JPS5911526B2 - Dry ice manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes commercially available low water content liquefied carbon dioxide (hereinafter referred to as LCO).
2) in producing dry ice from L.
This invention relates to a method for humidifying CO2.

In recent years, small dry ice making machines have been used to produce 0.2~10k
It is becoming increasingly common to produce dry ice as small as 1.5 oz. in the region where it is consumed, but the raw material, LaO2, is used in large quantities for welding, soft drinks, etc., and its dew point temperature is -40°C. Water content is very low.

When producing dry ice from liquefied carbon dioxide, if it does not contain an appropriate amount of moisture (dew point temperature: -15°C to -130°C, see Table 1), the inside of the dry ice will deteriorate over time after it is formed. Since the dry ice becomes rough and brittle, this type of dry ice is considered to be degraded dry ice, and this is a generally known fact.

On the other hand, dry ice manufacturers that produce large quantities of large dry ice at their factories prevent deterioration by adjusting the amount of moisture contained in the raw material, liquefied carbon dioxide, to an appropriate level. .

Therefore, when producing dry ice from LaO2 stored in a low-temperature container or storage tank at a consumption site, it is conceivable to add an appropriate amount of moisture, but if the pressure of LaO2 is 20
kg/cI! Since the temperature of the liquid is high, and the temperature of the liquid is as low as -20°C, it is actually quite difficult to humidify it.

However, as mentioned above, in order to produce dry ice that is hard, dense, and resistant to deterioration, it is necessary to use the vapor pressure of ice to maintain the dew point temperature of the low-temperature LaO2 liquid (around -20°C).
The inventor noticed that the objective could be achieved by humidifying aO2, and discovered a method for manufacturing dry ice by simply and continuously humidifying LaO2.

This will be explained in detail below with reference to FIG. 1 and examples.

Cryogenic container or storage tank 1 filled with LaO2 at low temperature
A pressure-resistant humidifying container 3 is provided in the middle of the piping connecting the dry ice manufacturing machine 2 and the dry ice manufacturing machine 2.

Appropriate nets or the like are placed at the inlet and outlet of LCO7 in the container to prevent the ice or porous material in the filling from moving due to the passage of LaO2.

Further, if necessary, a water injection valve 4, a drain valve 5, etc. may be installed above and below the container.

Furthermore, if one or more such humidifying containers are provided, there is an advantage that dry ice can be produced for a long time by alternately using them.

Fill this humidifying container with crushed ice, open the valve of the cryogenic container or storage tank 1, and slowly let low-temperature LCO2 pass through.
Ice is cooled by LCO2, and LCO2 is cooled by its liquid temperature (-
Since the dry ice is humidified to a dew point temperature close to the moisture saturation point (approximately 20° C.), dry ice of the required quality can be obtained by producing dry ice with this humidified LCO2.

In addition, a porous material such as natural, synthetic, or metal having a high water retention property is housed in the humidifying container 3, water is impregnated with the material, and the water is rapidly removed by passing low-temperature LCO2 in the same manner as above. Since it becomes ice at the same temperature as LCO2 and can be used in the same manner as described above, humidified LCo□ can be supplied to a dry ice manufacturing machine.

Example 1 As shown in the flow sheet of Figure 1, the inner diameter is 80 mm and the length is 32 mm.
A piece of crushed ice is placed in a cylindrical pressure-resistant humidifying container 2 of 0°C, and low-temperature LCO2 (pressure 19 to 9/c111, liquid temperature -21°C, dew point temperature -60°
C5 (moisture content 0.0004% by weight) per minute.
Dry ice was manufactured using dry ice manufacturing machine 1 (Dry Ice MD-058 model manufactured by Liquefied Carbonate Co., Ltd.) by passing through the mixture at a flow rate of 6 kg.

At this time, the liquefied carbon dioxide gas is humidified at the entrance of the dry ice manufacturing machine to a dew point temperature of -26°C1, or 0.0231% by weight, and the dry ice manufactured with this liquefied carbon dioxide gas has a glossy surface immediately after manufacturing. Its density is 1.5 to 9
/l.

Furthermore, no rough areas were formed even after 48 hours had passed.

In other words, no deterioration of the dry ice was observed.

Example 2 Large and small chunks of sintered metal were placed tightly in the humidifying container of Example 1, water was poured over the container to moisten the sintered metal chunks, and excess moisture was discharged through a valve at the bottom.

Next, the LCO2 is collected very slowly at first from the LCO2 container.
Example 1
Dry ice was produced under the same operating conditions as in Example 1, but the quality of the dry ice was the same as in Example 1.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet common to Example 1 and Example 2 of the present invention. 1 is a low temperature container or storage tank for liquefied carbon dioxide gas, 2 is a dry ice making machine, 3 is a pressure-resistant humidifying container, 4 is a water injection valve, and 5 is a drain valve.

Claims (1)

[Scope of Claims] 1. When manufacturing dry ice, one or more humidifying containers are installed between a liquefied carbon dioxide gas low temperature container or its storage tank and a dry ice manufacturing machine, and crushed ice pieces are packed in this container. A method for producing dry ice characterized by humidifying liquefied carbon dioxide gas by passing low-temperature liquefied carbon dioxide gas with a low moisture content through the ice. 2. When manufacturing dry ice, one or more humidifying containers are installed between the liquefied carbon dioxide gas low-temperature container or its storage tank and the dry ice manufacturing machine, and a porous material is filled in the container, and water is poured into the container. 1. A method for producing dry ice, which comprises absorbing and then passing low-temperature liquefied carbon dioxide gas with a low water content to generate ice, and humidifying the liquefied carbon dioxide gas by passing the liquefied carbon dioxide gas through the ice.