Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGR~UND OF THE INVENTION
This invention relates to an oven for treating web
stock, especially cloth stock in a tentor frame, and more
particularly to such having special gaseous recycling.
In the typical treatment of textile fabric during
manufacture thereof, a generally continuous web of fabric is
ultimately passed through a tentor frame for stretching and
drying of the textile held by tentor hooks or the equivalent
along the edges of the web. Heated gases are forced over
and through the stretched fabric in substantial volumes for
drying. During this process, the temperature of the gases
must be limited to a predetermined maximum to avoid damage
to the fabric due to overheating during drying or during the
post-drying heat treatment. Consequently, it is typically
necessary to ha~e several tentor frame dryer sections in
series to achieve effective drying and post-drying heat
treatment. Such equipment requires substantial capital
outlay, space, and heat input. A great share of this gen-
erated heat is exhausted to the atmosphere and lost in the
volumes of gases discharged. These gases are laden with
varying amounts of liquids removed from the fabric during
drying. When processing double knit fabrics, such liquids
typically include oily compounds deposited on the fabric
during the previous ~nitting operation, solvents, and
carriers for the dyes. These are carried by the drying
gases, in minute form and often partially combusted, into
the atmosphere as smoke and fine mist. This of course is
not ecologically desirable. Furthermore, some of the oily
sub~tance has a tendency to condense and coat the equipment
interior and cause potential problems and fabric damage.
In sum, it is recognized in the trade that present
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1 tentor dryer equipment, though effective, is expensive and
space consuming to the fabric mills. Not only the fabric
mills, but also the public in general is encumbered with
higher fuel costs and fabric costs due to the tremendous
quantities of fuel necessary for the tentor dryers. And the
public also has the ecological disadvantage of undesirable
stack discharges. Though such discharges are questionable
as to meeting governmental guidelines, the mills have not
heretofore had available to them tentor dryers that are
effective in this regard.
SUMMARY OF THE INVENTION
The present invention effectuates more efficient
and rapid drying and heat treatment of web stock, partic-
ularly textile fabric, in a tentor, using less fuel and less
equipment, and resulting in ecologically improved, con-
trolled stack discharge. Using the invention, moisture and
oil compounds are removed from textile fabric such as
knitted polyester materials in a fashion significantly
reducing fuel consumption and curbing pollution-causing
stack discharge. With the special flow circuit and apparatus
of the invention, the combustible volatile oil, solvent,
and carrier type materials removed from the textile material
during evaporation of the moisture are combusted in a
special c~amber, at a relatively higher temperature, the
resulting gases being subsequently cooled with supplemental
fresh air, with part of the gaseous stream then being
returned to the oven for evaporation of moisture and oil
products from additional web stock, and for preheating
and/or post heating of the stock.
3Q An advantageous feature of the invention is its
adaptability to existillg equipment, particularly tentor
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1 frames presently used for drying and heat treating of cloth.
The invention renders available to textile mills the capacity
to control stack discharge for curbing air pollution of
combustible materials to meet pollution control standards.
Yet, the amount of actual equipment is considerably lessened
over that previously required, rather than increased as
might be expected. And, furthermore, fuel requirements are
markedly lowered from previous requirements. Experimental
operation on a trial basis under actual textile mill con-
ditions shows that the invention enables substantial fuel
conservation, increased production rates and/or less equip-
ment for present production rates, and curbed stack output
for pollution control
Conversion of even existing tentor apparatus is
]5 accomplished without great difficulty and with immediate
benefits.
Because the invention was conceived and developed
for drying and heat treating of textile stock, and is par-
ticularly useful for such, it will be described herein
chiefly in this context. However, it is believed that the
concept in its broader aspects could be adapted to heat
treatment of other web stock also where combustible pol-
lutants are driven off the stock, e.g. paper, wood, polymer
stock and the like.
These and several other advantages, features and
objects of the invention will be apparent upon reviewing the
following detailed disclosure.
BRI~F DESCRIPTION OF THE DRAWIN~S
Fig. 1 is an elevational view of a five zone
tentor apparatus employing the invention;
Fig. 2 is an end elevational view of the input end
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1 into zone 1 of the apparatus in Fig. l;
Fig. 3 is a sectional, end, partially schematic
view of one of the zones in Fig. l;
Fig. 4 is a fragmentary, side elevational view of
the zone in Fig. 3;
Fig. 5 is an elevational view of a conventional
eight zone tentor which was replaced by the apparatus in
Fig. l; and
~ig. 6 is a schematic diagram of a second embodi-
ment of the concept.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The manufacture of cloth fabric at textile mills
typically involves use of a tentor or tentor frame by which
the fabric is stretched and heated to dry the fabric, and
usually to heat treat the fabric. Treatment of double knit
polyester fabric, for example, typically involves removal of
moisture quantities of 15 to 40% by weight and heat treating
the fabric, both while the fabric is in a stretched co~-
dition. In this type of operation, temperatures of 350 to
375F. should not be exceeded, to avoid damage to the fabric
by fusion or the like.
It is significant that, during the formation of
the fabric as by knitting, oils and solvents such as needle
oil, sludge solvents, metallic cleaners and other organic
compounds, are typically employed. As the polyester knit
cloth is dried in the conventional tentor, smoke is emitted
as a result of the oils and solvents present in the cloth
and volatilized therefrom by the heated drying gases. Some
of ~his oily material recondenses inside the tentor housing,
some of it reconden~es on the roof areas of the building at
the stacks, and some is ejected into the atmosphere as smoke
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1 to the disadvantage of personnel, plants, and structures in
the area.
The degree of effectiveness of conventional
tentors in drying and heat treating cloth is dependent upon
flow of vast quantities of hot gases. The gases are heated
to approximately 350 to 375F., passed over the stock, and
exhausted at temperatures of approximately 250F. These
tentor units are typically formed of ten foot length sec-
tions, each several feet wide. The fabric is stretched, for
lQ example, from a width of about 48 inches to about 63 inches
or so, during which and subsequent to which several pounds
of water per minute are evaporated for lowering the moisture
content from about 15 to 40% by weight to a few percent.
This also results in evaporation of substantial quantities
of k,nitting oil (light machine oil), solvents, dye carriers
and other chemicals from the fabric, The discharge from
these tentor units results in tremendous heat loss up the
stack. Increased fuel costs in recent years has rendered
these heat losses very serious. Further, meeting recent
pollution control standards has been all but impossible with
equipment heretofore available to the textile mills.
Experimentation employing the present inventive
concept was conducted in an actual operating textile mill.
One experiment involved conversion of two specific zones of
a conventional seven zone tentor. The converted system was
operated for several months to determine and solve problem
areas, and to reduce the invention to practice. The results
were exciting and encouraging, both to the inventor hereof
and the managing personnel of the mill.
Referring now specifically to the drawings, the
prior art apparatus depicted in Fig. 5 constitutes a typical
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1 eight zone tentor through which the cloth stock in web form
would flow for removal of moisture from the cloth as the
cloth is held stretched on a tentor frame. Hot gases are
normally used for drying and also to heat treat the fabric.
The temperature of the inflowing gases is usually between
about 350 and 375F.
Typically, each zone of a conventional tentor of
the type employed, such as an "Artos" brand unit, will
exhaust from about 6,000 to about 8,500 cubic feet per
minute of hot gases at a temperature of about 300F. to
360F. If the flow rates are allowed to drop to less than
about 4,000 cubic feet per minute, the oil evaporated from
the cloth will tend to recondense in the equipment, to cause
problems within the equipment and on the fabric itself. To
attempt to incinerate the vaporized products in this volume
of air would require more heat input than for the drying
process itself. This necessity for such tremendous amounts
of air limits the production from the apparatus and causes
substantial heat losses. The hot exhaust gases are vented
from multiple zones of the conventional tentor 100 through a
series of exhaust stacks 102, each typically including an
exhaust fan 104 and motor 106 therefor.
Experimentation with this multiple zone tentor
showed that by conversion of two of the zones in the central
portion of a conventional seven zone tentor in accordance
with the present invention, only five zones total were
needed in the tentor 10 (Fig. 1) to obtain equal or superior
production output to a conventional eight zone tentor (as in
Fig. 5), at greatly reduced heat consumption, as well as
3a simultaneously achieving pollution control. Since the first
and last zones ~ere not employed, Fig. 1 is shown with the
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1 remaining five zones only, numbered consecutively as 1-5.
Zone 2 and zone 3 of the apparatus ~as depicted in Fig. 1)
employ the novel concept, zone 3 being shown in Fig. 3 in
cross section for illustration purposes, with zone 2 being
basically identical therewith.
~ach of the five zones, e.g. zone 3 shown at 10'
in Fig. 3, includes a housing 12 of generally rectangular
cross section, lined with insulation 14 and defining an
internal chamber 16 having an opening on both the inlet and
outlet ends comparable to the inlet opening 18 for zone 1
shown in the end view of Fig. 2. The web stock that passes
through these chambers successively, (indicated by phantom
line W in Fig. 3), is straddled above and below by a series
of hot gas manifolds or pipes 20 and 22 respectively which
project laterally, i.e. transversely of the stock direction
of travel. From orifices in these manifolds, hot gases are
e~ected downwardly and upwardly respectively, onto and
through the fabric stock as the advancing stock is held in a
stretched condition in conventional fashion by typical
tentor hooks or the equivalent. The tentor hooks are on
supports 24 at the opposite edges of the web stock. Mani-
folds 20 and 22 are mounted to and in flow communication
with conduits 30 and 32 respectively, both connected to and
receiving hot gases from a common supply conduit 34. These
components 20, 22, 30, 32 and 34 are conventional, as are
the tentor hooks and supports 24. However, instead of the
hot gases being vented directly to the atmosphere through
exhaust stacks as is conventionally done, such gases,
containing substantial quantities of evaporated water and
3Q vaporized oil and related solvent products, are specially
processed, resulting in significant advantages.
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L
1 Specifically, the hot gases emitted from manifold
pipes 20 and 22 engage and pass through and over the moving
stretched fabric, and then, laden with vaporized material,
flow out return duct 40 and preferably through a filter 42
across which an indicating manometer 44 may be mounted to
measure the pressure drop at the filter. The hot gases in
the 300F. plus range contain substantial quantities of
combustible vapor, largely oil and solvents, as well as
moisture. The oil, solvent, and carrier substances are
combustible at temperatures above about 600F., and often
temperatures in the range of about 1400F. The oils actu-
ally having kindling temperatures below 600F. but the organic
carriers usually have kindling temperatues above 600F.
But, temperatues this high cannot be tolerated in the oven
since such would seriously damage the cloth being treated.
According to the present concept, these gases are passed in
front of an elongated high velocity burner assembly 48, as
of the type set forth at Figure 3 and described in column 6,
Second Form, of U.S. Patent No. 3,436,065 entitled METHOD OF
DRYING A FOUNDRY LADEL, and also at 38 in U.S. Patent No.
3,744,963 entitled HEAT TREATMENT. Burner assembly 48 is
supplied with a mixture of gaseous fuel and air from mixer
47 to which air line 45 and gas line 43 connect. The burner
causes the combustion of the vaporized combustible oils and
solvents, the temperature thereof being raised to the incin-
eration range, i.e. above 600F. in plenum 50. A grid 52
adjacent the burner may be used to assist in effective dis-
persal for efficient combustion. Adjacent the grid and
burner assembly 48 is an elongated air supply manifold 54
having a series of orifices for directing air jets into the
gaseous flow from the burner. This accomplishes two things,
namely, supplying
g
1 oxygen for combustion of the oil and solvent substances in
the event the circulated air becomes saturated with moisture
and lacks oxygen, and secondly creating turbulence to
thoroughly nlix the hot gases from the burner with the
recirculated gases from the oven and fresh air from manifold
54. This mixture of gases at combustion range temperatures
is directed through plenum 50 which has, downstream from the
burner, fresh cooler air inlet means 58 controlled by
dampers 60. The introduced cool air controllably lowers the
temperature of the gases back down to drying range tempera-
tures, i.e. the range of about 350 to 375F. The tempera-
ture is controlled to the highest that is tolerable in the
oven for the particular fabric. The gas temperature is
sensed for control by a suitable high limit temperature
sensor 62 such as a thermocouple projecting into the plenum
to prevent the temperature from exceeding the maximum
allowed for the cloth. Part of these gases are then drawn
by blower 64 into duct 34, which may also include an added
temperature sensor 66. Sensor 66 operates a temperature
controller to control temperature in the tentor frame.
Sensor 66 could also be used to govern the amount of fresh
air allowed through inlets 58 for regulating the temperature
of the gases re-entering the oven. The le~s air that is
allowed to enter through inlet 58, the higher the temp-
erature is created in plenum 50 to maintain the temperature
required at sensor 66.
As noted, part of the gases from plenum 50 are
advanced by blower 64 back into the oven. The other part
passes into duct 70, drawn by blower 72, for advancement
either into a succeeding zone or a preceding zone of the
assembly. ~lore specifically, as depicted in Figs. l and 3,
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1 this other part of the gases from plenum 50 of zone 3 passes
through blower 72 and duct 73 into the succeeding zone 4
downstream, for heat treatment of the cloth passing through
the tentor. In contrast, the like apparatus to that de-
picted in Fig. 3, as applied to zone 2 (Fig. 1), has part of
the gases from plenum 50A returned back to zone 2 through
conduit 34A and blower 64A, and part propelled into any one
or more of the other zones, e.g. zone 1 through blower 72A
and duct 73A for preheating the cloth stock as it passes
through zone 1 to zone 2. Each of zones 1 and 4 includes a
plurality of manifold elements (such as 20 and 22 in Fig. 3)
for vertically straddling the cloth stock. The gases
exhausted from zone 1 are passed up through an exhaust stack
102 (Fig. 1) containing a conventional exhaust fan 104 and
motor 106 therefor. The gases exhausted from zone 4 are
shown transferred by blower 78 through conduit 80 to zone 5.
The exhaust from zone 5 is conducted out through an exhaust
stack 102. The number of gaseous recycle subassemblies as
in Fig. 3, the particular location of the stacks, and
arrangement of the conduits for flow from one zone to
another can be varied to suit the circumstances, equipment,
components and fabric conditions at the mill involved.
The embodiment set forth in Figs. 1 and 3 involves
recirculation of all of the gases from the s~lected oven
zones to the combustion chamber and back to the oven.
However, in some instances it may be desirable to recir-
culate only a fraction of the gases from the particular zone
to the combustion chamber as explained relative to the
embodiment in Figure 6.
Preferably, air curtain units 86 and 88 are
employed at the entrance to the first zone and at the exit
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1 to the last zone, these being for example of the type dis-
closed in more detail in U. S. Patent 3,744,963 at 22 and
24. This helps to lessen hot gas flow out the inlet and
exit for the stock.
Extensive experimentation with this apparatus has
shown that, by converting two of the conventional tentor
zones of a conventional eight zone assembly, to employ the
invention herein, the same production output can be achieved
using only five zones in lieu of the previously required
eight zones. Further, as close as can be determined, fuel
savings over 30~ have been achieved. It is expected that
savings as high as 60% can be achieved in some installa-
tions. The amount of hot gases exhausted to the atmosphere
is drastically cut to a small fraction of that previously
lS exhausted, i.e. in the range of about 25 to 30%. For
example, in the experimental apparatus, 1500 cubic feet per
minute of gases were handled, per zone, instead of the
previous 8000 cfm per zone. In fact, the exhaust rate is
considerably less than that even tolerable in previous units
because such a low exhaust rate would have dictated low gas
flow rates that would have resulted in the vaporized oil and
solvent products recondensing in the equipment and on the
textile material. With the novel apparatus, these unde-
sirable solvent and oil materials are actually taken ad-
vantage of, by combusting them using the burner assembly at
the added plenum of the recycle system, to clean up the
gases as well as achieving significant heat conservation
therefrom. Thus, the significantly smaller fraction of
gases that are actually exhausted are basically free of the
oil and solvent substances. If it were attempted to combust
the volatiles carried in the gaseous flow mass of the prior
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.Lti`~t~
1 art, the amount of heat necessary to simply heat up the
tremendous amount of gases, e.g. 6000 to 8500 cfm, would be
greater than the entire amount of heat otherwise needed for
the process of drying and heat treating.
The results of the invention therefor are in-
creased production and/or lower capital equipment costs and
requirements, significantly greater heat conservation, with
concomitant less fuel consumption and pollution control.
Another operating criterion for tentor frames is
that the faster the textile fabric can effectively advance
through it, the greater the efficiency thereof. Using the
invention, rates of fabric feed can be increased by over 30%
and often considerably more, yet with effective drying and
heat treating, thereby increasing efficiency per pound of
fabric processed as well as production output. Tentors
presently in use can be converted to employ the invention
without significant difficulty or great expense, resulting
in significantly improved operation and savings.
Referring to Fig. 6, a second embodiment of the
invention there shown as assembly 200 has a plurality of six
oven zones with an elongated passage through which web stock
entering one end of the oven passes before exiting at the
other end of the oven. Each zone includes a chamber in
which volatilizable material is removed from the stock
and/or the stock is heat treated by flow of hot gases.
Burner 248 and plenum 250 into which it fires has a com-
bination effect with a plurality of zones, specifically all
six in the depicted version. As shown, a portion of the hot
gases in each of zones 1-6 is recirculated while the other
portion is conducted to the burner (zones 2-5) or to a stack
(zones 1 and 6). The gaseous portion that is recirculated
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1 is mixed with the incinerated gases from the burner plenum
at re-entry into the oven. The incinerated gases may be
conducted back to the oven zones through a manifold arrange-
ment. And, the gaseous portion removed may be conducted
through a manifold arrangement to the burner.
More specifically, hot incinerated gases at a
controlled temperature from plenum 250 are conducted through
duct 234, which leads into manifold 234' and into branch
ducts 234a to respective blowers 264. The blowers also
receive a portion of the gases and vapors from the oven
zones through ducts 234b. The mixture of gases is forced
into the individual oven zones to the web stock. As to the
intermediate zones 2-5, the other portion of the gases and
vapors are ducted through exit ducts 265 into manifold 267
to exhaust duct 269 in which a supplemental blower 271
operates to propel these gases and vapors to burner 148 for
incineration of the combustible volatilized vapors at
temperatures in the range of about 450F. to about 1400F.
Supplemental air is ejected through outlets 254 adjacent
burner 248 for oxygen supply and turbulence generation. A
controlled amount of ambient temperature air is allowed to
enter the plenum past the valve at inlet 258 to lower the
temperature of the mixture of gases flowing therepast to
that tolerable for the material treated in the oven prior to
re-entry of the gases into selected oven zones. The lowered
temperature of the hot gases will vary, depending upon the
material, but for cloth will typically be about 350F. to
375F
A portion of the gases in the end zones 1 and 6 is
ejected out the respective stacks 202 under the influence of
blowers 204 operated by motors 206, rather than recircu-
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1 lated. Thus, there is constant incineration of the com-
bustible material in a portion of the gases and constant
venting of a graduated amount. The blowers 264 recirculate
the hot gases in the zones while pulling sufficient in-
cinerated gaseous products from the plenum 250 to maintain
temperature and replace gases being dra~n out of the oven,
mainly up the stacks. If desired, an additional stack can
connect to one of the intermediate zones.
For example, if 1500 cubic feet per minute ~cfm)
is circulated in each zone, about 300 cfm or so could be
withdrawn to the incineration burner, incinerated, cooled to
a lower elevated temperature and returned. Surplus from the
intermediate zones could be supplied to the zones from
wherein the gases contain no pollutants such as the first
zone and the last zone.
To be certain the ratio of organic carriers
commonly employed for cloth dyes to air is kept well below
the explosive range, sufficient dilution of noncombusted
carriers is practiced by controlled entry of air. Speci-
fically, the dilution factor is kept in the range of 3 to 1
up to 20 to 1 of air to carrier.
Although the specific illustrative embodiments
depicted employ gaseous fuel for direct heating in the
chamber, other fuels such as coal, coke or heavy oils could
conceivably be employed as for indirect heating of the
chamber to an incineration temperature. Or, electrical heat
could be utilized in some instances or as an emergency
standby.
Once the inventive concept is understood, it will
he realized by those in the art that details of the illus-
trative arrangement can be modified to suit a particular
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p~
1 installation, type of textile, size of mill) and other
factors, the illustrative version depicted being exemplary
of the concept.
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