The solid form of carbon dioxide is known as dry ice. Dry ice plants are dry
ice generating systems. All carbon dioxide plants usually have a dry ice
plant as well which produces carbon dioxide and dry ice. Dry Ice is produced
by lowering the pressure of liquid carbon dioxide. The temperature at which
carbon dioxide turns into an opaque white solid is -109°F (178.5°C).
In gas plants, dry ice is manufactured basically in two forms: a block of
dry ice (50 lb or 22.7 kg) or in small pieces in different sizes from the
size of a grain of rice to a larger pellet. Dry ice is considered as one of
the important tools that has found many applications in various industrial
and commercial purposes.
Manufacturing process
The steps involved in the manufacturing of dry ice in gas plants are as
follows:
- By compressing, cooling, liquefying at a pressure of approximately
870 lb/in2 at room temperature, carbon dioxide is liquefied. The
pressurized, refrigerated liquid CO2 is pumped into huge
tanks or rail cars and transported to the premises of dry ice plants so
that dry ice manufacturers can remove the liquid required.
- The tank trunk dumps the liquid CO2 into huge tanks on
the premises, which hold the liquid refrigerated so that it remains in
liquid state. Usually the tanks are located adjacent to the factory wall
and with the use of pipes the liquid is brought directly inside when
required for manufacturing.
- The liquid CO2 is moved into the dry ice press at the
time of manufacturing. When the liquid moves from a highly-pressurized
environment to atmospheric pressure, it expands and evaporates at high
speeds. This leads the liquid to cool to its freezing point. A nozzle is
used to put the liquid into the top block of a dry ice press. There is a
large block at the top of the press that can exert extreme pressure on
the product that is brought into it. Since the liquid CO2 is now at room
temperature, it immediately solidifies when it touches the dry ice
press. The carbon dioxide now appear like snow.
- This snow at the top is now compressed into a block of dry ice. In
other words, the top portion of the press goes up and down with heavy
pressure, breaking the snow into a solid block of dry ice. This at the
most takes five minutes. When the block is solid, it is generally about
2 ft wide and 10 in high, weighing about 100 kg.
- This block of dry ice now cones out of the press and moved onto a
roller. A pneumatic saw cuts the block in half, which are then pushed to
another saw that cuts the smaller blocks yet again. The single block of
dry ice is now in four pieces, each weighing about 25 kg.
- These dry ice blocks are stored in containers which keep them solid
and which are then transported for various purposes.
Formation of dry ice: A
diagrammatic representation
Quality Control
Since dry ice is particularly used in the food industry, adequate
precautions must be taken by dry ice manufacturers to produce pure quality
dry ice. This of course depends on the grade of the carbon dioxide. It is
necessary that manufacturers should certify and test the liquid carbon
dioxide used, as well as the purity of the manufactured product. Other
quality control issues involved are that tanks and equipment used are
working in good conditions. If pressure is not properly maintained, dry ice
cannot be produced. Moving the dry ice quickly and efficiently from cutting
to storage is very important. This is because dry ice quickly sublimates at
room temperature, which in turn reduces the weight and hence the price of
the product. Shipping of the product should be in such a way so that they do
not melt while on transportation.
Dry ice varieties
The manufacturers of dry ice in gas plants produce dry ice in various sizes
and shapes, specific to its applications. Some of the varieties of dry ice
are as follows:
| High Density Dry Ice Pellets: Usually 1/8" in size to
be used in dry ice blast cleaning systems. |
 |
 |
Dry Ice Rice Pellets: 1/4" diameter in size used in
frozen food applications. |
| Dry Ice Standard Pellets: 1/2" diameter, used in
frozen food applications, meat processing plants, transportation of lab
specimens and blood plasma. |
 |
 |
Dry Ice Slabs: Manufacturers can supply in standard sizes
or in custom sizes. Usually wrapped in kraft paper or in poly and
transported to be used for various industrial purposes. |
| Dry ice blocks: Weight is around 60 lbs, in the size 10 x
10 x 12. Used in frozen food applications, grocery warehouses and in
shipping ice cream. |
 |
Uses of dry ice
A versatile, dry ice has a number of commercial and consumer uses:
- Dry ice is used in the poultry industry.
- It is used in the baking industry.
- It is used to remove floor tiles.
- It is used to remove skin imperfections.
- It lengthens the life of wet ice.
- In the entertainment industry, dry ice is used to create fog.
- It shrinks metal.
- Dry ice retards chemical catalysts.
- It improves the porosity in oil wells.
- Dry ice is used to pack ice cream on trips.
- It is used to store food during power failures.
- For low-temperature testing, dry ice is used.
- It can act as a mosquito attractant for traps.
- It is used by airline/railway caterers to keep food chilled.
- It is used by blood banks for shipping.
- Dry ice is also used to blast clean rubber and plastic injection
molds.
- It is also used to clean food processing equipment.
- It is used to blast clean fire-damaged buildings.
- Dry ice frequently used by the concrete industry to prevent heat
build up.
- Another important use of dry ice is to germinate food.
Dry
Ice Plant
