Method of recycling hazardous waste

A method of recycling hazardous and non-hazardous industrial wastes to reclaim valuable metals, metal alloys, and metal oxides, and to produce mineral wool. Wastes including hazardous wastes of USEPA Series D, F, P, K, and U are pulverized and blended with liquids such as water or wastewater to produce a homogeneous mass. Calcium from calcium-stabilized wastes is used to enhance the quality of the mineral wool, lower the sulfur content, remove phosphorous, and raise pH to facilitate metal reduction. The mass is formed into briquettes and melted in a cupola or shaft furnace in the presence of carbon or aluminum to reduce metals. Other types of furnaces such as an electric arc furnace may be used to avoid the steps of forming and curing briquettes. Reduction is carried out at temperatures between 1660 and 3100 degrees Fahrenheit. Reducible metals are reduced and drawn off into molds. Substantial purity is obtained in the recovered reducible metals. Volatile metals are volatilized and reclaimed in the air pollution control system. Remaining slags comprising principally oxides of non-reducible metals are used to produce mineral wool. Exhausts, heavy solids, and unspun shot particles are recycled into the system to eliminate waste.

BACKGROUND OF THE INVENTION 
The present invention relates broadly to a waste recycling and metal 
recovery method. More particularly, the present invention relates to a 
method for recycling metal-bearing hazardous wastes to recover valuable 
metals and metal oxides. In the best mode, slags remaining after metal 
recovery are used to produce mineral wool, and no waste results. 
Public awareness of problems associated with the rapid depletion of the 
earth's natural resources and disposal of industrial wastes has greatly 
increased in recent times. Such awareness, together with increased 
economic pressures, the tightening of competition, and government 
regulation of wastes have forced industrial concerns to take measures to 
minimize waste. In response, the focus of scientific undertaking in some 
industries has turned toward recovery and reuse of all commercially useful 
byproducts of industrial processes. 
In the past, little attention was directed to the preservation of limited 
mineral resources. It was generally deemed more feasible to mine metal 
ores and to simply dump rich metal-bearing wastes than to salvage usable 
metals from waste products. This was particularly true in the case of 
industrial wastes which contained hazardous or toxic materials. 
Hazardous industrial wastes were typically "stabilized"and/or captured in 
some generally non-leachable form with a basic material such as lime or 
cement. It is required to bury the stabilized materials in designated 
hazardous waste landfills. One widely accepted disposal method was to 
incorporate hazardous waste products into a glass-like matrix called slag 
which was used as a substitute for a natural rock aggregate in cement or 
asphalt used for paving roads and the like. However, the EPA has declared 
that no material which is considered hazardous can be applied to the land 
in any form, whether or not it has been diluted, treated, or otherwise 
"stabilized". Hence, the older disposal methods have fallen into disfavor. 
Alternative processes for treating wastes to produce environmentally 
"safe"products have been proposed. 
For example, Frey U.S. Pat. No. 4,432,666 issued on Feb. 21, 1984 describes 
a process for storing and dumping hazardous wastes. Rostoker, U.S. Pat. 
No. 4,793,933 issued Dec. 27, 1988 teaches a method for treating metal 
hydroxide electroplating sludges by fusion of the oxides of the metals 
into a silica and sodium slag. The Rostoker method relates to earlier EP 
Leaching standards, and has been proven incapable of achieving 
minimal-waste recycling. Lynn, U.S. Pat. No. 4,840,671 issued Jun. 20, 
1989, relates to the stabilization of EAF dusts for disposal. The latter 
'671 reference teaches the use of calcium hydroxides as an entrapping 
agent for toxic cadmium, chromium, and lead constituents. This patent 
suggests combining various different waste products to be processed to 
produce "safe" compounds. 
However, in view of the general awareness of environmental and health 
risks, such treatment and disposal techniques are no longer deemed 
environmentally or economically sound. Moreover, because industry pays a 
relatively high premium for waste treatment and disposal, it is desirable 
to provide a commercially viable method for recovering as much usable 
material as possible. Such methods would be directed to reducing loss of 
profits and expanding commercial markets. Specifically, it is desired to 
provide a process which can be carried out with equipment and apparatus 
already available in the industry. 
The United States Environmental Protection Agency (USEPA) has undertaken to 
classify certain materials for controlled disposal and/or recovery. The 
list of USEPA-listed hazardous wastes is presently limited, but will 
undoubtedly be enlarged with time. There are presently a large number of 
waste products generally recognized as unsafe for conventional disposal 
which have not yet come under USEPA scrutiny. For example, certain 
anodizing wastes such as F019 are presently listed but not classified as 
hazardous; sand used in blasting operations may be contaminated with 
nickel, chrome, or other metals which are considered toxic; and, baghouse 
dusts may contain carbon and hazardous materials have no separate 
classification under the current law. Such wastes are therefore thrown 
away without meaningful disposal precautions, although they are widely 
believed to create hazards to the environment. Moreover, their disposal 
results in unnecessary depletion of existing natural mineral resources. 
It is therefore desired to provide a viable method for reclaiming various 
listed and also non-listed hazardous wastes. Such a method must 
effectively eliminate waste in order to conserve natural resources and 
avoid costly liability, for example, under the Resource Conservation and 
Recovery Acts ("RCRA") or Comprehensive Environmental Response, 
Compensation, and Liability Act ("CERCLA"). Moreover, such a method must 
be effective to overcome disadvantages associated with prior sodium-based 
recovery processes. Such disadvantages include high reagent cost, pH 
imbalances in slags, low value by-products, production of waste, and 
undesired volatilization of sodium due to the higher temperatures required 
to reclaim certain metals (i.e., chromium). 
In the prior art known to us, numerous methods are taught for recovering 
various industry wastes for production of useful products. Such products 
include furnace fuels, paving aggregates, sealing compounds, and mineral 
wool. 
Mineral wool is a term broadly applied to various related products commonly 
used for insulation, padding, and the like. In general, mineral wool is a 
fiberglass-like material composed of very fine, interlaced mineral fibers, 
somewhat similar in appearance to loose wool. Low-temperature wools are 
composed primarily of silicates of calcium and aluminum. Mineral wool 
producers commonly use natural rock or slag. Slag is a term broadly 
applied to refer to waste products of the primary metal and foundry 
industries, including the erosion of refractory from the furnace lining, 
charge impurities, ash from fuel, and fluxes used to clean the furnace and 
remove impurities. Although metal producers and foundries strive to 
control the amount of slag, excess slag may result from overfluxing. 
Slags are classified as either "acid" (or high silicate) slags or "basic" 
slags, depending upon the relative quantities of acidic and basic 
subcomponents. For example, typical acid slags contain between forty and 
fifty percent (40-50%) silica (SiO.sub.2), an acidic subcomponent, and 
relatively small quantities of basic components such as oxides of calcium 
(CaO) and magnesium (MgO). Aluminum oxide (Al.sub.2 O.sub.3), which comes 
from the furnace lining, ranges from ten to twenty percent (10%-20%) and 
is considered neutral. A typical basic slag, on the other hand, comprises 
between twenty-six to forty-seven percent (26%-47%) silica (SiO.sub.2) and 
between five and twenty percent (5%-20%) aluminum oxide (Al.sub.2 O.sub.3) 
as the acidic subcomponents, and calcium oxide (CaO) ranging between 
thirty-two and forty-eight percent (32%-48%) and magnesium oxide (MgO) 
ranging between seven-tenths and twenty percent (0.7%-20%) as the basic 
subcomponents. Either magnesium oxide or aluminum may come from the 
erosion of the furnace lining or magnesium may be added to increase the 
slag basicity. 
Basicity is the tool used to determine metal quality produced from a basic 
slag. Basicity is calculated as follows: (CaO + MgO) .div. (Al.sub.2 
O.sub.3 + SiO.sub.2) Basicity of typical basic slags ranges between 0.93 
and 1.9. Generally speaking, metal producers using very high quality 
metals as charging materials use an acid slag, while metal producers using 
charge materials which need refining use a basic slag. For best results, 
mineral wool producers seek slags that can be blended together and melted 
at relatively low temperatures. Preferably the mineral wool slag will 
contain no reducible metals, or will be an acid slag, which will eliminate 
metal buildup in the furnace. 
Mineral wool is classified according to the raw materials used in its 
production. For example, Rock Wool is produced from combinations of 
natural rocks and/or minerals. Slag Wool comprises a composition of iron, 
copper, and lead slags typically removed from blast furnaces, and may 
contain some fluxing materials. Glass Wool is composed principally of 
silica sand, soda ash, and limestone. Refractory (high-temperature) or 
"Certa" wool may be made from oxides of aluminum, chromium, zirconium, or 
titanium and silica sand. Further subclassifications of these products 
relate to the quality or purity of the wool. For example, slag wool is 
subclassified for purity according to color; black, gray, and white wools 
are available. The tool for determining the quality of mineral wool 
produced from a slag charge is the Acid-to-Base ratio (A:B). The formula 
for determining A:B is (Al.sub.2 O.sub.3 + SiO.sub.2) .div. (CaO + MgO). 
In a typical mineral wool cupola slag, A:B ranges between 0.74 and 2.316. 
Prior art patents related to the production of mineral wool using various 
waste products include Gee U.S. Pat. No. 4,822,388 issued Apr. 18, 1989; 
and Monaghan U.S. Pat. No. 4,486,211 issued on Dec. 4, 1984. The 
latter-referenced '211 patent discloses a method and apparatus for melting 
discarded fly ash and spinning it into mineral wool. However, none of the 
prior art known to us teaches viable methods for recycling listed 
hazardous materials such as Chromium, Nickel, Cadmium, Zinc, Copper, Iron, 
and Lead Oxides or hydroxides into pure metals or alloys while producing 
mineral wools from Aluminum, Zirconium, and Titanium oxides 
Other relevant prior art patents known to us relate to methods for 
treatment, recovery, and recycling. For example, Allen, U.S. Pat. No. 
3,870,507, issued Mar. 11, 1975 is directed to a method for forming 
briquettes from steel mill wastes such as steel and iron dust, mill scale, 
and iron oxides with an organic binder to reduce slags formed during 
recycling. The resulting iron oxide briquettes are recycled by being fed 
into the production furnaces with new materials in the steel-making 
process. Fukuoka U.S. Pat. No. 4,004,918 issued on Jan. 25, 1977, teaches 
a method for treating certain wastes resulting from stainless steel 
operations. Briquettes are formed from the dust and scale from stainless 
steel ovens combined with organic and inorganic binders. The briquettes 
are returned to the existing electric arc furnace, and usable metals are 
extracted for further use in making stainless steel. 
Stephens U.S. Pat. No. 4,396,423 issued Aug. 2, 1983 and related U.S. Pat. 
No. 4,053,301 issued Oct., 1977 relate to a process for recovery of iron 
carbide and zinc metals from BOF dusts of the steel-making process. The 
Stephens system reduces the dust wastes within a fluidized bed reactor in 
the presence of carbon, recovers zinc by vaporization, and produces iron 
carbide and gangue, a worthless rock or matter in which metals are 
contained. 
U.S. Pat. Nos. 4,758,268 issued Jul. 19, 1988 and 4,836,847 issued Jun. 6, 
1989 to Bishop disclose apparatus and processes for reclaiming metals from 
electric arc furnace and BOF dusts. The systems described therein are 
directed to providing recovery of metals from EAF wastes in a reducing 
environment. In the method, carbon is added to the molded briquettes to 
reduce the iron and zinc content of the waste. However, the process is 
incapable of producing a slag suitable for use in the production of 
mineral wool, since these processes attempt to minimize slags to less than 
8%. Moreover, the Bishop system is specifically indicated to be unsuited 
for rotary kilns, shaft furnaces, retorts, and fluidized bed furnaces 
For purposes of clarity, various terms familiar to those skilled in the art 
and commonly used in the industry are applied herein and shall be 
clarified as necessary in context. Various hazardous wastes specifically 
identified shall be referred to by their standard USEPA designations, as 
for example, K061 (electric arc furnace dust). 
SUMMARY OF THE INVENTION 
The present invention is directed to a process for recycling industrial 
wastes. In the best mode, total recycling is accomplished by reclaiming 
metals and metal oxides from hazardous industrial wastes and by producing 
mineral wool from slags. Preferably a plurality of hazardous and 
non-hazardous wastes are combined to produce valuable products. Of 
particular advantage is the fact that the present process may be 
accomplished using various types of industrial equipment already in place. 
Among the wastes which may be applied in the instant process are 
USEPA-listed hazardous wastes of Series D, F, K, P, and U. These wastes 
are mixed in proper proportions in combination with calcium, pulverized to 
a predetermined mesh size, and blended with liquids such as waste water to 
produce a homogeneous mass. 
Calcium is essential to the instant recycling process, since the process 
involves the production of mineral wool as well as recovery of metals. 
Calcium imparts beneficial qualities to the mineral wool product. While 
virgin calcium may be used, preferably the source of calcium will be 
calcium-stabilized wastes, such as metal sludges stabilized with calcium 
oxide or lime. Calcium lowers the sulfur content, removes phosphorous, and 
raises pH to facilitate metal reduction. Calcium lowers the eutectic point 
of the waste mixture, and fluxes metals or alloys as it removes sulfur. 
Where the process is carried out using a cupola or shaft furnace, it is 
necessary to first shape the blended mass into briquettes of predetermined 
proportions. The briquettes are then cured to reduce the moisture content 
and improve structural stability. However, if an electric arc furnace, 
glass furnace, or the like is used, the steps of forming and curing the 
briquettes are eliminated. 
The briquettes are then reduced in the presence of carbon and/or aluminum 
to separate out reducible metals, volatile metals, and molten slag. In the 
best mode, reduction will be carried out at temperatures between 1660 and 
3100 degrees Fahrenheit in the presence of carbon or aluminum. Reducible 
metals are drawn off from the slag into molds. Volatile metals are 
volatilized and reclaimed in the air pollution control system. 
Non-reducible metals, which are used for the production of mineral wools, 
remain as oxides in the slag. 
Preferably exhaust gases and solid particles produced in the instant 
process are recycled into the process for further purification for 
powering the process. Unspun slag particles known as "shot" which remain 
from the production of mineral wool are also recycled into the system. 
Various specific examples of numerous possible applications of the present 
process are provided. 
Thus it is a fundamental object of the present invention to provide a 
viable method for recycling industrial wastes. 
Another fundamental object of the present invention is to provide a 
recycling process which protects and preserves valuable mineral resources. 
A similar broad object of the present invention is to provide a method for 
recovery of metals and metal oxides from hazardous wastes. 
Another fundamental object of the present invention is to provide a 
commercially viable method for recycling hazardous and non-hazardous 
waste. 
A further basic object of the present invention is to provide a method for 
recycling waste which may be practiced using existing industrial systems 
and apparatus. 
Another basic object of the present invention is to provide a waste 
recycling method which combines various hazardous and non-hazardous wastes 
to produce commercially valuable products. 
Yet another object of the present invention is to provide a method for 
recycling hazardous wastes to produce mineral wool. 
Still another object of the present invention is to provide a waste 
recycling method which minimizes industrial waste and itself produces no 
hazardous by-products. 
An additional object of the present invention is to provide a calcium-based 
hazardous waste recycling method which overcomes problems associated with 
previous sodium-based stabilization and recovery processes. 
A further object of the present invention is to provide a method for 
recovering valuable metal alloys from metal-bearing hazardous wastes. 
Another object of the present invention is to provide a commercially viable 
waste recycling method which is an effective alternative to treatment and 
disposal as established by RCRA, CERCLA, and similar environmental 
protection Acts. 
A specific object of the present invention is to provide a method for 
recovering Chromium, Nickel, Cadmium, Zinc, Iron, Copper and other metals 
from industrial waste products. 
A similar object of the present invention is to provide a method of 
recovering various alloys from industrial sludge. 
A further object of the present invention is to provide a waste recycling 
method in which titanium, zirconium, aluminum, and chromium oxides are 
used in the production of mineral wool. 
Another object of the present invention is to provide a waste recycling 
method which permits continued use of preexisting waste treatment systems. 
An additional object of the present invention is to provide a recycling 
method in which various listed and unlisted wastes are combined with 
calcium and silica to produce valuable products 
Still another specific object of the present invention is to provide a 
hazardous waste recycling method in which electric arc furnace dust is 
combined with calcium and silica products to produce low temperature 
mineral wool or slags suitable for mineral wool production. 
Yet another object of the present invention is to provide a hazardous waste 
recycling method which may be accomplished in various types of 
high-temperature furnaces. 
These and other objects and advantages of the present invention, along with 
features of novelty appurtenant thereto, will appear or become apparent in 
the course of the following descriptive sections.

DETAILED DESCRIPTION 
With reference to the accompanying drawing, our new method of recycling 
hazardous waste is broadly designated by the reference numeral 10. The 
method 10 produces valuable products such as pure metals, metal alloys, 
metal oxides, and mineral wool from various combinations of waste 
materials, including common hazardous and non-hazardous industrial wastes. 
Because numerous types of existing waste treatment apparatus may be used, 
only general reference is made herein to broad classes of functional 
components which may be effectively used in carrying out the present 
method 10. 
Waste products generally comprising free-standing sludge composed of 
twenty-five to fifty percent (25-50%) solids and dry dusts such as K061 
(electric arc furnace dust) are collected from various sources and stored 
in storage silos 15. Industrial wastes may be collected from numerous 
sources for use in the instant method 10. Wastes which may be utilized by 
the present technology are listed and categorized in Table 1: 
TABLE 1 
______________________________________ 
EPA-Classified Wastes 
EPA 
Designation 
Definition/Source 
______________________________________ 
K004 Waste water treatment sludge from production of 
zinc yellow pigments. 
K005 Waste water treatment sludge from production of 
chrome green pigments. 
K006 Waste water treatment sludge from production of 
chrome oxide green pigments. 
K007 Waste water treatment sludge from production of 
iron blue pigments. 
K008 Oven residue from the production of chrome oxide 
green pigments. 
K045 Spent carbon from the treatment of wastewater 
containing explosives. 
K061 Emission control dust/sludge from production of 
steel in electric furnaces. 
K062 Spent pickle liquor from steel finishing 
operations which use Chlorine. 
K069 Emission control dust/sludge from secondary 
lead smelting. 
K088 Spent aluminum potliner. 
P021 Calcium cyanide 
P029 Copper cyanide 
P030 Cyanides (soluble cyanide salts), not 
otherwise classified. 
P074 Nickel cyanide 
P104 Silver cyanide 
P106 Sodium cyanide 
P121 Zinc cyanide 
P122 Zinc phosphide, if greater than ten percent. 
U032 Calcium Chromate 
U249 Zinc phosphide (concentrations less than 10%) 
D006 Cadmium, if greater than 1 mg/L total leachate 
D007 Chromium, if greater than 5 mg/L total leachate 
D008 Lead, if greater than 5 mg/L total leachate 
D011 Silver, if greater than 5 mg/L total leachate 
F006 Wastewater treatment sludges from electroplating 
F007 Spent cyanide plating bath solutions from 
electroplating operations 
F008 Plating bath residues from the bottom of plating 
baths from electroplating cyanides 
F009 Spent stripping and cleaning bath solutions from 
electroplating cyanides 
F010 Quenching bath sludge from oil baths from metal 
heat-treating operations using cyanides 
F011 Spent cyanide solutions from salt bath pot 
cleaning from metal heat-treating operations 
F012 Quenching wastewater treatment sludges from 
metal heat-treating operations using cyanides 
F019 Wastewater treatment sludges from the chemical 
conversion coating of aluminum 
F024 Wastes, not limited to, distillation residues, 
heavy ends, tars, and reactor clean-out wastes 
from chlorinated aliphatic hydrocarbons, having 
carbon content from one to five, utilizing free-radical 
catalyzed processes 
______________________________________ 
Other wastes which may be used in the process include sand from casting or 
blasting operations, carbon from baghouse dusts, coal and coke fines, 
K088, and slags. Calcium-stabilized wastes which may contain a variety of 
ingredients, including both reducible and nonreducible metals, metal 
oxides, hydroxides and/or organics are also useful in the process. Typical 
compositions of such calcium-stabilized wastes are listed in Table 2: 
TABLE 2 
______________________________________ 
Calcium-Stabilized Wastes 
Ingredient Percent of Material 
______________________________________ 
CaO 41.2 
Ignition Loss 32.7 
Al.sub.2 O.sub.3 1.7 
Si.sub.2 O 13.1 
Fe.sub.2 O.sub.3 4.47 
Total Solids 69.24 
Organics 4.61 
As 0.000792 
Cd 0.00171 
Cu 0.0549 
Hg 0.000207 
Ag 0.000298 
Ba 0.567 
Cr 0.275 
Pb 0.0514 
Ni 0.0225 
Zn 0.197 
______________________________________ 
With reference directed to the drawing, predetermined amounts of selected 
wastes are delivered from selective silos such as silos 18, 20, 22, 24, 
28, and 30 via a conveyor 33 to a pulverizer 36. The wastes are combined 
and ground in pulverizer 36 to a mesh size typically three hundred (300) 
or smaller. The pulverized wastes pass via conduit 38 from pulverizer 36 
into a brick-making machine 40. Predetermined amounts of liquids stored in 
suitable tanks 45, 47, 49 preferably including water and certain 
metal-bearing liquids such as K062, F007, F009, or water-soluble oils are 
delivered via pipe 53 into the brick-making machine 40 and there mixed 
with the pulverized wastes until a homogeneous, semi-solid mass is 
achieved. 
Brick-making machine 40 extrudes or otherwise forms the blended, semi-solid 
mass into briquettes of a predetermined size suitable for the selected 
melting apparatus. The briquettes thus formed are conveyed from the 
brick-making machine 40 via line 60 into a curing station 66. Curing 
station 66 is preferably operated at a temperature of roughly two hundred 
degrees Fahrenheit, and the briquettes are preferably cured for a period 
of twenty-four hours. The cured briquettes comprise a substantially 
hardened block of thoroughly blended waste materials. 
Cured briquettes are transferred from curing station 66 by skip cart or 
conveyor 71. Coke or similar fuel retained in storage bin 76 is conveyed 
together with the cured bricks to a cupola 80 or similar furnace. It will 
be appreciated that the best mode described is directed to the use of a 
cupola 80 or shaft furnace, which requires that briquettes be used. 
However, the process may also employ other types of furnaces, such as 
electric arc or glass furnaces. Where the latter-mentioned furnaces are 
employed, it is not necessary to form briquettes prior to melting. Thus, 
the brick-making and curing steps may be omitted. 
The cupola 80 thus charged with the fuel and briquettes is heated to a 
temperature of between 1,660.degree. F.-3,100.degree. F. In the best mode, 
temperatures between 2750.degree. F. and 2800.degree. F. are preferred. 
When heating takes place in the presence of carbon or aluminum, a reducing 
atmosphere is provided in cupola 80. In the selected temperature range, a 
reaction occurs between the various metal oxides of the wastes and the 
carbon which results in the production of carbon monoxide and metals which 
are reduced to their metallic states. With the addition of proper 
additives as described in the following examples, reducible metals may be 
reclaimed as pure metals or alloys, and volatile metals may be reclaimed 
as concentrated oxides. 
During heating, the briquettes are melted and may be subsequently separated 
into various component products. Such products include reducible metals; 
volatile metals; non-reducibles such as certain metal oxides, silica, and 
calcium; and, exhaust products. 
Reducible metals such as copper, chromium, iron, and nickel or alloys may 
be drawn off the molten mixture in a cupola 80 via the lower tap 84, which 
is preferably coupled to a mold 92. In the mold 92, the reducible metals 
are shaped into selective usable dimensions and cooled. The molded metals 
may be transferred via route 94 after cooling to suitable storage 95 for 
sale. 
Based on our experimentation, substantial purity is obtained in the 
recovered reducible metals. For example, treated sludges containing oxides 
or hydroxides of nickel and iron only will reduce virtually quantitatively 
to a ferro-nickel alloy. Copper-rich sludges may be reduced to copper 
metal of ninety-nine percent (99%) purity. From oxide mixtures containing 
iron, nickel, and chromium, 99% of iron, 98% of nickel, and approximately 
85% of chromium may be recovered as an alloy. 
After the reducible metals are separated out and removed from the molten 
mixture, a molten slag remains. The slag is devoid of volatile metals such 
as cadmium and zinc, and various metal oxides such as oxides of aluminum, 
chromium, titanium, silicon, zirconium, and calcium remain. The latter 
metal oxides, which are essential for the production of mineral wool, are 
drawn off via the upper tap 99 of cupola 80. From tap 99 the metal oxides 
may be blown or spun into mineral wool at production station 103. The 
mineral wool produced at station 103 is fed into collection bins 107, and 
subsequently separated and packaged for sale in a bagging machine 114. 
After bagging, the mineral wool is moved 115 to storage 118 for sale. The 
shot, comprising unspun particles of slag, is recycled 105 from station 
103 into the recycling station 140. As indicated in the following 
examples, shot generally comprises one-third of each mineral wool cycle. 
The volatile metals are volatilized in the presence of Carbon. Carbon or 
carbon monoxide removes the oxygen from the oxides of cadmium and zinc in 
the same manner as it does with the reducible metals. Cadmium and zinc 
thus reduced to their metallic states are volatilized at a selected lower 
temperature. Volatile metals and other exhaust products are directed out 
of cupola 80 via exhaust ports 125. 
Port 125 feeds into a heavy solids separator 133. A fine water mist 
injected into the separator 133 separates out particles of a size larger 
than one micron (1 .mu.) from the exhaust products. These particles are 
delivered into recycling station 140 via conveyor 134 back into the 
pulverizer 36 and are recombined with other waste mixtures from silos 15 
for further processing in accordance with the present method. 
Solid particles smaller than 1 micron and exhaust gases remaining after 
processing in separator 133 are passed into an afterburner 146. In 
afterburner 146, these particles and gases which include carbon and carbon 
monoxide and/or other combustibles are mixed with air and natural gas and 
ignited. Ignition converts the excess carbon monoxide into an energy 
source for use by the system. 
Hot burning gases pass into a waste heat boiler 151, which produces steam. 
As indicated by broken lines 155, the steam is piped out of boiler 151 and 
used to power the briquette dryer 66 and the mineral wool production 
station 103. The cooled exhaust gases are directed via pipe 163 into a 
heat exchanger 167. The gases release heat which is used to heat outside 
air fed into exchanger 167 via blower 174. As indicated by dashed line 
177, the preheated air warmed by the exhaust gases are piped into the 
tuyeres of cupola 80. Cooler gases are subsequently directed via duct 183 
into a baghouse 189. 
In baghouse 189, the reduced-temperature gases are treated to separate 
solids from exhaust gases. The solids generally comprising marketable 
oxides from the volatilized zinc, cadmium, and lead are moved as indicated 
at 190 to storage 118. The exhaust gases, now purified of offensive or 
hazardous components, are drawn upwardly by a fan 194 through stack 198 
and exhausted into the environment. The present method thus provides 
complete recycling of waste products to produce marketable substances with 
minimal resulting waste. Complete reclamation of hazardous and/or valuable 
substances by the present process permits industry to minimize waste, 
fully exploit its available resources, and expand its markets. 
The present process is well-adapted to use with numerous types and blends 
of waste products. Various examples of successful applications of the 
process are provided hereinafter. However, it will be appreciated that 
such examples are provided only as representative of the best mode and are 
not intended to limit the scope of the present application. 
Organic binders containing cyanide were used to stabilize and harden the 
bricks used in various tests. Cyanide aids in the metal-reduction process. 
Importantly, no cyanide was detected in the slag or the metals after 
processing. Any cyanides present in the air stream in the form of hydrogen 
cyanide are destroyed in the afterburner of the boiler and are not 
emitted. 
As illustrated by the following examples, the present process represents an 
important advance in the art of waste recycling. However, it will be 
appreciated that the system 10 may find many applications, and the 
following examples are provided merely as illustrative, and are not to be 
construed to limit the scope of the invention. 
EXAMPLE I 
RECOVERY OF ZINC AND IRON AND PRODUCTION OF MINERAL WOOL 
The waste materials listed in Table 3 below are mixed into a homogeneous 
mass and molded into small briquettes. The briquettes are dried to a final 
moisture content of five percent, and subsequently reduced in a shaft 
furnace at 1800 degrees Fahrenheit using coke as fuel at a 1:1 charge to 
fuel ratio. 
TABLE 3 
______________________________________ 
Waste Materials Used in Sample 
EPA Designation 
*Components Percent of Total 
______________________________________ 
K061 63.1% 
CaO 25% 
Fe.sub.2 O.sub.3 as Fe 
24% 
ZnO as Zn 22% 
SiO.sub.2 3% 
MgO 3% 
PbO as Pb 1% 
Cr.sub.2 O.sub.3 as Cr 
0.07% 
CdO as Cd 0.065% 
K062 (stabilized secure 19.42% 
land fill material) 
CaO 41.2% 
SiO.sub.2 13.1% 
Organics 4.61% 
Fe.sub.2 O.sub.3 as Fe 
4.47% 
Al.sub.2 O.sub.3 as Al 
1.7% 
Zn 0.0197% 
Ba 0.00567% 
Cu 0.00549% 
Pb 0.00514% 
Cr 0.00375% 
Ni 0.00225% 
As 0.000792% 
Hg 0.000201% 
Cd 0.000171% 
F019 9.71% 
Al(OH).sub.2 
74% 
Ca(OH).sub.2 
15% 
Mg(OH).sub.2 
10.4% 
New Silica Sand 7.77% 
SiO.sub.2 98% 
______________________________________ 
*Components are given by dry weight as measured at 101Degrees Centigrade. 
A typical sample of products resulting from one ton of dried briquettes 
passing through one cycle of the present process is shown in the following 
Table 4. 
TABLE 4 
______________________________________ 
Yield from One Ton Sample 
PRODUCT SUBCOMPONENTS POUNDS 
______________________________________ 
Primary Alloy 315.67 
Fe 314.45 
Cr 0.63 
S 0.56 
Cu 0.02 
Ni 0.01 
Volatile Metals 250.84 
Zn 249.94 
Pb 0.78 
Cd 0.12 
Secondary Alloy 
Pb 12.32 
Slag (OXides) 1,116.92 
Ca 504.65 
Si 356.28 
Al 152.16 
Mg 57.55 
Fe 16.77 
S 12.11 
F 9.84 
Na 6.15 
Chlorides 0.80 
Pb 0.32 
Cr 0.27 
Mineral Wool from Slag 838 
Shot 279 
______________________________________ 
The resulting Acid:Base ratio in Example I is 0.92. Basicity is 1.11. All 
exhausts, heavy solids, and shot are recycled into the system, and no 
wastes result. Lead present as a secondary alloy readily separates from 
the iron in the molds and after cooling. 
EXAMPLE II 
RECOVERY OF IRON AND ZINC AND PRODUCTION OF MINERAL WOOL 
The wastes listed in Table 5 below are mixed into a homogeneous mass and 
molded into small briquettes. The briquettes are cured and subsequently 
reduced in a shaft furnace at 2900 degrees Fahrenheit. In this sample, 
fuel consumption is reduced by roughly one-half, due to the presence of 
aluminum in the waste. The aluminum contained in the casting sands and the 
sludge from the grinding and buffing operations helps to reduce the iron 
while increasing the slag temperature and volatilizing the zinc. 
TABLE 5 
______________________________________ 
Waste Materials Used in Sample 
EPA Designation 
*Components Percent of Total 
______________________________________ 
K061 70% 
CaO 25% 
Fe.sub.2 O.sub.3 as Fe 
24% 
ZnO as Zn 22% 
SiO.sub.2 3% 
MgO 3% 
PbO as Pb 1% 
Cr.sub.2 O.sub.3 as Cr 
0.07% 
CdO as Cd 0.065% 
MOLDING SAND 10% 
SiO.sub.2 93% 
Organic Binders 
3% 
Al.sub.2 O.sub.3 
2% 
Al 1.66% 
GRINDING 20% 
BUFFING SLUDGE 
Al 41% 
Fibers 33% 
SiO.sub.2 20% 
______________________________________ 
*Components are given by dry weight as measured at 100Degrees Centigrade. 
Products obtained from a representative one-ton sample of dried briquettes 
processed in Example II are set forth in the following Table 6. 
TABLE 6 
______________________________________ 
Yield from One-Ton Sample 
PRODUCT SUBCOMPONENTS POUNDS 
______________________________________ 
Primary Alloy 336.86 
Fe 336.0 
Cr 0.86 
Volatile Metals 278.14 
Zn 277.2 
Cd 0.86 
Pb 0.08 
Secondary Alloy 
Pb 13.65 
Slag (Oxides) 948.61 
Si 361.73 
Ca 350.00 
Al 143.91 
Mg 42.0 
Fe 17.92 
F 10.92 
S 8.09 
Na 6.83 
Inerts 5.85 
Chloride 0.89 
Pb 0.35 
Cr 0.12 
Mineral Wool from Slag 711 
Shot 237 
______________________________________ 
The Acid:Base Ratio of Example II is 1:33; basicity is 0.78. As in the 
first example, lead is present as a secondary alloy which readily 
separates from the iron in the molds and after cooling. Exhausts, heavy 
solids, and shot are recycled and no wastes result. 
EXAMPLE III 
RECOVERY OF CHROME, ZINC, NICKEL, AND IRON ALLOY AND PRODUCTION OF MINERAL 
WOOL 
The wastes listed in Table 7 below are mixed into a homogeneous mass and 
formed into briquettes. The briquettes are then cured to a final moisture 
content of five percent. The briquettes are reduced in a shaft furnace at 
3100 degrees Fahrenheit using coke at a 2:1 charge-to-fuel ratio. 
TABLE 7 
______________________________________ 
Waste Materials Used in Sample 
EPA Designation *Components Percent of Total 
______________________________________ 
K061 40% 
CaO 25% 
Fe.sub.2 O.sub.3 as Fe 
24% 
ZnO as Zn 22% 
SiO.sub.2 3% 
MgO 3% 
PbO as Pb 1% 
Cr.sub.2 O.sub.3 as Cr 
0.07% 
CdO as Cd 0.065% 
F006 31% 
Cr 24.662% 
Ni 15.559% 
Organics 9% 
Fe 8.44% 
CaO 1.88% 
Zn 1.193% 
Cu 0.71% 
Mg 0.6% 
Pb 0.0272% 
F019 6% 
Al(OH).sub.2 
74% 
Ca(OH).sub.2 
15% 
Mg(OH).sub.2 
10.4% 
K062 (stabilized secure 14% 
land fill material) 
CaO 41.2% 
SiO.sub.2 13.1% 
Organics 4.61% 
Fe.sub.2 O.sub.3 as Fe 
4.47% 
Al.sub.2 O.sub.3 as Al 
1.7% 
Zn 0.0197% 
Ni 0.00225% 
Ba 0.00567% 
As 0.000792% 
Cu 0.00549% 
Hg 0.000201% 
Pb 0.00514% 
Cd 0.000171% 
Cr 0.00375% 
______________________________________ 
*Components are given on a dry weight basis as detected at 101degrees 
Centigrade. 
Products obtained in a representative sample of the process of Example III 
are listed in Table 8 below: 
TABLE 8 
______________________________________ 
Yield from One-Ton Sample 
PRODUCT SUBCOMPONENTS POUNDS 
______________________________________ 
Primary Alloy 458.19 
Fe 252.67 
Cr 107.26 
Ni 94.06 
Cu 4.2 
Volatile Metals 165.616 
Zn 165.11 
Cd 0.50 
Pb 0.006 
Secondary Alloy 
Pb 7.98 
Slag (Oxides 847.68 
Ca 345.02 
Si 290.82 
Al 94.73 
Cr 45.97 
Mg 39.89 
Fe 13.48 
S 6.92 
F 6.24 
Na 3.9 
Cl 0.51 
Pb 0.20 
Mineral Wool from Slag 636 
Shot 211 
______________________________________ 
The resulting Acid:Base ratio is 0.92. Basicity is 1.11. Exhausts, heavy 
solids, and shot are recycled into the system, and no wastes result. 
EXAMPLE IV 
RECOVERY OF CU AND PRODUCTION OF MINERAL WOOL 
The waste materials listed in Table 9 below are mixed and molded into 
briquettes. The briquettes are cured to a final moisture content of six 
percent, and reduced at 2200 degrees Fahrenheit in a shaft furnace using 
coke at a 6:1 charge-to-fuel ratio. 
TABLE 9 
______________________________________ 
Waste Materials Used in Sample 
EPA Designation 
*Components Percent of Total 
______________________________________ 
F006 60% 
Cu 30.01% 
CaO 23.0% 
Zn 4.2% 
Cr 0.0036% 
Ni 0.0036% 
Ba 0.0008% 
As 0.006% 
MOLDING SAND 10% 
SiO.sub.2 93% 
Organic Binders 
3% 
Al.sub.2 O.sub.3 
2% 
Al 1.66% 
AIR EMISSION DUST 20% 
C 50% 
CaO 21% 
Al.sub.2 O.sub.3 
10% 
SiO.sub.2 6% 
MgO 3.1% 
Fluorides 0.3% 
GRINDING 10% 
BUFFING SLUDGE 
Al 41% 
Fibers (carbonized) 
33% 
SiO.sub.2 20% 
______________________________________ 
*Components are given on a dry weight basis as detected at 101degrees 
Centigrade. 
Table 10 below lists products obtained in a representative sample resulting 
from materials processed in Example IV: 
TABLE 10 
______________________________________ 
Yield from One-Ton Sample 
PRODUCT SUBCOMPONENTS POUNDS 
______________________________________ 
Primary Alloy 342.08 
Cu 342.0 
Ni 0.04 
Cr 0.03 
As 0.01 
Volatile Metals 
Zn 45.36 
Secondary Alloy None 
Slags from Oxides 790.25 
Ca 360.00 
Si 274.46 
Al 114.17 
Inerts 25.35 
Mg 12.40 
S 2.68 
F 1.17 
Ba 0.01 
Cr 0.01 
Mineral Wool from Slag 592 
Shot 197 
______________________________________ 
The resulting Acid:Base ratio is 1.11. Basicity is 0.96. Exhausts, heavy 
solids, and shot are recycled into the system, and no wastes result. 
From the foregoing, it will be seen that this invention is one well adapted 
to obtain all the ends and objects herein set forth, together with other 
advantages which are inherent to the structure. 
It will be understood that certain features and subcombinations are of 
utility and may be employed without reference to other features and 
subcombinations. This is contemplated by and is within the scope of the 
claims. 
As many possible embodiments may be made of the invention without departing 
from the scope thereof, it is to be understood that all matter herein set 
forth or shown in the accompanying drawings is to be interpreted as 
illustrative and not in a limiting sense.