A device and method for detecting low pressure gas

Abstract

The present invention discloses a device and method for low-pressure gas detection. The device comprises: a gas booster, a sampling device, a vacuum device and a detection device; the gas booster, the sampling device, the vacuum device and the detection device are respectively connected to a four-way device through a gas pipeline; the gas booster is used to increase the gas pressure inside the sampling device; the detection device is used to measure the gas inside the sampling device; a pressure reducing valve is connected between the gas booster and the four-way device; a flow regulating device and a first valve are connected between the detection device and the four-way device; a second valve is connected between the vacuum device and the four-way device. The low-pressure gas detection method of the present invention can accurately measure the gas composition and content under limited volume, and is easy to operate and low in cost.

Description

Technical Field

[0001] The invention relates to a device and method for detecting gas at low pressure. Background Art

[0002] At present, the coal gas produced by blast furnace gas or converter gas in the steelmaking process of steel plants still contains some high-value usable gases such as CO and H2 after dust removal. Recycling and purifying them can improve energy utilization and provide technical support for hydrogen purification and detection. At present, the industry uses gas-liquid two-phase flow to solve the problem of low-pressure quantitative detection of gas leakage points at gas layer drainage outlets, but this method does not solve the problem of detection accuracy when the leakage amount is small.

[0003] At present, the pressure of blast furnace gas or converter gas pipelines in steel plants after dust removal is about 10-50kPa. When manually sampling and analyzing the gas composition of coal gas, it is necessary to use a sampling device to take samples at low pressure at the pipe mouth. After repeated experiments, due to the low content of target gas in the detected gas, and the fact that the detection process will inevitably be affected by the purge and injection of gas chromatographs, the errors of various pressure gauges and personnel operations, even if the collected gas pressure is 50kPa, the gas in the 500mL sampling cylinder can only be tested once. The limited sampling volume results in a small number of tests, and it is impossible to determine whether the results of the measured gas composition are accurate. In this regard, the industry currently generally uses methods to increase the sampling volume, such as using large-volume sampling bags or large-capacity sampling cylinders to increase the number of tests. When the number of samples collected is large, on the one hand, it will be limited by space, and on the other hand, the transportation and storage costs will also increase. Summary of the invention

[0004] In order to overcome the defects of low sampling efficiency and high cost of low-pressure gas detection methods in the prior art, the present invention provides a low-pressure gas detection device and method. The low-pressure gas detection method of the present invention can accurately measure the gas composition and content under limited volume, and is easy to operate and low in cost.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention provides a low-pressure gas detection device, which comprises: a gas pressurizing device, a sampling device, a vacuum device and a detection device;

[0007] The gas pressurizing device, the sampling device, the vacuum device and the detection device are respectively connected to the four-way device through gas pipelines;

[0008] The gas booster device is used to increase the gas pressure inside the sampling device; the detection device is used to measure the gas inside the sampling device;

[0009] A pressure reducing valve is connected between the gas boosting device and the four-way device;

[0010] A flow regulating device and a first valve are connected between the detection device and the four-way device;

[0011] A second valve is connected between the vacuum device and the four-way device.

[0012] In the present invention, the pressure applied by the gas pressurizing device to the sampling device is controlled by adjusting the pressure reducing valve.

[0013] Wherein, the gas pressurizing device is preferably a pressurized steel cylinder.

[0014] Preferably, the gas pipeline connecting the gas boosting device and the four-way device is a 1 / 8 inch pipeline.

[0015] In the present invention, the sampling device can be a sampling device conventionally referred to in the art, preferably a sampling cylinder, and more preferably a sampling cylinder with a pressure gauge.

[0016] The sampling cylinder is preferably a double-ended cylinder, and both ends of the double-ended cylinder are preferably connected to valves. The smaller the capacity of the sampling cylinder, the better, preferably 500mL to 1L. Preferably, the sampling cylinder is purchased from Swagelok.

[0017] In a preferred embodiment of the present invention, the sampling cylinder is a double-ended cylinder purchased from Swagelok Company, and has a capacity of 500 mL.

[0018] Preferably, the gas pipeline connecting the sampling device and the four-way device is a 1 / 8 inch pipeline.

[0019] In the present invention, the flow regulating device is adjusted to control the gas flow rate from the sampling device to the detection device; the flow regulating device and the detection device are directly controlled by the first valve, and the connection status of the pipelines related to the gas boosting device, the sampling device and the vacuum device are controlled.

[0020] Wherein, the flow regulating device is preferably a mass flow meter.

[0021] Wherein, the detection device is preferably a gas chromatograph.

[0022] Wherein, the first valve is preferably a ball valve.

[0023] Preferably, the gas pipeline connecting the detection device and the four-way device is a 1 / 8 inch pipeline.

[0024] In the present invention, the connection state of the pipelines related to the vacuum device, the gas pressurizing device, the sampling device and the detection device is directly controlled by the second valve.

[0025] Wherein, the vacuum device is preferably a vacuum pump.

[0026] Wherein, the second valve is preferably a ball valve.

[0027] Preferably, the gas pipeline connecting the vacuum device and the second valve is a polytetrafluoroethylene tube.

[0028] Preferably, the gas pipeline connecting the vacuum device and the four-way device is a 1 / 8 inch pipeline.

[0029] The present invention also provides a low-pressure gas detection method, the steps of which include:

[0030] The pressurized gas is introduced into the gas to be tested until the system pressure of the gas to be tested reaches above 100 kPa, and then the gas is introduced into the detection device for detection;

[0031] The pressurized gas is an inert gas that is not contained in the gas to be tested and will not affect the test result.

[0032] In the present invention, preferably, the pressurized gas is introduced into the gas to be measured until the system pressure of the gas to be measured is above 150 kPa or 200 kPa, and then introduced into the detection device.

[0033] In the present invention, after the system pressure of the gas to be tested is increased, it is left standing for more than 1 hour before testing; the standing time is, for example, 1 hour, 1 day, 3 days or 5 days.

[0034] In the present invention, the inert gas refers to a gas that does not react with the gas to be measured, preferably helium or argon.

[0035] In the present invention, preferably, the low-pressure gas detection method is carried out using the low-pressure gas detection device as described above; the gas pressurizing device contains the pressurized gas; the sampling device contains the gas to be tested; when the first valve and the second valve are closed, the pressure reducing valve is adjusted, and the pressurized gas is introduced through the gas pressurizing device until the pressure in the sampling device is above 100 kPa, and then the air inlet valve and the pressure reducing valve of the sampling device are closed, the first valve is opened and the flow regulating device is adjusted, and the gas in the sampling device is introduced into the detection device for detection.

[0036] Those skilled in the art should know that before increasing the pressure to the sampling device through the gas booster device, it should be ensured that the residual gas in each pipeline of the low-pressure detection gas device will not interfere with the detection result of the final detection device. Generally speaking, the residual gas removal operation is performed. In a specific embodiment, when all valves are closed, the second valve is first opened, and the gas in the pipelines related to the gas booster device, the sampling device and the detection device is discharged through the vacuum device, and then the second valve is closed. After the residual gas removal operation, the pressurized gas is introduced into the sampling device.

[0037] Those skilled in the art should know that before the detection device is used for detection, it should be ensured that the residual gas in each pipeline of the low-pressure detection gas device will not interfere with the detection result of the final detection device. Generally speaking, the residual gas is cleared as described above. Afterwards, the pipelines related to the sampling device and the detection device are purged by introducing the gas from the gas booster device; the purging time is preferably more than 5 minutes.

[0038] In a preferred embodiment of the present invention, the flow rate of the gas from the sampling device entering the detection device is controlled by adjusting the mass flow meter.

[0039] In the present invention, the gas to be measured is preferably blast furnace gas and / or converter gas, and more preferably, the gas to be measured contains CO, N2, H2 and CO2.

[0040] In the present invention, the pressure of the gas system to be measured before pressurization is preferably 10-50 kPa.

[0041] In a preferred embodiment of the present invention, the gas to be tested is blast furnace gas and / or converter gas, or the gas to be tested contains CO, N2, H2 and CO2; and the pressurized gas is helium or argon.

[0042] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0043] The positive and progressive effects of the present invention are:

[0044] In the present invention, the low-pressure gas detection device is simple, easy to operate, and low in cost; the low-pressure gas detection method can accurately measure the gas composition and content in a limited volume, and has high efficiency. The present invention solves many problems of gas detection by pressurization, can be applied to on-site sampling of blast furnace gas or converter gas pipelines in steel plants, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the low-pressure gas detection device of Example 1.

[0046] Figure 2 This is a schematic diagram of the simulated mixed gas preparation device of Effect Example 1.

[0047] Description of Reference Numerals

[0048] Gas booster 1

[0049] Sampling device 2

[0050] Vacuum device 3

[0051] Detection device 4

[0052] Four-way device 5

[0053] Pressure reducing valve 6

[0054] Flow regulating device 7

[0055] First valve 8

[0056] Second valve 9

[0057] Standard gas cylinder 10

[0058] Pressure reducing valve 11

[0059] Tee 12

[0060] Ball valve 13

[0061] Vacuum pump 14 DETAILED DESCRIPTION

[0062] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product instructions.

[0063] Example 1

[0064] like Figure 1 As shown, Example 1 is a low-pressure gas detection device, which includes: a gas booster device 1, a sampling device 2, a vacuum device 3 and a detection device 4. The gas booster device 1, the sampling device 2, the vacuum device 3 and the detection device 4 are respectively connected to the four-way device 5 through gas pipelines. The gas booster device 1 is used to increase the air pressure inside the sampling device 2; the detection device 4 is used to measure the gas inside the sampling device 2. A pressure reducing valve 6 is connected between the gas booster device 1 and the four-way device 5. A flow regulating device 7 and a first valve 8 are connected between the detection device 4 and the four-way device 5. A second valve 9 is connected between the vacuum device 3 and the four-way device 5.

[0065] The pressure applied by the gas booster 1 to the sampling device 2 is controlled by adjusting the pressure reducing valve 6. The gas booster 1 is a booster cylinder. The gas pipeline connecting the gas booster 1 and the four-way device 5 is a 1 / 8 inch pipeline.

[0066] The sampling device 2 is a sampling cylinder with a pressure gauge. The sampling cylinder is a double-ended cylinder, and valves are connected to both ends of the double-ended cylinder. The capacity of the sampling cylinder is 500mL or 1L. The sampling cylinder is purchased from Swagelok. The gas pipeline connecting the sampling device 2 and the four-way device 5 is a 1 / 8 inch pipeline.

[0067] The gas flow rate from the sampling device 2 to the detection device 4 is controlled by adjusting the flow regulating device 7; the connection state of the pipelines related to the flow regulating device 7 and the detection device 4, the gas booster device 1, the sampling device 2 and the vacuum device 3 is directly controlled by the first valve 8. The flow regulating device 7 is a mass flow meter. The detection device 4 is a gas chromatograph. The first valve 8 is a ball valve. The gas pipeline connecting the detection device 4 and the four-way device 5 is a 1 / 8 inch pipeline.

[0068] The connection state of the pipelines related to the vacuum device 3 and the gas booster device 1, the sampling device 2 and the detection device 4 is directly controlled by the second valve 9. The vacuum device 3 is a vacuum pump. The second valve 9 is a ball valve. The gas pipeline connecting the vacuum device 3 and the second valve 9 is a polytetrafluoroethylene tube. The gas pipeline connecting the vacuum device 3 and the cross-way device 5 is a 1 / 8 inch pipeline.

[0069] A low-pressure gas detection method is performed using the aforementioned low-pressure gas detection device, and the steps include:

[0070] (1) When all valves are closed, the second valve 9 is opened first, and residual gas in the pipelines related to the gas boosting device 1, the sampling device 2 and the detection device 4 is exhausted through the vacuum device 3, and then the second valve 9 is closed.

[0071] (2) When the first valve 8 and the second valve 9 are closed, adjust the pressure reducing valve 6 to increase the pressure in the sampling device 2 through the gas booster 1 until the pressure in the sampling device 2 reaches 200 kPa, and then close the valves at both ends of the sampling device 2.

[0072] (3) With all valves closed, first open the second valve 9, exhaust the residual gas in the pipelines related to the gas booster device 1, the sampling device 2 and the detection device 4 through the vacuum device 3, and then close the second valve 9; then, purge the pipelines related to the sampling device 2 and the detection device 4 by introducing the gas from the gas booster device 1; the purging time is 5 minutes.

[0073] (4) The gas to be tested in the sampling device 2 is passed into the detection device 4 for detection. By adjusting the flow regulating device 7, the flow rate of the gas from the sampling device 2 to the detection device 4 can be controlled.

[0074] The pressurized gas in the gas pressurizing device 1 is helium.

[0075] Effect Example 1

[0076] This effect embodiment uses simulated mixed coal gas as the sample to be tested, and compares the test data after helium pressurization with the test results of the simulated mixed coal gas before helium pressurization to verify whether the device and method of Example 1 will change the composition and content of the gas to be tested, as well as the test accuracy. The model of the gas chromatograph used is Agilent GC7890B, the TCD detector is selected, the column box temperature is 40°C, and the detector temperature is 300°C.

[0077] This effect embodiment includes two steps:

[0078] Step 1:

[0079] The simulated mixed coal gas is prepared by using standard gases of CO, CO2, and H2 with nitrogen as the balance gas at an equal pressure ratio (1:1:1), wherein the content of the CO standard gas is 50%, the content of the CO2 standard gas is 20%, and the content of the H2 standard gas is 10%. The simulated mixed coal gas is connected to a gas chromatograph for detection, and the result is used as the detection result of the simulated mixed coal gas before helium filling.

[0080] The simulated mixed gas is prepared as follows: Figure 2 The simulated mixed gas preparation device shown in the figure is composed of a standard gas cylinder 10, a pressure reducing valve 11, a three-way connection 12, a ball valve 13, a vacuum pump 14, and a Swagelok cylinder 2 (same as the sampling device 2 in Example 1). The preparation steps are as follows:

[0081] Close all valves, open ball valve 13 and use vacuum pump 14 to evacuate the air in the device, open standard gas cylinder 10, at this time standard gas cylinder 10 is CO standard gas cylinder, the outlet pressure of pressure reducing valve 11 is set to 0.05Mpa, collect CO until the gas pressure in Swagelok cylinder 2 reaches 0.05Mpa, and close the inlet valve of Swagelok cylinder 2. Replace the CO standard gas cylinder with CO2 standard gas cylinder, set the outlet pressure of pressure reducing valve 11 to 0.1Mpa, and fill CO2 into Swagelok cylinder 2 according to the above steps. The pressure of Swagelok cylinder 2 reaches 0.1Mpa. Replace the CO2 standard gas cylinder with H2 standard gas cylinder, set the outlet pressure of pressure reducing valve 11 to 0.15Mpa, and fill H2 into Swagelok cylinder 2 according to the above steps. The pressure of the simulated mixed coal gas in Swagelok cylinder 2 is 0.15Mpa.

[0082] The Swagelok cylinder 2 was connected to the device of Example 1, all valves were closed and connected to the vacuum pump 14 to evacuate the air in the pipeline, and the simulated mixed coal gas was passed into the gas chromatograph for detection twice, and the carrier gas of the gas chromatograph was helium, until the pressure gauge reading dropped to 0.05Mpa, and the two detection results were similar, and the average value was taken as the detection result of the gas before helium pressurization. The test results are shown in Table 1.

[0083] Step 2:

[0084] According to the method of Example 1, helium was introduced into a Swagelok cylinder and pressurized to 200 kPa, and then introduced into a gas chromatograph for detection, and the test time intervals were 1 hour, 1 day, 3 days, and 5 days after gas mixing. The test results are shown in Table 1. According to the inter-group difference analysis, p>0.05, indicating that the difference in the test data before and after helium pressurization was not significant.

[0085] Table 1 Detection data before and after helium pressurization

[0086] Working conditions <![CDATA[H2 content ratio (%)]]> <![CDATA[CO2 content ratio (%)]]> <![CDATA[Ratio of N2 content (%)]]> CO content ratio (%) Before filling with helium 3.33 16.67 73.33 6.67 1h after filling with helium 3.32 16.23 73.47 6.67 1d after filling with helium 3.39 17.91 72.49 6.57 3d after helium filling 3.36 16.84 73.39 6.65 5 days after filling with helium 3.35 16.13 73.63 6.64

Claims

1. A method for detecting gas at low pressure, characterized in that: The low-pressure gas detection method is performed using a low-pressure gas detection device; The low-pressure gas detection device comprises: a gas pressurizing device, a sampling device, a vacuum device and a detection device; The gas pressurizing device, the sampling device, the vacuum device and the detection device are respectively connected to the four-way device through gas pipelines; The gas booster device is used to increase the gas pressure inside the sampling device; the detection device is used to measure the gas inside the sampling device; A pressure reducing valve is connected between the gas boosting device and the four-way device; A flow regulating device and a first valve are connected between the detection device and the four-way device; A second valve is connected between the vacuum device and the four-way device; The pressurized gas is introduced into the gas to be tested until the system pressure of the gas to be tested reaches above 100 kPa, and then the gas is introduced into the detection device for detection; Wherein, the pressurized gas is an inert gas that is not contained in the gas to be tested and will not affect the test result; The pressure of the gas system to be tested before pressurization is 10 to 50 kPa; The gas boosting device contains the boosted gas; the sampling device contains the gas to be tested; when the first valve and the second valve are closed, the pressure reducing valve is adjusted, and the boosted gas is introduced through the gas boosting device until the pressure in the sampling device is above 100 kPa, and then the air inlet valve and the pressure reducing valve of the sampling device are closed, the first valve is opened and the flow regulating device is adjusted, and the gas from the sampling device is introduced into the detection device for detection.

2. The low-pressure gas detection method according to claim 1, characterized in that: Before increasing the pressure of the sampling device through the gas pressurizing device, performing a residual gas removal operation; And / or, before the detection is performed by the detection device, a residual gas removal operation is performed.

3. The low-pressure gas detection method according to claim 2, characterized in that: When all valves are closed, the second valve is opened first, and the gas in the pipelines related to the gas boosting device, the sampling device and the detection device is discharged through the vacuum device, and then the second valve is closed.

4. The low-pressure gas detection method according to claim 2, characterized in that: When all valves are closed, first open the second valve, exhaust the gas in the pipelines related to the gas booster device, the sampling device and the detection device through the vacuum device, and then close the second valve; then purge the pipelines related to the sampling device and the detection device by introducing the gas from the gas booster device.

5. The low-pressure gas detection method according to claim 4, characterized in that: The purging time is more than 5 minutes.

6. The low-pressure gas detection method according to claim 1, characterized in that: The gas pressurizing device is a pressurizing steel cylinder; And / or, the gas pipeline connecting the gas boosting device and the four-way device is a 1 / 8 inch pipeline.

7. The low-pressure gas detection method according to claim 1, characterized in that: The gas pipeline connecting the sampling device and the four-way device is a 1 / 8 inch pipeline; And / or, the sampling device is a sampling cylinder.

8. The low-pressure gas detection method according to claim 7, characterized in that: The sampling device is a sampling cylinder with a pressure gauge.

9. The low-pressure gas detection method according to claim 7, characterized in that: The sampling cylinder is a double-ended cylinder, both ends of which are connected with valves; And / or, the capacity of the sampling cylinder is 500mL to 1L; And / or, the sampling cylinder is purchased from Swagelok Company.

10. The low-pressure gas detection method according to claim 1, characterized in that: The flow regulating device is a mass flow meter; And / or, the detection device is a gas chromatograph; And / or, the first valve is a ball valve; And / or, the gas pipeline connecting the detection device and the four-way device is a 1 / 8 inch pipeline.

11. The low-pressure gas detection method according to claim 1, characterized in that: The vacuum device is a vacuum pump; And / or, the second valve is a ball valve; and / or, the gas pipeline connecting the vacuum device and the second valve is a polytetrafluoroethylene tube; And / or, the gas pipeline connecting the vacuum device and the four-way device is a 1 / 8 inch pipeline.

12. The low-pressure gas detection method according to claim 1, characterized in that: Passing the pressurized gas into the gas to be tested until the system pressure of the gas to be tested reaches 150 kPa or 200 kPa or above, and then passing the gas into the detection device; And / or, after the system pressure of the gas to be tested is increased, it is left to stand for more than 1 hour before testing.

13. The low-pressure gas detection method according to claim 12, characterized in that: The placement time is 1 hour, 1 day, 3 days or 5 days.

14. The low-pressure gas detection method according to claim 1, characterized in that: The gas to be tested is blast furnace gas and / or converter gas; And / or, the inert gas is helium or argon.

15. The low-pressure gas detection method according to claim 14, characterized in that: The gas to be tested contains CO, N2, H2 and CO2.

16. The low-pressure gas detection method according to claim 14, characterized in that: The gas to be tested is blast furnace gas and / or converter gas, or the gas to be tested contains CO, N2, H2 and CO2; the pressurized gas is helium or argon.

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