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Economical and clean: using waste timber as a fuel. |
Mannheim Biomass Power Plant commenced operations in 2003 and specialises in generating energy from waste timber and non-recyclable timber. The plant can work with all categories of waste timber. At the plants own treatment facility, the timber is turned into wood chips suitable for combustion.
Boiler with spreader stoker
The plant combusts around 15 tonnes of waste timber and non-recyclable timber an hour. The material is combusted using a spreader stoker. The wood chips are blown with air from the hopper into the combustion chamber. Smaller parts are already combusted while still hovering. Larger parts fall onto the grate, where they burn out.
Around 80 tonnes of steam are generated an hour. The steam powers a condensing turbine, which in turn produces 20 megawatts of electrical output via a generator.
Use of residues and flue gas cleaning
The flue gas cleaning plant uses the latest technology to undercut the strict legal threshold values. The decomposition of nitrogen oxides (NOx) takes place in the boiler using the Selective Non-Catalytic Reduction (SNCR) process. Dust is initially removed from the flue gas in two parallel cyclones. Acidic noxious gases, heavy metals, dioxins and furans are bound by adding calcium hydrates and activated coke and removed together with the remaining dust in a baghouse filter.
The residues resulting from flue gas cleaning are used as backfill in the mining industry. The burnt out grate ash from the combustion chamber is put to environmentally-compatible use as a material for road construction and landscaping.
| Facts and figures | |
| Approval | In accordance with the 17th Federal Immission Control Ordinance |
| Subsidy period (EEG) | 20 years |
| Commissioned | 2003 |
| Types of timber | AI–AIV timbers (as defined in the Waste Timber Ordinance) |
| Firing | Travelling grate with spreader stoker |
| Timber silo | 5.000 m³ capacity |
| Storage capacity | approx. 5,000 Mg |
| Annual throughput | 130,000 Mg/a |
| Treatment capacity | 50 Mg/h |
| Imputed calorific value | 15,400 kJ/kg |
| Electricity output | 160,000 MWh/a |
| Personnel | Power plant: 15 employees Treatment: 10 employees |
Waste Timber Categories
The use of waste timber and non-recyclable timber in Germany is governed by the Waste Timber Ordinance. This subdivides the timber into various quality categories:
- AI: Untreated waste timber with insubstantial contamination
- AII: Treated waste timber which is glued, varnished, coated or painted
- AIII: Waste timber with halogen-organic compounds in the coating, but not wood preservers
- AIV: Waste timber treated with wood preservers with a high contaminant load (excluding waste pcb timber)
