U.S. patent application number 11/534547 was filed with the patent office on 2008-03-27 for liquefaction process.
Invention is credited to Barry Cooper.
Application Number | 20080072478 11/534547 |
Document ID | / |
Family ID | 39223391 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080072478 |
Kind Code |
A1 |
Cooper; Barry |
March 27, 2008 |
Liquefaction Process
Abstract
A process for producing a fuel product from biomass that
includes providing a biomass feedstock to a high-shear mixer,
mixing the biomass feedstock in the mixer in the absence of oxygen
and under conditions sufficient to undergo liquefaction, and
re-circulating and blending the liquefied biomass with the biomass
feedstock.
Inventors: |
Cooper; Barry; (Tucson,
AZ) |
Correspondence
Address: |
QUARLES & BRADY LLP
ONE SOUTH CHURCH AVENUE, SUITE 1700
TUCSON
AZ
85701-1621
US
|
Family ID: |
39223391 |
Appl. No.: |
11/534547 |
Filed: |
September 22, 2006 |
Current U.S.
Class: |
44/606 ; 44/605;
44/628 |
Current CPC
Class: |
C10G 1/00 20130101; Y02E
50/30 20130101; C10G 1/002 20130101; C10G 1/02 20130101 |
Class at
Publication: |
44/606 ; 44/605;
44/628 |
International
Class: |
C10L 5/00 20060101
C10L005/00; C10L 5/40 20060101 C10L005/40 |
Claims
1. A process for producing a fuel product from biomass, comprising
the following steps: (a) providing a biomass feedstock to a
high-shear mixer; (b) mixing said biomass feedstock in said mixer
in the absence of oxygen and under conditions sufficient for the
biomass to undergo liquefaction, thereby forming liquefied biomass;
and (c) re-circulating and blending at least a portion of said
liquefied biomass with said feedstock biomass.
2. The process of claim 1, wherein said biomass feedstock is a
solid organic-waste material.
3. The process of claim 2, wherein said organic-waste material
includes a cellulosic constituent.
4. The process of claim 3, wherein said cellulosic constituent is
wood.
5. The process of claim 1, wherein said high-shear mixer is a
high-shear screw extruder system.
6. The process of claim 1, wherein said biomass feedstock and said
liquefied biomass are co-mingled prior to introduction into said
mixer.
7. The process of claim 1, wherein the liquefied biomass is heated
prior to co-mingling with said biomass feedstock.
8. The process of claim 1, wherein at least a portion of said
liquefied biomass is subjected to a hydrogenation reaction.
9. A process for producing a fuel product from organic-waste
material, comprising the following steps: (a) providing a
organic-waste material feedstock to a high-shear screw extruder
system; (b) mixing said organic-waste material in the absence of
oxygen in said extruder at a temperature of at least 650 degrees F.
and at a pressure of at least 200 psi, thereby forming liquefied
organic-waste material; and (c) re-circulating and blending at
least a portion of said liquefied organic-waste material with fresh
feedstock organic-waste material.
10. The process of claim 9, wherein said organic-waste material
includes a component selected from the group consisting of
bituminous-waste material, cellulosic material, rubber material,
waste organic sludges, or mixtures thereof.
11. The process of claim 9, wherein step (c) includes heating the
liquefied biomass prior blending with the fresh feedstock
organic-waste material.
12. The process of claim 9, wherein at least a portion of said
liquefied biomass is subjected to a hydrogenation reaction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Enormous quantities of wood waste material are produced both
by recycling and as byproducts of industrial and commercial
activity. For example, it is estimated that about 5,000 lumber
mills in the U.S. continuously generate sawdust and wasted wood at
a rate of approximately ten percent of the processed lumber.
Similarly, over 1,100 cotton gins in the U.S. produce gin waste in
the form of cotton stalks, mostly lignocellulose, which have to be
plowed into the ground in order to minimize insect damage. The
lignocellulosic stalks of corn, wheat, other grains, hays, grasses,
sugar cane bagasse, and soybeans are also produced in large
quantities but, with the exception of sugar cane bagasse, they are
largely left to waste because of the expense involved in collecting
them.
[0003] Much potentially useful biomass waste is also available from
dead wood in forests, which is typically destroyed by insects,
microorganisms, or fires. Further, national forests have
accumulated an excess of living biomass in the form of dense small
trees, shrubs and pine needles that should be removed to save
older, large trees from being destroyed in catastrophic wild forest
fires. Moreover, solid waste from municipal sewage treatment plants
consists of a sludge that contains organic material and toxic
constituents that constitute a disposal problem. Similar wastes are
produced by nearly 100,000 dairy operations in the U.S., which must
continuously dispose of a mixture of bedding and manure, all
organic material. Additional organic-waste material is produced in
large quantities as waste from cattle, hog, chicken and turkey
farms. Finally, it is estimated that approximately 280 million
automotive tires are discarded annually in the U.S., ranging from
20 to 1,000 pounds in weight, which also represents a serious,
continuing disposal problem.
[0004] Most of this waste material is currently being disposed of
in landfills around the world. Approximately 300 million tons of
solid waste is placed in about 3,500 landfills around the U.S.
alone every year, about 70-80 percent of which is organic matter.
Thus, it is clear that the magnitude of these organic wastes
constitutes a serious environmental problem. As a result,
increasingly stringent regulation of waste disposal practices are
being imposed to satisfy environmental standards. Therefore,
reutilization of these materials has become an important component
of prudent industrial policy.
[0005] With the advent of energy sources being limited by OPEC in
the 1970's, three programs were initiated to develop a source of
domestic oil. They were 1) coal liquefaction, 2) oil shale mining,
and 3) biomass liquefaction. Once the oil crisis calmed, these
programs were scaled back. In the case of biomass liquefaction, two
projects survived.
[0006] The first was run by the U.S. Department of Energy in
Albany, Oreg. in the late 1970's. The liquefaction process
consisted of mixing a carrier oil with low wood flour
concentrations and introducing this slurry into a closed loop
heated/pressurized system. The slurry was recycled at various
pressures and temperatures for times from 12 hr. to several days. A
key component was the use of a piston pump to pump and pressurize
the slurry. While the oil made had O.sub.2 levels of 8 to 12%
versus the 53% of the wood flour, two major problems were noted.
The first was the inefficiency of the process. It took
approximately three times as much energy as was gained. In
addition, cycle times of days dictated that a very large plant must
be utilized for the process to be economically viable. The second
problem was the tendency of the piston pumps to plug on the wood
flour. Thus, this liquefaction process was not reliable or
economically sound.
[0007] The second project was funded by the U.S. Department of
Energy with overview by Battelle Northwest. The main research was
conducted by the Department of Chemical Engineering of the
University of Arizona in Tucson. The pump problems experienced in
the first project were solved by using a plastic extruder to pump
and pressurize the slurry. Optimum slurry levels of 50/50 (wood
mass/carrier oil mass) were found on single screw extruders and
65/35 on twin screw extruders (versus 12% wood mass/88% carrier oil
mass used in the Albany project described above). Lower wood levels
were easier to pump, while higher wood levels increased conversion
quantities. A total of 57 runs explored process variables to
determine their influence. Pressures up to 3000 psi and
temperatures up to 400 degrees C. were evaluated. Superheated steam
was injected into a tubular reactor just after the extruder. In
addition, CO was injected to increase the hydrogenation of the
created oil to make it more like petroleum. While these studies
resulted in a better understood and efficient liquefaction process,
the overall efficiency was still not economically viable enough for
commercialization.
SUMMARY OF THE INVENTION
[0008] A primary goal of this invention is the use of liquefied
biomass to induce more efficient breakdown of biomass in the
production of a combustible energy product. More particularly, the
invention relates to a process for producing a fuel product from
biomass that includes providing a biomass feedstock to a high-shear
mixer, mixing the biomass material under conditions sufficient for
the material to undergo liquefaction, and re-circulating and
blending at least part of the liquefied biomass material with the
feedstock.
[0009] In a preferred embodiment of the invention, the process of
the invention takes advantage of the reactive nature of liquefied
biomass material to induce the breakdown of a new feedstock of
biomass by re-introducing the liquefied biomass back into the
high-shear mixer.
[0010] According to these and other embodiments, the present
invention involves the degradation of feedstock biomass, which
preferably is organic-waste material, with a liquefied biomass
produced by the direct liquefaction or fast pyrolysis of the
feedstock biomass material. Such liquefied biomass is produced
according to known liquefaction processes in the absence of oxygen
at typical temperatures between about 230 and 370 degrees C. (about
450-700 degrees F.) and typical pressures between 200 and 3,000
psi. Alternatively, a liquid biomass product may also be produced
by the process of fast pyrolysis, which is instead carried out at
atmospheric pressure and at temperatures of 400-600 degrees C.
(about 205-315 degrees F.) with a residence time of about two to
five seconds, or at temperatures greater than 600 degrees C. with
residence times of less than 0.5 seconds.
[0011] If desired, the liquid biomass so produced by either direct
liquefaction or fast pyrolysis may be mixed with additives (such as
the heavy ends of fast pyrolysis, petroleum asphalts, natural
bitumens, oils from tar sands, oils from shales, heavy ends of coal
liquefaction, petroleum pitch, and petroleum coke derived from
petroleum delayed coking processes) in order to modify its
characteristics to meet specific needs of particular applications,
and the resulting mixture may further blended with one or more
additional materials of choice.
[0012] Various other purposes and advantages of the invention will
become clear from its description in the specification that follows
and from the novel features particularly pointed out in the
appended claims. Therefore, to the accomplishment of the objectives
described above, this invention consists of the features
hereinafter illustrated in the drawings, fully described in the
detailed description of the preferred embodiments and particularly
pointed out in the claims. However, such drawings and description
disclose only some of the various ways in which the invention may
be practiced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a flow chart depicting a method of the
invention.
[0014] FIG. 2 depicts a high-shear mixer of the invention.
[0015] FIG. 3 is a magnified view of another high-shear mixer
embodiment used in a method of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] This invention is based on the idea of utilizing liquid
biomass produced by direct liquefaction or fast pyrolysis in a
high-shear mixer to more efficiently produce combustible fuels.
While other reactive liquids also can aid in liquefaction (such as
unsaturated fatty acids/derivatives), utilizing liquid biomass to
aid in the breakdown of solid biomass feedstock is more
efficient.
[0017] As used in this disclosure, the term biomass refers in
general to any organic-waste material that has been found to be
suitable for conversion to liquid form by a process of liquefaction
or fast pyrolysis. In particular, and without limitation, such
biomass and organic-waste material are defined as organic material
containing various proportions of cellulose, hemicellulose, and
lignin; to manures; to protein-containing materials, such as
soybeans and cottonseeds; and to starch-containing materials, such
as grain flours. Hemicellulose is a term used generically for
non-cellulosic polysaccharides present in wood. Finally,
organic-waste material is intended to include rubber waste material
(such as from tires), and bituminous wastes (such as from coal
fines).
[0018] The term liquefaction, as used in this disclosure with
reference to biomass, refers to direct-liquefaction and
fast-pyrolysis processes by which a solid biomass is converted into
liquid form. Such processes are well known in the art. For
convenience, the liquid materials formed by liquefaction are
referred to in the art and herein as "liquefied" materials, as
distinguished from "liquified" materials formed by condensation
from a vapor state. Direct-liquefaction processes provide high
yields of liquid products from biomass by the application of
sufficient pressure, typically in the range of 200 to 3,000 psi, in
the absence of air, and at approximate temperatures in the 230-370
degree C. range. Fast pyrolysis processes, which also produce a
liquid product from biomass, are instead carried out at atmospheric
pressure and at temperatures of 400-600 degree C. with a residence
time of about two to five seconds, or at temperatures greater than
600 degree C. with residence times of less than 0.5 seconds. It is
noted that, in contrast, indirect-liquefaction processes first
convert biomass to gases, which are then caused to react
catalytically to produce liquids. The scope of this invention does
not include liquids obtained by indirect liquefaction.
[0019] A key difference between the invention and the related art
lies in the frictional heat generated in the high-shear mixer
(e.g., in an extruder with the high shear screw). As used herein,
"high shear" means a compression ratio that ranges from between
about 1.25:1 to 4:1. In other words, the substance(s) being acted
upon by, for example, an extruder screw, is compressed from between
about 0.8 to about 0.25 its original volume. Thus, both heat and
pressure in a highly localized area are present so that slow heat
transfer from heating elements located outside the mixer is not a
hindrance. The nature of a high shear screw can further be
descriptively defined in two stages. The first allows movement of
the free flowing biomass (e.g., wood chips) into a compressed area
that pushes into stage two. The second stage is a high shear
rotation of the extruder screw or similar device with a very small
gap over a very small length of the screw. Depending on the design
of the extruder or similar device, too much compression or too long
a section of high sheer compression will cause the screw to lock up
or stall the motor. Too large a gap or too slow a rotational speed
will not result in liquefied biomass.
[0020] A second key difference is the returning of liquefied
biomass to the mixer to react in the high-shear zone immediately
with the solid biomass feedstock (e.g., wood) to form more
liquefied biomass.
[0021] In a preferred embodiment, the high-hear mixer includes a
screw extruder system. As well understood in the art of extrusion,
very viscous liquid materials can barely be poured from a container
by gravity. Hence, when such materials are placed under high shear
rates (wherein one layer is moved rapidly away from its adjacent
layer), internal friction is generated within the viscous liquid,
which in turn generates heat. Thus, the energy of the electric
motor turning the extruder screw under high torque is converted
into frictional heat, which causes the viscous liquid to rise in
temperature with a resulting lower viscosity.
[0022] A pilot plant with two different biomass processing designs
has been constructed to overcome several of the deficiencies of the
earlier liquefaction processes. The first was a loop reactor which
utilized previously created liquefied biomass to preheat the
incoming biomass feedstock. The second was a loop reactor as above
with external heating elements that provided a preheating step. The
combination of the preheating and recirculation of the liquefied
biomass created a "digestion effect" missing in earlier
designs/processes. In other words, the incoming feedstock biomass
is degraded more readily because the liquefied biomass (and
especially the pre-heated liquefied biomass) is very reactive. This
allowed much greater output rates and lower energy costs per
barrel, since the mixer has to utilize less external heat to attain
the threshold temperature at which liquefaction takes place. An
additional benefit is the flashing of any remaining water in the
biomass.
[0023] In contrast, previous liquefaction processes needed extra
heat (such as from superheated steam) to achieve the same results,
albeit at a much slower rate. Since commercial plants will use
chopped biomass (e.g., wood chips) rather than "flour," the cost
associated with grinding is reduced or eliminated. The pre-digested
chip is easily smeared/sheared in the mixer. In addition, since the
new treated/exposed surface area of is virtually the same as flour,
the chip diameter can be increased to match the feed section of the
size of the mixer used. High shear screws, such as those used in
screw-type extruders, can accelerate the break down of the chips to
liquefied biomass. The optimum efficiency (energy out/energy in)
for the process of the invention has been found to be 4/1 vs. 1/1
and 0.3/1 for previous processes.
[0024] The aggressiveness of reactivity of the liquefied biomass
grows at higher temperatures, with ester, alcohol, acid, and
anhydride functional groups all thought to play a role. The use of
high shear extruder screws increases the rate of production of bio
oil by dramatically increasing the wood surface area which helps
more quickly expose the wood to the ambient heat. In addition, the
work shear produced by the screw creates extra heat above that
supplied by the external heater source alone.
[0025] A preferred continuous process would recycle bio oil
(liquefied biomass) at >600 degrees F and infuse it with a
steady stream of newly metered biomass (e.g., wood) at 50-350 psi.
This defines a continuous digestion step. The excess oil would be
collected as final product prior to the slurry being introduced
into the extruder. The wood/oil slurry preferably is heated to a
temperature over 250 degrees. The extruder would heat the mix to
>600 deg. F. and pressurize to over 1000 psi. The mix would then
be depressurized to allow the steam and CO.sub.2 to separate from
the bio oil and be used to dry the incoming wood. Alternatively,
the steam could be used to perform mechanical work, such as will a
steam engine. A less efficient process (semi-continuous batch)
would still recycle the liquefied biomass but would use alternating
vessels to mix the hot oil and dry wood. Thus, while the slurry
from one is fed to the extruder, the other(s) would be filled with
hot bio oil and wood. When the first vessel is empty, the activity
would reverse.
[0026] The rate of conversion is a function of rate of digestion,
temperature, pressure, shear level, and residence time (length and
linear rate) in the reactor. The equilibrium of conversion is
dependent on these and supplemental hydrogenation. For example,
introducing CO to the mix to react with the water in the wood to
produce hydrogen via the water shift reaction.
[0027] Moreover, the chemical reduction of the liquefied biomass
(i.e., hydrogenation) in a secondary step preferably is performed
to get maximum heat content and distillation potential of the
produced fuel.
[0028] Turning to FIG. 1, a flow diagram illustrating methods of
the invention is shown. The process starts with the recirculation
of liquefied biomass 2 (either previously produced or generated
contemporaneously) to either a mixing area 4 within the high-shear
mixer 6 or to a digestion vessel 8, where the liquefied biomass 2
and biomass feedstock 10 are combined to produce a predigested
slurry. Preferably, heat 12 is applied to the liquefied biomass 2
such that the temperature reaches between 250 and 450 degrees F.
while being under 50-350 psi of pressure P. Additional processes
may then be carried out with the excess liquefied biomass, such as
bio-binder processes 14 or hydrogenation processes 16. Given its
higher combustion quality, hydrogenated oils 18 typically are
further utilized in fuel processes 20 (either to power other
processes in shown in FIG. 1 or for external purposes).
[0029] As seen in FIG. 2, a high-shear mixer of the invention
preferably is a screw-type extruder 30, which may be either a
single or multi-screw extruder. The extruder 30 includes a metallic
helical screw 32 that is closely fitted into a metallic barrel 34.
In the embodiment shown in FIG. 2, biomass feedstock 36, which
preferably is chipped wood, is fed into vessel or hopper 38.
Preferably, the hopper 38 is supplied via supply lines 37a and 37b
with heated liquefied biomass 40 so that the biomass feedstock 36
is at least partially digested by the reactive hot liquefied
biomass 40 prior to extrusion. The resultant slurry is fed into the
extruder 30 by means of crammer-feeder 42 (or, alternatively, a
auger feeder), which helps assure continuous feed of the feed mix
under some pressure. Alternatively, albeit less efficiently, the
biomass feedstock 36 and liquefied biomass 40 may contemporaneously
be introduced into the barrel 34 of the extruder 30 without a
separate digestion step.
[0030] As well understood in the art of extruders, heating takes
place in the feed and compression zones of the extruder by surface
friction upon the wall of the extruder barrel 34. Liquefaction of
the biomass feedstock 36 is attained by providing a suitable air
environment (pressure devoid of oxygen) and temperature by heat
transfer through the barrel 34 using sources of heat generation,
such as electrical heater 44. Other, indirect sources of heating
may be used, such as induction or radiant heat, and the heat
provided by the heated liquefied biomass 40 also is utilized.
[0031] As the biomass feedstock 36 and liquefied biomass 40 is
heated and mixed in the extruder 30, internal friction, called
viscous dissipation, further heats the mixture. The additional heat
energy is created by the electrical power of the motor driving the
screw 32 and constitutes energy converted into frictional heat. The
helical screw 32 of the extruder 30 also generates pressure by
exerting a drag flow upon the mixture. The screw 32 furthermore
moves the biomass material down the barrel 34 and to a supply line
46 and/or storage container. As well understood in the art, viscous
dissipation is the process by which heat is generated in a highly
viscous fluid by the dissipative action of shearing forces acting
on the fluid, such as can be produced in extruders. See R. B. Bird,
W. E. Stewart and E. N. Lightfoot, "Transport Phenomena," J. Wiley
& Sons (1960), pp. 276-279; and S. Middleman, "Fundamentals of
Polymer Processing," McGraw-Hill Book Co. (1977), pp. 131-137 and
371.
[0032] Another embodiment of an extruder for use in a process
according to the invention is shown in FIG. 3, wherein the barrel
50 is of constant internal diameter throughout its length. The
diameter of the helical screw 51 in feed section 52a is small and
increases continuously in the compression/metering section 52b.
This has the effect of generating high shear rates in the biomass
existing in the compression/metering section 52b. The high shear
rates, in turn, generate pressure and assist in the liquefaction
process.
[0033] The present invention is based in part on the fact that all
organic-waste materials also contain reactive chemical groups.
Lignocellulosic material, the major component of trees, shrubs,
stalks, grasses, and growing vegetation in general, contains
cellulose and hemicellulose molecules with two reactive hydroxy
groups. These groups react readily with other organic groups,
especially aldhehydes. Therefore, such feedstock material is
suitable raw material for combination with liquefied biomass, which
leads to a more efficient liquefaction process.
[0034] The liquefied biomass produced by direct liquefaction can
have different chemical compositions and properties, depending on
the liquefaction conditions. For example, different tar-like
products were obtained by the direct liquefaction of Douglas Fir
wood operating at about 3,000 psi and temperatures in the 324-350
degree C. range (about 615-660 degree F.) in the presence of a
synthesis gas (67% carbon monoxide and 33% hydrogen). The resulting
products varied from 3.2 to 18.1 wt percent in oxygen content and
from 13,300 to 16,530 Btu/lb in heating value. Obviously, different
raw materials would also yield different liquefied biomass, which
may vary in consistency from tar-like products to light oils. As
one skilled in the art would readily appreciate, similar
differences exist in the liquefied biomass obtained by fast
pyrolysis.
[0035] Thus, it is well known that any biomass, especially
lignocellulosic material, can be converted into a heavy tar or oil
by applying heat and pressure in the process, while retaining most
of the heating value of the biomass feedstock in a more
concentrated form. Water and carbon dioxide are driven off the
biomass to make it more like a petroleum crude oil. For the
purposes of this invention, the temperature and pressure can be
adjusted to give a very viscous liquid product, which can be pumped
at 150 degrees C. (about 302 degrees F.) but is a brittle solid at
ambient temperatures. Test data show that the high molecular
weights of the cellulosic and hemi-cellulosic portions of the
biomass are degraded to lower molecular weight aromatic and
aliphatic ethers, alcohols, hydrocarbons and a variety of other
chemicals.
[0036] The following examples illustrate the invention with regard
to organic-waste material.
EXAMPLE 1
[0037] A mixture of 50% liquefaction biomass oil and 50% white pine
screened to feed a 1.25 inch Davis Standard extruder was heated to
300 F for 2 hours. The mixture was then run through the extruder
with a 4:1 compression ratio and converted to any oil with a heat
of combustion of 14,000 BTU's. With 2 parts recycled liquefied
biomass (the produced oil) and two parts wood by weight,
approximately one part of new oil was produced (i.e., oil in
addition to that re-circulated back to mix with new feedstock).
EXAMPLE 2
[0038] A run similar to Example 1 was performed, except with dried
grass as the feedstock. The ratio of 2/2 (oil/feedstock) gave 3
parts oil, with 2 parts oil returned to mix with the feedstock
biomass and one part stored for combustion as a fuel. The oil had a
heat of combustion of 12,700 BTU's.
EXAMPLE 3
[0039] A mixture of 2 parts wood (dry pine) and 1 part
re-circulated bio oil gave 1 part of new bio oil using a 28 mm
Werner & Pfleiderer twin screw extruder under the conditions
used in Example 1.
[0040] Note that in all cases, the oxygen level goes from
approximately 53% net weight in the solid biomass feedstock to
between 15 and 28% in the liquefied biomass (oil).
EXAMPLE 4
[0041] A repetition of the runs described in Examples 1-3 with a
low-shear screw and low compression ratio failed to make any
liquefied biomass, even at a barrel temperature of 650 F.
EXAMPLE 5
[0042] A repetition of the runs described in Examples 1-3 with
unsaturated fatty acids instead of re-circulating bio oil also
produced new oil, but not as efficiently.
EXAMPLE 6
[0043] A mixture of 49% liquefaction biomass oil, 1% tertiary butyl
peroxy benzoate (TBPB), and 50% white pine screened to feed a 1.25
inch Davis Standard extruder was heated to 170 F for 2 hours. The
mixture was then run through the extruder with a 4:1 compression
ratio and converted to an oil with a heat of combustion of 14,000
BTU's. With 2 parts recycled liquefied biomass (the produced oil)
and two parts wood by weight, approximately one part of new oil was
produced (i.e., oil in addition to that re-circulated back to mix
with new feedstock). Alternatively, the TBPB can introduced into
the high-shear area of the mixer as a coating prior to, or
concurrent with, the addition of the oil and wood.
[0044] Various changes in the details and components that have been
described may be made by those skilled in the art within the
principles and scope of the invention herein described in the
specification and defined in the appended claims. Therefore, while
the present invention has been shown and described herein in what
is believed to be the most practical and preferred embodiments, it
is recognized that departures can be made therefrom within the
scope of the invention, which is not to be limited to the details
disclosed herein but is to be accorded the full scope of the claims
so as to embrace any and all equivalent processes and products.
* * * * *