Waste material processing apparatus

A material processing apparatus includes a casing having a top and bottom and a plurality of sides defining a pyrolysis chamber for receiving and pyrolyzing feed materials therein into fluid materials and a mass of refractory material disposed upon the bottom of the casing and spaced below the top thereof and extending between its sides. The refractory mass includes an upper surface defining a bottom of the pyrolysis chamber and having an end spaced from a first one of the casing sides to define an ash residue collection cavity therebetween. The apparatus also includes a system of tunnels defined within the refractory mass being spaced below the upper surface thereof. The system of tunnels includes an inlet defined in the refractory mass at the end thereof and below the upper surface thereof and in communication with the cavity for receiving a flow of materials from the pyrolysis chamber into the system of tunnels and an outlet defined in a second one of the sides of the casing for discharging the flow of materials from the system of tunnels. The apparatus also includes elongated heater units mounted to sides of the casing and extending into and axially along selected ones of the tunnels in the system thereof.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention generally relates to material processing and, more 
particularly, is concerned with an apparatus for controlled processing of 
materials and a method of controlling hydrocarbon release rate by 
maintaining target oxygen concentration in discharge gases so as to 
thereby convert successive batches of materials of widely varying energy 
content into substantially harmless gases and carbon-free residue ash, 
such as is necessary for the disposal of medical and other diverse waste 
material, particularly on-site where the waste material is produced. 
2. Prior Art 
The problem of disposal of waste matter involves a material processing 
challenge that is becoming increasingly acute. The primary material 
processing methods of waste disposal have been burning in incinerators and 
burial in landfills. These two material processing methods have severe 
disadvantages. Burning of waste liberates particulate matter and fumes 
which contribute to pollution of the air. Burial of wastes contributes to 
the contamination of ground water. A third material processing method is 
recycling of waste. Although increasing amounts of waste are being 
recycled, which alleviates the problems of the two primary material 
processing methods, presently available recycling methods do not provide a 
complete solution to the waste disposal problem. 
The problem of disposal of biomedical waste materials is even more acute. 
The term "biomedical waste materials" is used herein in a generic sense to 
encompass all waste generated by medical hospitals, laboratories and 
clinics which may contain hazardous, toxic or infectious matter whose 
disposal is governed by more stringent regulations than those covering 
other waste. It was reported in The Wall Street Journal in 1989 that about 
13,000 tons a day of biomedical waste, as much as 20% of it infectious, is 
generated by around 6,800 U.S. hospitals. 
Hospitals and other generators of biomedical waste materials have employed 
three main material processing methods of waste handling and disposal: (1) 
on-site incineration with only the residue transferred to landfills; (2) 
on-site steam autoclaving and followed by later transfer of the waste to 
landfills; and (3) transfer of the waste by licensed hazardous waste 
haulers to off-site incinerators and landfills. Of these three main 
material processing methods, theoretically at least, on-site disposal is 
the preferred one. 
However, many hospital incinerators, being predominantly located in urban 
areas, emit pollutants at a relatively high rate which adversely affect 
large populations of people. In the emissions of hospital incinerators, 
the Environmental Protection Agency (EPA) has identified harmful 
substances, including metals such as arsenic, cadmium and lead; dioxins 
and furans; organic compounds like ethylene, acid gases and carbon 
monoxide; and soot, viruses, and pathogens. Emissions of these 
incinerators may pose a public health threat as large as that from 
landfills. 
Conventional incinerators most commonly are designed to operate above a 
certain temperature, such as 1200.degree.-1400.degree. F., to comply with 
requirements of the permit laws of many states. The reason for this 
requirement is that conventional thinking has been that operation of 
incinerators at such elevated temperatures will substantially eliminate 
the release of most harmful substances. This may have been true where the 
materials being consumed by the incinerator were assumed to be fairly 
uniform in terms of energy content and thus burned more or less evenly. 
However, this is the exception and not the normal situation today, 
particularly in the case of biomedical waste materials which can range 
from wet paper towels and steel surgery tools to plastic syringes and 
containers of saline solution. The thermal processing of these materials 
by temperature control alone will ordinarily result in the inability to 
control the hydrocarbon release rate and the repeated emission of 
un-burned hydrocarbons, typically visible as periodic puffs of black 
smoke, which is unacceptable under most current environmental regulations. 
Nonetheless, on-site disposal of biomedical waste materials still remains 
the most promising solution. One recent on-site waste disposal unit which 
addresses this problem is disclosed in U.S. Pat. No. 4,934,283 to Kydd. 
This unit employs a lower pyrolyzing chamber and an upper oxidizing 
chamber separated by a movable plate. The waste material is deposited in 
the lower chamber where it is pyrolyzed in the absence of air and gives 
off a combustible vapor that, in turn, is oxidized in the upper chamber. 
While this unit represents a step in the right direction, it does not 
appear to approach an optimum solution to the problem of biomedical waste 
material disposal. 
One problem with the approach of the aforementioned patent is that it 
proposes the use of an on-site waste disposal unit which is dedicated to 
the disposal of biomedical waste material. This approach requires that 
more than one incineration system be installed and maintained at 
hospitals, namely, one for biomedical waste and another for all other 
hospital waste. Resistance has been encountered to the adoption of this 
approach by hospitals due to added cost of installation, operation and 
maintenance. An urgent need has developed for an all-purpose material 
processing apparatus which can handle disposal of all types of hospital 
waste materials, both biomedical waste and general waste, such as metal 
needles and glass and plastic bottles. 
Reference is also made to the following issued U.S. Patents dealing with 
subject matter related to the present invention, the disclosures of which 
are hereby incorporated in their entireties: 
1. "Apparatus And Method For Controlled Processing Of Materials" by Roger 
D. Eshleman and Paul S. Stevers, assigned U.S. Ser. No. 07/987,928 and 
filed Dec. 9, 1992 and issued U.S. Pat. No. 5,353,719. 
2. "Multiple Unit Material Processing Apparatus" by Roger D. Eshleman, 
assigned U.S. Ser. No. 07/987,929 and filed Dec. 9, 1992, and issued U.S. 
Pat. No. 5,289,787. 
3. "Heat Generator Assembly In A Material Processing Apparatus" by Roger D. 
Eshleman, assigned U.S. Ser. No. 07/987,936 and filed Dec. 9, 1992, and 
issued U.S. Pat. No. 5,338,918. 
4. "Casing And Heater Configuration In A Material Processing Apparatus" by 
Roger D. Eshleman, assigned U.S. Ser. No. 07/987,946 and filed Dec. 9, 
1992, and issued U.S. Pat. No. 5,420,394. 
5. "Apparatus And Method For Transferring Batched Materials" by Roger D. 
Eshleman, assigned U.S. Ser. No. 08/026,719 and filed Mar. 5, 1993, issued 
U.S. Pat. No. 5,338,144. 
6. "Sloped-Bottom Pyrolysis Chamber And Solid Residue Collection System In 
A Material Processing Apparatus" by Roger D. Eshleman, assigned U.S. Ser. 
No. 08/299,034 and filed Sep. 17, 1993, issued U.S. Pat. No. 5,417,170. 
7. "Material Transport Pusher Mechanism In A Material Processing Apparatus" 
by Roger D. Eshleman, assigned U.S. Ser. No. 08/123,747 and filed Sep. 17, 
1993, issued U.S. Pat. No. 5,361,709. 
8. "Improved Casing And Heater Configuration In A Material Processing 
Apparatus" by Roger D. Eshleman, assigned U.S. Ser. No. 08/123,454 and 
filed Sep. 17, 1993, issued U.S. Pat. No. 5,428,205. 
9. "Method of controlling hydrocarbon release rate by maintaining target 
oxygen concentration in discharge gases" by Paul H. Stevers, assigned U.S. 
Ser. No. 08/283,118 and filed Jul. 29, 1994, issued U.S. Pat. No. 
5,501,159. 
SUMMARY OF THE INVENTION 
The present invention provides a diverse material processing apparatus 
designed to satisfy the aforementioned needs. While the apparatus of the 
present invention can be used in different applications, it is primarily 
useful as an apparatus for waste disposal and particularly as an apparatus 
for disposing of biomedical and general hospital waste material on-site 
where the waste material is produced. A greater than 95% reduction in mass 
and volume is achieved as is the complete destruction of all viruses and 
bacteria. The residue is a sterile, inert inorganic powder, which is 
non-hazardous, non-leachable and capable of disposal as ordinary trash. 
The preferred embodiment of the present invention includes various unique 
features for facilitating the processing of material and particularly the 
disposing of diverse waste material. Although some of these features may 
form a part of the inventions claimed in the patents cross-referenced 
above, these features are illustrated and described herein for 
facilitating a complete and thorough understanding of those features 
comprising the present invention. 
Accordingly, the present invention is directed to a material processing 
apparatus which generally comprises: (a) a casing having a top, a bottom 
and a plurality of sides defining a pyrolysis chamber for receiving and 
pyrolyzing feed materials into fluid materials and including an upper 
portion for temporarily receiving the fluid materials and wherein at least 
one of the plurality of sides includes a down-draft duct having (i) an 
entrance positioned in flow communication with the upper portion of the 
pyrolysis chamber, and (ii) an exit spaced from the entrance; (b) a mass 
of refractory material contained in the casing and spaced below the top 
and extending between the sides, the refractory mass including an upper 
surface defining a bottom of the pyrolysis chamber and having an end being 
spaced from a first one of the sides of the casing so as to define an ash 
residue collection cavity; and (c) a system of tunnels defined within the 
refractory mass and spaced below the upper surface thereof, the system of 
tunnels including at least one inlet defined in the refractory mass 
adjacent to an end thereof and below the upper surface and in flow 
communication with the exit of the down-draft duct so as to receive a flow 
of the fluid material from the pyrolysis chamber into the system of 
tunnels and an outlet defined in a bottom of the casing for discharging 
the flow of materials from the system of tunnels. 
In one preferred embodiment, the system of tunnels includes (a) a pair of 
spaced upper tunnels, each one of the pair of upper tunnels being disposed 
in flow communication with an inlet in a side of the refractory mass, (b) 
a lower tunnel, space below the pair of upper tunnels and arranged in 
transverse relation thereto and adjacent to an end of the refractory mass, 
(c) means for interconnecting the pair of upper tunnels in flow 
communication with the transverse lower tunnel, and (d) a middle tunnel 
arranged in open flow communication with the transverse lower tunnel and 
the outlet. The middle tunnel is adapted to form a hot gas trap. 
In another preferred embodiment, means positioned adjacent to the upper 
surface of the refractory mass, are provided for selectively stirring the 
ash residue and at preselected times for removing ash residue from the 
upper surface. The means for stirring and removing comprise at least two 
degrees of freedom of movement. One exemplary structure includes a pair of 
blades that are each fixedly fastened to an end of a spaced pair of 
movable shafts. The blades and shafts comprise at least two degrees of 
freedom of movement, i.e., linear translation and angular rotation, so 
that the blades may be selectively positioned and oriented relative to the 
upper surface of the refractory mass for selectively stirring ash residue, 
and at preselected times, for removing the ash residue from the upper 
surface and into the ash collection cavity. 
In a further preferred embodiment, the upper surface of the refractory mass 
includes an undulant contour such that at least a pair of elongate, 
concave surface depressions are separated by at least one elongate convex 
surface. 
In yet another preferred embodiment, the ash residue collection cavity that 
is disposed at a bottom of the casing, beside a lower portion of the 
refractory mass, includes a bake-out trough and a cool-down trough. The 
bake-out trough and cool-down trough each comprise a concave upper surface 
defining a channel. These channels are arranged in longitudinal alignment 
with one another so as to form an elongate concave surface. The cool-down 
trough is disposed outwardly of the refractory mass at a bottom side of 
the casing so as to be positioned in a lower temperature portion of the 
casing. An outlet is defined at a distal end of the channel for 
discharging cooled ash residue into a receptacle. Means are positioned 
adjacent to an end of the concave surface of the bake-out trough and 
spaced from the cool-down trough for selectively stirring the ash residue 
that has collected therein, and at preselected times, for removing the ash 
residue from the bake-out trough to the cool-down trough and for pushing 
the ash residue into the discharge outlet. The means for stirring and 
removing comprise at least two degrees of freedom of movement. One 
exemplary structure includes a blade fixedly fastened to an end of a 
movable shaft. The blade and shaft comprise at least two degrees of 
freedom of movement, i.e., linear translation and angular rotation, so 
that the blade may be selectively linearly positioned and angularly 
oriented relative to the channel of the bake-out trough and spaced from 
the cool-down trough for selectively stirring the ash residue, At 
preselected times, the blade and shaft can be oriented and linearly 
advanced for removing the ash residue from the bake-out trough to the 
cool-down trough, and then into the discharge outlet. 
The present invention also provides a method of controlling hydrocarbon 
release rate in thermal processing of materials which is designed to 
overcome the aforementioned problems of conventional incineration. The 
hydrocarbon release rate is controlled in a manner which converts 
successive batches of materials, particularly biomedical waste materials, 
of widely varying energy content into substantially harmless gases and 
carbon-free residue ash. The residue ash is a sterile, inert inorganic 
powder, which is non-hazardous, non-leachable and capable of disposal as 
ordinary trash. 
Accordingly, the present invention is also directed to a method of 
controlling the hydrocarbon release rate in the thermal processing and 
conversion of materials of widely varying energy content in a batch 
processing cycle. The hydrocarbon release rate controlling method 
comprises the steps of: (a) providing a first chamber capable of receiving 
successive batches of feed materials for thermal processing and having 
widely varying energy content; (b) producing heating in the first chamber 
to cause pyrolyzing of the feed materials into fluid materials; (c) 
providing a second chamber communicating with the first chamber and 
capable of receiving the fluid materials from the first chamber and 
communicating the fluid materials to a discharge location; (d) producing 
heating in the second chamber to cause oxidizing of the fluid materials 
into discharge gases reaching the discharge location; (e) providing a 
jacketed vessel defining a channel surrounding the first and second 
chambers containing a flow of coolant fluid through the channel; (f) 
producing separate variable flows of primary and secondary air 
respectively into and through the first and second chambers; (g) sensing 
the temperatures in the first and second chambers; (h) sensing the 
temperature of the coolant in the channel of the jacketed vessel; (i) 
sensing the concentration of a preselected gas in the discharge gases; (j) 
in response to the temperatures sensed in the first and second chambers 
and jacketed vessel channel coolant and in response to the concentration 
of the preselected gas sensed in the discharge gases, controlling primary 
and secondary flows of air into the first and second chambers so as to 
proportion and vary the respective amounts thereof and thereby maintain 
concentration of the preselected gas in the discharge gases at a preset 
target corresponding to the generation of substantially harmless discharge 
gases and production of substantially carbon-free residue ash; and (k) in 
response to the temperatures sensed in the first and second chambers and 
in the jacketed vessel channel coolant and in response to the 
concentration of the preselected gas sensed in the discharge gases, 
selectively stirring an ash residue collected within said first chamber 
according to a predetermined pattern so as to thereby maintain the 
concentration of the preselected gas in the discharge gases at a preset 
target level corresponding with the generation of substantially harmless 
discharge gases and production of substantially carbon-free residue ash. 
The preselected gas is preferably oxygen. 
The method also includes the step of mechanically stirring the ash residue 
collected in a bake-out trough located in an ash residue collection cavity 
within the first chamber. mass. 
These and other features and advantages and attainments of the present 
invention will become apparent to those skilled in the art upon a reading 
of the following detailed description when taken in conjunction with the 
drawings wherein there is shown and described illustrative embodiments of 
the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the following description, it is to be understood that such terms as 
"forward", "rearward", "left", "right", "upwardly", "downwardly", and the 
like, simply refer to the orientation of the structure of the invention as 
it is illustrated in the particular views shown in the drawings when the 
specific figure faces the reader. Similarly, the terms "inwardly" and 
"outwardly" generally refer to the orientation of a surface relative to 
its axis or elongation, or axis of rotation, as appropriate. Also, the 
terms "connected" and "interconnected", when used in this disclosure to 
describe the relationship between two or more structures, means that such 
structures are secured or attached to each other directly or indirectly 
through intervening structures, and includes pivotal connections. The term 
"operatively connected" means that the foregoing direct or indirect 
connection between structures allows such structures to operate as 
intended by virtue of such connection. 
Referring now to the drawings, and particularly to FIGS. 1-4, there is 
illustrated an exemplary apparatus 1 for controlled thermal processing of 
waste materials 3, and in particular for controlled disposal of biomedical 
waste materials, which is operated in accordance with a hydrocarbon 
release rate controlling method. Material processing apparatus 1 basically 
includes a coolant jacketed vessel 5 defining at least a first pyrolysis 
chamber 10. A second, oxidation chamber and main heat exchanger 400 are 
also enclosed by coolant jacketed vessel 5, and are more fully disclosed 
in the foregoing cross-referenced patents. The apparatus also includes one 
or more first heater units 25 having a plurality of elongated rod-like 
electric heating elements mounted in the vessel and being operable to 
electrically generate heat for pyrolyzing materials in first chamber 10, 
and one or more second heater units 27 having a plurality of electric 
heating elements mounted in the vessel and being operable to electrically 
generate heat materials in second chamber 20. 
The apparatus further includes an air flow generating means, preferably an 
induction fan and a fan speed controller (indicated generally at 30), 
connected in flow communication with first chamber 10 and second chamber 
20, and first and second airflow inlet valves 33, 36 connected to jacketed 
vessel 5. The apparatus also includes an air intake proportioning valve 
(not shown) connected in flow communication with the first and second air 
inlet valves. Induction fan 30, the proportioning valve, and first and 
second inlet valves 33, 36 function to produce separate primary and 
secondary variable flows of air respectively into and through first 
chamber 10 and second chamber 20. One suitable embodiment of the fan speed 
controller is a commercially-available unit identified as GPD 503 marketed 
by Magnetek of New Berlin, Wis. One suitable embodiment of the valves is 
disclosed in U.S. Pat. No. 4,635,899, the disclosure of which is 
incorporated herein by reference. One suitable embodiment of the 
proportioning valve is a pair of conventional air intake butterfly valves 
controlled by a standard proportioning motor marketed by the Honeywell 
Corporation. The respective amounts of air in the primary and secondary 
flows drawn through the first and second chambers by operation of the 
induction fan are proportioned by the operation of the proportioning valve 
to separately adjust the ratio of the amounts of air flow routed to the 
first and second air inlet valves 33, 36. The respective amounts of air 
drawn in the primary and secondary flows are correspondingly varied by 
varying the speed of operation of the induction fan. 
At least three temperature sensors 37, 38, 39 (FIG. 33) such as 
conventional thermocouples, are mounted on vessel 5 for sensing 
temperatures in first chamber 10 and second chamber 20, and in the coolant 
circulating about a channel 40 (FIG. 4) defined by jacketed vessel 5 about 
first chamber 10 and second chamber 20. Additionally, a gas sensor 42 
(FIG. 33) is mounted on a discharge outlet of vessel 5 for sensing the 
concentration of a predetermined gas, for example oxygen, in the discharge 
gases. Also, a computer-based central control system 44 (FIG. 33) is 
incorporated in the apparatus for controlling and directing the overall 
operation of the apparatus in accordance with a hydrocarbon release rate 
controlling method. One suitable computer which can be employed by the 
control system is a PC-55 marketed by the Westinghouse Electric 
Corporation of Pittsburgh, Pa. 
For many applications, material processing apparatus 1 can be provided in 
the form of a single unit where all components of the apparatus are 
contained within the one unit. However, in order to accommodate space and 
installation requirements, there are other applications where material 
processing apparatus 1 needs to be provided in the form of two separate 
first and second units. Still referring to FIGS. 1-4, material processing 
apparatus 1 includes a casing 47 having an outer wall 51 and an inner wall 
53 disposed in spaced, confronting relation to one another, thus forming a 
coolant jacketed, airtight pressure vessel 5 inside of inner wall 53, with 
channel 40 defined between outer and inner walls 51, 53. Channel 40 
surrounds vessel 5 and contains a flow of coolant fluid, such as water. 
The above-identified related patents show examples of the circulation flow 
path of coolant fluid about similar vessel channels. As mentioned above, 
vessel 5 is separated into first and second units and has means in the 
form of a pair of tubular extensions of the outer and inner walls which 
are fastened together to interconnect the first and second units in flow 
communication with one another. 
Referring to FIGS. 4-10, vessel 5 defines first pyrolysis chamber 10 having 
an inlet 60 and second oxidation chamber 20 connected in communication 
with first pyrolysis chamber 10 and having a discharge outlet 80. First 
chamber 10, in which waste materials 3 will be pyrolyzed, receives 
materials through inlet 60, via operation of an automatic feeding system 
65. Material 3, through pyrolysis, or burning in a starved oxygen 
atmosphere, is converted to a gas that tends to congregate in an upper 
portion 68 of first chamber 10. This gas exits first chamber 10 by passing 
into an entrance 70 disposed in inner walls 53, and flows through a 
down-draft duct or conduit 72 into and through a system of tunnels 73 
formed in a refractory mass 75 (FIGS. 5 and 6). It should be understood 
that in some of the various cross-sectional views of apparatus 1, only one 
down-draft duct or conduit 72 can be seen, however, a preferred embodiment 
of the invention will comprise two such down-draft ducts 72 disposed in 
confronting relation to one another in opposing portions of inner wall 53 
and outer wall 51, so that a down-draft duct or conduit 72 will be 
positioned on each side of refractory mass 75 (see FIG. 10). Second 
chamber 20 receives the pyrolyzed materials from first chamber 10 and, 
after oxidizing the pyrolyzed materials therein, discharges the oxidized 
materials therefrom through discharge outlet 80. 
Referring to FIGS. 5-10, a series of passages or tunnels 73 are defined in 
mass of refractory material 75. As the pyrolyzed gas flows down through 
each down-draft duct or conduit 72 from upper portion 68 of pyrolysis 
chamber 10, it enters a respective upper tunnel 82, defined in refractory 
mass 75. The gas enters refractory mass 75 through an inlet opening 74 
defined in each side of refractory mass 75, adjacent to an exit opening 76 
(FIG. 10) of one of the down-draft ducts or conduits 72. The gas passes 
through each upper tunnel 82 toward a transverse lower tunnel 85. The gas 
then flows toward the middle of refractory mass 75 until it enters a 
middle tunnel 87 that forms an inner trap or chamber 20. Chamber 20 
typically houses gas at a temperature of from about 2,000.degree. F. to 
about 2,200.degree. F., whereas primary chamber 10 contains gases at a 
temperature of from 300.degree. F. to 600.degree. F. The hot gas then 
flows toward discharge opening 80 where the oxidized gas passes down to a 
lower tunnel, where further turbulence is generated by a series of 
vertically oriented rods disposed within opening 80, after which the gas 
flows to the second unit. 
The series or arrangement of tunnels 73 formed in refractory mass 75 define 
the primary section of chamber 20, and provide communication with the 
first chamber 10, via down-draft ducts or conduits 72, disposed within the 
side walls of chamber 10. Refractory mass 75 is, of course, surrounded by 
jacketed vessel 5 and maintained in a heated condition at elevated 
temperatures by the heating produced in the first chamber by the first 
heater units 25 and by the pyrolyzing and oxidizing of materials 3. 
Middle tunnel 87 defines chamber 20 where hot gas (2,000-2,200.degree. F.) 
from in the lower section of refractory mass 75 is trapped, and prevented 
from flowing back up into pyrolysis chamber 10. Hot gas from chamber 20 
could explode, under certain conditions, if it were to mix with the higher 
oxygen content, lower temperature gasses located in upper portion 68 of 
pyrolysis chamber 10. For example, if there is a rapid shut down of 
apparatus 1 (e.g., a power outage) where the induction fan is turned off, 
then, after a while, gasses in the pyrolysis chamber cool down due to the 
cooling effect of the water flowing in channel 40 of vessel 5. In this 
situation, the lower, hotter gas located in chamber 20 of refractory mass 
75 would normally tend to flow upwardly, and could mix with oxygen in 
chamber 10. It being understood that the lower, hotter gas in chamber 10 
is oxygen depleted, whereas the upper cooler gas is, relatively, oxygen 
rich. However, the trap created by chamber 20 of middle tunnel 87 prevents 
hot gases from moving back up through down-draft ducts or conduits 72, due 
to the difference in density between the gasses in upper portion 68 and 
chamber 20, among other factors. As a result, the lower, hotter gas will 
tend to remain trapped in chamber 20 of middle tunnel 87, and not move 
back up through down-draft ducts or conduits 72 and into pyrolysis chamber 
10. 
Refractory mass 75 also includes an upper exterior surface 100 which is 
exposed to first chamber 10 and below which resides system of tunnels 73. 
Upper surface 100 comprises an undulant contour that, in transverse 
cross-section (FIGS. 9, 10, 11, 17 and 20), resembles a letter "W" in 
shape. As viewed in FIG. 11, upper surface 100 comprises a pair of 
elongate, concave surface depressions (gullies) 105 separated by one 
elongate convex surface (rib) 107. Upper surface 100 is preferably coated 
with a refractory grade surface coating 109. The undulant contour of upper 
surface 100 provides for greater surface area to be in contact with waste 
material 3, thereby transferring greater heat to these materials. Also, 
upper surface 100 is inclined at about 8.degree.-10.degree. slope so that 
it slopes downwardly, toward the wall of vessel 5 through which material 3 
is introduced into chamber 10. The inclined arrangement prevents low 
caloric content waste materials, e.g., liquid water, from spilling off of 
upper surface 100 and into bake-out trough 110. 
The undulant surface contour of upper surface 100 also helps to position 
newly introduced materials 3 (typically in the form of a sealed paper 
board container or box housing medical waste or the like) above the ash 
residue (not shown) that has been formed from pyrolyzing previously 
introduced waste material and thereby allowing for more even and thorough 
pyrolyzation of the newly introduced waste material. In particular, the 
undulant contour of upper surface 100 prevents the newly introduced 
material 3 from mixing with lower temperature water that may be resident 
in gullies 105. In this arrangement, a box containing waste material 3 is 
placed in first chamber 10 through inlet 60. The box falls into first 
chamber 10 and onto rib 107, where it is prevented from completely 
engaging the ash residue and water that may be collecting in gullies 105. 
This arrangement also helps to maintain at least some direct contact 
between upper surface 100 of refractory mass 75 and the newly introduced 
waste material. 
The heated condition of refractory mass 75 causes heating and pyrolyzing of 
materials 3 which come in close proximity to upper surface 100. By the 
provision of the refractory mass, and maintenance of its heated condition 
at elevated temperatures, the waste material in first chamber 10 which 
comes in close proximity to or contact with the upper surface 100 (via 
contact with at least rib 107) is being continuously heated from 
underneath by the refractory mass. This construction increases 
pyrolyzation of difficult to pyrolyze materials present in the first 
chamber, and contributes to the substantially complete conversion thereof 
to a carbon-free ash residue. 
The heating effect at upper surface 100 is enhanced by the use of stirring 
and mixing means 120 (FIGS. 13-19) which, according to a stirring sequence 
or "recipe" defined by the overall condition of the residue mass (e.g., 
the sensed temperature, hydrocarbon content, etc.) allows for the nearly 
complete conversion of the waste material. One possible form of stirring 
and mixing means 120, that is contemplated for use in the present 
invention, is an extendable, rotatable blade assembly 125 (ERB assembly 
125). Each ERB assembly 125 comprises a shaft 130, a stirring blade 135, a 
shaft scraper 140, and means 145 for moving shaft 130 and stirring blade 
135. More particularly, each shaft 130 includes a conventional cooling 
system 133 (FIG. 18) located along its length and adapted to maintain 
shaft 130 at a lower temperature than that of chamber 10. In one 
embodiment, shaft 130 has air circulated through its interior to maintain 
its temperature within specified limits. Shafts 130 are arranged so that 
they pass through inner and outer walls 53, 51, in substantially parallel 
relation to one another, and below inlet 60. In this way, the portion of 
shafts 130 located at any given time within chamber 10, are positioned in 
spaced, overlying relation to gullies 105 of upper surface 100 of 
refractory mass 75. Shaft scrapers 140 provide a thermally sealed and gas 
tight interface in walls 51, 53, through which shafts 130 may pass into 
chamber 10. Shaft scrapers 140 also help to remove any debris, e.g., ash 
residue, that may collect on the outer surface of shafts 130 while they 
are resident in chamber 10. 
Referring to FIG. 15, stirring blades 135 preferably comprise paddle shaped 
plates of high temperature metal or ceramic, having a first end 147 that 
is adapted to be fixed to an end of a shaft 130 and a second end 149 that 
is somewhat rounded so as to complement the surface contour of gullies 
105. As shown in FIG. 15, second end 149 may include a flattened corner 
portion 151 that complements a flatten bottom surface of each gully 105. 
Means 145 for moving shafts 130 and stirring blades 135 may comprise any 
electromechanical or hydraulic or pneumatic device of a type known for 
moving supported shaft type structures, as long as means 145 is capable of 
imparting two degrees of freedom of movement to shafts 130 and stirring 
blades 135, i.e., means 145 must be capable of moving the shafts linearly, 
into and out of chamber 10, while at the same time imparting selective 
rotational motive force to the shafts so that stirring blades 135 are 
selectively rotated into and out of gullies 105 of upper surface 100. 
For example, a ball screw 155 (FIG. 17) or hydraulic cylinder (not shown) 
may be used to actuate ERB assembly 125. Each ERB assembly 125 is operated 
separately, and independently of the other according to a set program, 
library of routines or recipes in response to sensor data on hydrocarbon 
and gas concentration, gas flow, and temperature. If a preselected change 
in the range of any of these, or other parameters, is sensed, then ERB 
assembly 125 (also called stirrers) is activated to stir the ash residue 
by a preselected series of linear and rotational movements. For thorough 
combustion or pyrolysis, ash material must be stirred periodically and 
spread out over upper surface 100. When pyrolysis has neared an end, or 
finished, shafts 130 are fully extended by means 145, from the end of 
upper surface 100 closest to inner wall 53 of vessel 5, with stirring 
blades 135 rotated so that flattened corner portions 151 are placed into 
full engagement with the bottom surface of each gully 105, and the 
collected ash residue is pushed off, over the end of refractory mass 75 
and into bake-out trough 110. 
If only a single degree of freedom push arm or lever is used to push ash 
residue off upper surface 100, metal objects may be caught between upper 
surface 100 and blade 135. This condition would either break the blade or 
jam it, or bind it, or cause the obstructing object to dig into the 
surface coating. With the present invention, if ERB assembly 125 is in a 
pushing mode and a jam is sensed, then by merely rotating the shaft 
upwardly, a little, to get over the obstruction, the jam can be cleared. 
Also, by rotating each blade 135 according to a preset recipe, different 
amounts of material may be stirred, as needed. Further, blade 135 must be 
rotated completely out of the way when a new box of waste material 3 is 
dropped through inlet 60 onto upper surface 100. Of course, it will be 
understood that a single blade and shaft structure may also be used 
without departing from the present invention, as an equivalent structure 
to a pair of blades and shafts, as long as they can move in two 
directions, i.e., linearly and rotatable. Likewise, more than two blades 
and shafts may also provide means for stirring and mixing the ash residue. 
By stirring the ash residue with ERB assembly 125, it is possible to 
separate newly introduced waste material from prior, already pyrolyzed 
waste material. 
As shown in FIGS. 17-19, one possible means for moving ERB assembly 125 
comprise a ball nut 160 attached on a bracket 163 to support one end of 
shaft 130. Ball nut 160 moves on ball screw 166 and a guide rod 168 guides 
the shaft and blade structure as it moves in and out of chamber 10. A 
hydraulic motor 170 with a belt, or chain and pulley 173 for rotating ball 
screw 166 may be used to move shaft 130 linearly, in and out, of chamber 
10. Another hydraulic motor 175 with a belt or chain pulley 178 may be 
used to rotate shaft 130, and thus blade 135 within chamber 10. A 
conventional shaft encoder, or other known sensor is used to record the 
angular position of blade 135 relative to the center of shaft 130 and 
upper surface 100. As shown in FIG. 18, cooling system 133 comprises a 
system of ducts running the length of shaft 133 and being adapted to 
circulate coolant introduced through coolant port 180, located at a 
proximal end of shaft 130. 
The present invention utilizes three stages of processing. First, the 
primary pyrolysis of waste material 3 is carried out by placing the waste 
material onto upper surface 100 of refractory mass 75. About 85% of the 
volume of waste material 3 is removed at this stage. Then, the ash residue 
is swept off of upper surface 100 of refractory mass 75 by stirring and 
mixing means 120, e.g., by ERB assembly 125, and into bake-out trough 110 
where further primary air is added to the ash, via primary air valves 33, 
so that oxidation rather than pyrolysis, takes place to get rid of the 
rest of the hydrocarbons that are present in the ash residue. About a 
10-15% further reduction in volume of material is accomplished at this 
stage. This ash material then is moved to a cool-down trough 190 where it 
cools. At this stage, only about 5% of the volume of original waste 
material is left. Once cooled, the remaining ash residue is pushed into a 
barrel 200 for disposal. Bake-out trough 110 and cool-down trough 190 are 
best seen in FIGS. 11 and 12, and comprise an elongate, relatively narrow 
concave channel positioned at the bottom of an ash residue collection 
cavity 195 defined between refractory mass 75 and the wall of vessel 5 
(FIGS. 5 and 6). Cool-down trough 190 further includes a bore 197, defined 
in the bottom of the channel, that communicates with a residue barrel 200. 
An extendable, rotatable blade assembly 210 (ERB assembly 210) is arranged 
to move within ash residue collection cavity 195 from a lower portion of 
vessel 5 (FIGS. 1-6, 8, 11-13, and 20-23). ERB assembly 210 comprises 
essentially the same components as ERB assembly 125. More particularly, 
ERB assembly 210 includes a shaft 230, a blade 235, a shaft scraper 240, 
and means 245 for moving shaft 230 and blade 235 within chamber 10. In 
addition, ERB assembly 210 includes a support frame 250 that is adapted to 
structurally support ERB assembly 210 on the outside of vessel 5 (FIG. 3). 
Frame 250 includes an upright support 255 and a horizontal support 258. 
ERB assembly 210 operates in the same way as ERB assembly 125 disposed on 
upper surface 100 of the refractory mass 75, in that ERB assembly 210 
moves linearly and also rotates in accordance with a preselected library 
of routines. An attachment may be fitted over the end of blade 235 to 
increase its surface area, and allows it to conform more to the shape of 
bake-out trough 110 and cool-down trough 190. Further, rather than using 
ball screw 160, ERB assembly 210 includes a hydraulic cylinder 260 that 
moves shaft 230 linearly, with shaft 230 being supported on a support 
carriage 262. Carriage 262 has wheels 263 that ride on a track 268 to 
provide means for moving ERB assembly 210 linearly. ERB assembly 210 mixes 
and stirs ash residue in bake-out trough 110 and also moves ash residue 
into cool-down trough 190. As a consequence, shaft 230 and carriage 
support 262 are longer than ERB assembly 125 and shaft 130. 
As shown in FIGS. 11 and 20, the channels forming bake-out trough 110 and 
cool-down trough 190 are in alignment. Cool-down trough 190 has insulation 
around it, and a water wall 270 adjacent to it. Disposed below opening 
197, in cool-down trough 190, are a pair of slide gates 275 that run in 
racks 277, and are operated by hydraulic cylinders 280. Before opening 
gates/doors 275, barrel 200 must be brought up into contact with a seal 
285 of opening 197 in order to maintain the integrity of the closed 
system. Barrel 200 is supported on a carriage 287 having pivotal arms 289 
adapted for grasping a lower edge of barrel 200 and holding the barrel 
securely. Carriage 287 is mounted on a pivoting arm 288 that allows barrel 
200 to pivot under or away from, opening 197. Barrel 200 is lifted off the 
ground and up against seal 285. This operation is completed by a cable and 
loop 290 that go through pulleys 293 and a crank 297 to lift barrel in 
place. Once barrel 200 is in correct sealed position, slide gates 275 open 
and barrel 200 is filled with ash. Once barrel 200 is filled, gates 275 
are then closed, and barrel 200 lowered and swung out on pivoting arm 288 
for removal. 
Referring to FIGS. 32-35, there is functionally illustrated the components 
of and the operative steps performed by material processing apparatus 1 
under the monitoring and control of computer-based central control system 
44 for effecting optimal pyrolyzing and oxidizing of materials 3 therein 
to provide control of the hydrocarbon release rate in accordance with the 
present invention. FIGS. 32 and 33 provide functional block diagrams of 
material processing apparatus 1, illustrating the directions of 
interactions between the components of the apparatus to maintain the 
target oxygen concentration and thereby control the hydrocarbon release 
rate. FIGS. 34 and 35 are a graphical representation of the target oxygen 
concentration versus time and versus temperature, respectively. 
Basically, material processing apparatus 1 operates through one cycle to 
thermally process, that is, to pyrolyze and oxidize, a predetermined batch 
of material 3, such as biomedical waste material, typically of widely 
varying energy values or contents. Central control system 44 functions to 
operate and regulate material processing apparatus 1 during each batch 
processing cycle by controlling the operation of the first and second 
heater units 25, 27, the position of the air intake proportioning valve 
and the speed of the induction fan 30A and 30B. Central control system 44, 
under control and direction of a software program stored in its internal 
memory repetitively, and at high speed, receives inputs, processes the 
inputs, and generates outputs. The inputs received by central control 
system 44 from the various temperature and gas sensors contain information 
about the current states of the pyrolysis process and of the oxidation 
process. Proportional, Integral, Derivative (PID) control algorithms for 
regulating induction fan speed 30A, proportioning valve position, and 
recipe/sequences for mixing and stirring means 120 and 210 are contained 
in the software program. These algorithms are employed by central control 
system 44 to process the imputed information by integrating the 
information into a logical sequence of decision steps and then generating 
an appropriate set of output instructions to ensure that the pyrolysis and 
oxidation processes and thus the hydrocarbon release rate continue at an 
optimum level. 
Underlying the present invention is recognition by the inventors herein 
that the direct correlation or correspondence between the hydrocarbon 
release rate and the concentration of a preselected gas, preferably 
oxygen, in the discharge gases can be used to control the hydrocarbon 
release rate during operation of the apparatus. For the apparatus to be 
able to accommodate feed materials of widely varying energy contents as is 
needed in most waste disposal applications, and certainly with respect to 
biomedical waste materials, the apparatus must be operated with a 
hydrocarbon release rate that avoids generation and emission of unburned 
hydrocarbons. However, it is not possible to determine in advance the 
energy value or content of the batches of material which are fed into the 
apparatus in order to be able to adjust the operation of the apparatus to 
arrive at the desired hydrocarbon release rate. The inventors herein 
recognized that due to the direct correspondence between the oxygen 
concentration in the discharge gases and the hydrocarbon release rate, if 
only the oxygen concentration is controlled and maintained at a desired 
target then automatically the hydrocarbon release rate is controlled and 
maintained at the desired optimum level. 
More particularly, if the hydrocarbon release rate begins to exceed the 
optimum level, this will result in the occurrence of an oxygen 
concentration in the discharge gases lower than the desired preset target. 
This deficiency will be detected by the oxygen sensor in the heat recovery 
exhaust and transmitted to the control system. The control system will 
then adjust the proportioning valve to reduce the air flow into the 
pyrolysis or first chamber and increase it to the primary section of the 
oxidation or second chamber. As less oxygen is let into the first chamber, 
heat generation by pyrolysis reaction in this chamber is reduced. Since 
the first chamber is surrounded by the coolant jacketed vessel, the 
surface of the waste materials therein will be cooled and thereby lower 
the hydrocarbon release rate to the optimum level. This effect will be 
further enhanced by appropriate mixing of the ash residue atop refractory 
mass 75 and in bake-out trough 110 according to a set of preselected 
recipes. 
It is thought that the present invention and many of its attendant 
advantages will be understood from the foregoing description and it will 
be apparent that various changes may be made in the form, construction and 
arrangement of the parts thereof without departing from the spirit and 
scope of the invention or sacrificing all of its material advantages, the 
forms hereinbefore described being merely preferred or exemplary 
embodiments thereof.