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Experience of operating an older ammonia plant and the energy consumption.

Author(s) : GIGIEL A., EVANS J.

Summary

This paper presents results from a survey of a large cold store complex with a small amount of blast freezing. The survey specifically excluded measuring the cooling loads. The site had two ammonia refrigeration systems with two-stage screw compressors, one with a closed and one an open flash intercooler. The refrigerant was pumped to the evaporators at high level in the cold stores. Both plants had evaporative condensers. The plant had been gradually adapted to its present configuration. The Coefficient of System Performance (COSP defined as kW of electricity to extract 1 kW of cooling) of the two plants on the site if used as originally designed would have been 0.53 and 0.64. However, because of economising capital cost and a lack of maintenance, the efficiency of the plants has been reduced and they are currently operating at a COSP of 0.66 and 1.03. The reasons for the reduced efficiency were: wear in the compressors, inefficient operation at part load, inefficient defrost programs, reduced recirculation in some evaporators, inaccurate instruments, poorly optimised intermediate pressure, deterioration of insulation on refrigerant pipe work and vessels and hot gas valves leaking. The estimated cost of the extra energy consumed because of these faults was GBP 115,300 per annum (EUR 173,000) plus the unquantified cost of the energy due to faulty hot gas valves.

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Pages: 2007-2

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Details

  • Original title: Experience of operating an older ammonia plant and the energy consumption.
  • Record ID : 2007-2177
  • Languages: English
  • Subject: Figures, economy
  • Source: Ammonia Refrigeration Technology for Today and Tomorrow.
  • Publication date: 2007/04/19

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