Gas detection B
MULTIPLEXED GAS ANALYSERS CAN LOWER COSTS
y the time a CEMS measures a process stream for compliance, the process work is done, and the analysers are simply providing proof that the process is complying with its permit. However, the efficiency with which that compliance is achieved can be substantially improved by monitoring at earlier stages in the process stream. This principle applies to almost all regulated processes with emissions to air, and for a variety of measurement parameters. For the purposes of this article we will take a closer look at thermal oxidation processes such as VOC abatement and incineration. Incineration is a widely adopted method for dealing with materials such as municipal waste, sewage sludge, clinical and hazardous waste, and animal by-products. The advantages of incineration over other waste disposal methods include significant volume reduction, hazardous material neutralisation and energy recovery. However, the process of incineration converts much of the solid waste into gases, so tight regulatory limits apply to air emissions. Under the Industrial Emissions Directive (IED) incinerators are normally required to continuously monitor emissions of carbon monoxide (CO), hydrogen chloride (HCl), hydrogen fluoride (HF,) nitrogen oxides (NOx), sulphur dioxide (SO₂), total organic carbon (TOC) and total particulate matter. Under certain circumstances, continuous monitoring of HCl, HF and SO₂ may not be required, and periodic monitoring may be applicable. The specific requirements for continuous or periodic monitoring are detailed in a site’s EPR (Environmental Permitting Regulations) permit. The permit also specifies periodic monitoring frequencies for dioxins and furans, dioxin-like PCBs (polychlorinated biphenyls), heavy metals and poly aromatic hydrocarbons (PAHs).
Following the withdrawal of the UK from the EU, the requirements of the IED have been maintained in UK law through the Environmental Permitting Regulations.
Seeking to minimise the impact of pollution on people’s health and the environment by reducing
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Just as a puppy is not just for Christmas, a gas analyser is not just for regulatory compliance. Process managers generally install a continuous emissions monitoring system (CEMS) because they have to, by law. In the following article, James Clements, MD at Signal Group, explains how businesses can extract maximum value from
an investment in gas analysis. Using total organic carbon (TOC) measurements at thermal processes as an example, he will argue that the same analysers can also be utilised for process control and for checking the performance of abatement equipment.
harmful industrial and intensive livestock emissions across the EU, the revised Industrial and Livestock Rearing Emissions Directive (Directive 2010/75/ EU or ‘IED 2.0’) entered into force on 4 August 2024. A key feature of IED 2.0 is the mandate for national authorities to set Emissions Limit Values (ELVs) at the “strictest achievable” level within the BAT-AEL range for a specific installation, unless the operator demonstrates that this is disproportionately costly. As a consequence, ELVs will become tighter.
THERMAL OXIDATION
Incinerators employ high temperatures to break down complex organic chemicals into simpler forms - ideally water and carbon dioxide. The measurement of TOC emissions is necessary, not just to demonstrate compliance with the site’s permit, but also to help to identify incomplete combustion, which reduces efficiency and increases the risk of non-compliance. The incomplete combustion of some materials, such as plastics, can also result in the production of toxic gases, which emphasises the need for monitoring and feedback control. Nitrogen oxides (NOx) are worthy of mention in this context because nitrogen and oxygen are abundant in air but do not react in ambient
conditions. At higher temperatures, the gases react to form nitrogen oxide (NO) and nitrogen dioxide (NO₂), which have serious health and environmental effects, and are therefore tightly regulated. There is a direct connection between combustion process temperature and NOx emissions, so Signal supplies NOx analysers to inform process control. Offering higher levels of accuracy, Chemiluminescence is the preferred measurement method for development engineers at manufacturer laboratories working on new technologies to reduce NOx emissions in the combustion of fossil fuels. For regulatory compliance monitoring, NDIR (Non-Dispersive Infrared) is less costly and more commonly employed. Process managers seek to avoid incomplete combustion by optimising temperature, residence time and the air/fuel mixture. This process is informed by the continuous measurement of parameters such as oxygen, carbon monoxide and VOCs.
VOC ABATEMENT
Thermal oxidation is generally more effective at higher temperatures and with longer residency times, but both of these involve a higher energy requirement, increasing costs and reducing
January 2026 Instrumentation Monthly
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