Wood Chip Boiler

Due to the growing awareness of the importance of environmental protection and preservation, efficient and sustainable wood waste management has become critical in the woodworking industry. In this vein, wood chip boiler systems are a promising solution as they offer a powerful means of converting wood waste into valuable fuel while minimising the environmental impact.

At Ranheat, we specialise in wood chip heating systems and designing, manufacturing and installing wood chip boilers engineered for maximum efficiency and reliability. Our commitment to harnessing the potential of wood waste as a renewable fuel source has motivated us to manufacture cutting-edge boiler systems that deliver optimum performance while contributing to responsible industrial wood waste management.

Finding the Right Wood Chip Boiler for Your Needs

Wood chip boilers vary hugely in size, specification and cost. To identify the right boiler for your particular business needs, you must consider the key specifications of your wood chip heating system:

  • Particle size
  • Can I reduce waste to landfill?
  • Moisture content and calorific density
  • Ash content

Particle size

When it comes to wood chip boiler systems, particle size is crucial as the combustion rate for solid fuels is directly proportional to the fuel’s surface area. In simpler terms, smaller particles and dust ignite more rapidly than larger wood chips. Furthermore, smaller particles and dust tend to sit lightly on the fire grate, increasing the risk of being blown through the boiler without complete combustion. This risk is particularly high with cheap heat exchangers featuring shorter flame paths.

Particle size also has a significant impact on the composition of ash produced, resulting in varying fractions of base ash and fly ash. These variations can dictate the required flue gas cleaning process. For instance, dusty fuels demand more robust flue gas cleaning to prevent particulate matter from escaping through the chimney.

Moreover, particle size plays a substantial role in auger-fed systems as it influences the relative fuel density. Dusty fuels have a higher mass flow rate than larger particle fuels as the fine dust fills all the available air gaps. As a consequence, larger wood chip boiler augers must work harder, making more rotations to convey the same fuel mass.

Moisture content and calorific density

Moisture content significantly affects the calorific density of fuel, a factor that has substantial implications for the design of wood chip boiler systems, particularly their fire chambers. The wood type also plays a role in this equation.

While moisture content significantly affects energy availability, it is the wood chip boiler’s capacity to deliver the required energy output that matters in terms of the design of the fire chamber. Excessively high moisture content in wood chips can lead to problems such as tar build-up on heat exchanger surfaces, and potential damage to fans and flue gas cleaning equipment.

This also impacts the production of sufficiently hot flue gases, affecting the boiler’s performance.
Conversely, moisture content levels lower than what the fire chamber is designed for can cause overheating, resulting in damage, clinker accumulation and costly repairs.

The type of wood chips utilised also has a substantial impact. Chips from manmade boards, such as MDF and chipboard, generally have lower moisture content due to their production process. They can also boast a higher base calorific value due to the binding agents used in their composition.

Ash content

The ash content in wood chips can range significantly, from as low as 0.5% to as high as 35%. This diversity has major implications for both the design of the fire chamber and the ash conveying system. In fact, this range can vary by a factor of 60.

This means a fire chamber and de-ash system optimised for low-ash wood with 0.5% ash content would struggle to handle fuel derived from MDF due to its substantially higher ash content.

Wood Chip Boiler Installation Process

When installing a wood chip boiler, fuel ingress, fuel storage, fuel feed, combustion emissions and ash egress must all be considered. The method used for introducing wood chips into the system will depend on the particle size and the presence of fines in the fuel. If the wood chips are chunky and devoid of fines, open pours and conveyance systems can be utilised. However, when the dust fraction is high, the system may discharge dust indiscriminately, resulting in a messy, illegal and hazardous situation.

Storage considerations also come into play. The method for removing wood chips from storage depends on the particle size. For example, using a rotary valve designed for 25mm wood chips with 50mm-long chips may lead to bridging issues.

Furthermore, the combustion chamber must be suitable for handling the produced ash and accommodating the calorific density of the fuel. The flue gas and oil-cleaning system must also be capable of effectively managing the specific fuel being used.


Wood Chip Boiler Control Systems

Wood chip boilers come with a range of control options. In simpler setups, they connect to large buffer vessels, essentially oversized water tanks. Here, the control system often maintains a continuous wood chip feed throughout the burn cycle, allowing the boiler to run at maximum capacity until the desired temperature is achieved. However, this approach has its drawbacks, including energy loss during inactive periods and potential mechanical stress on the boiler due to continuous temperature changes.

Although for less temperature-sensitive applications these basic controls can suffice, when precise temperature control is vital, as in industrial processes or when it is necessary to meet strict service-level agreements, these systems may prove inadequate and less efficient.

At Ranheat, our advanced control systems can adapt the boiler’s output to match the specific heat load, relying on high-quality combustion control and effective flue gas cleaning. While the initial investment is higher, the long-term benefits include improved fuel efficiency and reduced heat cycling.

Maintenance, Servicing and Repair of Wood Chip Boilers

Wood chip boilers come in various designs and your preference can have a significant impact on how you will maintain the system. The type of fuel used also plays a substantial role in the ongoing cost of spare parts.

For example, a wood chip boiler designed for wood with 0.5% ash content and 30% moisture content would sustain significant damage if exposed to fuel with 30% ash content and 5% moisture content. This could lead to rapid deterioration of the fire chamber and excessive clinker formation, potentially blocking air holes.

In contrast, a Ranheat industrial wood waste boiler engineered to handle such challenging fuel types may experience wear and tear but would yield significant cost savings from using complex fuels. These savings can often cover the cost of spare parts and servicing.

We also offer comprehensive annual service contracts, including onsite work, remote access and remote support. Our compliance with HETAS regulations and auditing ensures a high standard of service and performance.


Why Choose Ranheat?

If you are keen on investing in a wood chip boiler system, our commercial and industrial biomass boilers are certainly a reliable, highly efficient and cost-effective option. Here’s why.

Extremely adaptable to changes in fuel properties

Ranheat industrial wood waste boilers are unique and quite different to “standard” wood chip boilers. They have been specifically engineered to operate using wood pellets and waste directly sourced from the woodworking industry, making them highly adaptable to variations in fuel properties.

No minimum particle size requirement

Ranheat wood chip boilers are also incredibly versatile. With no minimum particle size requirement, they can even run efficiently on wood dust alone. However, the maximum particle size they can handle depends on the wood-conveying equipment. Typically, a maximum particle size of 25mm is the most cost-effective option, but larger sizes can be accommodated using larger rotary valves and screws.

Can handle wood waste with high moisture content

Ranheat industrial wood chip boiler systems can efficiently handle wood waste and pellets with moisture levels up to 25%. For wood with higher moisture content, drying is required, and some of the boiler’s energy is used for this purpose. Drying can be automated with rotary drum dryers or managed in batches using kilns.

Can handle different fuels with varying ash content

We offer drop-in fire chambers tailored to accommodate fuels with varying ash content. We can also provide a range of ash-conveying options to ensure we find the optimal solution to suit your specific requirements.

Burn less-processed fuels

Ranheat industrial wood chip boilers can burn minimally processed fuels, some of which could cost as little as 5p/kWh or nothing at all. This is possible because any wood sourced from an audited waste stream, such as pallets and packaging, can be chipped, stored and fed into a Ranheat industrial wood waste boiler.

Get in touch

From design and manufacture to installation and ongoing servicing and maintenance, our team at Ranheat can provide end-to-end solutions for all your heating needs. Get in touch with us today and we will help you set up a biomass boiler system tailored to your unique requirements and available fuel sources.

Send us your enquiries via the contact details on this page.