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Why biomass for heat?
Biomass heating is a mature, proven technology and has been used successfully for many years. Using biomass is one of the only cost effective and practical ways to provide space heating, hot water and process heating/steam from a low carbon source. Also, using biomass sources for heating provides more cost-effective carbon savings than for other uses (e.g. for electricity or transport fuels). It typically offers the highest carbon savings per unit mass of biomass, and the highest carbon savings that can be obtained by using a unit of land to grow biomass.
Feedstock used
The most commonly used sources of biomass heating fuels are virgin wood, certain energy crops, industrial wood residues and certain agricultural residues. Biomass fuels are typically delivered as woodchips or wood pellets, but can also be in other forms such as logs or straw bales.
The table below outlines the typical fuels used for biomass heating systems:
|
Fuel |
Utilization |
|
Logs |
Most commonly used in small-scale systems ( |
|
Bales |
Generally either manually fed ‘batch-firing’ systems below 300 kWth (as above, requiring daily input to load the system with fuel) or alternatively very large (multi-MWth), automatically-fed heating/CHP plant. |
|
Chipped/shredded wood |
Typical fuel for most automated biomass systems (50 kWth – multi-MWth applications). |
|
Pellets |
Most commonly used in smaller or urban systems (light commercial |
|
Woodworking off-cuts/ sawdust |
Some biomass plant is specifically designed to burn co-products from the wood industries such as furniture off-cuts and sawdust. |
|
Cereals/grains |
Some biomass plant can burn common agricultural commodities such as oats and spent grain. |
Technology
Direct combustion is the most common method of producing heat from biomass. This process accounts for 90% of all energy recovered from biomass worldwide. For more information on the technology, please click here.
Biomass heating system
Major components of a combustion System:
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Fuel storage and delivery system: Fuel is drawn from the storage bin using a moving floor or screw conveyor, which then is fed into the combustor in a controlled manner.
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Combustor: The combustor is the enclosed chamber where the fuel is burned by heating it and adding oxygen in the right amount and proportion
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Heat exchanger: The heat exchanger removes the heat from the combustion gases and places it in the air or water that is used for space heating or other needs.
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Pollution Control Devices: Combustors require some sort of additional treatment to reduce the amount of pollution in the stack gas. Devices for treatment include cyclonic separators, bag houses, electrostatic precipitators, and scrubbers.
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Auxiliary boiler: These provide heat only when the requirement for heat drops below the biomass system’s turndown ratio (often about 20 percent of full load).
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Control system: The control system measures the operating parameters of the device; it adjusts the device to ensure smooth, high-efficiency, safe operation.
Biomass combustion systems cover a wide range of equipment, distinguished by variations in fuel and air delivery, design of combustion chamber and grate, type of heat exchanger, and handling of exhaust gas and ash. Other than very large heating plants, biomass based heat installations can generally be classified within three broad feed system categories, based on their capacity:
|
Small manual feed systems (50-280 kW) |
Typically are outdoor furnaces burning blocks of wood and distributing heat with hot water. |
|
Small automatic feed systems (50-500 kW) |
Use particulate biomass fuel (feedstock), typically utilizing a two-stage combustor (i.e. With a secondary combustion chamber) and incorporating a fire-tube hot water boiler (i.e. A tube that carries hot combustion gases through the water that is to be heated). |
|
Moderate-sized feed systems (400 kW and up) |
Have fully automated feeding of particulate biomass fuel (feedstock), typically utilizing a moving or fixed grate combustor with integral or adjacent fire-tube boiler for hot water, steam or thermal oil. |
Biomass for heat - Market segments
Biomass heating systems can be used for space heating of buildings, hot water production, steam production, or any combination of these. They can be used at almost any scale, from domestic (10kWth) through to ‘light’ commercial (50kWth to several MWth), to industrial or district heating systems (up to hundreds of MWth).
The three major markets which use biomass heating solutions are
Community energy systems
Community energy systems make use of a biomass heating plant and a district heating system to service clusters of buildings or even an entire community. Such community energy systems can provide space heating, heating of ventilation air, water heating, and process heat. Small community energy systems employ biomass heating plants, usually with a capacity of 1 MW or higher. The heat thus produced can be supplied to individual buildings, such as institutional (e.g. hospitals, schools, sports complexes), commercial (e.g. offices, warehouses, stores), residential (e.g. apartments) and industrial buildings.
Institutional and commercial buildings
Individual buildings can satisfy their heating requirements with biomass heating systems. The biomass heating plants in individual buildings tend to be of the “small-commercial” or “commercial” variety. For plants with capacity of 75 to 250 kW, small-commercial systems are common. Commercial biomass heating systems, sized from 200 to 400 kW, have characteristics of both small-commercial and industrial biomass heating systems.
Process heat applications
Small industrial biomass heating plants are used to provide process heat to industry, especially in those sectors where biomass waste is produced. These include sawmills, sugar plants, alcohol plants, furniture manufacturing sites, and drying sites for agricultural processes. Industrial processes will usually require substantial quantities of heat year round, thus justifying the higher capital costs of biomass heating through substantial savings in fuel costs.
Opportunities
Opportunities are diverse, and are present in different sectors such as agriculture (biomass cultivation and processing), transportation, bioenergy production, manufacture of core equipments and EPC etc. For more information on business opportunities in the biomass to heat sector, please click here.