Storage Silos for Biomass
Ensuring the quality and availability of the biomass fuel
The main purpose of storage is to keep the biomass in good condition and in a suitable place so that it can be easily transferred to the next stages of the process of transformation of biomass into energy and heat through combustion.
In many cases, one of the main concerns is to keep it dry, protecting the biomass rain, humidity and the water that drips to the ground. Must also be protected during the supply of the local storage, its transfer and during access for maintenance.
Types of Storage Systems
The systems can be:
- With the purposes and structural forms that are specific to the storage, both above ground as underground;
- Units are suitable, such as silos for food or sheds;
- Units of immediate availability, pre-fabricated and designed for a specific type of biomass such as pellets.
Supply, storage and extraction of biomass
The project of storage of biomass fuel should consider the supply and the extraction of the biomass, as well as access for maintenance, which is very important for the efficient operation of an installation of the biomass.
The preferred method for the supply must also be considered. If the wood chips will be delivered by a truck-truck, the most efficient method is to deposit them directly in the store of fuel. This may require a ramp to allow access of the truck to the storage silo if it is built wholly or in part underground.
If the wood will be chopped on the spot, there is the possibility of storing directly within a silo by air.
Biomass in general is a fuel energy density low, consequently a large volume must be stored on site and if the frequency of supply required is very large, and a reserve of safety with a sufficient margin must also be maintained.
It is advisable that biomass is stored close to the site of the combustion equipment to avoid blockages or difficulties in the supply of fuel to the burner, and which is accessible to the vehicle load to supply the place of storage.
For the majority of the stores of dry biomass, good ventilation is required to prevent the build-up of condensation, allow to dry further, and to prevent the formation of humus and fungi that can present health hazard if inhaled.
The good air flow can also help to minimize the composting of the fuel, leading to loss of energy content, and avoid the build-up of excessive temperatures with the risk of fire. Studies in the USA and in Denmark suggest that one should not build mounds of wood chips above 8 to 10 meters for this reason.
Both in above ground storage as well as in below-ground installations, some forms of drainage should be included, for the case of entry of unwanted water and also to in cases of necessity of cleaning of the bins, such as in cases of contamination by fungi.
Factors to consider:
- The biomass does not drain as freely as the oil or natural gas.
- Usually it will absorb moisture if it is exposed.
- You may naturally biodegrade in the store if it is not dry. This leads to loss of the energy potential and the formation of fungus and mold.
- The design of a memory efficient:
- The device should keep the fuel in good condition, particularly protecting it moisture.
- It must also be possible to discharge the biomass into a suitable container for transportation.