Condenser Clean Removes More Than 300kg of Scale and Silt

Condenser Clean increases waste to energy output by 3.1mw/hr

The waste-to-energy plant of this UK-based company burns rubbish from the area to generate up to 12.8MW/Hr of electricity for the use of the plant and the local community. Output had fallen to 9.3MW/Hr because of the reduced efficiency of a dual steam condenser. Tube Tech cleaned the condenser in two halves, with one half remaining on line so that generation could continue at a reduced level. 320Kg of scale and other deposition was removed during the clean, resulting in a return of the generator to 12.4MW/Hr output.

The Challenge

The client company in the Midlands area of the UK operates a dedicated waste-to-energy plant, which burns up to 220,000 tons of rubbish from the area per annum in its environmentally regulated incinerators, to generate up to 12.8MW/Hr of electricity for use in the plant and the local community.
Around 2.5-3MW/Hr of the generator’s output is used for in-house equipment and processes. It also exports 2.2 million therms of heat per year for process and space heating in nearby factories.
Tube Tech was called in because the performance of the plant’s dual steam condenser had fallen off, resulting in a significant loss of generator output – down to 9.3MW/Hr. The condenser creates a vacuum that helps drive the generator turbine.
As the condenser’s efficiency fell, so did the vacuum is was able to achieve.
The dual condenser is 5.5 metres long, 3 metres from the floor and contains 2,328 tubes of 0.902″ internal diameter.
Apart from normal scaling, it was suspected that the condenser had also become partially blocked by the pieces of plastic screens from a cooling tower, which had passed through the fans into the cooling ponds, past other filters that were temporarily out of place and then in the condenser.
The screens had become blocked with airborne debris and were being replaced.
Over time, they had become brittle and tended to break up on removal.
In addition, fine airborne particles of silt from the nearby river were able to pass through all screening and filtration stages and enter the cooling water.
Substantial quantities of this silt were to be found in the condenser when it was cleaned.

The Solution

The Tube Tech team faced an unusual challenge in having to clean each half of the condenser while the other half remained on-line at operating temperature, so that some power generation could be maintained.

This was preferred by the National Grid, as it avoids having to re-synchronise the plant’s output when it comes back online.
Over 300Kg of scale and river silt deposit were flushed out of the condenser tubes, while the plastic packings were removed without difficulty, thanks to the special darTT that Tube Tech fired down each tube to clean and clear them.

Client Comment

“The Tube Tech team did a really good job, without a doubt; they were conscientious and worked hard. I had never seen the DarTTs that were used to clean the tubes before, but they certainly were very effective. The team completed the job faster than I expected, especially considering the size of the condenser doors and the work involved in their removal. Tube Tech worked so quickly, our people had started re-attaching the first door while we were still getting ready to remove the second one. The Tube Tech team took an awful lot of scale out and cleaned it up so we could dispose of it. When we have to clean the condenser again, I will certainly be in touch with Tube Tech.”

Benefit

The condenser was cleaned on-line, one half at a time, thus allowing the plant to continue operating and maintain its electricity generating revenue of approx. £10,000 per day.

Following the clean, the generator’s output has gone from 9.3 to 12.4MW/Hr and is the best performance it has yielded for some considerable time. As a result, Tube Tech expects to be recalled to carry out the same work again during the next outage.