Cooling and temperature control applications with cryogenics

Air Liquide’s cryogenic tunnels and injector devices are designed for use with either cryogen.  Image: Air Liquide

Cryogenic refrigerants such as liquid nitrogen or carbon dioxide (CO2) are commonly used in the meat and poultry industry due to their ability to reduce and maintain the food product’s temperature during the processing, storage, and shipping operations quickly and effectively.

Traditionally, CO2 has been the preferred refrigeration medium due to its higher versatility for use in more cooling applications however in recent years, liquid nitrogen has been gaining in popularity. Let’s examine why.

Carbon dioxide is usually obtained as a by-product from a primary source of industrial manufacturing, such as ammonia plants and ethanol production facilities, where it is then purified and liquified based on food grade specifications.  

Sourcing and supply issues can eventuate with CO2 as these are usually linked to unexpected disruptions at the primary production source.  As a result, this is one of the challenges customers may face when using CO2.  

However, CO2 has unique properties since it can exist as a solid, liquid or gas depending upon its storage pressure and temperature.  

For many food manufacturers, CO2 is stored in bulk tanks on their premises as a liquid at 20 barg and -20 °C.  

But to use CO2 as a refrigeration medium, the liquid needs to be transformed into a solid form, known as “dry ice” or “CO2 snow”, using specialised equipment such as snow horns, in-line CO2 tunnels, bottom injection devices, combo/tote coolers, pelletizers, etc. 

The dry ice then transfers its refrigeration power to the food product, once they are both in direct contact, to cool down the food or maintain it at a refrigerated or frozen temperature without leaving any residue behind.

On the other hand, nitrogen is obtained from air where it is the primary component at approximately 78 per cent. 

An Air Separation Unit (ASU) is used to capture atmospheric air, and then, using a cooling and fractional distillation method, separates the air molecules into nitrogen, oxygen, and argon.  

Nitrogen is then liquefied and stored in specially designed cryogenic tanks at a customer’s site at -196 °C and 2-4 barg. 

Sourcing disruptions are less likely with nitrogen since the primary source is the air rather than another industrial manufacturing process.  

Unlike CO2, nitrogen only exists as either a liquid or gas which limits its versatility because there isn’t a solid phase.  Liquid nitrogen also transfers its refrigeration power to the food product, once they are both in direct contact, to cool down or freeze the food, without leaving a residue. 

The choice for which cryogen to use is mainly driven by the type of cryogenic application along with the sourcing availability and pricing of liquid nitrogen or CO2 since, ultimately, this has a direct impact on the chilling cost for the food product.

Many food processors are also now looking at their carbon footprint to see how that factors into their decision-making process.  

Other cost considerations include the CAPEX for the cryogenic equipment solution and the required infrastructure for the insulated cryogenic piping network, an exhaust system, and safety room monitoring devices.  

Converting an existing cryogenic installation from one cryogen to another requires additional expenditures since quite often the cryogenic pipeline must be changed to meet the pressure, flow, and insulation requirements, in addition to changing the safety room monitoring device so that it is compatible for the cryogen being used.  

Upgrades to the exhaust system may also be required in terms of larger duct diameters and blower capacities.  The overall conversion costs need to be evaluated on a case-by-case basis to determine the economic feasibility of doing so.

Today, it is common to use either liquid nitrogen or CO2 throughout the food processing operations since many of Air Liquide’s cryogenic tunnels and injector devices are designed for use with either cryogen. 

However, a consequence of the global Covid pandemic has been the change in market availability of CO2, predominantly from changes in ethanol and ammonia sources, as a result there has been an increased interest within the food industry for alternatives such as the potential conversion to
liquid nitrogen. 

For cooling and temperature control applications in the mixer/blender operations, Air Liquide designed its CRYO INJECTOR- CB3 so that it can be easily retrofitted onto any OEM brand of equipment, whether it’s new or existing.  

Furthermore, the CRYO INJECTOR- CB3 can be easily converted from CO2 to Nitrogen service, or vice versa, by simply changing the injector insert on the mixer/blender. 

The CRYO INJECTOR- CB3 is the preferred injector, especially with international mixer OEMs, due to its impressive cooling efficiency, hygiene design and overall performance. The injector is also easy to disassemble and reassemble for the cleaning operations.   

 However, CO2 dry ice equipment, such as combo/tote coolers, snow horns, pelletisers, etc. cannot be converted to liquid nitrogen service when CO2 is in short supply so another type of cryogenic solution must be considered, often resulting in a different process layout. 

It will then be necessary for Air Liquide’s ALTEC Food Experts to evaluate the customer’s current process and production parameters to recommend an alternative cryogenic equipment set-up using liquid nitrogen.   

For instance, Air Liquide has performed extensive testing on the feasibility of replacing a CO2 dry ice combo/tote cooler application with a CRYO TUNNEL- FP1 that uses liquid nitrogen instead. 

The CRYO TUNNEL- FP1 tunnel has the same ability to effectively cool down large pieces of meat from the hot-boning operation through a simple process of reconfiguring so that the equipment can be easily integrated into the production line. 

In addition, the hygienically designed CRYO TUNNEL- FP1 has the necessary product clearance and enhancements to the conveyor belt support system to accommodate these types of large & heavy products, which many other brands of cryogenic tunnels simply don’t have.  

Whether you’re concerned about product quality issues, production capacity constraints, CO2 supply shortages, or even reducing your carbon footprint, Air Liquide’s team of experts can assist you in recommending the best cryogen and cryogenic equipment solution.

Our extensive portfolio of cryogenic equipment has been designed with hygiene and operational reliability in mind. 

Many of Air Liquide’s solutions are easily converted from one cryogen to another to minimise the future costs and inconvenience of changing out the existing cryogenic equipment.

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