Ammonia / Glycol plant upgrade

Our client is Britain's largest producer of branded and private label dairy products, with a network of dairies and depots servicing customers throughout the country. Our clients site in Telford predominantly manufactures retail branded yogurt products, and made the decision to increase the site capacity from the current production capacity of 200 to 500 million pots per annum. This being achieved through upgrading and increasing existing production and storage capabilities.

The existing refrigeration system was designed to facilitate future expansion and the new additions / modifications provided a common ammonia / glycol system.

Seward Refrigeration Ltd were awarded the installation contract to upgrade the existing ammonia / glycol refrigeration system to serve the new project, including the installation of two heat pumps providing conditioned air in a high bay warehouse.

The scope of works included;

  • Installation of an additional BAC evaporative condenser, equipped with fan inverter drives, located adjacent to the existing unit.
  • Installation of a high-pressure liquid receiver installed at condenser level
  • The existing HP float removed and converted to high pressure liquid feed via modulating control valves supplied via the new liquid receiver.
  • An additional Grasso DUO compressor pack installed between the two existing Grasso RC compressors and piped into the common refrigeration circuit.
  • An additional 1200kw ammonia / glycol heat exchanger was added to the existing 2500kw surge vessel to provide cooling duty to the new cooling tunnel, despatch area and Repack area.
  • The interconnecting suction pipework between compressors and surge drums to operate at the same suction pressure
  • The existing Trend controls system was extended to facilitate the new equipment.
  • Standalone ventilation system, consisting of 2-off Lennox heat pump units / ducted system providing the required heating, cooling and fresh air for a high bay Warehouse.

General plant description

New cooling duty requirements;

Cooling tunnel  1500kw

Despatch area  90kw

Repack area     40kw

The existing ammonia / glycol, chilled water system, comprises of 2-off gravity fed ammonia surge drums, one provides chilled water and the second provides chilled glycol at -7°C. For this project the chilled water system remained as built, and the glycol system was increased in size by a further 1200 kW by fitting to the surge drum, an additional Alfa Laval heat exchanger providing glycol at -7°C/ -3°C. Provision was made for this additional plate to be fitted when the plant was originally designed so all the connections were in place to allow a relatively straightforward installation. Additional valves and safety valves were fitted as required.

Vapour from each of the 2 plate packs on the glycol system is drawn into a common suction header from which the original Grasso RC612E compressors along with a new Inverter driven, GEA Grasso Duo SPD MD 5A screw compressor. The new compressor provides an additional capacity of 1515 kW when operating with a suction pressure at -9°C and condensing at +32°C. Each compressor then discharges into a common discharge header which in turn is condensed in 2-off Baltimore evaporative condensers, the existing is rated at approximately 1900 kW and the new CXVE 539 (supplied and installed) provides 1877 kW when operating at +32°C within a wet bulb ambient of +21°C. There is also an additional glycol cooling circuit fitted to the condenser to provide a capacity of 394 kW of cooling for the new GEA duo compressor pack oil cooling circuit.

The new and existing condensers are piped together to provide condensed ammonia liquid which then flows into a new common high-pressure liquid receiver. Liquid from the new common receiver is fed to the existing chilled water surge drum via a Hansen MVP 32-7 motorised valve, ammonia is also fed to the glycol surge drum via a Hansen MVP 40-7. Both valves are controlled by level transmitters fitted to each surge drum vessel.

The GEA DUO compressor oil cooling is provided via a split cooling circuit in the new evaporative condenser. The circuit operates with a 28% mix of DTX coolflow, the pump provided is a Grundfoss NB40-125-142/ 5.5 kW, the flow rate is 12.73 L/s with a head at 22.5 mtrs, the DTX coolflow operating temperatures are +32°C/ +42°C.

Three Grundfoss NB100-315-334/ 30 kW pumps are provided for the primary DTX coolflow chilled glycol to feed the new PL500 cooling tunnel, Repack area and Despatch area. The pumps are set up to have two running with one standby, each pump provides 54.73 L/s with a head at 35.4 mtrs. The PL500 cooling tunnel is fed with DTX coolflow at -7°C, there are twenty evaporators installed within the tunnel at high level. The Re-pack area has two dual discharge evaporators installed within it for controlling the air temperature at +4°C, each cooler is supplied with DTX coolflow and each has a capacity rated at 20 kW, defrost is off cycle with the cooling closed off and the fans running for a set period of time. The Despatch area has three draw through evaporators installed within it for controlling the air temperature at +4°C, each cooler is supplied with DTX coolflow and each has a capacity rated at 30 kW, defrost is off cycle with the cooling closed off and the fans running for a set period of time.

High Bay Warehouse temperature conditioning system

The system provides an overall temperature throughout the high bay warehouse at 15°C by means of a displacement ventilation system. Conditioned air is discharged along the full length and below the 4 of the bottom tiers of racking and the resultant mixed air allowed to rise via buoyancy to the top of the room where it will be collected via return ducts and drawn back to the two Lennox air handling units. The 2-off Lennox heat pump units provide all required heating, cooling and fresh air for the Warehouse.


Photo Gallery – Installation of the High bay warehouse ventilation system:

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