The raw material wood

In our gasification power plants, in addition to natural wood and forest wood residues, also waste wood (for example from demolitions), except for particle boards, can be used.  Normally, waste wood is definitely less expensive than forest wood, an element that further increases the profitability of a GTS plant.


Properties

Properties

Wood chips
Wood chips

Wood chips must have a minimum quality to meet the needs of the system.  In particular, foreign components such as iron, stones and the like, as well as the proportion of bark, must not exceed the limit. Therefore, the use of bark mulch, for example, is not possible. With regard to size, at least 80 percent of wood chips must be 20 to 150 millimeters long. The proportion of wood chips under ten millimetres in length shall not exceed two percent, and the proportion of wood chips over 200 mm shouldn’t be higher than one percent. This because excessively shredded wood chips can cause problems in the operation of the gasification reactor, while too coarsely chopped ones can result in a blockage of the conveyor systems.


Particle size according to EN 14961 or Austrian standard ÖNORM M 7133

Standard Fine proportion Main fraction Coarse fraction Maximum length
P 100 / G 100 < 10mm 20mm - 150mm < 200mm < 250mm
Diameter Ø < 5mm Ø 10mm - 40mm Ø > 50mm Ø > 60mm
Contents Max 2% Min 80% Max 1% 0%

Forest wood

Forest wood

Forest wood
Forest wood

Ideally, forest wood is chopped after one year of storage (reduction of water content). The selection of the correct chipper matters in the production of wood chips with defined properties.

Disc, drum or screw chippers can be used, the latter being the ones which produce the best wood chips. However, the ends of the logs are not always completely crushed in chippers with conical screws as opposed to chippers with cylindrical screws, and must be separated if necessary. Besides the choice of the adequate chipping method, the production of quality chips is also obtained through a customized machine setup, handling and maintenance.


Waste wood

Waste wood

Waste wood is divided as follows:

Category

Description

Examples

A1

Natural finish or only mechanically treated waste wood that by use came into contact only with a negligible amount of foreign materials

Solid wood furniture without adhesive panels

A2

Glued, painted, coated, lacquered or otherwise treated waste wood without halogenated organic compounds in the coating and without wood preservatives

Particle boards (approved but for technical reasons not suitable for gasification), furniture without PVC components, interior doors, planks

A3

Waste wood with halogenated organic compounds in the coating

Furniture with PVC edges or PVC coatings

A4

Waste wood treated with wood preservatives, such as railway sleepers, electricity pylons, hop poles, props, and other waste wood, which due to the amount of contaminants does not fall into the A 1, A 2 or A 3 categories except for waste wood containing PCB

Railway sleepers, electricity pylons, rafters, windows, exterior doors, fences, wooden garden furniture

Waste wood containing PCB

Insulation boards, railway sleepers, pylons impregnated with coal tar oil


Processing

Waste wood
Waste wood

The processing of waste wood takes place by means of shredders or chippers, as they are not damaged even in case of a higher proportion of foreign materials (such as stones and metals). Shredded waste wood must be further processed by separating foreign materials, fine particles and oversized ones. In this case, drum and star filters have proven to be useful tools. According to the legislation in force, waste wood belonging to A1 and A2 categories, falling within biomass, is normally authorized for gasification. The use of A3, A4 and PCB-containing waste wood is therefore not allowed, although technically it should not pose any problem.



Electricity and heat from wood

Electricity and heat from wood

  • BTS Biogas
  • TS energyGROUP