Sustainable Cooling for Freeze-Drying Applications with LYOAIR®

One of the most significant contributors to global warming is the use of fluorinated gases. Emissions from equipment that utilize them are now considered to be detrimental to the atmosphere and have an effect that’s up to 23,000 times greater than carbon dioxide. Although they’ve been regularly used in freeze dryers for decades, European Union legislation dictates that alternatives must now be found.

As such, GEA has been looking into alternative low-temperature cooling solutions that use natural refrigerants in commercial-scale freeze drying applications. As a result, the company has developed an innovative system using a combination of air cycling (Brayton or Coleman cycle) and carbon dioxide (CO₂)-based cooling.

The LYOAIR^® system, which has been shown to demonstrate high levels of throughput and reliability, can be operated without special ATEX requirements and/or installed in a non-ATEX equipped room. The air cycle cooler, for optimal energy utilization, is used to chill both the condenser and, indirectly, the lyophilizer shelves as well. The condenser operates as a cold oil resource during the freezing process.

The GEA CO₂ booster can reach shelf temperatures down to –50 °C and is suitable for a wide range of product freezing applications. The cooling system uses natural refrigerants (air and CO₂) and has a global warming potential (GWP) of 1 (equivalent to CO₂). In combination with the corresponding air cycle cooler, the LYOAIR^® system can reach –60 °C on the shelves and down to –90 °C on the condenser coils.

Carbon dioxide has a GWP of 1, which is considered to be the baseline figure or standard for comparison. If, for example, 1 kg of the hydrofluorocarbon (HFC) blend refrigerant R507 is expelled into the atmosphere and evaporates (becomes gaseous), this is equivalent to 3985 kg of CO₂ being released (Source: AR5: IPCC V, 2014).

Not only does the LYOAIR^® cooling system employ natural refrigerants that comply with current greenhouse gas regulations, it also benefits from the integration of highly efficient and economic third-party compressors. The combination of an air cycle system with a CO₂ booster offers a lower energy consumption system for freeze dryers compared with a regular air cycle system and provides the full range of temperatures required for effective operation.

Further benefits include the elimination of explosive or toxic natural gases, less vibration and quieter functionality. It’s also easy to maintain and significantly less expensive to run than liquid nitrogen alternatives. Tests have already shown that the system can run for 90,000 hours (approximately 10 years of continuous operation) without the need for a major overhaul. Furthermore, the LYOAIR^® system is retrofit-compatible with all GEA Lyophil freezer dryers.

From a business perspective, it’s been estimated that the annual operational costs of using liquid nitrogen is 10 times higher than using the newly developed LYOAIR^® system. As such, in terms of return on investment, the energy savings would result in a capital expenditure neutral situation in less than 5 years (not including service charges). Not only that, there’s the added benefit of not polluting the atmosphere and environment with fluorinated gases, which seep into the local ground water and can be extremely difficult to remove. For large-scale freeze dryers, we’ve calculated that up to 1000 tons of CO₂ equivalent can be saved per machine.