Fuel From The Forest
Metso installs gasification plant, turning Sweden’s forestry waste to biogas
by amanda m. klemp
It may still be nine years away, but the EU’s 20/20/20 targets are driving continual development in fuel and power technology and systems to meet the goal of: a reduction in EU greenhouse gas emissions of at least 20% below 1990 levels; 20% of EU energy consumption to come from renewable resources; and a 20% reduction in primary energy use compared with project levels, to be achieved by improving energy efficiency. Göteborg Energi AB, a Swedish energy company, is working to develop renewable fuel by generating natural gas-quality biogas from biomass sources. With a larger goal of producing 100 MW of biogas from Sweden’s forestry waste, the company opted to first install a gasification plant for the production of 20 MW of gas.
The GoBiGas20MW fuel processing plant project will be installed by Metso, which has facilities in Göteborg, Sweden allowing the energy provider to work with a local company. Metso’s gasification system is based on licensed technology for indirect gasification from Austrian com14 pany Repotec. With forest residue and wood pellets as the main fuel sources, the system, together with a methanation process and upgrading system, will produce biomethane for distribution in the existing gas grid.
Initially, the plant will be fed by wood pellets, but once forestry waste is introduced to the system, about 8900 kg/hr of the biomass will be used to generate 20 MW of biomethane. The fuel first has to go through the gasification process, where it begins in a drier. From the drier it goes into the gasifier, which uses steam for indirect gasification. The heat for this process is produced via combustion. To begin the purification process, the gas undergoes a tar removal process.
To finish cleaning the gas to natural gas standards, it enters the methanation process, where it goes through a second tar removal process, sulfur removal, CO2 removal, and then the methanation and final drying. After this final cleaning and methanation, the gas is imported to the utilities’ natural gas supply and used in Göteborg Energi’s power plant.