System and process for abatement of casting pollution, reclaiming resin bonded sand, and/or recovering a low BTU fuel from castings

A low vacuum is applied to selected surface areas of a resin bonded sand mold to draw ambient air into selected portions of the mold. The air entering the mold burns out a significant portion of the resin binder to form a low BTU gas fuel and to recover casting heat for use in a waste heat boiler or other heat abstractions device. Therefore, foundry air pollution is reduced, the burned out portion of the molding sand is recovered for immediate reuse, and a savings in fuel and energy.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates to resin bonded sand molds and in particular to a 
system and process for reducing casting pollution, recovering a portion of 
the molding sand for immediate reuse, producing a low BTU gas fuel by 
partial combustion of the bonding resin, and recovering a portion of the 
casting heat. 
2. Description of the Prior Art 
Heretofore, current foundry practice employing no-bake molds and cores have 
separate ventilation and sand reclamation operations. Organic waste 
products are removed from molds and cores in dry scrubbers and transported 
to dumping sites for disposal; the scrubbed sand is returned for reuse. At 
the present time there is no practical use for recovered binder residues. 
Care must be exercised in disposing of the organic waste products, since 
they pose a potential problem for the environment. 
Present ventilation systems include the dilution of foundry air with large 
quantities of unpolluted air and removing the same from the foundry by 
forced air and/or induced air systems. The air removed from the foundry is 
exhausted into the outside atmosphere where air standards are still 
lenient enough to permit such operation. The existing systems must move 
huge quantities of air and are therefore expensive to install and maintain 
operation thereof. Additionally, extra fuel is required to preheat the 
make-up air for the foundry operation. 
Under normal foundry practice, large quantities of silica dust can be 
present in the foundry environment. This is particularly true in the areas 
devoted to pouring and shakeout operations. As stated in a volume of 
American Society for Metal's Handbook, silica dust can produce silicosis 
if there is sufficient exposure, in terms of time and concentration, to 
free crystalline silica dust of particle size below five microns. When 
silica dust concentrations greatly exceed the maximal allowable, a case of 
silicosis can develop within two to twenty years, the average being ten 
years. 
In no-bake molding practices employing organic foundry sand binders 
environmental effects must be considered for products of the thermal 
decomposition of the organic binders. The smoke and thermal decomposition 
products require control equipment. Thermal decomposition products 
include, but are not limited to, carbon monoxide, carbon dioxide, 
nitrogen, hydrogen, methane, formaldehyde, ammonia, hydrogen cyanide, 
acetylene, ethane, paraffin hydrocarbons, aromatic organic compounds, and 
the like. 
The three major sand reclamation systems currently available to foundrymen 
using no-bake sands are thermal, wet and dry scrubbing. Thermal 
reclamation is the most expensive system to install and operate, but 
produces the cleanest reclaimed sand. A thermal reclaimer requires in the 
order of 1.5 million BTU's of heat per ton of sand, or 4.5 million BTU's 
per ton of metal cast, at 3:1 sand to metal ratio to remove up to 96 
percent of organic binder residues from any organic no-bake sand mold 
system. The thermal reclamation system is seldom employed in the industry. 
A wet reclamation system is less expensive to operate than a thermal 
reclamation system, but more expensive than a dry scrubbing system. A wet 
reclamation system will remove from 35 percent to 45 percent of the 
organic binder residue from the used no-bake molding sand system. However, 
the sludge byproduct of the wet reclamation operation requires an 
environmental safe disposal site. 
A dry scrubber system is the least efficient system to reclaim used no-bake 
foundry sand, its efficiency being of the order of removal of from 25 
percent to 35 percent of the binder residues from the sand processed for a 
shotblast type dry scrubber. This process is employed most often because 
of its low cost installation. 
In the dry scrubber system of reclamation, the sand is crushed and its 
surface abraded resulting in up to 20 percent of the sand processed being 
lost because of "dust losses". The wet reclamation system has a less 
severe "dust loss" process and the thermal system has the least "dust 
loss" problem. 
The binder residues removed by the sand reclamation system have no 
practical use at this time and their disposal method is dumping. 
An object of this invention is to provide a new and improved system and 
process for casting metals in no-bake sand molds. 
Another object of this invention is to provide a new and improved apparatus 
and process for reducing air pollution in foundries employing no-bake sand 
molds. 
A further object of this invention is to provide a new and improved 
apparatus and process for causing air to flow through selected regions of 
a no-bake sand mold to thermally decompose the organic binder therein to 
produce a gas having a low BTU content. 
A still further object of this invention is to provide a new and improved 
system for insitu thermal recovery of sand from a no-bake sand mold, 
producing a gas therefrom that has a low BTU content which is storable or 
can be utilized in several ways for preheating air, and water, for 
providing heat as required in the foundry. 
Another object of this invention is to recover the casting heat from the 
casting during the cooling cycle. 
BRIEF DESCRIPTION OF THE INVENTION 
In accordance with the teachings of this invention there is provided a new 
and improved mold system and process for no-bake casting mold assemblies. 
Each mold assembly comprises a cope, a drag and a no-bake foundry sand 
composition including an organic binding material. The improved system 
includes a mold assembly disposed on a vacuum plenum. The mold assembly is 
oriented with the plenum so that the bottom surface of the mold assembly 
has good air and gas communication means with the vacuum plenum. A 
communicative means joins a vacuum source means, such as a blower, to the 
vacuum plenum member. When operative, the vacuum source means induces the 
ambient about the mold assembly to flow through the mold and into the 
vacuum plenum member. 
The new and improved system permits an operator to collect a low BTU gas 
comprising gas products and condensate matter evolved by the mold assembly 
into the vacuum plenum member. Combustion air may be mixed with the 
collected gas products and condensate matter to form a combustible 
mixture. The combustible mixture may be burned to preheat combustion air 
as required, produce hot water, or to enable one to heat treat castings in 
the mold assemblies.

DESCRIPTION OF THE INVENTION 
With reference to FIGS. 1 and 2, there is shown a mold assembly 10 
comprising a cope 12, a drag 14, and a perforated support member 16 having 
walls 18, 20, 22 and 24 defining plenum chamber therein. Organic resin 
bonded sand is shaped on a pattern to form the cavity to be cast therein. 
The member 16 supports the mold assembly 10 and may be sealed at its 
juncture with the bottom of the mold assembly 10 to provide a good 
air-tight-seal therewith. In a similar manner an air tight seal is 
provided by the abutting surfaces of the cope 12 and drag 14. Walls 26 
define a plurality of apertures extending entirely through the wall 20 to 
provide a communicant means for air to flow. 
Vacuum means, not shown, are attached to the support member 16, and when 
operative, cause air to draw downward through the mold assembly 10 from 
the top surface 30, through the apertures defined by walls 26 and 28 
respectively. The vacuum is applied shortly before casting of the melt. 
The vacuum is maintained during casting and at least a portion of the time 
after casting is complete and before shake-out occurs. The air which is 
drawn into the sand of the mold is heated by the cast metal in the regions 
of the sand about the metal casting thereby forming an initial hot sand 
zone. The heat is sufficient to make the sand become incandescent. The 
heated air supports combustion of the organic binder residues and 
increases the heat content of the air causing the initial hot sand zone to 
grow greater in size and to extend further from the casting toward the end 
and side surfaces of the mold assembly 10. An ever increasing amount of 
organic binder material is burned out of the sand mold. The greatest 
growth of the hot sand zone is that portion of the mold assembly 10 in 
direct communication with the vacuum means. Approximately 50 to 70 percent 
by volume of the sand can be burned free of its organic binder materials. 
In the no-bake mold making system to which this invention is directed, the 
organic binder system or material comprises from 1 percent to 2 percent by 
weight of the sand composition and include furan, alkyd resins, phenol 
formaldehyde, phenolin, phenolic urethane, and the like materials. The 
particular choice of binder material depends upon the type of casting 
practice followed, type of molds being used, and particularly the time 
allotted to mold preparation to meet the economics of a particular foundry 
operation practice. Furans and alkyd resins normally set slowly while 
phenolics and polyurethanes are known to set faster. The choice of binders 
is determined by foundry practice, preference, and/or economics. 
The volume of air and the flow rate of air can both be controlled in this 
system to enable one to produce a low BTU gas content in the hot gases. 
The hot gases which include the low BTU gas therein, are recovered to be 
burned in a waste heat boiler and/or a heat recovery unit to extract the 
heat values from the low BTU gas as well as the casting heat content of 
the gas. The low BTU gas and hot gas mixture may also be employed as a 
means for providing heat in hot top casting practices. 
The burn-out efficiency of the process, as well as the BTU content of the 
low grade gas is dependent upon the type of molding equipment employed, 
the configuration of the casting to be poured, the molding sand to cast 
metal ratio, the amount of sand mold surface exposed directly to the 
surrounding ambient in the foundry, and the design of the system to cause 
the air to be drawn through the mold and to transport the gases from the 
mold to a particular distant point. Should the ambient air of the foundry 
be drawn in over the whole mold surface, the low BTU gas formed is diluted 
by the excess air drawn through the mold. Should the mold surfaces be 
sealed completely against the entrance of air by such suitable means as a 
spray coating material, sheets of material, and the like, the only air 
able to enter into the mold will be drawn into the mold around 
incandescent portions of mold surrounding the pouring cup, gate, and open 
risers which project to the top mold surface. The combustion of air and 
organic binder material produces a low BTU gas. The combustion, or burning 
of the organic resin binder material usually occurs in a straight line 
from the initial point of combustion to the perimeter of the casting and 
then fairly directly toward the plenum chamber of the support member 16. 
Some expansion of the initial burned out regions occurs as a result of 
heat conduction and gas diffusion into the abutting no-bake sand 
composition. 
Upon completion of casting the molten metal and further combustion of the 
organic binder materials cannot be achieved, the vacuum may be increased 
to draw greater quantities through the mold in order to cool the casting 
faster. For best all around results, cooling of the casting should be 
achieved through a separate air evacuation system. 
Castings made in this manner have been evaluated and found to have better 
qualities because of less surface gas in contact with the casting and 
surface roughness has also been reduced from prior art casting methods. 
As illustrated in FIG. 2, the vacuum means may be supplied by a blower 50 
which mixes the low BTU gases with a sufficient quantity of air to fire a 
waste heat boiler 52. Means for transporting the low BTU gas from each 
mold 10 to the blower 50 may be conduit means 54 and 55, a valve means 61, 
and conduit means 54 in the floor 56 controlled by flow valve 58. In this 
instance the combustion of the low BTU gas from the mold 10 is employed to 
produce steam for operating foundry equipment. 
Additionally, a blower 60, via valve means 62 and conduit means 63, may 
direct the flow of low BTU gas produced through a condenser 64. The 
condenser 64 enables one to recover the casting heat and to separate tarry 
oil from the gas via valve means 66 before directing the gas to storage 
tank 68. Valve means 70 enables one to draw low BTU gas to fire casting 
heat treat and/or hot-top accessory means as required. 
Valve means 72 enables the combustible gas mixture from blower 50 to be 
directed via conduit means 74 to hot top and/or heat treating accessory 
means 76 as required for each mold assembly 10. 
The system and method of this invention enables the using foundry to 
substantially reduce air pollution of the ambient of the foundry. Whereas 
prior casting methods released large amounts of hot gases and particulate 
matter into the foundry air, the system and method of this invention draws 
the hot gases and particulate matter into a confined area to be disposed 
of properly without contaminating the foundry air about the work stations 
therein. The castings produced are of excellent quality and are readily 
shaken out of the "burned" sand. The "burned" sand is readily reclaimed 
for reuse without introducing pollution problems of sludge and the like 
which occurred in the prior art methods. The no-bake sand composition 
which has not had the organic binder burned out constitutes only 30 to 50 
percent by volume of the original sand composition of the mold. This 
portion of the original volume of sand composition employed in the mold is 
recovered crushed, screened and combined with the reclaimed sand of this 
process, cooled and returned for reuse. Pollution problems are greatly 
reduced by this method. 
The following example illustrates the teachings of this invention: 
Two MES scab plate mold assemblies were prepared in matchplate flasks using 
PEPSET.TM. and Wedron 5010 sand. PEPSET is the registered trademark of 
Ashland Chemical Company for a patented phenolic-urethane three part 
binder system. One part contains a phenolic resin, a second part contains 
an isocyanate component, and a third part consists of a liquid catalyst. 
One mold assembly was employed as a control. No attempt was made to seal 
any of the top surfaces of the mold to restrict air penetration or gas 
evolution. 
A 12" by 14" aluminum jacket was inverted and placed on the foundry floor 
to act as a vacuum plenum for the second mold assembly. A first neoprene 
rubber seal provided an air tight seal between the floor and the jacket. 
The second mold assembly was disposed on the other side of the jacket with 
a second neoprene seal affixed to the assembly and the jacket to provide 
an air tight seal therebetween. An industrial vacuum cleaner purchased 
from Sears, Roebuck and Company was attached to the vacuum plenum to 
provide the vacuum means. 
The industrial vacuum cleaner was turned on and a considerable current of 
air could be felt entering into the mold through the top surface 
indicating a good air tight seal obtained through employment of the 
neoprene seal. Gray iron was poured into the two molds. The pouring 
temperature was 2700.degree. F. The molds were then observed for a period 
of 45 minutes following the pour. No attempt was made to collect 
condensate matter. 
The vacuum assembly reduced the smoke levels considerably. No smoke was 
evolved from the vacuumed mold until traces were observed at 20 minutes 
following the pour, while smoke from the control mold was light to 
moderate. 
Visual examination of the castings revealed that there was no increase in 
penetration of the vacuum casting when compared with the control casting. 
The surface of the castings was acceptable for commercial quality. The 
vacuumed mold was more thermally reclaimed, about 70 percent of the binder 
had been burned out, than the control mold. 
Condensate matter was observed collected in the cannister of the vacuum 
cleaner. 
Further evaluation of the system and method of this invention indicates the 
vacuum type system works more efficiently with casting processes wherein 
high thermal energy is present in the mold such as iron, steel, copper 
alloy castings and the like. Less efficiency in burnout and shakeout is 
achieved in low thermal energy molds such as obtained in aluminum 
castings. In all instances foundry air contamination is substantially 
reduced. The low BTU gases evolved in the vacuum casting process of this 
invention range from 90 BTU's per 1000 cubic feet to 180 BTU's per 1000 
cubic feet depending upon the type of organic binder and casting 
temperature. The low BTU gases have proven to be an excellent source of 
fuel for waste heat boilers, heating hot tops, heat treating the castings 
in the mold assembly, and the like.