This invention relates generally to the field of maintenance and operation of heat exchangers. Our interest is more particularly in the removal of foulants from operating heat exchangers.
Fouling of heat exchangers is an issue that occurs in all types of heat exchange processes. The cost of cleaning includes operational time lost, actual cleaning time, and replacement of equipment beyond cleaning. Cleaning techniques rely on the heat exchangers being shut down, drained, and dismantled. Effective cleaning of heat exchangers by non-chemical means or during operations are not available presently.
Cavitation is a phenomenon in industrial fluid flows that is normally avoided. Cavitation often causes surface destruction of pipes, impellers, and other equipment. Designs of equipment focus on removing any potential cavitation from the equipment. No foulant removal system for use on operating equipment currently employs cavitation.
New methods for removing fouling from heat exchangers, especially during operations, are needed.
United States patent publication number 20080073063 to Clavenna et al. teaches a method for reducing fouling and the formation of deposits on the inner walls of direct-contact heat exchangers. The method is comprised of applying fluid pressure pulsations to the liquids within tubes of the heat exchanger with vibrations to the heat exchanger to affect a reduction of the viscous boundary layer. Reduction of the viscous boundary layer reduces the incidence of fouling as well as promotes heat transfer from the tube wall to the liquid within the tubes. The method is also comprised of the use of a coating on the inner wall surfaces of exchanger tubes to further reduce fouling and corrosion. The present disclosure differs from this in that the exchanger can be operating, does not require fluid pressure pulsations, and does not require any special surface materials. This disclosure is pertinent and may benefit from the methods disclosed herein and is hereby incorporated for reference in its entirety for all that it teaches.
U.S. Pat. No. 4,120,699 to Kennedy et al. teaches a method for acoustical cleaning comprising immersing the equipment in a liquid and propagating opposing acoustic wave trains to produce directed cavitation. The present disclosure differs from this in that the exchanger can be operating and does not require immersion in a separate fluid bath. This disclosure is pertinent and may benefit from the methods disclosed herein and is hereby incorporated for reference in its entirety for all that it teaches.
United States patent publication number 20116290778 to Zugibe teaches a method for sonic cleaning of a heat exchanger comprising insertion of an ultrasonic transducer and a liquid medium within the shell of the heat exchanger. The ultrasonic transducer is excited, to produce acoustic waves within the liquid. The present disclosure differs from this in that the exchanger can be operating, requiring no shut down or special fluids. This disclosure is pertinent and may benefit from the methods disclosed herein and is hereby incorporated for reference in its entirety for all that it teaches.
U.S. Pat. No. 9,032,792 to Bradley et al. teaches a fouling reduction device and method. An ultrasound emitter is used to reduce fouling on a sensor in a liquid. The present disclosure differs from this in that the fouling is not reduced, but actually removed. This disclosure is pertinent and may benefit from the methods disclosed herein and is hereby incorporated for reference in its entirety for all that it teaches.
U.S. Pat. No. 8,628,660 to Foret teaches treatment of fluids with wave energy from a carbon arc. The carbon arc is applied to a hydrocyclone or other vortex and used to cavitate the bulk fluid and destroy biological and other materials. The present disclosure differs from this in that the cavitation occurs on the surface, not in the bulk flow, and does not require a vortex or thin film layers. This disclosure is pertinent and may benefit from the methods disclosed herein and is hereby incorporated for reference in its entirety for all that it teaches.
A method for removing a surface foulant is disclosed. An operating heat exchanger is provided, with a process side operating at an operating pressure. A carrier liquid that contains potential fouling agents is provided to the process side of the operating heat exchanger, wherein at least a portion of the potential fouling agents foul at least a portion of an internal wall of the process side of the operating heat exchanger. The process side of the heat exchanger is operated such that the carrier liquid is at a vapor pressure equal to the operating pressure. A cavitation inducing device or cavitation inducing devices are provided to the process side of the operating heat exchanger. A condition indicating fouling is detected. The cavitation inducing device or devices, operating on a portion or portions of the process side of the operating heat exchanger, induce a localized pressure change, vaporizing a portion of the carrier liquid and forming a transient bubble or bubbles which collapse by cavitation, producing a localized shockwave, a re-entrant microjet, and extreme transient pressures and temperatures. These steps are repeated as necessary to remove the surface foulant. In this manner, the surface foulant is removed from the operating heat exchanger.
The process side of the operating heat exchanger may be equipped with pressure sensors, temperature sensors, or a combination thereof. The pressure and temperature sensors may be located at an inlet and an outlet of the process side of the operating heat exchanger.
The condition indicating fouling may be determined by a change of pressure through the operating heat exchanger, indicated by the pressure sensor or pressure sensors, a change of temperature, indicated by the temperature sensor or temperature sensors, or a combination thereof.
The carrier liquid may comprise water, brine, hydrocarbons, liquid ammonia, liquid carbon dioxide, or combinations thereof. The potential fouling agents may comprise solid particles, miscible liquids, dissolved salts, a fouling gas that may desublimate onto the surface of the heat exchanger, reaction products, or combinations thereof. The fouling gas may comprise carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, hydrocarbons with a freezing point above 0 C, or combinations thereof.
The cavitation inducing device or cavitation inducing devices may comprise a piezoelectric actuator, ultrasound emitter, carbon-arc cavitation inducer, voice coil, linear resonant actuator, shaker, exciter, hydraulic actuator, solenoid actuator, blunt object, manual shaking, or a combination thereof. The cavitation inducing device or cavitation inducing devices may be sealed to prevent a liquid from damaging the cavitation inducing device.
The operating heat exchanger may be equipped with a cavitation detecting device or devices. The cavitation detecting device or devices may comprise hydrophones, passive cavitation detectors, piezoelectric polymer-coated impedance-matched acoustical absorbers, vibration sensors, microphones, pressure sensors, ceramic capacitive measuring cells, photolitographed-micropattern cavitation detectors, two electrodes isolated from each other by an insulative surface, high intensity focused ultrasound transducers with a modular cavitation element, or combinations thereof.
The cavitation inducing device or cavitation inducing devices may be controlled by a control loop that monitors the condition indicating fouling and actuates the cavitation inducing device or cavitation inducing devices automatically. The condition indicating fouling may be detected by an operator, at which point the operator may manually actuate the cavitation inducing device or cavitation inducing devices. The operator may directly use the cavitation inducing device or cavitation inducing devices on the operating heat exchanger.
The heat exchanger may comprise a brazed plate, aluminum plate, shell and tube, plate, plate and frame, plate and shell, spiral, or plate fin style heat exchanger. Any surface of the process side of the heat exchanger exposed to the carrier liquid may comprise a material that inhibits adsorption of gases, prevents deposition of solids, or a combination thereof. The material may comprise aluminum, stainless steel, polymers, carbon steel, ceramics, polytetrafluoroethylene, polychlorotrifluoroethylene, natural diamond, man-made diamond, chemical-vapor deposition diamond, polycrystalline diamond, or combinations thereof.
In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through use of the accompanying drawings, in which:
It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of certain examples of presently contemplated embodiments in accordance with the invention.
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In some embodiments, process side 104, 204, 304, and 404 are equipped with a pressure sensor or pressure sensors, a temperature sensor or temperature sensors, or a combination thereof. In some embodiments, these sensors are located on the inlets and outlets of the process side 104, 204, 304, and 404. In other embodiments, these sensors are located at a plurality of locations on process side 104, 204, 304, and 404.
In some embodiments, the condition indicating fouling is determined by a change of pressure through process side 104, 204, 304, and 404, as indicated by the pressure sensor or pressure sensors. In some embodiments, the condition indicating fouling is determined by a change of temperature through process side 104, 204, 304, and 404, indicated by the temperature sensor or temperature sensors. In some embodiments, the condition indicating fouling is determined by both a change of pressure and a change of temperature through process side 104, 204, 304, and 404, as indicated by the pressure sensor or pressure sensors and the temperature sensor or temperature sensors.
In some embodiments, the carrier liquid comprises water, brine, hydrocarbons, liquid ammonia, liquid carbon dioxide, or combinations thereof. In some embodiments, the potential fouling agents comprise solid particles, miscible liquids, dissolved salts, a fouling gas that may desublimate onto the surface of the heat exchanger, reaction products, or combinations thereof. The fouling gas comprises carbon dioxide, nitrogen oxide, sulfur dioxide, nitrogen dioxide, sulfur trioxide, hydrogen sulfide, hydrogen cyanide, water, hydrocarbons with a freezing point above 0 C, or combinations thereof.
In some embodiments, the cavitation inducing device or cavitation inducing devices comprise a piezoelectric actuator, ultrasound emitter, carbon-arc cavitation inducer, voice coil, linear resonant actuator, shaker, exciter, hydraulic actuator, solenoid actuator, blunt object, manual shaking, or a combination thereof. In some embodiments, the cavitation inducing device or cavitation inducing devices are sealed to prevent a liquid from damaging the cavitation inducing device.
In some embodiments, the operating heat exchanger may be equipped with a cavitation detecting device, which can be used to provide feedback to a control loop to verify the system is operating correctly. In some embodiments, the cavitation detecting device or devices may comprise hydrophones, passive cavitation detectors, piezoelectric polymer-coated impedance-matched acoustical absorbers, vibration sensors, microphones, pressure sensors, ceramic capacitive measuring cells, photolitographed-micropattern cavitation detectors, two electrodes isolated from each other by an insulative surface, high intensity focused ultrasound transducers with a modular cavitation element, or combinations thereof.
In some embodiments, the cavitation inducing device or cavitation inducing devices are controlled by a control loop that monitors the condition indicating fouling and actuates the cavitation inducing device or cavitation inducing devices automatically.
In some embodiments, the condition indicating fouling is detected by an operator, at which point the operator manually actuates the cavitation inducing device or cavitation inducing devices.
In some embodiments, the condition indicating fouling is detected by an operator, at which point the operator manually uses the cavitation inducing device or cavitation inducing devices on the operating heat exchanger. In one embodiment, the operator induces cavitations by striking the heat exchanger.
In some embodiments, the heat exchanger comprises a brazed plate, aluminum plate, shell and tube, plate, plate and frame, plate and shell, spiral, or plate fin style heat exchanger. In some embodiments, any surface of the process side of the heat exchanger exposed to the carrier liquid comprises a material that inhibits adsorption of gases, prevents deposition of solids, or a combination thereof. In some embodiments, the material comprises aluminum, stainless steel, polymers, carbon steel, ceramics, polytetrafluoroethylene, polychlorotrifluoroethylene, natural diamond, man-made diamond, chemical-vapor deposition diamond, polycrystalline diamond, or combinations thereof.
This invention was made with government support under DE-FE0028697 awarded by The Department of Energy. The government has certain rights in the invention.