U.S. patent number 3,622,748 [Application Number 04/539,348] was granted by the patent office on 1971-11-23 for electric heating system for asphalt equipment.
Invention is credited to William W. Sellers.
United States Patent |
3,622,748 |
Sellers |
November 23, 1971 |
ELECTRIC HEATING SYSTEM FOR ASPHALT EQUIPMENT
Abstract
A tank-heating system for fluids, such as asphalt, in which an
electric tank-heating means extends generally horizontally within
the tank for producing heat which is absorbed by the contents of
the tank. A conduit provides a flow path for the flow of a second
fluid, such as oil, to be heated by the contents of the tank. The
conduit extends within the tank and is positioned in the region
above the proximate to the tank-heating means so that the fluid
passing through the conduit is in effective heat exchange
relationship to the tank-heating means and the contents of the tank
in the region. A second electric heating means is associated with
the conduit for applying heat directly to the fluid flowing through
the conduit. The tank-heating means, the conduit and the second
heating means are structurally interconnected so as to form a
unitary assembly for installation within the tank as a single
unit.
Inventors: |
Sellers; William W. (King of
Prussia, PA) |
Family
ID: |
24150844 |
Appl.
No.: |
04/539,348 |
Filed: |
April 1, 1966 |
Current U.S.
Class: |
392/456; 122/33;
126/343.5A; 222/146.5; 392/468; 392/489 |
Current CPC
Class: |
F24H
1/225 (20130101) |
Current International
Class: |
F24H
1/22 (20060101); H05b 003/82 (); F24h 001/00 () |
Field of
Search: |
;219/421,325,302,303,306,280-283,310-312,314-316,320-326,378,530
;126/343.5,343.5A,344,362 ;222/146,146HE,146HS,146H
;122/33,37,16 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,154,352 |
|
Oct 1957 |
|
FR |
|
1,342,061 |
|
Sep 1963 |
|
FR |
|
126,754 |
|
Jul 1928 |
|
CH |
|
Other References
Licentia, German Application No. 1,113,079, published 8-24-61,
219/325, (1 sht drwg.; 2 pp. spec.)..
|
Primary Examiner: Bartis; A.
Claims
I claim:
1. A heating system for use with a storage tank for fluids such as
asphalt or other similar fluids which are solid or viscous under
unheated conditions, comprising a tank, a first heating means
extending generally horizontally within the tank for delivering
heat to a heating zone within the tank, a conduit means providing a
flow path for the flow of a fluid, said conduit means extending
generally horizontally within the tank and having a substantial
portion positioned above and proximate to said first heating means
and within the vertical confines of said heating zone whereby the
fluid passing through said conduit means is in effective heat
exchange relationship with said first heating means and the
contents of the tank within said heating zone, and second heating
means extending generally horizontally within the tank associated
with said conduit means for applying heat to said fluid passing
through said conduit means, said first and second heating means and
said conduit means being structurally interconnected at the ends of
their horizontal extent so as to form a unitary assembly for
installation within the tank.
2. A heating system for use with a storage tank for fluids such as
asphalt or other similar fluids which are solid or viscous under
unheated conditions, comprising a tank, a first heating means
extending generally horizontally within the tank for delivering
heat to a heating zone within the tank, a conduit means providing a
flow path for the flow of a fluid, said conduit means extending
within the tank and having a substantial portion positioned above
and proximate to said first heating means and within the vertical
confines of said heating zone whereby the fluid passing through
said conduit means is in effective heat exchange relationship with
said first heating means and the contents of the tank within said
heating zone, and second heating means associated with said conduit
means for applying heat to said fluid passing through said conduit
means, said first heating means comprising a plurality of spaced
elongated heating members located at the bottom of the tank, said
heating members defining the border of said heating zone whereby
said heating zone has a substantial width and length, said conduit
means having an elongated portion adapted to be heated directly by
second heating means and a portion cooperating with said elongated
portion to form at least one loop which extends across said heating
zone.
3. A heating system according to claim 2 wherein said elongated
portions of said conduit means comprises an inner pipe and an outer
pipe defining an annular flow path for the fluid which flows
through the space between said pipes.
4. A heating system according to claim 2 wherein said first and
second heating means are comprised of electrical heating
elements.
5. A heating system according to claim 2 wherein said first heating
means comprises electrical heating elements.
6. A heating system according to claim 2 wherein said second
heating means comprises electrical heating elements.
7. A heating system for use with a storage tank for fluids such as
asphalt or other similar fluids which are solid or viscous under
unheated conditions, comprising a tank, a first heating means
extending generally horizontally within the tank for delivering
heat to a heating zone within the tank, a conduit means providing a
flow path for the flow of a fluid, said conduit means extending
within the tank and having a substantial portion positioned above
and proximate to said first heating means and within the vertical
confines of said heating zone whereby the fluid passing through
said conduit means is in effective heat exchange relationship with
said first heating means and the contents of the tank within said
heating zone, and second heating means associated with said conduit
means for applying heat to said fluid passing through said conduit
means, said first heating means comprising a plurality of spaced
elongated heating members, said heating members defining the border
of said heating zone whereby said heating zone has a substantial
width and length, said conduit means having a pair of spaced
elongated portions adapted to be heated directly by said second
heating means and a conduit portion joining said elongated portions
and including a coil at least one loop which extends across said
heating zone.
8. A heating system according to claim 7 wherein said coil formed
by said conduit means comprises portions located directly above
said tank heating members of said first heating means.
9. A heating system according to claim 7 wherein said elongated
portions of said conduit means comprises an inner pipe and an outer
pipe, the fluid being arranged to flow in the space between said
pipes, said second heating means being located within said inner
pipe, and wherein said conduit means extends horizontally across
said heating members of said first heating means and including
elongated sections directly above and in contact with each of said
elongated heating members of said first heating means.
10. A heating system for use with a storage tank for fluids such as
asphalt or other similar fluids which are solid or viscous under
unheated conditions, comprising a tank, a first heating means
extending generally horizontally within the tank for delivering
heat to a heating zone within the tank, a conduit means providing a
flow path for the flow of a fluid, said conduit means extending
within the tank and having a substantial portion positioned above
and proximate to said first heating means and within the vertical
confines of said heating zone whereby the fluid passing through
said conduit means is in effective heat exchange relationship with
said first heating means and the contents of the tank within said
heating zone, and second heating means associated with said conduit
means for applying heat to said fluid passing through said conduit
means, said first and second heating means comprising a plurality
of heating elements extending horizontally across the bottom of the
tank and said conduit means comprising a plurality of elongated
elements extending horizontally across the bottom of the tank above
said first heating means, and including means for structurally
interconnecting said first and second heating means and said
conduit means in supporting relation to one another.
Description
This invention relates generally to heating systems and, more
particularly, to a heating system comprising a heater for the
contents of a storage tank in combination with a heat transfer
system within the tank for heating a fluid passed through a conduit
in the tank.
It is the general object of the invention to provide a heating
system of the indicated type wherein the tank-heating means and the
fluid heating means are constructed and arranged relative to one
another and relative to the tank contents so that there is achieved
a maximum of use of the energy input into the system to heat both
the contents of the tank and the fluid.
Briefly stated, the general object of the invention is achieved by
providing tank-heating means extending generally horizontally
within the tank and producing heat which is absorbed by the
contents of the tank. There is also provided a fluid system
comprising a conduit means within the tank located close to and
within the vertical confines of the tank-heating members so as to
receive heat from the tank contents at a relatively high
temperature. There is provided a fluid-heating means which produces
heat which will be absorbed by the fluid within the conduit means.
By this arrangement, the heat produced by the tank-heating means is
absorbed by the contents of the tank and transferred to the fluid
passing through the conduit means under an effective heat transfer
condition. Furthermore, since the conduit means for the fluid is
preferably placed above the tank-heating means, the rising heat
flow from the tank-heating means will pass over the conduit means.
Accordingly, there is provided a very effective heat exchange
relationship between the tank-heating means, the contents of the
tank, the fluid passing through the conduits and the oil-heating
means whereby a very high percentage of the heat produced by the
two heating means is absorbed. Also, in accordance with the
invention, there is provided large heat transfer surfaces to
increase the efficiency of the heating.
Another object of the invention is to provide a heating system of
the indicated type involving a substantial dwell time for the fluid
passing through the tank.
While, for the sake of simplicity of description, the invention
will be described as applied to a heating system for a storage tank
containing asphalt to be supplied to a bituminous concrete plant
and involving a heat transfer system for oil supplied to the plant,
it will be apparent that the invention is more generally applicable
to heating systems for storage tanks for materials other than
asphalt, such as for example, storage tanks for various chemicals,
caustics and similar materials. Moreover, fluids other than oil may
be involved.
The above and other objects and features of the invention will
become apparent from a consideration of the following description
taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic view illustrating a heating system in
accordance with the invention for an asphalt storage tank and
including an oil-heating system;
FIG. 2 is a side view of the tank-heating means and the oil-heating
means shown in FIG. 1;
FIG. 3 is a front end view of FIG. 2;
FIG. 4 is a side view of a modified form of tank-heating means and
oil-heating means in accordance with the invention; and
FIG. 5 is a front end view of FIG. 4.
In the form of the heating system shown in FIG. 1, there are
provided four tank heating members 10, 11, 12 and 13 arranged in
parallel relation to extend horizontally along the bottom of a
cylindrical storage tank 14 which is in a horizontal position. The
heating members are supported by suitable means so as to be spaced
only a small amount above the tank bottom in accordance with
conventional practice. Near their forward ends the heating members
are supported on a plate 15 which is welded to the front end 17 of
the storage tank 14, this front end 17 being shown in dashed lines
in FIG. 2. Each heating member comprises a tube 16 containing an
electrical heating element 18 extending longitudinally therein. The
electrical heating element 18 is preferably of the type disclosed
in my U.S. Pat. No. 3,045,097. The electrical supply for each
heating element 18 is provided from a suitable source connected to
the heating element through a terminal box 20 in accordance with
conventional procedure. By this arrangement heat is supplied to the
tank contents by the heating members from a generally rectangular,
horizontal heating zone the extremities of which are defined by the
two outer heating members 10 and 13 and planes extending across the
ends of the heating members. The heat supplied to the contents by
the heating members will be concentrated in this heating zone and
the region spaced vertically therefrom a certain extent. Asphalt
heated in this zone will rise vertically, cooler asphalt will flow
down the sides of the tank outside this zone to the heating area
providing convection circulation. Accordingly, the asphalt in this
lower heating region will be at a relatively higher temperature and
in a more fluid state than the asphalt to the sides and below this
heating area. The heating means will maintain the asphalt in this
lower region in a fluid state sufficient to permit flow to the
asphalt plant as will be described hereafter, the drain for the
tank 14 being connected to the tank bottom. Of course, the heat
transmitted from the heating members and the asphalt in the lower
region heated thereby will flow upwardly to maintain a relatively
high temperature for a substantial vertical extent.
Means are provided for delivering the asphalt from the bottom of
the tank 14 to the plant where it is to be used. Such means
comprises a drain line 22 connected at its upper end to the
lowermost portion of the tank 14 and containing a control valve 23.
The drain line 22 is connected at its lower end to one end of a
horizontally extending jacketed pipe 24 which is connected to the
inlet of a strainer 26. The outlet of the strainer 26 is connected
to the inlet of an asphalt pump 28. The discharge of the pump 28 is
connected to a jacketed pipe line 30 which extends upwardly and
then horizontally and has its outlet end connected to the supply
end of the plant. In this way, the asphalt at the lower portion of
the tank 14, which is maintained in a fluid state by the heating
members 10-13, is pumped through the drain line 22, the pipe 24,
the strainer 26 and the pipeline 30 to the plant as needed.
A bituminous concrete plant utilizes heated oil for various
purposes, such as for the heating of piping pumps, pug-mills and
other jacketed components of a plant that will freeze at shut down
and have to be heated to put back in operation. The heated oil
supplies the required heat to these components by circulating
through these jackets. After utilization by the plant, the oil is
delivered by return line 32, which has an inlet valve 34 at one
end. Line 32 is connected through a pump inlet valve 36 and a
strainer 38, to the inlet side of pump 40. Strainer 38 has a fill
valve 42 controlling flow to the inlet side thereof. The oil pump
discharge is connected by a line 44, having a control valve 46
therein, to the inlet of the oil heating means in accordance with
the invention. Connected to line 44 is a pump discharge line 48 and
valve 50. If it is desired to pump oil from system, valve 46 would
be closed, valve 36 open and oil can then be pumped through open
valve 50 into suitable container.
The oil-heating means comprises conduit means within the tank 14
defining a flow path for the oil in heat exchange relationship with
the contents of the tank and in proximity with the tank-heating
members 10-13. In FIG. 1, such conduit means comprises a pair of
conduits 52 and 54 extending horizontally from the front to the
rear of the tank. Each of these conduits 52 and 54 comprises a pair
of concentric inner and outer tubes 56 and 58, respectively. Each
of the inner tubes 56 is closed at its rear end and extends
outwardly from the front end 17 of the tank 14 through plate 15
into the terminal box 20 for a purpose to be described hereafter.
At the rear ends of the conduits 52 and 54 there is provided a
transversely extending pipe 60 which provides flow communication
between the outer tubes 58 of each conduit 52 and 54. By this
arrangement, there is provided an oil flow path consisting of a
pair of annular passages between each pair of concentric tubes 56
and 58 extending from the front to the rear of the tank and a flow
passage extending transversely between the rear ends of these
annular passages. The inlet 62 of the conduit means for the
oil-heating means is connected to the forward end of the conduit 52
while an outlet 64 is connected to the forward end of the conduit
54. By this arrangement, the oil flows into the annular chamber in
the conduit 52 by way of the inlet 62 and rearwardly therethrough
to the transversely extending pipe 60. After passing through the
pipe 60, the oil flows forwardly from the rear end of the conduit
54 to the outlet 64.
It will be apparent that the above-described arrangement provides a
very effective heat exchange relationship between the oil flowing
through the oil conduit means and the contents of the tank 14. By
reason of the annular flow passages provided by the conduits 52 and
54 there is provided a large heat exchange surface for the oil,
which, of course, improves the heat transfer between the asphalt
and the oil. Moreover, the oil conduit is within the heating zone
of the heating members described above whereat the temperature of
the asphalt is relatively high.
In order to assist the heating of the oil by the contents of the
tank, there is provided a separate heating means for the oil. This
heating means comprises a pair of electrical heating elements 68
arranged to extend longitudinally within the inner tubes 58 of the
oil conduits 52 and 54. The heating elements 68 for the oil-heating
means are also preferably of the type disclosed in my U.S. Pat. No.
3,045,097. The heating elements 68 are supplied from the same
electrical source as the elements 18 by way of the terminal box 20
in accordance with conventional electrical connections.
As is best shown in FIG. 3, each of the conduits 52 and 54 is
arranged to extend parallel to and above the heating members 10-13
for the tank 14. Moreover, each conduit 52 and 54 is arranged to be
approximately equally spaced from a pair of the heating members and
in relatively close relation.
By reason of the above-described arrangement there will be a very
effective heat transfer relationship between the tank-heating
members 10-13, the contents of the tank within the heating zone and
the oil passing through the oil conduit means. The heat produced by
the heating members 10-13 will be transferred to the asphalt which
is in heat exchange relationship therewith and will be transmitted
by way of this heated asphalt to the oil which is in heat exchange
relationship therewith. Thus, the heat produced by the tank heating
means 10-13 is transferred to both the contents of the tank and to
the oil passing through the oil conduit means. The oil-heaitng
means is also operative to heat the oil from the inside of the
conduit means and the heat produced by the oil heater is
transferred to the oil. It will be noted that if the asphalt on the
exterior of the oil conduit is at a temperature less than the oil
(a condition which could exist if the asphalt were delivered to the
tank in a relatively cold condition), this asphalt will be heated
by heat transferred from the oil.
The outlet 64 of the oil conduit means is connected through an
elbow 70 to a line 72 which is connected at its outlet end to the
oil supply portion of the plant, a control valve 74 being provided
in this line 72. As is shown in FIG. 3, the elbow 70 is provided
with a pressure switch 76 and a temperature indicator 78, which are
used in connection with the control of the heating system but are
not pertinent to the invention described herein.
As shown in FIG. 1, there is provided a plurality of pipes 80, 82,
84 and 86 having regulating valves 90, 92, 94 and 96, respectively,
connected therein. These pipes interconnect the oil system with the
jackets for the asphalt pipes 24 and 30 and direct flow
therethrough for heating the asphalt being delivered to the plant.
The valves may be adjusted to regulate the flow as desired.
The supply system shown in FIG. 1 may be automated as desired and
to this end there is provided a control panel 100 from which the
various automatic operations are controlled. It will be apparent
that the desired controls may be achieved by conventional means and
such controls form no part of the present invention.
In the operation of the heating system shown in FIG. 1, the asphalt
will be delivered to the tank 14 by way of a suitable inlet 102 in
the top thereof. The asphalt is generally delivered directly from
the refinery in insulated tanks so that the temperature of this
asphalt, as delivered, is generally higher than that of the oil
which is to be used by the plant. The tank heaters 10-13 serve to
maintain the asphalt in a fluid state and at a temperature such
that the plant may use the same. When the plant requires the
addition of asphalt, the valve 23 is opened and pump 28 is operated
to deliver asphalt from the drain line 22 through the pipe 24, the
strainer 26 and the pipe line 30 to the asphalt plant.
When the asphalt plant required hot oil, the valves 34, 36, 46 and
74 are opened and oil is pumped from line 32 through the strainer
38 to the inlet 62 of the oil conduit means. The oil flows
rearwardly through the annular passage in conduit 52, across
through the pipe 60 to the rear end of the conduit 54 and forwardly
through the annular passage therein to the outlet 64 of the oil
conduit means. From the outlet 64 the oil passes through the elbow
70 and the pipe line 72 to the oil supply for the asphalt
plant.
It will be apparent that as the oil flows through the conduit
system within the storage tank 14, its temperature will be raised
by reason of the heat transfer relationship between the oil and the
asphalt in the tank and the heat transfer relationship between the
heating elements 68 within the inner tubes 56 of the conduits 52
and 54. Moreover, it will be apparent that the heat exchange
relationship is very effective one involving large heat transfer
surfaces. Not only does the oil receive heat from the heated
asphalt externally thereof, but also the oil receives heat from the
heating elements 68 internally of the oil passages.
In FIGS. 4 and 5 there is shown another form of oil-heating conduit
in accordance with the invention. The arrangement here is
essentially the same as that shown in FIGS. 1 to 3. The only
essential difference is that instead of the transversely extending
pipe 60 between the rear ends of the two conduits 52 and 54, there
is provided an additional pair of loops in the flow path. The
structure for forming these loops comprises an elbow 110 connected
at one end to the rear end of the conduit 52 and at its other end
to a horizontally extending pipe 112. The pipe 112 is mounted on
top of the heating member 10 and extends in alignment therewith.
The elbow 110 extends at a 45.degree. angle with respect to the
horizontal in order to provide communication between conduit 52 and
pipe 112. At its forward end, the pipe 112 is connected by a
horizontally extending elbow 114 to a pipe 116 mounted on top of
and in alignment with the heating member 11. At its rear end, the
pipe 116 is connected by a horizontal elbow 118 to another pipe 120
which is mounted on top and of in alignment with the heating member
12. At its forward end, the pipe 116 is connected by way of a
forward elbow 122 to the front end of a fourth horizontally
extending pipe 124 which is mounted on top of and in alignment with
the heating member 13. The rear end of the pipe 124 is connected by
an elbow 126 extending at 45.degree. to the horizontal to the rear
end of the conduit 54.
It will be apparent that by the arrangement shown in FIGS. 4 and 5,
the dwell time of the oil within the tank is increased
considerably. Thus, instead of the oil passing directly between the
rear ends of the two conduits 52 and 54, the oil will pass from the
rear end of the conduit 52 forwardly the length of the tank 14 by
way of the first pipe 112 then rearwardly the same distance by way
of the second pipe 116, then forwardly by way of the third pipe 120
and again rearwardly by way of the fourth pipe 124 to the rear end
of the second conduit 54 through which it flows to the outlet 64 of
the oil conduit system.
In operation, of course, the system shown in FIGS. 3 and 4 is the
same as that shown in FIG. 1 with the exception that the oil flow
within the tank is different and, as mentioned above, the dwell
time of the oil within the tank is increased considerably. It will
be noted that by this arrangement, the temperature of the oil will
be raised a greater amount because of the longer dwell time and the
larger heat exchange area provided. Moreover, since the four pipes
112, 116, 120 and 124 are positioned on top of the tank-heating
members 10-13, as is best shown in FIG. 5, the oil within the pipes
will receive heat almost directly from these tank-heating
members.
The heating system in accordance with the invention has several
advantages over heating systems of the prior art. In the first
place, it permits shorter startup times in the heating of a cold
plant since the heat in the asphalt within the tank supplements the
oil heater capacity. Also, the structural arrangement provides a
convenient location for the oil heater and reduces the cost of
installation of the oil heater since there is no requirement for
insulation. Further, the heating system in accordance with the
invention provides greater safety to the oil-heating means in case
the control means therefor should fail. In this regard, it is noted
that the oil heater will not overheat excessively since the heat
produced thereby is absorbed by the asphalt in the tank.
Another feature of the invention is that the arrangement provided
permits the use of a storage tank in a manner whereby heat energy
may be stored and the system can be operated at a lower cost. The
electrical energy for a bituminous concrete plant, and similar
plants, is usually charged on a demand plus usage basis. The motor
load in such an installation far exceeds the electrical requirement
of the electrical heating elements in the storage tank. Thus, by
operating the electrical heating elements while the plant is not in
operation, there would be no demand charge for the electric heat so
that the electrical energy would be purchased at the most favorable
rate. It will be apparent that the heating system in accordance
with the invention permits the addition of additional heat energy
to the contents of the tank while the plant is not in operation, a
portion of this energy being absorbed into the oil system when the
plant is in operation with a reduction in the amount of electrical
energy required to be used while the plant is in operation.
Moreover, a portion of the extra heat energy in the asphalt when it
is delivered at a temperature higher than required for use, which
is the normal situation, can also be absorbed into the oil
system.
Another feature of the invention is that the tank-heating means and
the oil-heating means are constructed in a single assembly. As
shown in FIGS. 2 and 3 and in FIGS. 4 and 5, the parts of the oil
heater are mounted together with the parts of the tank heater in a
single assembly. For example, in the form of the invention shown in
FIGS. 1 to 3, the front ends of the tank-heating members 10-13 and
the oil heater conduits 58 are secured to the terminal box 20 by
suitable connections and the rear ends of these heating members are
secured together by a support plate 19. In the form of the
invention shown in FIGS. 4 and 5, the oil heater conduit is secured
to the tank-heating members 10-13 by reason of the arrangement
wherein the pipes forming the additional loops are mounted on top
of the various tank-heating members. This assembly can be installed
in the tank by simply welding the plate 15 to the end of the tank
in the position best shown in FIG. 1.
Another feature of the invention is that in view of the very
efficient transfer relationship between the oil conduit means and
the other elements of the assembly, it is possible to utilize a
lower capacity oil heater.
A further feature of the heating system in accordance with the
invention is that there is provided a compact assembly. This, of
course, reduces construction cost.
It will be apparent that various changes may be made in the
construction and arrangement of parts without departing from the
scope of the invention. For example, the invention is applicable to
heating means of types other than electrical heating elements,
although electrical heating elements would achieve the best
results. Also, there may be provided various numbers of
tank-heating members and oil-heating members, the invention not
being limited to the specific arrangement described or to the use
of four tank heaters in combination with two oil heaters.
Accordingly, it is not desired to be limited except as required by
the following claims.
* * * * *