Note: Descriptions are shown in the official language in which they were submitted.
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Renewable Blended Natural Gas and Rock Wool Production
from a Plasma Based System
Background of the Invention
FIELD OF THE INVENTION
This invention relates generally to processes and systems for generating a
blended Natural Gas of a BTU content high enough to be reinjected into the gas
main. This is also combined with the production of rock wool to develop a high
efficiency renewable energy plant at a low capital cost when the feedstock is
renewable such as Municipal Solid Waste (MSW). This design of plant is
becoming
more desirable as high tipping fees and high transportation costs demand
small,
distributed, cost effective, MSW / renewable energy facilities.
DESCRIPTION OF THE RELATED ART
There is significant interest in renewable energy projects. Thermal plasma
has consistently distinguished itself as a high efficiency, low emissions
gasification
process for just about any feedstock, and has been identified as one of the
most
desirable processes for use in producing energy from renewable fuels.
If an analysis of plasma MSW (or other renewable fuels) relative to other
energy facilities is conducted, it becomes apparent that the lack of existing
plasma projects is not exclusively the result of technological challenges, but
also
results from the relatively poor economics associated with this technology.
Plasma technology is not inexpensive when compared to disposition of waste
using landfill, incineration, or conventional gasification.
Many plasma projects fail at the onset, notwithstanding extensive initial
marketing efforts, usually as a result of inadequate financing and low or
nonexistent profitability. Recently some states have allocated bonuses for
development and use of renewable energy, and such efforts have stimulated the
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use of plasma systems in the production of energy. Unfortunately, it is
expected
that this modest boon to plasma usage will be short lived, as it represents an
artificial market that is a poor model on which to build a business. This is
particularly problematical when one considers that these facilities are
expected to
operate cost effectively for at least thirty years.
Many plasma projects in the past have pinned false hopes on high tipping
fees for hazardous waste without fully understanding the complications that
are
associated with such materials. The handling of these materials are not only
complex and expensive, but also potentially dangerous if not properly
engineered.
The entire process and the facility itself thus becomes unduly expensive. Most
counties emphatically state that they do not desire large quantities of
hazardous
waste to be transported through their communities. However, large quantities
of
such waste must be generated if the facility is to achieve profitability. The
production and delivery of the hazardous waste have to be carefully
coordinated
since it is dangerous to store biological and other hazardous waste feedstock.
The process and system of the present invention overcomes the economic
hurdles noted above for a plasma system. It is to be understood, however, that
the invention herein described is not limited to the use of a plasma
gassifier. In
some embodiments of the invention, conventional gassifiers, inductively heated
gassifiers, or inductively heated gassifiers with plasma assist, can be
employed.
The use of a plasma gassifier in the practice of the present invention simply
increases overall system effectiveness.
The system of the present invention is simple, flexible, and very energy
efficient. In short, it produces a large amount of renewable energy from a
feedstock such as Municipal Solid Waste ("MSW"), for a very small capital
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investment. Any feedstock can be used, including, for example, biomass or
algae.
MSW is but a common example of a renewable feedstock.
It is, therefore, an object of this invention to provide a simple and cost-
effective renewable energy system.
It is another object of this invention to provide a renewable energy system
that can consume virtually any feedstock.
It is also an object of this invention to provide a simple and cost-effective
renewable energy system that can use a conventional gassifier.
It is a further object of this invention to provide a simple and cost-
effective
renewable energy system that can use a plasma gassifier.
It is yet another object of this invention to provide a cost-effective
renewable energy system that can use an inductively heated gassifier or an
inductively heated and plasma assisted gassifier.
It is additionally an object of this invention to provide a process and
system for blending natural gas with syngas at a ratio that can be re-injected
into
the natural gas main.
It is yet a further object of this invention to provide a process and system
for the production of rock wool to enhancing the thermal and financial
efficiency of
the renewable energy plant.
It is yet an additional object of this invention to provide a process and
system for extracting heat energy from a plasma gassifier and providing the
heat
energy to any process that requires heat, including buildings, and thereby
increase the efficiency of the renewable energy facility.
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Summary of the Invention
The foregoing and other objects are achieved by this invention which
provides a method of extracting energy from a gassifier and delivering the
energy
to an energy transfer medium, the method including the steps of:
extracting syngas from a gas product issued by the gassifier;
delivering the extracted syngas to a fuel blending system; and
producing a blended fuel by mixing the syngas with a gaseous fuel, the
gaseous fuel having a higher thermal (BTU) content than the syngas.
In a practicable embodiment of the invention, the gassifier is a plasma
gassifier. In this embodiment, there is provided the further step of re-
injecting
the gas product into a gas main supply. Additionally, there is provided the
further step of delivering the gas product to a pre-gassifier to increase
system
efficiency. Reclaimed heat is, in some embodiments, delivered heat to the
pre-gassifier. The gaseous fuel includes any combination of natural gas,
butane,
propane, pentane, ethane, and any other suitable gaseous fuel.
In an advantageous embodiment of the invention, there is further
provided the step of controlling the thermal content of the blended fuel. The
step
of controlling the thermal content of the blended fuel includes, in some
embodiments, the further step of employing a sensor in a feedback loop. The
sensor can be any of a flame ionization detector, a calorimeter, or a
spectrometer.
In an efficient embodiment of the invention, there is further provided the
step of producing rock wool. In other embodiments, there is provided the
further
step of producing accessory heat.
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Prior to performing the step of extracting syngas from a gas product
issued by the plasma gassifier there are provided, in some embodiments, the
further steps of:
oxidizing a feedstock fuel to produce oxidized feedstock fuel; and
5 delivering the oxidized feedstock fuel to the plasma gassifier,
whereby a work load of a primary heat source of the plasma gassifier is
reduced.
In accordance with a further method aspect of the invention, there is
provided a method of extracting energy from a plasma gassifier and delivering
the chemical and heat energy to an energy transfer medium. In accordance with
this further aspect of the invention, there are provided the steps of:
extracting syngas from a fuel product issued by the plasma gassifier; and
delivering the extracted syngas to a fuel blending system for forming a
blended fuel having a thermal content that is greater than the thermal content
of
the extracted syngas.
The invention provides a method of producing blended natural gas to be
used on-site, or re-injected into the main, or any other gaseous fuel, rock
wool
production, and accessory heat production all at a low capital cost. This
process
is due in part to modern syngas production methods. Syngas production has
taken a large step forward in quality when it is produced using a pyrolysis
method
combined with plasma generated heat. This process has proven itself to be far
superior to conventional gassifiers. The thermal (BTU) content of the product
syngas can consistently be held to about 300 BTU/Cu ft. This relatively low
quality fuel is a step forward for renewable feedstock gasification but falls
far
short of the requirements of modern boilers, internal combustion engines, and
turbines.
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When this fuel is compared to others on a Wobbe Index it fairs poorly. The
low energy density creates a variety of difficulties for all forms of engines
or
turbines. Turbine manufacturers in particular have found it difficult to
produce
energy using syngas. These prime movers also add significant cost to any
renewable energy project which makes the project less likely to be built, or
to be
operated profitably.
A key attribute of the plasma based gasification system is the ability to
control the process and generate relatively consistent thermal (BTU) content
in
the resultant gas. This allows the blending of the syngas with other fuels
such as
natural gas to produce a fuel of consistently high quality.
In addition to the foregoing, feedback systems are also now available with
reasonably short time constants to allow continuous closed loop adjustments to
the fuel quality. Calorimeters can now be integrated to feed data back in
minutes, and devices like flame ionization detector(FID) units can feedback
data
in seconds.
When the blended natural gas invention described herein is used in
conjunction with the production of value added products such as rock wool and
facility accessory heat, a very cost effective and efficient method of
implementing
renewable power is achieved. This is a considerable asset in the endeavor to
promote the acceptance of plasma based renewable energy facilities
Brief Description of the Drawing
Comprehension of the invention is facilitated by reading the following
detailed description, in conjunction with the annexed drawing, in which Fig. 1
is a
simplified schematic representation of a process and system for generating
blended natural gas from a renewable energy source constructed in accordance
with the principles of the invention.
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Detailed Description
Fig. 1 is a simplified schematic representation of a process and system 100
for generating blended natural gas from an energy source constructed in
accordance with the principles of the invention. As shown in this figure,
municipal
solid waste or other feedstock, designated as MSW 1, is delivered, in this
specific
illustrative embodiment of the invention, to system 100 by a crane 2. The
feedstock can be any organic material, or an inorganic mix. Crane 2 transfers
MSW 1 to a shredder 3. The shredded feedstock (not shown) is then delivered to
a pre-gassifier chamber 4. It is to be understood that any other form of
gassifier
can be employed in the practice of the invention. In this embodiment, pre-
gassifier 4 helps to reduce the work of plasma torch 21, which is the primary
heat
source of plasma chamber 9.
The feed system, which includes shredder 3, compresses the incoming
feedstock MSW 1 so as to minimize the introduction of air. Plasma chamber 9,
or
other conventional gassifier is, in this specific illustrative embodiment of
the
invention, advantageously operated in a pyrolysis mode, or in air and/or
oxygen
combustion boosted modes of operation. Additives such as lime 5 are added, in
this embodiment, to the gassifier to control emissions and improve the quality
of
an output slag 24.
Methods of chemically boosted heat such as the use of liquid or gaseous
fuels and an oxidant injected into port 6 can be used in the practice of the
invention. Additionally, any of several fuels such as propane, recirculated
syngas,
ethane, butane, pentane, etc. can be used in the practice of the invention to
supplement the heat input of plasma torch 21.
The quality of the syngas is improved in this embodiment, by the injection
of steam 25 into plasma chamber 9.
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A syngas product is supplied via a syngas line 10 to a quench system 23 to
reduce particulate and other emissions and to reduce the temperature of the
syngas to a level that is acceptable to a final syngas purification system 13.
Persons skilled in the art will realize sour water cleanup systems for the
quench
system have been omitted from the drawing for the sake of clarity.
A final Heat recovery system 14 is generates heat that is used in this
embodiment to operate pre-gassifier 4. Alternatively, in other embodiments
such
heat is sold as accessory heat. Heat produced by quench system 11 can also be
sold or delivered to the pre-gassifier. A cooling tower for the facility has
been
omitted from this figure for the sake of clarity.
Compressor 15 draws a slight vacuum on system 100 and directs the
syngas to a three way valve 26 and a calorimeter 16. In other embodiments,
other fuel quality measuring devices, such as a flame ionization detector
(FID),
can be used in the practice of the invention. The syngas in line 17 is
directed to a
blending valve 27 that mixes natural gas 18, or any other fuel such as ethane,
propane, butane, pentane etc. Mixing valve 27 is employed in a closed loop
control arrangement that maintains a quality of fuel appropriate for re-
injection
into a natural gas main 29. Thus, typically about 5% to 10% concentration of
syngas is utilized in this embodiment. It should be understood this invention
is
not limited to 5% to 10% blend concentrations. The product gas is pressurized
by
compressor 28 prior to being re-injected into gas main 29.
Financial productivity and overall system efficiency of the plant are
enhanced by spinning or blowing slag 24 into rock wool by apparatus 30. The
rock wool is then shipped by truck 31.
Although the invention has been described in terms of specific
embodiments and applications, persons skilled in the art can, in light of this
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teaching, generate additional embodiments without exceeding the scope or
departing from the spirit of the invention described and claimed herein.
Accordingly, it is to be understood that the drawing and description in this
disclosure are proffered to facilitate comprehension of the invention, and
should
not be construed to limit the scope thereof.
