U.S. patent application number 14/033702 was filed with the patent office on 2014-03-27 for apparatus for heating or cooling a meltable material.
This patent application is currently assigned to BASF SE. The applicant listed for this patent is BASF SE. Invention is credited to Ralf BUCH, Waldemar MUENCH, Robert RUPANER.
Application Number | 20140083654 14/033702 |
Document ID | / |
Family ID | 50337730 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140083654 |
Kind Code |
A1 |
BUCH; Ralf ; et al. |
March 27, 2014 |
APPARATUS FOR HEATING OR COOLING A MELTABLE MATERIAL
Abstract
An apparatus for heating or cooling a meltable material in a
container, comprising a heating element (10) and a holding device
(20), the heating element (10) being of a tubular design, with an
inflow opening (11) and an outflow opening (12) for a heat transfer
medium to flow through, and being fastened to the holding device
(20) movably in at least one spatial direction as the main
direction of movement, wherein the apparatus also has a stirrer
(30) for mixing liquid material through, which is likewise arranged
movably in the main direction of movement.
Inventors: |
BUCH; Ralf; (Gruenstadt,
DE) ; MUENCH; Waldemar; (Neustadt, DE) ;
RUPANER; Robert; (Ellerstadt, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BASF SE |
Ludwigshafen |
|
DE |
|
|
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
50337730 |
Appl. No.: |
14/033702 |
Filed: |
September 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61705666 |
Sep 26, 2012 |
|
|
|
Current U.S.
Class: |
165/109.1 |
Current CPC
Class: |
F28F 7/00 20130101; F28D
2021/0045 20130101; F28D 7/024 20130101; B01J 6/005 20130101 |
Class at
Publication: |
165/109.1 |
International
Class: |
F28F 7/00 20060101
F28F007/00 |
Claims
1. An apparatus for heating or cooling a meltable material in a
container, comprising a heating element (10) and a holding device
(20), the heating element (10) being of a tubular design, with an
inflow opening (11) and an outflow opening (12) for a heat transfer
medium to flow through, and being fastened to the holding device
(20) movably in at least one spatial direction as the main
direction of movement, wherein the apparatus also has a stirrer
(30) for mixing liquid material through, which is likewise arranged
movably in the main direction of movement.
2. The apparatus according to claim 1, wherein the holding device
(20) is designed in such a way that the heating element (10) and
the stirrer (30) are movable in the vertical direction as the main
direction of movement through an opening in the upper side of the
container.
3. The apparatus according to claim 1, the heating element (10)
comprising a tube helix (15), which has a hollow-cylindrical
contour, and the axis of the cylinder corresponding substantially
to the main direction of movement.
4. The apparatus according to claim 3, the axial distance between
neighboring tube portions being from 20% to 400%, preferably from
50% to 200%, on the outside diameter of the tube.
5. The apparatus according to claim 3, the tube helix (15)
comprising two part-helixes with the same outside diameter of the
hollow cylinders, the part-helixes running one into the other in
the axial direction, being connected to one another at their
respective one end and opening out into the inflow opening (11) or
the outflow opening (12) with their respective other end.
6. The apparatus according to claim 3, the tube helix (15)
comprising two part-helixes with different outside diameters of the
hollow cylinders, the part-helixes running one into the other in
the radial direction, being connected to one another at their
respective one end and opening out into the inflow opening (11) or
the outflow opening (12) with their respective other end.
7. The apparatus according to claim 3, the heating element (10)
being dimensioned in such a way that the ratio of its length to its
outside diameter is from 1 to 10, preferably from 1.5 to 8, in
particular from 2 to 6, and the outside diameter of the heating
element (10) being from 4 to 60 cm, preferably from 8 to 20 cm, in
particular from 10 to 16 cm.
8. The apparatus according to claim 3, the stirrer (30) comprising
a stirrer shaft (31), on which at least one stirring element (32)
is arranged, and the axis of which corresponds substantially to the
main direction of movement.
9. The apparatus according to claim 8, the stirrer shaft (31) being
arranged inside the hollow-cylindrical tube helix (15).
10. The apparatus according to claim 1, the heating element (10)
and the stirrer (30) being fastened on the holding device (20)
movably in the main direction of movement independently of one
another.
11. A method for melting a meltable material in a container that
has an opening on its upper side, by means of an apparatus
according to claim 1, which comprises the steps of: placing the
lower end of the heating element (10) onto the surface of the
material to be melted through the opening in the container, making
the heat transfer medium flow through the heating element (10),
lowering the heating element (10) into the material as the
liquefaction of the material proceeds, mixing already molten
material through by rotation of the stirrer (30).
12. A method for cooling a molten material in a container that has
an opening on its upper side, by means of an apparatus according to
claim 1, which comprises the steps of: introducing the heating
element (10) into the molten material through the opening in the
container, making a cold heat transfer medium flow through the
heating element (10), after the material has solidified, raising
the temperature of the heat transfer medium briefly to melt the
heating element (10) free, withdrawing the heating element (10)
from the melted-free region.
13. The method according to claim 11, the container being a drum, a
transporting container, a railroad wagon, a container truck or a
road tanker.
Description
[0001] The invention relates to an apparatus for heating or cooling
a meltable material in a container, comprising a heating element
and a holding device, the heating element being of a tubular
design, with an inflow opening and an outflow opening for a heat
transfer medium to flow through, and being fastened to the holding
device movably in at least one spatial direction as the main
direction of movement. The invention also relates to a method for
melting a meltable material and to a method for cooling a molten
material in a container that has an opening on its upper side, by
means of an apparatus according to the invention.
[0002] A number of starting materials for the chemical or other
processing industries, for example waxes, wax-like oligomers and
polymers, fats, emulsifiers or salts, are in a solid or highly
viscous state at ambient temperature (20.degree. C. to 25.degree.
C.) and must be liquefied before they undergo further processing.
The provision of considerable amounts of such materials involves a
certain degree of expenditure. Such materials are usually
transported and delivered in transporting containers such as drums
or, for example, "Intermediate Bulk Containers" (IBC), which,
depending on the type, generally have a capacity of 500 to 1000
liters. The containers have a filling opening of about 15 cm in
diameter on their upper side and a drainage tap underneath.
[0003] Since the starting materials often constitute a mixture, it
is generally required to melt and homogenize the complete content
of a transporting container before a homogeneous partial amount can
be removed from the transporting container and passed on for
further processing, since it can be assumed that, during the
preceding solidification process, the components have crystallized
out at varying rates, and therefore the mixture in the container is
not in a homogeneously distributed form.
[0004] The liquefying of the content of a transporting container is
often carried out in what are known as heating cabinets, the
container being placed in a closed, heated space in which it is
heated as a whole by the air surrounding it. In the case of a
further established method for melting the content of the
container, the container is immersed in a tank with hot water and
left there until the content of the container has melted. Both the
heating cabinet and the immersion tank involve complicated
structural measures and a high energy consumption. Also known are
electrically operated heating bands and heating jackets, which are
placed around the outer wall of the transporting container and
transfer heat to the container wall. They are also not very
energy-efficient.
[0005] A further disadvantage of the aforementioned methods can be
seen in the fact that the heat transfer takes place indirectly via
the container wall. Generally used as the material for the walls of
IBCs is, for example, polyethylene (HDPE), which has a low thermal
conductivity and a thermal resistance of approximately 100.degree.
C. Consequently, there are limits to the heating-up process with
regard to the maximum admissible temperature, in order to avoid
damage or even destruction of the container wall. Furthermore, with
wall heating, the layers of the solid material that are near the
wall melt first, so that in the course of the melting process
layers of gas form between the solid material and the inner wall of
the container, reducing the thermal conductivity still further.
[0006] Specifically for drums as transporting containers, there are
known apparatuses in which heating does not take place indirectly
via the drum wall, but in direct contact with the material to be
melted. In laid-open patent specification DE 37 06 927 A1 there is
a description of a drum melting apparatus which comprises a
horizontally arranged tube spiral through which hot steam is made
to flow. The tube spiral is placed onto the material to be melted
and, as the melting process proceeds, slides down in a mounting in
the drum under the influence of gravitational force.
[0007] The document RU 2 159 671 C1 discloses a similar apparatus,
which is likewise intended for liquefying solid, meltable contents
of drums. Also in the case of this apparatus, a horizontally
arranged tube spiral is placed onto the material to be melted and
slides down in the drum as the melting process proceeds. The tube
spiral is flowed through by a liquid heating medium, the
temperature of which can be set.
[0008] While the two aforementioned apparatuses are suitable for
liquefying the content of drums, they are only suitable to a
limited extent for melting material in a container such as an IBC.
This is so because, by contrast with drums, in which the cross
section of the opening is of the same order of magnitude as the
cross section of the drum, the openings of containers are usually
much smaller than the cross section of the container. Although it
is possible with the known apparatuses to melt vertical channels
into the material in a container, it takes a very long time before
the entire material is liquefied, if it is possible at all.
[0009] The object is to provide an apparatus with which solid or
highly viscous materials in transporting containers can be
liquefied homogeneously and energy-efficiently in a short time.
[0010] This object is achieved according to the invention by an
apparatus for heating a meltable material in a container,
comprising a heating element and a holding device, the heating
element being of a tubular design, with an inflow opening and an
outflow opening for a heat transfer medium to flow through, and
being fastened to the holding device movably in at least one
spatial direction as the main direction of movement, the apparatus
also having a stirrer for mixing liquid material through, which is
likewise arranged movably in the main direction of movement. As
described further below, the apparatus according to the invention
can also be used for cooling a meltable material in a
container.
[0011] The apparatus may also be designed to be movable in two or
all three spatial directions. The main direction of movement is
understood as meaning the direction in which the heating element
and the stirrer can be moved into the container and out of the
container. In a preferred embodiment, the holding device is
designed in such a way that the heating element and the stirrer are
movable in the vertical direction as the main direction of movement
through an opening in the upper side of the container.
[0012] The heating element according to the invention is tubular
and can be flowed through by a fluid heat transfer medium. The
cross section of the tube may have different forms; it is
preferably circular, oval or rectangular, in particular circular.
The heating element is preferably produced from a material which
has a high heat transfer coefficient. It is particularly preferred
for the heating element to be produced from high-grade steel,
aluminum or copper. The wall thickness is preferably from 1 to 2
mm, the inside diameter from 0.5 to 3 cm.
[0013] In the case of a particularly advantageous embodiment, the
heating element comprises a tube helix, which has a
hollow-cylindrical contour. This configuration offers a large heat
transfer area in a limited space. It is also preferred that the
cylinder axis corresponds substantially to the main direction of
movement. This has the advantage that, with a given cross section
of the container opening, the outside diameter of the tube helix
can be chosen to be as large as possible, without the opening being
skewed when the heating element is moved in and out. A deviation of
up to 10.degree. between the hollow cylinder axis and the main
direction of movement is considered to be still tolerable.
[0014] In order to ensure a liquid flow through the hollow cylinder
not only in the axial direction but also in the radial direction, a
distance between the tube portions of the helix in the axial
direction is preferably provided. The axial distance between
neighboring tube portions is preferably from 20% to 400%,
particularly preferably from 50% to 200%, of the outside diameter
of the tube.
[0015] In the case of a preferred configuration, the tube helix
comprises two part-helixes with the same outside diameters of the
hollow cylinders, the part-helixes running one into the other in
the axial direction, being connected to one another at their
respective one end and opening out into the inflow opening or the
outflow opening with their respective other end. Also in the case
of this embodiment, axially neighboring tube portions are
preferably kept at a distance. In a further preferred variant, the
part-helixes are arranged in such a way that the axial distance
between neighboring tube portions is alternately 0% and from 50% to
400%, particularly preferably from 100% to 300%, of the outside
diameter of the tube. This means that on one axial area the
part-helixes are touching, while the other areas are at an axial
distance in the range specified.
[0016] In the case of a further preferred configuration, the tube
helix comprises two part-helixes with different outside diameters
of the hollow cylinders, the part-helixes running one into the
other in the radial direction, being connected to one another at
their respective one end and opening out into the inflow opening or
the outflow opening with their respective other end.
[0017] Both configurational variants are also referred to hereafter
as double helixes. The inflow opening and the outflow opening are
preferably located on the end face of the hollow cylinder that is
facing away from the container during moving in and out.
[0018] The heating element is preferably dimensioned in such a way
that the ratio of its length to its outside diameter is from 1 to
10, particularly preferably from 1.5 to 8, in particular from 2 to
6. The outside diameter of the heating element is preferably from 4
to 60 cm, particularly preferably from 8 to 20 cm, in particular
from 10 to 16 cm. A length of 60 cm to 120 cm has proven to be
advantageous for a number of applications.
[0019] In a preferred embodiment of the apparatus according to the
invention, the stirrer comprises a stirrer shaft, on which at least
one stirring element is arranged, and the axis of which corresponds
substantially to the main direction of movement. In the case of
embodiments with a hollow-cylindrical heating element, the stirrer
shaft is preferably arranged inside the hollow-cylindrical tube
helix, particularly preferably coaxially in relation to the
cylinder axis.
[0020] The stirrer shaft may be driven by known motors and gear
mechanisms, for example electrically or pneumatically. The axial
and vertical flow conditions in and around the heating element can
be set by the choice of stirring elements. Appropriate stirring
elements, for example blade, disk, cross-arm, impeller, anchor or
propeller stirrers, are known to a person skilled in the art. The
stirring elements are preferably made from high-grade steel;
depending on the application, enamelled or, for example,
Teflon-coated stirring elements have also proven to be successful
in counteracting product attachment. The stirring elements are
preferably fastened to the stirrer shaft adjustably and/or
exchangeably.
[0021] In a preferred embodiment, the stirrer is arranged in such a
way that it can be moved together with the heating element in the
main direction of movement. In this case, for example, components
in which the stirrer is mounted may be fixedly connected to the
heating element or the holding device.
[0022] In a further preferred embodiment, the heating element and
the stirrer are arranged movably in the main direction of movement
independently of one another. In this case, components in which the
stirrer is mounted may be connected to the heating element in such
a way that the stirrer is movable in relation to the heating
element in the main direction of movement. However, the stirrer is
preferably fastened to the holding device movably in the main
direction of movement. Particularly preferred is an arrangement of
the heating element and the stirrer in which the stirrer moves
further into the container than the heating element. This makes it
possible, for example, to use a stirring element which spreads open
speed-dependently and, in the spread-open state, has a greater
diameter than the outside diameter of the heating element.
[0023] The apparatus according to the invention may be provided
with a sensor or a plurality of sensors, for example for sensing
the temperature, the viscosity or the conductivity of the liquefied
material or the torque of the stirrer shaft. Changes in the
properties of the melt, such as the viscosity, can be concluded
from a change in the speed of the stirrer or the torque thereof
during operation.
[0024] A further subject matter of the invention is a method for
melting a meltable material in a container that has an opening on
its upper side, by means of the apparatus according to the
invention, comprising the following steps: [0025] placing the lower
end of the heating element onto the surface of the material to be
melted through the opening in the container, [0026] making the heat
transfer medium flow through the heating element, [0027] lowering
the heating element into the material as the liquefaction of the
material proceeds, [0028] mixing already molten material through by
rotation of the stirrer.
[0029] Making the heat transfer medium flow through the heating
medium does not necessarily have to be carried out as the second
step, it may also be commenced already before the heating element
is placed onto the surface of the material to be melted. The
through-flow may take place continuously during the melting process
or intermittently. The steps of lowering the heating element and
performing mixing through by the rotation of the stirrer may be
carried out successively or at the same time as one another. They
may also be carried out alternately one after the other.
[0030] The heat transfer medium is chosen in dependence on the
melting range of the material to be melted. For a wide application
area, warm to hot water with flow temperatures of 60 to 90.degree.
C. are suitable. If the melting range of the material to be melted
requires a higher flow temperature, superheated water or
water-steam mixtures up to a temperature of about 160.degree. C.
under a pressure of 4 bar are suitable. For still higher
temperatures, heating by steam alone is recommendable, in the
last-mentioned cases the components of the heating element having
to be of a pressure-resistant configuration. It goes without saying
that, depending on availability and the specific application, other
heat transfer media may also be used, for example oils such as
Marlotherm oil. They should be used in particular whenever water is
not appropriate for safety reasons, for example if the container
content would react violently with water in the event of a
leakage.
[0031] A further subject matter of the invention is a method for
cooling a molten material in a container that has an opening on its
upper side, by means of the apparatus according to the invention,
comprising the following steps: [0032] introducing the heating
element into the molten material through the opening in the
container, [0033] making a cold heat transfer medium flow through
the heating element, [0034] after the material has solidified,
raising the temperature of the heat transfer medium briefly to melt
the heating element free, [0035] withdrawing the heating element
from the melted-free region.
[0036] Making the cold heat transfer medium flow through the
heating medium does not necessarily have to be carried out as the
second step, it may also be commenced already before the heating
element is introduced into the molten material. The through-flow
may take place continuously during the melting process or
intermittently.
[0037] The cold heat transfer medium is chosen in dependence on the
melting temperature of the material to be cooled. Suitable are, for
example, cold water, cooling water, brine or some other substance
if water cannot be considered for the safety reasons already
referred to above.
[0038] By immersing the heating element in the molten material, the
latter can be cooled quickly and efficiently and, depending on its
melting point, possibly made to solidify. In the case of a
solidified material, a warm or hot heat transfer medium may be
briefly made to flow through the heating element, so that the
material in its direct vicinity liquefies. Subsequently, the
melted-free heating element is removed from the container and
possibly left to drip. The method for cooling a molten material is
advantageously used when an end product is to be rapidly cooled or
solidified, for example in order to make it quickly ready for
transportation or to prevent crystallization of the material.
[0039] Furthermore, it can also be used for rapidly cooling liquids
from the food industry, which may occur in a warm state or else be
heated briefly for the purpose of sterilization, for example wine,
milk or fruit juices.
[0040] In an advantageous configuration of the method according to
the invention, the flow temperature to the heating element is set
to a predetermined temperature. Appropriate thermostats or
temperature control devices are known to a person skilled in the
art.
[0041] To protect against undesired reactions in the container, for
example oxidations with atmospheric oxygen, a shielding gas may be
introduced into the container while the method is being carried
out. This gas is preferably nitrogen.
[0042] The method according to the invention is suitable in
particular for melting and/or cooling [0043] solid hydrocarbons or
derivatives thereof, for example waxes and paraffins, [0044]
polyether glycols, derived from polyethylene, polypropylene or
polybutylene glycols or mixtures thereof, which may also be in an
alkylated form, [0045] fats or solid fat-water emulsions, [0046]
solid salts, ionic liquids, metals or alloys, [0047] solid mono-,
di- or polyisocyanates, low-molecular-weight prepolymers or
silicones, [0048] solid sulfur or organic anhydrides such as maleic
anhydride or phthalic anhydride.
[0049] The methods according to the invention are suitable for
various transporting containers, in particular for drums, shipping
containers, railroad wagons, container trucks and road tankers.
Depending on the specific application, a plurality of apparatuses
according to the invention may also be used.
[0050] The invention makes it possible for the content of a
transporting container to be gently melted and heated by the direct
contact of a heated heating element with the material to be melted
in the container. By creating a flow in a melt by stirring while
the heat is being introduced into the melt, the container content
is additionally mixed through homogeneously, and the duration of
the melting process is reduced considerably in comparison with
known methods. As a result, potentially harmful side-effects of the
melting process, such as thermal damage to the material or
undesired reactions in the container, are also significantly
minimized. The apparatus according to the invention is of a simple
structure and can be used flexibly.
[0051] The invention is further explained below on the basis of the
drawings, which should be understood as basic representations. They
do not represent any restriction of the invention, for example with
regard to actual dimensions or configurational variants of
components. For the sake of better representation, they are
generally not to scale, in particular with regard to relative
lengths and widths. In the drawings:
[0052] FIG. 1 shows an embodiment of an apparatus according to the
invention with a double helix as a heating element
[0053] FIG. 2 shows a detail taken from FIG. 1
[0054] FIG. 3 shows an example of use of an apparatus according to
the invention for the continuous melting of solid flakes
[0055] FIG. 4 shows an embodiment of an apparatus according to the
invention for use in drums
LIST OF REFERENCE NUMERALS USED
[0056] 10 . . . Heating element [0057] 11 . . . Inflow opening
[0058] 12 . . . Outflow opening [0059] 13 . . . Inflow line [0060]
14 . . . Outflow line [0061] 15 . . . Tube helix [0062] 16 . . .
Reinforcing element [0063] 20 . . . Holding device [0064] 21 . . .
Guiding rod [0065] 22 . . . Guiding sleeve [0066] 23 . . . End stop
[0067] 30 . . . Stirrer [0068] 31 . . . Stirrer shaft [0069] 32 . .
. Stirring element [0070] 33 . . . Motor [0071] 40 . . . Container
[0072] 41 . . . Insulated container wall [0073] 42 . . . Wire
screen [0074] 43 . . . Filling hopper [0075] 44 . . . Outlet for
melt [0076] 45 . . . Solid flakes [0077] 46 . . . Melt [0078] 47 .
. . Gas inlet
[0079] In FIG. 1, a preferred embodiment of an apparatus according
to the invention is represented. The heating element 10 is formed
in a tubular manner as a double helix 15, which has a
hollow-cylindrical contour. The two part-helixes have the same
outside diameter of the hollow cylinder and run one into the other
in the axial direction. The axial distance between neighboring tube
portions is alternately 0% and 200% of the tube outside diameter,
that is to say on one axial area the part-helixes are touching,
while the other areas are at an axial distance that corresponds to
twice the tube outside diameter. At their respective one end, in
FIG. 1 the lower end, the part-helixes are connected to one
another. With their respective other end, the part-helixes open out
into the inflow opening 11 or into the outflow opening 12. The
inflow opening 11 and the outflow opening 12 are located on the end
face of the hollow cylinder that is facing away from the container
during moving in and out. For a heat transfer medium to flow
through, the two openings are connected to an inflow line 13 and an
outflow line 14. To strengthen the hollow cylindrical structure
with respect to radial bending, in the example represented three
band-shaped reinforcing elements 16 are provided, running axially
on the outer side of the double helix and fixedly connected, for
example welded or brazed, to at least some tube portions.
[0080] The holding device 20 comprises two guiding rods 21, on
which a guiding sleeve 22 is slidingly mounted. In order to prevent
the guiding rods 21 from sliding out of the guiding sleeve 22, they
are respectively provided at their lower ends with an end stop 23.
The end stop 23 can preferably be set variably along the guiding
rods 21, in order to be able to limit the depth of immersion of the
heating element 10 in a container. The guiding sleeve 22 is
connected to the inflow tube and the outflow tube of the double
helix 15.
[0081] The holding device 20 may be fixed in place, for example on
a wall, a top surface or a freestanding framework, or it may be
used in a mobile manner, for example with its lower end mounted on
a transporting container. In the case of an advantageous
configuration with a fixed-in-place mounting, the holding device is
fixedly connected to a wall. The transporting container to be
handled is placed under the holding device. The heating element and
the stirrer can be placed onto the material to be melted by being
moved on the holding device in the main direction of movement
vertically downward through the opening in the upper side of the
transporting container. The heating element and the stirrer are
preferably moved by means of a manually or electrically operated
cable winch.
[0082] In the space inside the hollow-cylindrical double helix 15,
a stirrer 30 is coaxially arranged. It comprises a stirrer shaft 31
and, in this example, three stirring elements 32 fastened thereto.
FIG. 2 shows the lower end of the apparatus from FIG. 1 as a
detail. The stirrer shaft 31 and the stirring elements 32 fastened
thereto can be seen more clearly from this illustration. Not shown
in the illustrations is the mounting of the stirrer shaft 31. It
may take place independently of the mounting of the heating
element, in order to allow an axial relative movement between
heating element 10 and the stirrer 30. The axial relative movement
makes it possible to move the stirrer further into the container
than the heating element. This makes it possible, for example, to
use a stirring element which spreads open speed-dependently and, in
the spread-open state, has a greater diameter than the outside
diameter of the heating element.
[0083] In order to liquefy the content of a transporting container,
for example an IBC, the apparatus according to FIG. 1 is placed
with its holding device 20 onto the opening in the upper side of
the container. The heating element 10 is placed onto the solid
content of the container and put into operation, by making warm or
hot heat transfer medium, for example hot water, flow through it.
The material in the direct vicinity of the tube helix 15 begins to
melt, whereupon the heating element 10 is immersed in the melt on
account of its dead weight or by being guided downward. The stirrer
30 inside the heating element 10 is likewise immersed in the melt
being created. As soon as one or more of the stirring elements 32
is in the melt, the stirrer is switched on. The flow induced in the
melt as a result has the effect that the heat transfer between the
heat transfer medium and the material to be melted is improved
significantly. Moreover, the melt is in this way homogenized. After
some time, the container content is completely melted and
homogeneously mixed. The stirrer 30 is switched off, the heating
element 20 is removed from the container and left to drip. Then a
desired amount of liquid, homogeneously mixed material can be
removed from the transporting container.
[0084] Experience shows that only a small part of the energy
introduced by the heat transfer medium is required for melting the
solid material. It is therefore also possible to connect a
plurality of apparatuses in series or parallel and operate them
energy- and cost-efficiently. It is also advantageously possible to
provide a control system which optimizes the melting process, by
increasing the energy input whenever there is sufficient melt to
take up the thermal energy. A preferred control strategy envisages,
for example, initially melting the material with a low energy
input, until the heating elements have been lowered to a
predetermined length, and subsequently increasing the temperature
of the heat transfer medium and/or the through-flow of heat
transfer medium.
[0085] In a preferred configuration, three to five apparatuses
according to the invention are interconnected on the heat transfer
medium side, the heat transfer medium is pumped in a circulated
manner and the energy required for input into the melt is
introduced continuously into the circulation, for example by a heat
exchanger or an inflow of heat transfer medium at a higher
temperature than that in the circulating flow. Hot condensate from
a processing plant can be advantageously used for this, for
example.
[0086] Apart from the discontinuous use for liquefying solid
container contents, the apparatus according to the invention can
also be used continuously. FIG. 3 shows an example of the use of an
apparatus according to the invention in a continuous process for
melting solid flakes. Shown as a basic diagram is a longitudinal
section through a container 40, which comprises an upper
cylindrical part and a conical part adjoining said cylindrical part
in the downward direction. The container wall 41 is preferably of a
heat-insulated configuration. In the top of the container there is
a filling hopper 43 for solid flakes 45, which is equipped with a
closure flap for the metering of the flakes. At the lower end of
the conical part there is an outlet 44 for the melt 46. Provided at
the transition from the cylindrical part to the conical part is a
wire screen 42, the mesh width of which is dimensioned in such a
way that only the melt can flow into the conical part, and any
flakes that there may still be in the melt are held back.
[0087] In a further opening in the top, the holding device 20 of an
apparatus according to the invention is fastened. Its construction
corresponds substantially to that represented in FIG. 1. Only the
holding device 20 has been modified. The inflow tube and the
outflow tube are each fastened to a guiding rod. The two guiding
rods are slidingly mounted in two sleeves, which are connected
fixed-in-place to the top of the container by means of the holding
device 20. The length and position of the elements of the holding
device have been chosen such that the lower end of the apparatus in
the completely lowered state is just above the wire screen 42.
[0088] The method for continuously melting solid flakes may, for
example, proceed as follows: firstly, flakes 45 are fed a little at
a time into the interior of the container, until they have reached
such a height from the wire screen 42 that they come into contact
with the heating element 10. The heating element 10 is put into
operation and hot water is made to flow through as a heat transfer
medium. The melt 46 collects in the lower, conical part of the
container, while flakes continue to be fed in continuously through
the filling hopper 43. As soon as about half of the container is
filled with melt, a continuous melt discharge through the outlet 44
is begun. While the flakes are being supplied, nitrogen is added as
a shielding gas via a gas inlet 47.
[0089] This melting method can be advantageously used to supply a
downstream plant continuously with a molten starting material, for
example one of the substances mentioned above. For a polyethylene
glycol (PEG 6000, melting range about 45.degree. C. to 60.degree.
C.), for example, a heating element with a ratio of length to
outside diameter of 1.5 is suitable if it is operated with hot
water at about 80.degree. C. For protection from an oxidation
reaction, nitrogen is fed to the container at a volumetric flow of
80 liters per minute.
EXAMPLES
[0090] In Examples 1 to 4 described below, an embodiment of the
apparatus according to the invention that corresponded in principle
to the one represented in FIG. 1 was used. The heating element was
produced from a high-grade steel tube with a wall thickness of 1.5
mm and an inside diameter of 9 mm. The heating element comprised a
double helix with an outside diameter of the hollow cylinder of
13.5 cm and a length of the double helix of 72 cm. The axial
distance between neighboring tube portions was 200% of the outside
diameter of the tube. The stirrer was pneumatically driven and
speed-controlled. Three propeller stirrers were arranged at a
respective distance of 20 cm on the stirrer shaft as stirring
elements. The outside diameters of the propeller stirrers were
about 8 cm.
Example 1
[0091] An IBC was filled with 750 kg of n-octadecane (melting point
20.degree. C.). The mass was in the container in the form of a
block of homogeneous solid material. The IBC was open at the top,
and the lower end of the holding device of the apparatus according
to the invention was placed onto the rim of the opening. The
heating element was movable in the vertical direction and was
placed with its lower end onto the mass of solid material. To heat
the solid material, hot water was made to flow through the heating
element as a heat transfer medium. The water was gravimetrically
fed into the heating element from a condensate tank at a flow
temperature of about 80.degree. C. and a volumetric flow of about 5
l/min. The water emerging from the outlet of the heating element
was discarded. After approximately 60 minutes, the heating element
had melted its way into the solid material over the complete length
of the tube helix, whereupon the stirrer was switched on at a
rotational speed of about 200 rpm. After a total of 12 hours, the
entire content of the container was melted and homogeneously mixed
through.
[0092] The heating element was withdrawn from the IBC and left to
drip. After two minutes, it was sufficiently clean to be placed
onto the next container. In the interim, a heatable feed pump and a
trace-heated line were connected to the bottom tap of the IBC and
the container was pumped empty for the material to be put to
further use.
Comparative Example 1
[0093] An IBC comparable to Example 1 was introduced into a heating
cabinet (the Conthermo company, heating area of 50 m.sup.2,
steam-heated at 4 bar) with a heated spatial volume of 2.3 m.sup.3
and a set ambient temperature of 70.degree. C., and the top of the
IBC was loosened sufficiently for pressure equalization. The
melting process was visually checked every two hours to monitor its
progress. Only after 63 hours in the heating cabinet was it found
that the content had melted completely. The container was removed
from the heating cabinet and its content processed further.
Example 2
[0094] The test arrangement corresponded to that in FIG. 1, with
the difference that the IBC was filled with 750 kg of the wax
mixture LINPAR.RTM. 18-20 (supplied by the Sasol company). The wax
mixture consists mainly of n-alkanes of a chain length of C17 to
C19 and has a melting point of about 30.degree. C. After about 15
minutes, the tube helix had melted into the wax mixture over its
entire length, whereupon the stirrer was switched on. After a total
of six and a half hours, the total content of the container had
melted, and a partial amount of 145 kg was removed.
Comparative Example 2
[0095] Under the same conditions as in Comparative example 1, a wax
mixture LINPAR.RTM. 18-20 in an IBC was placed into a heating
cabinet. After 33 hours, the mixture had melted completely, and the
IBC was removed from the heating cabinet. With an inserted stirrer,
the content of the IBC was homogenized for a time of 10 minutes,
before a partial amount of 145 kg of the wax mixture could be
removed.
Example 3
[0096] The test arrangement corresponded to that in Example 1, with
the difference that the IBC was filled with 750 kg of a mixture of
saturated n-paraffinic hydrocarbons (melting range about 27.degree.
C. to 31.degree. C.). After about 30 minutes, the tube helix had
melted into the mixture over its entire length, whereupon the
stirrer was switched on. The entire melting process of the complete
IBC content took 8 hours. After the melting, a partial amount could
be removed from the IBC.
Comparative Example 3a
[0097] Under the same conditions as in Comparative example 1, a
mixture according to Example 3 in an IBC was placed into a heating
cabinet. After 37 hours, the mixture had melted completely, and the
IBC was removed from the heating cabinet. With a stirrer placed on,
the content of the IBC was homogenized for a time of 30 minutes,
before a partial amount of the mixture could be removed.
Comparative Example 3b
[0098] A commercially available, electrically operated heating band
was wound around an IBC according to Example 3 and used to heat it.
After heating for a week, the content had still not melted and the
test was abandoned.
Example 4
[0099] A clamping ring drum with a capacity of 200 liters was
filled with 210 kg of a solid emulsifier (melting point about
26.degree. C.). The main constituent of the emulsifier was
p-octylphenol ethoxylate with about 25 mol EO. The mass was in the
drum in the form of a block of homogeneous solid material. The lid
of the drum was removed, and the lower end of the holding device of
the apparatus according to the invention was placed onto the rim of
the opening. All further method steps corresponded to those
described in Example 1, water with a flow temperature of 67.degree.
C. being used as a heat transfer medium. The stirrer was switched
on about one hour after the beginning of the melting process. After
14 hours, the entire content of the drum had melted, and, to dilute
it, the melt could be pumped into a reaction vessel already
containing hot water.
Comparative Example 4a
[0100] Under the same conditions as in Comparative example 1, a
drum with emulsifier according to Example 4 was placed into a
heating cabinet. After 67 hours, the content of the drum had melted
completely.
Comparative Example 4b
[0101] Four pallets each with four sealed drums according to
Example 4 were introduced and completely immersed in a tank with
dimensions of 4.times.3.times.2 meters
(length.times.width.times.depth), which was filled with 15 m.sup.3
of water. A constant stream of steam was introduced into the tank
for two days, whereby the water heated up and the content of the
drums was heated continuously. Experience shows that, after keeping
them in the tank for two days, the content of the drums was melted
through completely. This conventional method is complicated and
very energy-intensive. Moreover, sampling or monitoring of the
melting process is only possible if a complete pallet is extracted.
It has also proven to be disadvantageous that treatment of this
kind very soon makes the drums begin to rust.
Example 5
[0102] In the two examples described below, an embodiment of the
apparatus according to the invention that corresponded in principle
to the one represented in FIG. 4 was used. The heating element 10
was produced from a high-grade steel tube with a wall thickness of
1.5 mm and an inside diameter of 9 mm. The heating element
comprised a single tube helix 15 with an outside diameter of the
hollow cylinder of 40 cm and a length of the tube helix of 60 cm.
The axial distance between neighboring tube portions was 100% of
the outside diameter of the tube. The upper end of the tube helix
15 opened out into the inflow opening 11. The lower end of the tube
helix 15 was guided upward as a straight piece of tube on the inner
side of the hollow cylinder and opened out into the outflow opening
12. To strengthen the hollow cylindrical structure with respect to
radial bending, four band-shaped reinforcing elements 16 were
provided, running axially on the outer side of the double helix and
fixedly connected to at least some tube portions.
[0103] The heating element was designed with a view to melting
material in drums. The diameter of the hollow cylinder was chosen
such that, when seen in cross section perpendicularly to the axis
of the hollow cylinder, the area content of the circle within the
hollow cylinder corresponds substantially to the area content of
the circular ring between the hollow cylinder and the inner wall of
the drum. The test results presented below were obtained with the
heating element without using a stirrer. In comparison with
conventional methods for melting the material in the drums, it was
possible to achieve much shorter times just with the heating
element alone. When a stirrer is used, further reduced times can be
expected for the melting process as a result of the better mixing
through.
Example 5a
[0104] The apparatus according to the invention was placed into an
empty clamping ring drum with a capacity of 200 liters and the
heating element as described in Example 1 was put into operation.
100 kg of maleic anhydride flakes (melting point 53.degree. C.)
were fed into the drum and melted while venting. The melting
process for the entire amount of 100 kg took one hour.
Example 5b
[0105] The apparatus according to the invention was placed into an
empty clamping ring drum with a capacity of 200 liters and 100 kg
of polyethylene glykol 6000 (melting range about 45.degree. C. to
60.degree. C.) was introduced in the form of flakes. With hot water
at a temperature of about 90.degree. C. as a heat transfer medium,
the heating element was then put into operation. After six hours,
the complete content of the drum had melted, so that the melt could
be pumped into a storage tank.
[0106] For the next melting process, 100 kg of flakes (four bags of
25 kg each) were again introduced into the clamping ring drum.
Comparative Example 5b
[0107] The clamping ring drum filled with flakes was placed in a
heating chamber, the inside ambient temperature of which had been
set to 90.degree. C. After 19 hours, the content of the drum had
melted completely and could be removed for further use.
[0108] Most of the tests described above were carried out in
winter. The temperature of the material to be melted before the
beginning of the melting process was not determined. However, it
was the same in the examples and associated comparative examples,
since the transporting containers and drums were kept outdoors or
in unheated sheds at the same location.
[0109] Examples 6 and 7 illustrate the possibilities for using the
apparatus according to the invention for cooling meltable material.
They have not yet been confirmed experimentally.
Example 6
[0110] A catalyzed solvent-free conversion of a mixture of two
different bifunctional isocyanates with a mixture of two diols and
a triol is carried out at 110.degree. C. in a reaction vessel with
a reaction volume of 10 m.sup.3 to obtain a viscous polyurethane
melt. The size of the batch is around six tonnes. After completion
of the conversion, the reaction product has to be fed into seven
prepared IBCs, while the cooling process is intended to be carried
out quickly and under supervision, since the reaction product
continues to react as the viscosity increases at the temperature
concerned here. For being filled, the IBCs stand next to one
another and each IBC is equipped with an apparatus according to the
invention as described above, which are respectively introduced
into the empty IBCs. The apparatuses are connected in series to a
common cooling circuit and serve for cooling the reaction product.
Each of the stirrers is equipped with a stirrer speed monitor. The
heating elements are interconnected on the countercurrent
principle, opposite to the filling sequence of the IBCs. This has
the consequence that the IBC to be filled at any one time comes
into contact with the coldest stream of coolant.
[0111] As the temperature of the reaction product in the reaction
vessel decreases, the viscosity of the mixture increases greatly.
It is therefore not expedient to cool the reaction product in the
reaction vessel completely. After complete conversion, the mixture
is merely cooled to an internal temperature of about 75.degree. C.
and introduced by means of heated lines from the reaction vessel
into the IBCs via their bottom tap by further pressurization by
means of nitrogen. Once the filling of one IBC has been completed,
the lines are blown free by means of a surge of nitrogen and the
bottom tap concerned is closed.
[0112] On the apparatuses, the stirrer shaft has been lowered
approximately 10 cm with respect to the lower end of the tube helix
and is immersed in the product before the helix. When the surface
of the melt rises and comes into contact with the tube helix, slow
cooling commences, but only has an effect when the container is
completely filled and no further hot product flows in. The
temperature of the product is lowered while at the same time its
own viscosity increases, until the increasing viscosity leads to a
reduction in the stirrer speed. If the speed drops below a
predetermined, product-dependent value, the respective apparatus is
withdrawn from the melt of the IBC. After a cooling time of
approximately 3 h, the temperature inside the IBCs has fallen to
approximately 45.degree. C. Once all the IBCs have been filled and
the apparatuses have been withdrawn from the IBCs, the cooling is
stopped and hot water is passed through the tube helix in order to
liquefy any remains of product that are attached and make them drop
into the IBCs. After that, the IBCs are closed for
transportation.
Example 7
[0113] To prepare a defined wax mixture comprising 2 parts
n-octadecane, 1 part n-eicosane (C.sub.20H.sub.42, melting range
36-39.degree. C.) and 1 part n-docosane (C.sub.22H.sub.46, melting
range 41-44.degree. C.), the contents of four separate IBCs with
the raw materials analogous to Example 1 are melted and
successively pumped into a dry stirred reaction vessel that has
been filled with nitrogen and preheated to 60.degree. C. and are
homogenized for a time of 30 minutes. The apparatuses according to
the invention are switched over to cooling and brine heated to
+10.degree. C. is made to flow through them. The liquid wax mixture
is forced back out of the stirring vessel into the IBCs, whereby
the IBCs are filled. When the liquid wax melt comes into contact
with the cool tube helixes, the mass solidifies quickly and grows
outward around the tube helix. The cooling is maintained until the
entire content of the IBCs is completely solidified and in the form
of a block, which is the case after about 6 hours. The temperature
of the heat transfer medium is then increased to 43.degree. C. for
a time of three minutes, in order that the material surrounding the
tube helix can liquefy and the apparatuses can be withdrawn from
the IBCs. In comparison with the conventional method, in which the
container content is not actively cooled but solidifies slowly, a
more homogeneous distribution of the container content is achieved
by the method according to the invention. To verify this, drilled
samples can be taken at various points in the IBC and analyzed for
their physical properties, such as the melting temperature.
* * * * *