Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Improvements relating to the Refining of Waste Oil
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.
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.
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.
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.
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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.
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.
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.
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.
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.
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
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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.
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.
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.
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.
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
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is heated before being introduced into the reservoir tank, and is heated
further
within the reservoir tank by conventional means.
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.
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.
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.
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.
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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.
5 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.
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.
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.
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
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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
30kW, and most preferably greater than 50kW.
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.
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
(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
(b) an apparatus for heating liquid material, the apparatus comprising a
reaction chamber within which , in use, a swirling body of said material is
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created, and a source of microwave radiation adapted to exposeng the swirling
body of material to microwave radiation.
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.
The invention will now be described in greater detail, by way of illustration
only,
with reference to the accompanying drawings, in which
Figure 1 is a side view, partly cut-away, of apparatus according to the
invention;
Figure 2 is a front view, partly cut-away, of apparatus according to the
invention;
Figure 3 is an exploded view of a reactor that forms part of apparatus
according to the invention;
Figure 4 is a schematic of the reactor connected to peripheral equipment;
Figure 5 is a schematic cross-sectional view of an alternative reactor for the
apparatus of Figures 1 to 4;
Figure 6 is a cross-sectional view along the line VI-VI in Figure 5;
Figure 7 is a cross-sectional view along the line VII-VII in Figure 5; and
Figure 8 is a cross-sectional view along the line VIII-VIII in Figure 5.
Apparatus according to the invention is shown in Figures 1 and 2. The
apparatus comprises a reservoir tank 10 that forms the lower part of a
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distillation column 20 (only part of which is shown in Figures 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 Figures 1 and 2, for clarity) including a standing platform
to
facilitate maintenance of the apparatus.
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.
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 Figure 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.
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
200mm. 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 80mm. In
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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.
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.
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.
Figure 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
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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.
5 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-
10 orientated feed port 38 to which the upper injection pipe 18 is connected.
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).
The glass tube 40 is secured in place by means of tightening bolts 55 (only
one of which is shown in Figure 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 Figure 3), preventing gas, liquid or microwave radiation
escaping in the event of the glass tube 40 or gaskets 41,43 failing.
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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.
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.
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.
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.
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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.
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).
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.
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
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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.
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.
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.
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.
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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.
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.
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.
Figure 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 Figure 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.
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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.
5 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
10 transfer unit 60 before it is collected in storage tank 61.
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
15 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.
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.
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.
Figure 5 shows an alternative, and presently preferred, reactor 130 that
differs
in several respects from the reactor 30 shown in Figure 3. In particular, this
alternative reactor 130 includes a catalytic rod 200 that extends along a
central
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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.
The outlet port 131 includes a support 184 and a turbine rotor 186, which are
shown in Figures 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 Figure 5.
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.
The inlet port 132 includes a support 194 for the catalytic rod, which is
shown
in Figures 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,
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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.
As shown in Figures 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.
In all other respects, the alternative reactor 130 shown in Figure 5 is
identical
to the reactor shown in Figure 3.
