Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
  • G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
  • G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
  • G01F23/265—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors for discrete levels
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B15/00—Operating or servicing cells
  • C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
  • C25B15/081—Supplying products to non-electrochemical reactors that are combined with the electrochemical cell, e.g. Sabatier reactor
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/0007—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm for discrete indicating and measuring
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
  • G01F23/26—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields
  • G01F23/263—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors
  • G01F23/268—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields by measuring variations in capacitance of capacitors mounting arrangements of probes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
  • G01F23/80—Arrangements for signal processing
  • G01F23/802—Particular electronic circuits for digital processing equipment
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
  • G05D9/00—Level control, e.g. controlling quantity of material stored in vessel
  • G05D9/04—Level control, e.g. controlling quantity of material stored in vessel with auxiliary non-electric power

Definitions

• the subject matter disclosed herein relates to an apparatus and method for detecting a liquid level in an electrolytic cell.
• Low or high liquid levels in electrolytic cells may result from non-equilibrium conditions present during shut-down and start-up, as well as from problematic cells having "fast running" diaphragms.
• a low liquid level in an electrolytic cell coupled with a failure to detect the low liquid level in a timely manner, can result in a potentially hazardous situation.
• the electrolytic process is the chlor-alkali process
• the electrolytic cell is a diaphragm cell
• a decrease in the liquid level below the low-low liquid level can result in exposure of the tops of the cathodes to the head space gases of the electrolytic cell, which comprise chlorine gas.
• Liquid level can be measured in opaque electrolytic cells using a level gauge.
• the simplest and most reliable level gauge is a liquid sight monitor, also known as a direct reading level gauge, or sight glass.
• the electrolytic cells can be inspected by an operator at approximately 30-minute intervals. However, this inspection interval may be insufficient to catch "fast running" cells, in which the liquid level can decrease to a dangerously low level in less than 30 minutes.
• liquid level sensors in current use can be unreliable or lack cost-effectiveness under the operating conditions of electrolytic cells. It is therefore desirable to have an apparatus and method for detecting a liquid level in an electrolytic cell with improved reliability, particularly under severe operating conditions such as high magnetic fields and corrosive atmospheres. It would be a further advantage if installation does not require modification of existing electrolytic cells. It would be a still further advantage if the apparatus and methods are cost-effective.
• An embodiment is an apparatus for detecting a liquid level in an electrolytic cell, the apparatus comprising a level tube in fluid contact with the electrolytic cell; a proximity sensor positioned to detect the presence or absence of liquid at a predetermined level in the level tube; and a control system responsive to the proximity sensor, wherein the control system is in communication with the liquid level sensor via a communication system.
• Another embodiment is an apparatus for detecting a brine level in a chlor- alkali electrolytic cell, the apparatus comprising a level tube in fluid contact with the chlor- alkali electrolytic cell; a capacitive proximity sensor adjustably mounted on the level tube to detect the presence or absence of brine at a predetermined position on the level tube; a support for positioning and mounting the capacitive proximity sensor on the level tube; and a digital control system responsive to the capacitive proximity sensor, wherein the digital control system is in communication with the capacitive proximity sensor.
• Another embodiment is a method for maintaining a target liquid level in an electrolytic cell, the method comprising providing an apparatus comprising a level tube in fluid contact with an electrolytic cell, a proximity sensor positioned on the level tube at a target liquid level to detect the presence or absence of a liquid, and a control system responsive to the proximity sensor, wherein the control system is in communication with the proximity sensor via a communication system, and indicates the presence or absence of the liquid at the target liquid level on the level tube in response to a signal from the proximity sensor; and adjusting the liquid level in the electrolytic cell to the target liquid level in response to the signal.
• Another embodiment is a method for maintaining a target brine level in a chlor-alkali electrolytic cell, the method comprising providing an apparatus comprising a level tube in fluid contact with the chlor-alkali electrolytic cell, a capacitive proximity sensor adjustably mounted on the level tube to detect the presence or absence of brine at the target brine level on the level tube, a support for positioning and mounting the capacitive proximity sensor on the level tube, and a digital control system responsive to the capacitive proximity sensor, wherein the digital control system is in communication with the capacitive proximity sensor and indicates the presence or absence of the brine at the target brine level on the level tube in response to a signal from the capacitive proximity sensor; and adjusting the brine level in the chlor-alkali electrolytic cell to the target brine level in response to the signal.
• the Figure is a schematic diagram of an apparatus for detecting liquid level in an electrolytic cell comprising a level tube in fluid contact with the electrolytic cell and a proximity sensor.
• a level tube is placed in fluid contact with the electrolytic cell to detect the level of the liquid in the cell.
• the level tube is fitted with a proximity sensor positioned to detect the presence or absence of liquid at a predetermined level in the level tube.
• a communication system links the proximity sensor to a control system responsive to the proximity sensor. The control system can be used to alert the operator when the fluid level of the electrochemical cell is not within the desired range, or to perform other actions
• a method for detecting a high or low liquid level in an electrolytic cell comprises use of an apparatus comprising a level tube in fluid contact with an electrolytic cell, a proximity sensor positioned on the level tube to detect the presence or absence of liquid, and a control system responsive to the proximity sensor, wherein the control system is in communication with the proximity sensor via a communication system; and wherein the proximity sensor detects the presence or absence of fluid in the level tube and sends a signal to the control system via the communication system.
• the control system can then provide an indication of liquid level in response to the signal from the proximity sensor.
• the liquid level in the electrolytic cell is adjusted to the target level in response to the signal from the proximity sensor to the control system.
• the apparatus and methods are reliable under severe operating conditions such as high magnetic fields and corrosive environments. Moreover the apparatus and methods do not require modification of existing electrolytic cells, are cost- effective, and do not require process down-time or large capital investment to implement.
• the Figure is a schematic diagram of an apparatus 1 for detecting liquid level (the position of the liquid-gas interface) in an electrolytic cell 11 comprising a level tube in fluid contact with a liquid contained in the electrolytic cell 1 1 and a proximity sensor 3.
• electrolytic cell 11 contains liquid 12 exhibiting a liquid level 8 in electrolytic cell 1 1.
• Liquid 12 can be any liquid in the cell. In an embodiment, it is an electrolyte, for example a solution of water in which ions are dissolved. In an embodiment, the liquid is a solution of sodium chloride in water (brine).
• the liquid level 8 in the cell can vary depending upon process conditions. The liquid level can be adjusted, for example by increasing or decreasing the flow of liquid into or out of the electrolytic cell.
• Level tube 2 (also known as a direct reading level gauge, or sight glass) is in fluid contact with the liquid 12 in the electrolytic cell so that the liquid level 8 in the level tube 2 is representative of the liquid level 8 in the electrolytic cell.
• Proximity sensor 3 is positioned adjacent the level tube 2 so as to detect liquid level 8 in the level tube.
• Measurement zone 5 represents the area in which the proximity sensor detects the presence or absence of liquid.
• the proximity sensor can be imbedded in or attached to a support 7 as shown in the Figure, which is held in place by a clamp, or an elastomeric O-ring 6 as shown in the Figure.
• the position of the proximity sensor is fixed, for example by an adhesive.
• the position of the proximity sensor is adjustable along the vertical axis of the level tube.
• Liquid level 9 represents a low liquid level
• liquid level 10 represents for example a critical liquid level, at which there is an increase risk of a hazardous condition.
• the proximity sensor can comprise at least one display light, which is indicative of the presence or absence of liquid at the position of the proximity sensor.
• the proximity sensor 3 is in communication with a communication bus, for example via electrical connection 4.
• the electrolytic cell can be any chemical reactor that utilizes direct current electricity to induce the simultaneous oxidation and reduction of charged chemical components of an electrolyte (ions or a solution containing ions) to produce oxidized and reduced products in a process called electrolysis.
• the electrolyte can be a solution of an inorganic salt in a solvent, for example water.
• the electrolyte can also be a molten inorganic salt or oxide. Examples of electrolytes are aluminum, lithium, sodium, potassium, magnesium, calcium, copper, zinc, and lead salts and/or oxides, which are used in the production of the corresponding high purity metals.
• an electrolyte examples include bauxite, which is used in the production of aluminum, and sodium chloride, which is used in the simultaneous production of chlorine gas and sodium hydroxide.
• electrolysis an electric voltage is applied to the electrolyte via an anode and a cathode.
• the oxidation takes place in a half-cell comprising the anode, and the reduction takes place in a half-cell comprising the cathode.
• the electrolyte is a solution of sodium chloride in water (brine).
• the chloride ions are oxidized to chlorine gas in the half-cell comprising the anode, and water is reduced to hydrogen gas and hydroxide ion in the half-cell comprising the cathode.
• the brine that bathes the anode, and in which oxidation takes place, is called the anolyte, and the caustic solution which bathes the cathode, and in which reduction takes place, is called the catholyte.
• the two half-cells are separated by a permeable diaphragm, which can be made of asbestos or a ceramic material, which allows migration of sodium ions from the anode half-cell to the cathode half-cells, but not the back-migration of hydroxide ions.
• the electrolytic cell is a chlor-alkali electrolytic diaphragm cell, and the liquid is brine.
• a schematic diagram of an example of a chlor-alkali electrolytic diaphragm cell is provided in the Figure.
• the level tube comprises a vertical tube that can be opaque, translucent, or transparent, generally constructed of glass or plastic, positioned outside of the electrolytic cell.
• the level tube is in fluid communication with the electrolytic cell so that the liquid level in the level tube is the same as the liquid level in the electrolytic cell.
• the level tube 2 is in fluid contact with the liquid 12 at the side of the electrolytic cell.
• the level tube connects to the electrolytic cell at a point near the tops of the cathodes and anodes.
• the dimensions of the level tube can vary widely depending on the requirements of the application, manufacturing considerations, desired visibility of the liquid in the tube, and like considerations.
• the level tube can have an inside diameter of about 0.2 to about 2 inches, specifically about 0.25 to about 1 inch.
• the level tube can extend in a vertical direction about 6 to about 30 inches, specifically about 10 to about 20 inches above the tops of the cathodes and anodes.
• Proximity sensors detect the presence of nearby objects without any physical contact with the object.
• the proximity sensor detects the presence or absence of liquid at its position on the level tube, without coming into physical contact with the liquid.
• the proximity sensor can send a signal indicating either the presence or absence of liquid at its position on the level tube to the control system via a communication system.
• proximity sensors which operate using various types of electromagnetic radiation or acoustic waves to detect target objects.
• Types of proximity sensors include, but are not limited to, capacitive sensors, eddy-current sensors, inductive sensors, magnetic sensors, optical sensors, infrared sensors, and ultrasound sensors. Any of the foregoing can be used.
• the proximity sensor can be in a "barrel" (cylindrical) shape or "flat” (planar) shape.
• Flat proximity sensors can have the advantage of a lower weight than barrel proximity sensors, thereby imposing less stress on the level tube on which it is mounted.
• the proximity sensor can have a local display.
• the local display can be a LED or a LCD. A local display advantageously allows an operator to readily determine the operational status of the sensor while visually confirming the liquid level.
• the proximity sensor is a capacitive sensor.
• the capacitive sensor can have fixed or adjustable capacitance.
• the capacitive sensor has adjustable capacitance.
• the capacitance can be optimized for rapid detection of the presence or absence of liquid at the position of the capacitive sensor on the level tube.
• the capacitance should be such that it is suitable for detection of the presence of absence of liquid.
• the capacitive sensor should be unaffected by any build-up of solid residue on the inside of the level tube at the measurement position. Exemplary capacitive sensors that can be used are available from Lion Precision of St. Paul, Minnesota, Dwyer Instruments, Inc. of Michigan City, Indiana and others.
• the proximity sensor can be associated with the level tube by a variety of means that provide the desired degree of adjustability or fixedness.
• the proximity sensor rests on an elastomeric O-ring (6 in the Figure) around the level tube and is reversibly affixed to the level tube by way of a support (7 in the Figure).
• the proximity sensor is readily detached from the support and removed from the level tube.
• the position of the O-ring is readily adjustable by sliding along the vertical axis of the level tube.
• the electrical connection to the proximity sensor can be fixed or adjustable and/or detachable.
• the electrical connection is flexible so that the proximity sensor can be removed from the level tube for inspection and repair without disconnecting the electrical connection.
• adjusting the position of the proximity sensor on the level tube and maintenance of the proximity sensor can be done without interrupting the normal operation of the electrolytic cell.
• a target liquid level is determined, for example, the liquid level that provides a good balance of productivity, efficiency, and safety.
• the target liquid level depends on the type of electrolytic process and the type of electrolytic cell being used.
• the target liquid level can be identified with reference to any point within the electrolytic cell, for example the top of the cell, or the vertical distance measured from the top of the cathodes and anodes.
• the electrolytic process is the chlor-alkali process, and a diaphragm cell such as the one schematically depicted in the Figure is used
• the liquid level detected is that of the anolyte, i.e. the brine bathing the anode.
• the target liquid level can be about 4 to about 12 inches, specifically about 5 to about 10 inches, and more specifically about 6 to about 8 inches, above the top of the cathode.
• a single proximity sensor is used to provide an indication of a low liquid level relative to the target liquid level.
• the liquid level can be 0 to about 70 %, specifically 0 to about 60 %, more specifically 0 to about 50 % of the target liquid level.
• the liquid level can be 0 to about 6 inches, specifically 0 to about 5 inches, and more specifically 0 to about 4 inches, above the top of the cathode in the electrolytic cell.
• a single proximity sensor is used to provide an indication of a high liquid level relative to the target liquid level, for example the top of the cell.
• the liquid level when the liquid level represents a high liquid level, the liquid level can be about 70 to about 95 %, specifically about 70 to about 90 %, more specifically about 80 to about 90 % of the target liquid level.
• the high liquid level can be about 6 to about 3 inches, specifically 6 to about 4 inches, and more specifically 6 to about 5 inches below the top of the electrolytic cell.
• a plurality of proximity sensors can be positioned at various locations on the level tube.
• two proximity sensors are positioned on the level tube.
• the first proximity sensor can detect a first liquid level
• the second proximity sensor can detect a second liquid level below the first liquid level.
• the two proximity sensors can be used to provide indications of two liquid levels, for example the first proximity sensor can be used to provide a low liquid level indication, and the second proximity sensor can be used to provide a low-low liquid level indication.
• Indications of low liquid level and low-low liquid level are indications that action should be taken by an operator to increase the liquid level to the target liquid level, for example, by increasing the flow rate of the liquid into the electrolytic cell.
• the second proximity sensor which provides a low-low liquid level indication, can serve as a back-up to the first proximity sensor, which provides a low liquid level indication.
• the first liquid level when the first liquid level represents a low liquid level, the first liquid level can be about 40 to about 80 %, specifically about 50 to about 70 %, of the target liquid level.
• the second liquid level when the second liquid level represents a low-low liquid level, the second liquid level can be 0 to about 40 %, specifically about 20 to about 40 %, and more specifically about 30 to about 40 %, of the target liquid level.
• the first liquid level can be about 2 to about 6 inches, specifically about 3 to about 5 inches, and more specifically about 3.5 to about 4.5 inches above the top of the cathode in the electrolytic cell.
• the second liquid level can be 0 to about 4 inches, specifically about 1 to about 3 inches, and more specifically about 2 to about 3 inches, above the top of the cathode in the electrolytic cell.
• a reduction in liquid level in the electrolytic cell below the low-low level described above is a potentially hazardous condition.
• the electrolytic process is the chlor-alkali process
• the electrolytic cell is a diaphragm cell, such as the one schematically depicted in the Figure
• a further decrease in the liquid level below the low- low liquid level can result in exposure of the tops of the cathodes to the gases in the head space of the electrolytic cell, which comprise chlorine gas.
• the permeability of the diaphragm to hydrogen gas increases, and the potential exists for leakage of hydrogen gas into the head space comprising chlorine gas.
• a proximity sensor can be positioned on the level tube at a liquid level at a liquid level of 0 to about 2 inches, specifically 0 to about 1 inch, and more specifically, 0 to about 0.5 inch, above the top of the cathode in the electrolytic cell.
• a control system can be designed so that when a signal from a proximity sensor so positioned is received, controls which can shut off electrical power to the diaphragm cell, and which can purge the head space of the diaphragm cell with an inert gas or steam, are automatically actuated.
• the design of such control systems are within the ability of the skilled person in the art.
• a first and second proximity sensor can also be used to provide indications of high and low liquid levels.
• a first liquid level, detected by the first proximity sensor can be a high liquid level
• a second liquid level, detected by the second proximity sensor can be a low liquid level, each relative to a target liquid level determined by the top of the cathode in the electrolytic cell.
• the first liquid level can be about 110 to about 150 %, specifically about 110 to about 140 %, and more specifically about 110 to about 130 %, of the target liquid level.
• the first liquid level can be about 7 to about 12 inches, specifically about 7 to about 1 1 inches, and more specifically about 7 to about 10 inches, above the top of the cathode in the electrolytic cell.
• the second liquid level can be 0 to about 40 %, specifically about 20 to about 40 %, and more specifically about 30 to about 40 %, of the target liquid level.
• the second liquid level can be 0 to about 4 inches, specifically about 1 to about 3 inches, and more specifically about 2 to about 3 inches, above the top of the cathode in the electrolytic cell.
• the configuration with two or more proximity sensors also allows for redundancy. For example, if the first proximity switch fails, the second proximity switch can provide a backup signal for low liquid level.
• Various methods for providing redundancy in liquid level detection such as providing a plurality of proximity sensors for each electrolytic cell and/or a plurality of communication pathways for each proximity sensor will be readily apparent to the skilled person in the art.
• the proximity sensor is in communication with a control system via a communication system.
• the communication system can be a direct electric wire connection or wireless, including infrared.
• the communication system can be based on an industrial computer network protocol, for example an industrial Ethernet or a fieldbus.
• Fieldbus is the name for a family of industrial computer network protocols standardized under International Electrotechnical Commission (IEC) Standard 61 158.
• Fieldbus computer network protocols include Foundation Fieldbus HI, ControlNet, Profibus (process fieldbus), P-Net, Foundation Fieldbus HSE (High Speed Ethernet), WorldFIP, and Interbus.
• Computer network protocols related to fieldbus include AS-Interface (Actuator Sensor Interface, or AS-I), CAN bus (controller area network), Interbus, LonWorks, Modbus, Bitbus, CompoNet, SafetyBUS p, Sercos interface, and RAPIEnet.
• Industrial Ethernet network protocols include EtherCAT, EtherNet/IP, Ethernet Powerlink, BACnet, Profinet 10, Profinet IRT, SafetyNET p, Sercos III, TTEthernet, Varan, and RAPIEnet.
• the communication system can be fieldbus, Profibus, industrial Ethernet, or AS-Interface (Actuator Sensor Interface, or AS-i), more specifically an AS-Interface.
• AS-Interface is designed for networking simple field input/output devices, including binary On/Off devices, in discrete manufacturing and process applications using a single 2-conductor cable.
• Binary On/Off devices that can be networked with AS-Interface include actuators, sensors, rotary encoders, analog inputs and outputs, push buttons, and valve position sensors.
• the communication procedure in an AS-Interface is a master-slave method, by which the master initiates data exchange with a slave and requires the slave to respond within its defined maximum time.
• the AS-Interface comprises a network master, a plurality of network slaves, which are signal input and output modules, a power supply, which powers the network slaves, and which enables communication with the network master, and wiring infrastructure, comprising 2-conductor cables.
• AS-Interface is well-suited as a communication system for proximity sensors.
• the control system can be a digital control system (DCS).
• DCS digital control system
• Examples of digital control systems are microcontrollers, application-specific integrated circuits, programmable logic controllers (PLC, programmable controller), microcomputers, and mainframe computers.
• Microcomputers include, for example, workstations, personal computers (PC), portable computers, laptop computers, and tablet computers.
• the control system is in communication with the proximity sensor, and is responsive to the proximity sensor.
• the proximity sensor generates a signal, for example an electric signal, which is indicative of the presence or absence of liquid at its position on the level tube.
• This signal is transmitted via the communication system to the control system.
• the control system can be in communication with a plurality of proximity sensors positioned to detect the liquid levels in a plurality of electrolytic cells via the communication system. Based on signals received from the plurality of proximity sensors via the communication system, the control system can indicate the presence or absence of liquid as well as the identity and location of the electrolytic cell for each proximity sensor. In this way, the liquid level in a plurality of electrolytic cells can be monitored from a remote location.
• the control system can be programmed to issue an alarm as a function of electrolytic cell location when the liquid level drops out of the range of the proximity sensor.
• the alarm can be a light alarm, an auditory alarm, or a combination thereof.
• the alarm can also be in the form of an electronic signal to a receiver such as a pager.
• the control system can be programmed to transform signals form the proximity sensors to a numerical or graphical display of liquid level for each electrolytic cell being monitored.
• the control system can also be programmed to store and to display the liquid levels as a function of time.
• the programming can be done using commercially available software, for example, Lab VIEW, available from National Instruments Corporation of Austin, Texas.
• Lab VIEW is a graphical programming environment that uses graphical icons including graphical wires to generate programs in a format resembling a flowchart.
• a method for detecting liquid level in an electrolytic cell comprises providing an apparatus comprising a level tube in fluid contact with an electrolytic cell, a proximity sensor positioned on the level tube below a target liquid level to detect the presence or absence of liquid, and a control system responsive to the proximity sensor, wherein the control system is in communication with the proximity sensor via a communication system; wherein the proximity sensor detects the presence or absence of fluid in the level tube and sends a signal to the control system via the communication system; and the control system provides an indication of liquid level in response to the signal from the proximity sensor.
• a method for maintaining a target liquid level in an electrolytic cell comprises providing an apparatus comprising a level tube in fluid contact with an electrolytic cell, a proximity sensor positioned on the level tube below the target liquid level to detect the presence or absence of liquid, and a control system responsive to the proximity sensor, wherein the control system is in communication with the liquid level sensor via a communication system, and provides an indication of liquid level in response to a signal from the proximity sensor; and adjusting the liquid level in the electrolytic cell to the target level in response to the signal.
• Either of the foregoing methods can further comprise determining a target level for the liquid level, and determining the presence or absence of liquid relative to the target level. Adjusting the liquid level can be performed by the control system or a human operator.
• a method for maintaining a target liquid level in an chlor-alkali electrolytic diaphragm cell comprises providing an apparatus comprising a level tube in fluid contact with the chlor-alkali electrolytic cell, a capacitive proximity sensor adjustably mounted on the level tube to detect the presence or absence of a brine at a predetermined position on the level tube, a support for positioning and mounting the capacitive proximity sensor on the level tube, and a digital control system responsive to the capacitive proximity sensor, wherein the digital control system is in communication with the capacitive proximity sensor and indicates the presence or absence of the brine at the predetermined position on the level tube in response to a signal from the proximity sensor; and adjusting the brine level in the chlor-alkali electrolytic cell to the target level in response to the signal.
• a method for maintaining a target liquid level in a chlor-alkali electrolytic diaphragm cell comprises detecting with a capacitive proximity sensor the presence or absence of a brine at a predetermined position on a level tube in fluid contact with the chlor-alkali electrolytic cell, sending a signal from the capacitive proximity sensor to a digital control system in communication with the capacitive proximity sensor indicating the presence or absence of the brine at the predetermined position on the level tube; generating a signal from the control system indicating the presence or absence of the liquid at the predetermined position on the level tube; and adjusting the brine level in the chlor-alkali electrolytic cell to the target level in response to the signal from the control system.
• the apparatus for detecting a liquid level in an electrolytic cell can also be used to monitor inspection rounds made by an operator of the electrolytic cell. Operators can make inspection rounds at fixed intervals of time, for example at 30-minute intervals, to determine liquid levels by visual inspection of level tubes. When proximity sensors are positioned on the level tubes, the operator can inspect the proximity sensor at the same time. The operator can temporarily adjust the position of the proximity sensor above the actual liquid level to generate a signal for the absence of liquid, and then replace it to its original position. In this way, an inspection log based on brief indications of the absence of liquid at fixed time intervals can be generated by the digital control system.
• the control system can also be programmed to automatically adjust the fluid level in the electrolysis cell in response to indications of low or high fluid levels detected by the proximity sensors.
• the valves and/or pumps that control the flow of liquid in and out of the electrolytic cell are actuated valves and pumps, capable of being turned on and off, and adjusted, based on signals received from the control system via a control bus.
• Apparatus and methods for setting up automatic control of liquid level in an electrolytic cell will be apparent to the skilled person in the art based on the description of the apparatus and methods herein.
• the invention includes at least the following embodiments.
• Embodiment 1 An apparatus for detecting a liquid level in an electrolytic cell, the apparatus comprising a level tube in fluid contact with the electrolytic cell; a proximity sensor positioned to detect the presence or absence of liquid at a predetermined level in the level tube; and a control system responsive to the proximity sensor, wherein the control system is in communication with the proximity sensor via a communication system.
• Embodiment 2 The apparatus of embodiment 1, wherein the position of the proximity sensor is adjustable along the vertical axis of the level tube.
• Embodiment 3 The apparatus of embodiments 1 or 2, further comprising a support for positioning the proximity sensor in relation to the level tube.
• Embodiment 4 The apparatus of any of embodiments 1-3, wherein the proximity sensor comprises a display.
• Embodiment 5 The apparatus of any of embodiments 1-4, wherein the proximity sensor is a capacitive proximity sensor.
• Embodiment 6 The apparatus of embodiment 5, wherein the capacitive proximity sensor has a fixed capacitance for detecting the presence or absence of liquid in the level tube.
• Embodiment 7 The apparatus of embodiment 5, wherein the capacitive proximity sensor has an adjustable capacitance tunable to a value effective to detect the presence or absence of liquid in the level tube.
• Embodiment 8 The apparatus of embodiment 5, wherein the capacitive proximity sensor has a flat configuration and an adjustable capacitance.
• Embodiment 9 The apparatus of any of embodiments 1-8, wherein the communication system is a digital communication bus.
• Embodiment 10 The apparatus of any of embodiments 1 -9, wherein the communication system is a profibus, a fieldbus, or an industrial Ethernet.
• Embodiment 1 1 The apparatus of any of embodiments 1-10, wherein the control system issues a signal to an operator in response to a signal from the proximity sensor.
• Embodiment 12 The apparatus of any of embodiments 1-1 1, wherein the signal to an operator is a light alarm, a sound alarm, a pager alarm, or a combination thereof.
• Embodiment 13 The apparatus of any of embodiments 1-12, wherein the control system is a digital control system.
• Embodiment 14 The apparatus of any of embodiments 1 -13, wherein the liquid is an electrolyte.
• Embodiment 15 The apparatus of any of embodiments 1-14, wherein the electrolytic cell is a chlor-alkali electrolysis diaphragm cell.
• Embodiment 16 The apparatus of any of embodiments 1 -15, wherein the liquid is brine.
• Embodiment 17 The apparatus of any of embodiments 1-16, wherein the proximity sensor detects a low liquid level, and wherein the low liquid level is 0 to about 70 percent of a target liquid level.
• Embodiment 18 The apparatus of embodiment 17, wherein a target liquid level is about 6 to about 8 inches above the top of a cathode in the electrolytic cell; and wherein the low liquid level is 0 to about 4 inches above the top of the cathode in the electrolytic cell.
• Embodiment 19 The apparatus of any of embodiments 1 -18, comprising a first proximity sensor and a second proximity sensor, wherein the first proximity sensor detects a first liquid level, and the second proximity sensor detects a second liquid level below the first liquid level.
• Embodiment 20 The apparatus of embodiment 19, wherein the first liquid level represents a low liquid level and the second liquid level represents a low-low liquid level, and wherein the first liquid level is about 40 to about 80 percent of a target liquid level, and the second liquid level is 0 to about 40 percent of the target liquid level.
• Embodiment 21 The apparatus of embodiment 19, wherein a target liquid level is about 6 to about 8 inches above the top of a cathode in the electrolytic cell; wherein the first liquid level represents a low liquid level and the second liquid level represents a low- low liquid level; and wherein the first liquid level is about 3 to about 5 inches above the top of the cathode in the electrolytic cell, and the second liquid level is about 2 to about 3 inches above the top of the cathode in the electrolytic cell.
• Embodiment 22 The apparatus of embodiment 19, wherein the first liquid level represents a high liquid level and the second liquid level represents a low liquid level, and wherein the first liquid level is about 1 10 to about 130 percent of a target liquid level, and the second liquid level is 0 to about 40 percent of the target liquid level.
• Embodiment 23 The apparatus of embodiment 19, wherein a target liquid level is about 6 to about 8 inches above the top of a cathode in the electrolytic cell; wherein the first liquid level represents a high liquid level and the second liquid level represents a low liquid level; and wherein the first liquid level is about 7 to about 10 inches above the top of the cathode in the electrolytic cell, and the second liquid level is about 2 to about 3 inches above the top of the cathode in the electrolytic cell.
• Embodiment 24 The apparatus of embodiment 1, wherein the liquid is brine; the electrolytic cell is a chlor-alkali electrolytic cell; the proximity sensor is a capacitive proximity sensor adjustably mounted on the level tube; the control system is a digital control system; and the apparatus further comprises a support for positioning and mounting the capacitive proximity sensor on the level tube.
• Embodiment 25 A method for maintaining a target liquid level in an electrolytic cell, the method comprising providing an apparatus comprising a level tube in fluid contact with an electrolytic cell, a proximity sensor positioned on the level tube at the target liquid level to detect the presence or absence of a liquid, and a control system responsive to the proximity sensor, wherein the control system is in communication with the proximity sensor via a communication system, and indicates the presence or absence of the liquid at the target liquid level on the level tube in response to a signal from the proximity sensor; and adjusting the liquid level in the electrolytic cell to the target liquid level in response to the signal.
• Embodiment 26 The method of embodiment 25, the method further comprising detecting with the proximity sensor the presence or absence of the liquid at the target liquid level on the level tube; sending a signal from the proximity sensor to the control system indicating the presence or absence of the liquid at the target liquid level on the level tube; and generating a signal from the control system indicating the presence or absence of the liquid at the target liquid level on the level tube; and adjusting the liquid level in the electrolytic cell to the target liquid level in response to the signal from the control system.
• Embodiment 27 The method of embodiment 25 or 26, wherein the position of the proximity sensor is adjustable along the vertical axis of the level tube.
• Embodiment 28 The method of any of embodiments 25-27, wherein the apparatus further comprises a support for positioning the proximity sensor in relation to the level tube.
• Embodiment 29 The method of any of embodiments 25-28, wherein the proximity sensor comprises a display.
• Embodiment 30 The method of any of embodiments 25-29, wherein the proximity sensor is a capacitive proximity sensor.
• Embodiment 31 The method of embodiment 30, wherein the capacitive proximity sensor has a fixed capacitance for detecting the presence or absence of liquid in the level tube.
• Embodiment 32 The method of embodiment 30, wherein the capacitive proximity sensor has an adjustable capacitance tunable to a value effective to detect the presence or absence of liquid in the level tube.
• Embodiment 33 The method of embodiment 30, wherein the capacitive proximity sensor has a flat configuration and an adjustable capacitance.
• Embodiment 34 The method of any of embodiments 25-33, wherein the communication system is a digital communication bus.
• Embodiment 35 The method of any of embodiments 25-34, wherein the communication system is a profibus, a fieldbus, or an industrial Ethernet.
• Embodiment 36 The method of any of embodiments 25-35, wherein the control system issues a signal to an operator when the liquid is present or absent at the target level on the level tube.
• Embodiment 37 The method of embodiment 36, wherein the signal to the operator is a light alarm, a sound alarm, a pager alarm, or a combination thereof.
• Embodiment 38 The method of any of embodiments 25-37, wherein the control system is a digital control system.
• Embodiment 39 The method of any of embodiments 25-38, wherein the liquid is an electrolyte.
• Embodiment 40 The method of any of embodiments 25-39, wherein the proximity sensor detects a low liquid level, and wherein the low liquid level is 0 to about 70 % of the target liquid level.
• Embodiment 41 The method of embodiment 40, wherein the target liquid level is about 6 to about 8 inches above the top of a cathode in the electrolytic cell; and wherein the low liquid level is 0 to about 4 inches above the top of the cathode in the electrolytic cell.
• Embodiment 42 The method of any of embodiments 25-41 , wherein the apparatus comprises a first proximity sensor and a second proximity sensor, wherein the first proximity sensor detects a first liquid level, and the second proximity sensor detects a second liquid level below the first liquid level.
• Embodiment 43 The method of embodiment 42, wherein the first liquid level represents a low liquid level and the second liquid level represents a low-low liquid level, and wherein the first liquid level is about 40 to about 80 percent of the target liquid level, and the second liquid level is 0 to about 40 percent of the target liquid level.
• Embodiment 44 The method of embodiment 42, wherein the target liquid level is about 6 to about 8 inches above the top of a cathode in the electrolytic cell; wherein the first liquid level represents a low liquid level and the second liquid level represents a low- low liquid level; and wherein the first liquid level is about 3 to about 5 inches above the top of the cathode in the electrolytic cell, and the second liquid level is about 2 to about 3 inches above the top of the cathode in the electrolytic cell.
• Embodiment 45 The method of embodiment 42, wherein the first liquid level represents a high liquid level and the second liquid level represents a low liquid level, and wherein the first liquid level is about 110 to about 130 percent of the target liquid level, and the second liquid level is 0 to about 40 percent of the target liquid level.
• Embodiment 46 The method of embodiment 42, wherein the target liquid level is about 6 to about 8 inches above the top of a cathode in the electrolytic cell; wherein the first liquid level represents a high liquid level and the second liquid level represents a low liquid level; and wherein the first liquid level is about 7 to about 10 inches above the top of the cathode in the electrolytic cell, and the second liquid level is about 2 to about 3 inches above the top of the cathode in the electrolytic cell.
• Embodiment 47 The method of embodiment 25, wherein the liquid is brine; the electrolytic cell is a chlor-alkali electrolytic cell; the proximity sensor is a capacitive proximity sensor adjustably mounted on the level tube; the control system is a digital control system; and the apparatus further comprises a support for positioning and mounting the capacitive proximity sensor on the level tube.
• Embodiment 48 The method of embodiment 47, further comprising detecting with the capacitive proximity sensor the presence or absence of the brine at the target brine level on the level tube; sending a signal from the capacitive proximity sensor to the digital control system indicating the presence or absence of the brine at the target brine level on the level tube; generating a signal from the digital control system indicating the presence or absence of the brine at the target liquid level on the level tube; and adjusting the brine level in the chlor-alkali electrolytic cell to the target brine level in response to the signal from the digital control system.
• Embodiment 49 The method of embodiment 47 or 48, wherein the position of the capacitive proximity sensor is adjustable along the vertical axis of the level tube.
• Embodiment 50 The method of any of embodiment 47-49, wherein the capacitive proximity sensor comprises a display.
• Embodiment 51 The method of any of embodiments 47-50, wherein the capacitive proximity sensor has a fixed capacitance for detecting the presence or absence of brine in the level tube.
• Embodiment 52 The method of any of embodiments 47-50, wherein the capacitive proximity sensor has an adjustable capacitance tunable to a value effective to detect the presence or absence of brine in the level tube.
• Embodiment 53 The method of any of embodiments 47-52, wherein the communication system is a digital communication bus.
• Embodiment 54 The method of any of embodiments 47-53, wherein the control system issues a signal to an operator when the brine is present or absent at the target brine level on the level tube.
• Embodiment 55 The method of embodiment 54, wherein the signal to the operator is a light alarm, a sound alarm, a pager alarm, or a combination thereof.
• Embodiment 56 The method of any of embodiments 47-55, wherein the chlor-alkali electrolytic cell is a diaphragm cell.
• Embodiment 57 The method of any of embodiments 47-56, wherein the capacitive proximity sensor detects a low brine level, and wherein the low brine level is 0 to about 70 % of the target brine level.
• Embodiment 58 The method of embodiment 57, wherein the target brine level is about 6 to about 8 inches above the top of a cathode in the chlor-alkali electrolytic cell; and wherein the low brine level is 0 to about 4 inches above the top of the cathode in the chlor-alkali electrolytic cell.
• Embodiment 59 The method of any of embodiments 47-58, wherein the apparatus comprises a first capacitive proximity sensor and a second capacitive proximity sensor, wherein the first capacitive proximity sensor detects a first brine level, and the second capacitive proximity sensor detects a second brine level below the first brine level.
• Embodiment 60 The method of embodiment 59, wherein the first brine level represents a low brine level and the second brine level represents a low-low brine level, and wherein the first brine level is about 40 to about 80 percent of the target brine level, and the second brine level is 0 to about 40 percent of the target brine level.
• Embodiment 61 The method of embodiment 59, wherein the target brine level is about 6 to about 8 inches above the top of a cathode in the chlor-alkali electrolytic cell; wherein the first brine level represents a low brine level and the second brine level represents a low-low brine level; and wherein the first brine level is about 3 to about 5 inches above the top of the cathode in the chlor-alkali electrolytic cell, and the second brine level is about 2 to about 3 inches above the top of the cathode in the chlor-alkali electrolytic cell.
• Embodiment 62 The method of embodiment 59, wherein the first brine level represents a high brine level and the second brine level represents a low brine level, and wherein the first brine level is about 110 to about 130 percent of a target brine level, and the second brine level is 0 to about 40 percent of the target brine level.
• Embodiment 63 The method of claim 59, wherein the target brine level is about 6 to about 8 inches above the top of a cathode in the chlor-alkali electrolytic cell; wherein the first brine level represents a high brine level and the second brine level represents a low brine level; and wherein the first brine level is about 7 to about 10 inches above the top of the cathode in the chlor-alkali electrolytic cell, and the second brine level is about 2 to about 3 inches above the top of the cathode in the chlor-alkali electrolytic cell.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• General Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Thermal Sciences (AREA)
• Electromagnetism (AREA)
• Chemical & Material Sciences (AREA)
• Automation & Control Theory (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Electrochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Signal Processing (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Electrolytic Production Of Metals (AREA)
• Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
• Water Treatment By Electricity Or Magnetism (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=47628433

Family Applications (1)

Country Status (6)

Cited By (1)

Families Citing this family (2)

Family Cites Families (28)

• 2012
  • 2012-12-26 US US13/726,988 patent/US20130213818A1/en not_active Abandoned
  • 2012-12-26 BR BR112014018043A patent/BR112014018043A8/pt not_active IP Right Cessation
  • 2012-12-26 WO PCT/US2012/071638 patent/WO2013122677A1/en active Application Filing
  • 2012-12-26 KR KR1020147025897A patent/KR20140126384A/ko not_active Application Discontinuation
  • 2012-12-26 CN CN201280068767.7A patent/CN104094089A/zh active Pending
  • 2012-12-26 EP EP12819167.3A patent/EP2815215A1/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events