SHWPCE
Bill Bardin
Homework 7
7.1
Pyrolysis is the heating of an organic material, such as biomass, in the absence of
oxygen. Because no oxygen is present the material does not combust but the
chemical compounds (i.e. cellulose, hemicellulose and lignin) that make up that
material thermally decompose into combustible gases and charcoal. Most of these
combustible gases can be condensed into a combustible liquid, called pyrolysis oil
(bio-oil), though there are some permanent gases (CO-2, CO, H2, light
hydrocarbons). Thus pyrolysis of biomass produces three products: one liquid,
bio-oil, one solid, bio-char and one gaseous (syngas). (United States Department
of Agriculture, 2010)
Gasification is a time-tested, reliable, and flexible technology that converts
carbon-containing materials, including waste and biomass, into electricity and
other valuable products, such as chemicals, fuels, substitute natural gas, and
fertilizers. Gasification does not involve combustion (burning), but instead uses
little or no oxygen or air in a closed reactor to convert carbon-based materials
directly into a synthetic gas, or syngas. It is this intermediate product, syngas, that
makes gasification so unique and different from combustion. (Gasification
Technologies Council, 2014)
7.2
C6H10O5 + Heat
CH4 + H2 + CO2 + C2H4 + C + H2O
Resulting products are methane, hydrogen, carbon dioxide, water vapor,
ethylene (as a liquid), and carbon (as a solid).
7.3
Is it possible to efficiently burn MSW in our boiler?
What kind of new emissions would we need to be concerned about?
What kind of pre-processing would be needed?
What is the average BTU content of the MSW?
How variable is the BTU content throughout the day?
Do we have facilities capable of handling MSW surges?
How steady is the MSW stream?
Would we need specialized handling equipment?
How do we deal with non-combustibles?
7.5
Raw MSW (RDF1)
FIne Shred
Organic MSW
(RDF-4)
Organic Seperation
Shredding (RDF2)
Organic Portion of
Shredded MSW
(RDF-3)
7.6
MSW is transported to the waste-to-energy plant where it is dumped into
storage pits.
The waste is typically sorted then further processed by shredding and
classification to produce refuse derived fuel (RDF).
The RDF is burned to heat water to produce steam which is used to drive a
turbine which in turn drives a generator to produce electricity.
In some cases, excess steam is used by local companies for process heat.
The products of combustion are scrubbed or otherwise extracted form the
stack, treated (if needed) and disposed of.
7.7
The burning of tires results in significant amounts of soot, particulate matter,
and other air pollutants. Because tires contain much more than just rubber,
there are issues with steel cord, and processing additives that also produce
toxins.
7.8
Notify the authorities.
Take steps to ensure the safety of the protesters.
Involve state DEP and other applicable entities.
Assemble public data showing the proper operation of the facility.
Provide a single point of contact for all press inquiries.
Prepare and issue press statements.
7.9
Polyethylene does produce toxic gasses when burned but the plant would
have proper pollution control equipment to deal with it. It should also be
pointed out that during the screening process, these plastics are culled from
the waste stream and recycled rather than be incinerated.
7.10
The EPA has implemented Maximum Achievable Control Technology (MACT)
to deal with emissions including dioxins. Dioxin emissions from Municipal
Waste Combustors in 1987 totaled 18 pounds, they are expected to be down
to ½ ounce in 2014.
7.13
The substance to be tested is placed in the calorimeter
The “bomb” is placed in the calorimeter water bath.
Electrical ignition wires are placed in the sample
Pure oxygen is injected into the calorimeter under pressure.
An electrical current is applied to the sample, igniting it.
The heat from the combustion heats the water.
The temperature profile is recorded over time.
The heat energy is calculated form the data.
7.14
The lower heating value (also known as net calorific value) of a fuel is defined as
the amount of heat released by combusting a specified quantity (initially at 25°C)
and returning the temperature of the combustion products to 150°C, which
assumes the latent heat of vaporization of water in the reaction products is not
recovered. The LHV are the useful calorific values in boiler combustion plants
and are frequently used in Europe.
The higher heating value (also known as gross calorific value or gross energy) of
a fuel is defined as the amount of heat released by a specified quantity (initially at
25°C) once it is combusted and the products have returned to a temperature of
25°C, which takes into account the latent heat of vaporization of water in the
combustion products. The HHV are derived only under laboratory conditions, and
are frequently used in the US for solid fuels.
7.16
In a mass-burn unit since there is no classification of the waste there needs to be
excess air to insure complete combustion.
In an RDF unit, less air is required since the feed stream has been reduced to a
more uniform feed supply.
7.17
Bridgeport Resco is a Mass-Burn unit.