Wood-Chip Heating Systems - Biomass Energy Resource Center

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WOOD CHIP HEATING SYSTEMS 18 CHAPTER THREE The Components of a Biomass Energy System Even more than gas and oil systems, solid fuel systems require a careful integration of components to make sure the whole operation runs smoothly. These components include: • the fuel storage facility, • any driveways necessary to provide access for large fuel-delivery trucks, • a boiler room to house the combustion equipment, • the boiler or combustion appliance, • fuel-handling equipment to move the fuel from storage to the boiler, • a chimney to exhaust the combustion gases, • any necessary exhaust-gas cleaning devices, • ash disposal equipment, and • the controls that keep all the equipment operating optimally. Also, the person who actually operates the plant is one of the most important components of a successful system. This will be discussed in more detail later. Types of Fuel Storage Systems The most common type of biomass fuel storage for automated commercial and institutional facilities is the rectangular, below-ground concrete bin. Compared to above-ground storage, these bins have a number of advantages: • Because the bottom layers of chips are well below frost level, below-ground bins keep chips from freezing in cold weather. • Self-unloading delivery trucks can use gravity to discharge quickly into the bin without any other mechanical equipment. • Below-ground bins may be less visually obtrusive than those built above ground. Photographs throughout this book illustrate various confi gurations of loading doors for below-ground bins. Doors can be either horizontal (set into the ground-level roof of the bin), sloped (when the bin is located next to the side of a building), or vertical (when the bin is covered by a roofed building taller than a delivery truck). See photos on pages 46, 49, and 14 for examples of horizontal, sloped, and vertical door systems. Whether they work manually, hydraulically, or on electric winches, these doors must be designed to be easily operable in all weather conditions. It is best to have loading doors that work for deliveries from self-unloading tractor trailer vans and from dump trucks. With vertical door systems, the door height must be carefully designed to assure that it can accept deliveries from dump trucks. Above-grade bins or silos are also sometimes used for biomass storage. These are typically circular (similar to concrete or steel agricultural silos), although rectangular bins have also been used. See the photos on page 69 for one example of a metal silo. Above-ground bins can present freezing problems with green fuel in the coldest weather. They also require mechanical loading equipment, usually powered by electric motors, to convey the fuel from ground level (where it is discharged by the delivery truck) to the top of the bin. Small metal silos (sized to hold considerably less than a tractor-trailer load of chips) can be used to decrease a project’s initial cost. The disadvantage is that deliveries will be more frequent, and fuel suppliers may charge more per ton. Although a small metal silo may be less expensive than a full-sized below-grade bin, a metal silo big enough to hold a full 40-foot van load of chips will have probably have little or no cost advantage over a concrete bin. In the lower-cost agricultural biomass systems that are typically found on farms or in greenhouses, fuel is
Figure 3.1 A Typical Biomass System fuel storage bin (walls not shown) receiving auger bin unloading system (hydraulic scraper type shown) induced draft fan sometimes stored in ground-level sheds with concrete fl oor pads (dirt and asphalt fl oors should be avoided). These sheds can be very inexpensive to build. On delivery the fuel is dumped onto the pad in or in front of the building, and shoved or scooped in place with a tractor or front-end loader. The tractor is also used to remove the fuel from storage and transport it to an automated receiving bin; see photo on page 50 for an example. Although construction costs for this type of bin are lower, it involves operator labor on a daily basis and requires a tractor or loader of some kind. These systems are also well-suited for small schools where a fully automated system is prohibitively expensive. Semi-automated systems cost about half as much as fully automated systems. In some cases, storage system costs can be reduced by using one or more fuel delivery trailers for on-site fuel storage. The simplest approach is to use a conventional delivery van backed up to a loading dock or ramp. A small loader/tractor removes fuel from the trailer and fi lls an automatic day bin. A more sophisticated approach is to use a self-unloading trailer (see photo on page 52), which is backed up and connected inclined fuel conveyor chimney cyclone fl ue gas cleaner boiler combustor Courtesy KMW Energy Systems to a day bin in one wall of the boiler room. In this way the unloading and handling of fuel is fully automatic. In either case the day bin must be large enough to feed the system while the trailer is off-site being refi lled. Systems using more than one trailer have some advantages, but may cost as much as building a permanent fuel bin. Sizing the Fuel Storage System Every biomass system must have suffi cient onsite fuel storage. For small systems, such as those in schools, the storage is usually sized according to the volume of the delivery vehicle. Generally, storage bins should hold at least one and one-third to one and onehalf times the volume of delivered fuel per truckload. Fuel suppliers usually do not like to deliver partial loads, so sizing at less than a delivery load is not a good idea. Sizing the effective volume of the bin bigger than the truck volume allows the operator to order a delivery before the bin is empty. When designing a storage bin, it is important to account for the difference between the bin’s gross volume and its effective volume. The effective volume depends on the percentage of the bin that can actually WOOD CHIP HEATING SYSTEMS 19
Page 1 and 2: Wood-Chip Heating Systems A Guide F
Page 3 and 4: Wood-Chip Heating Systems A Guide F
Page 5 and 6: TABLE OF CONTENTS How to Use This B
Page 7 and 8: The appendices may be consulted as
Page 9 and 10: urners in the biomass fuel-producin
Page 11 and 12: Fuel Hardwood Chips No. 2 Fuel Oil
Page 13 and 14: Randolph Union High School, Randolp
Page 15 and 16: CHAPTER TWO Wood Chips and Other Ty
Page 17 and 18: Barre Town Elementary School, Barre
Page 19: in a system designed to burn hardwo
Page 23 and 24: An Important Relationship: Fuel Sou
Page 25 and 26: Murray Farms Greenhouse, Penacook,
Page 27 and 28: oiler facility. However, the backup
Page 29 and 30: The use of powerful and potentially
Page 31 and 32: in effi ciency: the higher the mois
Page 33 and 34: an effi ciency of 69%. This differe
Page 35 and 36: at a higher capital cost. For examp
Page 37 and 38: Older Residential Stove 1 EPA Certi
Page 39 and 40: CHAPTER SIX Types of Biomass Combus
Page 41 and 42: Figure 6.2 Two-Chamber Combustion S
Page 43 and 44: Cost-Effectiveness of Wood-Chip Sys
Page 45 and 46: Figure 7.3 Existing Gas Cost/ccf $3
Page 47 and 48: a value, independent of concerns ab
Page 49 and 50: • initial system equipment/instal
Page 51 and 52: engineering fi rms that specialize
Page 53 and 54: CHAPTER NINE Finding Capital to Pay
Page 55 and 56: installation and do not incur the r
Page 57 and 58: CHAPTER TEN Putting Together and Im
Page 59 and 60: The Importance of the System Operat
Page 61 and 62: Q: Will wood smoke cause acid rain?
Page 63 and 64: Data on the installed cost of bioma
Page 65 and 66: say exactly how it should do that.
Page 67 and 68: Green Acres, Barre, Vermont Facilit
Page 69 and 70: Contracting and Project Structure O
Page 71 and 72:
fully trained in operating, maintai
Page 73 and 74:
CHAPTER TWELVE The Future of Biomas
Page 75 and 76:
maintenance time has been reduced t
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APPENDIX A Northeast Regional Bioma
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APPENDIX C Wood-Fuel Energy Data I.
Page 81 and 82:
APPENDIX D Assumptions Used in Deve
Page 83 and 84:
Current year oil price . . . . . .
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Net Annual Savings $100,000 $90,000
Page 87 and 88:
Glossary Appliance effi ciency: The
Page 89 and 90:
Furnace: The primary combustion cha
Page 91 and 92:
Sizing: The process of specifying t
Page 93:
Jarrett, Branyon O. “Catch 22 in
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Wood-Chip Heating Systems - Biomass Energy Resource Center

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