No. 98 European Community Demonstration projects for energy saving and alternative energy sources

Wood roasting unit (Project No BM/333/84-F)

Aim of the project

The project consisted of building a wood roasting unit and demonstrating on an industrial scale that the roasting process is technically and economically viable. 

Roasted wood is obtained by subjecting wood to thermo-condensation at a temperature of between 250 and 300° C. It is therefore an intermediate product between wood and charcoal. It has most of the advantages of both products.

Cost

The total investment amounted to FF 19 million (1985 value). 
The following financial aid was received:

Economics

LA VAL DE CERE is the first industrial plant to apply the wood roasting process. Profitability was affected by teething troubles that persisted for over two years. Now that the technology has been mastered, profitability will depend on maintaining sales to the electrometallurgy industry and increasing sales to the general public. On the basis of a 3/4 to 1/4 split, the payback period should be four years at a production rate of 12,000 tonnes per year of roasted wood.

User

LE BOIS TORREFIE DO LOT Lava! de Cere 
F-46130 Bretenoux France 
Tel: 65.33.84.16

Manufacturers

Description

The manufacturing process is in three stages CHOPPING, DRYING, and ROASTING.

The wood comes from forests in the neighborhood and is received in the form of round wood or edgings. A drum chopper cuts the round wood or edgings into chips 50 to 80 mm long and 15 mm thick at a rate of 20 t/hour. 

At the outlet a screen removes any pieces larger than 80 mm {which are recycled) and any fines smaller than 15 mm {which serve to fuel a boiler).

The wood chips {with a moisture content of some 40 %) are transported to a tunnel kiln for drying. Heating for the kiln is obtained from a heat transfer fluid backed up by hot air obtained by burning gases. produced during roasting. The heat transfer fluid itself is heated up by being passed through the boiler to which the fines recovered in screening are sent. A set of valves coupled to regulators maintains the required levels of temperature in the different sections of the dryer. By the time the wood reaches the dryer outlet, the moisture content has dropped to 10%.

The roaster is a hot mixing device with a double sheath and a rotating shaft with disc sections perpendicular to the axis of the shaft. Heating by conduction is obtained by circulating the heat transfer fluid between the two layers of sheathing and through the hollow agitator. Inside the roaster, thermostats coupled to regulators maintain the temperature at a level within: t 0.5° C of the temperature, as required in order to obtain a product with a constant quality.

To avoid the danger of spontaneous combustion, the temperature is reduced at the roaster outlet.

The wood-distillation gases generated in the roaster are burned in an incinerator. The fume is de-dusted, diluted and returned to the dryer. The installation is thus non-polluting for the environment.

The process is continuously monitored via the parameters of temperature, pressure and flow rate, all the measuring instruments being mounted in a control room. Laboratory checks are carried out during production on the commercial product and on consignments.

The results obtained on an industrial scale have confirmed the initial assumptions as regards feasibility {the maximum production capacity of the unit has been achieved) and quality.

Nevertheless, there were major initial difficulties:

The gases are burned in a special incinerator installed immediately after the roaster. The fumes are dedusted, diluted and channeled to the dryer to provide additional heat.  The difficulties resulted in investment costs being higher than forecast and were the main reason for the lack of profitability at the demonstration stage. Nevertheless, the profitability of any future projects should be guaranteed.

Energy production:

A total of 10,000 tonnes of roasted wood was produced in 1988.  Assuming a net calorific value of 22,200 kJ/kg for the roasted wood, this would give an energy equivalent of 5,300 toe/year. It should also be emphasized that the energy yield from roasted wood is far superior to that from charcoal since roasted wood contains 90% of the energy contained in the wood from which it is made.

Prospects and replication

The qualities of roasted wood make it a promising pro- duct as regards making the best use of wood. At present the electrometallurgy industry is the main customer for the product that is being used as a reducing agent in electric furnaces instead of charcoal that is less reactive.

In the leisure market roasted wood is used as fuel for barbecues where its advantages are that it can be easily ignited, it quickly produces embers and it is clean, making it more convenient to handle.

So far there have been no attempts to use the roasted wood for commercial energy production. But a study as shown that, compared with other biomass fuels; roasted wood is a high quality product.

As roasted wood contains 90% of the energy present in the wood from which it is made, applications can be envisaged in developing countries. It would make for the rational use of forest biomass and thus represents an alternative to the deforestation now taking place in many countries.

The company

Le Bois Torrefie du Lot is a subsidiary of Pechiney Electrometallurgie. This company is the sole holder of the patent for producing roasted wood. In 1988 production amounted to 10,000 tonnes.

The company's experience

Where roasted wood is concerned, Le Bois T Torrefied du Lot has experience, which it is prepared to share with any undertaking seeking to make the best possible use of wood.

This project is now ripe for replication throughout the Community. Interested parties who may wish to adopt this process or to exploit it commercially are invited to contact

Le Bois Torrifie du Lot, Laval de Cere, F-46130 Bretenoux, France Tel: 65.33.84.16

Commission of the European Communities, Directorate-General for Energy Demonstration projects, 200, rue de la Loi, France B-1049 Brussels

The Community may grant financial support for energy demonstration projects.

Demonstration links the R & D stage, sometimes tested on pilot plant, and the later investment stage. It differs from the R & D and pilot stages in the industrial scale of the projects, the requirement of having prospects of economic viability, and from the normal investment stage in that the inherent risks are still considered by the entrepreneurs to be too high.

A demonstration project must satisfy the following conditions:

The support granted takes the form of a financial contribution by the Community. The Commission publishes calls for proposals for demonstration projects in the Official Journal of the European Communities.

Any natural or legal person in public or private law, any institution or any group established in the territory of the Member States may submit an application.