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SCR Retrofit

Electric Ireland
Customer: Moneypoint (Ireland)

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"SCR Retrofit"

To combat the potentially adverse effects of Air-Preheater blockage resulting from Ammonia Bisulphate build up in the heat exchanger Baskets, Power System Services calculated the temperature profile through the heater and established the exact region where this build up may possibly occur. Once the location of this plate surface temperature region, was established, engineered solutions were investigated to evaluate the most cost effective and reliable solution to this potential blockage issue.

Key considerations for design evaluation were:

  • Ensuring the ammonia bisulphate region is contained within one single basket layer.
  • Ensuring that the elements within the basket layer can be cleared easily and that the steel is resistant to aggressive precipitant build up material.
  • Ensure that cleaning devices are reliable and can clean this layer.
  • Ensure that the rotor modifications do not affect the overall performance of the heater, structurally and performance wise.

The Solution:

  • Replace the existing 3 layer system with a 2 layer system encapsulating the AB region in a deeper cold end basket as illustrated. The cold End Basket elements are coated in enamel to make them resistant to acid attack and more cleanable, because they have a smoother surface.
  • Altering the arrangement meant supporting all layers from the bottom. This required reinforcement of the bottom support grid once all old baskets were removed and the removal of intermediate basket support bars.
  • Overhauling of the existing combined HP/ Steam cleaning soot blowers top and bottom to ensure that they clean the baskets well.
  • Overhaul sealing system to optimise cross sector leakage.

Units 3 and 2 works completed. Guaranteed temperature outputs with 1 degree accuracy, pressure drop maintained.

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