JP2001017851A - Heater for producing supercritical fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a supercritical fluid with its temperature and density stabilized by small-sized constitution and to obtain a high temperature of a specified temperature or above simply by forming a heater from a structure in which a liquid heating pipe is wound spirally onto the peripheral surface of a metal block in the shape of a cylinder, etc., and a heating means arranged on the peripheral surface. SOLUTION: In a fluid heating pipe 1, a raw material liquid introduction port I is opened at one end, and a supercritical fluid extraction opening O is opened at the other end. a U-shaped groove 12 is formed spirally on each outside of cylindrical metal blocks 2, 3, which are a metal heat conductive medium, on the inner and outer sides, and the pipe I is embedded in the shape of a double spiral in the groove 12. A columnar metal block 4 is arranged on the inside of the inside block 3, and the pipe I is inserted in a through hole formed on the central axis of the block 4 in a straight line shape. A Ni-Cr wire 9 wrapped in an insulating body 8 is wound spirally onto the periphery of a metal cylindrical body 7, a metal radiation heat reflection plate 10 is wound on the periphery of these to do enclosure with an insulating material 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a supercritical fluid (SC)
F) A heating device for producing a supercritical fluid for use in processing or supercritical fluid reaction.

[0002]

2. Description of the Related Art Continuous generation of supercritical fluid used on industrial scale and research scale for various applications such as supercritical fluid chromatography, supercritical fluid reaction, supercritical fluid environmental pollutant treatment, and supercritical fluid cleaning. In order to make the liquid flow at a certain pressure, the liquid needs to be heated to a high temperature by a heating device.

[0003] As a method of heating a liquid, usually, a gas (for example, a furnace) or a constant temperature bath incorporating a heat source is used.
A method of transferring heat to a liquid using an air or a rare gas) or a liquid (for example, a molten salt) as a heat transfer medium has been used.

For example, as for an apparatus for epimerizing and decomposing glucose with supercritical water, an apparatus is known in which pressurized water is preheated in a preheating section directly wound with a sheath heater, and heated in a reaction section using a thermostatic bath using a molten salt ( In
d. Eng. Chem. Res., Vol. 36, No. 5, 1997, pp. 1552-1558).

[0005] Among supercritical fluids, supercritical water is considered to be used for various purposes such as industrial production and environmental pollutant treatment by companies and public facilities, and requires large-scale facilities. In addition, there is a demand for an apparatus that can easily realize a continuous supercritical flow and can be used for small-scale experiments and medium-scale production.

[0006]

In the supercritical state, which is neither a liquid nor a gas, the density changes greatly when the temperature changes even slightly. When the density changes, the branching ratio of the chemical reaction occurring there changes or does not proceed. Therefore, in order to keep the reaction conditions constant, it is very important to stabilize the temperature. Only when a supercritical fluid having a stable density is obtained can a desired chemical reaction or a desired substance be extracted selectively.

However, in the heating using a conventional thermostat,
The heating element is immersed in the heat transfer medium, and the generated heat is transmitted while generating a temperature gradient in the heating medium regardless of whether the heating element is cylindrical or flat, so that the temperature gradient is reduced. There is a need for stirring. Even with stirring, the thermal conductivity of molten salts and air is very small compared to metals, so the heat exchange efficiency between the heating element and heat transfer medium and between the heat transfer medium and It is considerably inferior to the transmission medium. Further, there is a tendency that the volume of the heat transfer medium is increased in order to increase the heat capacity to increase the size of the apparatus, which causes not only inconvenience in handling but also problems in safety and economy.

[0008]

Means for Solving the Problems The present inventors have obtained a supercritical fluid having a stable temperature and density with a small-sized apparatus, and can use a supercritical water which can be used in the most critical supercritical water.
As a result of research and development aimed at an apparatus that can easily obtain a high temperature of ℃ or higher, the present invention was completed.

That is, the present invention relates to a heating device for flowing a raw material liquid into a liquid heating tube formed of a metal tube and heating the raw material liquid from outside the liquid heating tube to generate a supercritical fluid. A liquid heating tube is formed on the outer peripheral surface of a cylindrical metal block or a cylindrical metal block, which is a metal heat transfer medium, continuously from one end in the longitudinal direction to the other end thereof along a spiral groove from the other end. A helical liquid that is wound around an end and has a structure in which the end portion of the liquid heating tube connected to the supercritical fluid outlet is straight and passes through the inside of a hole provided in the central axis of the cylindrical metal block or the cylindrical metal block. A heating device for generating a supercritical fluid, comprising a heating pipe structure and a heating means provided on an outer peripheral surface thereof.

In the heating apparatus for generating a supercritical fluid of the present invention, the outer peripheral surface of the helical liquid heating pipe structure is formed on the inner peripheral surface of a metal cylinder having good thermal conductivity provided with uniform heating means on the outer peripheral surface. Preferably, they are arranged so as to be in contact. In addition, the spiral liquid heating tube structure has another cylindrical metal block or columnar metal block placed inside the cylindrical metal block, and the liquid heating tubes are continuously spirally arranged on the outer peripheral surface of each block. It is preferably wound around. Preferably, metal heat guards are mounted at both ends of the cylindrical or cylindrical metal block to prevent uneven heating of the fluid heating tube due to a temperature gradient at both ends in the axial direction. Heating means is provided outside the metal cylinder having good thermal conductivity,
Preferably, it is a heating wire continuously spirally wound from one end to the other in the longitudinal direction of the metal cylinder. In the heating device of the present invention, the temperature of the supercritical fluid inside the linear liquid heating tube is measured by a thermocouple arranged along the linear liquid heating tube at the end portion connected to the supercritical fluid outlet. To control the temperature of the heating device.

In the heating apparatus for generating a supercritical fluid of the present invention, heat generated by a uniform heating means such as a heating wire is transmitted to a metal cylinder having good heat conductivity and is in contact with the metal cylinder. It is transferred to the heat transfer medium. As the heat transfer medium, a solid metal having a large thermal conductivity, for example, a copper alloy which is hardly oxidized even at 500 ° C. or more and has a relatively large thermal conductivity,
For example, using brass as a metal block, the outer peripheral surface of a metal tube, which is a liquid heating tube through which a raw material liquid flows, is brought into contact with the metal block.

[0012] The end portion of the liquid heating tube leading to the supercritical fluid outlet is straight, passes through the inside of a hole provided at the center axis of the cylindrical metal block or the cylindrical metal block, and passes through the metal block. Since the inner surface of the hole is in surface contact with the outer surface of the liquid heating tube, the heat transmitted through the metal block is uniformly transmitted from the 360-degree direction to the linear liquid heating tube having the central axis.

In the apparatus according to the present invention, the heating element as the heating means is arranged cylindrically symmetrically with respect to the axis, and the fluid heating tube receives heat from the 360-degree direction via the heat transfer medium. Regarding the temperature distribution inside the heating device, the temperature gradient in the radial direction with respect to the central axis of the heating device is very small, and it can be considered that the temperature is almost uniform in a steady state.

As described above, the temperature inside the heating device having the axisymmetric structure is stable, and the temperature of the fluid flowing along the central axis along the central axis is very reliable. By measuring and controlling the temperature of the finally obtained supercritical fluid in the vicinity of the central axis, a supercritical fluid having a desired and accurate density can be reliably obtained.

The apparatus of the present invention has a feature that it is compact and easy to use as compared with a conventional apparatus that requires a long time to prepare and finish a reaction using a large-scale heating apparatus. A high-temperature, high-pressure reaction that generates a supercritical fluid of various substances can be carried out efficiently, easily, and safely as easily as a normal room-temperature reaction. In addition, by flowing an aqueous solution containing a reactant through the inside of the spiral liquid heating tube, a chemical reaction can be advanced while leading to a supercritical fluid state.

Therefore, for example, an operation of conducting various reactions under various conditions to search for convenient conditions can be easily performed, and as one step in continuously performing an organic synthesis reaction, the reaction is carried out in the middle of the reaction. It is also possible to insert a supercritical water reaction. In addition, for the reaction in water, subcritical water (200 to
There is a reaction in 350 ° C) and a reaction in supercritical water (374 ° C or higher).
By using the apparatus of the present invention as a reactor and arranging two sets in series and controlling the temperature of each, it is also possible to carry out the reaction while controlling the two temperature regions by a program, and it is possible to control a chemical reaction which could not be performed conventionally.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the heating apparatus for generating a supercritical fluid according to the present invention will be described below in detail with reference to the drawings. FIG. 1 shows that the device according to the invention is approximately 120 ° relative to the central axis.
It is a longitudinal section perspective view cut and shown at an angle of degree. FIG.
FIG. 2 is a sectional view taken along the center line of FIG. 1.

The liquid heating tube 1 is provided with a pressure pump (not shown)
Is provided at one end (the upper part in the figure) and a supercritical fluid outlet O at the other end (the lower part in the figure). The liquid is pressurized at room temperature using a commercially available pump and led to the heating device of the present invention. FIG. 1 shows an example in which the central axis of the device of the present invention is vertically arranged. However, the present invention is not limited to the vertical arrangement, and it is also possible to freely arrange the device in the horizontal direction or any other angle direction. There are two features.

The material of the liquid heating tube 1 is SUS31
6. Materials satisfying chemical and mechanical properties such as high temperature oxidation resistance, high temperature corrosion resistance, high temperature strength, and high temperature creep strength such as stainless steel tubes such as SUS304 and Ni-based heat-resistant alloy (Hastelloy, Inconel (registered trademark)) tubes. use. The outer diameter of the liquid heating tube 1 is considered to be 1/16 to 1/8 inch suitable for a small to medium scale apparatus, but may be 1/4 inch or more on an industrial scale and is not particularly limited. The inner diameter of the liquid heating tube 1 is appropriately determined depending on the type of material and the pressure and temperature for generating a supercritical fluid.

The outermost cylindrical metal block 2 used as a metal heat transfer medium having good heat conductivity, and the outer peripheral surface of the inner cylindrical metal block 3 are arranged from one end in the longitudinal direction to the other end in FIG. As shown, a u-shaped groove 12 is formed by a machine tool (for example, a lathe) in a spiral shape such that the liquid heating tube 1 is just buried. Next, a metal tube serving as the liquid heating tube 1 is wound from one end to the other end using a metal processing device while being embedded along the spiral u-shaped groove 12. By doing so, the liquid heating tube 1 is provided with the u-shaped grooves 12 provided in the cylindrical metal blocks 2 and 3 having good heat conductivity.
In direct surface contact with the sides and bottom of the Also,
The side opposite to the bottom of the groove is in line contact with the surface of the metal cylinder 7 having good thermal conductivity. Preferably, the gap between the fluid heating tube 1 and the u-shaped groove 12 is filled with high melting point silver wax or the like so that there is no gap, so that the contact between the liquid heating tube and the metal heat transfer medium is improved, and the heat exchange efficiency is improved. Can be enhanced.

In the embodiment shown in FIG. 1 and FIG. 2, the liquid heating tube 1 is spirally continued from the lower part of the spirally wound outer spiral tube to the outer peripheral surface of the inner cylindrical metal block 3. It is wound and has a double spiral tube structure,
The object of the present invention can be sufficiently achieved with only the outer spiral tube. Further, a multiple tube structure such as a triple spiral tube structure or a quadruple spiral tube structure may be used.

When the liquid heating tube 1 is a double spiral tube, a u-shaped groove 12 for embedding the outer spiral tube in the outer peripheral surface of the outer cylindrical metal block 2 is cut into a spiral shape. A spiral tube is embedded. Similarly, a u-shaped groove 12 for embedding the internal spiral tube on the outer peripheral surface of the inner cylindrical metal block 3 serving as a metal heat transfer medium is spirally cut, and the internal spiral tube is embedded in this groove. . The entire length of the inner cylindrical metal block 3 is slightly shorter than the entire length of the outer cylindrical metal block 2, and is located at the center, and disk-shaped metal heat guards 5 are loaded at both ends. It is preferable to protect the influence of heat radiation at both ends due to the temperature gradient in the axial direction by the metal heat guard 5 and to achieve uniform heating of the fluid heating tube passing near both ends.

Inside the inner cylindrical metal block 3,
A cylindrical metal block 4 serving as a metal heat transfer medium is provided, and a through hole is provided on the central axis of the block 4 so that the end portion of the liquid heating tube 1 connected to the supercritical fluid outlet is linearly passed. The tube 1 is inserted straight from the upper side to the lower side as shown. When the helical tube is a single helical tube only on the outside, a cylindrical metal block is used, and a through hole is provided in the center axis of the helical tube. And insert it.

Further, along the straight portion of the liquid heating tube 1, a hole for inserting the thermocouple 6 to a substantially central portion is opened.
A thermocouple 6 for temperature measurement connected to a pyrometer (not shown) is inserted.

As the material of the cylindrical or cylindrical metal block and the metal heat guard serving as the metal heat transfer medium, brass, beryllium copper, phosphor bronze, aluminum bronze and the like are preferable. Room temperature to 600 ° C
Up to then, brass is the best. Copper is 400-500
It is not suitable for high temperature use because it oxidizes easily when used at ° C.

A spiral heating tube structure having the above-described structure is attached to the inner peripheral surface of a metal cylinder 7 having good thermal conductivity made of a copper alloy plate such as brass and provided with uniform heating means on the outer peripheral surface. The helical liquid heating tube structure is arranged so that the outer peripheral surfaces thereof come into contact with each other.

An insulator 8 such as a mica plate or cloth-like asbestos is wrapped around the outer periphery of the metal cylinder 7, and a nichrome wire 9 as a heating wire for the heater is placed on the insulator 8 so as not to bend and as dense as possible. Metal cylinder 7 from one end without unevenness
Spirally around the entire circumference. After the winding is completed, both ends of the nichrome wire 9 are fixed so as not to be loosened, and the insulator 8 is wound again from above. Both ends of the nichrome wire 9 are connected to a heating power supply (not shown). In FIG. 1, the insulator 8 that insulates the nichrome wire 9 shows a cut surface at a slightly receded surface, and the nichrome wire 9 is drawn so as to protrude from the insulator 8. Furthermore, a radiant heat reflecting plate 10 made of a metal such as nickel is preferably wound around the outside of the layer composed of the insulator 8 surrounding the nichrome wire 9 to increase the heating efficiency. Sufficiently surround.

The liquid heating tube 1 is wound as concentrically as possible with respect to a heater composed of a spirally wound nichrome wire 9. In the case of a multiple spiral tube, the outer spiral tube and the inner spiral tube are wound so as not to come into direct contact with each other.
It is desirable to arrange them via the above-described metal heat transfer medium. Although a specific example in which a heating wire is helically wound as a heater is shown, any method that can achieve uniform heating, such as a method such as winding in the vertical direction in the example shown in FIG. Can be used.

The apparatus of the present invention is a supercritical fluid generating apparatus, and can also perform a chemical reaction in the generated supercritical fluid if a reactant is previously mixed with a liquid. The apparatus of the present invention is applicable to various liquids, and the supercritical conditions of these various liquid substances are shown in Table 1.

[0030]

[Table 1]

The maximum heating temperature differs depending on the type of the substance to be made supercritical, the type of the material of the metal heat transfer medium, and the type of the material of the liquid heating tube. Considering the use of the most severe condition for supercritical water, the maximum usable temperature of the device is 600 ° C.
Although required, the heating device of the present invention sufficiently satisfies such high-temperature heating requirements.

FIG. 4 shows an example in which the apparatus of the present invention is used as a supercritical fluid reactor. When used as a supercritical fluid reactor, water + reactant 1 is pressurized by a pressurizing device 2 and heated by a heating device 3 of the present invention controlled by a back pressure control valve 4 to generate supercritical water. Then, a predetermined reaction proceeds. The reaction product is separated in the separation device 5. FIG. 5 shows an example in which the device of the present invention is used as a supercritical fluid generating device. When used as a supercritical fluid generator, the water 6 and the reactant 7 are each pressurized by the pressurizing device 2, and the water 6 is heated by the heating device 3 of the present invention, and the reactant 7 is heated.
Is preheated by using the heating device 3 of the present invention as the preheating device 8 and guided to the reaction tanks 9 controlled by the back pressure control valve 4 to react water and reactants. The reaction product is separated in the separation device 5.

Embodiment In the heating apparatus of the present invention shown in FIGS. 1 and 2, the inner diameter of the brass plate metal cylinder 7 is 40 mmφ, the total length is 130 mm,
The outer diameter of the cylindrical metal block 2 is 40 mmφ and the inner diameter is 30
SUS316, the overall length of the cylindrical metal block 3 was 30 mmφ, the overall length was 100 mm, and the outer diameter of the entire apparatus including the layer of the heat insulating material 11 was 70 mmφ.
A stainless steel pipe was wound as a liquid heating pipe 1 with a length of about 7 m at a pitch of 3 mm, and a nichrome wire 9 was wound 2.5 mm.
A device wound at a pitch of 1 mm was used.

Approximately 50 with a high-pressure liquid pump (manufactured by JASCO)
After the water pressurized to 0 kgf / cm ² is injected into the liquid heating tube 1 from the raw material liquid inlet I shown in FIGS. 1 and 2, the heater composed of the nichrome wire 9 is energized while maintaining a constant pressure. did. Heat until the temperature at the center of the device measured by the thermocouple 6 shown reaches the maximum temperature of 500 ° C.
Supercritical water at 500 ° C. and 500 kgf / cm ² was realized.

The condition of the critical point of water is 220 kgf / c
Since m ^{2 is} 374 ° C., the supercritical state is reliably realized. Thereafter, while supercritical water was discharged from the supercritical fluid outlet port O (at a pressure of 355 to 295 kgf / cm ² for about 40 minutes), the temperature was measured at the point A in FIG. 1 and the thermocouple 6. The temperature was stable and no fluctuation was observed. This means that the supercritical fluid taken out along the central axis can obtain a stable temperature and density, and the heating device of the present invention converts water at room temperature to a supercritical state of about 420 ° C. It has sufficient performance to generate supercritical water with stable temperature and density even if it flows continuously under the following conditions.

[0036]

The apparatus of the present invention has the following excellent effects as shown in 1 to 7. 1. By arranging the liquid heating tubes in the heating device concentrically around the same axis in a helical structure, preferably a multiple helical structure, the long liquid heating tubes can be made very small. 2. Unnecessary heat release is small due to miniaturization, and energy loss is suppressed as much as possible. 3. Metals have a thermal conductivity approximately three to four orders of magnitude higher than gas (air) and can be miniaturized when used as a heat transfer medium, so they are stable without stirring the heat transfer medium like gas. A temperature distribution is obtained. 4. Since metal is used for the heat transfer medium, the generation of steam in the heat transfer medium is extremely small even at high temperatures, and it is safe for the human body and the environment. 5. Since the heating element is wound close to the outer periphery of the metal heat transfer medium composed of a cylindrical block or a columnar block, the temperature gradient in the heating device is reduced. 6. The temperature of the supercritical fluid in the liquid heating tube along the central axis of the heating device is stable. Control and proceed. 7. The outer surface of the liquid heating tube has no corrosion problems because it is not in contact with a corrosive heat transfer medium.

[Brief description of the drawings]

FIG. 1 shows the device according to the invention at about 1
It is a longitudinal section perspective view cut and shown by an angle of 20 degrees.

FIG. 2 is a sectional view taken along the center line of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a portion X in FIG. 2;

FIG. 4 is a block diagram of an example in which the device of the present invention is used as a supercritical fluid reactor.

FIG. 5 is a block diagram of an example in which the device of the present invention is used as a supercritical fluid generating device.

Claims (6)

[Claims] 1. A heating device for flowing a raw material liquid into a liquid heating tube made of a metal tube and heating the raw material liquid from outside the liquid heating tube to generate a supercritical fluid, wherein the liquid heating tube is Winding from one end to the other along a spiral groove formed continuously from one end to the other end in the longitudinal direction on the outer peripheral surface of a cylindrical metal block or a cylindrical metal block as a metal heat transfer medium, A helical liquid heating tube structure having a structure in which the end portion of the liquid heating tube connected to the supercritical fluid outlet is straight and passes through the inside of a hole provided at the center axis of the cylindrical metal block or the cylindrical metal block. And a heating means provided on an outer peripheral surface of the heating device. 2. A helical liquid heating pipe structure which is arranged so that the outer peripheral surface of the helical liquid heating pipe structure comes into contact with the inner peripheral surface of a metal cylinder having good thermal conductivity provided with uniform heating means on the outer peripheral surface. The heating device for producing a supercritical fluid according to claim 1, wherein 3. The helical liquid heating pipe structure is such that another cylindrical metal block or a columnar metal block is disposed inside a cylindrical metal block, and a liquid heating pipe is continuously formed on the outer peripheral surface of each of the liquid heating pipes. 3. The heating device for generating a supercritical fluid according to claim 1, wherein the heating device is wound in a multiple structure. 4. The heating apparatus for generating a supercritical fluid according to claim 1, wherein metal heat guards are mounted on both ends of the cylindrical metal block or the cylindrical metal block. 5. The heating means is a heating wire continuously spirally wound from one end to the other end in the longitudinal direction of a metal cylinder having good heat conductivity. The heating device for generating a supercritical fluid according to claim 1. 6. A heating device which measures the temperature of a supercritical fluid inside a linear liquid heating tube by means of a thermocouple arranged along a linear liquid heating tube at a terminal portion connected to a supercritical fluid outlet. The heating device for producing a supercritical fluid according to any one of claims 1 to 5, wherein the temperature of the heating device is controlled.