PAHssion- Industrial efforts towards zero emissions of PAH

There are multiple reasons to measure emissions. One is to report correct numbers to authorities. Another is to use measurement data to optimize processes. Sometimes it is possible to use the same measurement methods to achieve both, but different approaches are often needed. The backdrop to the PAHssion project is the industry’s ambition of zero emissions. To reduce emissions to near zero, it is necessary to know when, where and how the pollutants form. Only then is it possible to adjust the process to hinder the formation. A challenge is that the lower the concentration is, the more difficult is it to measure it correctly. There are standardised methods to measure PAH in emissions. The motivation for the PAHssion project was however that the industry felt that results from standard measurements could not be used for process optimisation. Even when measurements were carried out in accordance with all available rules and standards, the engineers experienced that the results pointed in all directions at once. In the PAHssion project, 10 industrial partners and 4 research partners collaborate to meet this challenge. The industry has financed the project together with the Norwegian research council. The project has developed new strategies to measure PAH and more knowledge about how the PAH forms in different processes. The project have, among other things, made use of SINTSENSE – a sensor-based equipment developed by SINTEF. An important finding from the project is that the processes that forms PAH varies greatly, over long and short time periods. There can, for example, be fluctuations over minutes, hours, days, weeks, or months. There can also be significant differences between seasons. A way to follow the process variations with respect to emissions is to use sensors for emission monitoring which are able to catch all these fluctuations, even the fast ones. There are, however, no such sensors for PAH today. The work in PAHssion has shown that in some cases, it is possible to use volatile organic compounds (VOC) in the gas as a so-called proxy for PAH. In such cases, a photo-ionisation detector (PID) can be used to monitor how the concentration in the gas varies from second to second. These detectors are commercially available and are used today to measure other organic gases. In PAHssion, we have shown that it is possible to use them also for PAH. With SINTSENSE, we get signals from six different sensors simultaneously and one of these can be a PID. This is extra interesting for following own processes, because real-time signals can show which gas components are formed when. It is also possible to get the signals on a pc-screen and compare the variations of different gases and dust with other control parameters that tells something about the process. In a digitalised, industrial future, the signals from emission sensors will be integrated into the general monitoring and control systems. Several industrial measurements were carried out in PAHssion, and they have shown that PAH emissions from most of the industries are dominated by PAH in gas form, known as volatile PAH. The volatile PAH are included in an even larger group of compounds known as volatile organic compounds. They are formed and destroyed in much the same way as PAH in industrial processes. We have seen that it is often possible to use the VOCs as a proxy for PAH. It is not, however, always possible and must not, for example, be done when there is a lot of dust in the gas. The standard methods available to measure PAH are relatively expensive and labour intensive. Standard measurements are typically performed only a few (2-6) times a year. When the annual emissions are calculated based on only a few standard samples, it is not necessarily completely representative for processes that vary greatly. By using a PID as a complement to standard measurements, the industry can design measurement programs (for standard measurements) that better represent the real emissions throughout the year. Thereby, it is possible to improve the annual reports to authorities and simultaneously strive to stop the PAH from forming in the processes at all.

The value creation in the proposed project is threefold: 1) economic values through new services and products (realised by Nemko Norlab), abatement methods and prediction tools; 2) economic values through operational savings and cost efficiency of measurements (realised by all material producing partners); as well as 3) considerable non-economic gains in terms of health, safety and environmental values. In the short term, new measurement methods such as online sensors (similar to SintSense) and thermal desorption tube sampling are taken to market by Nemko Norlab. The sensorbased methods most notably through the recently launched Nemko Norlab Digital segment. These services are greatly anticipated by the other industrial partners but will also be offered to all other customers, nationally and internationally. A major value of the proposed project is arguably to allow the use of direct-reading, high-resolution measurement data to understand own emissions. Once the new services are available on the market, the industrial companies in the consortium will be able to use them to continuously increase their own expertise and optimise their processes to reduce emissions.

The material producers in the PAHssion consortium (i.e. the Norwegian silicon, ferroalloy, titantium dioxide and silicon carbide producers) use carbon materials as reductants, electrodes, lining materials etc. As a consequence, they emit polycyclic aromatic hydrocarbons (PAH) to a varying degree. These industries experience that current PAH measurement methodologies give extremely varying results. So much so, that the prevailing standards for industrial PAH sampling and analysis, can not be considered reliable. Hence, emission reporting, while executed in compliance with standards and regulations, does not aid the companies to understand or control their emissions. Due to the lacking credibility of the measurements, the monitoring activities fail to fulfil their ultimate goal: to reduce emissions. The core of the proposed project is the need for higher performance measurements. The development of such methods constitute the key innovation which will, in turn, enable further innovations in terms of process design. New methods for PAH emission monitoring and for testing new raw materials will result in new services offered on the market and improved guidance capability of laboratory subcontractors to the industry. It will also improve assessment of environmental footprints and limit associated costs for the industrial companies. Additionally, it will aid companies in selecting materials and design processes on the basis of anticipated emission behaviour. In total, this will create value in terms of new and improved measurement services, raw material selection, abatements methods, operational savings and new best practice guidelines. But most importantly, it will ensure that the industrial consortium partners can continue to operate in Norway.