For more than 15 years, Ranheat has been designing, manufacturing, and operating ceramic filter systems for industrial biomass boilers. First developed in-house around 2010–2012 by Chris Franklin, with support from Alexander Franklin while studying Physics at King’s College London, ceramic filters have become the cornerstone of Ranheat’s emissions control strategy.
Ceramic filters use arrays of precision-made ceramic candle elements suspended vertically. Dirty flue gases pass through the elements, where fine particulates are trapped. Periodically, compressed air pulses clean the filter elements, dislodging ash into a hopper or conveying system. This design delivers:
Ultra-low particulate emissions: typically <10 mg/Nm³, often 1–2 mg/Nm³.
High temperature tolerance: stable up to 400–450°C, tested in applications up to 600°C.
Long service life: many Ranheat customers are still running their original filter sets 15 years later, with only occasional element replacements.
The first generation of Ranheat ceramic filters entered service more than a decade ago. Since then, control systems have been refined to optimise cleaning cycles, manage pressure differential, and maintain stable combustion conditions downstream of the boiler. A significant upgrade was introduced around 2019–2020.
Earlier systems: fully functional, but can now benefit from a retrofit upgrade to the newer control strategy.
Current systems: delivered with the latest software and hardware, ensuring efficiency and reliability.
This approach reflects Ranheat’s philosophy: continuous improvement, but always in a way that can be retrofitted. Customers are never left behind.
Across the UK and Europe, Ranheat ceramic filters have consistently proven themselves:
Filters installed over a decade ago remain in operation today.
Most failures are linked not to design, but to poor compressed air quality (oil/water contamination) or outdoor units not maintained against weather. Where correctly maintained, lifetimes are measured in decades.
Ranheat filters are deployed both on our own MSU biomass boiler range and as retrofits to competitor systems needing to meet modern emissions standards.
Cyclones / multicyclones: simple and low cost, but only reduce dust to ~60 mg/Nm³—insufficient for current and future limits.
Electrostatic precipitators (ESPs): compliant and effective, but disproportionately expensive at scales below 4–6 MW.
Bag filters: widely used elsewhere, but limited to ~180–200°C continuous service; unsuitable for many biomass applications.
Ceramic filters: ideal for 150 kW to ~4 MW scale, modular above that, with lower costs than ESPs and greater robustness than bag filters.
Ceramic filters are not just high-performing—they are the right tool for a changing regulatory environment. The Medium Combustion Plant Directive (MCPD) and UK EPR Technical Note 5/1(18) make clear that emission limits are tightening and will be applied retrospectively across Europe, the UK, and Ireland. Systems installed before 2019 may need retrofitting to meet the 2025 and 2030 deadlines. Ranheat has already delivered multiple retrofit packages and is positioned to support both our own boilers and third-party systems.
Manufacturer: We design and manufacture our own ceramic filters in-house.
Integration: Optimised with Ranheat biomass boilers, but adaptable to competitor systems.
Longevity: Proven 15+ years of real-world operation.
Retrofit-ready: Improvements in controls and design can be applied to earlier installations.
Fifteen years of experience confirms it: ceramic filters are the most effective, reliable, and sustainable emissions control solution for small-to-mid-scale biomass boilers. At Ranheat, we’re proud of the systems already out there, many still on their original filter sets, and we continue to refine, upgrade, and retrofit to ensure every customer remains compliant for the decades ahead.
