Trans-critical CO2 system pushing boundaries for Meat World

Trans-critical CO2 system pushing boundaries for Meat World

By Johann Jooste of Metraclark
The new Meat World production facility in Springs boasts an energy efficient, state-of-the-art trans-critical CO2 refrigeration plant that will raise the technology standard in South Africa.

Other than the production facility in Springs, Meat World also has a total of 15 stores. Meat World CEO, Angelino Pereira, has worked with the Coolcare (part of the Brasco Group) team for 24 years and they look after the refrigeration plants of the majority of the stores. So, when the time came to upgrade the production facility, Coolcare was the natural choice.

In 2017, the experienced Coolcare team received the plans for the new Meat World production facility that was going to be erected in the Springs area for which they needed to supply energy efficient refrigeration equipment at the client’s request.

System requirements

The new facility employs an impressive 370 staff, almost doubling the 180 in number at the previous facility. It also drastically increased in floor size, from 3 000m2 to 7 000m2.

Coolcare contacted Metraclark to brainstorm ideas to supply technologically advanced equipment that would save their client energy, and deliver the refrigeration specifications initially set out for this massive facility. The Metraclark engineering team worked off the floor plans supplied along with all the daily meat production figures and calculated all the heat load requirements for each room.

The heat load for the system consisted of amongst others between 80 and
160 tonnes of fresh meat as well as 1 000 tonnes of frozen meat passing through the facility daily. This all added up to a combined heat load of 840kW for both the medium and low temperature applications. Additionally, the client required that the system could supply 10 000 litres of hot water per hour as well as 2 000 litres of chilled water for various factory and processing functions.

Considering the requirement that the system be state-of-the-art and energy efficient, a standard synthetic refrigerant refrigeration system was foregone in lieu of a CO2 system, incorporating a trans-critical booster design. Due to the high ambient temperatures often experienced in these parts of South Africa, it was vital that this system could operate trans-critically as well as sub-critically.

The plant was commissioned in May 2018 and the new facility was fully moved over and operational by 15 November last year.

System description

Coolcare and the knowledgeable Metraclark engineering team worked very closely together and proposed the idea of going ‘green’ with natural refrigerants to Pereira. Metraclark, along with CO2 system specialists from SCM Frigo Italy, explained in detail how the CO2 trans-critical booster system offered works, along with all its many advantages to the client, and he was sold on the idea based on the facts presented.

“We didn’t reinvent the wheel,” said Jooste. “We simply worked with one of the best international CO2 manufacturers, SCM Frigo in Italy, who has produced more than 4 000 CO2 systems to date into different countries around the world. Going forward the SCM Italian and South African teams will work closely together to manufacture CO2 equipment on the same international standards locally in South Africa.”

The contractor even went to Italy to inspect the equipment themselves and to see how it works before bringing it over.

MeatW00 06Coolcare’s drawing of the temperature requirements for this site. Credit: Coolcare

The final equipment offered and installed for the CO2 system were as follows:

  • Two outdoor multiple compressor rack plant rooms each handling half of the overall load to keep the system balanced. The following are specifications for each plant room:
  • Racks capable of delivering 431kW each to serve both medium and low temperature applications.
  • Each rack consists of eight compressors all equipped with service valves on the suction, discharge and oil side to allow for isolation if required, as well as pressure relief valves.
  • Four Bitzer compressors for the medium temperature users at a suction temperature of -5°C and the lead compressor fitted with a Danfoss Variable Speed Drive (231 kW).
  • Four Bitzer compressors for the low temperature users at a suction temperature of -25°C and the lead compressor fitted with a Danfoss Variable Speed Drive (200 kW).
  • Two Bitzer parallel compression compressors with the lead compressor fitted with a Danfoss Variable Speed Drive (VSD) and is installed to directly compress the flash gas present in the liquid receiver. These parallel compression compressors increase the overall efficiency of the system (31kW).
  • One Danfoss vapour multi ejector which adapts the capacity requirements and handles three different suction groups in one device.
  • Danfoss CO2 rack controller for the entire system as well as a dedicated rack controller for the parallel compressors.
  • Oil management system with electronic oil level regulators installed on all the compressors.
  • Danfoss high pressure valve which regulates the pressure in the gas cooler to maintain the optimum coefficient of performance (COP) for the system during trans-critical operation as well as a degree of sub-cooling during subcritical operation.
  • Danfoss medium pressure valve which maintains a constant pressure in the liquid receiver.
  • Plate Heat Exchanger mounted on the common discharge line for the supply of 5 000 litres per hour of hot water at 60°C to the facility.
  • A cold-water supply of 2 000 litres per hour at 7°C.
  • Gas detection system in the plant rooms with audible and visible alarms.
  • Two gas coolers installed with EC fans that each deliver a capacity of 684kW.
  • Various evaporators for each room in the facility making use of hot gas defrost where applicable.
  • Only one third of the low temperature load on each rack can be defrosted at any given time to ensure there is enough heat generated.
  • Electronic expansion valves were installed on all the evaporator coils.
  • Gas detectors are also installed near the bottom of each room with audible and visual alarms.
    Valve stations are installed at each evaporator coil in order to facilitate maintenance with an additional bypass valve to ensure any liquid that gets trapped can boil off again.
  • Redundancy was built into the system to ensure they wouldn’t experience any downtime when anything went wrong with the refrigeration plant.

Raising the standard

Coolcare had the continuous technical support of the experts from both SCM Frigo in Italy and Metraclark in South Africa throughout the entire process to ensure a successful installation and functioning plant. Many other suppliers of components were also present on site to provide additional assistance and support where required.

Energy savings calculation software was used to perform a comparison between a conventional synthetic refrigerant R404A system and the new CO2 system proposed and theoretically showed an average savings on the CO2 system of 13%. This project was a collaborative effort and boasts engineering excellence with all the latest technologies in CO2 available on the market and certainly sets a benchmark for the refrigeration industry.


Coolcare is on 24-hour standby for Meat World Springs. They also do a thorough check and basic plant service once a month.

A happy client

The previous Meat World facility had a multiplex refrigeration system with synthetic refrigerants. The new CO2


 plant is currently realising energy savings of about 30% compared to the old plant, which the client is very happy about. The topping up of refrigerants is also significantly cheaper than the old system.

“The system is working very well and I have no complaints,” says Pereira.

“If you’re going to do something, do it properly,” adds Pereira. “You have to keep up standards and work on uplifting the meat industry.” Meat World places very high value on quality and not only are their own quality control processes very stringent, they also expect their entire supply chain to deliver to the same standard. It is no surprise then that they held the construction team to the same standard, expecting only the best. No shortcuts were taken.

CO2 booster systems explained

Booster systems are systems with two temperature levels; namely medium and low. This is due to the fluctuation in ambient temperature. When the ambient temperature is below the critical temperature, the system operates as a subcritical system, however, when the ambient rises to above critical temperature, the system operates as a trans critical system by using the condenser as a gas cooler.

The booster system incorporates both medium and low temperature capabilities in a single unit, as the compressors selected can be used for a wide range of refrigeration loads. It saves space and allows the system to run optimally and can accommodate all the design requirements in one system.

What makes the booster systems different?

  • There is a special condenser that works as a gas cooler under higher ambient conditions (trans-critical operation)
  • The compressors for both medium and low temperature applications need to be selected carefully in order to ensure optimal capacity control during partial load conditions.
  • The same refrigerant is moving between the medium and low temperature compressors. The low temperature compressors discharge into the suction line of the medium temperature compressors, the low temp compressors act as a booster to the medium temperature compressors.
  • The condenser design is optimised for the best performance for both subcritical and trans-critical stages.
  • You can obtain hot water and cold water recovery from the same system and during the trans-critical phase the discharge temperatures are higher, which provides more potential for heat reclaim.

    Click here to read the issue of Cold Link Africa


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