阅读说明：本技术 一种高效回收焦炉煤气中苯类的系统及方法 (System and method for efficiently recovering benzene in coke oven gas ) 是由 李俊玲 李庆生 张顺贤 李训明 高峰 陈淼 李鑫罡 郭凤明 于 2020-12-29 设计创作，主要内容包括：本发明涉及焦化产品回收技术领域,具体涉及一种高效回收焦炉煤气中苯类的系统及方法；系统包括依次相连的终冷塔,超重力洗涤塔,贫富油换热器、富油加热器和脱苯塔；脱苯塔顶部的蒸汽出口依次与粗苯冷凝冷却器、分离回流罐和粗苯槽连接；脱苯塔底部的热贫油出口依次与热贫油泵、贫富油换热器、贫油冷却泵、缓冲分离器、贫油槽相连；所述贫油槽通过冷贫油泵与超重力洗涤塔相连。本发明将超重力洗涤塔引入焦炉煤气的苯回收系统,结合系统中其他设备的设置和工艺方法中的条件设置,实现焦炉煤气中苯类的高效回收,大幅减小系统选用的设备规模和循环洗油的用量,降低系统运行能耗,降低生产成本。(The invention relates to the technical field of coking product recovery, in particular to a system and a method for efficiently recovering benzene in coke oven gas; the system comprises a final cooling tower, a supergravity washing tower, a lean-rich oil heat exchanger, a rich oil heater and a debenzolization tower which are connected in sequence; a steam outlet at the top of the debenzolization tower is sequentially connected with a crude benzene condensation cooler, a separation reflux tank and a crude benzene tank; a hot lean oil outlet at the bottom of the debenzolization tower is sequentially connected with a hot lean oil pump, a lean rich oil heat exchanger, a lean oil cooling pump, a buffer separator and a lean oil tank; the lean oil tank is connected with the supergravity washing tower through a cold lean oil pump. The invention introduces the hypergravity washing tower into the benzene recovery system of the coke oven gas, combines the settings of other equipment in the system and the conditions in the process method, realizes the high-efficiency recovery of benzene in the coke oven gas, greatly reduces the equipment scale selected by the system and the consumption of the circulating wash oil, reduces the energy consumption of the system operation, and reduces the production cost.)

1. A system for efficiently recovering benzene in coke oven gas is characterized by comprising a final cooling tower, a supergravity washing tower, a lean and rich oil heat exchanger, a rich oil heater and a debenzolization tower;

the final cooling tower, the supergravity washing tower, the lean and rich oil heat exchanger, the rich oil heater and the debenzolization tower are connected in sequence;

a steam outlet at the top of the debenzolization tower is sequentially connected with a crude benzene condensation cooler, a separation reflux tank and a crude benzene tank;

a hot lean oil outlet at the bottom of the debenzolization tower is sequentially connected with a hot lean oil pump, a lean rich oil heat exchanger, a lean oil cooling pump, a buffer separator and a lean oil tank;

the lean oil tank is connected with the supergravity washing tower through a cold lean oil pump.

2. The system for efficiently recovering benzene in coke oven gas according to claim 1, wherein a washing and absorbing device is arranged inside the supergravity washing tower and comprises a packing layer, a tar washing oil spraying device, a transmission shaft and a support frame; the packing layer is arranged in the center of the supergravity washing tower, a tar washing oil spraying device is arranged above the packing layer, and a transmission shaft and a support frame are arranged below the packing layer.

3. The system for efficiently recycling benzene in coke oven gas according to claim 2, wherein the hypergravity washing tower is further provided with a tar washing oil spraying inlet and a motor.

4. The system for efficiently recovering benzene in coke oven gas according to claim 1, wherein the separation reflux tank is further connected with a top inlet of the debenzolization tower through a reflux pump.

5. The system for efficiently recycling benzene in coke oven gas according to claim 1, wherein the separation reflux tank is connected with a non-condensable gas cooler, and the non-condensable gas cooler is connected with a vacuum pump.

6. The system for efficiently recovering benzene in coke oven gas according to claim 1, wherein a pipeline is led out between the heat lean oil pump and the lean rich oil heat exchanger and is connected with a regenerator, and the regenerator is connected with the middle part of the debenzolization tower.

7. The system for efficiently recovering benzene in coke oven gas according to claim 1, wherein a demisting and dedusting tower is arranged between the final cooling tower and the hypergravity washing tower.

8. A method for efficiently recovering benzene in coke oven gas, which is characterized in that the method is completed in the system of any one of claims 1 to 7, and comprises the following steps:

(1) introducing coke oven gas into a final cooling tower, cooling to 27 ℃, and then introducing the coke oven gas into a hypergravity washing tower from the final cooling tower through a demisting and dedusting tower to be sprayed and washed by tar washing oil;

(2) the tar washing oil containing crude benzene in the hypergravity washing tower is sent to a lean-rich oil heat exchanger through a rich oil pump, heat exchange is carried out until the temperature reaches 120 ℃, and then the tar washing oil enters a rich oil heater to be further heated to 185-240 ℃; heating, introducing into a debenzolization tower, and performing reduced pressure distillation in the debenzolization tower;

(3) benzene steam distilled in the debenzolization tower enters a crude benzene condensation cooler for condensation, condensed benzene enters a separation reflux tank, part of crude benzene in the separation reflux tank reflows to the debenzolization tower by a reflux pump, and the other part of the crude benzene enters a crude benzene tank;

part of the non-condensed steam enters a non-condensed steam cooler for further cooling, and the rest of the non-condensed steam is pumped out by a vacuum pump and sent to a coal gas negative pressure system;

(4) and the lean oil in the debenzolization tower is pumped out by a hot lean oil pump, the lean oil is cooled by a lean-rich oil heat exchanger, the cooled lean oil enters a lean oil cooler, the cold lean oil cooled by the lean oil enters a buffer separator, solid particles and partial water in the cold lean oil are separated out and then enter a cold lean oil tank, the lean oil in the cold lean oil tank is pumped out by a cold lean oil pump and is sent to a supergravity washing tower for washing, and the oil washing completes one cycle.

9. The method of claim 8, wherein a portion of the lean oil is routed to the regeneration tower after the lean heat pump for wash regeneration.

10. The method of claim 8, wherein the reduced pressure distillation is at a pressure condition of-40 to-75 kPa.

Technical Field

The invention relates to the technical field of recovery of coking products, in particular to a system and a method for efficiently recovering benzene in coke oven gas.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

In the coking industry, a large amount of coke oven gas is generated in the coke production process, and the coke oven gas contains more substances such as tar, benzene and the like, so that a coking enterprise is provided with a benzene elution system in a coking production device so as to recover high-added-value coking benzene in the coke oven gas.

The traditional benzene washing and steaming process is adopted in the coking benzene elution process at present to recover benzene, however, the mass transfer absorption efficiency of the existing coking benzene elution system is low, the benzene elution tower is generally large in diameter and high in tower body, a large number of gas and liquid redistributors are required to be arranged in the benzene washing tower to fill various fillers with large volume, and complicated tower internals are matched in the benzene elution tower. Because of the high size of the equipment, the lift and the flow of various selected circulating pumps are higher, and the corresponding rich oil quantity needing to be heated is also higher. Therefore, the whole benzene eluting system has the problems of large equipment model selection and occupied area, high equipment investment and energy consumption, low washing and absorbing efficiency, high operating cost and the like.

Disclosure of Invention

Aiming at the technical problems in the prior art, the invention introduces the hypergravity equipment into the benzene recovery system of the coke oven gas, combines the arrangement of other equipment in the system, realizes the high-efficiency recovery of benzene in the coke oven gas, and can greatly reduce the equipment scale selected by the system and the consumption of circulating wash oil, thereby greatly reducing the operation energy consumption of the system and lowering the production cost. In order to achieve the purpose, the invention aims to provide a system and a method for efficiently recovering benzene in coke oven gas.

Specifically, the technical scheme of the invention is as follows:

in a first aspect of the invention, a system for efficiently recovering benzene in coke oven gas is provided, which comprises a final cooling tower, a supergravity washing tower, a lean-rich oil heat exchanger, a rich oil heater and a debenzolization tower;

the final cooling tower, the supergravity washing tower, the lean and rich oil heat exchanger, the rich oil heater and the debenzolization tower are connected in sequence;

a steam outlet at the top of the debenzolization tower is sequentially connected with a crude benzene condensation cooler, a separation reflux tank and a crude benzene tank;

a hot lean oil outlet at the bottom of the debenzolization tower is sequentially connected with a hot lean oil pump, a lean rich oil heat exchanger, a lean oil cooling pump, a buffer separator and a lean oil tank;

the lean oil tank is connected with the supergravity washing tower through a cold lean oil pump.

In a second aspect of the present invention, a method for efficiently recovering benzene in coke oven gas is provided, which comprises the following steps:

(1) introducing coke oven gas into a final cooling tower, cooling to 27 ℃, and then introducing the coke oven gas into a hypergravity washing tower from the final cooling tower through a demisting and dedusting tower to be sprayed and washed by tar washing oil;

(2) the tar washing oil containing crude benzene in the hypergravity washing tower is sent to a lean-rich oil heat exchanger through a rich oil pump, heat exchange is carried out until the temperature reaches 120 ℃, and then the tar washing oil enters a rich oil heater to be further heated to 185-240 ℃; heating, introducing into a debenzolization tower, and carrying out reduced pressure distillation in the debenzolization tower, wherein the pressure in the tower is controlled to be-40 to-75 kPa;

(3) benzene steam distilled in the debenzolization tower enters a crude benzene condensation cooler for condensation, condensed benzene enters a separation reflux tank, part of crude benzene in the separation reflux tank reflows to the debenzolization tower by a reflux pump, and the other part of the crude benzene enters a crude benzene product tank;

part of the non-condensed steam enters a non-condensed steam cooler for further cooling, and the rest of the non-condensed steam is pumped out by a vacuum pump and sent to a coal gas negative pressure system;

(4) and the lean oil in the debenzolization tower is pumped out by a hot lean oil pump, the lean oil is cooled by a lean-rich oil heat exchanger, the cooled lean oil enters a lean oil cooler, the cold lean oil cooled by the lean oil enters a buffer separator, solid particles and partial water in the cold lean oil are separated out and then enter a cold lean oil tank, the lean oil in the cold lean oil tank is pumped out by a cold lean oil pump and is sent to a supergravity washing tower for washing, and the oil washing completes one cycle.

The specific embodiment of the invention has the following beneficial effects:

(1) a final cooling tower is arranged in front of the hypergravity washing tower, the temperature of the coal gas is reduced to about 27 ℃, the washing and absorbing effect of the tar washing oil can be improved, and the higher absorbing speed of the tar washing oil on benzene in the coal gas can be kept at the temperature;

(2) the washing and absorbing device arranged in the hypergravity washing tower can forcibly redistribute the tar washing oil, the tar washing oil is thrown out by centrifugal force, the tar washing oil is changed into finer liquid drops under the condition of greatly improving instantaneous flow velocity, the contact area is increased, the absorption effect is improved, and the absorption efficiency is improved, so that the selectable equipment of the system is greatly reduced, the consumption of the circulating tar washing oil is also greatly reduced, only about one tenth of the traditional process is adopted, the matched debenzolization device is also reduced, the investment costs of the debenzolization tower, the oil-water separation device, the heat exchange facility, the cooling facility and the like are reduced, the consumption of the motor power of each operating equipment, steam or coal gas for heating, cooling water and the like is greatly reduced, which is less than one third of the original process, the operation energy consumption of;

(3) the demisting and dedusting tower is arranged in front of the hypergravity washing tower, so that dust impurities brought into the hypergravity washing tower by coal gas can be reduced, the problem of blockage of the hypergravity washing tower in a coking process is effectively solved, and the stable operation time of the hypergravity washing tower is improved;

(4) the traditional oil-water separating device is composed of an oil-water separator, a control separator and a crude benzene reflux tank, and the corresponding oil-water separating device can adopt an integrated groove body to integrate the functions of the oil-water separator, the control separator and the crude benzene reflux tank because of the reduction of the circulating oil quantity in the embodiment of the invention,

the equipment quantity can be reduced, the equipment investment is reduced, and the crude benzene product with qualified quality can still be obtained;

(5) a circulating oil buffer separator is arranged to separate granular solids in the circulating wash oil and a small amount of water carried in the circulating wash oil, so that the operating conditions of the supergravity washing tower are further improved;

(6) reduced pressure distillation is adopted in the distillation process, so that the energy consumption is further reduced, the crude benzene tail gas is recovered, and the tail gas emission is reduced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of the system of the present invention;

FIG. 2 is a schematic diagram of a supergravity wash column according to the present invention;

in the figure: 1. the system comprises a final cooling tower, 2, a supergravity washing tower, 3, an oil-rich pump, 4, a lean and rich oil heat exchanger, 5, a rich oil heater, 6, a debenzolization tower, 7, a crude benzene condensation cooler, 8, a separation reflux tank, 9, a crude benzene tank, 10, a non-condensing cooler, 11, a vacuum pump, 12, a regenerator, 13, a hot lean oil pump, 14, a lean oil cooler, 15, a buffer separator, 16, a lean oil tank, 17, a cold lean oil pump, 18, a reflux pump, 19, a tar washing oil spraying device, 20, a packing layer, 21, a transmission shaft and a support frame, 22, a motor, 23 and a tar washing oil spraying inlet.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In one embodiment of the invention, a system for efficiently recovering benzene in coke oven gas is provided, which comprises a final cooling tower,

the system comprises a supergravity washing tower, a lean-rich oil heat exchanger, a rich oil heater and a debenzolization tower;

the final cooling tower, the supergravity washing tower, the lean and rich oil heat exchanger, the rich oil heater and the debenzolization tower are connected in sequence;

a steam outlet at the top of the debenzolization tower is sequentially connected with a crude benzene condensation cooler, a separation reflux tank and a crude benzene tank;

a hot lean oil outlet at the bottom of the debenzolization tower is sequentially connected with a hot lean oil pump, a lean rich oil heat exchanger, a lean oil cooling pump, a buffer separator and a lean oil tank;

the lean oil tank is connected with the supergravity washing tower through a cold lean oil pump.

In a specific embodiment, a washing and absorbing device is arranged inside the supergravity washing tower and comprises a packing layer, a tar washing oil spraying device, a transmission shaft and a support frame; the packing layer is arranged in the center of the supergravity washing tower, a tar washing oil spraying device is arranged above the packing layer, and a transmission shaft and a support frame are arranged below the packing layer; the transmission shaft drives the packing layer to rotate continuously, the tar washing oil is forcibly redistributed, the tar washing oil is thrown out through centrifugal force, and the tar washing oil is changed into finer liquid drops under the condition of greatly improving the instantaneous flow rate, so that the contact area is increased, the absorption effect is improved, and the absorption efficiency is improved.

Preferably, the hypergravity washing tower is also provided with a tar washing oil spraying inlet and a motor, and the tar washing oil enters the hypergravity washing tower through the tar washing oil spraying inlet; the transmission shaft motor drives the transmission shaft to rotate so as to drive the packing layer to rotate;

because the washing liquid, namely the tar washing oil is broken into small liquid drops and is forcedly distributed at an increased speed through centrifugal force, the absorption area and the absorption speed are improved, the available equipment of the system is greatly reduced, the using amount of the circulating tar washing oil is only about one tenth of that of the traditional process, the matched debenzolization device is also reduced, the investment costs of a debenzolization tower, an oil-water separation device, a heat exchange device, a cooling device, a tail gas treatment device and the like are reduced, the consumption of the motor power, heating steam or coal gas, cooling water and the like of each operating equipment is less than one third of that of the original process, the operating energy consumption of the system is greatly reduced, and.

In a specific embodiment, the separation reflux tank is also connected with an inlet at the top of the debenzolization tower through a reflux pump, and a product is refluxed to keep gas-liquid two phases at the top of the debenzolization tower balanced so as to realize continuous and stable distillation;

in a specific embodiment, the separation reflux tank is connected with a non-condensable gas cooler, and the non-condensable gas cooler is connected with a vacuum pump;

in a specific embodiment, a pipeline is led out between the hot lean oil pump and the lean rich oil heat exchanger and is connected with a regenerator, and the regenerator is connected with the middle part of the debenzolization tower; the device can reduce the consumption of the wash oil, realize the regeneration of the wash oil, namely the wash oil, evaporate the light components of the wash oil for reuse in the regeneration tower, discharge the heavy components out of the system, and improve the quality of the wash oil;

in a specific implementation mode, a demisting and dedusting tower is arranged between a cooling tower and a hypergravity washing tower, so that dust and impurities brought into the hypergravity washing tower by coal gas are reduced, the problem of blockage of the hypergravity washing tower in a coking process is effectively solved, and the stable operation time of the hypergravity washing tower is improved.

In one embodiment of the present invention, a method for efficiently recovering benzene in coke oven gas is provided, wherein the method is implemented in the above system, and comprises the following steps:

(1) introducing coke oven gas into a final cooling tower, cooling to 27 ℃, and then introducing the coke oven gas into a hypergravity washing tower from the final cooling tower through a demisting and dedusting tower to be sprayed and washed by tar washing oil;

(2) the tar washing oil containing crude benzene in the hypergravity washing tower is sent to a lean-rich oil heat exchanger through a rich oil pump, heat exchange is carried out until the temperature reaches 120 ℃, and then the tar washing oil enters a rich oil heater to be further heated to 185-240 ℃; heating, introducing into a debenzolization tower, and performing reduced pressure distillation in the debenzolization tower;

(3) benzene steam distilled in the debenzolization tower enters a crude benzene condensation cooler for condensation, condensed benzene enters a separation reflux tank, part of crude benzene in the separation reflux tank reflows to the debenzolization tower by a reflux pump, and the other part of the crude benzene enters a crude benzene tank;

part of the non-condensed steam enters a non-condensed steam cooler for further cooling, and the rest of the non-condensed steam is pumped out by a vacuum pump and sent to a coal gas negative pressure system;

(4) and the lean oil in the debenzolization tower is pumped out by a hot lean oil pump, the lean oil is cooled by a lean-rich oil heat exchanger, the cooled lean oil enters a lean oil cooler, the cold lean oil cooled by the lean oil enters a buffer separator, solid particles and partial water in the cold lean oil are separated out and then enter a cold lean oil tank, the lean oil in the cold lean oil tank is pumped out by a cold lean oil pump and is sent to a supergravity washing tower for washing, and the oil washing completes one cycle.

The temperature of the coke oven gas introduced into the final cooling tower is reduced to about 27 ℃, so that the washing and absorbing effect of the tar washing oil can be improved, and the higher absorbing speed of the tar washing oil on benzene in the gas can be maintained at the temperature.

In a specific embodiment, part of the lean oil is led to a regeneration tower after the lean oil heat pump to carry out washing oil regeneration.

In a specific embodiment, the pressure in the vacuum distillation column in the debenzolization column is controlled to be in the range of-40 to-75 kPa;

examples

As shown in fig. 1, a system for efficiently recovering benzene in coke oven gas comprises a final cooling tower 1, a supergravity washing tower 2, a lean-rich oil heat exchanger 4, a rich oil heater 5 and a debenzolization tower 6;

the final cooling tower 1, the supergravity washing tower 2, the lean and rich oil heat exchanger 4, the rich oil heater 5 and the debenzolization tower 6 are connected in sequence;

a steam outlet at the top of the debenzolization tower 6 is sequentially connected with a crude benzene condensation cooler 7, a separation reflux tank 8 and a crude benzene tank 9;

the separation reflux tank 8 is also connected with an inlet at the top of the debenzolization tower through a reflux pump 18, the separation reflux tank 8 is also connected with a non-condensable gas cooler 10, and the non-condensable gas cooler 10 is connected with a vacuum pump 11;

a hot lean oil outlet at the bottom of the debenzolization tower 6 is sequentially connected with a hot lean oil pump 13, a lean rich oil heat exchanger 4, a lean oil cooling pump 14, a buffer separator 15 and a lean oil tank 16; the lean oil tank 16 is connected to the supergravity wash column 1 via a cold lean oil pump 17.

A pipeline is led out between the hot lean oil pump 13 and the lean rich oil heat exchanger 14 and is connected with a regenerator 12, and the regenerator 12 is connected with the middle part of the debenzolization tower 6; a demisting and dedusting tower (not shown in the figure) is arranged between the final cooling tower 1 and the hypergravity washing tower 2.

As shown in fig. 2, a packing layer 20, a tar washing oil spraying device 19, a transmission shaft and a support frame 21 are arranged in the supergravity washing tower; the packing layer 20 is arranged in the center of the supergravity washing tower, the tar washing oil spraying device 19 is arranged above the packing layer 20, and the transmission shaft and the support frame 21 are arranged below the packing layer 20; the transmission shaft drives the packing layer to rotate continuously, the tar washing oil is forcibly redistributed, the tar washing oil is thrown out through centrifugal force, and the tar washing oil is changed into finer liquid drops under the condition of greatly improving the instantaneous flow rate, so that the contact area is increased, the absorption effect is improved, and the absorption efficiency is improved.

The hypergravity washing tower is also provided with a tar washing oil spraying inlet 23 and a motor 22, and the tar washing oil enters the hypergravity washing tower through the tar washing oil spraying inlet; the transmission shaft motor drives the transmission shaft to rotate so as to drive the packing layer to rotate;

because the washing liquid, namely the tar washing oil is broken into small liquid drops and is forcedly distributed at an increased speed through centrifugal force, the absorption area and the absorption speed are improved, the available equipment of the system is greatly reduced, the using amount of the circulating tar washing oil is only about one tenth of that of the traditional process, the matched debenzolization device is also reduced, the investment costs of a debenzolization tower, an oil-water separation device, a heat exchange device, a cooling device, a tail gas treatment device and the like are reduced, the consumption of the motor power, heating steam or coal gas, cooling water and the like of each operating equipment is less than one third of that of the original process, the operating energy consumption of the system is greatly reduced, and.

The method for efficiently recovering benzene in coke oven gas is completed in the system and comprises the following steps:

(1) introducing coke oven gas into a final cooling tower 1, cooling to 27 ℃, and then introducing the coke oven gas into a supergravity washing tower 2 from the final cooling tower 1 through a demisting and dedusting tower to be sprayed and washed by tar washing oil;

(2) sending tar washing oil containing crude benzene in the supergravity washing tower 2 to a lean-rich oil heat exchanger 4 through a rich oil pump 3, exchanging heat to 120 ℃, and then entering a rich oil heater 5 for further heating to 230-240 ℃; heating and then entering a debenzolization tower 6, and carrying out reduced pressure distillation in the debenzolization tower, wherein the pressure in the tower is controlled to be-60 to-70 kPa;

(3) benzene steam distilled in the debenzolization tower 6 enters a crude benzene condensation cooler 7 for condensation, condensed benzene enters a separation reflux tank 8, a part of crude benzene in the separation reflux tank reflows to the debenzolization tower 6 by a reflux pump 18, and a part of crude benzene enters a crude benzene tank 9;

part of the non-condensed steam enters a non-condensed steam cooler 10 for further cooling, and the rest of the non-condensed steam is pumped out by a vacuum pump 11 and sent to a coal gas negative pressure system;

(4) the lean oil in the debenzolization tower 6 is pumped out by a hot lean oil pump 13, is cooled by a lean-rich oil heat exchanger 4, the cooled lean oil enters a lean oil cooler 14, the cold lean oil cooled by the lean oil enters a buffer separator 15, solid particles and partial water in the cold lean oil are separated out and then enter a cold lean oil tank 16, the lean oil in the cold lean oil tank is pumped out by a cold lean oil pump 17 and is sent to a supergravity washing tower 2 for washing, and the oil washing completes a cycle; wherein, part of the lean oil is led to the regeneration tower 12 after the hot lean oil pump for washing oil and regeneration.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.