Heat exchange system for preventing sulfur dioxide dew point corrosion

Abstract

The utility model provides a heat exchange system of preventing sulfur dioxide dew point corrosion, including heat exchanger (1), heat exchanger (1) has the heat side inlet pipeline (2) and heat side outlet pipeline (3), and cold side inlet pipeline (4) and cold side outlet pipeline (5), concentration detector (6), concentration control valve (7), temperature sensor (8), external pipeline valve (9) and external pipeline (10). The heat exchange system of the utility model effectively prevents the occurrence of sulfur dioxide dew point corrosion, reduces the cost and improves production efficiency, reduces the potential safety hazard, ensures the long-term normal stable safe production of production device.

Description

Technical Field

[0001] This utility model relates to the field of corrosion prevention technology for heat exchangers used in the recovery of sulfur-containing natural gas tail gas, specifically to a heat exchange system for preventing sulfur dioxide dew point corrosion. Background Technology

[0002] The development and production of high-sulfur natural gas fields generates large amounts of H2S gas. Besides being harmful to human health, H2S gas also causes environmental pollution upon contact with the atmosphere, such as dissolving in rainwater to form acid rain. We typically need to treat H2S gas from natural gas, and to do so, we usually use a tail gas absorption tower to minimize its emissions. The tail gas from the top of the absorption tower enters a tail gas incinerator, where it mixes and burns with external fuel gas and air. The air required for combustion is supplied by the incinerator's blower. The remaining H2S and other sulfides in the tail gas are burned in the incinerator and converted into SO2. Other combustibles such as hydrocarbons, hydrogen, and CO are also completely oxidized simultaneously. The high-temperature flue gas leaving the furnace enters the tail gas incinerator's heat recovery system, where heat is recovered by generating low-pressure saturated steam. The flue gas exiting the heat recovery system enters the flue gas desulfurization system. The flue gas from the waste heat boiler first exchanges heat with purified flue gas from the scrubbing tower through a flue gas heat exchanger. After the temperature drops to about 170℃, it is further cooled by water spraying and then enters the scrubbing tower, where SO2 in the flue gas is absorbed by a 30% sodium hydroxide solution. The SO2 concentration in the flue gas after alkaline scrubbing is ≤50mg / Nm³. 3 The exhaust gas is heated to 180°C by a tail gas heat exchanger before being discharged through a chimney. The saline wastewater (sodium sulfate) generated after alkaline washing is sent to a comprehensive water recovery unit.

[0003] Due to the currently low outlet temperature of the heat exchanger, the outlet of the sulfur dioxide dew point heat exchanger is susceptible to liquefaction corrosion by sulfur-containing substances. Furthermore, the current E-411 heat exchanger, due to material limitations, has poor corrosion resistance, making it a weak link in the exhaust gas recovery system. The large amount of sulfur-containing corrosion products generated during exhaust gas treatment continuously erodes the sulfur dew point area of ​​the heat exchanger over time. Excessive corrosion not only reduces production efficiency but also poses safety hazards.

[0004] Therefore, there is an urgent need in this field to improve the corrosion resistance of heat exchangers in exhaust gas recovery, thereby effectively solving the corrosion problem faced by heat exchangers and ensuring the stable operation and efficient output of the system. Utility Model Content

[0005] The purpose of this invention is to solve the problem of sulfur dioxide dew point corrosion at the heat exchanger outlet, overcoming the current shortcomings of sulfur dioxide corrosion at the hot-side outlet due to low outlet temperature, and providing a heat exchange system that prevents sulfur dioxide dew point corrosion. This heat exchange system can effectively prevent sulfur dioxide dew point corrosion, reduce costs, improve production efficiency, reduce safety hazards, and ensure long-term normal, stable, and safe production of the production unit.

[0006] This invention provides a heat exchange system for preventing sulfur dioxide dew point corrosion, comprising:

[0007] A heat exchanger having a hot-side inlet pipeline and a hot-side outlet pipeline for the gas to be treated, and a cold-side inlet pipeline and a cold-side outlet pipeline for the cooling medium; a concentration detector, installed on the hot-side inlet pipeline, for detecting the concentration of sulfur dioxide in the gas to be treated entering the heat exchanger; and a concentration control valve, installed on the hot-side inlet pipeline and upstream of the concentration detector, having a nitrogen pipeline for connection to a nitrogen source, and communicatively connected to the concentration detector to adjust the amount of sulfur dioxide entering the gas according to the sulfur dioxide concentration measured by the concentration detector. The system includes: a nitrogen level in the outlet pipeline; a temperature sensor installed on the hot-side outlet pipeline to measure the temperature of the gas in the hot-side outlet pipeline; an external pipeline and an external pipeline valve, wherein the external pipeline valve is installed on the hot-side inlet pipeline and upstream of the concentration control valve, one end of the external pipeline is connected to the hot-side inlet pipeline via the external pipeline valve, and the other end is connected to the hot-side outlet pipeline; the external pipeline valve is communicatively connected to the temperature sensor to adjust the connection or disconnection of the external pipeline according to the temperature measured by the temperature sensor to control the temperature of the gas in the hot-side outlet pipeline.

[0008] This invention relates to a heat exchange system for preventing sulfur dioxide dew point corrosion. By adding a concentration detector and a temperature sensor, it monitors the concentration of sulfur dioxide in the gas at the hot-side inlet pipeline and the temperature of the gas at the hot-side outlet pipeline in real time. If the sulfur dioxide concentration in the gas at the hot-side inlet pipeline is too high, the concentration control valve is adjusted based on the concentration measured by the detector. The valve opens, adjusting the amount of nitrogen entering the hot-side inlet pipeline, thereby reducing the sulfur dioxide concentration entering the heat exchanger, and consequently decreasing the sulfur dioxide concentration in the gas at the hot-side outlet pipeline. If the temperature of the gas at the hot-side outlet pipeline is detected to be lower than the sulfur dioxide dew point, the external pipeline valve is adjusted based on the temperature measured by the temperature sensor. The external pipeline valve opens, mixing the high-temperature gas (not cooled by the heat exchanger) with the cooled gas, raising the temperature of the gas at the hot-side outlet pipeline, thus ensuring that the gas temperature is above the dew point. This heat exchange system, through a series of adjustments, effectively prevents sulfur dioxide dew point corrosion, reduces costs, improves production efficiency, reduces safety hazards, and ensures long-term normal, stable, and safe production of the equipment.

[0009] Optionally, the heat exchange system further includes a tail gas scrubbing tower, the inlet of which is connected to the hot-side outlet pipeline, and the outlet of which is connected to the cold-side inlet pipeline. The tail gas scrubbing tower is used to receive the heat-exchanged gas from the hot-side outlet pipeline and the gas from the external pipeline, and to desulfurize the gas through physical absorption or chemical reaction.

[0010] Optionally, the tail gas scrubbing tower is equipped with a packing layer and a spraying device. This improves the desulfurization efficiency of the tail gas scrubbing tower. In particular, the packing layer provides a larger gas-liquid contact area, which helps in the absorption of sulfur dioxide; the spraying device ensures uniform distribution of the desulfurization liquid, improving reaction efficiency. These features significantly enhance the desulfurization efficiency of the tail gas scrubbing tower, further reducing the emission concentration of sulfur dioxide. This not only contributes to environmental protection but also prevents equipment corrosion due to prolonged contact with high concentrations of sulfur dioxide, extending the equipment's service life. To achieve the recycling of the heat exchange system, the gas treated by the tail gas scrubbing tower is used as a cooling medium, entering the heat exchanger through the cold-side inlet pipeline and then exiting through the cold-side outlet pipeline. This not only improves the system's energy utilization efficiency but also allows heat to be recovered for use in other processes, maximizing resource utilization.

[0011] Optionally, the external pipeline further includes at least one branch pipeline, on which a flow control device is provided.

[0012] To precisely control the gas flow rate in the external pipeline, multiple branch pipes and multiple flow control devices can be installed on the external pipeline. These branch pipes can be selectively connected as needed, and a problem in one branch pipe will not affect the overall operation of the external pipeline. Multiple flow control devices can adjust the gas flow rate as required, providing more flexibility to cope with various operating conditions and improving the stability and reliability of the system.

[0013] Optionally, the heat exchange system further includes a data recording and analysis module. The concentration detector and the temperature sensor are both communicatively connected to the data recording and analysis module. The data recording and analysis module receives and processes signals from the concentration detector and the temperature sensor, and sends instructions to the concentration control valve and the external pipeline valve according to the signal processing results to adjust the opening and closing of the concentration control valve and the external pipeline valve.

[0014] To achieve intelligent control of the heat exchange system, a data recording and analysis module was introduced. This module can receive and process signals from the concentration detector and temperature sensor, and send instructions to the concentration control valve and external pipeline valves based on the signal processing results. This enables the system to automatically adjust the opening and closing of each valve based on real-time data, achieving intelligent control and improving the system's automation level and operating efficiency.

[0015] Optionally, the heat exchange system further includes an alarm device, which is communicatively connected to the data recording and analysis module and is used to issue audible and / or visual alarm signals when the detected sulfur dioxide concentration and / or hot-side outlet temperature exceed a preset alarm threshold.

[0016] An alarm device is introduced to issue audible and / or visual alarm signals when the detected sulfur dioxide concentration and / or hot-side outlet temperature exceed a preset alarm threshold. The above settings can promptly detect and handle abnormal situations, avoid safety accidents, and ensure the safe and stable operation of the system.

[0017] Optionally, the heat exchanger is a shell-and-tube heat exchanger, and a sealing device is provided between the tube side and the shell side of the shell-and-tube heat exchanger.

[0018] A shell-and-tube heat exchanger is used, with a sealing device between the tube side and the shell side. This effectively prevents media leakage and corrosion, extending the service life of the heat exchanger. Furthermore, the shell-and-tube heat exchanger has a compact structure and high heat transfer efficiency, making it suitable for heat exchange needs under various complex operating conditions.

[0019] Optionally, the heat exchanger's tube side is made of 254SMO high-nitrogen, high-chromium, molybdenum-containing stainless steel, and the shell side is made of 316 stainless steel.

[0020] 254SMO high-nitrogen, high-chromium, molybdenum-containing stainless steel was selected as the tube-side material, and 316 stainless steel was selected as the shell-side material. High-nitrogen, high-chromium, molybdenum-containing stainless steel has good corrosion resistance, high-temperature strength, and fatigue resistance, and can operate stably for a long time in sulfur-containing environments. Using conventional 316 stainless steel for the shell side reduces equipment costs.

[0021] Optionally, the hot-side inlet pipeline and the hot-side outlet pipeline are connected to the tube side of the shell-and-tube heat exchanger; the cold-side inlet pipeline and the cold-side outlet pipeline are connected to the shell side of the shell-and-tube heat exchanger.

[0022] Optionally, the connection point between the external pipe and the hot-side outlet pipe is located downstream of the temperature sensor.

[0023] Optionally, the concentration control valve and the external pipeline valve are solenoid valves or pneumatic valves.

[0024] Solenoid valves or pneumatic valves are used as concentration control valves and external pipeline valves, which have the advantages of fast response speed and high control accuracy.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention relates to a heat exchange system for preventing sulfur dioxide dew point corrosion. By adding a concentration detector and a temperature sensor, the system can detect the concentration of sulfur dioxide in the inlet gas on the hot side and the gas temperature at the outlet gas on the hot side in real time. Based on the detection results, the system can further control the concentration control valve and external pipeline valve in the system. The system can also selectively connect external channels and nitrogen pipelines according to the concentration of sulfur dioxide in the inlet gas on the hot side and the gas temperature at the outlet gas on the hot side. This effectively prevents sulfur dioxide dew point corrosion, reduces costs, improves production efficiency, reduces safety hazards, and ensures long-term normal, stable, and safe production of the production unit. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the heat exchange system for preventing sulfur dioxide dew point corrosion according to this utility model.

[0028] Among them, 1-heat exchanger; 2-hot side inlet pipeline; 3-hot side outlet pipeline; 4-cold side inlet pipeline; 5-cold side outlet pipeline; 6-concentration detector; 7-concentration control valve; 8-temperature sensor; 9-external pipeline valve; 10-external pipeline; 11-nitrogen pipeline; 12-tail gas scrubbing tower. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0030] Example

[0031] like Figure 1 As shown, a heat exchange system for preventing sulfur dioxide dew point corrosion includes a heat exchanger 1, a hot-side inlet pipeline 2, a hot-side outlet pipeline 3, a cold-side inlet pipeline 4, a cold-side outlet pipeline 5, a concentration detector 6, a concentration control valve 7, a temperature sensor 8, an external pipeline valve 9, an external pipeline 10, a nitrogen pipeline 11, a tail gas scrubbing tower 12, a data recording and analysis module, and an alarm device.

[0032] Heat exchanger 1, as the core processing component of the heat exchange system, is used to realize the exchange of heat energy in the heat exchange system. Heat exchanger 1 has a hot-side inlet pipe 2 and a hot-side outlet pipe 3 for the gas to be processed to pass through, and a cold-side inlet pipe 4 and a cold-side outlet pipe 5 for the cooling medium to pass through. Heat exchanger 1 is a shell-and-tube heat exchanger, and a sealing device is provided between the tube side and the shell side of the shell-and-tube heat exchanger. The tube side of heat exchanger 1 is made of 254SMO high-nitrogen, high-chromium, molybdenum-containing stainless steel, and the shell side is made of 316 stainless steel. The hot-side inlet pipe 2 and the hot-side outlet pipe 3 are connected to the tube side of the shell-and-tube heat exchanger; the cold-side inlet pipe 4 and the cold-side outlet pipe 5 are connected to the shell side of the shell-and-tube heat exchanger.

[0033] Concentration detector 6 is installed on the hot-side inlet pipeline 2 to detect the concentration of sulfur dioxide in the gas to be treated entering the heat exchanger 1 and transmit the signal to the data recording and analysis module.

[0034] A concentration control valve 7 is installed on the hot-side inlet pipeline 2 and located upstream of the concentration detector 6. The concentration control valve 7 has a nitrogen pipeline 11 for connection to a nitrogen source. The concentration control valve 7 and the concentration detector 6 are connected via a data recording and analysis module to adjust the amount of nitrogen entering the hot-side inlet pipeline 2 based on the sulfur dioxide concentration measured by the concentration detector 6, thereby controlling the concentration of sulfur dioxide in the gas entering the heat exchanger. In this embodiment, the concentration control valve 7 is a solenoid valve.

[0035] Temperature sensor 8 is installed on the hot-side outlet pipeline 3 to measure the temperature of the gas in the hot-side outlet pipeline 3 and transmit the signal to the data recording and analysis module.

[0036] An external pipeline valve 9, located on the hot-side inlet pipeline 2 and upstream of the concentration control valve 7, communicates with a temperature sensor 8 via a data recording and analysis module. It controls the temperature of the gas in the hot-side outlet pipeline 3 by adjusting the connection or disconnection of the external pipeline 10 based on the temperature measured by the temperature sensor 8. When the gas temperature in the hot-side outlet pipeline is lower than the dew point of sulfur dioxide, the external pipeline valve 9 opens, connecting the external pipeline 10 to the heat exchange system to raise the temperature of the gas in the hot-side outlet pipeline 3. The gas in the external pipeline 10 does not pass through the heat exchanger for cooling; instead, it combines with the gas that has passed through the heat exchanger to rapidly increase its temperature, thus raising the gas temperature above the dew point. In this embodiment, the external pipeline valve 9 is a solenoid valve.

[0037] An external pipe 10 is provided, with one end connected to the hot-side inlet pipe 2 via an external pipe valve 9, and the other end connected to the hot-side outlet pipe 3. The connection point between the external pipe 10 and the hot-side outlet pipe 3 is located downstream of the temperature sensor 8. The external pipe 10 also includes at least one branch pipe, on which a flow control device is installed.

[0038] Nitrogen pipeline 11 is connected to a nitrogen source. Nitrogen pipeline 11 is connected to the hot-side inlet pipeline 2 via a concentration control valve 7. When the concentration detector 6 detects that the sulfur dioxide concentration in the gas in the hot-side inlet pipeline 2 is too high, the concentration control valve 7 opens, connecting nitrogen pipeline 11 to the heat exchange system and adjusting the amount of nitrogen entering the hot-side inlet pipeline 2 to reduce the concentration of sulfur dioxide in the gas.

[0039] The tail gas scrubbing tower 12 has its inlet connected to the hot-side outlet pipeline 3 and its outlet connected to the cold-side inlet pipeline 4. The tail gas scrubbing tower 12 receives the heat-exchanged gas from the hot-side outlet pipeline 3 and the gas from the external pipeline 10, and performs desulfurization treatment on the gas. The gas treated by the tail gas scrubbing tower serves as a cooling medium, entering the heat exchanger 1 through the cold-side inlet pipeline 4 and then exiting through the cold-side outlet pipeline 5. The tail gas scrubbing tower 12 is equipped with a packing layer and a spray device to improve the desulfurization effect.

[0040] Data recording and analysis module: It communicates with the concentration detector 6 and the temperature sensor 8, receives and processes signals from the concentration detector 6 and the temperature sensor 8, and sends instructions to the concentration control valve 7 and the external pipeline valve 9 according to the signal processing results to adjust their opening and closing.

[0041] Alarm device: The alarm device is connected to the data recording and analysis module. When the detected sulfur dioxide concentration and / or hot side outlet temperature exceeds the preset alarm threshold, it will emit an audible and / or visual alarm signal.

[0042] Working principle:

[0043] 1. Gas entry and concentration control:

[0044] The gas to be treated, containing sulfur dioxide, enters the tube side of heat exchanger 1 through the hot-side inlet pipeline 2. A concentration detector 6 installed on the hot-side inlet pipeline 2 monitors the concentration of sulfur dioxide in the gas in real time and transmits the signal to the data recording and analysis module. Based on the signal from the concentration detector 6, the data recording and analysis module adjusts the amount of nitrogen entering the hot-side inlet pipeline 2 via the concentration control valve 7. If the sulfur dioxide concentration is too high, the nitrogen pipeline 11 will be connected to add nitrogen and reduce the concentration of sulfur dioxide in the gas.

[0045] 2. Heat exchange:

[0046] The cooling medium (in this system, the gas treated by the tail gas scrubber 12) enters the shell side of the heat exchanger 1 through the cold-side inlet pipeline 4. Inside the heat exchanger 1, the gas to be treated in the tube side exchanges heat with the cooling medium in the shell side, thereby realizing the transfer of heat energy.

[0047] 3. Temperature control and external piping adjustment:

[0048] The gas after heat exchange is discharged through the hot-side outlet pipeline 3. A temperature sensor 8 installed on the hot-side outlet pipeline 3 measures the gas temperature in real time and transmits the signal to the data recording and analysis module. Based on the signal from the temperature sensor 8, the data recording and analysis module adjusts the connection or disconnection of the external pipeline 10 via the external pipeline valve 9. If the gas temperature in the hot-side outlet pipeline 3 is too low, the external pipeline 10 will be connected to raise the gas temperature in the hot-side outlet pipeline 3 and prevent dew point corrosion.

[0049] 4. Exhaust gas treatment and recycling:

[0050] The gas after heat exchange (still containing a certain amount of sulfur dioxide) is discharged through the hot-side outlet pipeline 3 and enters the tail gas scrubbing tower 12. Inside the tail gas scrubbing tower 12, the gas undergoes desulfurization treatment through the packing layer and spray device to reduce the sulfur dioxide content. The gas treated by the tail gas scrubbing tower 12 is used as a cooling medium and re-enters the heat exchanger 1 through the cold-side inlet pipeline 4 for recycling.

[0051] 5. Data recording, analysis, and alarms:

[0052] The data recording and analysis module continuously receives and processes signals from the concentration detector 6 and the temperature sensor 8, and sends instructions to the concentration control valve 7 and the external pipeline valve 9 based on the signal processing results. Simultaneously, the alarm device communicates with the data recording and analysis module and issues an alarm signal when the detected sulfur dioxide concentration and / or the hot-side outlet temperature exceed a preset alarm threshold.

[0053] As can be clearly seen from the above description of the embodiments, the heat exchange system of this utility model has the function of real-time detection of the concentration of sulfur dioxide in the gas and the temperature at the hot-side outlet, and automatically adjusting the system operating parameters according to the detection results, thereby effectively preventing sulfur dioxide dew point corrosion. Simultaneously, through the installation of the tail gas scrubbing tower and heat exchanger, the system can also achieve desulfurization treatment and heat recovery and utilization, improving energy efficiency and reducing environmental pollution.

[0054] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A heat exchange system for preventing sulfur dioxide dew point corrosion, characterized in that, include: The heat exchanger (1) has a hot-side inlet line (2) and a hot-side outlet line (3) for the gas to be treated to pass through, and a cold-side inlet line (4) and a cold-side outlet line (5) for the cooling medium to pass through. A concentration detector (6) is installed on the hot side inlet pipeline (2) to detect the concentration of sulfur dioxide in the gas to be treated entering the heat exchanger (1); A concentration control valve (7) is installed on the hot-side inlet pipeline (2) and located upstream of the concentration detector (6). The concentration control valve (7) is provided with a nitrogen pipeline (11) for connecting to a nitrogen source. The concentration control valve (7) is communicatively connected to the concentration detector (6) to adjust the amount of nitrogen entering the hot-side inlet pipeline (2) according to the concentration of sulfur dioxide measured by the concentration detector (6). A temperature sensor (8) is installed on the hot-side outlet pipeline (3) to measure the temperature of the gas in the hot-side outlet pipeline (3); An external pipe (10) and an external pipe valve (9) are provided. The external pipe valve (9) is located on the hot-side inlet pipe (2) and upstream of the concentration control valve (7). One end of the external pipe (10) is connected to the hot-side inlet pipe (2) via the external pipe valve (9), and the other end is connected to the hot-side outlet pipe (3). The external pipe valve (9) is communicatively connected to the temperature sensor (8) to adjust the connection or disconnection of the external pipe (10) according to the temperature measured by the temperature sensor (8) to control the temperature of the gas in the hot-side outlet pipe (3).

2. The heat exchange system according to claim 1, characterized in that, The heat exchange system also includes a tail gas scrubbing tower (12), the inlet of which is connected to the hot side outlet pipeline (3), and the outlet of which is connected to the cold side inlet pipeline (4).

3. The heat exchange system according to claim 2, characterized in that, The exhaust gas scrubbing tower (12) is equipped with a packing layer and a spraying device.

4. The heat exchange system according to claim 1, characterized in that, The external pipe (10) also includes at least one branch pipe, on which a flow control device is provided.

5. The heat exchange system according to claim 1, characterized in that, The heat exchange system also includes a data recording and analysis module. The concentration detector (6) and the temperature sensor (8) are both connected to the data recording and analysis module. The data recording and analysis module receives and processes signals from the concentration detector (6) and the temperature sensor (8), and sends instructions to the concentration control valve (7) and the external pipeline valve (9) according to the signal processing results to adjust the opening and closing of the concentration control valve (7) and the external pipeline valve (9).

6. The heat exchange system according to claim 5, characterized in that, The heat exchange system also includes an alarm device, which is communicatively connected to the data recording and analysis module and is used to issue audible and / or visual alarm signals when the detected sulfur dioxide concentration and / or hot-side outlet temperature exceed a preset alarm threshold.

7. The heat exchange system according to any one of claims 1-6, characterized in that, The heat exchanger (1) is a shell-and-tube heat exchanger, and a sealing device is provided between the tube side and the shell side of the shell-and-tube heat exchanger.

8. The heat exchange system according to claim 7, characterized in that, The hot-side inlet pipeline (2) and the hot-side outlet pipeline (3) are connected to the tube side of the shell-and-tube heat exchanger; the cold-side inlet pipeline (4) and the cold-side outlet pipeline (5) are connected to the shell side of the shell-and-tube heat exchanger.

9. The heat exchange system according to any one of claims 1-6, characterized in that, The connection point between the external pipe (10) and the hot-side outlet pipe (3) is located downstream of the temperature sensor (8).

10. The heat exchange system according to any one of claims 1-6, characterized in that, The concentration control valve (7) and the external pipeline valve (9) are solenoid valves or pneumatic valves.

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