Gas sensing
Increasing political action on Climate Change is prompting a new requirement for process operators to improve the accuracy and reliability of greenhouse gas (GHG) emissions monitoring. To meet this requirement, Stephane Canadas from UK gas analyser manufacturer Signal Group is urging the operators of combustion equipment, such as boilers and incinerators, to employ reference method analysers in either the measurement of GHGs or for the calibration of installed continuous emissions monitoring systems (CEMS) for carbon dioxide (CO2) and nitrous oxide (N2O). Amid increasing concern about the effects
results in global warming; so, increases in the concentration of GHGs in the atmosphere
G
enhance this process. CO2 is the best known GHG but others include methane (CH4), nitrous oxide and fluorinated gases such as
CFCs. GHGs differ in both their ability to absorb energy and how long they stay in the atmosphere. As a consequence, methane has a Global Warming Potential (GWP) of 28–36
times larger than CO2, N2O has a GWP 265–298 times that of CO2, and many fluorinated compounds have GWPs that can
be in the thousands or tens of thousands. The term ‘carbon emissions’, is generally
employed as a term that covers all GHG emissions. This is because different gases have different Global Warming Potential (GWP), which is a measure of how much energy the emissions of one ton of a gas will absorb over a given period of time, relative to the
emissions of one ton of CO2. Building on the Kyoto protocol of 1997, the
Paris Agreement in 2015 was the first legally binding global climate change commitment. It aimed to limit global warming increases to well below two degrees, and included a requirement to submit GHG reduction plans every five years.
HGs absorb and emit some of the energy radiated from Earth's surface. This absorption of energy
of Climate Change, governments around the world have been implementing further commitments to reduce GHG emissions. In the UK for example, the government announced a plan to cut carbon emissions by 78 per cent by 2035 (against 1990 levels), and President Biden has pledged to cut carbon emissions by 50 to 52 per cent below 2005 levels by the year 2030. These pledges come in advance of the UN Climate Change Conference (COP 26) which is scheduled to take place in Glasgow in November 2021. In the EU, Directive 2003/87/EC establishes
a scheme for GHG emission allowance trading within the Community. Under this scheme operators will be required to monitor
CO2 emissions from all types of combustion processes, including: boilers, burners, turbines, heaters, furnaces, incinerators, calciners, kilns, ovens, dryers, engines, fuel cells, chemical looping combustion units, flares, thermal or catalytic post-combustion units, and scrubbers (process emissions) and any other equipment or machinery that uses fuel, except that which is used for transportation purposes.
MONITOrING rEqUIrEMENTS Monitoring is of course an essential component of GHG emission allowance trading schemes. From a pollution control
perspective, in the past, it has not been necessary for the operators of most regulated industrial processes to monitor GHG emissions. However, if governments are to be able to measure and improve GHG emissions, it is clear that monitoring will be necessary. Evidence of moves in this direction is provided by communications from the Environment Agency in England urging the operators of Energy from Waste (EfW) plants
to calibrate their CEMS for flow rate, CO2 and N2O. This will involve meeting the requirements of EN 14181, which includes
carrying out a QAL 2 exercise, implementing QAL 3 measures and carrying out Annual Surveillance Tests (ASTs) thereafter. Calibration of the CEMS will require the monitoring contractor to assume a virtual Emission Limit Value (ELV) for each pollutant.
For CO2 a virtual ELV of 10 per cent will be suitable with a 95 per cent confidence interval
of 10 per cent. For N2O this will be a virtual ELV of 20 mg/m3
and a 95 per cent
confidence internal of 20 per cent. For some operators, their installed CEMS
will already have GHG monitoring capability – analysers employing FTIR, for example, are able to
monitor CH4, CO2 and N2O. FTIR is stated to be the second preference according to EN TS
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June 2021 Instrumentation Monthly
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