Emissions Analyser Used for Process Control

A Gasmet FTIR multiparameter emissions monitor at Thetford power station (UK) is being used to demonstrate that the plant is performing within the conditions of its environmental permit. However, the data from the analyser, which was supplied by Gasmet’s UK distributor Quantitech, also performs a vitally important role in helping to manage the plant. “Individual gas readings are displayed in almost real-time in the control room,” says Plant Manager Andrew Corbyn, “which enables our staff to respond quickly to the changes resulting from variations in our feedstock. This ability to continually adjust the process ensures that we operate the plant efficiently; generating the maximum amount of renewable energy whilst maintaining a good clean burn.”                                                                              

Thetford Power Station operates under an environmental permit and as such the plant has to provide the Environment Agency with continuous monitoring data including half hour and daily averages for HCl, SO2 and TOC (total organic compounds). Monitoring data for CO, NOx and dust are also reported to the Agency.

Thetford operates a second Gasmet FTIR analyser to ensure that there is no possibility of expensive downtime. EPR Group Environmental Manager Kevin Williams says: “We originally purchased the portable Gasmet DX4000 analysers as a an emergency back-up unit, but the core measurement components of a DX4000 are exactly the same as the Gasmet CEMS, so it made sense to run both analysers simultaneously so that we always had a ‘hot’ back-up.”

Gasmet FTIR technology was chosen for the Thetford plant because of its ability to monitor multiple gases simultaneously. Operations Team Leader Richard Bloomfield says: “The system has performed very well, with very little maintenance required. Zero point calibration with nitrogen (background) just takes a few minutes each day and is fully automated. Water vapour calibration is conducted at least once per year, but under normal circumstances no other calibration is necessary.”

Richard says “The Gasmet analysers are our eyes and ears; providing us with almost real-time information on conditions inside the combustion chamber. We have a display in the control room that provides recent trends in addition to the live data, so that we can take steps to ensure optimal combustion efficiency, whilst maintaining compliance with our emission limits.”

There are a number of ‘tools’ with which the combustion process can be managed. For example, it is possible to adjust the feed rate, the distribution on the grate, the grate speed and air flow from below (primary air) and from above (secondary air).