CN110143576B - Method and device for recycling waste gas in LED epitaxial wafer preparation process - Google Patents
Method and device for recycling waste gas in LED epitaxial wafer preparation process Download PDFInfo
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- CN110143576B CN110143576B CN201910423123.9A CN201910423123A CN110143576B CN 110143576 B CN110143576 B CN 110143576B CN 201910423123 A CN201910423123 A CN 201910423123A CN 110143576 B CN110143576 B CN 110143576B
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- 238000000034 method Methods 0.000 title claims abstract description 38
- 239000002912 waste gas Substances 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title claims abstract description 22
- 238000004064 recycling Methods 0.000 title description 10
- 239000007789 gas Substances 0.000 claims abstract description 195
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 102
- 239000001257 hydrogen Substances 0.000 claims abstract description 31
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 31
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 29
- 238000001914 filtration Methods 0.000 claims abstract description 19
- 238000011084 recovery Methods 0.000 claims abstract description 17
- 239000000428 dust Substances 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000010438 heat treatment Methods 0.000 claims abstract description 11
- 238000001816 cooling Methods 0.000 claims abstract description 10
- 239000002808 molecular sieve Substances 0.000 claims abstract description 9
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000005507 spraying Methods 0.000 claims abstract description 8
- 239000007788 liquid Substances 0.000 claims description 34
- 238000009833 condensation Methods 0.000 claims description 17
- 230000005494 condensation Effects 0.000 claims description 17
- 239000007921 spray Substances 0.000 claims description 17
- 239000012535 impurity Substances 0.000 claims description 14
- 238000001704 evaporation Methods 0.000 claims description 11
- 238000010992 reflux Methods 0.000 claims description 11
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 230000008020 evaporation Effects 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 8
- 238000001179 sorption measurement Methods 0.000 claims description 8
- 230000018044 dehydration Effects 0.000 claims description 4
- 238000006297 dehydration reaction Methods 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 238000003860 storage Methods 0.000 claims description 3
- 238000010521 absorption reaction Methods 0.000 claims description 2
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims 1
- 239000003546 flue gas Substances 0.000 claims 1
- XCZXGTMEAKBVPV-UHFFFAOYSA-N trimethylgallium Chemical compound C[Ga](C)C XCZXGTMEAKBVPV-UHFFFAOYSA-N 0.000 abstract description 15
- 239000002699 waste material Substances 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 9
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 9
- 239000000203 mixture Substances 0.000 description 8
- 239000007787 solid Substances 0.000 description 7
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 6
- 235000011114 ammonium hydroxide Nutrition 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 229910002601 GaN Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 229910052733 gallium Inorganic materials 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000012856 packing Methods 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000003507 refrigerant Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910000807 Ga alloy Inorganic materials 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000009615 deamination Effects 0.000 description 1
- 238000006481 deamination reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000000407 epitaxy Methods 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/0632—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron with gallium, indium or thallium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
- C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/12—Separation of ammonia from gases and vapours
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0276—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of H2/N2 mixtures, i.e. of ammonia synthesis gas
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
- C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
- C01B2203/042—Purification by adsorption on solids
Abstract
The invention relates to the technical field of waste gas recovery, in particular to a method and a device for recovering waste gas in an LED epitaxial wafer preparation process. The recovery method specifically comprises the following steps: collecting tail gas of the waste gas of the LED epitaxial wafer preparation process, and performing dust filtration on the tail gas to obtain first filtered tail gas; pressurizing and heating the first filtered tail gas, cooling and filtering to remove an MO source in the tail gas to obtain second filtered tail gas; condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removing tail gas and industrial liquid ammonia; and (3) spraying water on the ammonia-removing tail gas, and dehydrating and pressure-swing adsorbing by using a molecular sieve to obtain high-purity hydrogen. The recovery method has simple technical process, and recovers and utilizes ammonia, hydrogen and trimethyl gallium (TMGa) in the waste gas, thereby avoiding the waste of energy sources, reducing the emission of the waste gas and having good environmental protection and economy.
Description
Technical Field
The invention relates to the technical field of waste gas recovery, in particular to a method and a device for recovering waste gas in an LED epitaxial wafer preparation process.
Background
In the process of producing the LED epitaxial wafer, a Metal Organic Chemical Vapor Deposition (MOCVD) process is mostly adopted, the process temperature is 700-1100 ℃, raw materials such as trimethylgallium, ammonia gas and the like are LED into an MOCVD system through different pipelines, simple substances such as gallium, nitrogen and the like are decomposed into in a special equipment reaction chamber, thin film single crystals of gallium nitride and alloys thereof are deposited on a sapphire substrate, and the main pollution source in the production process of the LED epitaxial wafer is ammonia-containing waste gas discharged by the MOCVD system. The components are approximately as follows:
| composition of the components | Volume fraction |
| H2 | 50％ |
| NH3 | 33％ |
| N2 | 10％ |
| TMGa | 4％ |
| CH4,THC | 3％ |
The existing ammonia-containing waste gas discharged from an MOCVD system is mainly characterized in that tail gas is introduced into pure water or dilute sulfuric acid solution, ammonia gas is absorbed, ammonia gas in the absorbed ammonia water is recovered in a heating mode, and noncondensable components such as hydrogen and nitrogen are directly discharged for amplifying.
Although the ammonia in the tail gas can be effectively removed in the treatment process, the treatment process can discharge trimethyl gallium (TMGa) in the tail gas without treatment, and the direct discharge of hydrogen causes the waste of energy, and the recycled ammonia has high water content and low quality.
Disclosure of Invention
The invention provides a method and a device for recycling waste gas in an LED epitaxial wafer preparation process, and aims to solve the technical problems of energy waste and low quality of recycled ammonia water in the tail gas treatment process of the LED epitaxial wafer preparation process in the prior art.
The embodiment of the invention provides a method for recycling waste gas in an LED epitaxial wafer preparation process, which specifically comprises the following steps:
collecting tail gas of the waste gas of the LED epitaxial wafer preparation process, and filtering the tail gas by particle impurities to obtain first filtered tail gas;
pressurizing and heating the first filtered tail gas, cooling and filtering to remove an MO source in the tail gas to obtain second filtered tail gas;
condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removing tail gas and industrial liquid ammonia;
and (3) spraying water on the ammonia-removing tail gas, and dehydrating and pressure-swing adsorbing by using a molecular sieve to obtain high-purity hydrogen.
The embodiment of the invention also provides a device for recycling waste gas in the preparation process of the LED epitaxial wafer, which specifically comprises the following steps:
the tail gas absorption tank is used for collecting tail gas of the waste gas of the LED epitaxial wafer preparation process, and the dust filter is used for filtering the particle impurities of the tail gas to obtain first filtered tail gas;
the equipment for pressurizing and heating the first filtered tail gas comprises a compressor, a heater, a regenerator and a reactor which are sequentially connected, a cooler for cooling and a second filtered tail gas filter for filtering and removing an MO source in the tail gas;
the equipment for condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removed tail gas comprises a heat exchanger, a first-stage condensed gas-liquid separator, an ice maker, a second-stage condensed gas-liquid separator and an ammonia rectifying device for obtaining industrial liquid ammonia, which are connected in sequence; and
a spray tower for spraying water on the ammonia-removing tail gas and a hydrogen PSA (Pressure Swing Adsorption ) system for obtaining high-purity hydrogen;
the dust filter is connected with the compressor through a pipeline, the filter is connected with the heat exchanger through a pipeline, and the secondary condensation gas-liquid separator is connected with the heat exchanger through a pipeline and is connected with the spray tower.
According to the method for recycling the waste gas in the preparation process of the LED epitaxial wafer, provided by the embodiment of the invention, trimethyl gallium (TMGa) is converted into gallium nitride (GaN) through high-temperature and high-pressure reaction for recycling, ammonia in the waste gas is separated through a condensation method and low-temperature rectification, high-purity liquid ammonia is obtained, and high-purity hydrogen is obtained through a pressure swing adsorption hydrogen production technology.
Drawings
Fig. 1 is a flow chart of a method for recycling waste gas in an LED epitaxial wafer preparation process according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an exhaust gas recovery apparatus in an LED epitaxial wafer manufacturing process according to an embodiment of the present invention.
Detailed Description
For a clearer explanation of the technical content of the present invention, reference is made to the detailed description herein with reference to specific examples, which are, obviously, only preferred embodiments of the present technical solution, and other technical solutions that will be apparent to those skilled in the art from the disclosed technical content still fall within the scope of the present invention.
As shown in fig. 1, the method for recovering waste gas in the preparation process of the LED epitaxial wafer provided by the embodiment of the invention specifically includes the following steps:
and step S101, collecting tail gas of the LED epitaxial wafer preparation process, and filtering solid impurities of the tail gas to obtain first filtered tail gas.
In one embodiment of the invention, the step is to collect the exhaust gas of the preparation process of the LED epitaxial wafer and then filter the exhaust gas to remove the particles or dust pollutants carried in the exhaust gas so as to prevent the particles or dust pollutants from adversely affecting the subsequent treatment process and the service life of the treatment equipment.
And step S102, pressurizing and heating the first filtered tail gas, cooling and filtering to remove an MO source in the tail gas, and obtaining second filtered tail gas.
In one embodiment of the invention, the MO source is a metal or element organic compound used as a basic material in MOCVD epitaxy technology, and the MO source in the present embodiment is mainly trimethylgallium, and the first filtered tail gas is pressurized to 1.5-2.5Mpa, and then heated to 280-350 ℃ to react for 0.5-1h, so that trimethylgallium (TMGa) in the first filtered tail gas and ammonia gas react chemically to generate hydrocarbons such as gallium nitride (GaN) and methane, wherein gallium nitride is a solid substance, and the reacted mixed gas is cooled and filtered to remove gallium nitride, thereby obtaining the second filtered tail gas.
And step S103, condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removing tail gas and industrial liquid ammonia.
In one embodiment of the invention, the process recovers the ammonia part in the second filtered tail gas according to the characteristic that ammonia is easy to liquefy, the process comprises the steps of carrying out heat exchange on the second filtered tail gas and reflux low-temperature gas, condensing part of ammonia to obtain first condensed gas through gas-liquid separation, carrying out secondary condensation on the first condensed gas at the temperature of minus 20-30 ℃ to obtain crude liquid ammonia and ammonia-removed tail gas, wherein the ammonia-removed tail gas obtained in the process has lower temperature, can be used as reflux low-temperature gas to carry out heat exchange with the second filtered tail gas which is subsequently introduced, and can save energy; and removing impurity gas dissolved in the liquid ammonia by low-temperature rectification of the obtained crude liquid nitrogen to obtain industrial liquid ammonia.
And step S104, spraying water on the ammonia-removing tail gas, and dehydrating and pressure swing adsorbing by using a molecular sieve to obtain high-purity hydrogen.
In one embodiment of the invention, in order to further remove a small amount of ammonia contained in the ammonia-removed tail gas, the ammonia-removed tail gas is subjected to water spraying, then molecular sieve dehydration is performed, and finally non-hydrogen components in the mixed gas are selectively adsorbed in a pressurized state according to the adsorption capacity of the adsorbent on different gases, so that high-purity hydrogen is obtained.
As shown in fig. 2, this embodiment further provides a device for recycling waste gas generated in a process of preparing an LED epitaxial wafer, where a direction of an arrow indicates a flow direction of a material in a processing process, and the recycling device specifically includes:
in the embodiment of the invention, the tail gas absorbing tank 1 is used for collecting tail gas of the process waste gas of the LED epitaxial wafer preparation and the dust filter 2 is used for filtering the tail gas to obtain first filtered tail gas, wherein the tail gas absorbing tank 1 collects the tail gas generated by each process device through the tail gas recovery pipe, then the tail gas is introduced into the dust filter through the gas pipeline, and dust in the tail gas is filtered through the filter screen of the dust filter 2 to obtain first filtered tail gas.
In the embodiment of the invention, the device for pressurizing and heating the first filtered tail gas comprises a compressor 3, a heater 4, a regenerator 5, a reactor 6, a cooler 7 for cooling, an MO source for filtering and removing the tail gas to obtain a second filtered tail gas filter 8, the first filtered gas obtained by filtering the dust filter 2 is introduced into the tail gas compressor 3 through a gas pipeline to obtain pressurized gas, the pressurized gas is introduced into the heater 4, the heater 4 can be an electric heater or a combustion chamber, the regenerator 5 is introduced, the normal flow gas and the reacted reflux gas exchange heat, heat energy is recovered, the reactor 6 is then introduced into the reactor to perform chemical reaction under the conditions of high temperature and high pressure to obtain solid-gas mixed gas containing solid product gallium nitride, the solid-gas mixed gas is introduced into the cooler 7, and the cooled solid-gas mixed gas is introduced into the filter 8 to obtain the second filtered tail gas.
In the embodiment of the invention, the device for condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removed tail gas comprises a heat exchanger 9, a first-stage condensed gas-liquid separator 10, an ice maker 11, a second-stage condensed gas-liquid separator 12 and an ammonia rectifying device for obtaining industrial liquid ammonia, which are sequentially connected, wherein the second filtered gas obtained by filtering through a filter is introduced into the heat exchanger 9 through a gas pipeline, the heat exchanger 9 also comprises a low-temperature gas flowing reversely, part of ammonia gas is condensed after passing through the heat exchanger to obtain a first gas-liquid mixture, the first gas-liquid mixture is introduced into the first-stage condensed gas-liquid separator 10, the first condensed gas is introduced into the ice maker 11 from the top of the first-stage condensed gas-liquid separator 10 through a pipeline for secondary condensation, the ice maker 11 can be an ammonia cooler or any other cold source, obtaining a second gas-liquid mixture, introducing second condensed gas, namely ammonia removal tail gas, into a heat exchanger through a throttle valve 13 from the top of a secondary condensed gas-liquid separator 12 to serve as reflux low-temperature gas, obtaining condensed liquid from the bottoms of the primary condensed gas-liquid separator 10 and the secondary condensed gas-liquid separator 12, merging two materials through a liquid pipeline and introducing the two materials into a rectifying tower 15, arranging a throttle valve 14 on a pipeline connected with the rectifying tower after merging, rectifying the materials through the primary rectifying tower 15 to obtain crude liquid ammonia and a small amount of gas, wherein the low-temperature refrigerant liquid in the process comes from an ice maker 11, the refrigerant liquid evaporation gas returns to the ice maker 11 again, the gas obtained in the process is merged with the ammonia removal tail gas through a gas pipeline to serve as reflux low-temperature gas, continuously introducing the crude liquid ammonia into an evaporation tank 16 to evaporate, the heat source of the evaporation tank is compressed air or an electric heater, the high-purity ammonia obtained by evaporation is led into a condenser 17 from the top of an evaporation tank 16 to be condensed, and the industrial liquid ammonia is obtained and stored in a liquid ammonia storage tank 18.
In an embodiment of the present invention, a spray tower 19 for spraying the ammonia-removing tail gas with water and a hydrogen PSA system 20 for obtaining high purity hydrogen. In the embodiment of the invention, ammonia removal tail gas and gas at the top of the rectifying tower 15 are continuously introduced into the spray tower 19 after heat exchange through the heat exchanger 9, pure water is sprayed at the top of the spray tower 19, and random packing is filled in the middle of the spray tower. The residual ammonia gas is absorbed by water in a spray tower, the spray tower can be designed into multi-stage spray, the ammonia water product with 20% ammonia content is obtained at the bottom, the ammonia water product can be directly used for sales, the gas at the top is introduced into a hydrogen PSA system 20, the hydrogen PSA system 20 specifically comprises a molecular sieve dehydration system and a pressure swing adsorption hydrogen production device, the molecular sieve dehydration system is used for removing moisture in the gas, pressure swing adsorption is carried out, impurity gas is removed, and high-purity hydrogen is obtained, wherein the impurity gas is directly discharged into the air as regenerated waste gas.
Hereinafter, the effects, which are aspects of the present invention, will be described with reference to specific examples.
Examples
Exhaust gas discharged in a Metal Organic Chemical Vapor Deposition (MOCVD) process in the production process of the LED epitaxial wafer is collected into an exhaust gas collection tank 1 through an exhaust gas collection pipeline, the exhaust gas is introduced into a dust filter 2 to remove solid impurities such as particle dust in the exhaust gas, so as to obtain first filtered exhaust gas, and adverse effects of the particle dust on subsequent treatment equipment are prevented.
Introducing the first filtered tail gas into a tail gas compressor 3, pressurizing the first filtered tail gas to 2.4Mpa, heating the first filtered tail gas to a reaction temperature of 300 ℃ through a heater 4, which can be an electric heater or a combustion chamber, introducing the first filtered tail gas into a regenerator 5, exchanging heat between normal flow gas and reacted reflux gas, recovering heat energy, then introducing the first filtered tail gas into a reactor 6, carrying out chemical reaction on trimethyl gallium (TMGa) in the tail gas and ammonia gas under high temperature and high pressure conditions to generate hydrocarbons such as gallium nitride (GaN) and methane, thereby removing trimethyl gallium in the tail gas, introducing the reacted gas into a cooler 7, reducing the temperature to 30 ℃, removing solid powder gallium nitride (GaN) generated by the reaction through a filter 8, recovering the solid powder gallium nitride (GaN) as a raw material for an LED epitaxial wafer preparation process, and obtaining the second filtered tail gas.
Introducing the second filtered tail gas into a heat exchanger 9, exchanging heat with the reverse flow gas, cooling the second filtered tail gas to 0-10 ℃, condensing part of ammonia in the second filtered tail gas to obtain a first gas-liquid mixture, introducing the first gas-liquid mixture into a first-stage condensation gas-liquid separator 10, separating liquid ammonia from the bottom of the first-stage condensation separator, discharging first non-condensable gas from the top, introducing the first non-condensable gas into a low-temperature ice maker 11, cooling to-30 ℃ to obtain ammonia-removed tail gas and a second gas-liquid mixture, wherein the ice maker can be an ammonia cooler or any other cold source, introducing the second gas-liquid mixture into a second-stage condensation gas-liquid 12 separator, the ammonia is obtained by separating from the bottom of the secondary condensation separator 12, ammonia-removing tail gas is discharged from the top, impurities such as methane, nitrogen, hydrogen and the like are dissolved in the liquid ammonia separated by the primary condensation gas-liquid separator 10 and the secondary condensation gas-liquid separator 12, the two materials are combined and throttled to 1.0Mpa by a throttle valve 14, the liquid ammonia enters a rectifying tower 15, 10 theoretical plates are arranged in the rectifying tower 15, a rectifying cold source is a low-temperature water machine, a heat source is compressed air or an electric heater, or low-temperature refrigerating liquid thereof comes from the ice maker 11, refrigerating liquid evaporating gas returns to the ice maker 11 again, crude liquid ammonia is obtained and is introduced into a crude liquid ammonia evaporating tank 16 for evaporation, and high-purity ammonia at the bottom enters a condenser 17 and is stored in a liquid ammonia storage tank 18 through condensation. The ammonia-removing tail gas is intercepted to 1.0Mpa by a throttle valve 13 and is combined with the gas at the top of a rectifying tower 15 and a small amount of liquid ammonia discharged from the bottom of a crude liquid ammonia evaporation tank 16, and the gas enters a heat exchanger 9 as reflux gas.
The main components of the reflux gas discharged from the heat exchanger are as follows by volume ratio: 62% of hydrogen, 6% of ammonia, 13% of nitrogen and 19% of methane, wherein the gas is directly introduced into the bottom of a spray tower 19, pure water is sprayed on the top of the spray tower 19, random packing is filled in the middle of the spray tower 19, the spray tower 19 can be sprayed in a plurality of sections, the reflux gas removes residual ammonia in the spray tower, an ammonia water product with 20% of content is obtained at the bottom of the reflux gas and is directly used for sale, the top gas is continuously introduced into a hydrogen PSA system (20), moisture is firstly removed in a molecular sieve system, 99.99% of high-purity hydrogen is obtained through pressure swing adsorption, and other non-hydrogen impurity gases are directly discharged into the air.
The tail gas is recovered specifically through four working sections: the first is a tail gas solid impurity treatment section, the solid impurities in the tail gas are removed through tail gas collection and filtration, the second is an MO source recovery section, the reacted particle impurities in the tail gas are removed through high-temperature high-pressure reaction and cooling filtration, and the trimethyl gallium is recovered and utilized, so that the environmental pollution is reduced, and the gallium-containing resource is saved; the third is ammonia recovery section, through the tail gas through heat transfer, low temperature heat transfer and liquid ammonia rectification condensation process obtain industry liquid ammonia through three times condensation, can directly be used to industrial use or sell, this process obtains the purity and the energy cost of liquid ammonia and is far lower than the process that draws ammonia through the ammonia water backheat, fourth is hydrogen recovery section, through two processes such as spray deamination and pressure swing adsorption hydrogen manufacturing, finally obtain 99.99% high purity hydrogen, prevented clean energy extravagant on the one hand, can promote economic benefits again.
Modifications and variations of the above embodiments will be apparent to those skilled in the art in light of the above teachings. Therefore, the invention is not limited to the specific embodiments disclosed and described above, but some modifications and changes of the invention should be also included in the scope of the claims of the invention. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.
Claims (9)
1. The waste gas recovery method for the LED epitaxial wafer preparation process is characterized by comprising the following steps of:
collecting tail gas of the waste gas of the LED epitaxial wafer preparation process, and filtering the tail gas by particle impurities to obtain first filtered tail gas;
pressurizing and heating the first filtered tail gas, cooling and filtering to remove an MO source in the tail gas to obtain second filtered tail gas; the first filtered tail gas is compressed and heated for reaction, specifically:
pressurizing the first filtered tail gas to 1.5-2.5Mpa, heating the pressurized first filtered tail gas to 280-350 ℃ and reacting for 0.5-1h;
condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removing tail gas and industrial liquid ammonia;
and (3) spraying water on the ammonia-removing tail gas, and dehydrating and pressure-swing adsorbing by using a molecular sieve to obtain high-purity hydrogen.
2. The method for recovering exhaust gas according to claim 1, wherein the step of condensing and separating the second filtered off-gas to obtain ammonia-free off-gas and industrial liquid ammonia comprises:
performing heat exchange on the second filtered tail gas and the reflux low-temperature gas to condense part of ammonia gas and obtain first condensed gas;
performing secondary condensation separation on the first condensation gas to obtain crude liquid ammonia and ammonia removal tail gas;
and (3) performing low-temperature rectification on the crude liquid ammonia to remove impurity gases dissolved in the liquid ammonia, thereby obtaining industrial liquid ammonia.
3. The exhaust gas recovery method of claim 2, wherein the counter-flow cryogenic gas is a counter-flow ammonia removal tail gas.
4. The exhaust gas recovery method according to claim 2, wherein the temperature of the secondary condensation separation is from minus 20 to 30 ℃.
5. The utility model provides a LED epitaxial wafer preparation technology waste gas recovery unit which characterized in that specifically includes:
the tail gas absorption tank is used for collecting tail gas of the waste gas of the LED epitaxial wafer preparation process, and filtering the tail gas to obtain a dust filter for filtering the first tail gas;
the equipment for pressurizing and heating the first filtered tail gas comprises a compressor, a heater, a regenerator and a reactor which are sequentially connected, a cooler for cooling and a second filtered tail gas filter for filtering and removing an MO source in the tail gas; pressurizing the first filtered tail gas to 1.5-2.5Mpa, heating the pressurized first filtered tail gas to 280-350 ℃ and reacting for 0.5-1h;
the equipment for condensing, separating and rectifying the second filtered tail gas to obtain ammonia-removed tail gas comprises a heat exchanger, a first-stage condensed gas-liquid separator, an ice maker, a second-stage condensed gas-liquid separator and an ammonia rectifying device for obtaining industrial liquid ammonia, which are connected in sequence; and
a spray tower for spraying water on the ammonia-removing tail gas and a hydrogen PSA system for obtaining high-purity hydrogen;
the dust filter is connected with the compressor through a pipeline, the filter is connected with the heat exchanger through a pipeline, and the secondary condensation gas-liquid separator is connected with the heat exchanger through a pipeline and is connected with the spray tower.
6. The waste gas recovery device according to claim 5, wherein the ammonia rectification device specifically comprises a rectification column, a crude liquid ammonia evaporation tank, a condenser and a liquid ammonia storage tank which are connected in sequence.
7. The flue gas recovery device of claim 5 wherein the hydrogen PSA system specifically comprises a molecular sieve dehydration system and a pressure swing adsorption hydrogen plant.
8. The exhaust gas recovery apparatus according to claim 5, wherein a throttle valve is provided on a pipe line between the secondary condensed gas-liquid separator and the heat exchanger.
9. The exhaust gas recovery apparatus according to claim 6, wherein the rectifying column, the evaporating tank, and the secondary condensed gas-liquid separator are connected to the heat exchanger through a pipe.
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| CN105600746A (en) * | 2014-11-06 | 2016-05-25 | 湖南高安新材料有限公司 | Hydrogen production method |
| CN106233471A (en) * | 2014-04-16 | 2016-12-14 | 耶鲁大学 | The semi-polarity GaN layer of the nitrogen polarity in Sapphire Substrate and device |
| CN108658042A (en) * | 2018-05-29 | 2018-10-16 | 四川天采科技有限责任公司 | A kind of LED-MOCVD processing procedures tail gas warm journey pressure-variable adsorption full constituent recycling method entirely |
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| CN106233471A (en) * | 2014-04-16 | 2016-12-14 | 耶鲁大学 | The semi-polarity GaN layer of the nitrogen polarity in Sapphire Substrate and device |
| CN105600746A (en) * | 2014-11-06 | 2016-05-25 | 湖南高安新材料有限公司 | Hydrogen production method |
| CN108658042A (en) * | 2018-05-29 | 2018-10-16 | 四川天采科技有限责任公司 | A kind of LED-MOCVD processing procedures tail gas warm journey pressure-variable adsorption full constituent recycling method entirely |
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