Preheating glass batch

A method and apparatus for preheating particulate glass batch comprises a rotatable drum for mixing the batch with particulate heat transfer media in a heat transfer relationship where the batch is separated from the media in a media exit vestibule having a screen through which the batch passes and having compartments mounted for rotation about the axis of the drum for lifting the separated batch to the batch inlet conduit where it is directed back into the drum.

TECHNICAL FIELD 
This invention relates to a process for preheating glass batch which is 
then fed to a glass-melting furnace. 
BACKGROUND OF THE INVENTION 
One method for preheating glass batch involves feeding cold particulate 
glass batch raw materials into one end of a rotating heat-transfer drum, 
and feeding hot media of larger particle size than the batch particles 
into the other end of the heat transfer drum. The glass batch moves in 
direct and immediate physical contact with the heated media, with the 
batch flowing from the cold end to the hot end of the drum and the media 
flowing from the hot end to the cold end of the drum. The heated 
particulate batch is removed from the hot end of the drum, and the cooled 
media is removed from the cold end of the drum. Preferably, the heat 
transfer media is of a durable material and can be comprised of glass 
batch agglomerates, glass, ceramic material, steel, stainless steel, 
aluminum, or gravel. The media can be spherical in shape, and a useable 
example of such media is spherical ceramic balls. The media can be heated 
with an external burner or preferably heated by direct contact with 
exhaust gases from a glass melting furnace. 
A problem with such a preheating apparatus and method is that the cold 
balls exiting the heat transfer drum carry some of the particulate glass 
batch with them. This is undesirable because the particulate glass batch 
can melt and foul the heating apparatus for reheating the balls prior to 
their reintroduction into the heat transfer drum. There is a need for 
separating particulate batch material from the heat transfer media as the 
heat transfer media is discharged from the heat transfer drum. 
SUMMARY OF THE INVENTION 
According to this invention, there is provided apparatus for preheating 
particulate glass batch comprising a rotatable container for mixing said 
batch with particulate heat transfer media in a heat transfer 
relationship, the heat transfer media being larger in particle size than 
the batch, and a media exit vestibule for separating the media from the 
batch comprising a generally cylindrical screen mounted for rotation about 
its symmetrical axis, the screen having openings sufficiently small to 
prevent the passage of the media therethrough and sufficiently large to 
enable the passage of the batch therethrough, carrier means mounted for 
coaxial rotation with the screen for lifting the separated batch, and 
means for directing the separated batch from the exit vestibule into the 
container. 
In a specific embodiment of the invention the carrier means comprises a 
plurality of compartments defined by a cylindrical surface rotating 
coaxially with the screen and by a plurality of baffles mounted between 
the screen and the surface. 
In a preferred embodiment of the invention the means for directing the 
separated batch comprises a batch inlet conduit. 
According to this invention, there is also provided apparatus for 
preheating particulate glass batch comprising substantially spherical heat 
transfer balls which are larger in size than the batch particles, a 
cylindrical drum mounted for rotation about its symmetrical axis for 
mixing the batch with the balls in a heat transfer relationship, a batch 
inlet conduit for directing batch into the drum, and a ball exit vestibule 
for separating the balls from the batch comprising a cylindrical screen 
mounted for rotation about the axis, the screen having openings 
sufficiently small to prevent the passage of the balls therethrough and 
sufficiently large to enable the batch to pass through the screen, a 
plurality of compartments mounted for rotation about the axis for lifting 
the separated batch and for depositing the separated batch in the batch 
inlet conduit. 
In a preferred embodiment of the invention, the separated batch falls to 
the bottom of the exit vestibule and the compartments are adapted to lift 
the separated batch to the top of the exit vestibule. 
In the most preferred embodiment of the invention the balls are lifted from 
the bottom of the drum to the exit vestibule with a scroll. 
According to this invention, there is also provided a method for preheating 
particulate glass batch comprising rotating a container to mix the batch 
with particulate heat transfer media in a heat transfer relationship, 
passing the media into a rotating media exit vestibule, separating the 
batch from the media, lifting the separated batch, and directing the 
separated batch from the exit vestibule into the container. 
According to this invention, there is also provided a method for preheating 
particulate glass batch comprising rotating a cylindrical drum about its 
symmetrical axis to mix the batch with particulate heat transfer media in 
a heat transfer relationship, directing batch into the drum via a batch 
inlet conduit, passing the media into a media exit vestibule mounted for 
rotation about said axis, separating the batch in the exit vestibule from 
the media by passing the batch through a screen and into a plurality of 
compartments, and rotating the compartments about the axis to lift the 
separated batch and deposit the separated batch in the batch inlet conduit 
.

DESCRIPTION OF THE INVENTION 
This invention will be described in terms of a glass particulate batch 
preheating operation, although it is to be understood that the term 
"glass" includes other heat-softenable mineral material, such as rock, 
slag, and basalt. 
As shown in FIG. 1, the heat transfer media can be heated in preheat hopper 
10 and transferred via media conveyer 12 which deposits the media into a 
rotatable container, such as heat exchange drum 14 via media charge 
conduit 16. Preferably, the media is heated by exhaust gases from a glass 
making furnace, although it can be heated by other means. The heat 
exchange drum can be mounted on bearings 18 for rotation about axis x-x, 
preferably inclined at a small angle to the horizontal. Particulate glass 
batch material 40 supplied from batch supply 20 is transported on batch 
conveyer 22 and discharged into the heat exchange drum by means of batch 
inlet conduit 24. The cold batch material travels in a direction opposite 
that of the hot heat transfer media and is discharged from the heat 
transfer drum through batch discharge screen 26 at the hot end of the heat 
transfer drum as hot batch stream 28. The hot batch discharge stream is 
supplied to the glass melting furnace. The heat transfer media travels 
from the hot end of the heat transfer drum to the cold end of the heat 
transfer drum through media exit vestibule 30 and is conveyed by media 
discharge conduit 32 and return media conveyer 34 for return to the 
preheat hopper. 
As shown in FIGS. 2, 3, and 4, at the cold end of the heat transfer drum is 
positioned scroll 36 and the media exit vestibule. The scroll is mounted 
for rotation with the drum to lift media 38 from the bottom of the drum to 
a higher position where the media can fall into the exit vestibule. 
Preferably, the scroll is a helical screen with openings small enough to 
prevent the heat transfer media from passing therethrough, but large 
enough for the batch to pass therethrough. 
The exit vestibule is comprised of a generally cylindrical screen, such as 
discharge screen 42, mounted for rotation about its symmetrical axis, and 
carrier means 44 mounted for coaxial rotation with the discharge screen 
for lifting the batch passed through the screen. The axis of rotation of 
the screen can be axis x-x. The screen supports the media and has openings 
large enough for the particulate batch to pass therethrough but small 
enough so that the media does not pass through. The carrier means can be 
any suitable means for lifting the separated batch, i.e., the particulate 
batch passed through the screen. Preferably the carrier means comprises 
compartments defined by cylindrical surface 46, which is the outside of 
the exit vestibule, and baffles 48 positioned between the screen and the 
cylindrical surface. The compartments, being part of the exit vestibule, 
rotate from the bottom of the exit vestibule to the top of the exit 
vestibule to lift the separated batch and drop it onto a means for 
directing the batch into the heat transfer drum. Preferably, the means for 
directing the batch into the heat transfer drum is the batch inlet 
conduit. 
In operation, the hot heat transfer media, such as ceramic balls, travel to 
the cold end of the heat transfer drum, are lifted by the scroll, and fall 
into the exit vestibule. There, particulate batch is shaken from the balls 
and the batch passes through the discharge screen, where it is lodged in 
one or more of the compartments. The balls continue to fall through the 
exit vestibule and out into the media discharge conduit. The rotation of 
the compartments lifts the separated batch to a position above the batch 
inlet conduit where the batch falls into the batch inlet conduit and is 
diverted back into the heat transfer drum, or into the interior of the 
scroll, which is positioned in the heat transfer drum. 
It will be evident from the foregoing that various modifications can be 
made to this invention. Such, however, are considered as being within the 
scope of the invention.