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Ammonia-alcohol refrigeration system

Natural refrigerant cooling unit “Bacchus” series

The natural refrigerant indirect cooling unit “Bacchus” series is an earth-friendly and safe cooling unit that uses ammonia and ethanol.

Bacchus image

Characteristics of an ammonia and ethanol system

Characteristics of an ammonia and ethanol system

Why does Bacchus use “ammonia” and “ethanol”? There is a reason!!

1 Refrigerants are now at a turning point...

 As a freezing refrigerant, ammonia had been used a long time ago. After the commercialization of the CFC refrigerants in 1930s, their odorless and low-toxic characteristics led the CFC (R12) and the HCFC (R22) to be widely used in the freezer air-conditioner field. However, the ozone depletion caused by these refrigerants became a global issue, resulting in the 1995 ban on the manufacture of R12. R22 was banned from replenishment for new freezing equipment after 2010. For existing freezing equipment, newly manufactured R22 is to be banned from replenishment after 2020, and the manufacture phase-out plan for R22 has been implemented.
 Such regulations have been implemented in response to the commercialization of the HFC refrigerants that do not deplete the ozone layer (such as R404A and R134a). However, these refrigerants also have as high Global Warming Potentials (GWP: an index obtained by comparing the global warming capacity of CO2 defined as 1) as 1430 to 3920; hence, they became subject to the emission restriction for global warming prevention, making it necessary for them to be replaced by a new refrigerant.

Turning point of refrigerants (Fig. 1)

 As for R134a, which is used for air-conditioners, a refrigerant with a GWP as low as 4 (HFO-1234yf) has been developed, and has started to be commercialized in Europe. However, as for R404A and R407C, which are used for freezing, refrigerants with a low GWP are yet under development and give no clear prospects for commercialization, making it difficult to take action on the issue. Should we wait for the commercialization of a low-GWP refrigerant while using HFCs, or should we go back to natural refrigerants such as ammonia...? Now, refrigerants are at a turning point.

Turning point of refrigerants (Fig. 2)

 Under such a situation for freezing refrigerants, NISSIN has been examining countermeasures from aspects of both CFC refrigerants and natural refrigerants in an attempt to flexibly cope with the issue.

2 Comparison of ammonia refrigerant systems

 Ammonia is the most popular natural refrigerant. Ammonia refrigerants do not deplete the ozone layer or have any global warming effect. However, they have a strong odor, are toxic, and slightly flammable, requiring safety consideration. The following shows a comparison of the characteristics of ammonia refrigerant systems.

Two-stage compression system

Two-stage compression system

Indirect cooling system by CO2 refrigerant

Indirect cooling system by CO<sub>2</sub> refrigerant

Indirect cooling system by standard brine

Indirect cooling system by standard brine

Comparison of the systems

Comparison of the systems

*Issues of CO2

  • 1) Despite that the system uses CO2 as a secondary refrigerant, it needs a high-pressure-specification device.
  • 2) Even when the cooling operation is stopped, CO2 pressure control is required, making the system itself complex as well.

Issues of CO<sub>2</sub>

Since CO2 cannot be heated to -5°C or higher, one of the following operations needs to be performed.

  • 1. Install an expansion tank (with a capacity of 150 times as much as the liquefied CO2) into the system.
  • 2. Operate the NH3 freezer when the CO2 pressure in the system increases.
  • 3. Install a small freezer for maintaining temperature.
  • 4. Release CO2 to the atmosphere when the system is stopped for a long period of time.

Easily unstoppable system

3 Natural refrigerant indirect cooling system from Nissin

NISSIN’s natural refrigerant cooling system “Bacchus” ensures safety and maintainability by using “ethanol brine “ as a medium for cooling the refrigerator.

Advantages of ethanol brine

Advantages of ethanol brine

Bacchus has other features than brine.

Other features of Bacchus

Is ethanol brine hazardous?

According to the International Chemical Safety Card,

International Chemical Safety Card

    the flash point of 59% ethanol is 22°C (concentration in the air: 3.3%).

  •  - 22°C or lower: No risk of ignition.
  •  - 22°C or higher: Ignition does not occur if the concentration in the air is 3.3% or lower.
  •            ⇒ This can be coped with by ventilation.

(Reference) Descriptions on the International Chemical Safety Card for CO2

Although the permissible concentration is 5000 ppm,
As for “physical hazard,” it is heavier than the air, and in a place where the ceiling is low, it may cause oxygen deficiency.
As for “inhalation hazard,” if the container is opened, the liquid evaporates very rapidly. In a closed room, it pushes the air out of the room, potentially causing the risk of suffocation.

⇒ In the case of CO2, the boiling point under atmospheric pressure is as significantly low as -79°C. Hence, an entire leak will be gas.
Since CO2 gas is heavier than the air, it builds up at the bottom of a room.

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