Disclosure of Invention
The invention aims to solve one or more of the technical problems and provides a system for preparing acetylene by partially oxidizing natural gas, which is efficient, energy-saving and environment-friendly.
The technical scheme for solving the technical problems is as follows: the system for preparing acetylene by partial oxidation of natural gas with high efficiency, energy conservation and environmental protection comprises an air preheating system, a natural gas preheating furnace, an oxygen preheating furnace, an acetylene cracking furnace, a washing tower, a carbon black separation system and a heat exchange system, wherein the air preheating system is respectively connected with the oxygen preheating furnace and the natural gas preheating furnace and preheats air entering the oxygen preheating furnace and air entering the natural gas preheating furnace; the device comprises an oxygen preheating furnace, a natural gas preheating furnace, a washing tower, a carbon black water discharge port of the acetylene cracking furnace, a carbon black separation system and a heat exchange system, wherein the oxygen preheating furnace and the natural gas preheating furnace are respectively connected with an air inlet of the acetylene cracking furnace, an air outlet of the acetylene cracking furnace is connected with the washing tower, the carbon black water discharge port of the acetylene cracking furnace and a washings discharge port of the washing tower are respectively connected with the carbon black separation system, and the carbon black separation system is connected with the heat exchange system.
The invention has the beneficial effects that: according to the invention, the air preheating systems are arranged at the air inlets of the burners of the natural gas preheating furnace and the oxygen preheating furnace, the heat source used by the air preheating systems is high-temperature condensate rich in acetylene devices, and the high-temperature condensate is provided with a pressure head, so that the air preheating systems do not need to be additionally provided with power equipment. For the condensate which needs to be cooled, the air preheating system is additionally arranged, the condensate generated by other equipment in the device is utilized to preheat the air, the abundant heat source of the whole device is fully utilized, and the purpose of energy conservation is achieved; and the air entering the natural gas preheating furnace and the oxygen preheating furnace is preheated, so that the temperature of the combustion air entering the combustor of the preheating furnace can be increased, the subsequent sufficient combustion is facilitated, and the fuel gas can be saved.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, carbon black piece-rate system includes closed carbon black separation tank and burns the system, the charcoal black water discharge port of acetylene cracking stove reaches the washings discharge port of scrubbing tower respectively with closed carbon black separation tank connects, closed carbon black separation tank through first exhaust pipe with burn the system connection, closed carbon black separation tank passes through drain line and is connected with heat transfer system.
The beneficial effect of adopting the further scheme is that: the closed carbon black separating tank is adopted, and then the VOC gas in the carbon black separating tank is burnt completely by utilizing the burning system, so that the purpose of environmental protection is achieved.
Further, the heat exchange system adopts a closed heat exchange cooling system; the closed heat exchange cooling system adopts one cooler or a plurality of coolers used in series or a plurality of coolers used in parallel.
The beneficial effect of adopting the further scheme is that: the carbon black water hyperbolic cooling tower in the original process is replaced by a closed heat exchange system, and the closed heat exchange system can be provided with one cooler or two coolers which are connected in series or in parallel for use according to the treatment capacity of the carbon black water. The closed heat exchange system replaces a hyperbolic cooling tower, prevents the VOC gas volatilized by the carbon black water from polluting the atmosphere, and further achieves the purpose of environmental protection.
Further, closed carbon black separating tank includes cell body and apron, the apron is sealed to be set up at the opening end of cell body.
Further, install the second draught fan on the first exhaust pipeline, install the pump on the exhaust pipeline. The exhaust or drainage efficiency can be improved by arranging an induced draft fan or a pump.
Further, the incineration system comprises an RTO incinerator and a chimney, and the RTO incinerator is connected with the chimney through a second exhaust pipeline.
The beneficial effect of adopting the further scheme is that: the VOC gas in the carbon black separation tank can be completely burned by the RTO incinerator to achieve the purpose of environmental protection, and the burned environmental protection gas is discharged through a chimney.
Further, a third induced draft fan is installed on the second exhaust pipeline.
The beneficial effect of adopting the further scheme is that: the exhaust efficiency can be improved through setting up the draught fan.
Further, the air preheating system comprises a preheater, a condensate water inlet pipe and a condensate water outlet pipe; one end of the condensate water inlet pipe is connected with the condensate receiver, and the other end of the condensate water inlet pipe is connected with the tube pass water inlet of the preheater; one end of the condensate water outlet pipe is connected with a pipe pass water outlet of the preheater, and the other end of the condensate water outlet pipe is connected with a condensate post-treatment system; the shell side of the preheater is connected with the oxygen preheating furnace and the natural gas preheating furnace and preheats air entering the oxygen preheating furnace and air entering the natural gas preheating furnace.
The beneficial effect of adopting the further scheme is that: the air is preheated by the condensate generated by other parts of the device, and the condensate which needs to be cooled can be recycled firstly, and then is cooled, so that the energy is saved.
Further, the condensate receiver comprises a condensate receiver in an acetylene plant utility, and the condensate aftertreatment system comprises a cooling device and a condensate storage tank. The condensate receiver in the acetylene device public works can be condensate generated in a concentration unit, a partial oxidation unit, a boiler or other parts of a system, and the condensate generated in the parts can be recycled, cooled by a cooling device and collected by a condensate storage tank to be used by other users. The heat of the condensate is recycled.
Further, the burners on the oxygen preheating furnace and the natural gas preheating furnace are respectively connected with a fuel gas pipeline and a combustion-supporting air pipeline, and the combustion-supporting air pipeline is connected with a first induced draft fan; the air preheating system is connected with the combustion-supporting air pipeline and preheats air sent into the corresponding combustor.
The beneficial effect of adopting the further scheme is that: the first induced draft fan provides pressure for combustion air, replaces the natural air inlet mode with the forced air inlet mode, can avoid leading to the furnace negative pressure not enough because of the long-time back boiler tube deposition of operation of preheating furnace to lead to the intake not enough to make the unstable problem of burning, thereby lead to the fact the frequent interlocking phenomenon of device.
Furthermore, a first flow control valve and a first flow meter are arranged on the fuel gas pipeline, thermocouples are connected to the feed gas outlet furnace tubes of the oxygen preheating furnace and the natural gas preheating furnace, and the thermocouples and the first flow meter are respectively connected with the first flow control valve; and a second flowmeter and a second flow control valve are arranged on the combustion-supporting air pipeline, and the second flowmeter is respectively connected with the first flowmeter and the second flow control valve.
The beneficial effect of adopting the further scheme is that: the flow meter and the flow control valve are arranged on the fuel gas pipeline, so that the fuel gas flow can be adjusted according to the preheating furnace temperature fed back by the thermocouple, and the fuel gas discharging temperature and the fuel gas flow cascade control fuel gas flow are realized. The flow meter and the flow control valve are respectively arranged on the fuel gas pipeline and the combustion-supporting air pipeline, so that the ratio of fuel gas and air and the air flow can be controlled in a cascade mode to control the quantity of combustion-supporting air, and the quantity of combustion-supporting air can be automatically adjusted in real time along with the change of heat load. The combustion-supporting air quantity can also be controlled by a second flow control valve on the combustion-supporting air pipeline, and the combustion-supporting air quantity adjusting precision is high.
Further, an oxygen analyzer for detecting residual oxygen amount is arranged in an exhaust chimney of each of the oxygen preheating furnace and the natural gas preheating furnace.
The beneficial effect of adopting the further scheme is that: the oxygen analyzer can realize the on-line monitoring of the residual oxygen amount and correct the flow ratio of the fuel gas and the air at any time. The residual oxygen amount in the flue gas of the preheating furnace can be accurately controlled, and the heat efficiency of the preheating furnace is ensured.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
Example 1
As shown in fig. 1 to fig. 3, the system for preparing acetylene by partial oxidation of natural gas in an efficient, energy-saving and environment-friendly manner in this embodiment includes an air preheating system, a natural gas preheating furnace F2, an oxygen preheating furnace F1, an acetylene cracking furnace D1, a washing tower E1, a carbon black separation system, and a heat exchange system, where the air preheating system is respectively connected to the oxygen preheating furnace F1 and the natural gas preheating furnace F2 and preheats air entering the oxygen preheating furnace F1 and air entering the natural gas preheating furnace F2; the oxygen preheating furnace F1 and the natural gas preheating furnace F2 are respectively connected with an air inlet of the acetylene cracking furnace D1, an air outlet of the acetylene cracking furnace D1 is connected with the washing tower E1, a carbon black water discharge port of the acetylene cracking furnace D1 and a washing object discharge port of the washing tower E1 are respectively connected with the carbon black separation system, and the carbon black separation system is connected with the heat exchange system.
According to the embodiment, the air preheating system is arranged at the air inlets of the burners of the natural gas preheating furnace and the oxygen preheating furnace, the heat source used by the air preheating system is high-temperature condensate rich in acetylene devices, and the high-temperature condensate is provided with a pressure head, so that the air preheating system does not need to be additionally provided with power equipment. The air preheating system makes full use of the abundant heat source of the whole device, and achieves the purpose of energy conservation.
As shown in fig. 1, the carbon black separation system of this embodiment includes a closed type carbon black separation tank C1 and an incineration system, the carbon black water discharge port of the acetylene cracking furnace D1 and the washings discharge port of the washing tower E1 are respectively connected to the closed type carbon black separation tank C1, the closed type carbon black separation tank C1 is connected to the incineration system through a first exhaust pipeline, and the closed type carbon black separation tank C1 is connected to a heat exchange system through a drain pipeline. The closed carbon black separating tank is adopted, and then the VOC gas in the carbon black separating tank is burnt completely by utilizing the burning system, so that the purpose of environmental protection is achieved.
As shown in fig. 1, the closed carbon black separation tank C1 of the present embodiment includes a tank body and a cover plate, and the cover plate is hermetically disposed at an open end of the tank body.
As shown in fig. 1, the heat exchange system of the present embodiment employs a closed heat exchange cooling system. The closed heat exchange cooling system adopts one cooler or a plurality of coolers used in series. The carbon black water hyperbolic cooling tower in the original process is replaced by a closed heat exchange system, and the closed heat exchange system can be provided with one cooler or two coolers which are connected in series or in parallel for use according to the treatment capacity of the carbon black water. The closed heat exchange system replaces a hyperbolic cooling tower, prevents the VOC gas volatilized by the carbon black water from polluting the atmosphere, and further achieves the purpose of environmental protection.
As shown in fig. 1, the incineration system of the present embodiment includes an RTO incinerator F3 and a chimney Z1, and the RTO incinerator F3 is connected to the chimney Z1 through a second exhaust pipe. The VOC gas w11 in the carbon black separating tank can be burnt completely by the RTO incinerator to achieve the purpose of environmental protection, and the burnt environmental protection gas is discharged through a chimney.
As shown in fig. 1, a second induced draft fan P2 is installed on the first exhaust pipeline of the present embodiment, and a pump P4 is installed on the exhaust pipeline. And a third induced draft fan P3 is installed on the second exhaust pipeline. The exhaust and drainage efficiency can be improved by arranging the induced draft fan and the pump.
In the present embodiment, the natural gas w2 and the oxygen w1 are subjected to oxidation reaction, cracking reaction, and side reaction in the acetylene cracking furnace D1, respectively, and the first acetylene cracking gas w9 generated in the acetylene cracking furnace D1 mainly includes acetylene, carbon monoxide, hydrogen, higher acetylene, carbon black, and the like. The oxidation reaction is that hydrocarbon gas reacts with oxygen to generate carbon monoxide and hydrogen, the carbon monoxide reacts with oxygen to generate carbon dioxide, and the hydrogen reacts with oxygen to generate water. The cracking reaction is the thermal decomposition of hydrocarbon gas into acetylene and hydrogen. A side reaction is the thermal decomposition of acetylene into carbon and hydrogen. Natural gas w2 and oxygen w1 enter from the inlet of a mixing chamber D101 of an acetylene cracking furnace D1, are uniformly mixed in the mixing chamber D101, and are prepared for entering a burner D102 for combustion. Acetylene cracking gas is discharged from the side part of the quenching chamber, the discharge temperature is 80-90 ℃, and the acetylene concentration (dry gas) is 7-9%. After natural gas w2 and oxygen w1 are cracked in an acetylene cracking furnace D1 and then quenched in a quenching chamber D103, generated carbon black water w8 enters a closed carbon black separation tank C1.
The present embodiment has the following advantages: (1) pure energy conservation: the selected heat source is completely waste heat, the energy-saving system does not increase any additional equipment with energy consumption, and the energy-saving system is driven to stably run by parameter balance of the energy-saving system and the margin of a smoke wind resistance system designed by the preheating furnace. (2) The operation elasticity is big, and it is convenient to use the maintenance, long service life, pre-heater 20 years. (3) The condensate heating system for remote conveying adopts a desuperheating water cooling conveying technology to prevent water hammer. (4) Bidirectional energy conservation: the preheating furnace device realizes energy conservation, and the device for providing a waste heat source also saves energy. (5) The pressure loss of the air path of the preheater is less than 40Pa, which is the key to the safe operation or success of the energy-saving system. (6) The whole process system adopts an unbalanced pressure loss method to ensure that the air temperature at the outlet of each path of preheater is consistent. (7) The energy-saving benefit is obvious, the total fuel consumption of the preheating furnace can be reduced by 2-2.5%, and the smoke emission is reduced. (8) The energy-saving system completely adopts static equipment, has no three-waste discharge, is simple and convenient to maintain, has no additional personnel, has no high-speed, high-temperature and high-pressure equipment, and has extremely high working reliability.
Example 2
On the basis of embodiment 1, as shown in fig. 1, the system for preparing acetylene by partial oxidation of natural gas in an efficient, energy-saving and environment-friendly manner further comprises a washing tower E1 and an electric filter S1, wherein a quenching chamber D103 of the acetylene cracking furnace D1 is connected with the washing tower E1, and a first acetylene cracking gas w9 is fed into the washing tower E1 for washing to obtain a second acetylene cracking gas w10, and the washing tower E1 is connected with the electric filter S1, and a second acetylene cracking gas w10 after washing is fed into the electric filter S1 for dust removal; the washing tower E1 and the electric filter S1 are respectively connected with the carbon black separation system and convey the carbon black products obtained by washing and dedusting to the carbon black separation system. The first acetylene cracking gas in the quenching chamber can be washed and dedusted by using the washing tower and the electric filter, and the scrubbed cracking gas can be input into the scrubber again for repeated washing after being dedusted by the electric filter. The washing tower can be connected with a compression unit K1 and a concentration unit T1, the washed and dedusted second diacetylene pyrolysis gas w10 in the washing tower sequentially enters the compression unit K1 and the concentration unit T1, and acetylene with the purity of more than 99.1% is obtained after the absorption and desorption processes of the concentration unit T1.
Example 3
On the basis of embodiment 1, this embodiment further describes an air preheating system. The air preheating system of the embodiment comprises a preheater A1, a condensate water inlet pipe and a condensate water outlet pipe; one end of the condensate water inlet pipe is connected with the condensate receiver 1, and the other end of the condensate water inlet pipe is connected with a pipe pass water inlet of the preheater A1; one end of the condensate water outlet pipe is connected with a pipe pass water outlet of the preheater A1, and the other end of the condensate water outlet pipe is connected with the condensate post-treatment system 2; the shell side of the preheater A1 is connected to an oxygen preheater F1 and a natural gas preheater F2 and preheats air entering the oxygen preheater F1 and air entering the natural gas preheater F2.
Wherein the condensate receiver comprises a condensate receiver in an acetylene plant utility, the condensate aftertreatment system 2 comprises a cooling device 21 and a condensate storage tank 22, as shown in fig. 3. The condensate receiver in the acetylene apparatus utility can be condensate generated in a concentration unit, a partial oxidation unit, a boiler or other parts of the system, and the condensate generated in the parts can be recycled and reused, and then cooled by the cooling device 21 and collected by the condensate storage tank 22 to be used by other users. The heat of the condensate is recycled. The condensate generated by the condensate receiver in the acetylene device public works is utilized to preheat the air, and the condensate which needs to be cooled can be recycled firstly and then cooled, so that the energy is saved.
Example 4
As shown in fig. 1 to 3, in addition to embodiment 1 or embodiment 2, the present embodiment describes a connection pipeline between an oxygen preheating furnace and a natural gas preheating furnace. In the embodiment, the burners of the oxygen preheating furnace and the natural gas preheating furnace are respectively connected with a fuel gas pipeline and a combustion-supporting air pipeline, and the combustion-supporting air pipeline is connected with a first induced draft fan P1; the air preheating system is connected with the combustion-supporting air pipeline and preheats air sent into the corresponding combustor. First draught fan P1 provides pressure for combustion air, avoids leading to the combustion air of combustor not enough, leads to the unstable problem of burning.
As shown in fig. 1 and fig. 2, a specific scheme of the present embodiment is that a fuel gas pipeline and a combustion-supporting air pipeline are connected to a first burner 21 of the natural gas preheating furnace 2, and a fuel gas pipeline and a combustion-supporting air pipeline are also connected to a second burner 31 of the oxygen preheating furnace 3. The fuel gas pipeline and the combustion-supporting air pipeline of the first combustor 21 and the second combustor 31 have the same structure, which is specifically shown as follows.
As shown in fig. 2, a first flow control valve m5 and a first flow meter m6 are arranged on the fuel gas pipeline, a thermocouple m7 is connected to the raw material gas outlet furnace tubes of the oxygen preheating furnace 3 and the natural gas preheating furnace 2, and the thermocouple m7 and the first flow meter m6 are respectively connected to the first flow control valve m 5; and a second flow meter m2 and a second flow control valve m1 are arranged on the combustion-supporting air pipeline, and the second flow meter m2 is respectively connected with the first flow meter m6 and the second flow control valve m 1. The fuel gas pipeline can be controlled in cascade through the thermal feedback of the first flow control valve and the thermocouple, the fuel gas flow of the fuel device pipeline can be adjusted by directly utilizing the first flow control valve, and the fuel gas flow can also be adjusted through the temperature fed back by the thermocouple. The combustion-supporting air quantity on the combustion-supporting air pipeline can be controlled in a cascade mode through the second flow control valve and the flow of the fuel gas, the flow of the combustion-supporting air on the combustion-supporting air pipeline can be adjusted through the second flow control valve directly, the flow of the combustion-supporting air can also be adjusted through the fuel gas quantity (the introducing proportion of the combustion-supporting air and the fuel gas is determined before the preheating furnace operates), and the introduced air quantity is determined according to the introduced fuel gas quantity and the preset proportion.
In this embodiment, the thermocouple m7 and the first flow meter m6 may be connected to the first flow control valve m5 by a PLC or DCS control system, respectively, and the second flow meter m2 may be connected to the first flow meter m6 and the second flow control valve m1 by a PLC or DCS control system, respectively. The thermocouple can feed back a temperature signal to the PLC or DCS control system, and the PLC or DCS control system controls the opening of the first flow regulating valve according to the temperature signal so as to regulate the fuel gas flow. The opening degree of the first flow regulating valve m5 can also be directly regulated on a DCS system of the central control room, so that the fuel gas flow is regulated. When the flow of the fuel gas changes, the PLC or the DCS control system can control the flow of the combustion-supporting air according to the opening degree of a second flow control valve m1 on the combustion-supporting air pipeline of the fuel gas flow control. Of course, the opening degree of the second flow regulating valve m1 can also be directly regulated on the DCS system of the central control room, so that the flow of the combustion-supporting air is regulated.
And the fuel gas pipeline is also provided with a cut-off valve m 9. The fuel gas line can be shut off depending on the operating conditions. And a first pressure gauge m10 is also arranged on the fuel gas pipeline. The pressure of the fuel gas line can be monitored. And a blower m3 is arranged on the combustion-supporting air pipeline. Provide pressure for combustion air, avoid resulting in the combustor combustion air not enough, lead to the unstable problem of burning. The air inlet end of the blower m3 is provided with a silencer m 4. Low noise air intake can be achieved. And a second pressure gauge m11 is further arranged on the combustion-supporting air pipeline. The pressure of the combustion-supporting air pipeline can be monitored. And an ignition fuel gas pipeline is arranged on the fuel gas pipeline, two ends of the ignition fuel gas pipeline are respectively communicated with the fuel gas pipeline and the pilot burner of the first combustor or the pilot burner of the second combustor, and a pressure regulating valve m14 is arranged on the ignition fuel gas pipeline.
As shown in fig. 2, an oxygen analyzer m8 for detecting the residual oxygen amount is provided in an exhaust stack m12 of each of the oxygen preheater 3 and the natural gas preheater 2. The oxygen analyzer can realize the on-line monitoring of the residual oxygen amount, can correct the flow ratio of the fuel gas and the air at any time, can accurately control the residual oxygen amount in the flue gas of the preheating furnace, and ensures the thermal efficiency of the preheating furnace. Utilize the oxygen analysis appearance can monitor the residual oxygen volume of exhaust chimney, because there is the surplus air to exist after the fuel gas burning in the preheater, and the combustion-supporting amount of wind that the combustion-supporting air pipeline let in can influence final residual oxygen volume, the residual oxygen volume is too many to explain to let in combustion-supporting amount of wind too much, can take away the heat of preheater, the residual oxygen volume is too little also not the ideal mixed state of fuel gas and combustion-supporting wind, can generate carbon monoxide easily, be unfavorable for the environmental protection. Therefore, the residual oxygen amount of the exhaust gas can be monitored by arranging the oxygen analyzer, and the flow ratio of the fuel gas and the combustion-supporting air is corrected at any time according to the residual oxygen amount, so that the introduced amount of the combustion-supporting air is controlled within a reasonable range.
The fuel gas sequentially passes through a first flowmeter m6, a first flow control valve m5 and a stop valve m9 of the fuel gas pipeline and finally enters a first combustor or a second combustor, a first pressure gauge m10 is further arranged on the fuel gas pipeline and used for monitoring the pressure of the fuel gas, and a thermocouple m7 is arranged on a fuel gas outlet pipeline of the preheating furnace. And combustion-supporting air enters a combustion-supporting air pipeline through a blower m3, and enters the first combustor or the second combustor through a second flow meter m2, a second flow control valve m1 and a second pressure meter m11 to be mixed with fuel gas.
The working process of the system for preparing acetylene by partial oxidation of natural gas in the embodiment is that fuel gas and preheated air are respectively conveyed to respective burners of an oxygen preheating furnace and an acetylene cracking furnace through a combustion-supporting air pipeline and a fuel gas pipeline, the fuel gas and the preheated air are combusted in the burners to provide heat for the preheating furnace, and the oxygen and natural gas are preheated to prepare for a subsequent acetylene cracking furnace. The preheated oxygen and natural gas enter an acetylene cracking furnace to carry out cracking reaction, acetylene cracking gas is discharged after being washed by a washing tower, carbon black water enters a carbon black separation system to separate carbon black, and the carbon black water enters a closed heat exchange cooling system through a drainage pipeline to be cooled and then goes to relevant equipment. The gas that carbon black piece-rate system volatilizes burns through RTO incinerator, burns the VOC gas in the carbon black separating tank totally, reaches the purpose of environmental protection to the environmental protection gas discharge after will burning through the chimney.
The system for preparing acetylene by partial oxidation of natural gas with high efficiency, energy conservation and environmental protection is adopted to prepare acetylene, the condensate inflow rate of a preheater of an air preheating system is 25-30 t/h, the inlet temperature of the condensate is 120 ℃, the inlet pressure (pressure after pumping) of the condensate is 0.85MPaG, the temperature of combustion-supporting air can reach more than 100 ℃, the pressure difference of an inlet and an outlet of the condensate is less than or equal to 60KPa, and the air pressure loss of the preheater is less than or equal to 40 Pa. The amount of natural gas saved by a single-row furnace is shown in Table 1, and the fuel gas can be saved by 12.52Nm all year round under normal working conditions when acetylene is prepared by adopting the process disclosed by the invention3/h。
Note: 1. the fuel gas saving amount is calculated according to the normal working condition; 2. the temperature rise is the average temperature rise throughout the year.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.