Patent ID: 12246284

While the present disclosure is susceptible to various modifications and alternative forms, specific implementations and implementations have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.

DETAILED DESCRIPTION

While this invention is susceptible of implementation in many different forms, there is shown in the drawings and will herein be described in detail preferred implementations of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the implementations illustrated. For purposes of the present detailed description, the singular includes the plural and vice versa (unless specifically disclaimed); the words “and” and “or” shall be both conjunctive and disjunctive; the word “all” means “any and all”; the word “any” means “any and all”; and the word “including” means “including without limitation.” Additionally, the singular terms “a,” “an,” and “the” include plural referents unless context clearly indicates otherwise.

Large merchant shipping vessels (such as general cargo vessels, container ships, tankers, dry bulk carriers; multi-purpose vessels, refer ships, etc.) operate using way of diesel engines that emit large amounts of exhaust gas. The exhaust gas emissions of these diesel engines can include nitrogen-based NOxcompounds such as nitric oxide (NO), nitrogen dioxide (NO2), and other compounds. These NOxcompounds are considered to be pollutants; and can be harmful to the environment. In order to reduce the harmful emissions from these diesel engines, the exhaust gas of the diesel engines can be remediated to reduce and/or remove the amount of NOxcompounds in the exhaust gas.

FIG.1shows a system100for exhaust gas remediation that includes a high voltage source108and a plasma reactor110. During operation, the plasma reactor110is fluidly coupled to the output of an engine102via a valve111. The valve111is operable to control the amount of exhaust gas emitted by engine102that is directed to an input port112of the plasma reactor110. Any gas and/or substances emitted by the plasma reactor can be emitted at output port114. Exhaust gas not directed to the engine102can be sent to an exhaust port104. In some implementations, the exhaust gas of the engine102includes NOxmolecules. In some implementations; the engine102is a diesel engine; and the exhaust gas is diesel exhaust. For example, the engine102can be the diesel engine of a large merchant shipping vessel. However, the engine102can be other types of diesel engines as well, as such as the diesel engines of smaller ships, trucks, sport utility vehicles (SUVs), submarines, trains; or any other type of vehicle that may include a diesel engine, in still other implementations, the engine102is a diesel engine of equipment such as a crane, a bulldozer, an excavator, etc. The engine102can also be a diesel engine of an electric power plant, or a diesel engine from any other source. In further implementations, the engine102is a non-diesel engine.

The plasma reactor110is generally formed from at least one reactor tube that defines an internal chamber116(seeFIG.5B). The internal chamber116is fluidly connected to the engine102through the input port112, such that the exhaust gas can flow through the reactor tube. Electrodes are disposed within the internal chamber116of the reactor tube. The electrodes are electrically coupled to the high voltage source108. The high voltage source108delivers electrical pulses to the electrodes when the internal chamber116contains the exhaust gas from the engine102, to form a plasma from the exhaust gas. The electrical pulses and the resulting formation of the plasma removes at least a portion of the NO molecules and at least a portion of the NO molecules from the exhaust gas, thereby at least partially remediating the exhaust gas.

In some implementations, additional components can be added to system100in order to test the plasma reactor110. These components can include a gas analyzer105, an oscilloscope107, and one or more sensors109. The gas analyzer105can be used to analyze the gas emitted from the output port114of the plasma reactor110. The sensors109can be coupled to the high voltage source108, and are used to measure the voltage and current of the pulses being fed into the plasma reactor110. The sensors109are used to measure the derivatives of the electrical field and magnetic field of these pulses. The outputs of the sensors109are sent to integrators coupled to the oscilloscope107to obtain oscilloscope waveforms, which are numerically reconstructed to form the actual voltage and current waveforms. The oscilloscope107can be housed in an electromagnetically compatible (EMC) cabinet, or another suitable enclosure, to protect the oscilloscope from any electromagnetic interference from the plasma reactor. In some implementations, some or all components of system100are grounded to aid in reducing electromagnetic interference issues.

In some implementations, one of the sensors109measures only the electric field D, and is positioned near a cable connecting the high voltage source108and the plasma reactor110. The sensor can be formed from a metal plate placed adjacent to the cable, such that a capacitance CDis formed. The voltage of the pulses from the high voltage source108are thus given by:

VD=Zcable⁢CD⁢d⁢VHVd⁢t,
where Zcableis the impedance of the cable (for example, 50 ohms), VHVis the voltage waveform that is reconstructed, and VDis the output of the electric field sensor109.

In some implementations, one of the sensors109measures only the electric field B, and is positioned near the cable connecting the high voltage source108and the plasma reactor110. The sensor can be formed from a single metal loop placed adjacent to the cable. The magnetic field generated by current in the cable couples into the metal loop via a mutual inductance MBbetween the metal loop and the cable. The resulting change in magnetic flux in the metal loop induces a voltage across the loop, given by:

VB=MB⁢d⁢⁢IHWd⁢⁢t,
where IHVis the current waveform that is reconstructed, and VB, is the output of the magnetic field sensor109.

The full numerical reconstruction of the voltage and current waveforms is given by:

VHV=1CD⁢R2⁡[R1⁢C1⁢VD,int+(1+R1Z0)⁢∫VD,int⁢d⁢⁢t],andIHV=1MB⁡[R1⁢C1⁢VB,int⁢+(1+R1Z0)⁢∫VB,int⁢d⁢⁢t],
where Z0is the input impedance of the oscilloscope107, and both CDand MBare predetermined calibration values. The final integration term is a correction term for the impedance of the oscilloscope107.

FIG.2illustrates various implementations and configurations of the electrodes, which can be solid extruded electrodes, or can be formed from a number of wires. The wire-based electrodes can be 1-wire electrodes, 2-wire electrodes 3-wire electrodes, 4-wire electrodes, 5-wire electrodes, 6-wire electrodes, or any other number of wires. The electrodes can include two different types of electrodes. Moreover, the plasma reactor110may include one electrode, or three or more electrodes. Shown inFIG.2are a 3-wire electrode118A, a 4-wire electrode118B, and an extruded electrode118C. The multiple wire-based electrodes (such as 3-wire electrode118A and 4-wire electrode118B) can have a cross-section that is generally defined as the diameter of a circle connecting all of the wires of the electrode, as shown. The cross-section of the extruded electrode1180has a central portion120, and four arms122A-122D. The cross-section of the extruded electrode118C is defined as the distance between the ends of two opposing arms, such as arms122A and122B, or arms122C and122D. In some implementations, the 3-wire electrode118A and the 4-wire electrode118B have cross-sections of about 2.0 inches, about 2.25 inches, or about 2.5 inches. In other implementations, the 3-wire electrode118A and the 4-wire electrode118B have cross-sections of between about 1.0 inches and about 5.0 inches. Other electrode types and configurations are also contemplated. For example, the extruded electrode118C could have more or less than the four arms122A-122D, and could also have a different shape entirely. In other implementations, the cross-section of the electrodes can be between about 0.4 inches and about 1.1 inches. Further, the electrodes can have an impedance of between about 70 ohms and about 300 ohms.

FIG.3Aillustrates a perspective view of one implementation of the plasma reactor110, whileFIG.3Billustrates a top plan view of one implementation of the plasma reactor110. In this implementation, the plasma reactor includes a first pair of reactor tubes124A and124B, a second pair of reactor tubes126A and126B, a third pair of reactor tubes128A and128B, and a fourth pair of reactor tubes130A and130B. Each reactor tube124A-130B defines a hollow internal chamber (such as hollow internal chamber116shown inFIG.5B) in which an electrode can be disposed. The plasma reactor110inFIGS.3A and3Balso include four high voltage connectors132A-132D.

High voltage connector132A is coupled to the electrodes positioned inside the first pair of reactor tubes124A,124B. High voltage connector13213is coupled to the electrodes positioned inside the second pair of reactor tubes126A,126B. High voltage connector1320is coupled to the electrodes positioned inside the third pair of reactor tubes128A,128B. High voltage connector132D is coupled to the electrodes positioned inside the fourth pair of reactor tubes130A,130B. The high voltage connectors132A-132D deliver electrical pulses from the high voltage source108to the electrodes positioned inside the reactor tubes124A-130B. The input port112and the output port114are positioned at opposite ends of the reactor tubes124A-130B, and are both fluidly coupled to the internal chambers of all of the reactor tubes1284-130B, so that the exhaust gas from the engine102can flow through the plasma reactor. In some implementations, each high voltage connector132A-132D is coupled to the same high voltage source108. In other implementations, each high voltage connector132A-132D is coupled to its own respective high voltage source108.

FIG.4Ashows a top plan view of a pair of reactor tubes134A and134B. The input port112is coupled to one end of both reactor tubes134A,134B. The output port is coupled to the other end of both reactor tubes134A,134B. A single high voltage connector136is coupled to both the first reactor tube134A and the second reactor tube134B. The reactor tubes134A and1:34B may be the same as or similar to reactor tubes124A-130B. The high voltage connector136may be the same as or similar to high voltage connectors132A-132D. The high voltage connector136generally extends between the reactor tubes134A,134B in a direction that is perpendicular to the direction along which the reactor tubes134A,134B extend.

In some implementations, the pair of reactor tubes134A,134B and the high voltage connector136form an individual plasma reactor110on their own. In other implementations, the pair of reactor tubes134A,134B and the high voltage connector136are components of a larger plasma reactor110, such as the plasma reactor110illustrated inFIGS.3A and3B. The high voltage connector136includes a housing137and a cable138extending from the housing137. A distal end of the cable138electrically connects to the high voltage source108, while the proximal end of the cable extends into the housing137of the high voltage connector136.

FIG.4Bshows a cross-section of one end of the plasma reactor110ofFIG.4A, showing the inside of the reactor tubes134A,134B, and the inside of the high voltage connector136. The high voltage connector136includes two insulating members142A,142B extending from the housing137. A first portion of each insulating member142A,142B is disposed within the housing137. A second portion of insulating member142A extends from the housing137and is positioned inside the internal chamber of reactor tube134A, while the second portion of insulating member142B extends from the housing137and is positioned inside the internal chamber of reactor tube134B. The first portion of each insulating member142A,142B has a generally cylindrical shape. The second portion of each insulating member142A,142B is generally cone-shaped, and tapers down to the end that is disposed in the respective reactor tube134A,134B.

The cable138extends into the housing137, where it is electrically connected to into two separate electrically conductive members140A,140B. Electrically conductive member140A extends through the interior of the insulating member142A to the tapered end disposed in reactor tube134A. Electrically conductive member140B extends through the interior of the insulating member142B to the tapered end disposed in reactor tube134B. Thus, the electrically conductive members140A,140B generally extend perpendicular to the length of the reactor tubes134A,134B.

An electrode144A is coupled to electrically conductive member140A, and extends along the length of the internal chamber of reactor tube134A. Similarly, an electrode144B is coupled to electrically conductive member140B, and extends along the length of the internal chamber of reactor tube134B. Electrode144A is formed from wires145A,145B, and145C. Electrode144B is formed from wires145D,145E, and145F. Spacers146A,146B may be coupled to electrodes144A,144B, respectively. Spacers146A,146B aid in maintaining the position of the electrodes144A,144B within the internal chambers of the respective reactor tubes134A,134B, and prevent the electrodes144A,144B from contacting the interior surface of the reactor tubes134A,134B. Electrodes144A and144B can be 3-wire electrodes (such as electrode118A), 4-wire electrodes (such as118B), extruded electrodes (such as electrode118C), or any other suitable type or shape of electrode. When the electrodes are multi-wire electrodes, the spacers146A,146B also aid in maintaining separation of the wires. In some implementations, the spacers146A,146B are made of an electrically insulating material, such as fiberglass.

The arrangement of the high voltage connector136and the electrodes144A,144B can be used for any implementation of the plasma reactor110. For example, the plasma reactor110can include the four pairs of reactor tubes124A-130B as shown inFIGS.4A and4B. The plasma reactor110could also include a single reactor tube coupled to the input port112and the output port114, a single pair of reactor tubes coupled to the input port112and the output port114, or any number of reactor tubes coupled to any number of input ports112and any number of output ports114.

FIG.5Ashows a perspective view of the high voltage connector136without the cable138attached. In some implementations, the housing137includes one or more ports139A,13913,139C that are open to the interior of the housing. Ports139A,13913, and139C can be used to allow coolant or other fluids to circulate within the housing137, in order to cool the high voltage connector136and maintain the high voltage connector136at a desired temperature. In some implementations, the coolant is oil. In some implementations, the electrically conductive members140A,140B extend out of their respective insulating members142A,142B parallel to the length of the reactor tubes134A,134B. Thus, the electrically conductive members140A,140B can have a right-angled shape, e.g., an “L” shape.

FIG.5Bshows an end view of reactor tube134A with an end cap removed, such that the internal chamber116is visible. As shown, the electrode144A extends away from the insulating member142A toward the opposite end of the internal chamber116. In the implementation shown inFIG.5B, electrode144A is a 3-wire electrode formed from wires145A,146B,145C, and spacer146A aids in maintaining separation of the three wires145A,145B,145C.

FIG.5Cshows the high voltage connector136from the opposite side as compared toFIG.5B. In the implementation illustrated inFIG.5C, the spacers146A,146B have large circular shapes, with an outer diameter generally equal to an inner diameter of the reactor tubes134A,134B. These types of spacers146A,146B are generally used with extruded electrodes118C.

FIGS.6A,6B, and6Call show an extruded electrode118C with a spacer147(which can be the same as or similar to any of the spacers146discussed herein). As shown, extruded electrode118C is formed from four arms122A-122D extending from a central portion120. The extruded electrode118C is mounted to an electrically conductive member141(which can be the same as or similar to electrically conductive members140A,140B). The electrically conductive member141extends through the center of the spacer147, and is used to conduct pulses from the high voltage source108to the electrode118C.

FIG.7shows a bypass network150that can be electrically coupled in parallel with the cable138of the high voltage connector136. During use, the plasma reactor110can generate large amounts of electromagnetic interference (EMI) due to the operation of the high voltage source108. In certain situations, a large amount of electrical energy can be reflected back to the high voltage source108, such as when the connection to one of the electrodes144A,144B is short-circuited, or when the high voltage source108and the plasma reactor110are impedance mismatched. The reflected energy can be absorbed by the output of the high voltage source108(which could be, for example, a diode stack). To avoid this issue, the bypass network150can be electrically connected in parallel with the output of the high voltage source108and the high voltage connector136. The bypass network150can act as a sink and absorb any reflected electrical energy. In the illustrated implementation, the bypass network150is one or more capacitors electrically connected in series. Other types of bypass networks150can also be utilized.

During operation, system100has a total system efficiency defined as ηsystem=ηsource×ηreactor×ηplasma. ηsourceis the electrical efficiency at which electrical energy is taken from the electricity grid (or other ultimate source of electrical energy) by the high voltage source108and converted into short pulses. ηreactoris the electrical efficiency at which the energy of the pulses is dissipated by the plasma formed in the plasma reactor110, and can be defined as

ηsource=EplasmaEpulse,
where Eplasmais the energy dissipated by the plasma, and Epulse, is the total available energy in the pulse. ηplasmais the chemical efficiency of the plasma, and is a measure of the amount of energy used by the plasma that is converted into chemically active species. The total system efficiency ηsystemis the product of all three efficiencies.

The reactor efficiency ηreactoris influenced by the electric field strength in the plasma reactor110, and the impedance matching of the plasma reactor110. The impedance matching of the plasma reactor110determines how much of the pulse from the high voltage source108enters the plasma reactor110. In a perfectly matched system, the impedance of the cable138delivering the pulses matches the impedance of the plasma reactor110, and the entire pulse enters the plasma reactor110. When there is some amount of mismatch in the impedance, the pulse partially reflects off the plasma reactor110, which can lead to a loss of energy and high voltage stress on the system. In some implementations of system100, the cable138has an impedance of about 50 ohms, and each of the electrically conductive members140A,140B connected to the high voltage source108through the cable138have an impedance of about 100 ohms. In these implementations, a single high voltage source108is used to generate pulses for each pair of electrodes.

The reflectiveness of the system100is given by

R=Zreactor-ZcableZreactor+Zcable,
where Zcableis the impedance of the cable138and Zreactoris the impedance of the plasma reactor110. For a perfectly matched system R=0, and there is no reflection. For a mismatched system however, there is some degree of reflection. The maximum voltage stress Vmaxof the system100is the sum of the incoming pulse voltage and the reflected pulse voltage, and is generally given by Vmax=(1+R)Vpeak, where Vpeakis the applied peak voltage.

The effectiveness of the system100at removing NO molecules and NOxmolecules is measured by comparing the initial and final concentrations of NO and NOx. This is measured as:

NOremediation=100⁢%⁢×NOinitial-NOfinalNOinitialNOx,remediation=100⁢%⁢×NOx,initial-NOx,finalNOx,initial

The NO removal efficiency of the system100is defined as how efficient the formed plasma removes NO and is measured in mol/kWh. The NO removal efficiency is measured by the following equation:

NOrem,eff=Δ⁢⁢NO×3.6Vm⁢ϵ,

ΔNO is the removed concentration of NO (in ppm), Vmis the molar volume (in L/mol, dependent on temperature) and c is the energy density (in J/L). The energy density is given by:

ϵ=frr⁢Eplasma×60F.

Here, frris the pulse repetition rate (in Hz), Eplasmais the dissipated energy in the plasma per pulse, and F is the gas flow rate (in L/min).

The overall efficiency of the system100is given by the following equation:
System efficiency=Reactor efficiency×NOrem,eff

The system100is operated according to a variety of settings, including engine loading, engine speed, pulse source voltage, pulse source repetition rate, flow through the plasma reactor110, and electrode type and geometry. The engine speed can be between about 400 rpm and about 1,000 rpm, between about 1,000 rpm and about 1,800 rpm, between about 400 rpm and about 1,800 rpm, about 400 rpm, about 1,000 rpm, or about 1,800 rpm. The pulse source voltage can be about 250 volts, about 300 volts, about 325 volts, about 350 volts, or between about 250 volts and about 350 volts. The pulse source repetition rate can be about 100 Hz, about 500 Hz, about 1000 Hz, about 1,500 Hz, about 2,500 Hz, or generally any range between any two of these values. In some implementations, the average electrical reactor efficiency (e.g., ηreactor), can be between about 70% and about 90%, between about 78% and about 86%, between about 80% and about 90%,

While the present invention has been described with reference to one or more particular implementations, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention. Each of these implementations and obvious variations thereof is contemplated as falling within the spirit and scope of the invention. It is also contemplated that additional implementations according to aspects of the present invention may combine any number of features from any of the implementations described herein.