JP2003206122A - Method for producing dry ice and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing dry ice capable of realizing a remarkably increased yield and an extremely excellent productive effect, and to provide an apparatus therefor. <P>SOLUTION: In the method for producing dry ice, a liquefied carbon dioxide gas is supercooled from a point to be crossed with a saturated liquid line under the feed pressure of about 2.0 Mpa at about -20°C to a point to be crossed with a triple point in an isobaric state, and is adiabatically expanded to 0.1 Mpa (atomic pressure). The apparatus for producing the dry ice is provided with a heat exchanger of supercooling the liquefied carbon dioxide gas, and a means of adiabatically expanding the liquefied carbon dioxide gas passed through the heat exchanger to 0.1 Mpa (atomic pressure). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new dry ice manufacturing method and apparatus, and more particularly, to a dry ice manufacturing method capable of largely eliminating yield waste and greatly improving production efficiency. Regarding the device.

[0002]

2. Description of the Related Art Dry ice, which is a solid carbon dioxide gas, has the property of sublimating in the atmosphere at -78.5 ° C, and is used as a coolant because it can obtain a low temperature without wetting the surroundings. In the room, ether and methyl alcohol
It is used as a cooling body that is crushed and put into a chilled container at a temperature of about -80 ° C, and it is also used as a prop for expressing clouds and fog on the stage of a theater.

This dry ice is usually manufactured by the steps described below. That is, the liquefied carbon dioxide gas is jetted from a jet nozzle (snow gun) connected to the liquefied carbon dioxide cylinder by a tube into a box-shaped integrated container having an upper surface opening. The liquefied carbon dioxide gas is adiabatically vaporized by this injection (adiabatic expansion), but at that time, it is cooled by latent heat and partly becomes snow-like powder (dry ice snow). A small amount of liquefied carbon dioxide is usually added to the snow-like powder, and the snow-like powder is compressed and solidified by a hydraulic piston to obtain dry ice.

In the above-mentioned work, the supply pressure of liquefied carbon dioxide is 2.0 MPa, the temperature is -20 ° C., and the point A in the enthalpy diagram of carbon dioxide shown in FIG.
In such a state, it is executed at a point intersecting the saturated liquid line. In this figure, point A indicates adiabatic expansion to 0.1 Mpa (atmospheric pressure), and the point intersecting 0.1 Mpa is B. Point B is the point where snow-like powder is obtained. In this enthalpy diagram, X indicates the dryness at a pressure and temperature below the triple point, and X = 0.6 indicates that gas is 60% and solid is 40%.

[0005]

However, in the conventional method for producing dry ice, the dryness is 55% even under the pressure and temperature which are considered to be efficient, that is, the gas of carbon dioxide gas. 55%, dry ice snow
The yield is at most 45%, and when the above-mentioned pressure and temperature are removed, the yield is further reduced to about 20 to 30% of the liquefied carbon dioxide gas supplied, resulting in extremely poor production efficiency. There is.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention is based on the conventional situation described above.
The purpose of the present invention is to provide a method and an apparatus for producing dry ice, in which the problems are solved, the yield is significantly increased, and the production effect is extremely excellent. .

[0007]

In order to achieve this object, in the method for producing dry ice according to the present invention, liquefied carbon dioxide gas intersects a saturated liquid line at a supply pressure of about 2.0 MPa and a temperature of about -20 ° C. From the point, the liquefied carbon dioxide gas is subcooled to a point intersecting the triple point in an isobaric state, and in that state, adiabatic expansion is performed to 0.1 Mpa (atmospheric pressure). Liquefied carbon dioxide gas that was supercooled to the point where it intersects with the triple point in the isobaric state is adiabatically expanded, then passed through a production amplification mechanism and cooled to approximately -75 ° C, and crossed at 0.1 MPa along the dryness at this time. The above-described generation and amplification mechanism is a tubular body having a resistance of approximately 0.25 Mpa.

The dry ice producing apparatus according to the present invention further comprises a heat exchanger for supercooling the liquefied carbon dioxide and a means for adiabatically expanding the liquefied carbon dioxide passing through the heat exchanger to 0.1 Mpa (atmospheric pressure). The above-mentioned production / amplification mechanism is characterized in that a production / amplification mechanism which is a tubular body having a resistance of approximately 0.25 Mpa is attached to the adiabatic expansion means. It is characterized in that it is connected to a dry ice forming machine having a gas exhaust port, and the dry ice forming machine is provided with a press chamber.

[0009]

With the above structure, the predetermined enthalpy (thermodynamic state quantity having the dimension of energy) is deprived by supercooling up to the point intersecting the triple point, and the dryness with a large amount of solids. In this state, adiabatic expansion (injection) is performed to 0.1 MPa (atmospheric pressure), and a large yield can be secured and a dry ice snow can be obtained as compared with the conventional case.
Furthermore, during adiabatic expansion, a conduit with a resistance of about 0.25 Mpa is passed to cool it to a lower temperature,
The yield is further improved due to the action at a dryness with a higher solid content.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block circuit diagram showing a dry ice manufacturing apparatus embodying the present invention, FIG. 2 is a carbon dioxide enthalpy diagram showing the same adiabatic expansion point, and FIG. 3 is also an adiabatic expansion point in the case of not using a production amplification mechanism. Is a carbon dioxide enthalpy diagram showing FIG. 4, FIG. 4 is a view showing a conduit as a production / amplification mechanism, FIG. 5 is a process drawing of dry ice, and FIG. 6 is a view showing a dry ice molding machine.

In these figures, reference numeral 1 denotes a supply source of liquefied carbon dioxide gas, and this liquefied carbon dioxide gas used is contained in a high-pressure container (cylinder). The liquefied carbon dioxide gas is shown in FIG. As described above, the raw material gas is cleaned in a washing tower to obtain pure pure carbon dioxide gas through a purifying device, which is then applied to a gas compressor and condensed by a condenser through a refining / drying device. The pressure is set to 20 ° C. and the pressure is set to 1.8 Mpa to 2.0 Mpa.

The liquefied carbon dioxide gas thus supplied is connected to the refrigerator 2 by the refrigerant pipe 3 in a heat exchanger (supercooler).
Sent to 4 ... A plurality of the heat exchangers 4 ... Are connected to gradually cool the liquefied carbon dioxide to lower the temperature.

The supercooling by the heat exchangers 4, 4 ... Is shown by an enthalpy diagram of carbon dioxide at a supply pressure of liquefied carbon dioxide of 2.0 Mpa (1.967 Mpa to be precise) and a temperature of -20 ° C. From point A (as described above) that intersects the saturated liquid line, the saturated liquid line is a triple point under the isobaric condition (the point where solid, liquid and gas exist at the same time, and the absolute pressure is 0.5).
Up to point C (see FIGS. 2 and 3) that intersects 18 Mpa and a temperature of −56.6 ° C.). At this time, the enthalpy between X and Y shown in FIGS. 2 and 3 is 73 KJ / Kg (17.4 Kc).
al / Kg) will be robbed.

In this state at point C, the liquefied carbon dioxide gas passes through a solenoid valve 6 operated by a solenoid 5, and is squeezed at its tip to be sent to a conduit 8 as a jet nozzle for adiabatic expansion which constitutes a throttle valve 7, and dry ice. Is sent to the molding machine 9.

The supercooled liquefied carbon dioxide gas was added to 0.1 Mpa.
The work of adiabatic expansion (injection) to (atmospheric pressure) is the above-mentioned C
The saturated liquid line reaches the point D where the triple point intersects at the time of this adiabatic expansion. Adiabatic expansion must be done at pressures and temperatures above the triple point. This is because when the temperature and pressure are below the triple point by supercooling, dry ice snow is generated in the conduit 8 and clogs the conduit 8, and the carbon dioxide gas keeps the liquid state only in the state above the triple point, Does not interfere with liquidity issues.

Further, between the conduit 8 and the dry ice molding machine 9 described above, a generation / amplification mechanism of about 0.25 MPa is provided.
The tubular body 10 having the resistance of is interposed. In this pipe 10, the liquefied carbon dioxide gas adiabatically expanded by the conduit 8, particularly the throttle valve 7, is cooled to -75 ° C (point E). That is, the tubular body 10 exists between points D and E in FIG. Along with the dryness when cooled to −75 ° C., it is possible to reach from the point E to the point F intersecting with 0.1 MPa (atmospheric pressure). Since this point F intersects with a line having a dryness of 0.4, that is, a line having a gas of 40%, it can be seen that the solid content is 60%, that is, the dry ice snow is 60%.

Further, the dry ice molding machine 9 is provided with a dry ice snow diffuser 11 to which the tip of the pipe 10 is connected and opened, and the diffuser 11 has a discharge port for carbon dioxide gas which has become a gas. 12 are provided.

A stack of dry ice snow press chambers 13 is provided in communication with the diffusion unit 11 described above. The press chamber 13 has a cylindrical shape, a shielding (receiving) hydraulic cylinder 14 is exposed at one opening, and the piston 1 is internally provided from the other opening.
A press hydraulic cylinder-15 for press-fitting 5a and compressing dry ice snow is exposed. The pressing chamber 13 can also be used as the radiating portion 11 as shown in FIG. 6, and reference numeral 17 in the drawing denotes dry ice formed by pressing.

The dry ice forming machine 9 shown in FIG.
16 is the one that omits the tubular body 10 as the generation and amplification mechanism.
・ 16 indicates piping for pressure oil.

The carbon dioxide enthalpy diagram when the tube body 10 is omitted is shown in FIG. In this case, the process of subcooling from point A to point C at a constant pressure is the same, but adiabatic expansion is performed from point C to reach point D, which intersects with 0.1 MPa (atmospheric pressure). The dryness at point D in FIG. 3 is located between 0.4 and 0.5 and is about 47% or lower. Therefore, it is understood that the yield of solids is 53% or more, that is, 53% or more even when the tubular body 10 (generation / amplification mechanism) is not present.

[0021]

The method and apparatus for producing dry ice according to the present invention are constructed and function as described above. Therefore, it is possible to achieve a high yield, which can be said to be a physical limit, under the condition of liquefied carbon dioxide gas as a raw material to be supplied, and the production efficiency is extremely excellent.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a dry ice manufacturing apparatus embodying the present invention.

FIG. 2 Carbon dioxide enthalpy showing adiabatic expansion points
It is a diagram.

FIG. 3 is a carbon dioxide enthalpy diagram showing adiabatic expansion points in the case where a generation / amplification mechanism is not used.

FIG. 4 is a diagram showing a conduit as a generation and amplification mechanism.

FIG. 5 is a manufacturing process diagram of dry ice.

FIG. 6 is a view showing a dry ice forming machine.

FIG. 7 is a carbon dioxide enthalpy diagram according to a conventional manufacturing method.

[Explanation of symbols] Source of liquefied carbon dioxide 2 refrigerator 3 Refrigerant piping 4 heat exchanger 5 solenoid 6 Solenoid valve 7 Throttle valve 8 conduits 9 Dry ice molding machine 10 tubes 11 Dispersion part 12 outlet 13 Press chamber 14 Shield hydraulic cylinder 15 Press hydraulic cylinder 16 Pressure oil piping 17 dry ice

Claims (6)

[Claims] 1. A supply pressure of liquefied carbon dioxide is approximately 2.0 Mp.
a, at a temperature of approximately -20 ° C, the liquefied carbon dioxide gas is supercooled from a point intersecting the saturated liquid line to a point intersecting the triple point in an isobaric state, and adiabatically expanded to 0.1 Mpa (atmospheric pressure) in that state. A method for producing dry ice, characterized in that 2. In the above-mentioned step, the liquefied carbon dioxide gas that has been supercooled to a point intersecting the triple point in the above-mentioned equal pressure state is adiabatically expanded and then passed through a production / amplification mechanism to obtain about −7.
Cool to 5 ℃, and dry according to the dryness at this time to 0.1 MPa.
The method for producing dry ice according to claim 1, wherein the dry ice is reached at a point intersecting with. 3. The generation and amplification mechanism described above is approximately 0.25 Mp.
The method for producing dry ice according to claim 2, wherein the tube body has a resistance of a. 4. A heat exchanger for supercooling liquefied carbon dioxide and liquefied carbon dioxide passing through the heat exchanger are set to 0.1 Mpa.
An apparatus for producing dry ice, comprising: means for performing adiabatic expansion (atmospheric pressure). 5. The means for adiabatic expansion described above has a value of approximately 0.
The dry ice manufacturing apparatus according to claim 4, further comprising a generation / amplification mechanism that is a tubular body having a resistance of 25 Mpa. 6. The production / amplification mechanism described above is connected to a dry ice forming machine having a gas exhaust port, and the dry ice forming machine is provided with a press chamber. Dry ice manufacturing equipment.