Key principles for BTC
- High-pressure steam treatment and gasification of biomass
- Combustion in a gas turbine for power generation
- Optimised heat integration
High-pressure steam treatment and gasification
Biomass is first pressurised utilising steam. Using a lock-hopper for pressurisation, we are able to utilise solid fuels of varying sizes and shapes. Initially, we have focused on wood chips but we intend to include a broad spectrum of biomass to maximise value for our customers. Steam treatment of the biomass downstream causes the formation of biocoal, an optimal fuel for the following gasification step, or an excellent product for external use in industry or agriculture.
The resulting biocoal and the wood gases are then combined with air from the gas turbine in an entrained flow gasifier to produce a high-quality syngas to power the gas turbine. Steam and water injection are used to control and cool the process.
Combustion and power generation
After clean-up in the hot gas filer, the combined syngas and steam flow is lead to the gas turbine for combustion at 60+ bar with air from the gas turbine compressor. Here the steam moderates the flame and limits production of unwanted by-products such as thermal NOx. The resultant hot gas with up to 50% steam drives the gas turbine expander, providing power to the generator
Optimised heat integration
The BTC technology is based on an integrated process with steam as an efficient heat carrier and working media in the entire plant. Steam advantageously recovers energy from both the gas turbine exhaust and the gasification process and channels it back to the gas turbine. This steam, flowing through the combustor and expander, limits temperatures and removes the need for costly and energy-intensive compression of excess air.
To recover the steam utilised, the water content in the exhaust gas is condensed. In contrast to the far majority of power plants, this makes the BTC plant is water self-sufficient, i.e. without the need for external make-up water. The heat removed while extracting this condensate can be efficiently used for district heating systems and other heat loads such as biomass drying.