Compressor capable of pressurizing and injecting dense-phase carbon dioxide

Abstract

The invention discloses a compressor capable of pressurizing and injecting dense-phase carbon dioxide, and belongs to the field of carbon capture, utilization and storage. A second control valve, an emergency shut-off valve SDV1, a small-flow regulating valve PV1, a heater, an air inlet separator, an air inlet buffer tank, a compressor, an air exhaust buffer tank, a temperature control valve TV2, an air cooler, an air exhaust separator, a back pressure valve PV3 and an emergency shut-off valve SDV2 are sequentially connected, and finally the air is conveyed to an air injection system, wherein the emergency shut-off valve SDV1 and the small-flow regulating valve PV1 are connected in parallel. A tube pass inlet and outlet of the heat exchanger are connected with the left end and the right end of a second control valve through pipelines, a shell pass inlet and outlet of the heat exchanger are connected with the left end and the right end of a temperature control valve TV2 through pipelines, an inlet pipeline is provided with a temperature control valve TV1, and the left end of the air cooler is connected with the right end of the heater through a bypass valve BPV and a backflow adjusting valve PV2 which are connected in parallel. According to the method, the project engineering cost and energy consumption are reduced, and the economic benefits of the CCUS-EOR project are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon capture, utilization and storage, and specifically relates to a compressor capable of pressurizing and injecting dense phase carbon dioxide. The invention is applied to the field of pressurizing and injecting carbon dioxide into underground oil recovery after long-distance supercritical pipeline transportation. The invention is a process method in which the carbon dioxide medium transported by supercritical carbon dioxide pipeline still uses a compressor to pressurize the carbon dioxide medium after entering the dense phase area. Background Art

[0002] CCUS (Carbon Capture, Utilization and Storage) is a technology for carbon capture, utilization and storage. CCUS technology can store carbon dioxide emitted during the production process, or purify it and put it into a new production process for recycling. Among them, carbon dioxide recovery and oil storage (CCUS-EOR) has become the main method of carbon utilization and storage. It can improve the oil recovery rate while storing carbon dioxide. The additional crude oil produced makes carbon storage have better economic benefits. It is the only large-scale utilization and storage technology that can achieve near-zero carbon dioxide emissions from fossil energy output at this stage.

[0003] After carbon dioxide is captured at the carbon source, it is often far away from the injection site. Pipeline transportation becomes the most economical way of carbon transportation due to its large transportation volume and long transportation distance. Carbon dioxide pipeline transportation includes gas phase transportation, liquid phase transportation and supercritical transportation. For large-volume and long-distance transportation pipelines, supercritical transportation is generally used. Carbon dioxide high-pressure injection methods include liquid injection, supercritical injection and dense phase injection. When carbon dioxide is transported to the injection point by supercritical pipeline and then injected by supercritical method, there are the following problems: due to the low critical temperature of carbon dioxide when it is transported over a long distance in the pipeline, the supercritical phase will gradually change to a dense phase state as the temperature decreases. When the pipeline is transported to the end point, in order to avoid the physical property changes at different phases affecting the normal operation of the compressor, it is generally required that carbon dioxide deviates from the supercritical point to enter the supercritical compressor. This requires that the carbon dioxide in the dense phase state needs to be reheated to the supercritical state before it can be allowed to enter the compressor for pressurization. In response to the above problems, a high-power electric heater or heating furnace is generally used to heat the dense phase carbon dioxide to heat it up and enter the supercritical state. This method has the problems of high energy consumption and high operating costs. Summary of the invention

[0004] In order to solve the above-mentioned problems, the present invention proposes: a compressor that can pressurize and inject dense-phase carbon dioxide, the dense-phase carbon dioxide is input into the compressor skid group through a pipeline, and a first shut-off valve is arranged on the inlet pipeline of the compressor skid group, which is connected in sequence to the second control valve, the emergency shut-off valve SDV1 and the small flow regulating valve PV1 connected in parallel, the heater, the intake separator, the intake buffer tank, the compressor, the exhaust buffer tank, the temperature control valve TV2, the air cooler, the exhaust separator, the back pressure valve PV3 and the emergency shut-off valve SDV2, and finally transported to the gas injection system, the tube-side inlet and outlet of the heat exchanger are connected to the left and right ends of the second control valve through a pipeline, the shell-side inlet and outlet of the heat exchanger are connected to the left and right ends of the temperature control valve TV2 through a pipeline, the inlet pipeline is provided with the temperature control valve TV1, and the left end of the air cooler is connected to the right end of the heater through the bypass valve BPV and the reflux regulating valve PV2 connected in parallel.

[0005] Furthermore, the compressor inlet stream and outlet stream enter the tube side and shell side of the heat exchanger respectively, and the compressor outlet hot stream first enters the heat exchanger to heat the inlet cold stream before going to the air cooler.

[0006] Furthermore, the compressor inlet flow is 8MPa, 20℃, and the outlet pressure is 20MPa. When the compressor is in the first stage of compression, the outlet temperature is about 115℃. After setting the inlet and outlet heat exchangers, the inlet flow temperature can be increased to 40℃ to ensure that the compressor inlet temperature requirements are met.

[0007] Furthermore, when the compressor adopts multi-stage compression, it enters the next stage of compression without inter-stage cooling to ensure the temperature of the outlet medium of the last stage. If the temperature of the medium entering the next stage exceeds the maximum temperature allowed by the specification, it can enter the cooler to be cooled to the maximum temperature allowed before entering the next stage.

[0008] Furthermore, when the compressor outlet pressure is low and the compression heat is insufficient to heat the inlet stream temperature to above 40° C., a heater or heating furnace is provided after the heat exchanger as a supplement.

[0009] Furthermore, a compressor startup small flow heater is provided in the compressor skid assembly for heating the inlet flow stream when the compressor is started. The heater is only used when the compressor is started and can be stopped after the compressor is operating normally.

[0010] Furthermore, the low temperature start-up process of the supercritical compressor is as follows:

[0011] ① Compressor reflux status: compressor reflux regulating valve PV2 is fully open, bypass valve BPV is open, temperature control valve TV1 is open, and other control valves are closed;

[0012] ② Small flow heating intake warm-up: Open the first shut-off valve, the second control valve, the small flow electric heater and the small flow regulating valve PV1 at the inlet, heat the inlet stream to 80°C, charge the compressor system to 0.3-0.4MPaG, close PV1, and warm up the compressor device and the inlet and outlet heat exchangers;

[0013] ③Start the machine at the minimum flow rate to increase the system temperature: Start the main motor, and the speed reaches the minimum allowable speed when the compressor is under low load. Gradually open PV1, slowly inject air into the system, and at the same time close the bypass return valve BPV, gradually reduce the return regulating valve PV2, slowly increase the compressor outlet pressure, monitor the fluid temperature in the system, and when it rises to 45°C, gradually reduce the heater power to keep the temperature at the front end of the compressor in the system at 45-50°C. When the pressure in the compressor unit system rises to 8MPaG, open SDV1, and close PV1 and the second control valve at the inlet.

[0014] Furthermore, it also includes: ④ A back pressure valve PV3 is set at the outlet of the compressor. When the downstream pressure of the compressor does not reach the set gas injection pressure, or the outlet pressure of the compressor does not reach the pressure to ensure sufficient compression heat in a short period of time, the minimum back pressure of the compressor is set to ensure the compression heat: SDV2 is opened, the back pressure valve is set to the minimum outlet pressure to ensure that the inlet flow can be heated to 40°C, and the reflux regulating valve PV2 is gradually reduced to fully closed. When the pressure before the back pressure valve rises to the set pressure, the heater is completely closed;

[0015] ⑤ When the pressure behind the monitored back pressure valve PV3 reaches the set pressure, fully open the back pressure valve PV3 and adjust the speed of the main motor to the full load operating speed of the compressor.

[0016] The beneficial effects of the present invention are:

[0017] (1) Based on the fact that the gas injection pressure of CCUS-EOR projects in various oil fields is generally high and the compression process of the gas injection compressor generates a large amount of compression heat, the compression heat of the gas injection compressor is fully utilized to save the energy consumption of heating the dense phase carbon dioxide to a supercritical state by an electric heater or a heating furnace and then sending it to the compressor for pressurization;

[0018] (2) The inlet and outlet streams of the gas injection compressor are the same stream, the heat exchange process is simple, and when the gas injection pressure is constant, the compression heat required for heat exchange is stable and guaranteed;

[0019] (3) Using the compression heat of the gas injection compressor to heat the inlet stream can also greatly reduce the load of the compressor outlet cooler and save cooler energy consumption;

[0020] (4) Currently, carbon dioxide high-pressure injection compressors do not allow dense-phase carbon dioxide to directly enter the compressor for pressurization. It must be heated to a supercritical state in advance before entering the compressor. After adopting the present invention, it can be achieved under specific working conditions that dense-phase carbon dioxide directly enters the compressor skid group for pressurization and injection.

[0021] (5) The present invention can save the investment in electric heaters or heating furnaces required for directly heating dense phase carbon dioxide to a supercritical state, thereby reducing project engineering costs. At the same time, the energy savings can significantly reduce the annual operating costs of the project, thereby increasing the economic benefits of the CCUS-EOR project. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic diagram of the compressor flow chart for pressurizing and injecting dense phase carbon dioxide. DETAILED DESCRIPTION

[0023] In order to make the technical means and objectives of the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments. A compressor capable of pressurizing and injecting dense phase carbon dioxide, such as Figure 1 As shown, dense phase carbon dioxide is input to the compressor skid through a pipeline. A first shut-off valve is arranged on the inlet pipeline of the compressor skid, which is connected in sequence to the second control valve, the emergency shut-off valve SDV1 and the small flow regulating valve PV1 connected in parallel, the heater, the air intake separator, the air intake buffer tank, the compressor, the exhaust buffer tank, the temperature control valve TV2, the air cooler, the exhaust separator, the back pressure valve PV3 and the emergency shut-off valve SDV2, and finally transported to the gas injection system. The pipe side inlet and outlet of the heat exchanger are connected to the left and right ends of the second control valve through a pipeline, and the shell side inlet and outlet of the heat exchanger are connected to the left and right ends of the temperature control valve TV2 through a pipeline (the temperature control valve TV1 is arranged on the inlet pipeline), and the left end of the air cooler is connected to the right end of the heater through the bypass valve BPV and the reflux regulating valve PV2 connected in parallel.

[0024] (1) A shell and tube heat exchanger is set in the compressor skid. The inlet and outlet streams of the compressor enter the tube side and shell side of the heat exchanger respectively. The hot stream at the outlet of the compressor enters the heat exchanger to heat the inlet cold stream before going to the air cooler. Generally, the pressure of carbon dioxide transported to the terminal gas injection station in a supercritical state is greater than the supercritical pressure (generally ≥8MPa), and the temperature drops to about 20°C; according to the statistics of gas injection pressure in carbon dioxide drive blocks currently carried out in China, the general wellhead reinjection pressure is about 20MPa. Therefore, a large amount of compression heat is generated during the compression process of the compressor. Taking the inlet stream of 8MPa, 20°C, and outlet pressure of 20MPa as an example, when the compressor is compressed in the first stage, the outlet temperature is about 115°C. After the inlet and outlet heat exchangers are set, the inlet stream temperature can be increased to 40°C to ensure that the compressor inlet temperature requirement is met.

[0025] (2) If the compressor adopts multi-stage compression, it should enter the next stage of compression without inter-stage cooling to ensure the temperature of the medium at the outlet of the last stage. If the temperature of the medium entering the next stage exceeds the maximum temperature allowed by the specification or the manufacturer, it can enter the cooler to cool to the maximum temperature allowed before entering the next stage.

[0026] (3) If the compressor outlet pressure is low and the compression heat is insufficient to heat the inlet stream temperature to above 40°C, an electric heater or heating furnace can be installed after the heat exchanger as a supplement.

[0027] (4) A compressor startup low-flow electric heater is installed in the compressor skid to heat the inlet flow stream when the compressor is started. The electric heater is only used when the compressor is started and can be stopped after the compressor is running normally. The power calculation of the electric heater is based on the minimum flow rate allowed when the compressor is started to heat the flow stream to 80°C.

[0028] The low temperature start-up process of supercritical compressor is as follows:

[0029] ① Compressor reflux status: compressor reflux regulating valve PV2 is fully open, bypass valve BPV is open, temperature control valve TV1 is open, and other control valves are closed;

[0030] ② Small flow heating intake warm-up: Open the first shut-off valve, the second control valve, the small flow electric heater and the small flow regulating valve PV1 at the inlet, heat the inlet stream to 80°C, charge the compressor system to 0.3-0.4MPaG, close PV1, and warm up the compressor device and the inlet and outlet heat exchangers;

[0031] ③Start the machine at the minimum flow rate to increase the system temperature: Start the main motor, and the speed reaches the minimum allowable speed of the compressor under low load. Gradually open PV1, slowly inject gas into the system, and at the same time close the bypass return valve BPV, gradually reduce the return regulating valve PV2, slowly increase the compressor outlet pressure, monitor the fluid temperature in the system, and when it rises to 45°C, gradually reduce the heater power to keep the temperature at the front end of the compressor in the system at 45-50°C. When the pressure in the compressor unit system rises to 8MPaG, open SDV01, and close PV1 and the second control valve at the inlet;

[0032] ④ Set a back pressure valve PV3 at the compressor outlet. When the compressor downstream pressure does not reach the set gas injection pressure, or the compressor outlet pressure does not reach the pressure to ensure sufficient compression heat in a short period of time, set the compressor minimum back pressure to ensure compression heat: open SDV2, set the back pressure valve pressure to ensure the minimum outlet pressure that can heat the inlet stream to 40°C, gradually reduce the reflux regulating valve PV2 to fully closed, and when the pressure before the back pressure valve rises to the set pressure, completely close the heater;

[0033] ⑤ When the pressure behind the monitored back pressure valve PV3 reaches the set pressure, fully open the back pressure valve PV3 and adjust the speed of the main motor to the full load operating speed of the compressor.

[0034] To address the problem that carbon dioxide cannot directly enter the downstream supercritical compressor for pressurization when its phase changes to dense phase during supercritical pipeline transportation, and the conventional solutions such as using electric heaters or heating furnaces to directly heat the dense phase carbon dioxide to a supercritical state have high energy consumption and operating costs, we have developed a compressor that can pressurize and inject dense phase carbon dioxide, so as to simplify the process and save energy.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A compressor capable of pressurizing and injecting dense phase carbon dioxide, characterized in that: Dense phase carbon dioxide is input into the compressor skid through a pipeline. A first shut-off valve is arranged on the inlet pipeline of the compressor skid, which is connected in sequence to the second control valve, the emergency shut-off valve SDV1 and the small flow regulating valve PV1 connected in parallel, the heater, the air intake separator, the air intake buffer tank, the compressor, the exhaust buffer tank, the temperature control valve TV2, the air cooler, the exhaust separator, the back pressure valve PV3 and the emergency shut-off valve SDV2, and finally transported to the gas injection system. The pipe side inlet and outlet of the heat exchanger are connected to the left and right ends of the second control valve through a pipeline, and the shell side inlet and outlet of the heat exchanger are connected to the left and right ends of the temperature control valve TV2 through a pipeline. The temperature control valve TV1 is arranged on the inlet pipeline, and the left end of the air cooler is connected to the right end of the heater through the bypass valve BPV and the reflux regulating valve PV2 connected in parallel.

2. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 1, characterized in that: The compressor inlet stream and outlet stream enter the tube side and shell side of the heat exchanger respectively. The compressor outlet hot stream first enters the heat exchanger to heat the inlet cold stream before going to the air cooler.

3. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 2, characterized in that: The compressor inlet stream is 8MPa, 20℃, and the outlet pressure is 20MPa. When the compressor is in the first stage of compression, the outlet temperature is about 115℃. After installing the inlet and outlet heat exchangers, the inlet stream temperature can be increased to 40℃ to ensure that the compressor inlet temperature requirements are met.

4. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 1, characterized in that: When the compressor adopts multi-stage compression, it enters the next stage of compression without inter-stage cooling to ensure the temperature of the outlet medium of the last stage. If the temperature of the medium entering the next stage exceeds the maximum temperature allowed by the specification, it can enter the cooler to be cooled to the maximum temperature allowed before entering the next stage.

5. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 1, characterized in that: When the compressor outlet pressure is low and the compression heat is not enough to heat the inlet stream temperature to above 40°C, a heater or heating furnace is installed after the heat exchanger as a supplement.

6. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 1, characterized in that: A compressor startup small flow heater is installed in the compressor skid to heat the inlet flow when the compressor is started. The heater is only used when the compressor is started and can be stopped after the compressor is running normally.

7. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 1, characterized in that: The low temperature start-up process of supercritical compressor is as follows: ① Compressor reflux status: compressor reflux regulating valve PV2 is fully open, bypass valve BPV is open, temperature control valve TV1 is open, and other control valves are closed; ② Small flow heating intake warm-up: Open the first shut-off valve, the second control valve, the small flow electric heater and the small flow regulating valve PV1 at the inlet, heat the inlet stream to 80°C, charge the compressor system to 0.3-0.4MPaG, close PV1, and warm up the compressor device and the inlet and outlet heat exchangers; ③Start the machine at the minimum flow rate to increase the system temperature: Start the main motor, and the speed reaches the minimum allowable speed when the compressor is under low load. Gradually open PV1, slowly inject air into the system, and at the same time close the bypass return valve BPV, gradually reduce the return regulating valve PV2, slowly increase the compressor outlet pressure, monitor the fluid temperature in the system, and when it rises to 45°C, gradually reduce the heater power to keep the temperature at the front end of the compressor in the system at 45-50°C. When the pressure in the compressor unit system rises to 8MPaG, open SDV1, and close PV1 and the second control valve at the inlet.

8. The compressor capable of pressurizing and injecting dense phase carbon dioxide according to claim 7, characterized in that: Also includes: ④ Set a back pressure valve PV3 at the compressor outlet. When the compressor downstream pressure does not reach the set gas injection pressure, or the compressor outlet pressure does not reach the pressure to ensure sufficient compression heat in a short period of time, set the compressor minimum back pressure to ensure compression heat: open SDV2, set the back pressure valve pressure to ensure the minimum outlet pressure that can heat the inlet stream to 40°C, gradually reduce the reflux regulating valve PV2 to fully closed, and when the pressure before the back pressure valve rises to the set pressure, completely close the heater; ⑤ When the pressure behind the monitored back pressure valve PV3 reaches the set pressure, fully open the back pressure valve PV3 and adjust the speed of the main motor to the full load operating speed of the compressor.

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