Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A STEAM GENERATOR USING A PLASMA ARC
Field of the invention:
The present invention relates to steam generators. More particularly, the
present invention relates to a steam generator using a plasma arc submerged in
electrolyte.
Background of the invention:
Steam generators are commonly used in industrial and domestic settings. For
example, in agriculture, steam can be used for soil sterilization while
domestically, steam can be used for cleaning fabric and carpets.
Generating steam using heat exchangers is known in the field of heat
transfer. Conventional systems are generally bulky and difficult to transport.
They
also have a slow reaction time due to the inertia of the heating process.
Typically,
a heating element is used to heat a liquid, such as water, to its boiling
point.
A steam generator is a device that uses a heat source to boil water and
convert it into its vapor form, referred to as steam. The heat may be derived
from
an electrical source or the combustion of fuel such as coal, natural gas,
nuclear
fission reactors, etc. To readily have access to steam, these types of steam
generators usually require the heater to remain active and thus waste energy.
Therefore, there is a need for a steam generator to rapidly and efficiently
generate steam when activated.
Hence, in light of the aforementioned, there is a need for an improved system
which, by virtue of its design and components, would be able to overcome some
of the above-discussed prior art concerns.
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Summary of the invention:
The object of the present invention is to provide a device which, by virtue of
its design and components, satisfies some of the above-mentioned needs and is
thus an improvement over other related steam generators known in the prior
art.
In accordance with the present invention, the above mentioned object is
achieved, as will be easily understood, by a steam generator such as the one
briefly described herein and such as the one exemplified in the accompanying
drawings.
According to a first aspect of the present invention, there is provided a
steam
generator using a plasma arc submerged in electrolyte. The steam generator
comprises:
a chamber having a vertical axis, said chamber includes an electrically non-
conductive outer wall, a base surface and a top surface, said base surface
and top surface are located at opposite ends of the chamber along the vertical
axis, wherein the top surface includes at least one aperture for introducing
the
electrolyte and removing the steam;
an electrode assembly comprising:
a first electrode having a longitudinally extending spiral shape along a
longitudinal axis mounted inside the chamber; and
a second electrode having a flat spiral shape in a plane mounted inside
the chamber relative to the first electrode for forming the plasma arc;
an electrical power source to energize the electrode assembly with an input
voltage;
terminal connections operatively connecting the first electrode and the second
electrode to the power source; and
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an electronic rectifier operatively connected between the power source and
the terminal connections, comprising:
a controllable switch for rectifying the input voltage; and
a monitoring-controller connected to the controllable switch for controlling
said controllable switch;
wherein the monitoring-controller engages the controllable switch upon
sensing a substantially zero input voltage for initiating a gradual plasma
arc,
heating the electrolyte and generating steam therefrom.
In some implementations, the base surface includes one aperture for
introducing the electrolyte.
In some implementations, the chamber further comprises a deflector for
urging the electrolyte towards the electrode assembly.
In some implementations, the deflector comprises an electrically non-
conductive and heat resistant material.
In some implementations, the chamber is sized such that the electrolyte
defines a first volume while the first electrode defines a second volume, such
that
a ratio of the first volume to the second volume inside the chamber is between
3
to 15.
In some implementations, the ratio of the first volume to the second volume is
between 6 to 10.
In some implementations, the at least one aperture is closable.
In some implementations, the electrode assembly comprises a high emissivity
material.
In some implementations, the first electrode is a cathode.
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In some implementations, the first electrode has a length starting with a
circular cross-section at the beginning of the length and ending with an oval
cross-section at the end of the length.
In some implementations, the second electrode is an anode.
In some implementations, the longitudinal axis of the first electrode is
substantially parallel to the vertical axis of the chamber.
In some implementations, the plane of the second electrode is substantially
perpendicular to the longitudinal axis of the first electrode.
In some implementations, the first electrode is placed at a distance ranging
between 10 mm to 150 mm from the second electrode.
In some implementations, the first electrode is placed at a distance ranging
between 15.4 mm to 64.5 mm from the second electrode.
In some implementations, the input voltage of the electrical power source
ranges between 200 V to 12 000 V AC.
In some implementations, the input voltage of the electrical power source
ranges between 200 V to 600 V AC.
In some implementations, the terminal connections comprise an electrically
conductive inner core and an electrically non-conductive outer jacket.
In some implementations, the inner core comprises copper.
In some implementations, the outer jacket comprises ceramic.
In some implementations, the electronic rectifier produces a rectified DC
voltage.
In some implementations, the electronic rectifier comprises at least one
current controlling device selected from a group consisting of thyristors,
silicon-
controlled rectifiers and insulated-gate bipolar transistors.
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In some implementations, the electrolyte comprises water and sodium
hydrogen carbonate.
According to a second aspect of the present invention, there is provided a
method for producing a constant flow output of steam using multiple electrode
5 assemblies in a steam generator, the method comprising:
(a) monitoring an input voltage, having alternating input waves, of an AC
electrical power source;
(b) rectifying the input voltage into a rectified voltage;
(c) conducting the rectified voltage to a first electrode assembly when the
input voltage is substantially zero and starting a positive half cycle
input wave;
(d) ceasing the rectified voltage from the first electrode assembly after
conducting the positive half cycle input wave;
(e) waiting for a negative half cycle input wave to pass through; and
(f) conducting the rectified voltage to a second electrode assembly when
the input voltage is substantially zero and starting a subsequent
positive half cycle input wave.
The objects, advantages and features of the present invention will become
more apparent upon reading of the following non-restrictive description of
preferred embodiments thereof, given for the purpose of exemplification only,
with reference to the accompanying drawings.
Brief description of the drawings:
Figure 1 is a cross-section view of a steam generator using a plasma arc
according to an embodiment of the present invention.
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Figure 2 is a perspective view of a first electrode according to an embodiment
of the present invention.
Figure 3 is a perspective view of a second electrode a according to an
embodiment of the present invention.
Figure 4A is a diagram of an input voltage, a rectified voltage and a plasma
current according to an embodiment of the present invention.
Figure 4B is a diagram of an inrush current, a rectified voltage and a plasma
current, initiating the plasma arc, according to an embodiment of the present
invention.
Figure 5 is a schematic view of a steam generation assembly comprising two
steam generators according to an embodiment of the present invention.
Figure 6 a flow chart diagram of a method for producing a constant flow
output of steam using multiple electrode assemblies in a steam generator
according to an embodiment of the present invention.
Detailed description of preferred embodiments of the invention:
In the following description, the same numerical references refer to similar
elements. Furthermore, for the sake of simplicity and clarity, namely so as to
not
unduly burden the figures with several reference numbers, not all figures
contain
references to all the components and features, and references to some
components and features may be found in only one figure, and components and
features of the present invention illustrated in other figures can be easily
inferred
therefrom. The embodiments, geometrical configurations, materials mentioned
and/or dimensions shown in the figures are optional, and are given for
exemplification purposes only.
As shown in Figures 1 to 5, there is provided a steam generator 20 using a
plasma arc submerged in electrolyte 32 for initiating a gradual plasma arc,
heating the electrolyte 32 and generating steam therefrom. In a preferred
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embodiment, the electrolyte 32 comprises water and sodium hydrogen
carbonate. It is understood that the steam generator 20 may also be used with
other types of solvents and electrolytes such as potassium chloride, sodium
hydroxide, sodium nitrate, etc.
The steam generator 20 includes a chamber 22 having a vertical axis 24
wherein a cathode 40 and an anode 42 (first electrode 50 and second electrode
52) are placed therein to form a plasma arc. The term "chamber" is intended to
refer to the volume receiving the electrolyte 32 and its container wherein the
plasma arc is generated to produce steam. The chamber 22 has an electrically
non-conductive outer wall 26 to prevent, among other things, an electrical
discharge. The chamber 22 also includes a base surface 28 and a top surface 30
located at opposite ends along the vertical axis 24. In the illustrated
embodiment
shown in Figure 1, the chamber 22 further includes apertures 34 located on the
top surface 30 for introducing the electrolyte 32 and/or removing the steam.
In
other embodiments, apertures 34 may also be located on the base surface 28 for
introducing the electrolyte 32. The apertures 34 are closable for controlling
the
quantity of electrolyte 32 inside the chamber 22 and extracting the steam. The
chamber 22 is preferably sized such that a ratio of the volume of the
electrolyte
32 inside the chamber 22 to the volume of the cathode 40 inside the chamber is
between 3 to 15 and preferably between 6 to 10. This ratio may vary depending
on the electrolyte 32 used and the strength of a current energizing the
cathode
40 and anode 42.
The chamber 22 further includes a deflector 36 for urging the electrolyte 32
towards an electrode assembly 38 mounted inside the chamber 22, comprising
the cathode 40 and the anode 42, for ensuring continuous contact between the
electrolyte 32 and the electrode assembly 38. The term "deflector" is intended
to
refer to devices and arrangements that are designed to maintain continuous
contact between the electrolyte 32 and the electrode assembly 38 during the
plasma reaction. The deflector 36 is preferably made from non-conductive and
heat resistant material.
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The electrode assembly 38 includes the first electrode 50, having a
longitudinally extending spiral shape along a longitudinal axis 44, and the
second
electrode 52, having a flat spiral shape in a plane. The particular shape of
the
electrodes 50,52 considerably increases the life-span of the electrode
assembly
38. For example, where a conventional straight electrode may have a one (1)
second life-span, the electrodes 50,52 according to the illustrated embodiment
may have a life-span ranging from forty (40) to a hundred (100) hours.
Preferably, the first electrode 50 is the cathode 40 and the second electrode
52 is
the anode 42 during the plasma reaction. The electrode assembly 38 is
preferably made from high emissivity material.
In the illustrated embodiment shown in Figures 2, the first electrode 50 has a
length starting with a circular cross-section 46 at the beginning of the
length, i.e.
at the end closer to a connection to a power source, and an oval cross-section
48
at the end of the length.
As shown in Figure 1, the first electrode 50 is mounted inside the chamber 22
such that the longitudinal axis 44 is substantially parallel to the vertical
axis 24 of
the chamber. The second electrode 52 is mounted inside the chamber 22 at a
distance 118 relative to the first electrode 50 such that the plane is
substantially
perpendicular to the longitudinal axis 44. The distance 118 between the oval
cross-section 48 at the end of the length of the first electrode 50 and the
centre of
the second electrode 52 ranges from 10 mm to 150 mm, preferably, between
15.4 mm to 64.5 mm. The term "distance" is intended to refer to the shortest
distance between the first electrode 50 and the second electrode 52.
The electrode assembly 38 is energized with an electrical alternating current
provided by an electrical power source (not shown). The electrical power
source
produces an alternating input voltage 68 ranging from 200 V to 12 000 V,
preferably between 200 V to 600 V AC. An input voltage 68 below 200 V may
produce a week plasma arc and consequently affect the efficiency of the steam
generator 20.
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The electrode assembly 38 is connected to the power source using terminal
connections 56. The terminal connections 56 comprise an electrically
conductive
inner core 58 and an electrically non-conductive outer jacket 60. Preferably,
the
inner core 58 is made of copper while the outer jacket 60 is made of ceramic.
The alternating current (AC) is converted into a direct current (DC) before
supplying the electrode assembly 38. An electronic rectifier is used for
converting
the AC voltage into a DC voltage. The electronic rectifier is connected
between
the power source, for receiving the input voltage 68, and the terminal
connections
56 for providing a rectified voltage. The electronic rectifier includes a
controllable
switch for rectifying the input voltage and a monitoring-controller for
controlling
the controllable switch. The term "controllable switch" is intended to refer
to any
one or more, or a combination of any suitable electrically controllable switch
capable of converting alternating current to direct current, such as an
electromechanical switch, a transistor, a thyristor, a silicon-controlled
rectifier and
an insulated-gate bipolar transistor. The monitoring-controller monitors the
input
voltage 68 and activates the controllable switch upon sensing a substantially
zero
input voltage 68, thereby synchronizing the activation of the controllable
switch
with the input voltage 68. One of the main advantages of activating the
controllable switch when the input voltage 68 is substantially zero is
initiating a
gradual plasma arc current 70. As shown in Figures 4A and 4B, the gradual
initiation limits the inrush current 72 initiating the plasma arc. Limiting
the inrush
current 72 may reduce wear and tear of the electrode assembly 38 and smooth
the operation of the steam generator 20.
The steam generator 20 may also be used with two (2) or more electrode
assembly 38 for reducing wear and tear of the first electrode 50 and the
second
electrode 52. Moreover, a constant flow of steam can be achieved by
alternatively activating the electrode assemblies 38. In one embodiment, a
method 74 for producing a constant flow output of steam including multiple
electrode assemblies 38 in a steam generator 20 is used. The first step
consists
of monitoring 76 an input voltage 68, having alternating input waves, of an AC
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electrical power source in order to synchronize the input voltage 68 with the
activation of the controllable switch. This can be done using the monitoring-
controller. In a case of a polyphase system, the monitoring-controller can
also
detect the corresponding phase. The next step consists of rectifying 78 the
input
voltage 68 into a rectified voltage 120 for supplying the electrode assembly
38
with a direct current. A first electrode assembly 38 is supplied 80 with the
rectified
voltage 120 when the input voltage 68 is substantially zero and starting a
positive
half cycle input wave. After conducting the positive half cycle input wave,
the
rectified voltage 120 is cut 82 from the first electrode assembly 38, allowing
84
for a negative half cycle input wave to pass through the first electrode
assembly
38. The final step consists of conducting 86 the rectified voltage 120 to a
second
electrode assembly when the input voltage 68 is substantially zero and
starting a
subsequent positive half cycle input wave. The steps are then repeated in an
alternating fashion between the electrode assemblies used in the steam
generator. For example, a steam generator with three electrode assemblies A, B
and C, will alternate in the following fashion: A-B-C-A-B-C etc.
In another embodiment, the steam generator 20 can also be integrated to a
system 88 for generating a constant flow of steam. As shown in Figure 5, the
system comprises a reservoir 90 receiving a plurality of steam generators 20.
The reservoir 90 may be made from conductive materials. Preferably, the
reservoir 90 is made from a non-corrosive material such as stainless steel.
The
electrolyte 32 is placed in the reservoir 90 for feeding the steam generators
20.
The system 88 also includes level probes 92 monitoring the electrolyte 32
quantity in the reservoir 90, the steam generators 20, etc. The system 88
preheats the electrolyte 32, preferably between 80 and 90 degrees Celsius,
before feeding it to the steam generators 20. A temperature probe 94 and
heating
elements 96 are used to control the temperature of the electrolyte 32 before
feeding the steam generators 20. The system 88 may also include a pressure
valve 98 and a pressure probe 100 to limit the pressure inside the system 88.
The reservoir 90 further includes a drainage valve 102 for emptying the
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electrolyte 32 allowing for maintenance and the like. The output of the steam
generators 20 is connected to a vapor separator 106 allowing non-saturated
steam to exist from the system 88 through a vapor output 104. Water is
supplied
to the system 88 through a water valve 108. The water valve 108 can be
connected to a municipal water supply networks for providing the system 88
with
water. An electrolyte tank 110 supplies the system 88, through a dosing pump
114, with a suitable electrolyte substance for mixing it with water and
producing
the electrolyte 32. A conductivity probe 112 is used to monitor the
concentration
of the electrolyte 32. The concentration is varied by controlling the quantity
of
water and/or electrolyte into the system 88. Finally, a flow switch 116 and a
flow
meter may also be included in the system 88 to monitor the proper functioning
of
electrolyte 32 circulation. The above described system 88 allows the
continuous
generation of steam.
Of course, numerous modifications could be made to the above-described
embodiments without departing from the scope of the invention, as defined in
the
appended claims.
