Biomass fuel feed – Avoiding failure

If you are currently operating or developing a biomass energy plant or gasification facility, then you’ll appreciate the importance of a reliable fuel feed and reception solution, to ensure long term plant viability and performance.

The same is true whether you are burning refuse derived fuels such as SRF, favoured in the cement sector, or RDF, and any number of alternative fuels from Municipal Solid Waste to Distiller’s Dried Spent Grain.

That said, the industry is littered with plant failures and facilities that simply haven’t achieved predicted energy outputs precisely because of fuel handling and storage issues. Why?

• repeated interruptions in the fuel feed prevent the plant reaching peak efficiency or
• excessive cost of unplanned manual intervention and troubleshooting, required to rectify issues, destroys the financial foundations and investment opportunity for the project.

Not only is this hugely costly but some plants may never reach their full potential or overrun extensively in time and cost just to get them operating at all.

The fuels we are talking about all have similar characteristics. They tend to be sticky, abrasive and cohesive with a tendency to compact and bridge. ‘Buyer Beware’ should be at the forefront of your thinking when considering a solution for your project as these properties can easily disrupt storage and conveying systems if the design is defective, resulting in poor or erratic material flow, with stagnant product and periods of prolonged outage.

Reception systems, storage and discharge, screening, reclaim conveyors, plus weighing and dosing systems, are all elements that need to work together seamlessly and for the life of the facility, twenty to twenty five years is typical.

So a full understanding of the handling and flow characteristics of the material involved becomes important, with a direct bearing on the engineering solution and long term plant reliability. Important considerations are:

• Particle size
• mass flow properties
• density variations
• moisture content
• compressibility
• engineering partner

Specialised in bulk material handling for more than 60 years Saxlund’s design approach focusses on activated surfaces and ‘first in, first out’ design principles. This limits the opportunity for fuel to degrade in the system, ensuring a continuous uninterrupted flow of product 24/7.

Today solutions are deployed across hundreds of sites in Northern Europe. Of the twenty or so biomass energy projects currently under construction in the UK, 13 have specified Saxlund fuel handling solutions incorporating either Saxlund Push Floor or Sliding Frame silos for fuel storage and discharge.

Bouygues Energies & Services, the company responsible for the engineering and construction of the UK’s largest waste-to-energy gasification plant currently underway at Hoddesdon in Hertfordshire, is just one example.

Plant longevity is another key factor. Slough Heat & Power, now owned and operated by SSE, and one of the UK’s largest dedicated biomass fired Combined Heat and Power (CHP) plants, for example has been operating since 2003 with Saxlund Push Floors feeding waste wood and recently installed a third Saxlund Push Floor fuel handling solution to feed additional combustion capacity with a 720m3 fuel reception area with live storage.

With over three years successful operation already completed RWE’s Markinch biomass power station in Fife is one of the largest of its type in the UK, burning over 450,000 tonnes of sustainable waste wood each year. Again the fuel storage and handling solution, developed by Saxlund, is a crucial element, designed to ensure uninterrupted operation 24/7. 

As with all these projects the efficiency of the combustion process and energy conversion is clearly where much of the industry’s science and engineering is currently focussed, and rightly so. But a consistent uninterrupted fuel feed, when the material is typically sticky and difficult to handle, is just as crucial. Choosing the right engineering partner, plus a clear understanding of the material characteristics you are working with, will help to deliver maximum plant uptime, better reliability and improved confidence for all stakeholders.