U.S. patent application number 11/917498 was filed with the patent office on 2008-08-28 for process for cracking of waste oil by microwave.
Invention is credited to John Tooley.
Application Number | 20080202982 11/917498 |
Document ID | / |
Family ID | 34855583 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080202982 |
Kind Code |
A1 |
Tooley; John |
August 28, 2008 |
Process for Cracking of Waste Oil by Microwave
Abstract
A process and apparatus for heating liquid material, which are
particularly suitable for refining waste oil, are disclosed. The
process comprises the steps of creating a swirling body of liquid
material, such as waste oil, within a reaction chamber, and
exposing the swirling body of material to microwave radiation.
Inventors: |
Tooley; John; (Nottingham,
GB) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
34855583 |
Appl. No.: |
11/917498 |
Filed: |
June 12, 2006 |
PCT Filed: |
June 12, 2006 |
PCT NO: |
PCT/GB2006/050151 |
371 Date: |
December 13, 2007 |
Current U.S.
Class: |
208/106 ;
422/224 |
Current CPC
Class: |
B01J 19/126 20130101;
B01J 2219/00182 20130101; B01J 19/26 20130101; B01J 2219/00164
20130101; B01J 2219/1215 20130101; B01J 2219/1272 20130101; B01J
2219/1245 20130101; B01J 2219/1242 20130101; B01J 4/002 20130101;
B01J 19/2405 20130101; B01J 2219/0877 20130101; B01J 2219/00153
20130101; B01J 2219/1239 20130101; B01J 2219/00094 20130101; B01J
2219/1946 20130101; B01J 2219/1266 20130101; C10G 32/02 20130101;
B01J 2219/185 20130101; C10G 31/06 20130101; B01J 2219/0892
20130101; B01J 2219/1224 20130101; B01J 2219/1269 20130101 |
Class at
Publication: |
208/106 ;
422/224 |
International
Class: |
C10G 15/08 20060101
C10G015/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 15, 2005 |
GB |
0512183.5 |
Claims
1. A process for refining waste oil, the process comprising
transferring waste oil from a reservoir tank into a reaction
chamber such that a swirling body of waste oil is formed within the
reaction chamber, and exposing the swirling body of waste oil to
microwave radiation such that cracking reactions occur, wherein
waste oil that cools within the reaction chamber before undergoing
any cracking is replaced from below by swirling bodies of waste oil
at a higher temperature, and the cooler waste oil falls, under the
action of gravity, along a circuit conduit into the reservoir
tank.
2. A process as claimed in claim 1, wherein waste oil is
transferred by one or more injection conduits from a reservoir tank
either directly into the reaction chamber, or into the circuit
conduit that communicates with the reaction chamber, such that a
swirling body of waste oil is formed within the reaction
chamber.
3. A process as claimed in claim 2, wherein a swirling body of
waste oil is formed within the circuit conduit, which communicates
with an opening in a lower part of the reaction chamber, and this
swirling body rises by thermal effects into the reaction
chamber.
4. A process as claimed in claim 3, wherein the waste oil is guided
by the one or more injection conduits into a portion of the circuit
conduit that is offset from its central, longitudinal axis, along a
direction that is orientated transversely to that axis.
5. A process as claimed in claim 1, wherein as the cracking
reactions refine the waste oil and the products are removed, the
waste oil is replenished within the reservoir tank so as to
maintain the level of waste oil within the reservoir tank
substantially constant.
6. A process as claimed in claim 1, wherein the waste oil is heated
before being introduced into the reservoir tank, and is heated
further within the reservoir tank.
7. A process as claimed in claim 1, wherein a microwave radiation
sensitiser is added to the waste oil before it is transferred to
the reaction chamber.
8. A process as claimed in claim 7, wherein the sensitiser is added
to the waste oil before it is introduced into the reservoir
tank.
9. A process as claimed in claim 8, wherein other additives are
also added to the waste oil before it is introduced into the
reservoir tank.
10. A process as claimed in claim 1, wherein the circuit conduit
extends from an opening in the lower part of the reaction chamber
to a port in a lower portion of the reservoir tank.
11. A process as claimed in claim 1, wherein solid sediments and
other heavy materials build up in a lower portion of the reservoir
tank, and this heavy material is intermittently drained through an
outlet port in the base of the reservoir tank.
12. A process as claimed in claim 1, wherein a catalytic substrate
is situated within the reaction chamber during exposure of the
swirling body of material to microwave radiation.
13. A process as claimed in claim 1, wherein the reaction chamber
is housed within an electrically-conductive jacket, with an inert
gas-filled space separating the reaction chamber from the wall of
the jacket, and microwave radiation enters the jacket through a
window, before entering the reaction chamber to be absorbed by the
swirling body of waste oil.
14. A process as claimed in claim 13, wherein the entire reaction
chamber is exposed to microwave radiation.
15. A process as claimed in claim 13, wherein a waveguide transmits
the microwave radiation from a source to the window of the
jacket.
16. A process as claimed in claim 1, wherein vapour products, and
also any entrained liquid droplets and solid particles, escape from
the reaction chamber through an upper opening of the reaction
chamber.
17. A process as claimed in claim 16, wherein the vapour products,
and any entrained liquid droplets and solid particles, passing
through the upper opening of the reaction chamber are transferred
to an upper portion of the reservoir tank where the entrained
liquid droplets and solid particles are returned to the waste
oil.
18. A process as claimed in claim 17, wherein the vapour products
flow into a product recovery apparatus through an upper outlet port
of the reservoir tank.
19. An apparatus for refining waste oil, the apparatus comprising a
reservoir tank, at least one injection conduit configured to
transfer the waste oil from the reservoir tank into the reaction
chamber such that a swirling body of waste oil is formed within the
reaction chamber, in use, and a source of microwave radiation
adapted to expose the swirling body of waste oil to microwave
radiation such that cracking reactions occur, wherein the apparatus
is adapted such that waste oil that cools, in use, within the
reaction chamber before undergoing any cracking is replaced from
below by swirling bodies of waste oil at a higher temperature and
the cooler waste oil falls, under the action of gravity, along a
circuit conduit into the reservoir tank.
20. An apparatus as claimed in claim 19, wherein the swirling body
of waste oil is created within the reaction chamber by the one or
more injection conduits that transfer waste oil from a reservoir
tank either directly into the reaction chamber, or into the circuit
conduit that communicates with the reaction chamber, such that a
swirling body of waste oil is formed within the reaction
chamber.
21. An apparatus as claimed in claim 20, wherein the one or more
injection conduits are adapted to guide the waste oil into a
portion of the circuit conduit that is offset from its central,
longitudinal axis, along a direction that is orientated
transversely to that axis.
22. An apparatus as claimed in claim 20, wherein the reaction
chamber is cylindrical, with open upper and lower ends, and is
orientated generally vertically.
23. An apparatus as claimed in claim 22, wherein the portion of the
circuit conduit that is immediately below the reaction chamber is
orientated vertically, and the injection conduits are adapted to
feed the waste oil into the circuit conduit in a generally
horizontal direction.
24. An apparatus as claimed in claim 23, wherein the open lower end
of the reaction chamber is in sealed communication with the circuit
conduit, and has an internal diameter that matches the internal
diameter of the circuit conduit.
25. An apparatus as claimed in claim 19, wherein the entire wall of
the reaction chamber is formed from a heat-resistant glass.
26. An apparatus as claimed in claim 19, wherein the circuit
conduit extends from an opening in the lower part of the reaction
chamber to a port in a lower portion of a reservoir tank.
27. An apparatus as claimed in claim 19, wherein a catalytic
substrate is situated within the reaction chamber.
28. An apparatus as claimed in claim 27, wherein the catalytic
substrate comprises carbon as a catalyst.
29. An apparatus as claimed in claim 28, wherein the catalytic
substrate has the form of a rod that extends along a central axis
of the reaction chamber.
30. An apparatus as claimed in claim 27, wherein the catalytic
substrate is mounted at its ends, with the mountings being situated
within inlet and outlet ports for the reaction chamber.
31. An apparatus as claimed in claim 30, wherein each of the
mountings comprises a central hub for receiving an end portion of
the catalytic substrate, and a plurality of radial support
struts.
32. An apparatus as claimed in claim 31, wherein the radial support
struts in the inlet port have the form of deflector blades, the
deflector blades being adapted to deflect waste oil flowing into
the reaction chamber transversely relative to the longitudinal axis
of the reaction chamber so as to facilitate formation of a swirling
body of waste oil.
33. An apparatus as claimed in claim 19, wherein a microwave
barrier is disposed within an outlet port for the reaction chamber,
and the microwave barrier comprises one or more electrically
conductive members configured to prevent escape of microwave
radiation from the reaction chamber through the outlet port.
34. An apparatus as claimed in claim 33, wherein the microwave
barrier has the form of a turbine rotor that is adapted to be
rotated by material exiting the reaction chamber through the outlet
port.
35. An apparatus as claimed in claim 34, wherein the apparatus
includes means for monitoring the rotation of the turbine rotor,
and means for calculating therefrom the rate of flow through the
outlet port.
36. An apparatus as claimed in claim 19, wherein the reaction
chamber is housed within an electrically-conductive jacket.
37. An apparatus as claimed in claim 36, wherein the reaction
chamber is mounted co-axially within a cylindrical jacket, with an
inert gas-filled space separating the reaction chamber from the
wall of the jacket.
38. An apparatus as claimed in claim 37, wherein the jacket
includes a window through which microwave radiation is able to
enter the jacket, before entering the reaction chamber to be
absorbed by the swirling body of waste oil.
39. An apparatus as claimed in claim 38, wherein the window is
dimensioned and configured such that the entire reaction chamber is
exposed to microwave radiation.
40. An apparatus as claimed in claim 38, wherein the apparatus
includes a waveguide that transmits the microwave radiation from a
source to the window of the jacket.
41. An apparatus as claimed in claim 19, wherein the apparatus
includes means for separating the products of the cracking
reactions.
42. An apparatus as claimed in claim 41, wherein the reaction
chamber has an upper opening through which vapour products, and
also any entrained liquid droplets and solid particles, are able to
escape from the reaction chamber.
43. An apparatus as claimed in claim 42, wherein the apparatus is
adapted such that the vapour products, and any entrained liquid
droplets and solid particles, passing through the upper opening of
the reaction chamber are transferred to an upper portion of the
reservoir tank where the entrained liquid droplets and solid
particles are returned to the waste oil.
44. An apparatus as claimed in claim 43, wherein the reservoir tank
includes an upper outlet port through which the vapour products are
able to flow into a product recovery apparatus.
Description
[0001] This invention relates primarily to the refining of waste
oil, and in particular to microwave-activated cracking of waste
oil. However, the process and apparatus of the invention may have
applications in other fields.
[0002] A large proportion of the waste oil generated in the UK is
collected and subjected to a rudimentary reprocessing treatment
that removes water and solid contaminants to form a recovered fuel
oil. The recovered fuel oil is then used as an alternative fuel in
power stations, heaters at quarries, cement & lime kilns, and
industrial furnaces. However, from 2006, the European Waste
Incineration Directive will prevent many of the current users of
recovered fuel oil from burning it.
[0003] Many attempts have been made to devise a commercially viable
process for refining waste oil, but none have been entirely
satisfactory. This is because waste oils pose a significant problem
due to their variable properties, and high sediment, sulphur and
chlorine content. Refining waste oil to base oils is possible and
is practised to a certain degree, but presently available products
are not accepted as being equivalent to base oil. Consequently,
there is a need for a process to refine waste oils to produce
hydrocarbon fuels that conform to normal specifications in respect
of product quality, and in particular sulphur content.
[0004] A current area of research in the field of waste oil
refining is concerned with microwave-activated cracking. Typical
hydrocarbons do not interact with microwaves because they are
non-polar. However, in the presence of appropriate sensitisers,
photon absorption takes place that is sufficiently intense for "hot
spots" to form that are localised in both space and time. It has
been demonstrated that sufficiently high local temperatures and
pressures exist for free radical reactions to occur at bulk
temperatures well below those required for thermally activated
processes.
[0005] A satisfactory microwave-activated refining process for
waste oil has yet to be developed because of the large amount of
heavy material and sediments produced by such a process, and the
high temperature of the "hot spots" causing breakages of the
microwave conducting materials.
[0006] There has now been devised an improved process, and an
improved apparatus, which overcome or substantially mitigate the
above-mentioned and/or other disadvantages associated with the
prior art.
[0007] According to a first aspect of the invention, there is
provided a process for refining waste oil, the process comprising
creating a swirling body of waste oil within a reaction chamber,
and exposing the swirling body of waste oil to microwave radiation
such that cracking reactions occur.
[0008] According to a further aspect of the invention, there is
provided an apparatus for refining waste oil, the apparatus
comprising a reaction chamber within which, in use, a swirling body
of waste oil is created, and a source of microwave radiation
adapted to expose the swirling body of waste oil to microwave
radiation such that cracking reactions occur.
[0009] The process and apparatus according to the invention are
advantageous principally because the swirling movement of the body
of waste oil within the reaction chamber reduces the risk of the
high localised temperatures and pressures created by the microwave
radiation damaging the apparatus. In addition, the rotation of the
body of waste oil ensures that the waste oil remains in a fluid
form when lighter fractions of the waste oil have been removed.
[0010] In preferred embodiments, waste oil is transferred from a
reservoir tank, either directly into the reaction chamber or more
preferably into a circuit conduit that communicates with the
reaction chamber, via one or more injection conduits such that a
swirling body of waste oil is formed within the reaction chamber.
This arrangement is particularly advantageous because there is no
need for the apparatus to include a mechanism disposed within the
reaction chamber or the circuit conduit that would be liable to
restrict the passage of heavy material produced by the cracking
reactions, and hence potentially cause a blockage.
[0011] Most preferably, a swirling body of waste oil is formed
within the circuit conduit, which preferably communicates with an
opening in a lower part of the reaction chamber, and this swirling
body preferably rises by thermal effects into the reaction chamber.
The one or more injection conduits preferably therefore guide the
waste oil into a portion of the circuit conduit that is offset from
its central, longitudinal axis, along a direction that is
orientated transversely to that axis.
[0012] In presently preferred embodiments, the reaction chamber is
cylindrical, with open upper and lower ends, and is orientated
generally vertically. The portion of the circuit conduit that is
immediately below the reaction chamber is preferably also
orientated vertically, and the injection conduits preferably feed
the waste oil into the circuit conduit in a generally horizontal
direction. Furthermore, the open lower end of the reaction chamber
is preferably in sealed communication with the circuit conduit, and
preferably has an internal diameter that matches the internal
diameter of the circuit conduit.
[0013] At least a portion of the wall, and most preferably the
entire wall, of the reaction chamber is preferably formed from a
material, such as a heat-resistant glass, that has a high
transmittance of microwave electromagnetic radiation.
[0014] The waste oil is preferably held within a reservoir tank
from which the waste oil is transferred as required to the reaction
chamber. As the cracking reactions refine the waste oil and the
products are removed, the waste oil is preferably replenished
within the reservoir tank so as to maintain the level of waste oil
within the reservoir tank substantially constant. Most preferably,
the waste oil is heated before being introduced into the reservoir
tank, and is heated further within the reservoir tank by
conventional means.
[0015] A suitable microwave radiation sensitiser is preferably
added to the waste oil before it is transferred to the reaction
chamber. Most preferably, the sensitiser is added to the waste oil
before it is introduced into the reservoir tank. Suitable
sensitisers are known in the art. Other additives, such as a
catalyst, are also preferably added to the waste oil before it is
introduced into the reservoir tank.
[0016] Waste oil that cools within the reaction chamber before
undergoing any cracking, as well as larger solid sediments, is
preferably replaced from below by swirling bodies of waste oil at a
higher temperature. The circuit conduit preferably extends from an
opening in the lower part of the reaction chamber to a port in a
lower portion of the reservoir tank. The cooler waste oil and solid
sediments preferably fall, under the action of gravity, along the
circuit conduit into the reservoir tank such that there is a
continuous flow of waste oil from the reservoir tank, into the
circuit conduit, and back into the reservoir tank. This continuous
flow maintains the waste oil in the circuit conduit in a fluid
state to ensure the continued functioning of the apparatus.
[0017] Solid sediments and other heavy materials, such as carbon,
metals and catalyst residue, build up in a lower portion of the
reservoir tank during use. This heavy material, commonly referred
to as tar, is preferably intermittently drained through an outlet
port in the base of the reservoir tank in order to ensure that the
waste oil within the reservoir tank remains sufficiently fluid to
circulate. In order to facilitate draining of the tar, the base of
the reservoir tank is preferably tapered, eg generally
frusto-conical, in shape. A conventional auger unit may be used to
drain this heavy material.
[0018] As discussed above, a catalyst may be added to the waste oil
before it is introduced into the reservoir tank. Alternatively, or
preferably in addition, a catalytic substrate may be situated
within the reaction chamber during use.
[0019] For instance, the catalytic substrate may comprise carbon as
a catalyst. In presently preferred embodiments, the catalytic
substrate has the form of a rod that extends along a central axis
of the reaction chamber.
[0020] The catalytic substrate is preferably mounted at its ends,
with the mountings being situated outside the reaction chamber. In
presently preferred embodiments, the mountings are situated within
inlet and outlet ports for the reaction chamber. In particular,
each of the mountings preferably comprises a central hub for
receiving an end portion of the catalytic substrate, and a
plurality of radial support struts. In the inlet port, the radial
support struts preferably have the form of deflector blades, the
deflector blades being adapted to deflect waste oil flowing into
the reaction chamber transversely relative to the longitudinal axis
of the reaction chamber so as to facilitate formation of a swirling
body of waste oil.
[0021] A microwave barrier is preferably disposed within an outlet
port for the reaction chamber, and the microwave barrier preferably
comprises one or more electrically conductive members suitable for
preventing escape of microwave radiation from the reaction chamber
through the outlet port. In presently preferred embodiments, the
microwave barrier has the form of a turbine rotor that is caused to
rotate by material exiting the reaction chamber through the outlet
port. Rotation of the turbine rotor may therefore be monitored,
during use, and the rate of flow through the outlet port thereby
calculated.
[0022] In presently preferred embodiments, the mounting for the
catalytic substrate within the outlet port preferably also acts as
a mounting for the turbine rotor. The turbine rotor is preferably
therefore mounted about the central hub of the mounting.
[0023] The reaction chamber is preferably housed within a jacket
formed of a material that does not absorb microwave radiation, such
as stainless steel or aluminium. In particular, the reaction
chamber is preferably mounted co-axially within a cylindrical
jacket, with an inert gas-filled space separating the reaction
chamber from the wall of the jacket. Microwave radiation preferably
enters the jacket through a window, before entering the reaction
chamber to be absorbed by the swirling body of waste oil. The
window is preferably dimensioned and configured such that the
entire reaction chamber is exposed to microwave radiation. A
waveguide preferably transmits the microwave radiation from a
suitable source to the window of the jacket. The microwave
radiation preferably has a frequency at the lower end of the
microwave range, eg approximately 1 GHz frequency, and preferably
has a power of greater than 30 kW, and most preferably greater than
50 kW.
[0024] In preferred embodiments of the apparatus according to the
invention the products of the cracking reactions are separated. In
particular, the reaction chamber preferably has an upper opening
through which vapour products, and also any entrained liquid
droplets and solid particles, escape from the reaction chamber. The
vapour products, and any entrained liquid droplets and solid
particles, passing through the upper opening of the reaction
chamber are preferably transferred to an upper portion of the
reservoir tank where the entrained liquid droplets and solid
particles are returned to the waste oil. The reservoir tank
preferably includes an upper outlet port through which the vapour
products then flow into a product recovery apparatus. The product
recovery apparatus may have any form suitable for cooling and
separating the vapour products into useful fractions.
[0025] As mentioned above, the process and apparatus of the
invention may be useful in applications other than the refining of
waste oil. Thus, in its broadest aspects, the present invention
provides
[0026] (a) a process for heating liquid material, the process
comprising creating a swirling body of said material within a
reaction chamber, and exposing the swirling body of material to
microwave radiation; and
[0027] (b) an apparatus for heating liquid material, the apparatus
comprising a reaction chamber within which, in use, a swirling body
of said material is created, and a source of microwave radiation
adapted to exposing the swirling body of material to microwave
radiation.
[0028] Examples of other fields of application in which the
invention may be used are processing of foodstuffs, drying of
materials, viscosity reduction of heavy fuel oils, and many
others.
[0029] The invention will now be described in greater detail, by
way of illustration only, with reference to the accompanying
drawings, in which
[0030] FIG. 1 is a side view, partly cut-away, of apparatus
according to the invention;
[0031] FIG. 2 is a front view, partly cut-away, of apparatus
according to the invention;
[0032] FIG. 3 is an exploded view of a reactor that forms part of
apparatus according to the invention;
[0033] FIG. 4 is a schematic of the reactor connected to peripheral
equipment;
[0034] FIG. 5 is a schematic cross-sectional view of an alternative
reactor for the apparatus of FIGS. 1 to 4;
[0035] FIG. 6 is a cross-sectional view along the line VI-VI in
FIG. 5;
[0036] FIG. 7 is a cross-sectional view along the line VII-VII in
FIG. 5; and
[0037] FIG. 8 is a cross-sectional view along the line VIII-VIII in
FIG. 5.
[0038] Apparatus according to the invention is shown in FIGS. 1 and
2. The apparatus comprises a reservoir tank 10 that forms the lower
part of a distillation column 20 (only part of which is shown in
FIGS. 1 and 2), and three reactors 30. The distillation column 20
is of known form, and is used to separate fractions of the refined
oil by distillation. The reservoir tank 10 and reactors 30 are
mounted within an appropriate support frame (parts of which are not
shown in FIGS. 1 and 2, for clarity) including a standing platform
to facilitate maintenance of the apparatus.
[0039] The reservoir tank 10 comprises a generally cylindrical main
portion, a generally dome-shaped upper portion, and a
frusto-conical lower portion. An upper outlet port 11 is formed at
the apex of the upper portion of the reservoir tank 10, the
remainder of the distillation column 20 extending upwardly
therefrom, and a lower outlet port 12 is formed at the base of the
reservoir tank 10. The reservoir tank 10 also includes an inlet
port (not shown in the Figures) through which pre-heated waste oil,
which contains appropriate amounts of a microwave sensitiser and
other additives, is supplied to the reservoir tank 10. The
reservoir tank 10 also includes means for further pre-heating the
waste oil.
[0040] A lower circuit port 14 is formed in a side wall of the
lower portion of the reservoir tank 10, and an upper circuit port
24 is formed in an upper wall of the upper portion of the reservoir
tank 10. As shown most clearly in FIG. 2, the lower circuit port 14
is connected to three lower circuit pipes 15, and the upper circuit
port 24 is connected to three upper circuit pipes 25.
[0041] Each lower circuit pipe 15 extends generally horizontally
away from the reservoir tank 10 and then vertically upwards into
connection with an inlet port 32 of one of the reactors 30. Each
lower circuit pipe 15 is formed from several components, but has a
generally constant internal diameter of approximately 200 mm. Each
upper circuit pipe 25 extends generally upwardly and outwardly away
from the upper portion of the reservoir tank 10 to a highest point,
and then vertically downwards into connection with an outlet port
31 of one of the reactors 30. Each upper circuit pipe 25 is formed
from several components, but has a generally constant internal
diameter of approximately 80 mm. In addition, the upper circuit
pipes 25 each include a viewing window 26 that is formed of a
sufficiently transparent material to enable a user to view the
interior of the pipe 25. Inlet port 32 and outlet port 31 have
inline valves (not shown) fitted, such that maintenance work can be
carried out on a reactor 30 without interrupting the flow of oil to
other, still functioning reactors 30.
[0042] A feed pipe 16 of reduced diameter relative to the upper and
lower circuit pipes 15,25 extends horizontally away from a side
wall of the lower portion of the reservoir tank 10, above the lower
circuit pipe 15, to a variable speed pump 17. From the variable
speed pump 17, the feed pipe 16 extends upwardly before dividing
into three branches, one for each of the lower circuit pipes 15.
The three branches of the feed pipe 16 each include a shut-off
valve that enables each branch to be isolated such that maintenance
work can be carried out on a reactor 30 without interrupting the
flow of waste oil to the other, still functioning reactors 30.
[0043] Each branch of the feed pipe 16 includes upper and lower
injection pipes 18. Each upper injection pipe 18 is in fluid
communication with the inlet port 32 of the corresponding reactor
30, and each lower injection pipe 18 is in fluid communication with
the vertical portion of the corresponding lower circuit pipe 15,
such that the injection pipes 18 feed waste oil into the fluid
conduit formed by the inlet port 32 and the lower circuit pipe 15.
Each injection pipe 18 feeds waste oil horizontally, and hence in a
direction that is perpendicular to said fluid conduit, into a
portion of said fluid conduit that is offset from its central, ie
longitudinal, axis. In this way, waste oil is guided along the
curved interior surface of the port 32 or pipe 15, and is hence
given an angular momentum, such that a swirling body of waste oil
is formed within the fluid conduit formed by the vertical portion
of the lower circuit pipe 15 and the inlet port 32.
[0044] FIG. 3 is an exploded view of one of the three reactors 30,
which are all identical in form. The reactor 30 comprises a
cylindrical jacket 33 formed of stainless steel, a microwave window
34 formed in a wall thereof, a reaction chamber in the form of a
glass tube 40, and inlet and outlet ports 32,31. The inner surface
of the jacket has a highly reflective finish to maximise heating
efficiency.
[0045] The jacket 33 comprises annular flanges at each end to each
of which is fixed an endplate 35,35a, a gasket 36,36a being
situated between the respective annular flanges and corresponding
endplates 35,35a. Each endplate 35,35a includes a central circular
opening, and the inlet and outlet ports 31,32 of the reactor 30
extend therefrom. The inlet port 32 includes a
tangentially-orientated feed port 38 to which the upper injection
pipe 18 is connected.
[0046] The endplates 35,35a connect to the jacket 33 using the
gaskets 36,36a and tightening equally spaced nuts and bolts (not
shown) that are located around the endplates 35,35a. A gasket 39 is
fitted between the flanged inlet 32 and endplate 35, the two
components being secured together by bolts (not shown). A gasket 41
is placed into a rebate (not visible) located on flanged inlet port
32, the reaction chamber, ie glass tube 40, being inserted into the
reactor 30 and fitting inside the rebate, on gasket 41. A metal
ring 42 and flexible gaskets 43 are placed in position on the glass
tube 40. A gasket 44 is placed in position on flanged outlet port
31 and offered up to endplate 35, an inner guiding ring 45 being
placed inside the glass tube 40. Flanged inlet port 31 is then
bolted to endplate 35 by bolts (not shown).
[0047] The glass tube 40 is secured in place by means of tightening
bolts 55 (only one of which is shown in FIG. 3) which are housed in
tubular projections 56 extending from the flanged outlet 31, and
which press the metal ring 42 and flexible gaskets 43 onto the
glass tube 40 and gasket 41, creating a gas/liquid/microwave seal.
The open ends of the tubular projections 56 are then closed by
threaded sealing plugs 57 and sealing rings 58 (again only one of
which is shown in FIG. 3), preventing gas, liquid or microwave
radiation escaping in the event of the glass tube 40 or gaskets
41,43 failing.
[0048] In this way, the reaction chamber (glass tube) 40 is
captivated between the inlet and outlet ports 31,32, and extends
along the longitudinal axis of the interior of the jacket 33. The
upper and lower circuit pipes 15,25 are in fluid communication
through the reaction chamber 40 of the reactor 30. The reaction
chamber 40 is formed from heat-resistant glass through which high
energy microwaves may pass with minimal scattering, and which is
sufficiently strong, heat-resistant and durable to withstand the
temperatures and pressures generated within the reaction chamber 40
during use. The glass tube 40 is dimensioned such that the
microwave energy is "full wave", thereby maximising heating
efficiency.
[0049] The jacket 33 also includes an opening in its side wall, and
an extension of rectangular cross-section extending therefrom. The
microwave window 34, which comprises a frame and a rectangular
plate of heat-resistant glass, is mounted to the outer end of the
extension. The microwave window 34 is formed such that its
longitudinal axis is orientated parallel to the longitudinal axis
of the reaction chamber 40.
[0050] A waveguide 50 is connected to the microwave window 34, and
transmits microwaves from a suitable microwave generator (not shown
in the Figures) into the interior of the reactor 30. Currently
available microwave generators are capable of producing up to 100
kW microwaves, which is sufficient for the process of the
invention, but higher-energy microwaves could be utilised.
[0051] In use, collected waste oil is firstly pre-treated to remove
excess water and sediment. Appropriate amounts of microwave
sensitiser and other additives, such as a catalyst, are added to
the waste oil, and then the waste oil is heated using a heat
exchanger. The pre-heated waste oil is introduced into the
reservoir tank 10 through its inlet port, and is then pre-heated
further within the reservoir tank 10.
[0052] The variable speed pump 17 is used to withdraw waste oil
from the reservoir tank 10, and inject it into the lower circuit
pipes 15 and the inlet ports 32 of the reactors 30 so as to create
swirling bodies of waste oil. Each swirling body of waste oil is
drawn upwards into the reaction chamber 40 of the reactor 30 by a
so-called thermal siphon effect. The throughput of waste oil
through the tangential inlet 38 may be controlled by appropriate
adjustment of the speed of the pump 17. An increase in pump speed
may be used in order to remove deposits from the surface of the
reaction chamber 40.
[0053] Microwaves generated by the microwave generator are
transmitted along the waveguides 50, and through the microwave
window 34 and the wall of the reaction chamber 40 of each reactor
30. Within the reaction chamber 40 of each reactor 30, the
microwaves are finally absorbed by the swirling body of waste oil.
Microwaves are prevented from escaping the reactor 30 by an in-line
microwave trap (not shown).
[0054] In particular, conduction electrons in the microwave
sensitiser are accelerated in the oscillating electromagnetic field
of the microwaves, creating a discharge of electricity. These
discharges of electricity represent a highly non-equilibrium system
of ionised molecules and electrons in which the kinetic energy of
the electrons is significantly higher than the average temperature
of the system. Furthermore, by virtue of the high temperatures that
are attained very quickly, the local pressures can also be very
high. The electron energy is sufficient to break the chemical bonds
within localised areas of the swirling body of waste oil, forming
free radicals at substantially lower bulk temperatures than in
typical thermal cracking. The other additives act to catalyse or
participate in desirable chemical reactions, such as
desulphurisation and the removal of other inorganic
contaminants.
[0055] The major reactions that occur are free radical cracking
reactions, as well as hydro-cracking reactions, which are possible
by virtue of the high local temperatures and pressures. The
swirling movement of the bodies of waste oil ensures that the high
local temperatures and pressures that activate the cracking
reactions are maintained for only a short period of time before
being dispersed in the bodies of waste oil. This reduces the risk
of the high temperatures and pressures damaging the apparatus, and
in particular rupturing the walls of the reaction chambers 40.
[0056] Inorganic contaminants, mainly sulphur and chlorine, react
with metals or oxides (added as additives) to form relatively
stable compounds such as sulphides and chlorides. Metals, which are
present in the collected waste oil by virtue of engine and bearing
wear as well as metal containing lubricating oils, either react
with sulphur to form sulphides or fall under the action of gravity
along the lower circuit pipe 15 into the reservoir tank 10.
[0057] The cracking reactions produce a wide range of hydrocarbon
products. Vapour, along with entrained liquid droplets and solid
particles, flows through the outlet ports 31 of the reactors 30,
along the upper circuit pipes 25, into the upper portion of the
reservoir tank 10. The entrained liquid droplets and solid
particles re-join the waste oil in the reservoir tank 10 to undergo
further cracking, and the vapour flows through the outlet port 11
of the reservoir tank 10 into the lower bed of packing in the
distillation column 20.
[0058] Waste oil that cools before undergoing any cracking, as well
as larger solid sediments, will be replaced from below by swirling
bodies of waste oil at a higher temperature. The cooler waste oil
and solid sediments will therefore fall, under the action of
gravity, along the lower circuit pipe 15 into the reservoir tank
10. There will therefore be a continuous flow of waste oil from the
reservoir tank 10, through the feed pipe 16, the injection pipes 18
and then the lower circuit pipes 15, back into the reservoir tank
10. This continuous flow maintains the waste oil in a fluid state
to ensure the continued functioning of the apparatus.
[0059] Solid sediments and other heavy materials, such as carbon,
metals and catalyst residue, build up in the lower portion of the
reservoir tank 10 during use. This heavy material, commonly
referred to as tar, is intermittently drained through the lower
outlet port 12 of the reservoir tank 10 in order to ensure that the
waste oil within the reservoir tank 10 remains sufficiently fluid
to circulate. A conventional auger unit may be used to drain this
heavy material.
[0060] The vapour that flows into the lower bed of packing is
cooled, and a heavy fraction condenses and falls back into the
reservoir tank 10. The lighter fraction passes into a middle bed of
packing of the distillation column 20. A diesel range liquid
product is withdrawn from the bottom of the middle bed, and a
naphtha range liquid product is withdrawn from the bottom of an
upper bed of packing. Finally, a gaseous product is withdrawn from
the top of the distillation column 20.
[0061] The rate at which waste oil is fed into the reservoir tank
10 is adjusted so that the level of waste oil within the reservoir
tank 10 is maintained substantially constant, and hence the process
is continuous.
[0062] FIG. 4 shows the general arrangement of the reactor 30
connected to ancillary equipment. Oil is pumped from a holding tank
1 by a pump 3 into the reservoir tank 10 via heat transfer vessel
5. Catalyst held in a catalyst mixing tank 2 is introduced into the
system and mixed with oil as it passes through an inline mixer 4.
An ultrasonic level gauge (not visible in FIG. 4) controls the oil
level in the bottom section of the reservoir tank 10. The oil level
in both the reservoir tank 10 and reactor 30 are equal. The
ultrasonic level gauge is connected to feed pump 3. The pump 3
starts when the oil falls below a pre-determined level within the
reservoir tank 10 and stops when the oil reaches that
pre-determined level, creating a thermo-siphon effect. As the oil
is heated in the reactor 30 the oil vaporises and exits as a
gas.
[0063] The gas enters the distillation column 20 and progresses
through a gas distributor 29 which evenly distributes the gas as it
progresses into the mid section of the distillation column 20. The
gas passes through a collection of pall rings 45 that condense
approximately 80% of the gas into a diesel fraction. Incondensable
gas and lighter oil fractions in the form of gas continue to
progress up through the distillation column 20. The diesel fraction
exits the distillation column 20 via outlet port 11 and travels
through heat transfer unit 5. The hot diesel fraction is cooled in
heat transfer unit 5, pre-heating incoming feedstock oil. The
diesel fraction is further cooled as it passes through heat
transfer unit 60 before it is collected in storage tank 61.
[0064] The diesel fraction can be pumped back into the midsection
of the distillation column 20 by a recirculation pump 62, through a
spray nozzle. The spray helps condense the diesel fraction. Gas
progresses into the top section of the distillation column 20,
where a naphtha fraction is condensed. Uncondensed gas exits the
top of the distillation column 20 and is transferred into a gas
condensing unit 63 where waste water is removed. Gas exits the gas
condensing unit 63 and is stored in gasholder 64. In the event of
pressure build up, gas can be flared off by a ground flare 65.
[0065] The naphtha fraction exits the distillation column 20 via
outlets 66, and is cooled in heat transfer unit 67 before being
stored in storage tank 68.
[0066] The carbon coke, heavy particulates, spent catalyst and
heavy ends are allowed to build up in the bottom of the tank 10
until they reach a vibrating level probe 70. The probe 70 senses
the sediment level and activates a remote warning light, whereupon
the waste is removed from the distillation column 20 using an auger
unit 71.
[0067] FIG. 5 shows an alternative, and presently preferred,
reactor 130 that differs in several respects from the reactor 30
shown in FIG. 3. In particular, this alternative reactor 130
includes a catalytic rod 200 that extends along a central axis of
the reaction chamber 140. The catalytic rod 200 is mounted at its
ends within the inlet and outlet ports 131,132 of the reactor
130.
[0068] The outlet port 131 includes a support 184 and a turbine
rotor 186, which are shown in FIGS. 5 and 6. The support 184
comprises a central pillar that is mounted at each end between a
pair of radial struts that extend from the interior surface of the
outlet port 131, so that the central pillar extends along a central
axis of the outlet port 131. The central pillar of the support 184
includes a recess at its lower end for receiving the upper end of
the catalytic rod 200, as shown most clearly in FIG. 5.
[0069] The turbine rotor 186 is rotatably mounted about the central
pillar of the support 184, and comprises a plurality of blades that
are arranged such that the turbine rotor 186 entirely occludes the
outlet port 131 along axial directions, but defines openings
through which material may flow during use. The turbine blades are
electrically conductive, and hence this arrangement prevents the
escape of microwave radiation from the reaction chamber 140, during
use. Furthermore, material flowing through the outlet port 131 will
impinge upon the turbine rotor 186, and hence impart a rotational
force thereon, during use. In this embodiment of the apparatus
according to the invention the rotation of the turbine rotor 186
may therefore be monitored, and the output rate of the reactor 130
thereby calculated.
[0070] The inlet port 132 includes a support 194 for the catalytic
rod, which is shown in FIGS. 5 and 7. The support 194 comprises
three radial turbine blades 196 extending from a central hub 198,
the central hub 198 having a cylindrical upper portion with a
recess at its upper end for receiving a lower end of the catalytic
rod 200 and a conical lower portion. The turbine blades 196 extend
radially between the interior surface of the inlet port 132 and the
central hub 198, and together define three openings through the
inlet port 132 of equal size. Furthermore, the turbine blades 196
are arranged so that material flowing through the inlet port 132
into the reaction chamber, during use, impinges upon those blades
196 and is deflected transversely in the same direction as that in
which the material is swirling. In this way, the turbine blades 196
do not occlude a large proportion of the inlet port 132, and hence
offer low resistance to flow, but facilitate formation of a
swirling body of material within the reactor chamber 140.
[0071] As shown in FIGS. 5 and 8, the catalytic rod 200 extends
along a central axis of the reactor chamber 140 between the
supports 184,194 of the inlet and outlet ports 131,132. The
catalytic rod comprises carbon, and acts to catalyse the cracking
reactions that occur within the reaction chamber 140.
[0072] In all other respects, the alternative reactor 130 shown in
FIG. 5 is identical to the reactor shown in FIG. 3.
* * * * *