Canadian Biomass Magazine

Fire prevention strategies in biomass pellet production and use

July 13, 2022
By Tom Burniston

A complete fire system. Photo: Fagus GreCon.

As the world continues to strive to find ways to combat climate change, the methods and fuels used for power and heat generation remain strongly in focus. The energy sector is shifting towards creating a decarbonized and sustainable infrastructure. One method of achieving this goal is the use of biomass pellets as an alternative to traditional fossil fuels.

Fire prevention is a prime concern for all sectors of this growing market; risk of fire is inherent in both the production and use of biomass pellets. In the event of a fire or explosion there is a risk of injury and loss of life; damage to expensive machinery; damage to premises and storage facilities; production interruptions resulting in a loss of income and/or customers. These safety and economic risks can, however, be mitigated by employing field-proven automated fire prevention solutions to help protect people, premises and enable uninterrupted process and production.

Ignition risks

For both industrial scale biomass and more agriculturally based plants, the largest source of material for biomass pellet production is wood. The production process and use of wood pellets has an inherent risk of fire. The material itself is combustible, and the creation and presence of small particles present a risk of dust explosions. Continuous operation of fast-running machinery, high operating pressures and high process temperatures can result in sparks, glowing embers, and hot particles, all of which are potential sources of ignition. Early detection and extinguishment of ignition sources can minimize the risk of both fire and explosion.

In the pelletization process, there are various areas presenting significant risk. Mills, grinders, and presses all have the potential to create sparks and glowing embers due to the heat and pressure of the process. Furthermore, should any foreign bodies be present within the material – for example, stray pieces of metal such as nuts and bolts – the likelihood of creating an ignition source is greatly increased.

Dryers will also typically be used in the process to reduce the moisture content of the biomass pellets, increasing their value economically and as a fuel source. The simple nature of heating the product is another area of risk regarding ignition.

In the event of sparks, embers or hot particles being present, there is the potential for fire not only within the process itself, but also within the dust extraction system. Explosive atmospheres are created by the dust, and there is also the risk of igniting material gathered within dust extraction filters.

Fire prevention is also necessary in power plants using biomass for generation. Machinery and moving parts – for example, in conveying systems – are at risk of the build-up of heat within the component parts, especially in the event of any kind of machinery fault or failure. In addition, friction from the wood pellets rubbing against one another can also create heat, and in turn an ignition source.

In all these instances, there are solutions that can be employed to detect risk at an early stage, triggering extinguishment of ignition sources before they are able to cause a fire or explosion.

Fire prevention solutions

Various methods are available to detect fire, or the risk of fire. The simplest of these can be temperature measurement; another is the use of flame detectors. The downside of some of these solutions is that they can alert too late once a fire is already established or beginning to smoulder. In these cases, at the very least an interruption to production would be expected and it may be that machinery will be damaged or safety put at risk.

Infrared detection can be used which will provide the earliest detection of risk. Generally detecting in the spectral range from 780nm to 1,100nm, the most sensitive infrared detectors will see as little as a single spark. They will also have the capability to initiate a range of different actions depending on the number of sparks or embers detected, allowing appropriate levels of safety plans and mitigatory actions to be automatically triggered.

The most effective places to detect sparks are when material is in free-fall, such as in drop-chutes or transport areas. They are also easily detected in extraction ducts. However, the use of appropriate infrared spectroscopy can also allow hot particles and embers to be detected when material is more compacted, such as on conveying equipment.

Swift initiation of extinguishment is a vital component to implementing an appropriate fire prevention solution in biomass facilities. Upon detection of an ignition source, high-pressure water can be used by extinguishers triggered within milliseconds of a detection event.

Extinguishers are most effectively installed when considering the speed of material transport in relation to the reaction time following a detection event. In these instances, the sparks and/or hot particles are extinguished before they can proceed further through the process and cause a fire or explosion.

To ensure correct implementation of a fire prevention solution, producers and users of biomass pellets should work with experienced suppliers who are familiar with the types of risk within the plant or process, and who have the knowledge, instrumentation, and equipment to effectively specify a system to prevent a fire before it has an opportunity to start.

Tom Burniston is the head of sales of Fagus GreCon team in the UK.

This article is part of Dust Safety Week 2022. To read more articles on dust safety, click here.


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