阅读说明：本技术 一种煤制乙醇的微界面反应系统及方法 (Micro-interface reaction system and method for preparing ethanol from coal ) 是由 张志炳 周政 张锋 李磊 孟为民 王宝荣 杨高东 罗华勋 杨国强 田洪舟 曹宇 于 2020-07-16 设计创作，主要内容包括：本发明提供了一种煤制乙醇的反应系统及方法,所述反应系统包括：依次连接的甲醇制二甲醚反应单元以及二甲醚制乙醇反应单元,其中所述甲醇由煤气化制备得到；所述甲醇制二甲醚反应单元包括：二甲醚反应器；甲醇通入所述二甲醚反应器中进行气相催化脱水反应；所述二甲醚制乙醇反应单元包括：羰基化反应器,在所述羰基化反应器的外侧设置有第一微界面发生器,所述第一微界面发生器通入从所述第一精馏塔精馏分离出来的二甲醚、同时通入一氧化碳,经过所述第一微界面发生器的分散破碎后进入所述羰基化反应器进行反应。本发明提供的微界面反应系统降低了能耗,降低了反应温度,提高了原料的利用率,同时有效的提高了产能。(The invention provides a reaction system and a method for preparing ethanol from coal, wherein the reaction system comprises: the system comprises a methanol-to-dimethyl ether reaction unit and a dimethyl ether-to-ethanol reaction unit which are connected in sequence, wherein the methanol is prepared by coal gasification; the reaction unit for preparing dimethyl ether from methanol comprises: a dimethyl ether reactor; introducing methanol into the dimethyl ether reactor to perform gas phase catalytic dehydration reaction; the dimethyl ether-to-ethanol reaction unit comprises: the device comprises a carbonylation reactor, wherein a first micro-interface generator is arranged on the outer side of the carbonylation reactor, the first micro-interface generator is introduced with dimethyl ether separated by rectification of a first rectifying tower and carbon monoxide at the same time, and the dimethyl ether is dispersed and crushed by the first micro-interface generator and then enters the carbonylation reactor for reaction. The micro-interface reaction system provided by the invention reduces the energy consumption, reduces the reaction temperature, improves the utilization rate of raw materials and effectively improves the productivity.)

1. A coal-to-ethanol micro-interface reaction system is characterized by comprising: the system comprises a methanol-to-dimethyl ether reaction unit and a dimethyl ether-to-ethanol reaction unit which are connected in sequence, wherein the methanol is prepared by coal gasification;

the reaction unit for preparing dimethyl ether from methanol comprises: a dimethyl ether reactor; introducing methanol into the dimethyl ether reactor to carry out gas phase catalytic dehydration reaction, introducing a product after reaction into a first rectifying tower to carry out dimethyl ether purification and rectification, condensing a rectified gas phase, partially returning to the first rectifying tower, partially returning to the dimethyl ether reactor to carry out re-reaction, and collecting a rectified dimethyl ether side line to a dimethyl ether-to-ethanol reaction unit;

the dimethyl ether-to-ethanol reaction unit comprises: the device comprises a carbonylation reactor, wherein a first micro-interface generator is arranged on the outer side of the carbonylation reactor, the first micro-interface generator is filled with dimethyl ether separated by rectification of a first rectifying tower and carbon monoxide, the dimethyl ether and the carbon monoxide are dispersed and crushed by the first micro-interface generator and then enter the carbonylation reactor for reaction, the carbonylation reactor is connected with a second micro-interface generator so as to be filled with a carbonylation product, the second micro-interface generator is filled with hydrogen at the same time, the hydrogen is dispersed and crushed by the second micro-interface generator and then enters a hydrogenation reactor for methyl acetate hydrogenation, and a reaction product after the hydrogenation reaction is subjected to methanol and ethanol separation by a second rectifying tower to obtain ethanol.

2. The micro-interface reaction system of claim 1, wherein the methanol to dimethyl ether reaction unit comprises a heat exchanger, and the heat exchanger is used for exchanging heat between raw material methanol and a gas phase catalytic dehydration reaction product.

3. The micro-interface reaction system according to claim 1, wherein a withdrawing mechanism for laterally withdrawing dimethyl ether is arranged on the first rectifying tower, and the withdrawing mechanism is connected with the first micro-interface generator.

4. The micro-interface reaction system according to claim 1, wherein the carbonylation reactor is a fixed bed reactor, three layers of fixed tower plates are arranged in the carbonylation reactor, a carbonylation reaction catalyst is distributed on each layer of fixed tower plate, a plurality of reaction mixture inlets are arranged on the carbonylation reactor, and the reaction mixture inlets are respectively arranged on the top of the carbonylation reactor and between the adjacent fixed tower plates.

5. A micro-interfacial reaction system according to claim 1, wherein a separation column is provided between the carbonylation reactor and the second micro-interfacial generator for removing gas phase impurities from the carbonylation product.

6. A micro-interface reaction system according to claim 5, wherein a separation tank is arranged at the top of the separation tower, the gas phase separated by the separation tank is sent to the first micro-interface generator, and the liquid phase is returned to the separation tower for re-stripping separation.

7. The micro-interface reaction system according to claim 5, wherein the bottom of the separation column is provided with a methyl acetate outlet, and the methyl acetate outlet is connected with the second micro-interface generator through a pipeline.

8. The micro-interface reaction system according to claim 1, wherein a methanol outlet is arranged at the top of the second rectifying tower, the methanol outlet returns to the dimethyl ether reactor through a pipeline to be used as a methanol raw material, and a product extraction outlet is arranged at the bottom of the second rectifying tower and used for extracting ethanol product.

9. The reaction method of the coal-to-ethanol micro-interface reaction system according to any one of claims 1 to 8, comprising:

carrying out gas phase catalytic dehydration and rectification on raw material methanol to obtain dimethyl ether;

after dimethyl ether and carbon monoxide are mixed, dispersed and crushed, carbonylation reaction is carried out to obtain a carbonylation reaction product;

and mixing, dispersing and crushing the carbonylation reaction product and hydrogen, carrying out hydrogenation reaction, and rectifying to obtain the ethanol.

10. The reaction process as claimed in claim 9, wherein the pressure of the carbonylation reaction is 2.5-3.0MPa, and the temperature of the carbonylation reaction is 200-230 ℃;

preferably, the pressure of the hydrogenation reaction is 2.5-3.0MPa, and the temperature of the hydrogenation reaction is 200-210 ℃.

Technical Field

The invention relates to the field of coal-to-ethanol, in particular to a micro-interface reaction system and a micro-interface reaction method for coal-to-ethanol.

Background

The production routes of ethanol worldwide include grain fermentation routes, petrochemical routes, and carbon-chemical routes such as coal and natural gas. The grain fermentation route is widely applied internationally, and large-scale ethanol production enterprises mostly adopt grain fermentation processes. Influenced by the 'grain crisis', the new corn fuel ethanol project is stopped to be approved in China at present. The cellulose fuel ethanol project fermented by cassava and corn straws has poor economic benefit due to high production cost, excessive dependence on national subsidies, imperfect production technology and other factors. The petrochemical route uses ethylene as raw material to prepare fuel ethanol by ethylene hydration method. China depends on import of a large amount of petroleum, and the price of ethylene is often higher than that of ethanol, so that the application and popularization of the method in China are restricted.

The carbon chemical industrial route of coal, natural gas and the like is a method for preparing synthetic gas and methanol by using coal or natural gas as raw materials and then preparing ethanol by a dimethyl ether method or an acetic acid method. However, the method has a series of problems of high reaction pressure, high temperature, high energy consumption, low raw material utilization rate, low productivity and the like.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The first purpose of the present invention is to provide a micro-interface reaction system for producing ethanol from coal, which combines the micro-interface reaction system with a micro-interface generator, thereby reducing energy consumption, reducing reaction temperature, increasing reaction yield, especially increasing the utilization rate of reaction gas phase, and effectively increasing productivity, thereby increasing product quality and yield, and further saving equipment cost and equipment floor space.

The second objective of the present invention is to provide a reaction method for preparing ethanol from coal by using the above-mentioned micro-interface reaction system, wherein the reaction method sufficiently disperses and crushes the reaction raw materials, improves the mass transfer efficiency of the reaction, improves the conversion rate of the reaction raw materials, and correspondingly improves the yield of the product.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

the invention provides a micro-interface reaction system for preparing ethanol from coal, which comprises: the system comprises a methanol-to-dimethyl ether reaction unit and a dimethyl ether-to-ethanol reaction unit which are connected in sequence, wherein the methanol is prepared by coal gasification;

the reaction unit for preparing dimethyl ether from methanol comprises: a dimethyl ether reactor; introducing methanol into the dimethyl ether reactor to carry out gas phase catalytic dehydration reaction, introducing a product after reaction into a first rectifying tower to carry out dimethyl ether purification and rectification, condensing a rectified gas phase, partially returning to the first rectifying tower, partially returning to the dimethyl ether reactor to carry out re-reaction, and collecting a rectified dimethyl ether side line to a dimethyl ether-to-ethanol reaction unit;

the dimethyl ether-to-ethanol reaction unit comprises: the device comprises a carbonylation reactor, wherein a first micro-interface generator is arranged on the outer side of the carbonylation reactor, the first micro-interface generator is filled with dimethyl ether separated by rectification of a first rectifying tower and carbon monoxide, the dimethyl ether and the carbon monoxide are dispersed and crushed by the first micro-interface generator and then enter the carbonylation reactor for reaction, the carbonylation reactor is connected with a second micro-interface generator so as to be filled with a carbonylation product, the second micro-interface generator is filled with hydrogen at the same time, the hydrogen is dispersed and crushed by the second micro-interface generator and then enters a hydrogenation reactor for methyl acetate hydrogenation, and a reaction product after the hydrogenation reaction is subjected to methanol and ethanol separation by a second rectifying tower to obtain ethanol.

According to the micro-interface reaction system for preparing ethanol from coal, the micro-interface generator is correspondingly arranged in front of the carbonylation reactor and the hydrogenation reactor, so that an entering gas phase is dispersed and crushed into micro-bubbles, the mass transfer effect is improved, and the main function of introducing a liquid phase into the micro-interface generator is to match with the dispersion and crushing of gas, which is equivalent to the function of a medium.

In addition, in the micro-interface reaction system of the invention, the micro-interface generators are required to be arranged in front of the carbonylation reactor and the hydrogenation reactor, because the reactions in the two reactors are both gas-liquid two-phase reactions, the arranged micro-interface generators can just play a role of dispersing and crushing gas phase, and because the micro-interface generators are arranged, dimethyl ether does not need to be gasified firstly, and can be directly introduced into the micro-interface generators to be mixed with carbon monoxide for dispersing and crushing, thereby simplifying the operation steps.

Preferably, the number of the first micro-interface generator or the second micro-interface generator is not unique, and in order to increase the mass transfer effect, the number of the micro-interface generators can be correspondingly increased, the micro-interface generators are preferably arranged in a manner of being sequentially arranged from top to bottom, and the micro-interface generators are preferably in a parallel connection relationship.

The first micro-interface generator and the second micro-interface generator are both in a pneumatic type, and the gas phase is introduced into the micro-interface generator and then is broken into micro bubbles after being directly contacted with the liquid phase, so that the mass transfer effect is improved.

Certainly, except for the mode of arranging the micro-interface generator in the reactor, the micro-interface generator can also be correspondingly arranged in the reactor, but the optimal mode is to arrange the micro-interface generator in front of the reactor, and the micro-interface generator is required to be arranged in front of the carbonylation reactor and the hydrogenation reactor, so that the pressure in the reaction process is ensured not to be too high, the raw materials are not required to be gasified, the centralized control is facilitated, the safety of the equipment operation is also improved, if one micro-interface generator is arranged less, the controllability of the material pressure in the whole process flow is reduced, the pressure is different, and the effect of reducing the energy consumption cannot be fully achieved.

It will be appreciated by those skilled in the art that the micro-interface generator used in the present invention is described in the prior patents of the present inventor, such as the patents of application nos. CN201610641119.6, 201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN 207581700U. The detailed structure and operation principle of the micro bubble generator (i.e. micro interface generator) is described in detail in the prior patent CN201610641119.6, which describes that "the micro bubble generator comprises a body and a secondary crushing member, wherein the body is provided with a cavity, the body is provided with an inlet communicated with the cavity, the opposite first end and second end of the cavity are both open, and the cross-sectional area of the cavity decreases from the middle of the cavity to the first end and second end of the cavity; the secondary crushing member is disposed at least one of the first end and the second end of the cavity, a portion of the secondary crushing member is disposed within the cavity, and an annular passage is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also comprises an air inlet pipe and a liquid inlet pipe. "the specific working principle of the structure disclosed in the application document is as follows: liquid enters the micro-bubble generator tangentially through the liquid inlet pipe, and gas is rotated at a super high speed and cut to break gas bubbles into micro-bubbles at a micron level, so that the mass transfer area between a liquid phase and a gas phase is increased, and the micro-bubble generator in the patent belongs to a pneumatic micro-interface generator.

In addition, the first patent 201610641251.7 describes that the primary bubble breaker has a circulation liquid inlet, a circulation gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker communicates the feed inlet with the gas-liquid mixture outlet, which indicates that the bubble breakers all need to be mixed with gas and liquid, and in addition, as can be seen from the following drawings, the primary bubble breaker mainly uses the circulation liquid as power, so that the primary bubble breaker belongs to a hydraulic micro-interface generator, and the secondary bubble breaker simultaneously introduces the gas-liquid mixture into an elliptical rotating ball for rotation, thereby realizing bubble breaking in the rotating process, so that the secondary bubble breaker actually belongs to a gas-liquid linkage micro-interface generator. In fact, the micro-interface generator is a specific form of the micro-interface generator, whether it is a hydraulic micro-interface generator or a gas-liquid linkage micro-interface generator, however, the micro-interface generator adopted in the present invention is not limited to the above forms, and the specific structure of the bubble breaker described in the prior patent is only one of the forms that the micro-interface generator of the present invention can adopt. Furthermore, the prior patent 201710766435.0 states that the principle of the bubble breaker is that high-speed jet flows are used to achieve mutual collision of gases, and also states that the bubble breaker can be used in a micro-interface strengthening reactor to verify the correlation between the bubble breaker and the micro-interface generator; moreover, in the prior patent CN106187660, there is a related description on the specific structure of the bubble breaker, see paragraphs [0031] to [0041] in the specification, and the accompanying drawings, which illustrate the specific working principle of the bubble breaker S-2 in detail, the top of the bubble breaker is a liquid phase inlet, and the side of the bubble breaker is a gas phase inlet, and the liquid phase coming from the top provides the entrainment power, so as to achieve the effect of breaking into ultra-fine bubbles, and in the accompanying drawings, the bubble breaker is also seen to be of a tapered structure, and the diameter of the upper part is larger than that of the lower part, and also for better providing the entrainment power for the liquid phase.

Since the micro-interface generator was just developed in the early stage of the prior patent application, the micro-interface generator was named as a micro-bubble generator (CN201610641119.6), a bubble breaker (201710766435.0) and the like in the early stage, and is named as a micro-interface generator in the later stage along with the continuous technical improvement, and the micro-interface generator in the present invention is equivalent to the micro-bubble generator, the bubble breaker and the like in the prior art, and has different names.

In summary, the micro-interface generator of the present invention belongs to the prior art, although some bubble breakers belong to the type of pneumatic bubble breakers, some bubble breakers belong to the type of hydraulic bubble breakers, and some bubble breakers belong to the type of gas-liquid linkage bubble breakers, the difference between the types is mainly selected according to the different specific working conditions, and in addition, the connection between the micro-interface generator and the reactor and other equipment, including the connection structure and the connection position, is determined according to the structure of the micro-interface generator, which is not limited.

The micro-interface reaction system comprises a reaction unit for preparing dimethyl ether from methanol and a reaction unit for preparing ethanol from dimethyl ether.

Wherein, the reaction unit for preparing dimethyl ether from methanol mainly comprises the following equipment: a dimethyl ether reactor and a first rectifying tower.

The methanol is firstly subjected to gas phase catalytic dehydration reaction in a dimethyl ether reactor to generate dimethyl ether, the reaction temperature is 250-270 ℃, the pressure is 1.2MPa, and the catalyst is generally a molecular sieve, such as a ZSM molecular sieve, aluminum phosphate or gamma-Al₂O₃. The dimethyl ether generated by methanol dehydration is an exothermic reaction, and the temperature of the product gas at the outlet of the reactor is 320-330 ℃. The main reaction products are dimethyl ether and water, and the side reaction products are carbon oxide, methane, hydrocarbon and the like.

Preferably, the reaction unit for preparing dimethyl ether from methanol comprises a heat exchanger, and the heat exchanger is used for carrying out heat exchange on raw material methanol and a gas-phase catalytic dehydration reaction product.

Preferably, the heat exchanger is arranged between the dimethyl ether reactor and the first rectifying tower, and a preheater is further arranged between the heat exchanger and the dimethyl ether reactor. Just because the dimethyl ether prepared by dehydrating methanol belongs to exothermic reaction, a preheater and a heat exchanger are correspondingly arranged, and the heat exchanger can exchange heat between a reaction product and a raw material, thereby achieving the purpose of effectively utilizing heat.

The reaction product enters a first rectifying tower after heat exchange for purification and rectification, and then a pure dimethyl ether product can be formed for subsequent ethanol synthesis.

The first rectifying tower is mainly used for purifying dimethyl ether products, after the gas-phase methanol recovered from the top of the first rectifying tower is liquefied by the tower top condenser, one part of the gas-phase methanol flows back to the first rectifying tower, and the other part of the gas-phase methanol returns to the dimethyl ether reactor to be reused as reaction raw materials. Most of the materials coming out of the bottom of the first rectifying tower are dimethyl ether and a small amount of methanol, and the separated methanol can be directly used as a reaction raw material of the dimethyl ether reactor after being directly extracted and simply separated.

Preferably, the first rectifying tower is provided with a recovery mechanism for laterally recovering dimethyl ether, and the recovery mechanism is connected with the first micro-interface generator. The main product of the first rectifying tower is extracted through a side extraction mechanism, and the dimethyl ether product is conveyed to a first micro-interface generator after side extraction for a subsequent ethanol synthesis process.

The reaction unit for preparing ethanol from dimethyl ether mainly comprises the following equipment: the device comprises a carbonylation reactor, a separation tower, a hydrogenation reactor and a second rectifying tower.

The carbonylation reactor for carrying out the carbonylation reaction is preferably a fixed bed reactor, three layers of fixed tower plates are arranged in the carbonylation reactor, carbonylation reaction catalysts are distributed on the fixed tower plates on each layer, a plurality of reaction mixture inlets are arranged on the carbonylation reactor, and the reaction mixture inlets are respectively arranged at the top of the carbonylation reactor and between the adjacent fixed tower plates.

Dimethyl ether products from the reaction unit for preparing dimethyl ether from methanol are not required to be gasified and are directly introduced into the first micro-interface generator, carbon monoxide is also introduced into the first micro-interface generator, the carbon monoxide is crushed into micro-bubbles under the action of liquid-phase dimethyl ether and then enters the carbonylation reactor to carry out carbonylation reaction, and in order to improve the reaction effect, mixture inlets on the carbonylation reactor are respectively arranged between adjacent fixed bed layers on the side wall and at the top.

Preferably, a separation column is provided between the carbonylation reactor and the second micro-interface generator for removing gas phase impurities from the carbonylation product.

Preferably, a separation tank is arranged at the top of the separation tower, the gas phase separated by the separation tank is sent to the first micro-interface generator, and the liquid phase is returned to the separation tower for re-stripping separation.

The method comprises the steps that carbon monoxide and dimethyl ether are subjected to carbonylation reaction under the action of a catalyst to obtain a carbonylation product, the main component of the carbonylation product is methyl acetate, and then some unreacted dimethyl ether exists, after the carbonylation product is subjected to steam stripping through a separation tower, the top of the separation tower is mainly unreacted dimethyl ether, the unreacted dimethyl ether can be directly returned to a first micro-interface generator through a separation tank arranged at the top of the separation tower to serve as reaction feeding of carbonylation, and a liquid phase discharged from the bottom of the separation tank is directly returned to the separation tower to be subjected to steam stripping separation and purification again.

Preferably, the bottom of the separation tower is provided with a methyl acetate outlet, and the methyl acetate outlet is connected with the second micro-interface generator through a pipeline.

And the substances discharged from the bottom of the separation tower are mainly methyl acetate and are conveyed into the second micro-interface generator through a pump, and in order to improve the action effect of the second micro-interface generator, the methyl acetate is preheated by a preheater and then is introduced into the second micro-interface generator. And simultaneously introducing hydrogen into the second micro-interface generator, and after the hydrogen is crushed into micro bubbles under the action of the liquid-phase methyl acetate, feeding the micro bubbles into the hydrogenation reactor for hydrogenation reaction.

Preferably, the hydrogenation reactor for hydrogenation reaction is a fixed bed reactor, the catalyst in the fixed bed reactor is fixed on the bed layer, the catalyst for hydrogenation reaction is generally nickel-based catalyst, preferably the catalyst can be supported nickel-based catalyst, or nickel-based catalyst modified by alkaline earth metal oxide or rare earth metal oxide is more preferable.

Methyl acetate generates methanol and ethanol after hydrogenation reaction, and then enters a second rectifying tower for ethanol refining, the operating pressure of the top of the second rectifying tower is about 0.03MPa, steam at the top of the second rectifying tower is condensed to 61.7 ℃, and part of a condensed liquid phase (a large amount of methanol) returns to the second rectifying tower and part of the condensed liquid phase goes to a reaction unit for preparing dimethyl ether from methanol, and is used as a reaction raw material for preparing dimethyl ether.

Preferably, a methanol outlet is formed in the top of the second rectifying tower, the methanol outlet returns to the dimethyl ether reactor through a pipeline to be used as a methanol raw material, and a product extraction outlet is formed in the bottom of the second rectifying tower and used for extracting ethanol product.

And after the substances discharged from the methanol outlet are condensed by the overhead condenser, one part of the substances returns to the second rectifying tower again, and the other part of the substances is communicated with the dimethyl ether reactor through a pipeline so as to reuse the methanol as the raw material.

And a product extraction port arranged at the bottom of the second rectifying tower is used for extracting refined ethanol, the temperature is about 101 ℃, the refined ethanol extracted from the extraction port is cooled to 40 ℃ in an ethanol cooler, then the cooled refined ethanol passes through an ethanol buffer tank and is conveyed to an ethanol product tank area by a pump, and an ethanol unqualified product tank is arranged in an intermediate tank area and is used when the automobile is started or the production is abnormal. And a small amount of rectification waste liquid, mainly comprising acetic acid, is generated at the bottom of the second rectifying tower in the process of refining the ethanol, and is cooled to normal temperature and then sent to a heavy component tank for storage.

The invention also provides a micro-interface reaction method for preparing ethanol from coal, which comprises the following steps:

carrying out gas phase catalytic dehydration and rectification on raw material methanol to obtain dimethyl ether;

after dimethyl ether and carbon monoxide are mixed, dispersed and crushed, carbonylation reaction is carried out to obtain a carbonylation reaction product;

and mixing, dispersing and crushing the carbonylation reaction product and hydrogen, carrying out hydrogenation reaction, and rectifying to obtain the ethanol.

Preferably, the pressure of the carbonylation reaction is 2.5-3.0MPa, and the temperature of the carbonylation reaction is 200-230 ℃.

Preferably, the pressure of the hydrogenation reaction is 2.5-3.0MPa, and the temperature of the hydrogenation reaction is 200-210 ℃.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

fig. 1 is a schematic structural diagram of a coal-to-ethanol micro-interface reaction system according to an embodiment of the present invention.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In order to more clearly illustrate the technical solution of the present invention, the following description is made in the form of specific embodiments.