EMISSIONS MONITORING: EUROPEAN SURVEY OF OPINIONS ON MONITORING USING THE SRM (EN 14791) OR PORTABLE INSTRUMENTAL TECHNIQUES
SO2
With increasingly strict emissions limits being brought in across many industries, there is some debate over whether the existing Standard Reference Method for SO2
(EN 14791) is capable of reliably
detecting these lower levels. Some would advocate moving to longer EN 14791 sampling times to increase sensitivity whilst others would propose moving to portable instrumental techniques capable of providing the increased sensitivity without needing to increase sampling times, with the added benefi t of real-time data. However, many of these portable instrumental techniques require the sample to be dried before measurement (conditioned sampling), and here more data is needed to better characterise conditioned sampling at low SO2
levels so the community can fully understand
this capability. A new European metrology project called ‘Sulf–Norm’ aims to address such sampling questions so that the emissions community have the data they need to make fully informed decisions on the future of SO2
monitoring.
Here we report one of the fi rst activities under Sulf-Norm which has been to conduct a survey to determine industry preferences and perception of the pros and cons of SO2
monitoring using
EN 14791 or portable instruments. Fifty seven questionnaires were completed online via the Source Testing Association (STA) server, with participation from across Europe. Overall, portable instrumentation was the preferred method in most countries, although concerns were raised regarding species cross-interference and losses within the conditioning system. Issues were raised across the survey regarding the logistics of glassware on site, the sample-train, and user-error in leak testing.
Introduction
With a growing global focus on the effects of air pollution and its environmental impact, there is an ongoing effort not only to reduce current emission limits, but also to ensure that decreased emissions are measured with continued confi dence and accuracy.
The serious health risks associated with air pollution continue to impact heavily on the populations of all European countries, alongside the fi nancial burden that this then transfers to their healthcare systems and governments. A recent United Nations report suggested that over 40,000 premature deaths in the UK per
year were the direct result of poor air quality, with many of these in the country’s largest and most densely populated cities1
.
The EU is tackling these issues in terms of emission limits that must be adopted and enforced by all member states. This is being supported at CEN by the publication of standards that provide emission measurement methods that are passed into, or referred to in member state legislation; by convention such methods are referred to as Standard Reference Methods (SRMs). The role of the SRM has become two-fold: to periodically demonstrate compliance with emission limits and to calibrate, via parallel measurements, in-situ permanently installed instrumentation (referred to as Automated Measurement Systems - AMSs). Alongside the regular compliance testing, these AMSs are then used for year-round, continuous monitoring of emissions, as is required on all plants with >100MW capacity. Fundamentally, whether by compliance or calibration, the monitoring framework is underpinned by the capability of the current suite of SRMs.
In 2013, the Industrial Emissions Directive (IED)2 brought in stricter
emission limits for key pollutants, and the European Commission estimated that successful implementation of the IED would reduce premature deaths in Europe by approximately 13 000 p.a. With Best Available Techniques Conclusions documents bringing in even stricter
emission limits across a number of industrial processes the emission monitoring community has started to discuss whether the capability of the existing suite of SRMs is suffi cient to enforce such limits.
With respect to SO2 the existing SRM - described in EN 147913
- is based on extracting a sample from the stack and passing it through impingers fi lled with H2
O2(aq) , where the SO2 is dissolved as
sulphate for subsequent analysis off-line in an analytical laboratory, most commonly by ion chromatography. In principle, the sensitivity can be increased by sampling for longer periods of time (increasing the concentration of collected sulphate) and hence, this could be the solution to enforcing increasingly stringent emission limits. Alternatively, the community could move to using portable instrumental techniques (often optical in nature) that could provide increased sensitivity without increasing run times with the added advantage of real-time data. However, many of these techniques, in contrast to the SRM, require the extracted stack gas to be dried (conditioned) before being passed through the analyser.
For the emissions community to take informed decisions regarding the future approach to emissions monitoring, data are needed that show how far the SO2
SRM can go in enforcing increasingly
stringent emissions limits and if portable instrumental techniques offer a viable alternative. With respect to the latter, the European
IET November / December 2018
www.envirotech-online.com
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