Tableros Losan is a particle board factory that, due its activity, produces a lot of dust and bark as wastes, which can be exploited to produce energy (biomass). Bark was burned in an existing thermal oil boiler while dust was burned in existing dryers.
With the aim of improving factory’s competitiveness and due to the fact that not all generated biomass could be used, it was decided to install a cogeneration plant of 22.9 MW in combined cycle (gas turbine of 19.4MW and steam turbine of 3.5MW) and a simple cycle biomass plant where 4 MW were generated.
The combined cycle cogeneration plant can supply all thermal demand of the factory (2.3 MWt of thermal oil and 13.9 MW of hot gases to the dryers).
Part of the exhaust gases from the gas turbine are sent to a thermal oil generator and after passing it, they are sent to two wood shavings dryers.
The gases that are not necessary for the production of thermal oil or for drying are sent to a recovery steam boiler, where they are cooled against the water-steam circuit. In this way, the condensate from the steam turbine of the biomass cycle plant is heated before it is introduced into the thermal deaerator. In the boiler, up to 18.8 t/h of superheated steam is generated at 41.5 bar(a) and 400ºC.
The biomass plant (its fuels were bark and dust) burns the fuel that no longer has to be used to produce thermal oil and hot gases for dryers, in a boiler to produce 21,1 t/h of superheated steam (41.5 bar(a) and 400ºC) that is send to a steam turbine to produce 4 MW.
The bark is transported, from the storage area to the biomass boiler, through a drive system with redler conveyors. With regard to dust, it is transported, from storage silos to the biomass boiler, by a pneumatic suspension system.
Since these are two fuels with different characteristics, they are burned at different points in the same boiler and under equally different conditions. Bark is burned in a grate firebox combustion chamber and dust is burned in a separate combustion chamber with an specific burner.
The biomass boiler is prepared to operate under the following conditions:
- Using only dust to generate all steam demand
- Using only bark to generate all steam demand
- Using 60% dust and 40% bark
- Using 40% dust and 60% bark
- Using 75% dust and 25% bark