阅读说明：本技术 评价耐火材料整体隔热性能的试验装置及试验方法 (Test device and test method for evaluating overall heat insulation performance of refractory material ) 是由 薛飞 许谦 易帅 邓丽娜 潘传才 林国伟 张航 司国栋 陈美娜 蒋晨 谢金莉 于 2021-09-24 设计创作，主要内容包括：本发明公开了一种评价耐火材料整体隔热性能的试验装置及试验方法,属于耐火材料领域。包括炉壳和炉盖,壳的底壁内通过耐火砖水平铺设得到第一耐火砖层,炉壳的侧壁内通过耐火砖环形摆设得到第二耐火砖层,耐火砖的耐火端朝向炉壳内部,第一耐火砖层和第二耐火砖层围成向上开口的腔体；炉盖下方设置有加热装置和第一组测温探头,炉盖密封覆盖在炉壳上端的敞口上,加热装置伸进腔体内,第一组测温探头在炉壳内与耐火砖上设定的测温点接触；炉壳的侧壁外表面上设置有第二组测温探头,第一组测温探头和第二组测温探头与测温装置连接。本发明客观表征耐火材料在窑炉服役的温度环境,模拟实际的窑炉工艺情况,准确评价耐火材料的整体传热性能。(The invention discloses a test device and a test method for evaluating the integral heat-insulating property of a refractory material, and belongs to the field of refractory materials. The furnace comprises a furnace shell and a furnace cover, wherein a first refractory brick layer is horizontally laid in the bottom wall of the shell through refractory bricks, a second refractory brick layer is annularly laid in the side wall of the furnace shell through refractory bricks, the refractory ends of the refractory bricks face the inside of the furnace shell, and the first refractory brick layer and the second refractory brick layer enclose a cavity with an upward opening; a heating device and a first group of temperature measuring probes are arranged below the furnace cover, the furnace cover is hermetically covered on an opening at the upper end of the furnace shell, the heating device extends into the cavity, and the first group of temperature measuring probes are contacted with temperature measuring points set on the refractory bricks in the furnace shell; and a second group of temperature probes are arranged on the outer surface of the side wall of the furnace shell, and the first group of temperature probes and the second group of temperature probes are connected with a temperature measuring device. The method objectively represents the temperature environment of the refractory material in the service of the kiln, simulates the actual process condition of the kiln, and accurately evaluates the overall heat transfer performance of the refractory material.)

1. The utility model provides an evaluation refractory material is test device of heat-proof quality entirely which characterized in that, includes stove outer covering and bell, wherein:

the furnace shell is provided with an opening at the upper end, a first refractory brick layer is horizontally paved in the bottom wall of the furnace shell through refractory bricks, a second refractory brick layer is annularly paved in the side wall of the furnace shell through refractory bricks, the refractory ends of the refractory bricks in the first refractory brick layer and the second refractory brick layer face the inside of the furnace shell, and the first refractory brick layer and the second refractory brick layer enclose a cavity with an upward opening;

a heating device and a first group of temperature measuring probes are arranged below the furnace cover, the furnace cover is covered on an opening at the upper end of the furnace shell in a sealing manner, the heating device extends into the cavity, and the first group of temperature measuring probes are in contact with temperature measuring points set on the refractory bricks in the furnace shell;

and a second group of temperature probes are arranged on the outer surface of the side wall of the furnace shell, and the first group of temperature probes and the second group of temperature probes are connected with a temperature measuring device.

2. The test device for evaluating the overall heat insulation performance of the refractory material according to claim 1, wherein the refractory bricks are composite refractory bricks, the composite refractory bricks comprise a refractory layer, a heat insulation layer and a heat insulation layer which are sequentially and integrally formed, and the refractory layer of the composite refractory bricks faces to the inside of the furnace shell.

3. The test device for evaluating the overall heat insulation performance of the refractory material according to claim 2, wherein the temperature measuring points are arranged on the refractory layer, the heat insulation layer and the heat insulation layer, and temperature measuring holes for inserting the first group of temperature measuring probes are drilled at the temperature measuring points.

4. The test apparatus for evaluating the overall heat insulation performance of the refractory material according to claim 1, wherein the refractory bricks are homogeneous refractory bricks, and the homogeneous refractory bricks comprise an insulation layer unit, a thermal insulation layer unit and a refractory layer unit which are separated from each other, and the insulation layer unit, the thermal insulation layer unit and the refractory layer unit are sequentially arranged inside the furnace shell from outside to inside.

5. The test device for evaluating the overall heat insulation performance of the refractory material according to claim 4, wherein the temperature measuring points are arranged on the refractory layer unit, the thermal insulation layer unit and the thermal insulation layer unit, and temperature measuring holes for inserting the first group of temperature measuring probes are drilled at the temperature measuring points.

6. The test apparatus for evaluating the overall thermal insulation performance of a refractory according to claim 1, wherein the refractory bricks in the first and second refractory brick layers are bonded by fire clay.

7. The test device for evaluating the integral heat insulation performance of the refractory material according to any one of claims 1 to 6, wherein the second group of temperature probes are adsorbed on the outer surface of the side wall of the furnace shell by magnetic force, or an installation groove is formed on the outer surface of the side wall of the furnace shell, and the second group of temperature probes are arranged in the installation groove.

8. The testing device for evaluating the integral heat insulation performance of the refractory material according to claim 7, wherein the furnace shell and the furnace cover are made of steel, the furnace shell is cylindrical, the heating device is a heating rod, the first group of temperature probes are thermocouple probes, the second group of temperature probes are thermal resistance probes, and the temperature measuring device is a multi-channel composite inspection temperature measuring device.

9. A test method of the test apparatus for evaluating the overall heat insulating performance of a refractory according to any one of claims 1 to 8, wherein the method comprises:

s1: hoisting the furnace cover by using a crane;

s2: horizontally laying refractory bricks along the inner wall of the bottom wall of the furnace shell, and enabling the refractory ends of the refractory bricks to face the inside of the furnace shell to obtain a first refractory brick layer;

s3: arranging refractory bricks on the first refractory brick layer in an annular mode along the inner side wall of the furnace shell, and enabling the refractory ends of the refractory bricks to face the inner side of the furnace shell to obtain a second refractory brick layer;

s4: the furnace cover is hermetically covered on an opening at the upper end of the furnace shell, the heating device extends into the cavity, and the first group of temperature measuring probes are contacted with the temperature measuring points set on the refractory bricks in the furnace shell;

s5: setting a heating rate and a heating temperature, starting a heating device, and starting heating operation;

s6: measuring the temperatures of the first group of temperature measuring probes and the second group of temperature measuring probes by using a temperature measuring device, and recording the temperature values of the first group of temperature measuring probes and the second group of temperature measuring probes after the temperatures of the first group of temperature measuring probes and the second group of temperature measuring probes are stable;

s7: and drawing a temperature change curve of each position of the refractory brick according to each recorded temperature value, and evaluating the overall heat insulation performance of the refractory material according to the temperature change curve.

10. The method as claimed in claim 9, wherein in S2, the refractory bricks are bonded by the fire clay, and in S3, the refractory bricks are bonded by the fire clay.

Technical Field

The invention relates to the field of refractory materials, in particular to a test device and a test method for evaluating the overall heat insulation performance of a refractory material.

Background

The refractory material is a kiln lining material commonly used in a thermal kiln, and is one of indispensable functional materials for guaranteeing the safe production of the kiln. The design, configuration, construction and application of the refractory material affect the service life of the industrial kiln and also determine the heat insulation effect of the kiln.

In the prior art, kiln design workers calculate temperatures of different layers, such as an insulating layer, a heat-insulating layer and a fire-resistant layer, according to the heat conductivity coefficient of a homogeneous system refractory brick and a theoretical temperature in a kiln, and design the kiln by referring to relevant data of the temperatures. However, the temperature of different layers calculated theoretically is often different from the actual temperature, the service life of the kiln is influenced, and the integral heat insulation performance of the refractory material is reduced.

In addition, with the increasing awareness of energy conservation and consumption reduction, the requirements of the thermal kiln on energy conservation are higher and higher, and for the requirements, new energy-saving varieties of corresponding refractory materials emerge endlessly. The structure function integrated multilayer composite refractory material is a main variety, generally comprises a refractory layer and an insulating layer, and some products also comprise a heat-insulating layer. The fire-resistant layer, the heat-insulating layer and the heat-insulating layer are integrally formed by adopting a synchronous forming and synchronous sintering process. Because the composite refractory material is composed of materials of different layers, the heat transfer capacity of the material is uneven, and the result deviation of theoretically calculating the temperature of different layers is larger.

Disclosure of Invention

In order to solve the technical problems, the invention provides a test device and a test method for evaluating the overall heat insulation performance of a refractory material, which objectively represent the temperature environment of the refractory material in service in a kiln, simulate the actual process condition of the kiln and accurately evaluate the overall heat transfer performance of the refractory material.

The technical scheme provided by the invention is as follows:

a test device for evaluating the integral heat insulation performance of a refractory material comprises a furnace shell and a furnace cover, wherein:

the furnace shell is provided with an opening at the upper end, a first refractory brick layer is horizontally paved in the bottom wall of the furnace shell through refractory bricks, a second refractory brick layer is annularly paved in the side wall of the furnace shell through refractory bricks, the refractory ends of the refractory bricks in the first refractory brick layer and the second refractory brick layer face the inside of the furnace shell, and the first refractory brick layer and the second refractory brick layer enclose a cavity with an upward opening;

a heating device and a first group of temperature measuring probes are arranged below the furnace cover, the furnace cover is covered on an opening at the upper end of the furnace shell in a sealing manner, the heating device extends into the cavity, and the first group of temperature measuring probes are in contact with temperature measuring points set on the refractory bricks in the furnace shell;

and a second group of temperature probes are arranged on the outer surface of the side wall of the furnace shell, and the first group of temperature probes and the second group of temperature probes are connected with a temperature measuring device.

Furthermore, resistant firebrick is compound resistant firebrick, compound resistant firebrick is including setting gradually and integrated into one piece's flame retardant coating, insulating layer and heat preservation, compound resistant firebrick's flame retardant coating orientation inside the stove outer covering.

Furthermore, the temperature measuring points are arranged on the fire-resistant layer, the thermal insulation layer and the heat preservation layer, and temperature measuring holes for the first group of temperature measuring probes to be inserted are drilled at the temperature measuring points.

Furthermore, the refractory bricks are homogeneous refractory bricks, each homogeneous refractory brick comprises a heat insulation layer unit, a heat insulation layer unit and a fire-resistant layer unit which are mutually separated, and the heat insulation layer unit, the heat insulation layer unit and the fire-resistant layer unit are sequentially arranged in the furnace shell from outside to inside.

Furthermore, the temperature measuring points are arranged on the fire-resistant layer unit, the thermal insulation layer unit and the thermal insulation layer unit, and temperature measuring holes for the first group of temperature measuring probes to be inserted are drilled at the temperature measuring points.

Further, the refractory bricks in the first refractory brick layer and the second refractory brick layer are bonded through fire clay.

Furthermore, the second group of temperature measuring probes are adsorbed on the outer surface of the side wall of the furnace shell through magnetic force, or an installation groove is formed in the outer surface of the side wall of the furnace shell, and the second group of temperature measuring probes are arranged in the installation groove.

Further, the material of stove outer covering and bell is the steel, the shape of stove outer covering is cylindrical, heating device is the heating rod, first group temperature probe is thermocouple probe, second group temperature probe is the thermal resistance probe, temperature measuring device patrols and examines temperature measuring device for the multichannel is compound.

A test method of the test apparatus for evaluating the overall heat insulation performance of a refractory, the method comprising:

s1: hoisting the furnace cover by using a crane;

s2: horizontally laying refractory bricks along the inner wall of the bottom wall of the furnace shell, and enabling the refractory ends of the refractory bricks to face the inside of the furnace shell to obtain a first refractory brick layer;

s3: arranging refractory bricks on the first refractory brick layer in an annular mode along the inner side wall of the furnace shell, and enabling the refractory ends of the refractory bricks to face the inner side of the furnace shell to obtain a second refractory brick layer;

s4: the furnace cover is hermetically covered on an opening at the upper end of the furnace shell, the heating device extends into the cavity, and the first group of temperature measuring probes are contacted with the temperature measuring points set on the refractory bricks in the furnace shell;

s5: setting a heating rate and a heating temperature, starting a heating device, and starting heating operation;

s6: measuring the temperatures of the first group of temperature measuring probes and the second group of temperature measuring probes by using a temperature measuring device, and recording the temperature values of the first group of temperature measuring probes and the second group of temperature measuring probes after the temperatures of the first group of temperature measuring probes and the second group of temperature measuring probes are stable;

s7: and drawing a temperature change curve of each position of the refractory brick according to each recorded temperature value, and evaluating the overall heat insulation performance of the refractory material according to the temperature change curve.

Further, in S2, the refractory bricks are bonded by the fire clay, and in S3, the refractory bricks are bonded by the fire clay.

The invention has the following beneficial effects:

according to the invention, the temperature change curves of all points are obtained objectively and accurately by simulating the actual service condition of the refractory material in the kiln, the temperature condition of the refractory material used in the kiln is visually represented, the overall heat transfer performance of the refractory material is systematically and objectively evaluated, the accuracy of the heat conduction test of the refractory material is improved, and considerable economic benefits are created for refractory material enterprises, so that the method has important significance. And the temperature in the test device is controllable, safe and reliable, and the cost is lower. The furnace body can be built by refractory bricks with different sizes, is suitable for the refractory bricks of various homogeneous systems and heterogeneous systems, does not require isotropy and homogeneity of the refractory bricks, and enlarges the test range of the tested refractory materials. In the test process, the temperature rise temperature and the temperature rise rate have no any limit on the result of the invention, and the result is stable and has good consistency.

Drawings

FIG. 1 is an exploded view of a test apparatus for evaluating the overall heat insulating performance of a refractory according to the present invention;

FIG. 2 is a perspective view of a testing apparatus for evaluating the overall heat insulating performance of a refractory according to the present invention;

FIG. 3 is a top view of the furnace shell.

Detailed Description

In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

Example 1:

the embodiment of the invention provides a test device for evaluating the integral heat insulation performance of a refractory material, which comprises a furnace shell 1 and a furnace cover 2, as shown in figures 1-3, wherein:

the furnace shell 1 and the furnace cover 2 can be made of steel, the furnace shell 1 can be cylindrical, the upper end of the furnace shell is open, the furnace shell 1 and the furnace cover 2 form a high-temperature cylindrical test furnace, and the temperature rise range of the test furnace is 100-1500 ℃.

The furnace body is built by the tested refractory bricks in the furnace shell 1, wherein: lay through resistant firebrick level and can obtain first firebrick layer 3 through the firebrick bonding in the diapire of stove outer covering 1, through resistant firebrick annular in the lateral wall of stove outer covering 1 set up and can obtain second firebrick layer 4 through the firebrick bonding, firebrick's in first firebrick layer 3 and the second firebrick layer 4 fire-resistant end 5 is inside towards stove outer covering 1, first firebrick layer 3 and second firebrick layer 4 build into the furnace body by laying bricks or stones, first firebrick layer 3 and second firebrick layer 4 enclose into the cavity 6 of upwards opening.

The thickness and the height of the furnace body are adjusted through the using amount of the refractory bricks, the thickness of the furnace body built by the refractory bricks can select single-layer or multi-layer refractory bricks, and the height of the furnace body can be adjusted through the number of layers of the refractory bricks.

The heating device 7 and the first group of temperature probes 8 are arranged below the furnace cover 2, the heating device 7 can be a heating rod, the heating rod can be a silicon carbide rod or a silicon molybdenum rod, the heating rod is selected according to the temperature, and the heating rod is installed on the furnace cover and moves along with the furnace cover.

The first group of temperature probes 8 can be thermocouple probes, the thermocouple precision is controlled within +/-1 ℃, for example, B, S, K type thermocouples, and the number of the temperature probes is several.

The furnace cover 2 is hermetically covered on an opening at the upper end of the furnace shell 1, the heating device 7 extends into the cavity 6, and the first group of temperature measuring probes 8 are contacted with temperature measuring points set on refractory bricks in the furnace shell 1.

The outer surface of the side wall of the furnace shell 1 is provided with a second group of temperature probes 9, and the first group of temperature probes 8 and the second group of temperature probes 9 are connected with a temperature measuring device.

The second group of thermometric probes 9 may be thermal resistance probes, for example Pt100 type thermal resistance, in number.

The first group of temperature measuring probes 8 and the second group of temperature measuring probes 9 are connected in the test furnace body or on the surface of the test furnace body to test the lateral or bottom heat transfer condition of the refractory bricks.

The using method of the invention is as follows:

the furnace lid 2 is first lifted by a crane.

Then build by laying bricks or stones the furnace body according to predesign, the centre sets up the cavity, specifically includes: horizontally laying refractory bricks along the inner water of the bottom wall of the furnace shell 1, enabling the refractory ends of the refractory bricks to face the inside of the furnace shell 1 (namely the refractory ends are vertically upward), and bonding the refractory bricks by using fire clay to obtain a first refractory brick layer 3; arranging refractory bricks on the laid first refractory brick layer 3 in an annular manner along the side wall of the furnace shell 1, enabling the refractory ends of the refractory bricks to face the inside of the furnace shell 1 (namely the refractory ends horizontally face the middle), and bonding the refractory bricks by using fire clay to obtain a second refractory brick layer 4; the first refractory brick layer 3 and the second refractory brick layer 4 enclose a cavity 6 which is open upwards.

And then the furnace cover 2 is hermetically covered on the opening at the upper end of the furnace shell 1 and is locked with the furnace shell, the heating device 7 extends into the cavity, and the first group of temperature measuring probes 8 are contacted with the temperature measuring points set on the refractory bricks in the furnace shell 1.

Setting the heating rate and the heating temperature, starting the heating device 7, starting the heating operation, and simultaneously starting the temperature measuring device.

The temperature measuring device is used for measuring the temperatures of the first group of temperature measuring probes 8 and the second group of temperature measuring probes 9, and after the temperatures of the first group of temperature measuring probes 8 and the second group of temperature measuring probes 9 are stable, the temperature values of the first group of temperature measuring probes 8 and the second group of temperature measuring probes 9, namely the temperature values of all temperature measuring points, are recorded.

And drawing a temperature change curve of each position of the refractory brick according to each recorded temperature value, and evaluating the overall heat insulation performance of the refractory material according to the temperature change curve.

According to the invention, the temperature change curves of all points are obtained objectively and accurately by simulating the actual service condition of the refractory material in the kiln, the temperature condition of the refractory material used in the kiln is visually represented, the overall heat transfer performance of the refractory material is systematically and objectively evaluated, the accuracy of the heat conduction test of the refractory material is improved, and considerable economic benefits are created for refractory material enterprises, so that the method has important significance. And the temperature in the test device is controllable, safe and reliable, and the cost is lower. The furnace body can be built by refractory bricks with different sizes, is suitable for the refractory bricks of various homogeneous systems and heterogeneous systems, does not require isotropy and homogeneity of the refractory bricks, and enlarges the test range of the tested refractory materials. In the testing process, the temperature rise temperature and the temperature rise rate have no any limit on the result of the method, and the result is stable.

The invention is applicable to various forms of refractory brick, and several examples are given below for illustration:

example one:

the firebrick of this example is compound firebrick, and compound firebrick includes flame retardant coating, insulating layer and the heat preservation that sets gradually and integrated into one piece, and when building the furnace body, the flame retardant coating of compound firebrick is inside towards the stove outer covering.

For the composite refractory brick, the temperature measuring points are arranged on the refractory layer, the heat insulating layer and the heat insulating layer of the composite refractory brick, and temperature measuring holes for the first group of temperature measuring probes to be inserted are drilled at the temperature measuring points.

Example two:

the refractory brick of this example is a homogeneous refractory brick, which includes a heat insulating layer unit, and a flame retardant layer unit that are separated from each other, and when a furnace body is built, the heat insulating layer unit, and the flame retardant layer unit are sequentially disposed from outside to inside in a furnace shell.

For the homogeneous refractory brick, the temperature measuring points are arranged on the refractory layer unit, the thermal insulation layer unit and the thermal insulation layer unit of the homogeneous refractory brick, and temperature measuring holes for inserting the first group of temperature measuring probes are drilled at the temperature measuring points.

The second group of temperature measuring probes 9 can be adsorbed on the outer surface of the side wall of the furnace shell 1 through magnetic force, or an installation groove is formed in the outer surface of the side wall of the furnace shell 1, and the second group of temperature measuring probes 9 are arranged in the installation groove.

Aforementioned temperature measuring device can be patrolled and examined temperature measuring device for the multichannel is compound, and thermocouple and thermal resistance data end are patrolled and examined temperature measuring device with the multichannel is compound and are connected, and temperature measuring device can be surveyed to the multichannel is compound to patrol and examine temperature measuring device can multi-direction and multiple site.

Example 2:

an embodiment of the present invention provides a test method of the test apparatus for evaluating the overall heat insulation performance of a refractory material of embodiment 1, the method including:

s1: the furnace lid 2 is lifted by a crane.

S2: the firebricks are laid horizontally along the bottom wall of the furnace shell 1 and the refractory ends of the firebricks are made to face toward the inside of the furnace shell 1 (i.e., the refractory ends are vertically upward) and the firebricks are bonded with fire clay to obtain a first firebrick layer 3.

S3: on the first firebrick layer 3 that has been laid, firebricks are laid in an annular shape along the side wall of the furnace shell 1, and the firebricks are made to face the inside of the furnace shell 1 at their firebrick ends (i.e., the firebricks are horizontally faced toward the center), and the firebricks are bonded with fire clay, resulting in a second firebrick layer 4.

The first refractory brick layer 3 and the second refractory brick layer 4 enclose a cavity, and the upper end of the cavity is opened.

S4: the furnace cover 2 is hermetically covered on the opening at the upper end of the furnace shell 1 and is locked with the furnace shell, the heating device 7 extends into the cavity, and the first group of temperature measuring probes 8 are contacted with the temperature measuring points set on the refractory bricks in the furnace shell 1.

S5: setting the heating rate and the heating temperature, starting the heating device 7, starting the heating operation, and simultaneously starting the temperature measuring device.

S6: the temperature measuring device is used for measuring the temperatures of the first group of temperature measuring probes 8 and the second group of temperature measuring probes 9, and after the temperatures of the first group of temperature measuring probes 8 and the second group of temperature measuring probes 9 are stable (namely the heat transfer of the system reaches a stable state), the temperature measuring device records the temperature values of the first group of temperature measuring probes 8 and the second group of temperature measuring probes 9.

S7: and drawing a temperature change curve of each position of the refractory brick according to each recorded temperature value, and evaluating the overall heat insulation performance of the refractory material according to the temperature change curve.

For the composite refractory brick, the refractory brick is a heterogeneous system refractory brick, a refractory layer, a thermal insulation layer and a heat preservation layer are integrally formed, when a furnace body is built, the tested composite refractory brick refractory layer is vertically upwards faced into the furnace and is tiled at the bottom in a furnace shell, and the composite refractory brick is bonded by fire clay to obtain a first refractory brick layer; on the flame retardant coating on the first firebrick layer of laying, put along the stove outer covering inner wall and examine compound firebrick, the flame retardant coating is towards the stove in, and the heat preservation is towards the stove outer covering inner wall, with compound firebrick of fire clay bonding, obtains the second firebrick layer, the centre sets up the cavity.

The thermocouple contacts the tested refractory brick in the refractory layer, the heat insulating layer and the heat insulating layer of the composite refractory brick respectively, and the thermal resistor is adsorbed on the outer surface of the furnace shell through magnetic force.

The homogeneous refractory brick comprises a heat-insulating layer unit, a heat-insulating layer unit and a refractory layer unit which are mutually separated, and the homogeneous refractory brick is respectively applied to a refractory layer, a heat-insulating layer and a heat-insulating layer of a kiln. When a furnace body is built, the heat-insulating layer unit and the fire-resistant layer unit are sequentially paved at the bottom of the furnace shell from bottom to top, and the three kinds of fire brick units are bonded by fire clay to obtain a first fire brick layer; on the first refractory brick layer, heat insulating layer unit and refractory layer unit are built along the inner wall of furnace shell from outside to inside, and three refractory brick units are bonded by fire clay to obtain the second refractory brick layer with cavity in the middle.

The thermocouple contacts the tested refractory brick in the refractory layer unit, the heat insulating layer unit and the heat insulating layer unit of the composite refractory brick respectively, and the thermal resistor is adsorbed on the outer surface of the furnace shell through magnetic force.

The method of the embodiment of the present invention is a method for using the test apparatus for evaluating the overall heat insulation performance of the refractory material described in embodiment 1, and includes all the technical solutions of embodiment 1, and has the beneficial effects described in embodiment 1, which are not described herein again. Other parts of this embodiment not mentioned above can be referred to the corresponding parts in the foregoing embodiment 1.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.