Overcoming Feedstock Fluctuations
Published by Alfie Lloyd-Perks,
Editorial Assistant
World Cement,
Lars Jennissen, N+P Group, discusses the complexities of maintaining high-quality alternative fuel processing in the face of varying feedstock quality, emphasising the critical role of advanced data collection and processing technologies in overcoming these obstacles for the cement industry.
If you had the pleasure of visiting waste processing sites across different continents, you start to appreciate the work of alternative fuel (AF) processing. You can tell a lot of stories about this, especially around quality. Quite recently, I visited a few cement kilns that are in the 'Championship League' of fossil fuel substitution, with average rates well above 80% and weeks where no traditional fossil fuel was consumed. A significant proportion of that AF is what would be called solid recovered fuel (SRF), along with many other abbreviations used in the market. However, depending on where you are in the world, the quality definition of SRF can vary significantly.
The impact of feedstock quality
The SRF at these sites is often fantastic, primarily due to the excellent feedstocks available. If I were to ask you, as a reader, to guess which country I visited, I’m fairly certain you would guess correctly. Why? Because it is no secret that high-quality SRF feedstocks are typically found in countries with effective collection and sorting systems. Conversely, I could recount a visit where I questioned if the SRF was truly suitable for burning, leading me to notice unpleasant odours on my flight back home. The quality of SRF fluctuates by country, and I believe that as AF producers, we will need to prepare ourselves for more 'difficult' feedstocks, as higher-grade materials will inevitably find their way to other applications.
Challenges in maintaining quality
N+P's processing capacity spans several countries, providing invaluable experience in understanding how collection systems affect quality. Legislation also plays a role in the choices we make; for example, in the UK, the so-called water exemption for landfill tax creates a cost-effective way to dispose of high-moisture waste streams like paper mill rejects, whereas this legislation is not (ab)used in Germany or the Netherlands. There are numerous examples concerning recycling quotas or finding cheaper disposal methods for waste. The diverse qualities of waste pose significant challenges for AF-producing companies striving to ensure the right quality, especially when processing large volumes. The question arises: how do you maintain the production of high-grade main burner fuel amid these challenges?
Importance of effective data collection
First and foremost, effective data collection is essential, and it is crucial to ensure you get your data right. When I first encountered pelletised fuel 15 years ago, many people questioned, “Why is this not a product?” It certainly appeared to be a refined fuel. While that assumption held some truth, the chemistry of the material, especially concerning certain elements, was similar to that of SRF. Initially, data indicated that SRF was cleaner than pellets, which seemed paradoxical since the SRF undergoes further cleaning. It was later revealed that sampling pellets was far easier, leading to more accurate results and less variability.
Reevaluating sampling methodologies
If we revisit sampling methodologies and follow precise guidelines for quartering a sample, we may obtain slightly more accurate data. However, we inevitably lose very fine material that might contain heavy metals during the process. When everything is compressed into a pellet, this issue is largely mitigated. We have often grappled with this dilemma, but we can now effectively collect data from our suppliers by processing mono-streams and compiling our datasets based on these results. It is both amusing and frustrating to witness significant discrepancies, particularly when explaining to clients that their materials contain, for example, substantial amounts of PVC and chlorine, while their own measurements suggest minimal levels.
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Read the article online at: https://www.worldcement.com/special-reports/23122024/overcoming-feedstock-fluctuations/
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