Process for recovering hydrogen and silane from HJT solar cell production waste gas

Abstract

The present invention discloses a process for recovering hydrogen and silane from HJT solar cell production waste gas, which belongs to the field of waste gas treatment technology and includes the following steps: the waste gas is sequentially input into a combined adsorption tower through a vacuum pump and a blower to remove the silane or phosphine components in the waste gas; the gas after adsorption is sent to a deep cold box to liquefy the silane or phosphine that has not been completely removed and the nitrogen in the mixed gas; and is transported to a gas-liquid separator, which separates hydrogen + a small amount of nitrogen. The high nitrogen liquid after separation refluxes in a heat exchanger and performs heat exchange with the waste gas flowing in. The refluxed high nitrogen liquid is vaporized and transported to a combined adsorption tower; step five, hydrogen purification and recovery. The present invention realizes the recovery of hydrogen and silane gas from the waste gas discharged from the production of HJT solar cells by rationally designing the process of waste gas treatment and proposing a new molecular sieve configuration, and reuses them after purification.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment, and in particular to a process for recovering hydrogen and silane from waste gas produced by HJT solar cells. Background Art

[0002] In the traditional HJT solar cell production process, because the amorphous silicon thin film deposition process and the TCO deposition process use special gases such as silane (SiH4) and phosphine (PH3), and a large amount of hydrogen is introduced into the reaction chamber as a carrier gas and filling gas, the waste gas emitted during the HJT solar cell production process is highly toxic, highly reducing, flammable and explosive.

[0003] Currently, the mainstream method for treating these waste gases in the industry is to use a plasma local scrubber. This uses a plasma generator to combust hydrogen and oxygen in the air while allowing air to flow in. The heat released by the combustion raises the waste gas temperature to over 600°C. At this temperature, silane and phosphine are decomposed into hydrogen, silicon, and phosphorus. The chemical reaction is as follows:

[0004] ;

[0005] After the hydrogen in the exhaust gas is completely burned, the excess oxygen further reacts with the remaining silane, phosphine, and silicon and phosphorus metal particles to produce water and silicon and phosphorus oxides; the chemical reaction formula is as follows:

[0006] ;

[0007] The waste gas after full reaction enters the spray tower for washing. The water can absorb the particulate matter in the waste gas, turning it into silicon-containing or phosphorus-containing wastewater and discharged into the wastewater station.

[0008] The existing technology has the following problems:

[0009] 1) When using a plasma generator to burn hydrogen, special attention must be paid to controlling the air flow rate to keep the explosive limit of the mixture away from the explosive limit of hydrogen (4.0%-75.6%). If the air flow rate does not match the amount of hydrogen in the exhaust gas, an explosion hazard may occur.

[0010] 2) Silane or phosphine decomposes and burns to produce oxide microparticles, which ultimately form wastewater in the spray tower. Treating this wastewater requires concentration and evaporation, consuming large amounts of steam or electricity.

[0011] 3) Failure to recycle and utilize materials, resulting in waste.

[0012] Based on this, the present invention designs a process for recovering hydrogen and silane from HJT solar cell production waste gas to solve the above problems. Summary of the Invention

[0013] In view of the above-mentioned shortcomings of the prior art, the present invention provides a process for recovering hydrogen and silane from waste gas produced by HJT solar cell production.

[0014] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0015] The process for recovering hydrogen and silane from HJT solar cell production waste gas includes the following steps:

[0016] Step 1: During the HJT solar cell production process, the exhaust gas discharged from the machine containing silane or phosphine, hydrogen, nitrogen and other mixed gases is transported through a vacuum pump;

[0017] Step 2: After the exhaust gas is initially pressurized by the fan, it enters the combined adsorption tower to remove silane or phosphine components in the exhaust gas, and the combined adsorption tower is filled with adsorbent;

[0018] The adsorbent adopts a modified molecular sieve, the framework adopts a modified chabazite structure, the modified chabazite is modified by electromagnetic radiation, the pore is designed as a bottleneck structure, and Cu is loaded on the inner wall of the pore. + , boron atoms are doped to replace some aluminum sites to form Lewis acid sites, a polydimethylsiloxane coating is formed on the outer surface of the pores, and zirconium phosphate nanosheets are embedded in the skeleton;

[0019] Step 3: The adsorbed gas is pressurized by a compressor and sent to a cryogenic cold box. A heat exchanger is installed in the cold box, and liquid nitrogen is used as an auxiliary cooling source to liquefy the silane or phosphine that has not been completely removed by the combined adsorption tower and the nitrogen in the mixed gas;

[0020] Step 4: The liquefied silane or phosphine and nitrogen in the mixed gas are transported to a gas-liquid separator after the heat exchanger. The gas-liquid separator separates the hydrogen and a small amount of nitrogen. The separated high-nitrogen liquid flows back through the heat exchanger to exchange heat with the incoming exhaust gas. After the reflux high-nitrogen liquid is vaporized, it is transported to the combined adsorption tower and used as the first-stage regeneration gas.

[0021] Step 5: The hydrogen separated by the gas-liquid separator and a small amount of nitrogen enter the PSA circulating adsorption tower, where the hydrogen is purified to 99.999%. The regenerated gas from the PSA circulating adsorption tower flows back to the pipeline in front of the compressor for recycling.

[0022] Furthermore, the combined adsorption tower can be used in a dual-tower switch. When Tower A is in operation, Tower B uses the exhaust gas discharged from the cold box for regeneration. After regeneration, the exhaust gas is discharged into the silane combustion barrel for subsequent harmless treatment. After the regeneration is complete, Tower B is switched to use and Tower A is regenerated.

[0023] Furthermore, after the regeneration of the first stage regeneration gas is completed, nitrogen needs to be used to perform a positive blow to the combined adsorption tower, and the positive blown dust-containing gas directly enters the silane combustion barrel.

[0024] Furthermore, the PSA cycle adsorption tower is composed of a multi-stage adsorption tower.

[0025] Furthermore, in step 2, the exhaust gas is initially pressurized to 30~80Kpa by a fan and then enters the combined adsorption tower.

[0026] Furthermore, in step three, the adsorbed gas is pressurized to 8-10 barg by a compressor and sent to a cryogenic cold box.

[0027] Furthermore, in step three, the silane or phosphine that is not completely removed by the combined adsorption tower and the nitrogen in the mixed gas are liquefied at a low temperature of -175 to -185°C.

[0028] Furthermore, the preparation method of the modified molecular sieve is as follows:

[0029] (1) Dissolving silica sol, aluminum sulfate, and sodium hydroxide in deionized water to form a uniform synthetic solution, followed by a crystallization reaction, wherein the main pore diameter is larger than the molecular diameter of H2 and smaller than the molecular diameters of SiH4 and PH3. After washing, drying, and calcining, chabazite powder is obtained. The chabazite powder is exposed to electromagnetic radiation having a wavelength of 600-800 nm and a power of 12-20 watts / cm3 for 5-10 minutes to obtain modified chabazite powder.

[0030] (2) Weighing the modified chabazite powder, dispersing it in a toluene solution of trimethylmethoxysilane, and reflux reaction to graft trimethylmethoxysilane onto the surface of the modified chabazite, further shrinking the pore entrance, and then washing and drying;

[0031] (3) Prepare cuprous chloride solution and boric acid solution and mix them, immerse the modified chabazite powder with pore modification in the mixed solution, stir and exchange, then dry and calcine to make Cu + Exchanged to the inner wall of the modified chabazite pore, boron atoms replaced some aluminum sites to form Lewis acid sites;

[0032] (4) preparing a mixed solution containing zirconium nitrate and phosphoric acid, adding the modified chabazite powder to the mixed solution, stirring the solution to react, so that zirconium phosphate nanosheets are in situ generated in the modified chabazite framework, and then drying;

[0033] (5) Dissolve polydimethylsiloxane in n-hexane to prepare a PDMS solution, immerse the modified chabazite powder in the PDMS solution, and evenly coat the surface of the modified chabazite with a layer of PDMS solution, and finally solidify to obtain the modified molecular sieve.

[0034] Furthermore, step (1) obtains a modified chabazite with a main pore diameter of 0.33 nm, and step (2) shrinks the pore entrance of the modified chabazite to 0.30 nm.

[0035] Furthermore, in step (4), the mass ratio of zirconium nitrate to phosphoric acid is 1:1.

[0036] Compared with existing technologies, the present invention has the following advantages: 1. By rationally designing the waste gas treatment process and proposing a novel molecular sieve configuration, the present invention recovers hydrogen and silane gases from the waste gas emitted by HJT solar cell production, purifies them, and reuses them. Using the modified molecular sieve as an adsorbent, it highly selectively adsorbs silane and phosphine while allowing hydrogen to pass through efficiently, achieving a hydrogen purity of up to 99.5%.

[0037] 2. There is no open flame, no high temperature, no combustion, and no explosion risk during the preparation process of the present invention.

[0038] 3. The present invention can realize the recovery of silane or phosphine, as well as the recovery of hydrogen and online purification and recycling.

[0039] 4. The system of the present invention is filled with nitrogen for protection, which is beneficial to reducing risks.

[0040] 5. Compared with traditional waste gas treatment systems, the present invention can not only save a lot of materials for enterprises and reduce production costs, but also significantly reduce the silicon-containing waste generated in the production process of HTJ batteries, and has high environmental value. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0042] Figure 1 This is a process flow chart for recovering hydrogen and silane from waste gas produced by HJT solar cells of the present invention. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0044] Example 1: In some embodiments, please refer to the accompanying drawings of the specification. Figure 1 The process of recovering hydrogen and silane from HJT solar cell production waste gas uses compression + adsorption + cryogenic cooling to carry out multi-stage separation of different components in the mixed waste gas based on different principles. The specific steps include:

[0045] Step 1: During the HJT solar cell production process, the waste gas containing silane or phosphine, hydrogen, nitrogen and other mixed gases discharged from the machine (amorphous silicon thin film deposition and TCO deposition process) is transported through a vacuum pump;

[0046] Step 2: After the exhaust gas is initially pressurized to 30~80Kpa (G) by the fan, it enters the combined adsorption tower to remove silane or phosphine components in the exhaust gas. The combined adsorption tower can be used in a dual-tower switch. The combined adsorption tower is filled with adsorbent. When Tower A is running, Tower B uses the exhaust gas discharged from the cold box for regeneration. After regeneration, the exhaust gas is discharged into the silane combustion barrel for harmless subsequent treatment. After regeneration is complete, it is switched to Tower B for use, and Tower A is regenerated in the same way.

[0047] The adsorbent adopts a modified molecular sieve, which can adsorb silane and phosphine with high selectivity and allow hydrogen to pass through efficiently.

[0048] The modified molecular sieve has the following characteristics:

[0049] The framework adopts a modified Chabazite structure. By adjusting the silicon-aluminum ratio (Si / Al=5), the main pore diameter is controlled at 0.33nm, which is slightly larger than the diameter of the H2 molecule (0.289nm), but smaller than SiH4 (0.41nm) and PH3 (0.43nm), thus achieving size screening.

[0050] The pore is designed as a "bottleneck" structure, with the entrance shrinking to 0.30nm, further blocking the entry of large molecules.

[0051] Metal-organic anchoring sites: Copper (I) ions (Cu + ), selectively adsorbing PH3 (containing lone pair electrons) through π complexation.

[0052] Lewis acid sites: Boron (B) atoms are doped to replace some aluminum sites to enhance the strong adsorption of SiH4 (SiH4 combines with the electron-deficient orbitals of B).

[0053] Surface hydrophobic treatment: A small amount of polydimethylsiloxane (PDMS) coating is added to the outer surface of the molecular sieve pores to utilize its low surface energy to reduce H2 retention and increase the flow rate.

[0054] Flame-retardant design: Zirconium phosphate (ZrP) nanosheets are embedded in the skeleton, which decompose at high temperatures to release phosphates and inhibit the combustion of adsorbed gases.

[0055] Harmless treatment: The adsorption saturated molecular sieve can be soaked in sodium hydroxide solution to decompose SiH4 / PH3 to generate harmless silicate / phosphate.

[0056] Based on the above, the modified molecular sieve design can achieve efficient separation of H2 and SiH4 / PH3 through the dual mechanism of "pore size screening + chemical adsorption".

[0057] Step 3: The adsorbed gas is pressurized to 8-10 barg by a compressor and sent to a cryogenic cold box. A heat exchanger is installed in the cold box. The heat exchanger uses a low-temperature plate-fin heat exchanger and liquid nitrogen as an auxiliary cooling source. At a low temperature of -175--185°C, the small amount of silane or phosphine that was not completely removed by the combined adsorption tower and the nitrogen in the mixed gas are liquefied;

[0058] Step 4: The liquefied small amount of silane or phosphine and the nitrogen in the mixed gas are transported to the gas-liquid separator after the heat exchanger. The gas-liquid separator separates the hydrogen and a small amount of nitrogen. The separated high-nitrogen liquid flows back through the heat exchanger to exchange heat with the incoming exhaust gas. After the reflux high-nitrogen liquid is vaporized, it is transported to the combined adsorption tower and used as the first-stage regeneration gas.

[0059] Furthermore, after the first-stage regeneration gas is regenerated, it is necessary to use nitrogen to perform a positive blow to the combined adsorption tower. The positive blown dust-laden gas directly enters the silane combustion barrel. This process is used to prevent possible large particles from damaging the compressor.

[0060] Step 5. The hydrogen + a small amount of nitrogen separated by the gas-liquid separator enters the PSA circulating adsorption tower. After the hydrogen + a small amount of nitrogen are circulated and adsorbed in the PSA (Pressure Swing Adsorption) circulating adsorption tower, the hydrogen is purified to 99.999% purity. The PSA circulating adsorption tower is composed of a multi-stage (≥3-stage) adsorption tower. The adsorbent characteristic is that when the gas enters it, the nitrogen will be adsorbed by the adsorbent, and the hydrogen can pass through normally. The regenerated gas of the PSA circulating adsorption tower is returned to the compressor for recycling.

[0061] The present invention rationally designs the waste gas treatment process and proposes a new molecular sieve configuration to achieve the recovery of hydrogen and silane gases from the waste gas discharged from the production of HJT solar cells, and reuse them after purification.

[0062] The preparation process of the present invention involves no open flame, no high temperature, no combustion, and no explosion risk.

[0063] The present invention can realize the recovery of silane or phosphine, as well as the recovery of hydrogen and the online purification and recycling of hydrogen.

[0064] The system of the present invention is filled with nitrogen for protection, which is beneficial to reducing risks.

[0065] Compared with traditional waste gas treatment systems, the present invention can not only save a large amount of materials for enterprises and reduce production costs, but also significantly reduce the silicon-containing waste generated in the production process of HTJ batteries, and has high environmental value.

[0066] Example 2: The preparation method of the modified molecular sieve is as follows:

[0067] (1) 15 g of 40% silica sol, 3.42 g of aluminum sulfate, and 0.28 g of sodium hydroxide were dissolved in 60 mL of deionized water to form a uniform synthetic solution. The solution was then transferred to a stainless steel autoclave lined with polytetrafluoroethylene, sealed, and placed in an oven for crystallization at 160 °C for 5 days. The silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons were connected by shared oxygen atoms to form chabazite crystals with a specific pore structure. The silicon-aluminum ratio was 5, and the main pore diameter was about 0.33 nm (slightly larger than the diameter of H2 molecules (0.289 nm), but smaller than SiH4 (0.41 nm) and PH3 (0.43 nm). After washing, the solution was dried at 100 °C for 10 hours and finally calcined at 535 °C for 5 hours to remove the template agent to obtain chabazite powder. The chabazite powder was exposed to electromagnetic radiation with a wavelength of 600 nm and a power of 20 W / cm for 5 minutes to obtain modified chabazite powder.

[0068] (2) Weigh 30 g of modified chabazite powder and disperse it in a toluene solution of trimethylmethoxysilane at a concentration of 0.7 mol / L. Reflux the solution at 71 °C for 5 h to graft trimethylmethoxysilane onto the surface of the modified chabazite, shrinking the pore entrance to 0.30 nm. After the reaction, wash the modified chabazite powder with an organic solvent to remove the unreacted silane reagent, and then dry it at 105 °C for 1 h.

[0069] (3) Prepare 3.5 wt% cuprous chloride solution and 2 wt% boric acid solution, mix them, immerse the modified chabazite powder with pore modification in the mixed solution, stir and exchange at 55 °C for 13 hours, then dry at 105 °C for 1 hour, and finally calcine at 450 °C for 2 hours to exchange copper (I) ions to the inner wall of the modified chabazite pore channel, and boron atoms replace some aluminum sites to form Lewis acid sites.

[0070] (4) preparing a mixed solution containing zirconium nitrate and phosphoric acid in a mass ratio of 1:1, adding the modified chabazite powder to the mixed solution, stirring and reacting at 88°C for 5 hours to form zirconium phosphate nanosheets in situ in the modified chabazite framework, and then drying at 105°C for 1 hour;

[0071] (5) Dissolve polydimethylsiloxane (PDMS) in n-hexane to prepare a 12 wt% PDMS solution, immerse the modified chabazite powder in the PDMS solution, and evenly coat the surface of the modified chabazite with a layer of PDMS solution. Finally, cure the mixture at 80 °C for 2 h to obtain a modified molecular sieve.

[0072] The modified molecular sieve is used as an adsorbent to highly selectively adsorb silane and phosphine while allowing hydrogen to pass through efficiently, with a hydrogen purity of up to 99.5%.

[0073] The present invention adopts a redesigned molecular sieve structure to selectively adsorb and separate silane, has a long service life, can efficiently separate SiH4, PH3 and hydrogen, and has good use effect.

[0074] Example 3: This differs from Example 2 in that, in step (1), after preparing the chabazite powder, the chabazite powder is exposed to electromagnetic radiation having a wavelength of 800 nm and a power of 12 watts / cm for 10 minutes to obtain a modified chabazite powder. This modified molecular sieve is used as an adsorbent to highly selectively adsorb silane and phosphine while allowing hydrogen to pass through efficiently, with a hydrogen purity of up to 99.2%.

[0075] Example 4: This differs from Example 2 in that, in step (1), after preparing the chabazite powder, the chabazite powder is exposed to electromagnetic radiation having a wavelength of 700 nm and a power of 15 watts / cm for 8 minutes to obtain a modified chabazite powder. This modified molecular sieve is used as an adsorbent to highly selectively adsorb silane and phosphine while allowing hydrogen to pass through efficiently, with a hydrogen purity of up to 99.6%.

[0076] Comparative Example 1: The difference from Example 2 is that in step (1), after the chabazite powder is prepared, electromagnetic radiation is not performed. Using this modified molecular sieve as an adsorbent, the hydrogen purity can reach 94.4%.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A process for recovering hydrogen and silane from waste gas produced by HJT solar cells, characterized in that: The following steps are involved: Step 1: During the HJT solar cell production process, the exhaust gas containing silane or phosphine, hydrogen, and nitrogen mixture discharged from the machine is transported through a vacuum pump; Step 2: After the exhaust gas is initially pressurized by the blower, it enters the combined adsorption tower to remove the silane or phosphine components in the exhaust gas, and the combined adsorption tower is filled with adsorbent; The adsorbent adopts modified molecular sieve, the framework adopts modified chabazite, the modified chabazite is modified by electromagnetic radiation, the pore is designed as a bottleneck structure, and Cu is loaded on the inner wall of the pore. + , boron atoms are doped to replace some aluminum sites to form Lewis acid sites, a polydimethylsiloxane coating is formed on the outer surface of the pores, and zirconium phosphate nanosheets are embedded in the skeleton; Step 3: The adsorbed gas is pressurized by a compressor and sent to a cryogenic cold box. A heat exchanger is installed in the cold box, and liquid nitrogen is used as an auxiliary cooling source to liquefy the silane or phosphine that has not been completely removed by the combined adsorption tower and the nitrogen in the mixed gas; Step 4: The liquefied silane or phosphine and nitrogen in the mixed gas are transported to the gas-liquid separator after the heat exchanger. The gas-liquid separator separates the hydrogen and a small amount of nitrogen. The separated high-nitrogen liquid refluxes in the heat exchanger and exchanges heat with the incoming exhaust gas. The reflux high-nitrogen liquid is vaporized and transported to the combined adsorption tower to be used as the first-stage regeneration gas. Step 5: The hydrogen + a small amount of nitrogen separated by the gas-liquid separator enters the PSA circulating adsorption tower, where the hydrogen is purified. The regenerated gas from the PSA circulating adsorption tower flows back to the pipeline in front of the compressor.

2. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: The combined adsorption tower can be switched between two towers. When Tower A is running, Tower B uses the exhaust gas discharged from the cold box for regeneration. After regeneration, the exhaust gas is discharged into the silane combustion barrel for subsequent harmless treatment. After regeneration is complete, Tower B is switched to use and Tower A is regenerated.

3. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: After the regeneration of the first stage is completed, nitrogen is needed to perform a positive blow to the combined adsorption tower, and the positive blown dust-containing gas directly enters the silane combustion barrel.

4. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: The PSA cycle adsorption tower consists of a multi-stage adsorption tower.

5. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: In step 2, the exhaust gas is initially pressurized to 30~80Kpa by the fan and then enters the combined adsorption tower.

6. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: In step three, the adsorbed gas is pressurized to 8-10 barg by a compressor and sent to a cryogenic cold box.

7. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: In step 3, the silane or phosphine that has not been completely removed by the combined adsorption tower and the nitrogen in the mixed gas are liquefied at a low temperature of -175 to -185°C.

8. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 1, characterized in that: The preparation method of the modified molecular sieve is as follows: (1) Dissolving silica sol, aluminum sulfate, and sodium hydroxide in deionized water to form a uniform synthetic solution, followed by a crystallization reaction, wherein the main pore diameter is larger than the molecular diameter of H2 and smaller than the molecular diameters of SiH4 and PH3. After washing, drying, and calcining, chabazite powder is obtained. The chabazite powder is exposed to electromagnetic radiation having a wavelength of 600-800 nm and a power of 12-20 watts / cm3 for 5-10 minutes to obtain modified chabazite powder. (2) Weighing the modified chabazite powder, dispersing it in a toluene solution of trimethylmethoxysilane, and reflux reaction to graft trimethylmethoxysilane onto the surface of the modified chabazite, further shrinking the pore entrance, and then washing and drying; (3) Prepare cuprous chloride solution and boric acid solution and mix them, immerse the modified chabazite powder with pore modification in the mixed solution, stir and exchange, then dry and calcine to make Cu + Exchanged to the inner wall of the modified chabazite pore, boron atoms replaced some aluminum sites to form Lewis acid sites; (4) preparing a mixed solution containing zirconium nitrate and phosphoric acid, adding the modified chabazite powder to the mixed solution, stirring the solution to react, so that zirconium phosphate nanosheets are in situ generated in the modified chabazite framework, and then drying; (5) Dissolve polydimethylsiloxane in n-hexane to prepare a PDMS solution, immerse the modified chabazite powder in the PDMS solution, and evenly coat the surface of the modified chabazite with a layer of PDMS solution, and finally solidify to obtain the modified molecular sieve.

9. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 8, characterized in that: Step (1) obtains a modified chabazite with a main pore diameter of 0.33 nm, and step (2) shrinks the pore entrance of the modified chabazite to 0.30 nm.

10. The process for recovering hydrogen and silane from HJT solar cell production waste gas according to claim 8, characterized in that: In step (4), the mass ratio of zirconium nitrate to phosphoric acid is 1:1.

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