Biomass Wood-fired combined heat and power
Biomass Wood-fired combined heat and power
From left to right: deaerator, water tube boiler, multi cyclone, electro static filter, flue gas condenser
At the Vink Sion greenhouse for sweet peppers, a 5 MWth wood-fired combined heat and power (CHP) plant is installed by Imtech-Vonk and HoSt. The plant provides heat and electricity for 8 hectare of sweet peppers. The plant is characterized by a unique high efficiency.The characteristics of the CHP plant are:
| Input Wood | 5.7 MWth |
| Hot water steam condenser | 3.6 MWth |
| Hot water flue gas condenser | 1.7 MWth |
| Electricity | 1.15 MWe |
| Total useful energy | 6.45 MW |
| Total efficiency | 113% from input |
| electrical efficiency | 20 % |
| Green house area | 8 ha |
| Natural gas saving | 4 million Nm3/year |
The wood-fired CHP plant consists of wood storage, a furnace, a high-pressure boiler, a steam turbine, a steam condenser, a flue gas condenser and a electro static filter.
The combustion process
The plant uses "A quality" wood. The wood chips are stored in two bunkers with moving floors. After storage, the chips are transported onto the grate in the furnace. The grate and the furnace are based on Swedish design of Saxlund. At the grate the wood is combusted. The produced hot flue gasses are fed into the boiler.
High efficiency
The type of steam boiler that is applied in this plant is special. It is not a flame tube boiler but a water tube boiler. The water tube boiler has a high steam pressure of approx. 55 bar instead of the 28 bar pressure level that is frequently used in flame tube boilers. With this higher pressure the electrical efficiency of the CHP increases, because of the larger expansion of the steam in the turbine. Another advantage of the water tube boiler is that there are almost no soot deposits on the tubes, which means less maintenance and cleaning of the boiler. This water tube boiler needs less space than a flame tube boiler, because of the vertical construction.
Electricity
The steam turbine expands steam and generates 1150 kWe electrical power. Most of the electrical power is supplied back to the public electricity grid.
Heat
In the steam condenser the heat for the green house is produced from the steam. The steam condenser produces 3600 kWth thermal power. To realise the unique high efficiency an extra thermal power of 1700 kWth will be generated by the flue gas condenser. The flue gas condenser is supplied by our Swedish partner SRE. The heat of the flue gas condenser is used by a low-temperature heating net of 45°C in the greenhouse. This extra heat originates from the water content of the wood. Biomass fuels can contain up to 60% moisture. When the biomass fuel is combusted, the moisture is evaporated. This evaporation costs a lot of energy, which is normally lost when the flue gas leaves the stack. Using the flue gas condenser, the flue gas is cooled down, the water vapour in the flue gas is condensed and the energy of evaporation of the water is recovered. This energy can is used in the greenhouse.
CO2
Finally, the CO2 can be selectively absorbed with a special-design installation. The produced CO2 will be used in the greenhouse. This reduces the need for CO2 production by combustion of natural gas and it adds to the sustainability of the CHP.
Power energy and management
Imtech Vonk is supplying various products and services in the field of electrical generation conversion & distribution. From Diesel Generator Sets up to switch and controlgear, it can all be handled through one and the same supplier: Imtech Vonk B.V.
With extensive experience in electrical engineering & design we can guarantee a state-of-the-art solution for almost every project against competitive prices.
Some examples:
• Power generation up to 3 MW
• Containerised generator sets (diesel/gas)
• HV switchgear
• LV switchgear & motor control centres
• LV sub-distribution switchboards
Control panels, power management systems, generator control & protection panels