. This makes the process of delivering pressurized carbon dioxide exhaust gas to subsequent processes safer and more reliable.

[0033] Furthermore, such as Figure 2 As shown, a fifth valve 9 and a sixth valve 10 are added to the second conveying pipeline 3. The fifth valve 9 is located upstream of the connection point between the third conveying pipeline 7 and the second conveying pipeline 3 on the second conveying pipeline 3, and the sixth valve 10 is located downstream of the connection point between the third conveying pipeline 7 and the second conveying pipeline 3 on the second conveying pipeline 3.

[0034] In the above embodiments, the fifth valve 9 and the sixth valve 10 of this application are both shut-off valves. When it is necessary to isolate the second delivery pipeline 3 and the third delivery pipeline 7 from the first delivery pipeline 1 at the same time, the fifth valve 9 and the sixth valve 10 can be closed to achieve this effect, which can improve the flexibility of the power generation system of this application in use.

[0035] Furthermore, such as Figure 3 As shown, a heat exchanger 11 is installed on the second delivery pipeline 3, and the heat exchanger 11 is located upstream of the second valve 5 on the second delivery pipeline 3.

[0036] In the above embodiments, after the pressurized carbon dioxide exhaust gas expands and performs work in the expander generator set 4, the internal energy of the exhaust gas decreases, and the temperature drops below zero. This not only fails to meet the gas temperature requirements of the subsequent units, but also causes condensation or even ice formation on the outside of the exhaust gas pipeline after the generator set. To solve this problem, this application adopts a method of heating the pressurized carbon dioxide exhaust gas using the heat exchanger 11 before it enters the heat exchanger 11.

[0037] In addition to the above methods, a heat exchanger 11 can also be installed at the outlet of the expander generator set 4 to heat up the low-temperature carbon dioxide output by the expander generator set 4. This method can also raise the temperature of the carbon dioxide tail gas at the outlet of the expander generator set 4 to the temperature required by the subsequent process.

[0038] Furthermore, such as Figure 3 As shown, the heat source for heat exchanger 11 comes from the existing steam condensate in the plant.

[0039] In the above embodiments, chemical production enterprises usually have readily available steam condensate. This steam condensate has a certain temperature. After introducing this steam condensate as a heat source into the heat exchanger 11, it can be used to heat the carbon dioxide tail gas flowing through the heat exchanger 11, so that the tail gas temperature at the outlet of the expansion generator set 4 is raised to the temperature required by the subsequent process. For example, when the applicant synthesizes urea from carbon dioxide and ammonia using the urea unit, it generates condensed steam at a temperature of 90°C. The flow rate and temperature of this condensed steam are sufficient to meet the process requirements for heating the carbon dioxide tail gas in the heat exchanger 11. In practice, after introducing the 90°C condensed steam from the urea unit into the heat exchanger 11, the carbon dioxide tail gas can be heated to 54°C. After passing through the power generation process in the expansion generator set 4, the carbon dioxide discharged from the expansion generator set 4 has a temperature of 16°C. In fact, as long as the carbon dioxide inlet temperature is stabilized at 15-18°C, the gas pumping volume of the carbon dioxide compressor unit in the subsequent process will no longer be affected by the air temperature. It can be seen that the 90°C condensed steam from the urea unit is sufficient to meet the temperature requirements for heating the carbon dioxide tail gas.

[0040] Furthermore, such as Figure 3 As shown, a seventh valve 12 is installed on the inlet pipe of heat exchanger 11, and an eighth valve 13 is installed on the outlet pipe of heat exchanger 11. A short-connecting pipe is provided between the inlet pipe and the outlet pipe of heat exchanger 11. The connection point of the short-connecting pipe to the inlet pipe of heat exchanger 11 is located upstream of the seventh valve 12, and the connection point of the short-connecting pipe to the outlet pipe of heat exchanger 11 is located downstream of the eighth valve 13. A ninth valve 14 is installed on the short-connecting pipe.

[0041] In the above embodiments, the seventh valve 12 on the inlet pipe of the heat exchanger 11 is a regulating valve, the eighth valve 13 installed on the outlet pipe of the heat exchanger 11 is a shut-off valve, and the ninth valve 14 installed on the short-connection pipe is a shut-off valve. The seventh valve 12 can not only regulate the flow rate of steam condensate entering the heat exchanger 11, but also temporarily interrupt the path of steam condensate flowing to the heat exchanger 11. When the heat exchanger 11 needs maintenance, closing the seventh valve 12 and the eighth valve 13 and opening the ninth valve 14 allows the steam condensate to flow directly elsewhere without passing through the heat exchanger 11, while simultaneously isolating the heat exchanger 11 to facilitate maintenance and other operations by on-site technicians.

[0042] The implementation principle of this embodiment is as follows: Before use, after the worker checks that the expander generator set 4 is normal, the first valve 2 and the fourth valve 8 can be closed, allowing all the pressurized carbon dioxide exhaust gas to flow along the second conveying pipeline 3 through the expander generator set 4 before being input into the subsequent processes. When the high-pressure carbon dioxide exhaust gas passes through the expander generator set 4, the unit can utilize the pressure energy of the gas expansion in the preceding and following sections to drive the runoff turbine to do work, thereby driving the generator in the unit to generate electricity. This not only realizes the conversion of high-pressure carbon dioxide exhaust gas into the required pressure carbon dioxide during the process of transporting the carbon dioxide exhaust gas to the subsequent processes, but also converts the pressure energy released during the carbon dioxide pressure change process into electricity, which is then transmitted to the plant's power grid for production use through the grid-connected cabinet. This not only reduces the waste of pressure energy but also saves the company's electricity costs.

[0043] When the expander generator set 4 needs to be shut down due to a malfunction, the worker can open the first valve 2. When the first valve 2 is opened to its normal operating position, the worker can then close the second valve 5 upstream of the expander generator set 4 to shut it down. If the first valve 2 malfunctions and cannot be opened, the worker can open the fourth valve 8. When the fourth valve 8 is opened to its predetermined position, the first valve 2 can be closed to shut down the expander generator set 4.

[0044] When the expander generator set 4 requires maintenance, workers can completely close the second valve 5 and the third valve 6 upstream and downstream of the expander generator set 4. This completely isolates the expander generator set 4 from the pressurized carbon dioxide exhaust gas, facilitating troubleshooting and routine maintenance. During unit maintenance, to ensure safety and prevent minor leaks in the aforementioned two valves, the fourth valve 8, the fifth valve 9, and the sixth valve 10 can also be closed.

[0045] After pressurized carbon dioxide expands and performs work in the expander generator set 4, the temperature of the carbon dioxide exhaust gas discharged from the expander generator set 4 not only fails to meet the gas temperature requirements of subsequent processes, but also causes condensation or even ice formation on the exterior of the exhaust gas pipeline downstream of the expander generator set 4. This application addresses this by adding a heat exchanger 11 upstream of the expander generator set 4 to increase the temperature of the exhaust gas at the outlet of the expander generator set 4, ensuring that the exhaust gas temperature at the unit outlet meets the requirements of subsequent processes. The heat exchanger 11 in this application is preferably a shell-and-tube heat exchanger 11, and the heat source is existing steam condensate from the factory. This allows for full utilization of the temperature in the existing steam condensate, ensuring that the carbon dioxide exhaust gas temperature at the outlet of the expander generator set 4 meets the requirements of subsequent processes.

[0046] After the system is actually put into operation on the applicant's production line, assuming an annual working time of 350 days and a net power generation of 440kW, and an electricity price of 0.5 yuan / kWh based on the local comprehensive electricity price, the carbon dioxide expansion power generation system proposed in this application can bring the company approximately 1.76 million yuan in revenue per year. Converting the electricity generated from the pressure difference of carbon dioxide exhaust gas into standard coal equivalent, it can save approximately 1400 tons of standard coal per year, resulting in a corresponding reduction of approximately 3600 tons of carbon dioxide emissions. Therefore, it is evident that the system not only brings substantial benefits to the company but also achieves the beneficial effects of resource conservation and environmental protection.

[0047] The equipment purchase cost is approximately RMB 3.5 million, the material cost of pipelines, valves, cables, etc. is approximately RMB 754,000, the installation and civil engineering cost is approximately RMB 230,000, and the design fee is approximately RMB 30,000, totaling RMB 4.514 million. The system applied for can generate positive revenue for the enterprise in the third year of operation.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A carbon dioxide expansion power generation system, comprising a first conveying pipeline (1) for conveying carbon dioxide exhaust gas to subsequent processes, wherein a first valve (2) is installed on the first conveying pipeline (1), characterized in that: A second conveying pipeline (3) is connected in parallel to one side of the first conveying pipeline (1). The connection points between the two ends of the second conveying pipeline (3) and the first conveying pipeline (1) are located upstream and downstream of the first valve (2), respectively; An expansion generator set (4) is installed on the second delivery pipeline (3); When pressurized carbon dioxide exhaust gas flows through the expansion generator set (4), the expansion generator set (4) can generate electrical energy using the pressure in the carbon dioxide exhaust gas.

2. The carbon dioxide expansion power generation system according to claim 1, characterized by: A second valve (5) and a third valve (6) are installed on the second delivery pipeline (3) upstream and downstream of the expansion generator set (4), respectively.

3. The carbon dioxide expansion power generation system according to claim 2, characterized by: A third conveying pipeline (7) is connected in parallel to the second conveying pipeline (3). The two connection points of the third conveying pipeline (7) and the second conveying pipeline (3) are located upstream of the second valve (5) and downstream of the third valve (6), respectively. A fourth valve (8) is installed on the third conveying pipeline (7).

4. The carbon dioxide expansion power generation system according to claim 3, characterized by: A fifth valve (9) and a sixth valve (10) are added to the second conveying pipeline (3). The fifth valve (9) is located upstream of the connection point between the third conveying pipeline (7) and the second conveying pipeline (3) on the second conveying pipeline (3), and the sixth valve (10) is located downstream of the connection point between the third conveying pipeline (7) and the second conveying pipeline (3) on the second conveying pipeline (3).

5. The carbon dioxide expansion power generation system according to any one of claims 2 to 4, characterized by: A heat exchanger (11) is installed on the second delivery pipeline (3), and the heat exchanger (11) is located upstream of the second valve (5) on the second delivery pipeline (3).

6. The carbon dioxide expansion power generation system according to claim 5, characterized by: The heat source for the heat exchanger (11) comes from the existing steam condensate in the plant.

7. The carbon dioxide expansion power generation system according to claim 5, characterized by: A seventh valve (12) is installed on the inlet pipe of the heat exchanger (11), and an eighth valve (13) is installed on the outlet pipe of the heat exchanger (11). A short-connecting pipe is provided between the inlet pipe and the outlet pipe of the heat exchanger (11). The connection point of the short-connecting pipe with the inlet pipe of the heat exchanger (11) is located upstream of the seventh valve (12), and the connection point of the short-connecting pipe with the outlet pipe of the heat exchanger (11) is located downstream of the eighth valve (13). A ninth valve (14) is installed on the short-connecting pipe.

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