Product category:
Gas monitoring and analysis
News Release from: Servomex | Subject: As Pontes 2700 installation
Edited by the Processingtalk Editorial
Team on 01 April 2005
Combustion monitoring cuts power station
emissions
Following a year-long trial, Spain's largest coal-fired power station has installed four advanced analysers to monitor post-combustion levels of oxygen and carbon monoxide
Following a year-long trial, Spain's largest coal-fired power station has installed four advanced analysers to monitor post-combustion levels of oxygen and carbon monoxide The result is a fine-tuned process that enjoys improved efficiency and reduced emissions
This article was originally published on Processingtalk on 3 Jul 2008 at 8.00am (UK)
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With a capacity of 1400MW, the As Pontes power station operated by Endesa is the country's largest coal-fired power station.
It burns vast amounts of coal to produce steam for its turbine generators.
As with any coal-fired power station, an excess of oxygen (air) above the stoichiometric quantity is required to achieve complete combustion.
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Insufficient oxygen results in more carbon monoxide being produced.
However, it is more common for too much air to be supplied, causing a significant reduction in combustion efficiency due to an increased loss of heat to the atmosphere, plus there is more oxygen available to combine with nitrogen and sulphur dioxide to produce undesirable emissions of nitrogen oxides and sulphur trioxide.
To further complicate matters, the optimum air-fuel ratio continually varies as a result of changes in the loading conditions, fuel composition and particle size, aging of the equipment and other process conditions.
Endesa was previously monitoring the level of oxygen in the post-combustion gases, but this does not give as accurate a picture as measuring oxygen and combustibles together at a single point.
These analysers had also suffered as a result of the high levels of dust and sulphur present.
The company therefore decided to install a trial 2700 analyser from Servomex that would monitor both oxygen and combustibles and allow continuous fine-tuning of the combustion process.
This analyser was fitted downstream of the economiser, so had to operate with a sample temperature in the region of 500C.
To cope with the extremely dusty conditions, a special double filter was specified, and the blowback facility on the analyser was used on a regular basis to maintain its performance.
Two different technologies are used within the 2700 sensor head.
Oxygen is measured using a zirconium oxide sensor, giving high accuracy and a fast response; carbon monoxide levels are monitored using a thick film calorimeter that gives a precision of +/-25ppm, with sufficient sensitivity and speed of response to enable the combustion process to be continuously fine-tuned.
Both of these technologies are highly reliable, non-depleting, and can operate for extended periods without requiring attention.
According to Servomex, thanks to the inherent reliability and auto-calibration facility, the analyser required no servicing whatsoever throughout the one-year trial.
Endesa was initially attracted to the 2700 analyser ability to monitor oxygen and carbon monoxide concurrently, but reliability and cost-of-ownership are also important.
As a result, the company is purchasing four analysers for use in relatively inaccessible locations - taking advantage of their ease of installation, commissioning, operation, plus minimal requirements for servicing.
Whereas the excess oxygen was previously measured at 3.8 per cent, using the 2700 analyser has enabled this figure to be reduced to 2.7 per cent, with a corresponding reduction in carbon monoxide emissions and an increase in combustion efficiency - and, therefore, profitability.
With the oxygen levels given on a typical application of this type, a fuel saving of about 0.75 per cent can be expected, so users find that the improved efficiency easily pays for the cost of the instrumentation upgrade.
As with the trial analyser, these instruments are being supplied through Instrumentacion Analytica, the Servomex distributor in Madrid.
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