TECHNICAL FIELD
[0001] The present invention relates to elevating the temperature of highly viscous fluids
by a movable heating element. The invention further relates to elevating the temperature
of a highly viscous slurry of a hydrocarbon fluid in which an amount of water stabilizes
the suspension of particles of solid carbonaceous material at a high pressure by rotating
a heating element within the slurry to break up laminar flow of the slurry over the
heating element.
BACKGROUND ART
[0002] In the present stage of prior art development, fuels are being developed in the form
of slurries of fluid hydrocarbons in which solid carbonaceous material is dispersed.
In short, coal, or petroleum coke, is being dispersed in oil, the coal, or petroleum
coke, being so finely dispersed that the re- sultin
g slurry can be atomized from burners at pressures in the order of 500 psi.
[0003] The fuel slurry, as a highly viscous fluid, must be brought to pre-burner temperature
quickly. The fluid must arrive at the burner within a fairly high pressure range.
The conventional concept of passing this fluid material through a tube-shell heat
exchanger must be discarded, as the coefficient of heat exchange and pressure drop
through such heating device has been found unsatisfactory. An arrrangement is sought
which will elevate the coefficient of heat transfer, yet preclude the penalty of excessive
pressure drop in the flow stream.
[0004] To elevate the coefficient of heat transfer between the heating element and the fluid
being heated, movement of the heating element must be provided to break up laminar
flow within the fluid. Further, the surface of the heating element must be given a
configuration which will not only agitate the fluid, but extend, or expand, the effective
heat transfer surface of the heating element. One of the overall specifications for
this new configuration is obviating accumulation of solid deposits on all surfaces
coming in contact with the fluid being heated, and the introduction of excessive pressure
drop in the flow stream of the fluid.
DISCLOSURE OF THE INVENTION
[0005] The present invention contemplates the provision of a casing through which a fluid
to be heated is passed. Mounted within the casing is a heated chamber over whose outer
surface the fluid being heated passes. The heating chamber within-the casing is moved
to reduce laminar flow of the fluid passing over its outer surface in elevation of
the coefficient of heat exchange between the surface and the fluid. Surface extenders
are mounted on the external surface of the heating chamber with the result that movement
of the heating element will cause the extenders to increase the reduction of laminar
flow while expanding'the effective heating transfer surface of the chamber.
[0006] Other objects, advantages and features of this invention will become apparent to
one skilled in the art upon consideration of the written specification, appended claims,
and attached drawings.
BRIEF DESIGNATION OF THE DRAWING
[0007] The drawing is a sectioned elevation of the heater for a highly viscous fluid in
which the present invention is embodied. BEST MODE FOR CARRYING OUT THE INVENTION
Overview
[0008] The basic objective of the structure in which the invention is_embodied is to elevate
the temperature of a fluid, or fluid-like material which will be referred to as the
process fluid. The process fluid requiring heating by the present embodiment is at
a high pressure, i.e. a range including 500 psi.
[0009] In reducing the invention to practice, the process fluid being heated is a highly
viscous slurry of finely dispersed coal, or petroleum coke, suspended in a hydrocarbon
liquid. With the coal, or petroleum coke, homogenized with the oil, the resulting
slurry is atomized in a burner developing the products of combustion in a furnace.
Atomizing the slurry, with the type of burner available, requires a pressure ranging
from 100 to 500 psi.
[0010] As the slurry being heated passes through the inventive embodiment, build-up on the
heating surfaces has to be obviated. Solid build-up on the heating surfaces would
generate prohibitive pressure drops in the flow stream of the slurry. Finally, a degree
of agitation of the slurry is required to elevate the coefficient of heat transfer
between the heating surface and the slurry.
[0011] From one viewpoint, the embodiment of the invention centers about a hollow casing
through which the highly viscous slurry is passed. The heating element within the
casing is given the form of-a chamber.whose surface sports'pins mounted on the external
surface of the elongated chamber. The elongated chamber, radially disposed within
the casing, is rotated about the axis common with the axis of the casing to break
up the laminar flow of the slurry passing over its surface. The chamber is heated
by steam introduced from a source outside the casing. The steam condenses as it gives
up its heat to the slurry, the condensed water being continuously withdrawn from the
chamber. All the objectives are met with this embodiment, leaving only the mechanical
complications of the seals necessary to contain the fluids and introduce a rotating
mechanism for the chamber as a heating element.
The Basic Structure
[0012] The drawing discloses a casing 1 which is in the form of a hollow cylinder. The broken
midsection indicates greater length than otherwise implied within the limitations
of the drawing figure. The first actual reduction to practice has a length in the
order of 14 feet, and an inside diameter of about 16inches. The process fluid is provided
an entry 2 near the lower end of casing 1. The heated process fluid leaves the casing
1 via upper exit 3.
[0013] Although the actual reduction to practice fiows the process fluid up through casing
1, it is to be understood that this direction of flow is not a limitation of the invention.
In the actual reduction to practice, the process fluid was first flowed downward over
the heating element. However, it presently appears advisable to flow the process fluid
into entry 2 and out of exit 3, as disclosed in the drawing.
[0014] Within casing 1, an elongated, cylindrical, bulb-shaped chamber 4 presents its outside
surface to the process fluid flowed into, and through, casing 1. A motor 5 is mounted
externally, and on the upper portion of, casing 1. A power train links motor 5 to
shaft 6, shaft 6 extending down through the upper closure of casing 1 to connect to
the upper end of chamber 4. Thus, with chamber 4 properly supported for rotation within
casing 1, motor 5 imparts the speed of rotation desired for chamber 4 as the external
surface of chamber 4 transfers its heat to the process fluid flowing through casing
1.
[0015] Once the concept of a cylindrical flow casing, and an internally supported chamber
rotated by a power means is accepted, design of their sizes establishes the acceptable-pressure
drop in the flow stream of the process fluid heated by this arrangement. The quantity
of the process stream, the internal diameter of casing 1, the external diameter of
chamber 4, and the speed of rotation imparted by motor 5, are adjusted under sound
engineering principles to deliver the process fluid at the acceptable pressure and
heated to the required temperature. Further, this sizing establishes the rate of flow
of the process fluid through casing 1 which will militate against the precipitation
of any solid material from the flow stream and its collection on the surfaces within
casing 1 which will increase the pressure drop.
Seals
[0016] Under the broad concepts of the invention, the embodiment has several moving parts
requiring effective bearings and seals. As a beginning, chamber 4 is extended by a
neck 10 through the lower end of casing 1. As the chamber 4 and its neck 10 are rotated,
the seal between the neck and casing end must be provided at 11. Concomitantly, a
bearing 12 is provided outboard of the seal 11 between the end of the casing 1 and
the neck 10.
[0017] Steam, as a convenient heating medium, is flowed into the interior of chamber, or
drum, 4. Specifically, the steam is connected to the lower end of supply tube 13 through
a steam joint 14. This supply tube 13 is fixed to steam drum 4 and neck 10. Spider
structure 15 is disclosed within steam drum 4, extending from the steam tube 13 to
the interior wall of steam drum 4. Therefore, drum, neck, and tube rotate as a unit
in steam joint 14. While this rotation is taking place, the steam flowed into steam
drum 4 is giving u
p its heat to the internal wall of the drum 4, condensing and is withdrawn from the
lower end of neck 10 at 16.
[0018] Shifting attention to the upper portion of casing 1, shaft 6, linked to motor 5,
is extended vertically down through the upper wall closure of casing 1 to connect
to the upper end of drum 4 and impart the desired rotation to the drum 4. The sealing
problem is somewhat simpler on the upper end of casing
1. A seal is provided at 20 and a bearing is provided at 21 between casing 1 and shaft
6. With seals and bearings provided as indicated, the process flui-d, even at its
high pressure, is contained within casing 1, entering through 2 and exiting through
3.
Operation
[0019] Although the overall operation of the embodiment of the invention has been covered
piecemeal while describing its configuration and arrangement, a review is in order.
The highly viscous, high pressure slurry, or process fluid, is preferably passed upward
through the casing 1 from inlet 2 to outlet 3. The rate of flow is designed to be
high enough to prevent settling of the solid material from the slurry into accumulation
on the parts within the casing. Of course, the rate of flow must also be compatible
with the heating surface contacted and the temperature rise required.
[0020] In start-up of the system, it has been found highly desirable to purge casing 1 of
any vapor. To facilitate this purging, vent valve 23 is installed through the upper
closure of casing 1. At this high point of vertical casing 1, valve 23 can be opened
at the proper time to withdraw any vapor collecting in the upper part of casing 1
and insure that the process fluid has packed the entire volume of casing 1.
[0021] Steam drum 4 rotates within the fluid-packed casing 1 as the slurry flows over its
outside surface. This movement of the external heating surface of the drum resists
any tendency .to form laminar flow by the slurry as it is heated. To further enhance
the introduction of turbulence in the slurry, and thereby elevate the heat transfer
coefficient, pins 25 are carried on the surface of drum 4. These pins not only extend,
or ex- pane, the effective heat transfer surface of the drum, but further promote
the mechanical agitation of the slurry as the drum is rotated. Some degree of continued
mixing is brought about, but more importantly, reduction of laminar flow is insured
by this structure.
[0022] The seals between the moving parts of the steam drum, drum neck, casing, and motor
shaft, can be regarded as conventional. Various specific and effective forms are available.
With the heated, cooling, and heating fluids contained within their respective volumes
by proper seals, the end result is that the slurry discharged from outlet 3 is presumably
made available for atomization in a downstream burner, not shown.
[0023] From the foregoing, it will be seen that this invention is one well adapted to attain
all of the ends and objects hereinabove set forth, together with other advantages
which are obvious and inherent to the apparatus.
[0024] - It will be understood that certain features and subcombinations are of utility
and may be employed without reference to other features and subcombinations. This
is contemplated by and is within the scope of the invention.
[0025] As many possible embodiments may be made of the invention without departing from
the scope thereof, it is to be understood that all matter herein set.forth or shown
in the accompanying drawings is to be interpreted in an illustrative and not in a
limiting sense.