Column oven and gas chromatograph

Abstract

To improve cooling efficiency of an inner space of a column oven while ensuring the heat insulation of the inner space.SOLUTION: A column oven (2) includes: an inner casing (10) forming inside an inner space (11) for accommodating a separation column (4) for gas chromatography and adjusting a temperature of the separation column (4); a temperature control element (12) provided in the inner space (11) for controlling a temperature of the inner space (11); and a heat insulation material layer (14) made of a fibrous material surrounding an outer peripheral surface of the inner casing (10). The heat insulation material layer (14) includes: a first layer (18) having a first bulk density (ρ1); and a second layer (20) surrounding the outside of the first layer (18) and having a second bulk density (ρ2) lower than the first bulk density (ρ1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a column oven and a gas chromatograph equipped with the column oven. [Background technology]

[0002] In gas chromatographs, a separation column for separating components in a sample gas is generally housed in a column oven, and the temperature of the separation column is controlled to a set temperature by raising and lowering the temperature inside the column oven. The column oven has a structure in which the internal space housing the separation column is surrounded by a heat insulating material, thermally insulating the internal space from the outside (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-162972 Summary of the Invention [Problem to be solved by the invention]

[0004] To control the temperature inside a column oven with high precision, it is important to improve the insulation of the column oven's internal space. Generally, the insulation performance improves as the volume of the insulation material increases. Therefore, increasing the volume of the insulation material surrounding the internal space of the column oven can improve the insulation of the internal space, but this increases the heat capacity of the insulation material, which increases the time required for the insulation material to cool naturally when you want to lower the temperature inside the column oven.

[0005] The present invention has been made in view of the above problems, and has as its object to improve the cooling efficiency of the internal space of a column oven while ensuring the thermal insulation of the internal space. [Means for solving the problem]

[0006] The thermal conductivity λ [W / (m·K)] of a thermal insulation material can be approximated by the thermal conductivity of a solid, the thermal conductivity contributed by radiation, and the thermal conductivity of a gas (see Takahiro Omura et al., Kyushu University Institute of Functional Materials Research Report, Vol. 16, pp. 13-17, 2002, Study on the Effective Thermal Conductivity of Fibrous Thermal Insulation Materials). In other words, the thermal conductivity λ of a thermal insulation material can be expressed by the following equation (1). λ=Aρ+(B / ρ)T 3 +C (1) where A, B, and C are coefficients determined from experiments, and ρ is the bulk density of the insulation material [kg / m 3 ], and T is the absolute temperature [K]. The first term on the right side of the equation is the thermal conductivity of the solid, the second term is the thermal conductivity contributed by radiation, and the third term is the thermal conductivity of the gas. From the above equation (1), we can see that in high temperature ranges (for example, above 300°C), the contribution of thermal conduction due to radiation is large, and the higher the bulk density of the insulation material, the smaller the thermal conductivity due to radiation. In other words, the higher the bulk density of the insulation material, the higher the insulation performance in high temperature ranges. Conversely, in low temperature ranges, the contribution of bulk density ρ to thermal conductivity becomes larger.

[0007] Furthermore, the amount of heat Q [J] accumulated in an object can be expressed by the following equation (2) according to the law of conservation of heat. Q=ρVcΔT (2) V is the volume of the insulation [m 3 ], and c is the specific heat [J / kg·K]. From this equation (2), when comparing insulation materials of the same volume, it can be seen that the lower the bulk density of the insulation material, the smaller the amount of heat that can be stored, i.e., the smaller the heat capacity.

[0008] The present invention utilizes the above-mentioned features to improve the thermal insulation performance and cooling efficiency inside a column oven. That is, the column oven according to the present invention comprises an inner casing that forms an internal space for accommodating a separation column for gas chromatography and for regulating the temperature of the separation column, a temperature control element that is provided in the internal space and for regulating the temperature of the internal space, and an insulating layer made of a fibrous material that surrounds the outer surface of the inner casing, wherein the insulating layer includes a first layer having a first bulk density and a second layer that surrounds the outside of the first layer and has a second bulk density lower than the first bulk density.

[0009] The gas chromatograph of the present invention comprises a sample vaporization unit having a sample injection port and vaporizing a sample injected from the sample injection port to produce a sample gas; a separation column having an inlet and an outlet, the inlet fluidly connected to the sample vaporization unit, for separating components in the sample gas produced in the sample vaporization unit; a detector connected to the outlet of the separation column and for detecting the components separated from each other in the separation column; and a column oven of the present invention having an internal space to accommodate the separation column and adjust the temperature of the separation column. [Effects of the Invention]

[0010] In the column oven according to the present invention, a first layer having a high bulk density (first bulk density) effectively blocks heat radiated from the inner casing in the high-temperature region near the inner casing, while a second layer having a low bulk density (second bulk density) is disposed in the relatively low-temperature region outside the first layer, thereby ensuring the volume of the insulation layer, ensuring high insulation performance, and suppressing an increase in heat capacity. This makes it possible to improve the cooling efficiency of the internal space of the column oven while ensuring insulation of the internal space.

[0011] The gas chromatograph according to the present invention uses the column oven according to the present invention described above, and therefore the time required for increasing and decreasing the temperature of the separation column is shortened, thereby improving analytical efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing an embodiment of a gas chromatograph. [Figure 2] FIG. 2 is a cross-sectional view illustrating the structure of the heat insulating layer of the column oven of the same embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of a column oven and a gas chromatograph according to the present invention will be described with reference to the drawings.

[0014] FIG. 1 shows a schematic structure of a gas chromatograph 1.

[0015] The gas chromatograph 1 includes a column oven 2, a separation column 4, a sample vaporizer 6, and a detector 8. The separation column 4 is housed in an internal space 11 of the column oven 2. The internal space 11 of the column oven 2 is provided with a temperature control element 12 for controlling the temperature of the internal space 11. The temperature control element 12 includes, for example, a heater, a Peltier element, a fan, etc.

[0016] The sample vaporizer 6 and detector 8 are attached to the top of the column oven 2. The separation column 4 has an inlet at one end and an outlet at the other end, with the inlet connected to the sample vaporizer 6 and the outlet connected to the detector 8. The sample vaporizer 6 has a sample injection port 7 at its top and is used to vaporize the sample injected through the sample injection port 7 to generate sample gas. The sample gas generated in the sample vaporizer 6 is introduced into the separation column 4, where the components in the sample gas are separated from each other. The detector 8 detects the components separated from each other in the separation column 4.

[0017] The column oven 2 comprises an inner casing 10 that defines an internal space 11 therein, an insulating layer 14 that surrounds the outer periphery of the inner casing 10, and an outer casing 16 that surrounds the outer side of the insulating layer 14. That is, the wall surface of the column oven 2 is composed of, from the inside, the inner casing 10, the insulating layer 14, and the outer casing 16 (see FIG. 2). The wall surface of the ceiling of the column oven 2 has through-holes for passing the sample vaporizer 6 and the detector 8 through, and the sample vaporizer 6 and the detector 8 are fixed to the outer casing 16 while passing through the ceiling of the column oven 2.

[0018] The insulation layer 14 interposed between the inner casing 10 and the outer casing 16 of the column oven 2 is made of a fibrous material such as glass wool or rock wool. The insulation layer 14 includes a first layer 18 and a second layer 20. The first layer 18 covers the outer peripheral surface of the inner casing 10, and the second layer 20 covers the outer peripheral surface of the first layer 18.

[0019] A cross section of the inside wall of the column oven 2 is shown in FIG.

[0020] The first layer 18 of the thermal insulation layer 14 is located in a region close to the inner casing 10. This region is a region that reaches a high temperature when the temperature of the separation column 4 is raised to a high temperature (for example, 300°C or higher). On the other hand, the second layer 20 of the thermal insulation layer 14 is located in a region away from the inner casing 10. By interposing the first layer 18 between this region and the inner casing 10, this region is a region that is lower in temperature than the region where the first layer 18 is located.

[0021] The first layer 18 and the second layer 20 have different bulk densities ρ1 and ρ2. The bulk density ρ1 of the first layer 18 is higher than the bulk density ρ2 of the second layer 20. For example, the bulk density ρ1 of the first layer is at least twice the bulk density ρ2 of the second layer 20. Furthermore, the thickness L2 of the second layer 20 is greater than the thickness L1 of the first layer. For example, the thickness L2 of the second layer 20 is at least twice the thickness L1 of the first layer.

[0022] As mentioned above, in high temperature ranges (e.g., 300°C or higher), the contribution of heat conduction by radiation is large, and the higher the bulk density of the insulation material, the lower the thermal conductivity by radiation. Therefore, if the only goal is to improve the insulation performance of the internal space 11, it is sufficient to cover the outer surface of the inner casing 10 with a thick insulation layer having a high bulk density, that is, to form the insulation layer 14 only with the first layer 18 having a high bulk density. However, this increases the heat capacity of the insulation layer 14, and it takes a long time to cool the internal space 11.

[0023] In this embodiment, a first layer 18 with a high bulk density ρ1 is placed only in the high-temperature region, and a second layer 20 with a relatively low bulk density ρ2 is placed in the relatively low-temperature region outside of it. In low-temperature regions, the contribution of heat conduction by radiation is smaller than in high-temperature regions. Therefore, even if the bulk density ρ2 of the insulation layer (second layer 20) placed in the low-temperature region is lower than the bulk density ρ1 of the insulation layer (first layer 18) placed in the high-temperature region, sufficient insulation can be achieved by ensuring a certain thickness L2 of the second layer 20 (e.g., more than twice L1). Furthermore, because the second layer 20 has a low thermal capacity due to its low bulk density ρ2, the overall thermal capacity of the insulation layer 14 can be reduced. In particular, by designing the second layer 20 to occupy a large portion of the volume of the insulation layer 14 (e.g., more than 60%), an insulation layer 14 with high insulation performance and low thermal capacity can be achieved.

[0024] The heat insulating layer 14 does not necessarily need to completely cover the outer peripheral surface of the inner casing 10, and part of the outer peripheral surface of the inner casing 10 may not be covered by the heat insulating layer 14. Furthermore, cloth, foil, etc. may be interposed between the outer peripheral surface of the inner casing 10 and the first layer 18, between the first layer 18 and the second layer 20, and between the second layer 20 and the outer casing 16.

[0025] The above-described embodiment is merely one example of the column oven and gas chromatograph according to the present invention. One embodiment of the column oven and gas chromatograph according to the present invention is as follows.

[0026] One embodiment of the column oven of the present invention comprises an inner casing that forms an internal space for accommodating a separation column for gas chromatography and regulating the temperature of the separation column, a temperature control element provided in the internal space for regulating the temperature of the internal space, and an insulating layer made of a fibrous material that surrounds the outer surface of the inner casing, wherein the insulating layer includes a first layer having a first bulk density and a second layer that surrounds the outside of the first layer and has a second bulk density lower than the first bulk density.

[0027] In the above embodiment, the second layer of the thermal insulation layer may be thicker than the first layer. Because the second layer is disposed in a region with a lower temperature than the first layer, a sufficient thermal insulation effect can be obtained by ensuring a certain thickness of the second layer. Although the volume of the entire thermal insulation layer increases by increasing the thickness of the second layer, the bulk density of the second layer is lower than the bulk density of the first layer, so that an increase in the heat capacity of the entire thermal insulation layer can be suppressed, thereby shortening the time required to cool the internal space of the column oven.

[0028] One embodiment of a gas chromatograph according to the present invention comprises: a sample vaporization unit having a sample injection port and vaporizing a sample injected from the sample injection port to produce a sample gas; a separation column having an inlet and an outlet, the inlet fluidly connected to the sample vaporization unit, for separating components in the sample gas produced in the sample vaporization unit; a detector connected to the outlet of the separation column and for detecting the components separated from each other in the separation column; and the above-mentioned column oven having an internal space to accommodate the separation column and adjust the temperature of the separation column. [Explanation of symbols]

[0029] 1. Gas chromatograph 2 Column Oven 4 Separation column 6. Sample vaporization section 8 Detectors 10 Inner casing 12 Temperature control element 14 Insulation layer 16 outer casing 18 First Layer 20 Second Layer

Claims

1. An inner casing that accommodates a separation column for gas chromatography and forms an internal space therein for adjusting the temperature of the separation column; A temperature control element provided in the internal space for adjusting the temperature of the internal space; a heat insulating layer made of a fibrous material surrounding the outer peripheral surface of the inner casing, A column oven, wherein the insulation layer includes a first layer having a first bulk density and a second layer surrounding the outside of the first layer and having a second bulk density lower than the first bulk density.

2. 10. The column oven of claim 1, wherein the second layer of the insulation layer is thicker than the first layer.

3. a sample vaporization unit having a sample injection port and vaporizing a sample injected through the sample injection port to generate a sample gas; a separation column having an inlet and an outlet, the inlet fluidly connected to the sample vaporization section, for separating components in the sample gas produced in the sample vaporization section from each other; a detector connected to the outlet of the separation column for detecting components separated from each other by the separation column; 3. A gas chromatograph comprising: the column oven according to claim 1 or 2, which has an internal space for accommodating the separation column and for adjusting the temperature of the separation column.

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