FAQ and Information for Beneficiaries

What is a biomass boiler?

A biomass boiler is a boiler designed to burn solid fuels classed as biomass. Such boilers can be supplied to burn every form of biomass from woodchips, wood pellets or logs to waste agricultural materials such as straw and grain husks, olive kernels, rice and the dust from any of these including sawdust. Boilers need to be designed to burn specific materials, with any given boiler able to burn a limited range of biomass.

Can a biomass boiler be connected to my existing heating system?

Yes, in much the same manner as any other boiler. However, as many biomass boilers operate at a higher temperature, and hence pressure, than fossil fuelled boilers, with some operating at above 100C, it may be necessary to interpose a plate heat exchanger between the biomass boiler and the existing heating system.

How is a biomass boiler controlled?

In many respects biomass boilers can be controlled based on heat demand just as with fossil fuelled boilers. However, the much slower response of biomass boilers to changes in load mean that up to three control loops are used to control the fuel feed rate, the primary and secondary air fans, and the delivery of energy to the load including the charging/discharging of the buffer vessel. The minimisation of emissions requires carefully controlled combustion for which a Lambda sensor in the flue monitors the excess oxygen level to enable combustion to be optimised.

What are the best applications for a biomass boiler?

Biomass boilers operate at their highest efficiency, and are most reliable, when operating continuously. Biomass boilers cannot be switched on and off like fossil fuelled boilers and need to operate in conjunction with a buffer tank if the boiler is to be able to handle modulating loads, particularly loads less than the minimum boiler output, whilst continuing to operate efficiently. Biomass boilers are ideally suited to meet the continuous heat loads of buildings such as swimming pools, hospitals and nursing homes, and industrial processes with a constant heat demand. Other buildings with long periods of daily heat demand like schools and hotels are also a good match to a biomass boiler when a buffer tank is used in conjunction with the boiler.

Can a biomass boiler supply hot water in summer as well as heating in winter?

Summer hot water loads are usually very small in relation to the size of the boiler, typically 5% - 10% of the boiler rating and, as such, are always less than the minimum output of the boiler. The use of a correctly sized buffer vessel allows the boiler to be operated for short periods once or twice a week to charge the vessel. Hot water is then drawn from the buffer vessel as required to meet the load

What are the main components of a biomass system?

In addition to the boiler itself, a biomass system will require a fuel store (silo) and a mechanism to extract fuel from the store and to feed it into the boiler. The flue gases may require treatment and a cyclone grit arrestor is the most common flue gas cleaning device. Where a cyclone or other flue filtration system is fitted, an induced draught fan will be required on the flue. Finally, a buffer vessel will be required for the majority of boilers in the majority of circumstances

Can a biomass boiler work fully automatically?

All but the smallest of biomass systems can be configured to work fully automatically. Typical automated features include time switch or optimum start/stop, fuel feed, de-ashing and flue cleaning. The majority of boilers can operate for up to 1 week at a time without manual intervention.

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