Wood briquettes make an important contribution to renewable sources of heat. However, so far it has not been possible to feed small-scale furnaces automatically. But this could change very soon.

Because of a joint project the briquetting system manufacturer RUF together with DBFZ Deutsches Biomasseforschungszentrum gemeinnützige GmbH has drawn up an approach for an economically useful solution. The central feature is the so-called briquette crusher.

Solid fuels of biogenic origin are an important component of ecological sources of heat for private households and industrial companies. Wood briquettes, which are made of untreated wood, form part of this together with pellets or wood chips. Briquettes have many strengths: they can be produced easily and flexibly precisely where scraps of wood occur. In addition, they can be produced cheaply with modern machinery. However, wood briquettes also have a disadvantage: furnaces cannot be feed continuously and automatically with them – until now. In order to change this, the briquetting machine specialists at RUF GmbH, Zaisertshofen, together with the DBFZ from Leipzig, started a project that has laid the foundations for this. According to Andreas Jessberger, Sales Manager of RUF GmbH, the advantages of the briquettes – namely cheap, flexible production – are to be combined with the advantage of pellets – good conveyability. The task of the innovative project was on the one hand to find out how continuous briquette burning can be achieved and whether there are already marketable solutions for this. On the other hand the emissions occurring during burning had to be assessed and optimised if necessary. Crushed wooden briquettes make automatic feeding possible The DBFZ discovered through extensive product and patent research that there is currently no automatic, continuous feeding of wood briquettes for a small-scale furnace. There is merely a patent, which describes the irregular, requirement-oriented feeding of wood-fuelled boilers with paraffined wood briquettes. Reason enough to finally start the project. Jessberger stated: “First of all we must crush our RUF briquettes to implement our idea so that they can be conveyed evenly and automatically by means of a screw.”

A briquette crusher developed by RUF engineers (see box) accomplishes this task. According to the manufacturer, the briquettes used for feeding the machine have a fuel value 5.0 kWh/kg, the cross-section is rectangular (15.3 cm × 6.3 cm) and the height is 9 cm.