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The fundamental design of wood biomass boiler systems commonly
installed under the FFS&B program is fairly basic.
Basic system components include a fuel storage bin, fuel
conveyance system, a firebox (combustion chamber or gasifier), an
emissions control system including but not limited to a stack, and
an attached water boiler. Basic
operation involves the wood fuel being conveyed to the firebox via
an augering system. In the firebox, the
wood fuel is combusted and its heat transferred to heat the boiler
water system which then distributes hot water or steam throughout
the facility’s HVAC and/or hot water distribution systems.
While basic system operation follows this general concept, different
manufacturers design and build their systems in different ways which
employ varied technologies and mechanisms.
Certain designs may better suit particular scenarios and
applications and care should be taken to match the right system to
meet your needs. Variations of design
may be determined by factors such as quality of wood fuel to be
used, type of vehicles available for fuel delivery, facility space
limitations, and compatibility with the existing HVAC distribution
system.
Technology Resources
·
Identify local sources
and estimated quantities available. Find
out who has residues and what they’re currently doing with them
(mills, other wood product manufacturers, arborists, landfill, etc.)
For forest residues, local state and federal land management
agencies may help to identify current and future forest management
projects that will produce residues, and assist in identifying
contractors in the area as potential suppliers.
·
Identify potential suppliers
in the area with equipment for processing material (chipper/grinder)
and trucks for delivery.
·
Identify the type of wood fuel commonly available in your area.
Do this as you’re exploring different system designs and communicate
that with the system engineers. Determine
whether the fuel will be chipped vs. ground wood
material from forest or urban sources, soft- or hardwoods, a mix of
both, sawdust, wood pellets or other material.
By doing this, the system manufacturer can design a
conveyance and burner system that is compatible with the wood fuel
you intend to burn.
Factors that commonly affect the cost and availability of wood fuel
include rates of material generation, ease of collection, competing
users and haul distances. It’s important
to note that the cheapest wood fuel is not always the
best. Your wood fuel should meet
certain standards and specifications as designated by the system
manufacturer which provide for a few things: ease of conveyance,
high heat value, and quality consistency.
To maximize flexibility in your suppliers it’s good to design your
fuel storage facility to accommodate deliveries from a variety of
locally available delivery vehicles (walking floor trailer, dump
truck, potato truck, tractor, front-end loader, pneumatic systems,
etc.).
Fuel Supply Availability Resources
Biomass as a Feedstock for a Bioenergy and
Bioproducts Industry: The Technical Feasibility of a Billion Ton
Annual Supply (“The Billion Ton Report”), USDA and DOE,
April 2005
A Geographic Perspective on the Current Biomass
Resource Availability in the United States, NREL, Dec.
2005
TimberBuySell.com online Marketplace
for Forest Resources and News
Managing Organic Debris for Forest Health:
Reconciling fire hazard, bark beetles, wildlife and forest nutrition
needs, A Pacific Northwest Extension Publication, 2009.
Wood Fuel Transportation Resources
A Study of How to Decrease the Costs of
Collecting, Processing and Transporting Slash, MCDC, et
al., Dec. 2004
Options for Transporting Biomass, USFS
Forest Residue Transportation Costing Model
(Trucking Simulator) Interactive
spreadsheet calculator designed to compare costs of varied
alternatives for slash collection, processing, and transportation
methods.
Using forest biomass for heat and energy production can offset air
emissions from a number of activities—displacing open burning of
slash piles; encouraging treatment of densely over-stocked forests
at risk of damaging infestations by insects and disease and
catastrophic wildfires, thus maintaining the forests ability to
sequester CO2; and displacing CO2 emissions from the combustion of
fossil fuels.
Like other energy combustion sources, wood boilers emit pollutants,
including particulate matter (PM), nitrogen oxides (NOx), carbon
monoxide (CO), volatile organic compounds (VOC), sulfur dioxide
(SO2), carbon dioxide (CO2), hazardous air pollutants and trace
elements. Particulate matter emissions can be minimized by
choosing clean and efficient technology designs, proper systems
operation and maintenance, and with the installation of pollution
control devices. As part of the FFS&B partners' commitment to
ensuring good air quality, they have sponsored stack emissions
testing on a variety of systems, regularly share lessons learned
with the public at large, and continue to collaborate closely with
regional and national air quality managers.
As you begin the design of a wood biomass energy system, consult
your local, state, and national regulations as these will vary by
location and project.
For national
and regional information from the EPA.
Update on federal air pollution regulations for
smaller commercial/institutional boilers,
January 29, 2009 (PDF, 26 KB)
Information
on Air Pollution Control Technology For
Woody Biomass Boilers, March 2009 (PDF, 158 KB) -
This document describes the types of control technology available
and their effectiveness, and various aspects of designing and
operating woody biomass boilers.
Emissions
Test Reports from Fuels for Schools and Beyond Projects
Air Quality
Presentations from 2007 Workshop