U.S. patent number 3,779,182 [Application Number 05/283,516] was granted by the patent office on 1973-12-18 for refuse converting method and apparatus utilizing long arc column forming plasma torches.
Invention is credited to Salvador L. Camacho.
United States Patent |
3,779,182 |
Camacho |
December 18, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
REFUSE CONVERTING METHOD AND APPARATUS UTILIZING LONG ARC COLUMN
FORMING PLASMA TORCHES
Abstract
A method and apparatus are disclosed which are based on
utilizing a plural number of long arc column forming plasma torches
in combination with a refractory lined furnace chamber to
continuously pyrolyze household and industrial refuse material fed
into the chamber and convert the same to usable materials and
useful forms of energy.
Inventors: |
Camacho; Salvador L. (Raleigh,
NC) |
Family
ID: |
23086420 |
Appl.
No.: |
05/283,516 |
Filed: |
August 24, 1972 |
Current U.S.
Class: |
110/234; 110/243;
219/75; 110/250; 219/121.11 |
Current CPC
Class: |
F23G
5/085 (20130101); C03B 5/025 (20130101); C10B
53/00 (20130101); C03B 5/005 (20130101); C10B
19/00 (20130101); F23G 2204/201 (20130101); Y02E
50/30 (20130101); Y02W 10/30 (20150501) |
Current International
Class: |
C10B
53/00 (20060101); F23G 5/08 (20060101); C03B
5/02 (20060101); C03B 5/00 (20060101); C10B
19/00 (20060101); F23g 005/12 () |
Field of
Search: |
;110/8R,8E,18C,8C,18E
;219/121,72-75,383 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sprague; Kenneth W.
Assistant Examiner: Yuen; Henry C.
Claims
What is claimed is:
1. An apparatus for reducing by pyrolysis raw unsegregated refuse
comprising:
a. a furnace chamber;
b. a refractory lined hearth in said furnace chamber;
c. conveyor means adapted to introduce raw unsegregated refuse, at
least a portion of which is metallic, into said furnace chamber;
and
d. long arc column forming plasma generator means mounted in said
chamber and adapted to initiate and sustain at least one long arc
column plasma having a portion thereof in electrical contact with
said refuse and being adapted to reduce said refuse to gaseous and
molten fluid products by utilization of the column heat.
2. The apparatus of claim 1 including gas supply means adapted to
contact and chemically react with said gaseous and molten fluid
products.
3. The apparatus of claim 2 including energy conversion means
adapted to recover energy from said products.
4. The apparatus of claim 2 wherein said gas supply means comprises
an oxidizing supply.
5. The apparatus of claim 1 wherein said generator means comprises
a plurality of peripherally spaced generators and including
electrical circuit means adapted to initiate a pilot arc in each
said generator and enabling a main long arc column to be
transferred between at least two said generators and said
refuse.
6. The apparatus of claim 1 including groundable electrode means
included in said hearth and being adapted to enable a long arc
plasma column to be generated between at least one said generator
and said grounded electrode.
7. A method for reducing by pyrolysis a volume of raw unsegregated
refuse comprising:
a. initially charging a furnace chamber with refuse materials of
which a substantial portion is metallic;
b. providing long plasma arc column generation means extending
through at least one wall portion of said furnace chamber;
c. establishing and maintaining at least one long plasma arc column
between said generation means and said refuse thereby reducing by
heat at least said metallic refuse portion to a molten state;
d. conveying additional raw unsegregated refuse into said furnace
chamber; and
e. pyrolyzing all of said raw unsegregated refuse by heat from said
long plasma arc column into molten and gaseous products.
8. The method of claim 7 including chemically reacting a selected
gas with said molten and gaseous products.
9. The method of claim 8 wherein said gas comprises an oxidizing
gas.
10. The method of claim 7 including the step of recovering energy
from said products.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This invention is related to copending application, Serial No.
283,552, entilted "Trough Hearth Construction And Method For Plasma
Arc Furnace," which discloses an electric circuit for initiating
and sustaining long arc plasma columns utilizing long arc column
forming plasma generators or "torches" of the type previously
taught in U.S. Pat. No. 3,673,375, entitled "Long Arc Column Plasma
Generator and Method," issued to the same inventor.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and apparatus for reducing
the physical weight and volume of refuse by subjecting it to direct
radiated and convected heat from a long plasma arc column.
2. Description of the Prior Art
Pyrolysis (or destructive distillation) techniques were until very
recently unrecognized as a means for converting municipal and
industrial refuse into useful solid, liquid and gaseous products.
In the past, conventional incinerators have been widely used to
reduce refuse to ash through combustion. This process necessarily
introduced fly ash and many other types of airborne pollutants into
the atmosphere, due to the tremendous amounts of air utilized to
effect combustion. As an alternate measure, sanitary landfills were
developed to prevent air pollution. It is now recognized, however,
that water leaching through such landfills may constitute a
pollutant to ground water. It is a well-known and documented fact
that refuse contains both combustible and non-combustible
materials. The University of California, as a result of a study
analyzing municipal refuse, has stated that the composition of
municipal "mixed" (unsegregated) refuse by weight is: cans, 9.8
percent, bottles and glass, 11.7 percent; metals (other than cans)
0.9 percent; other 77.6 percent. (See University of California
Technical Bulletin No. 9, Sanitary Engineering Laboratory 1973
American Public Works Association, "Municipal Refuse Disposal"). It
is also a well-known fact that the non-combustible portion which
approximates 25 percent of the total weight of refuse is never
appreciably reduced by either conventional incineration or landfill
practices. Typically, these items are either shredded and buried at
the landfill or are simply heaped near the incinerator.
In its 1970 study entitled "Conversion of Municipal and Industrial
Refuse into Useful Materials by Pyrolysis," the United States
Department of the Interior, Bureau of Mines, revealed the
usefulness of pyrolyzing refuse and obtaining usable solid, liquid,
and gaseous products. In this study, various samples of shredded
municipal and industrial refuse with the metallic component largely
removed were placed in a sealed retort and subjected to various
levels of conducted heat to as much as 900.degree. centigrade.
Among the resulting products were solid residue (a source of
charcoal briquettes and filter medium), propane, ethylene and
methane gas, solid ammonium sulphate, tar, light oil (a soure of
benzene and toluene) and liquor 95 percent water and the remainder
formed of acids, ketones and aldehydes). In terms of recoverable
heat energy, the products of pyrolysis of refuse produced more than
a sufficient Btu content to provide the heat for pyrolysis. (See W.
S. Sanner et al.: "Conversion of Municipal and Industrial Refuse
into Useful Materials by Pyrolysis," Report of Investigations No.
7428, U. S. Department of the Interior, Bureau of Mines, August,
1970.)
Although the study conducted by the Bureau of Mines was
instrumental in determining the potential value of converting
refuse into usable products by pyrolysis, it did not suggest an
efficient method and apparatus to do so. The system used was based
upon a "batch" method of charging the retort and did not suggest a
method and apparatus for more efficient continuous operation.
Furthermore, the solid residue contained bottle caps and bits of
metal which required further separation before the solid residue
could be utilized. In addition, the bulk of the metallic refuse
component was required to be segregated from the combustible or
carbonaceous component prior to pyrolysis, and the combustible
component required drying and shredding for maximum efficiency of
the process.
Additional prior art has suggested the use of conventional
arc-forming electrodes in an incinerator in U.S. Pat. No. 3,503,347
to intermittantly generate heat and thereby reduce the volume and
weight of waste confined inside the incinerator. The above patent
does not, however, teach the continuous operation of such an
incinerator and does not teach a practical application of the
evolved noxious gases. In general, the prior art has not suggested
an efficient method and apparatus utilizing long arc column plasma
torches for reducing substantially large amounts of unsegregated
refuse to usable and valuable products from which energy may be
readily obtained, while at the same time not polluting the
environment. Furthermore, the prior art has not suggested such a
method and apparatus which would be adapted for continuous rather
than batch operation and capable of reducing the physical weight
and volume of substantially large amounts of refuse while
generating more energy than being consumed.
SUMMARY OF THE INVENTION
This invention utilizes a plurality of long arc column forming
plasma torches in combination with a furnace chamber to thermally
decompose unsegregated refuse into a gaseous and molten fluid
state. Conveyor means are adapted to continuously supply refuse to
the furnace chamber while smoke recycling means are adapted to
prevent the gases being produced within the chamber from escaping.
The furnace chamber is formed so as to have a somewhat bowl-shaped
refractor lined interior hearth portion into which the long arc
forming plasma torches are directed. The hearth portion further
includes a normally electrically disconnected graphite electrode
but which may be appropriately connected into the electrical
circuit when needed as an electrode. A lip formed along one edge of
the refractory material provides a fluid outlet for the molten
refuse. Pyrolysis of the refuse proceeds as long arc plasmas are
generated between the various torches residing in vertical wall
portions of the furnace chamber, and molten metallic portions of
the refuse collects in the hearth. The heat radiated and convected
from the generated long arc plasma columns is sufficient to reduce
the remaining organic and non-combustible portion of the refuse to
either a molten or gaseous state. Some of the evolved gases rise,
preheat the refuse and are then reintroduced into the reduction
process. In a preferred embodiment as the molten refuse reaches the
level of the outlet lip it is oxidized by an incoming stream of
gas, e.g., air. The oxidized molten refuse then enters a water bath
which effectively provides a water seal and forms into a solid slag
for later recovery by appropriate handling means. In some instances
the slag may be maintained heated for purposes of molding the same.
The gaseous products of the pyrolyzed refuse are simultaneously
converted into saturated steam and other gases which may be
neutralized or combusted by introduction of gases other than the
mentioned air. The hot gases may then drive appropriate energy
conversion means such as a turbine generator and may be scrubbed or
otherwise purified before being released to the atomosphere.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional side view of a typical refuse
converting apparatus according to the invention.
FIG. 2 is a cutaway side view of a long arc column forming plasma
torch employed in the instant invention generally shown in
operating position inside a furnace chamber.
FIG. 3 is a top plan view of a refuse converting apparatus
according to the invention.
FIG. 4 is a somewhat schematic diagram of an electrical circuit
employed in the instant invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, as previously mentioned, the present invention
is directed to an apparatus and method for continuously reducing by
pyrolysis the physical weight and volume of municipal and
industrial refuse material and converting it into energy,
recoverable and useful products, utilizing long arc column plasma
generators, also known in the art as plasma torches. In a preferred
embodiment, a complete refuse converting apparatus includes a
furnace chamber 15; a plurality of directionally stable long arc
column forming plasma torches, generally designated 12, of the type
disclosed in previously referred to U.S. Pat. No. 3,673,375,
projecting through selected apertures 11 in vertical walls 14 of
said furnace chamber 15. Also included is a somewhat concave
refractory lined furnace hearth 17 having an integrally formed
graphite electrode 18. Said refuse converting apparatus is also
provided with a refuse hopper 20 including sealed refuse conveying
means 21 and smoke recovery means 23, together being adapted to
continuously feed refuse materials 25 into said furnace chamber 15,
while maintaining smoke and noxious gases within the chamber. The
term "refuse" as used in this disclosure includes raw unsegregated
refuse of a municipal or industrial nature or any mixture of both.
By "unsegregated" what is meant is that organic wastes are mixed
with tin cans, bottles, paper, etc.
In accordance with the instant invention during operation, later
described in greater detail, each plasma torch 12 is adapted to
form a transferred long arc column of from 10 to 40 inches with
molten refuse material 19 a portion of which is metallic. Due to
the intense heat being generated (1,000.degree. to 2,000.degree.K),
the non-molten refuse (represented by dashed lines 22) is rapidly
pyrolyzed into gaseous and molten fluid components in the absence,
at this point, of appreciable combustion.
Hot gases and molten refuse evolved from the heat of the arc
columns flow past a lip 16 formed in the concave refractory lined
hearth 17 and into an oxidation chamber 30 which includes a gas
inlet manifold 31 for oxygen or air which enables the evolved gases
to be combusted into an oxidation dioxide and steam vapor.
Depending on the nature of the refuse gases produced, gases other
than air or oxygen may be introduced to combust or neutralize such
refuse gases. Gas vent 32 receives the hot combusted vapor while a
water bath 33 receives the molten residue and reduces it into a
solidified slag material 38. The solidified slag aggregate is a
highly salable item due to its silica and metallic content. A ridge
of molded refractory material 34 adjacent lip 16 further enhances
combustion and further degradation of the molten refuse by
increasing the surface area over which the refuse is exposed to
oxidation. The action of the water seal with the molten refuse
serves to generate additional steam. A turbine generator 35, for
example, may receive the hot gases entering gas vent 32 and be used
to generate more electrical power than is consumed by the torches.
Appropriate gas treatment means (not shown) receive and scrub the
combusted gases until safe for release to atmosphere. Alternately,
selected valuable gases, e.g., methane, may be separated by
well-known means before being combusted by withdrawing a portion of
the gas by appropriate means (not shown). The now solidified slag
38 may be handled by appropriate blade or other suitable conveyor
means 60 and finally withdrawn from the water bath by additional
handling apparatus 61 for later use.
Referring to FIG. 2, a long arc column plasma torch, according to
the invention and as previously taught in U.S. Pat. No. 3,673,375,
is defined as being an apparatus and an electrical conductor in the
arc circuit and includes a cylindrical shaped electrode 36, a gas
directing nozzle 37 axially aligned with, forwardly spaced and
insulated from electrode 36, and appropriate gas and electrical
supply means (not shown). As previously disclosed in copending
application, Ser. No. 283,552 a "pilot arc" indicated by dashed
lines 45, may be struck between electrode 36 and nozzle 37 by
introducing a current potential therebetween while simultaneously
applying a vortical flow of gas directed outward through said
nozzle 37. Such a pilot arc is readily transferred to a metallic
material 46 also in the electrical circuit when such pilot arc 45
becomes proximate said metallic matter (i.e., 4-7 inches) by
appropriately advancing said torch 12 into a position proximate
said metallic refuse 46. In the instant invention, it has been
recognized that such a long arc column plasma torch has particular
effectiveness in a refuse converting apparatus since one component
(typically 25 percent) of refuse is metal.
Referring now to FIG. 3, a first long arc column plasma torch 40,
in preferred form, is adapted to extend through an aperture 47 in a
portion of a rear wall 51 of said furnace chamber 15 while second
41 and third 42 long arc column plasma torches are adapted to
extend through apertures 48, 49 in adjacent corner wall portions 52
of said furnance chamber. As is perhaps apparent, many other torch
mounting configurations will appear to those skilled in the art,
and the particular mounting details described herein are for
purposes of example only. A sleeve or collar 53 (FIG. 2) which may
be stainless steel, for example, lining each respective aperture
47, 48, 49 is adapted to enable horizontal and vertical angular, as
well as axial, movement of each plasma torch within its respective
mounting position while preventing heat and noxious gases from
escaping through apertures 47, 48, 49. Remotely controllable torch
positioning means 24 (FIG. 1) are provided to enable accurate
positioning of the plasma torches.
Referring now to FIG. 4, as previously mentioned, each long arc
column forming plasma torch utilized in the present invention
(shown in cross section) includes a cylindrical shaped internal
electrode 36 and a gas directing nozzle 37 axially aligned with,
forwardly spaced and insulated from electrode and appropriate gas,
water and electrical supply means (not shown). while the last
mentioned gas and water supply means are considered
well-established in the art requiring no further elaboration
herein, a better understanding may be gained of the invention by a
discussion of its advantageous use of power in starting and
maintaining the various long arc plasma columns. Utilizing a three
phase A. C. wye 55 having a floating neutral 56 to conveniently
supply power to three long arc column forming plasma torches 12, a
given torch internal electrode 36 is connected to an individual
current phase. It is apparent that if more than three torches are
employed, a greater number of phases may be utilized. Each torch
nozzle 37 is connected to an adjacent phase 58 via an appropriate
choke 59. In this manner, a "pilot arc" 45 may be struck between
the nozzle 37 and internal electrode 36 of each torch without
introducing a consumable electrical conductor by applying the phase
to adjacent phase voltage differential, caused by choke 59, across
internal electrode 36 and nozzle 37 and by simultaneously
introducing a gas vortical flow through nozzle 37. The current
passing through the "pilot arc" 45 is substantially smaller than
that of the "main arc" 13 (see FIGS. 1 and 2) which is subsequently
adapted to be transferred to the metal scrap to be melted.
Simultaneous transferral of at least two "pilot arcs" 45 to the
metallic refuse component establishes at least two main transferred
arcs (not shown) and completes a phase 57 to adjacent phase 58 loop
whereby the full available current is now utilized.
Since the nature and physical arrangement of the refuse with
respect to the torches will vary widely during operation it is
contemplated that one or more torches may become inoperable. For
example, a falling porcelain coated refrigerator or a sudden deluge
of rotten vegetables may stifle an arc. In this event, any single
torch may be operated phase to neutral and a new plasma column path
may be established by restarting with a pilot arc. Thus, when
contact with an electrically conductive melt or an electrically
conductive unmelted refuse is lost to a particular plasma column
connection may be made to graphite electrode 18 to a ground or
neutral 79 (FIG. 1) by a suitable manual or remotely operated
contactor 78. Once a molten metallic pool is reestablished the
other torches may be again utilized.
Once a molten pool 19 of metallic refuse has been formed and
preferably all long arc plasma columns 13 have made electrical
contact with said molten pool, it is possible to then continuously
dump unsegregated refuse 25 into the furnace chamber 15. The small
molten metallic component of the unsegregated refuse will then be
sufficient to sustain electrical connection between the three
plasma arcs. Furthermore, the above described method of operating
long arc column plasma torches in electrical connection with a
molten pool of metallic refuse 19 assures continuous operation of
the furnace since the metal having a higher specific gravity than
the bulk of other refuse will tend to remain in the concave
refractory lined hearth 17 while the continuously melting mixed
metallic-non-metallic refuse will tend to flow out of the concave
furnace hearth 17, pass the outlet lip 16 through oxidation chamber
30 and into water bath 33. It is also a recognized advantage of the
particular embodiment shown to utilize the hot gases being evolved
in the furnace chamber to pre-heat refuse materials 25 entering the
furnace thereby promoting even greater efficiences. Based on the
foregoing invention operation parameters, the specific furnace
design and construction is deemed well within the established
electric arc furnace art and therefore requires no further
elaboration here. While specific refuse conveying means, material
handling and energy recovery means have been suggested, these
aspects of the instant invention are also well-known in the
established art. A complete but not definitive method of converting
refuse into usable energy recoverable products based on the
described invention may include:
a. initially charging a furnace built in accordance with the
invention with refuse having a high metallic content;
b. initiating and sustaining a plurality of long arc plasma columns
and reducing the largely metallic refuse to a molten pool;
c. conveying refuse of any class or mixture into the furnace;
d. reducing by heat pyrolysis the physical weight and volume of
said conveyed refuse into molten fluid and gaseous products;
e. converting the evolved molten fluid and gaseous products to
usable energy;
f. treating and purifying the final products before returning them
to the atmosphere.
On the basis of the foregoing description, it is apparent that the
instant invention provides an efficient and environmentally safe
alternative to landfill, and combustive incineration practices of
refuse disposal while at the same time providing a source for
energy through the use of long arc column forming plasma torches.
According to the invention, it is now possible to continuously
decrease the physical weight and volume of raw unsegregated refuse
while converting the evolved products to useful materials and
useful energy.
* * * * *