JPS58176113A - Preparation of solid carbon dioxide gas and liquefied carbon dioxide gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing solid carbon dioxide and liquefied carbon dioxide.

Conventionally, the following methods have been used to industrially produce solid carbon dioxide) and liquefied carbon dioxide.

Petroleum-based hydrocarbons such as naphtha or butane are heated, and the resulting crude carbon dioxide gas is received as a raw material. After removing impurities such as sulfur through a washing group and a desulfurization tower, the pressure is increased by a compressor. Then, it is passed through a dehumidifier to remove moisture, then cooled and liquefied in a refrigerator, sent to a purification tower for flushing, and contains small amounts of hydrogen, oxygen, and nitrogen.

Impurities such as methane are completely purged to produce high-purity liquefied carbon dioxide.On the other hand, solid carbon dioxide is produced by sending liquefied carbon dioxide from a storage tank to a molding machine, adiabatically expanding it in the molding machine, and cooling it. The snow-like dry ice obtained by the effect is compressed, molded, cut, and processed into products through automatic packaging. A common table manufacturing method was to return the gas generated in the molding machine to the suction side of the compressor, recompress it, and liquefy it.

In this conventional method, the raw carbon dioxide gas is purified and then
This is a process in which liquefied carbon dioxide is produced by compressing from about jo to 70 ata, and this is cooled by a refrigerator, and this liquefied carbon dioxide is ejected under reduced pressure into a pressure molding machine to produce solid carbon dioxide. In addition, power consumption is large, requiring investment in equipment such as compressors and refrigerators, and operating costs have become difficult to overlook due to the recent rise in electricity rates. Therefore, in order to reduce power consumption, capital investment, and operating costs, methods for producing liquefied carbon dioxide and solid carbon dioxide using the cold energy of LNG are being studied, and some methods have already been developed. It is being implemented. I will discuss them next.

As is well known, as the consumption of LNG increases in Japan, development in the field of effectively utilizing the cold energy of LNG is actively progressing. The use of LNG for cold energy has also begun to be considered, and many reports on this topic have been introduced. There are generally the following three methods for producing solid carbon dioxide gas and liquefied carbon dioxide gas using the cold energy of LNG.

(1) The compression, purification, and liquefaction processes are basically the same as conventional methods, but this method utilizes the cold energy of LNG and eliminates the need for a refrigerator to cool carbon dioxide to around the triple point temperature.
This allows the compressor power required in the past to be reduced, and among the methods that utilize the cold energy of LNG, this method is the closest to the conventional method for producing liquefied carbon dioxide. In addition, 0(2) LNG is used to obtain solid carbon dioxide from this liquefied carbon dioxide.
A method for producing solid carbon dioxide by directly contacting liquid nitrogen or liquid oxygen produced by a cryogenic separation device using cold heat with a low-temperature refrigerant such as a mixture thereof or LNG itself and raw carbon dioxide under normal pressure, and a low-temperature refrigerant or I,NG
A method for producing liquefied carbon dioxide gas from separated solid coal gas.

(3) Generate solid carbon dioxide gas on the heat transfer surface by exchanging heat between low-temperature refrigerant or LNG and low-pressure raw carbon dioxide gas of less than 5.2 J at& using a heat exchanger,
A production method for extracting this and a method for producing liquefied carbon dioxide from solid carbon dioxide.

Among these, manufacturing methods (2) and (5) are based on LNG
The raw carbon dioxide is directly and indirectly cooled at a pressure below the triple point without using a compressor or refrigerator using the cold heat of the gas to produce solid carbon dioxide, and from this, liquefied carbon dioxide is produced. This is what I am trying to do.

These methods of producing solid carbon dioxide gas and liquefied carbon dioxide gas using the cold energy of LNG each have disadvantages when put into practical use. In other words, in the production method (1), which pressurizes the raw carbon dioxide gas, refines it, and cools it using the cold energy of LNG, a refrigerator is not required, but the raw carbon dioxide gas is kept under triple pressure! , power is required to pressurize to more than 1ata. On the other hand, in method (2), 1. Low-temperature refrigerants such as liquid nitrogen and liquid oxygen are expensive to manufacture due to rising equipment and operating costs, and also require a large amount of electric power to manufacture. Furthermore, since it is difficult to recycle these media, the amount of media consumed to produce unit solid carbon dioxide increases, and the cost of producing solid carbon dioxide increases. Regarding the method of producing solid carbon dioxide by direct contact with LNG, since the raw material carbon dioxide is at about normal pressure, I, NG4 is required at about normal pressure, but LNG is gasified and transported far away. Due to the need for pressure-feeding over a distance, a gas pressure of io to 10 ata is normally required at the time of shipment.

For this reason, boosting the pressure of vaporized gas after using LNG at normal pressure requires pressure boosting equipment and power for boosting the pressure. It is disadvantageous. Conversely, when LNG under high pressure and raw carbon dioxide gas are brought into direct contact, it is necessary to increase the pressure of raw carbon dioxide gas, which is similarly disadvantageous.

Furthermore, in the method (5), when liquid nitrogen and liquid oxygen are used as the low-temperature refrigerant, there is a problem in the cost of the refrigerant, as in (2) above. Also, when using refrigerant KLNG,
As solid carbon dioxide adheres to the heat transfer surface of an indirect heat exchanger, the thermal conductivity decreases, so it is necessary to remove it, which makes the equipment complex and requires power to remove it. Become.

The present invention has been made to overcome the various drawbacks seen in the above manufacturing methods, and is composed of the following two parts.

(1) Without using expensive and difficult-to-recover refrigerants such as liquid nitrogen or liquid oxygen, and without directly using LNG, which requires a high pressure state during shipping, heat can be exchanged indirectly with the cold energy of LNG. The obtained low-temperature intermediate refrigerant and the raw material carbon dioxide are brought into direct contact in a phase changer or the like to solidify the raw material carbon dioxide.

(2) The solid carbon dioxide precipitated in the intermediate refrigerant is heated and heated together with the intermediate refrigerant, and the pressure is increased to the triple point or higher, and the solid carbon dioxide is compressed to liquefy the solid carbon dioxide.Then, it is separated from the intermediate refrigerant due to the difference in specific gravity, etc., and liquefied. To extract carbon dioxide gas.

Examples of the present invention will be specifically described below.

First, an example of solid carbon dioxide production will be explained based on FIG. 1 is an intermediate refrigerant storage tank such as 70 N/J, ethylene, etc., which is made of an insulated pressure-resistant container, and is connected to the phase change @J by an insulated pipe. And pulp! is located. The phase changer J is a heat-insulated, pressure-resistant container, and is a device for producing solid carbon dioxide gas. An intermediate refrigerant such as 70 g/J, ethylene, etc., stored in the intermediate refrigerant storage tank 1, is forced into the phase change IIJ by a pumper for pumping the intermediate refrigerant through the pulp j, and is formed into a predetermined groove. After transferring the refrigerant between f, the pump for pumping the intermediate refrigerant is stopped, and the pulp! Make it a closed shape 11. On the other hand, the intermediate refrigerant is cooled by LNG heat exchange 114. The LliG heat exchanger≦LN
It exchanges heat between the cold energy held by G and the intermediate refrigerant, and is connected to the phase changer 3 in a loop through an insulated pipe 7, between which an intermediate refrigerant circulation pump l and a valve 9 are connected.
, 10 are arranged. After a predetermined amount of intermediate refrigerant is injected into the phase changer 3, the intermediate refrigerant circulation pump l
By passing through the NG heat exchanger 6, the LNG is cooled down to about -/IIO°C by the cold heat possessed by the LNG. This intermediate refrigerant is continuously cooled during the solid carbon dioxide generation process. During this time, valve 9. Open your IQ. When the intermediate refrigerant in the phase changer 3 is cooled by the LNG heat exchanger 4, it is washed from the blower 13 through the carbon dioxide pipe//and valve 12.

The desulfurized and dehumidified carbon dioxide gas is continuously fed into the phase changer 3. In the converter 3, the raw carbon dioxide gas is cooled down to about -10°C in direct contact with a low-temperature intermediate refrigerant and sublimated into solid carbon dioxide gas. When the generation of solid carbon dioxide gas is completed in the phase changer 3, the valve 12 is closed to stop feeding the raw carbon dioxide gas, and at the same time, the intermediate refrigerant circulation pump t is also stopped, and the valves 9 and 10 are closed. state. The solid carbon dioxide gas generated in the phase changer 3 is transferred to the valve/4
1, the mixture of solid carbon dioxide and intermediate refrigerant is transferred to the separator t3. The separator t1. The nine containers are thermally insulated and equipped with fine-mesh filter separation plates, etc., to separate solid carbon dioxide from intermediate refrigerant. In addition, when extracting the mixture of solid carbon dioxide gas and intermediate refrigerant from the phase changer J, open the valve 17 installed between the carbon dioxide pipe l≦ connecting the blower/J and the upper part of the phase changer J. As a result, raw carbon dioxide gas is fed into the phase changer 3. When the extraction of the mixture is completed, the valve 17 is closed and the blower 13 is stopped. Solid carbon dioxide gas and intermediate refrigerant are separated inside the separator IS, and the intermediate refrigerant accumulated at the bottom is transferred to an insulated pipe /I connecting the separator /ji and the intermediate refrigerant storage tank l, valve 1.
9, the intermediate refrigerant is returned to the intermediate refrigerant storage tank 1 by the operation of the intermediate refrigerant return pump. When the intermediate refrigerant in the separator/3 is completely returned, the intermediate refrigerant return pump X is stopped and the valve 19 is closed. If a small amount of intermediate refrigerant remains in the solid carbon dioxide gas left in separator Ij, only the intermediate refrigerant is vaporized due to the boiling point difference, and valve J
Open it and release it out of the system.

After discharge, valve 1 is closed. Thereafter, solid secondary gas is taken out from the separator/jj.

The above is an example of producing carbon dioxide gas from an image body.

Next, an example of producing liquefied carbon dioxide gas will be explained in terms of percentages in FIG. 2.

The explanation will begin from a state in which a predetermined amount of gaseous carbon dioxide gas and an intermediate refrigerant (propane in this embodiment) are contained in the phase change WjJ. Only the valves 9, 10 and 12 are open, and propane is passed through the LNG heat exchanger 4 with less propane than the intermediate refrigerant circulation pump IK, and is cooled down to -1C@g using the cold energy held by the LNG. The solid propane is continuously cooled during the production process of solid carbon dioxide gas, and is circulated and supplied to the phase changer 3 through an insulated pipe 7. At the same time, the blower 1 is connected through the 1 charcoal gas pipe// and 12.
From step 3, raw carbon dioxide gas that has been washed, desulfurized, and dehumidified is continuously injected into the phase change chamber 11J. In the phase change 11J, the raw carbon dioxide gas is cooled to about -101: by direct contact with low-temperature propane, and sublimated into solid carbon dioxide gas.

When the generation of solid carbon dioxide gas is completed in the phase changer 3, the pulp lλ is closed, the injection of the raw carbon dioxide gas is completed, and at the same time, the intermediate refrigerant l is stopped and the pulp filter /θ is also closed. Closed state 0 Next, in order to heat and raise the temperature and pressure of propane and solid carbon dioxide sealed at about -10°C in the phase changer 3, one pulp liter is opened and the inside of the phase changer 3 is heated. A heat medium is caused to flow into the heating tube 1. The temperature inside the phase changer 3 begins to rise, the thermometer and n show -j≦, ≦℃, and the pressure gauge S shows j,
’ indicates kot ata.

(This state of S* and pressure is the triple point of carbon dioxide.)
If you continue heating in this state, the temperature will increase.

After holding this value together with the pressure for a while, the temperature and pressure begin to rise. At this point, all solid carbon dioxide becomes liquefied carbon dioxide. When the concentration and pressure are, for example, −jf °C, j, r ata, the pulp l
Close to complete heating. At this time, in the phase changer 3, both propane and carbon dioxide are in a liquid state, and the specific gravity of liquid carbon dioxide is /, /7, and the specific gravity of propane is 0.6, so the phase change occurs above [97]. Propane is divided into 1 and liquefied carbon dioxide gas is divided downward. That is, it is a separation means based on a difference in specific gravity.

Next, operate the intermediate refrigerant pressure pump l, and the pulp! At the same time, the propane in the intermediate refrigerant storage tank 1 is forced to be sent to the phase changer 3 through the insulated pipe.
Pulp I# is opened and the liquefied carbon dioxide produced in the phase changer J is sent through the insulated pipe B to the liquefied carbon dioxide storage tank.

(In this state, the pressure inside the intermediate refrigerant storage tank 1 becomes low because the nitrogen gas is expanding.) A predetermined amount of liquefied carbon dioxide produced in the phase changer 3 was sent to the liquefied carbon dioxide storage tank. After that, Pulp! At the same time, the pumper for pumping the intermediate refrigerant is stopped.

Next, a predetermined amount of propane in the phase changer 3 is returned to the intermediate refrigerant storage tank l via the insulated pipe /I.
1 is opened, the intermediate refrigerant return pump Thereafter, the pulps 17 and 19 are closed, and the intermediate refrigerant return pump X is stopped. (In this state, the pressure inside the intermediate refrigerant storage tank 1 becomes a high pressure state as the nitrogen is compressed.) By repeating the above operations, liquefied carbon dioxide gas is produced. The gas and propane are dispersed based on the difference in specific gravity, and the liquefied carbon dioxide gas is recovered into the storage tank b using this difference in specific gravity.
An electromagnet is movably disposed on the outside of the J-40, and the excitation effect of the electromagnet is used to facilitate separation. Separation methods such as the dialysis method, the precision method that uses pressure to separate liquids through membranes, the ultrafiltration method, and the reverse osmosis method are also used, so there is no need to specify ratio 1 difference separation as this separation method. do not have.

As described above, according to the present invention, methods for producing solid carbon dioxide gas and liquefied carbon dioxide gas include conventional production methods and conventional production methods using LNG cold energy, etc., as can be understood from the description of the embodiments. This is a non-groundbreaking invention as it can completely eliminate the drawbacks of .

In other words, there is no need for a carbon dioxide compressor or refrigerator equipment, which reduces equipment costs and requires less space for installation, and the intermediate refrigerant for direct contact can be replaced with a general-purpose, inexpensive hydrocarbon-based one. The amount consumed is extremely small because it can be recycled and used7. Furthermore, LNG pressure □
It has excellent features such as being unaffected by environmental factors, the equipment is simple, and operating costs are low.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of an apparatus for implementing the method for producing solid carbon dioxide, and Figure 2 is an explanatory diagram for implementing the method for producing liquefied carbon dioxide.Applicant: Kawasaki Heavy Industries, Ltd.

Claims (2)

[Claims] (1) Low-temperature intermediate refrigerant obtained by heat exchange with a cold source such as liquefied natural gas (LNG) and carbon dioxide gas at a low pressure less than the triple point pressure of carbon dioxide gas, s, 2r Ky/cWL2. A method for producing solid carbon dioxide, which comprises direct contact in a phase changer to precipitate solid carbon dioxide. (2) A low-pressure intermediate refrigerant obtained by heat exchange with a cold heat source such as liquefied natural gas (I, NG) and carbon dioxide at a low pressure of less than -1 Kp/cz', which is the triple point pressure of carbon dioxide gas. The solid carbon dioxide precipitated by direct contact with gas in a phase changer is heated to raise its temperature together with a low-temperature intermediate refrigerant.
A method for producing liquefied carbon dioxide gas, which comprises generating liquefied carbon dioxide gas at a pressure equal to or higher than the triple point of carbon dioxide gas, and separating the liquefied carbon dioxide gas from a low-temperature intermediate refrigerant using a separation means such as a difference in specific gravity.