A method and device for recovering special gases adsorbed by molecular sieves

Abstract

The present invention discloses a method and device for recovering special gases adsorbed by molecular sieves, which mainly adopt hydrogen or helium as carrier gas, blow into the molecular sieve adsorption column at room temperature to impact the special gases in the molecular sieve, thereby directly recovering the special gases in the molecular sieve at room temperature, with low recovery cost, easy operation, environmental protection and safety, recovery rate of up to 90% or more, and considerable economic benefits. Since the recovery method of the present invention does not require heating, other impurities such as moisture adsorbed in the molecular sieve are not easy to desorb, so that the impurity content of the recovered special gas is low and the utilization value is high. In addition, the carrier gas used in the present invention will not introduce impurities, and the subsequent direct low-temperature condensation of the special gas can separate the special gas from the carrier gas, and the separated carrier can be directly recycled. It can be seen that the present invention makes up for the technical defect that the current industry cannot directly recover the special gas adsorbed in the molecular sieve, and also greatly reduces the purification cost of the special gas.

Description

Technical Field

[0001] The present invention relates to the technical field of special gas recovery, and in particular to a method and device for recovering special gas adsorbed by molecular sieve. Background Art

[0002] In the field of high-purity specialty gases, such as arsine, phosphine, germane, etc., molecular sieves such as 3A, 4A, 5A, 13X, etc. are generally used to remove impurities such as moisture in specialty gases. The use of molecular sieves for purification has the advantages of high efficiency, deep removal of moisture and other small molecular impurities, and heating and repeated use, so it is widely used in the purification of various gases.

[0003] However, molecular sieves will also adsorb a large amount of special gases while adsorbing impurities. For example, when arsine passes through an adsorption column filled with 4A molecular sieves with a volume of 100L, the 4A molecular sieve will adsorb 20 to 30kg of arsine while adsorbing water. Arsine can be decomposed at 230°C. If the molecular sieve is directly activated, arsine will be directly lost, and the molecular sieve will easily be deactivated. If the molecular sieve is directly evacuated and replaced for reactivation, the molecular sieve adsorbed with arsine will enter the tail gas absorption spray tower, which will not only consume a large amount of oxidant, but also fail to recover the arsine inside. It can be seen that activating a molecular sieve adsorption column with a volume of 100L will cause a loss of tens of thousands of yuan. Especially for expensive special gases such as germane, the market price per kg is as high as tens of thousands of yuan, and activating a molecular sieve once will result in a loss of more than 100,000 yuan. In actual industrial production, generally, a molecular sieve needs to be activated once for every 100 to 200kg of special gases processed, and the special gases adsorbed in the molecular sieve cannot be recovered, resulting in an increase in the cost of the enterprise by more than 10%.

[0004] Therefore, it is of great significance to develop a method and equipment for efficiently recovering special gases adsorbed in molecular sieves. Summary of the invention

[0005] In order to solve the shortcomings and deficiencies in the above-mentioned prior art, the first purpose of the present invention is to provide a method for recovering special gases adsorbed by molecular sieves, and the second purpose of the present invention is to provide a device for recovering special gases adsorbed by molecular sieves. The method and device of the present invention are used together to efficiently recover the special gases adsorbed in the molecular sieves, with a recovery rate of more than 90%, which significantly reduces the loss of special gas purification and reduces the purification cost of special gases.

[0006] To achieve its purpose, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for recovering special gases adsorbed by molecular sieves, which comprises the following steps:

[0008] (1) blowing non-impurity gas to the molecular sieve adsorbing the special gas to desorb the special gas on the molecular sieve to obtain a mixed gas containing non-impurity gas and special gas;

[0009] (2) condensing the special gas in the mixed gas to separate the special gas from the non-impurity gas;

[0010] (3) Recovering the special gas condensed in step (2).

[0011] Preferably, the non-impurity gas includes at least one of hydrogen and helium. Most preferably, the non-impurity gas is hydrogen. Hydrogen has a small molecular radius, fast molecular movement speed, and excellent diffusivity. It can continuously invade the gaps of the molecular sieve and continuously impact the special gas molecules adsorbed on the molecular sieve, causing them to break free from the adsorption of the molecular sieve and then desorb. In addition, hydrogen is cheap.

[0012] Preferably, the special gas includes at least one of arsine, phosphine and germane.

[0013] Preferably, the blowing mode of the non-impurity gas is continuous blowing, and the blowing direction is blowing from bottom to top. Continuous blowing can make the non-impurity gas continuously impact the special gas molecules in the molecular sieve, so that they are quickly desorbed. Blowing from bottom to top can make the non-impurity gas flow along the natural flow direction of the gas, fully invade the molecular sieve, and desorb the special gas in the molecular sieve.

[0014] Preferably, the flow rate of the non-impurity gas is 60 to 100 L / min, and the blowing time is 8 to 12 hours. Preferably, the flow rate of the non-impurity gas is 60 L / min. Because as the flow rate of the non-impurity gas increases, the recovery rate of the special gas will also increase significantly, but when the flow rate reaches more than 60 L / min, the recovery rate of the special gas does not increase significantly. Therefore, the present invention uses 60 L / min as the optimal flow rate of the non-impurity gas, and the recovery cost of this flow rate is low, and the recovered special gas has a higher purity.

[0015] Preferably, the temperature of the condensation recovery of the special gas in step (2) is below -170°C, and the condensation medium used is liquid nitrogen, liquid argon, liquid helium or other refrigerants that can provide a cooling environment below -170°C. Since the melting point of the special gas is -100 to -170°C, the gaseous special gas will be condensed and converted into a liquid or solid state at a temperature below -170°C, while the hydrogen is still in a gaseous state at this temperature, so that the special gas can be easily separated from the hydrogen. Most preferably, the step (2) condenses the special gas at the temperature of liquid nitrogen. The temperature of liquid nitrogen is -196°C, the condensation efficiency of the special gas is high, and the price of liquid nitrogen is relatively cheap.

[0016] Preferably, in step (3), when recovering the condensed special gas, the special gas is first converted into a gaseous state and then directly filled into a gas cylinder to directly recover the special gas. Compared with only recovering key elements in the special gas, such as germanium, arsenic, and phosphorus, the method of directly recovering the special gas of the present invention is more efficient and has a higher recovery rate.

[0017] The above-mentioned recovery method of the present invention adopts hydrogen or helium as a carrier gas to bring the special gas out from the built-in molecular sieve without heating. Under the continuous flushing of the carrier gas flow, the desorbed special gas is mixed in the carrier gas flow to form a mixed gas. Under the condensation conditions of the present invention, the special gas in the mixed gas is converted into a liquid or solid state, while the non-impurity gas remains in a gaseous state, so that the special gas is separated from the non-impurity gas. Finally, the discharged non-impurity gas can be returned to the initial process through a gas circulation machine and flow into the molecular sieve adsorbed with the special gas as a carrier gas, or recovered and used by equipment such as gas cylinders. After the blowing is completed, the condensed special gas is converted back into a gaseous state and directly recovered into the gas cylinder.

[0018] The method of using non-impurity gas flow to desorb special gases from molecular sieves of the present invention is different from the principle of heating molecular sieve desorption. The recovery method of the present invention does not need to be heated, and special gases can be desorbed from the molecular sieve at room temperature, while water has great polarity and will not be desorbed from the molecular sieve. However, when heating molecular sieves to achieve desorption, special gases will decompose or transform during heating, and the heating process will also bring out a large amount of water adsorbed in the molecular sieve, and the role of molecular sieves in the field of special gases is to remove water. Therefore, if the method of heating molecular sieves is used to recover the adsorbed special gases, the water desorbed by heating will be removed by molecular sieves, which will fall into an endless loop. Therefore, in the actual production process of the industry, the special gases adsorbed by molecular sieves cannot be directly recovered. The molecular sieves adsorbed with special gases can only be heated and activated to desorb the special gases therein. Special gases are mostly toxic, and finally it is necessary to spray absorbents such as KMnO4 through the tail gas purification system or heat and oxidize through an incinerator to recover the key elements (such as germanium, arsenic, and phosphorus) in the special gases. The above existing recovery methods have low economic benefits and high recovery costs. It can be seen that the recovery method of the present invention has the advantages of low cost, easy operation, environmental protection and high efficiency, can directly recover special gases, and considerable economic benefits, which makes up for the technical defects of the existing industry.

[0019] The present invention provides a device for recovering special gases adsorbed by molecular sieves, which includes a first gas delivery pipeline, a second gas delivery pipeline and a condenser; the first gas delivery pipeline is used to blow non-impurity gas into a molecular sieve adsorption column adsorbed with special gases, so as to desorb the special gases in the molecular sieve adsorption column; the second gas delivery pipeline is used to transport the mixed gas desorbed from the molecular sieve adsorption column to the condenser; the condenser is used to condense the special gas in the mixed gas to separate the special gas from the non-impurity gas. Here, the definition and preference of special gases, non-impurity gases and molecular sieves are the same as those of the above-mentioned recovery method of the present invention, and will not be repeated here.

[0020] Preferably, the first gas delivery pipeline is connected to the interface at the bottom of the molecular sieve adsorption column, one end of the second gas delivery pipeline is connected to the interface at the top of the molecular sieve adsorption column, and the other end of the second gas delivery pipeline is connected to the condenser. In this way, the hydrogen or helium flow can flow from bottom to top inside the molecular sieve adsorption column, which is the same as its natural flow direction, and a higher flow rate can be achieved at a lower blowing pressure, so that it can better penetrate into the gap of the molecular sieve to collide with the special gas, making it easier to desorb the special gas.

[0021] Preferably, the condenser is a shell-and-tube condenser, the mixed gas flows through the shell side of the tube, the tube is filled with condensing medium, and the second gas delivery pipeline is connected to the shell side air inlet of the condenser. In the present invention, the mixed gas flows through the shell side in the shell-and-tube condenser, and the condensing medium flows through the shell side.

[0022] Preferably, the device of the present invention further comprises a condensing medium delivery pipeline, a third gas delivery pipeline, a gas circulation machine and a gas cylinder; the condensing medium delivery pipeline is used to deliver the condensing medium to the tube array of the condenser; the third gas delivery pipeline and the gas cylinder are respectively connected to the shell side gas outlet of the condenser, the third gas delivery pipeline is used to discharge the non-impurity gas separated by the condenser, the third gas delivery pipeline is also connected to the gas circulation machine, and the gas circulation machine is also connected to the first gas delivery pipeline, so that the non-impurity gas separated by the condenser can be reused as a carrier gas, and re-delivered back to the first gas delivery pipeline through the gas circulation machine, and then blown into the molecular sieve adsorption column. The gas cylinder is used to recover the special gas condensed by the condenser. After the blowing is completed, the first gas delivery pipeline, the second delivery pipeline, the condensing medium delivery pipeline and the third gas delivery pipeline are closed, and the condenser is auxiliary heated, so that the condensed special gas is converted back into a gaseous state and directly recovered by the gas cylinder. Preferably, the condensing temperature of the condenser is below -170°C, and the condensing medium used is liquid nitrogen, liquid argon, liquid helium or other refrigerants that can reach the condensing temperature. Liquid nitrogen is most preferred. The technical principle is the same as the above method and will not be repeated here.

[0023] Preferably, all pipelines of the device of the present invention are provided with regulating valves for regulating flow.

[0024] Beneficial effects of the present invention: The present invention uses hydrogen or helium as a carrier gas, and blows air into the molecular sieve adsorption column at room temperature to impact the special gas in the molecular sieve, thereby directly recovering the special gas in the molecular sieve at room temperature, with low recovery cost, easy operation, environmental protection and safety, and a recovery rate of more than 90%, with considerable economic benefits. Since the recovery method of the present invention does not require heating, other impurities such as moisture adsorbed in the molecular sieve are not easy to desorb, so that the recovered special gas has a low impurity content and a high utilization value. In addition, the carrier gas used in the present invention will not introduce impurities, and the subsequent direct low-temperature condensation of the special gas can separate the special gas from the carrier gas, and the separated carrier can be directly recycled. It can be seen that the present invention makes up for the technical defect that the current industry cannot directly recover the special gas adsorbed in the molecular sieve, and also greatly reduces the purification cost of the special gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the device for recovering special gases adsorbed by molecular sieves according to the present invention.

[0026] In the figure, a first gas delivery pipeline 1, a second gas delivery pipeline 2, a third gas delivery pipeline 3, a condensing medium delivery pipeline 4, a shell and tube condenser 5, a gas circulation machine 6, a gas cylinder 7, a molecular sieve adsorption column 8, a cooling medium inlet 9, a regulating valve 10, a cooling medium outlet 11, a shell-side air inlet 12, and a shell-side air outlet 13. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments of the present invention are only used to illustrate the technical effects of the present invention, rather than to limit the protection scope of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown, this embodiment 1 provides a device for recovering special gases adsorbed by molecular sieves, which includes a first gas delivery pipeline 1, a second gas delivery pipeline 2, a third gas delivery pipeline 3, a condensing medium delivery pipeline 4, a tube-and-tube condenser 5, a gas circulation machine 6 and a gas cylinder 7. Specifically, the first gas delivery pipeline 1 is connected to the interface at the bottom of the molecular sieve adsorption column 8 adsorbed with special gases, and is used to blow non-impurity gas into the interior of the molecular sieve adsorption column 8 to desorb the special gases in the molecular sieve. One end of the second gas delivery pipeline 2 is connected to the interface at the top of the molecular sieve adsorption column 8, and the other end of the second gas delivery pipeline 2 is connected to the shell-side air inlet 12 of the tube-and-tube condenser 5, in order to transport the mixed gas desorbed from the molecular sieve adsorption column 8 to the tube-and-tube condenser 5. The mixed gas travels through the outer shell of the tube in the tube-and-tube condenser 5, and the tube is filled with condensing medium. The special gas in the mixed gas outside the tube is condensed by the condensing medium, while the non-impurity gas remains in a gaseous state, so that the special gas is separated from the non-impurity gas. The condensing medium delivery pipeline 4 is connected to the cooling medium inlet 9 at the bottom of the tube-in-tube condenser 5, and is used to deliver the condensing medium to the tubes of the tube-in-tube condenser 5. The third gas delivery pipeline 3 and the gas cylinder 7 are respectively connected to the shell side gas outlet 13 of the tube-in-tube condenser 5, and the third gas delivery pipeline 3 is also connected to the gas circulation machine 6, and the gas circulation machine 6 is also connected to the first gas delivery pipeline 1. The third gas delivery pipeline 3 is used to discharge the non-impurity gas separated by the tube-in-tube condenser 5, and the discharged non-impurity gas is re-transported back to the first gas delivery pipeline 1 through the gas circulation machine 6 to be reused as a carrier gas. The gas cylinder 7 is used to recover the special gas condensed by the tube-in-tube condenser 5. After the blowing is completed, the gas in the shell side of the tube-in-tube condenser 5 is evacuated, the first gas delivery pipeline 1, the second delivery pipeline 2, the third gas delivery pipeline 3 and the condensing medium delivery pipeline 4 are closed, and the tube-in-tube condenser 5 is auxiliary heated, so that the special gas condensed into a solid or liquid state is converted back into a gaseous state, and then directly recovered by the gas cylinder 7. In addition, a regulating valve 10 for regulating flow is provided on the pipeline of the device.

[0030] The above-mentioned special gas is arsine, phosphine or germane, the non-impurity gas is hydrogen or helium, and the condensing medium is liquid nitrogen, liquid argon or liquid helium. A cooling medium outlet 11 is provided at the top of the tube-in-tube condenser 5, and the gasified nitrogen or argon in the tube-in-tube can be discharged from the cooling medium outlet 11.

[0031] Example 2: A method for recovering germane adsorbed by molecular sieves

[0032] The molecular sieve adsorption column to be recycled contains 200 kg of 13X molecular sieve, which has been used to purify 100 kg of germane, and 10 kg of germane is absorbed in the molecular sieve.

[0033] The device of Example 2 supporting Example 1 recovers germane in the molecular sieve adsorption column as follows:

[0034] (1) The non-impurity gas used was hydrogen, and a hydrogen flow was blown into the molecular sieve adsorption column at a flow rate of 60 L / min for 8 hours;

[0035] (2) condensing the mixed gas discharged from the molecular sieve adsorption column at liquid nitrogen temperature, and discharging the remaining uncondensed hydrogen from the third gas delivery pipeline, and then returning to the first gas delivery pipeline through the gas circulation machine;

[0036] (3) After the hydrogen blowing is completed, the gas in the shell of the tube-in-tube condenser is evacuated, and the condensed solid germane is converted back into gas through auxiliary heating and then directly recovered using a gas cylinder.

[0037] According to testing and statistics, 9.5 kg of germane was recovered in this embodiment, and the recovery rate was as high as 95%.

[0038] The impurity content of the germane recovered in this embodiment is shown in Table 1. It can be seen that the impurity content of the recovered germane is low, the purity is high, and the utilization value is high.

[0039] Table 1 Impurity content of recovered germane

[0040] Gas Phase Impurities Project <![CDATA[H2]]> <![CDATA[O2]]> <![CDATA[N2]]> CH4 CO <![CDATA[CO2]]> Moisture Content (ppm) 230 0.23 0.47 ND ND ND 1.9

[0041] Example 3: A method for recovering arsine adsorbed by molecular sieves

[0042] The molecular sieve adsorption column to be recycled contains 200 kg of 4A molecular sieve, which has been used to purify 200 kg of arsine, and 30 kg of arsine is absorbed in the molecular sieve.

[0043] The device of Example 3 supporting Example 1 recovers arsine in the molecular sieve adsorption column as follows:

[0044] (1) The non-impurity gas used was hydrogen, and a hydrogen flow was blown into the molecular sieve adsorption column at a flow rate of 60 L / min for 8 hours;

[0045] (2) condensing the mixed gas discharged from the molecular sieve adsorption column at liquid nitrogen temperature, and discharging the remaining uncondensed hydrogen from the third gas delivery pipeline, and then returning to the first gas delivery pipeline through the gas circulation machine;

[0046] (3) After the hydrogen blowing is completed, the gas in the condenser shell is evacuated, and the condensed solid arsine is converted back into gas through auxiliary heating and then directly recovered using a gas cylinder.

[0047] According to testing and statistics, 28 kg of arsine was recovered in this embodiment, and the recovery rate was as high as 93.3%.

[0048] Example 4: Investigating the influence of the flow rate and blowing time of non-impurity gas on the recovery effect of specialty gas

[0049] Experimental method: Referring to the recovery method of Example 2, hydrogen was blown through a 13X molecular sieve adsorbing 10 kg of germane at flow rates of 10 L / min, 20 L / min, 40 L / min, 60 L / min, 80 L / min and 100 L / min for 8 hours. The weight of germane recovered is shown in Table 2 below.

[0050] Table 2 Germane recovery effect at different hydrogen flow rates

[0051]

[0052] As can be seen from Table 2, with the increase of hydrogen flow rate, the recovery rate of germane is higher. When the flow rate of hydrogen reaches more than 60L / min, the recovery rate of germane does not increase significantly, and the flow rate is too high, which will bring out other impurities. Therefore, the present invention uses 60L / min as the preferred flow rate of non-impurity gas, at which time the recovery rate of germane is as high as 95%, and the purity of the recovered germane is higher.

[0053] Experimental method: Referring to the recovery method of Example 2, 13X molecular sieve absorbing 10 kg of germane was blown with hydrogen at a flow rate of 60 L / min. The blowing time was 2 hours, 4 hours, 6 hours, 8 hours, 10 hours and 12 hours respectively. The weight of germane recovered is shown in Table 3 below.

[0054] Table 3 Germane recovery effect at different blowing times

[0055]

[0056] It can be seen from Table 3 that as the blowing time increases, the recovery rate of germane increases. When the blowing time reaches more than 8 hours, the recovery rate of germane does not increase significantly. Therefore, the present invention uses 8 hours as the preferred blowing time for the non-impurity gas. At this time, the recovery rate of germane is as high as 95%, and the recovered germane has a high purity.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for recovering specialty gases adsorbed by molecular sieves, characterized in that: The steps include: (1) Blowing non-impurity gas to the molecular sieve adsorbing the special gas, so as to desorb the special gas on the molecular sieve and obtain a mixed gas containing non-impurity gas and special gas; (2) condensing the special gas in the mixed gas to separate the special gas from the non-impurity gas; (3) recovering the specialty gas condensed in step (2); The non-impurity gas includes at least one of hydrogen and helium; The special gas includes at least one of arsine, phosphine and germane.

2. The method for recovering the specialty gas adsorbed by the molecular sieve according to claim 1, characterized in that: The non-impurity gas is blown in a continuous manner, and the blowing direction is from bottom to top.

3. The method for recovering the special gas adsorbed by the molecular sieve according to claim 1, characterized in that: The flow rate of the non-impurity gas is 60-100 L / min, and the blowing time is 8-12 h.

4. The method for recovering the specialty gas adsorbed by the molecular sieve according to claim 3, characterized in that: The non-impurity gas is hydrogen.

5. The method for recovering specialty gases adsorbed by molecular sieves according to claim 1, characterized in that: The temperature of the special gas condensed and recovered in step (2) is below -170°C, and the condensing medium used is liquid nitrogen, liquid argon or liquid helium.

6. The method for recovering the specialty gas adsorbed by the molecular sieve according to claim 5, characterized in that: The step (2) condenses the special gas at liquid nitrogen temperature.

7. The method for recovering specialty gases adsorbed by molecular sieves according to claim 1, characterized in that: In the step (3), when recovering the condensed special gas, the special gas is first converted into a gaseous state and then recovered into a gas cylinder.

8. The method for recovering specialty gases adsorbed by molecular sieves according to claim 1, characterized in that: The device used in the method for recovering special gases adsorbed by molecular sieves includes a first gas delivery pipeline, a second gas delivery pipeline and a condenser; the first gas delivery pipeline is used to blow non-impurity gas into the molecular sieve adsorption column adsorbing special gases, so as to desorb the special gases in the molecular sieve adsorption column; the second gas delivery pipeline is used to transport the mixed gas desorbed from the molecular sieve adsorption column to the condenser; the condenser is used to condense the special gas in the mixed gas, so as to separate the special gas from the non-impurity gas; the non-impurity gas includes at least one of hydrogen and helium; the special gas includes at least one of arsine, phosphine and germane.

9. The method for recovering specialty gases adsorbed by molecular sieves according to claim 8, characterized in that: The first gas delivery pipeline is connected to the interface at the bottom of the molecular sieve adsorption column, one end of the second gas delivery pipeline is connected to the interface at the top of the molecular sieve adsorption column, and the other end of the second gas delivery pipeline is connected to the condenser.

10. The method for recovering specialty gases adsorbed by molecular sieves according to claim 8, characterized in that: The condenser is a shell-and-tube condenser, the mixed gas flows through the outer shell of the tube, the tube is filled with a condensing medium, and the second gas delivery pipeline is connected to the shell-side air inlet of the condenser.

11. The method for recovering specialty gases adsorbed by molecular sieves according to claim 10, characterized in that: The device also includes a condensing medium delivery pipeline, a third gas delivery pipeline, a gas circulation machine and a gas cylinder; the condensing medium delivery pipeline is used to transport the condensing medium to the tubes of the condenser; the third gas delivery pipeline and the gas cylinder are respectively connected to the shell side gas outlet of the condenser, the gas cylinder is used to recover the special gas condensed by the condenser, the third gas delivery pipeline is used to discharge the non-impurity gas separated by the condenser, the third gas delivery pipeline is also connected to the gas circulation machine, and the gas circulation machine is also connected to the first gas delivery pipeline.

12. The method for recovering specialty gases adsorbed by molecular sieves according to any one of claims 8 to 11, characterized in that: All pipelines of the device are provided with regulating valves for regulating flow.

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