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Power Industry Process News
News Release from: Elga Process Water | Subject: MODI at St Austell
Edited by the Processingtalk Editorial
Team on 27 September 2007
Power station gets de-ionised water
supply
Elga Process Water has again assisted a power station, Indian Queens near St Austell, by providing on site deionised water from an ion exchange system, and dealing with all regeneration off-site
Elga Process Water has assisted a power station, who had no consent to discharge liquid effluents, to create low cost on-site deionised water International Power is a growing, independent power generation company with 18GW net ownership of capacity worldwide (30GW gross)
This article was originally published on Processingtalk on 17 Dec 2002 at 8.00am (UK)
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Last year, it acquired the 140MW Indian Queens oil fired open cycle gas turbine (OCGT) station in St Austell, Cornwall, from AES.
Indian Queens Power Station was constructed by John Brown Engineering in 1996 and, under the terms of the integrated pollution control application, it operates as a peak lopping station, which means that it runs only infrequently, and predominantly in the winter months when demand is high.
In order to suppress NOx emissions, water is sprayed directly into the burner to reduce the flame temperature.
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This water evaporates leaving behind any dissolved salts which deposit in the burner and need to be removed regularly.
In order to avoid such problems, Indian Queens uses deionised water of 0.1uS/cm conductivity and silica less than 20ppb, which is very low in dissolved salts.
During the summer, the station uses about 40m3 per day of deionised water, but in winter the demand rises to about 170m3/day.
To produce this high quality water, an ion exchange plant with its associated regenerant chemicals and effluent discharge is required.
Back in 1996, Indian Queens did not have a Consent to Discharge and, since the station would operate with a very low utilisation, its then owners, Indian Queens Power, opted to use a mobile rental deionisation system with off-site regeneration and no on-site effluent discharge.
The ten year rental contract allowed Indian Queens Power to obtain deionised water from any source available during the summer months.
Water costs were reviewed every year and, when the economics moved in favour of on-site regeneration, the company purchased a 9m3/h Elga Process Water Rapide deioniser.
The Rapide uses state-of-the-art ion exchange technology, with a highly efficient regeneration process that produces such a small quantity of effluent that it can be economically tankered off site to a merchant waste disposal facility.
During the winter months, with the higher demand for water, this becomes un-economical and the station reverts to the mobile rental solution.
The Elga Process Water plant had performed well, and after sales service had ensured that it was also trouble free, so when the rental contract was due for renewal, Elga Process Water was given a chance to bid.
Elga Process Water operates a fleet of Aquamove mobile trailer mounted treatment plants that includes MODI deionisation units.
These provide two streams of cation, anion and mixed bed ion exchange vessels housed in custom built, 45foot trailers together with automated controls, remote telemetry and all the necessary safety equipment.
Each MODI trailer is capable of producing in excess of 150m3/h of high purity water - more than enough for the Indian Queens requirement.
Once exhausted the complete trailer is returned to the Elga Process Water Stoke-on-Trent facility for regeneration, which means zero discharge on site and no problems of handling or disposal of regenerant chemicals.
But the MODI trailers are intended mainly for emergencies or planned maintenance shutdowns and are an expensive option for long term hire.
The Elga Process Water Aquamove Team carried out a detailed review of the Indian Queens site and concluded that, rather than a trailer-mounted mobile unit, a lower cost option would be to install a custom designed 30m3/h containerised deionisation plant.
They proposed two 20foot ISO containers each fitted out with a cation exchanger, two anion exchangers and a mixed bed polisher.
One container is also equipped with the controls, quality monitors and remote monitoring equipment needed for both streams.
Rather than shipping the complete unit back to Elga Process Water for regeneration when the resins are exhausted, the resin vessels are simply exchanged for regenerated ones by the Aquamove service team.
Each containerised unit will treat about 1200m3 of mains water between regenerations; enough for a fortnight of use at average station generating capacity.
This proposal offered a big saving by comparison with mobile trailers and International Power signed up to a 5-year contract.
Unfortunately the order came too late for Elga Process Water to build, deliver and commission the new containerised plant in time.
So as an alternative, for the first year of the of the contract, Elga provided a MODI Trailer at the same price, ensuring that the station water supply was secured without affecting the economic forecasts, and all with the level of service that International Power has come to expect from Elga Process Water.
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