Cogeneration
Cogeneration, also known as ‘combined heat and power’ (CHP) or the combined cycle, is the simultaneous production of heat (usually in the form of hot water and/or steam) and power, utilising one primary fuel.
Primary fuels commonly used in cogeneration include natural gas, oil, diesel fuel, propane, coal, wood, wood-waste and biomass. These ‘primary’ fuels are used to make electricity, which is known as a ‘secondary’ fuel. The pulp mills use black liquor as primary fuel.
The operators of pulp mill power plants are required to apply for a licence to operate as a cogenerator. Until 2003 these licences required that that all the power generated in excess of the mill’s consumption be sold to the grid. Since November 2003, cogenerators have been allowed to sell all their power to the grid at a subsidised guaranteed green tariff and buy from the grid all the power needed for their industrial activity at the regular tariff.
Cogeneration involves burning the black liquor at the recovery boiler, generating electrical and thermal power that are sold to the grid in their entirety.
Currently Altri produces 365 GWh of electric power through cogeneration per year, broken down by mill as follows:
- Celbi 180 GWh
- Caima 100 GWh
- Celtejo 85 GWh