[go: up one dir, main page]
More Web Proxy on the site http://driver.im/

WO2014106078A2 - Instruments de surveillance de phénomènes électrostatiques dans des réacteurs - Google Patents

Instruments de surveillance de phénomènes électrostatiques dans des réacteurs Download PDF

Info

Publication number
WO2014106078A2
WO2014106078A2 PCT/US2013/078044 US2013078044W WO2014106078A2 WO 2014106078 A2 WO2014106078 A2 WO 2014106078A2 US 2013078044 W US2013078044 W US 2013078044W WO 2014106078 A2 WO2014106078 A2 WO 2014106078A2
Authority
WO
WIPO (PCT)
Prior art keywords
probe
vessel
static
stream
charge
Prior art date
Application number
PCT/US2013/078044
Other languages
English (en)
Other versions
WO2014106078A3 (fr
Inventor
William A. Lamberti
Joseph A. MOEBUS
Harry W. Deckman
Charles R. BUHLER
Judson S. CLEMENTS
Original Assignee
Exxonmobil Research And Engineering Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Exxonmobil Research And Engineering Company filed Critical Exxonmobil Research And Engineering Company
Priority claimed from US14/141,857 external-priority patent/US9328177B2/en
Priority claimed from US14/142,179 external-priority patent/US9360453B2/en
Publication of WO2014106078A2 publication Critical patent/WO2014106078A2/fr
Publication of WO2014106078A3 publication Critical patent/WO2014106078A3/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/002—Scale prevention in a polymerisation reactor or its auxiliary parts
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2/00—Processes of polymerisation
    • C08F2/34—Polymerisation in gaseous state
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/60—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrostatic variables, e.g. electrographic flaw testing
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2400/00—Characteristics for processes of polymerization
    • C08F2400/02—Control or adjustment of polymerization parameters

Definitions

  • FIELD [0001] The disclosure relates to specialized instruments for measuring and monitoring electrostatic phenomena in complex environments such as those which exist within gas-phase, fluidized bed reactors.
  • Fouling in commercial fluidized bed reactors, including gas phase polymerization reactors, is a significant operational issue. Fouling negatively impact operational efficiency and ultimately requires time-consuming shutdown and maintenance.
  • Fouling in fluidized bed reactors can be strongly affected by physical processes within the fluidized bed reactor, such as electrostatic charge and solids carryover within a recycle loop.
  • Electrostatic charge can affect commercial process units such as chemical reactors, granular particle handling equipment, transfer lines, holding tanks, and shipping containers, for example.
  • the types of operations can include fluidized bed reactors for producing a variety of chemical products such as gas, liquid or solid products such as polyethylene.
  • Cryogenic processes or handling equipment are another notable case where the dry environment can lend itself to electrostatic charge buildup in at least some portions of a process, especially if solids such as ice form due to the cryogenic conditions.
  • the buildup of electrostatic charge on particles, and/or process components results in the formation of an electric field, which then exerts forces on particles or components within a given process or system.
  • electrostatic discharge events can occur, which by themselves can be deleterious to reliable or safe operations, or simply an indicator that electrostatic effects are present at a given moment.
  • PE polyethylene
  • reactors utilize a fluidized bed to suspend catalyst particles that grow into PE resin particles by converting ethylene gas into polyethylene resin. Collisions between catalyst particles, resin particles and also the reactor wall can result in the particles becoming charged. The wall can also become charged wherever it has an insulating coating or surface deposit or layer.
  • the monitor system must be installed as specified in this user's guide. It is intended for use in the following environmental conditions only: (1) indoor use; (2) altitudes up to 2,000 meters above sea level; (3) temperature range of 10°C to 40°C; (4) maximum relative humidity of 80% for temperatures up to 31°C, decreasing linearly to 50% relative humidity at 40°C; and (5) pollution degree two (office, laboratory, test station).
  • a coated static probe which monitors the electrostatic charge on particles entrained in the gas stream of a vessel, the probe comprising: an electrode, such as a metal rod with a modified surface comprising an electrically insulating coating, thereby mitigating triboelectrification of the probe arising from charge transfer from impinging particulates and extraneous signals via charge saturation of the coating.
  • the coating is a dielectric material that maintains a saturation charge layer and inhibits tribocharging.
  • the dielectric material is a high dielectric strength, and high volume and surface resistivity.
  • the dielectric material is at least one material selected from the group consisting of: polyethylene, polypropylene, polytetrafluoroethylene, polyether ether ketone, aluminum oxide, silicon dioxide, iron oxide, and any other electrically insulating material, such as glasses, ceramics and polymers.
  • the dielectric material maintains the charge saturation by exhibiting high dielectric strength, and high surface resistivity and high volume resistivity. Additionally, proper relative placement within triboelectric series can help maintain charge saturation.
  • the dielectric strength determines the maximum electric field at which the material reaches electrical breakdown.
  • the surface and volume resistivity determine the rate at which a material will discharge analogous to an C circuit.
  • the placement within triboelectric series affects the amount and polarity of charge transferred due to contact and separation.
  • the coating is applied to the static probe by dip coating, for example.
  • the dip coating comprises the steps of: heating the static probe; submerging the heated static probe into a bed of polymer particles with suitable melting point and adhesive properties, such that the polymer particles adhere to the static probe; heating the static probe after the polymer particles have been adhered thereto to the point where they begin to flow; and once the polymer particles have formed a uniform coating on the static probe, heating is stopped, thereby allowing the coating to harden on the static probe.
  • a method for monitoring the electrostatic charge on particles entrained in the gas stream of a vessel comprises: disposing the coated static probe within the gas stream of the vessel.
  • the gas stream is at least one stream selected from the group consisting of: a product discharge stream, a recycle stream, , a fluidizing gas stream, a mixing stream, a purge stream, a feed stream, and a transfer stream, for example .
  • the vessel is at least one vessel selected from the group consisting of: a fluidized bed reactor, a product tank, a purge vessel, a holding vessel, a shipping vessel, a discharge tank, a mixing vessel, piping between the vessels, a shipping vessel, a rail car, and/or a truck.
  • a coated static probe which monitors the electrostatic charge on particles entrained in the gas stream of a vessel, the probe comprising: a metal electrode, often in the form of a rod, with a modified surface comprising a coating which measures the ambient direct current electric field by periodically blocking the field near the probe while also substantially minimizing particle-to- surface interactions via purging of a sensing element with a flowing gas.
  • An RF probe which monitors the electrostatic discharges in a vessel, the probe comprising: an antenna; a flange bolted to a mating flange welded on the outside of a wall of the vessel; an electrode, such as a metal rod connected to the antenna, wherein the rod is hermetically sealed by means of an insulating material, thereby electrically isolating the antenna from the flange; an electronics module and a power supply disposed within a pressure containment housing or a separate shielded, cooled external enclosure located outside of the vessel and electronically connected to the rod; and an electrically conductive wire which electronically connects the antenna to the electronics module.
  • the RF probe further comprises a double pressure containment housing.
  • the RF probe is a hardened probe comprising: (a) spark detection electronics, or (b) circuitry with high sensitivity and high speed electrical response together with a single channel analyzer and/or frequency based filter circuitry.
  • the frequency based filter circuitry is at least one selected from the group consisting of: lock-in amplification, Fourier analysis, digital filtering and correlation circuits, integrators, baseline shifters, and averaging circuits.
  • the probe sensitivity is proportional to the length of the antenna.
  • the RF probe wherein the wire is a coax cable and the electronics module comprises a receiver/amplifier filter.
  • a method for monitoring the electrostatic discharges in a vessel which comprises: disposing the RF probe within the gas stream of the vessel.
  • a probe which monitors the electrostatic state in a vessel is at least one selected from the group consisting of: a coated or uncoated static probe, an oscillatory electric field probe, a chopped electric field probed, and a radio-frequency antenna probe.
  • a fluidized bed reactor comprising either a coated static probe or a radio frequency (RF) probe disposed in at least one portion of the fluidized bed reactor selected from the group consisting of: a recycle line, product discharge system, fluid bed, expanded or disengagement zone above the fluidized bed, purge system, and product handling or shipping system.
  • RF radio frequency
  • RF radio frequency
  • Fig. 1 is a plot of static probe filtered frequency data from the reactor or lower bed.
  • Fig. 2 is a plot of raw current data from the coated product chamber static probe (left) and acquisition rate and surface area compensated integral or charge (right).
  • Fig. 3 is a plot of the inverse of the cycle gas or recycle line static mean.
  • Fig. 4 is month long plot of the variance of the upper bed static vs. the charge calculated from the product chamber discharge integral.
  • Fig. 5 is a plot of the center of the autocorrelation of the recycle line static probe signal.
  • Fig. 6 is a plot of the center of the cross-correlation of the cooler inlet and outlet acoustic probes.
  • Fig. 7 is a plot of the cross-correlation of the recycle line static signal with the cooler inlet acoustic signal.
  • Fig. 8 is a plot of the autocorrelation of the upper bed static probe signal (left) and the cross-correlation of the upper bed static signal with its integral (right).
  • Fig. 9 depicts an embodiment of a conventional gas-phase fluidized- bed reactor system.
  • Fig. 10 is a double-plot in which the plot of Fig. 1 is split into components.
  • Fig. 1 1 is a representative cross-section of a custom F probe for high temperature, high pressure reactor.
  • Fig. 12a is a picture of the spark-gap.
  • Fig. 12b shows a high voltage power supply and the wooden-dowel tera-ohm range adjustable resistor connected to the spark gap.
  • Fig. 13 is an example of the data acquisition and control program text file output.
  • Fig. 14 is a screen shot of the custom program developed for the F Probe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • Useful techniques include Fourier analysis, digital filtering of high-speed static probe data (i.e., data sampling rates faster than 10 Hz; 100 Hz is typical), integrations, baseline shifts, time-resolved means and inverse means, time-resolved variances, auto-correlations, cross-correlations, and direct correlations with other sensor information.
  • Static probes measure current. Sources of current can be direct tribo- charging due to particle impact or induced current arising from fluctuations in the electric field. Bare metal static probes signals can be dominated by triboelectric charge transfer via particle collisions, which affects mean and integral values of the static probe signal.
  • Surface-altered static probes have a dielectric coating made from an electrostatically insulating material applied to the sensing tip that mitigates the triboelectric charge transfer. For the coating to be an effective mitigation technique, the coating must reach a state of charge saturation in which further charge transfer is reduced, on average, to an insignificant level. This mitigates direct tribo-electric charging.
  • the amount of time the coating takes to reach the charge-saturated state is dependent on the material the coating is made of and the charge transfer rate of the impinging particles. Mitigation of the triboelectric charge transfer and charge injection allows for accurate measurement of the mean and variance of the resultant static probe signal.
  • FIG. 9 shows product discharge tanks 20 and 22 used to remove product from a fluid bed reactor (components 12, 1, 4, 28 and 18).
  • Coated static probes (38 and 40) located in the product discharge tanks (20 and 22) provide a means to accurately measure charge on the resin discharged as product from the fluidized bed reactor (components 12, 1, 4, 28 and 18).
  • the data processing techniques described in this application provide a means to extract a quantity proportional to the charge on the resin discharged into the tank when a coated static probe is used. Changes in this quantity in each discharge cycle provide a means to monitor how the charge on the resin changes during reactor operation.
  • Fig. 9 shows a coated static probe 31 located in the recycle line 30.
  • Coated static probes 31 provide a means to monitor the charge on the particles entrained in the gas stream being recycled. Without a coating on the probe particles in the recycle gas stream impact the probe and produce a signal from triboelectric charging that can overwhelm the signal coming from charge on the particles passing the probe.
  • the data processing techniques described in this application provide a means to extract a quantity related to the charge on the particles flowing in the recycle line. Changes in this quantity in provide a means to monitor how the charge on the resin changes during reactor operation.
  • the aforementioned coated static probes can be used with product vessels and tanks including, but not limited to: • Product tanks
  • Electrostatic charge can be bulk, individual, or refer to sign of particles passing near tip of probe.
  • a preferred static probe is coated with a dielectric.
  • the surface properties of the probe can be configured to measure specific physical and chemical processes.
  • the coated probe substantially reduces noise and/or artifacts in signals transmitted.
  • the coated probe essentially takes the form of an electrode, such as a metal rod with a modified surface.
  • the probe can be configured to measure, among other things, electrostatic charge, changing or fluctuating electric field, bubbles in charged fluid beds, and detection of transient surface active species (gas, liquid, or solid) not normally present, or desired, in a given system (i.e., contaminants in a system).
  • a static probe can be coated with an electrically insulating composition to mitigate triboelectrification of the probe arising from charge transfer from impinging particulates and therefore mitigate extraneous signals via charge saturation of the coating.
  • Conventional measurement methods are not viable when particles impact an uncoated sensing element because of the resultant signal altering charge transfer due to the impacts.
  • a static probe can be coated to measure the ambient DC (direct current) electric field by periodically blocking the field near the probe while also substantially preventing particle-to-surface interactions via purging of the sensing element with a flowing gas. Since a conventional probe can only measure a change in induced signal, the probe does not have the ability to measure a DC or constant field as they do not create a change in induced charge at the probe tip (the derivative of a constant field is zero, therefore no change. By alternately blocking the electric field from reaching the probe's sensing element and then removing the block, a changing electric field is created. Then a change in induced charge at the probe tip can be observed and calibrated to a known field strength. Accurately measuring the DC field is possible if particle impacts and unwanted charge transfer with the probe are prevented, such as purging with a flowing gas stream.
  • Dielectric strength determines the maximum electric field at which the material reaches electrical breakdown (also known as dielectric breakdown voltage).
  • Surface and volume resistivity determine the rate at which a material will discharge analogous to an C circuit. Surface resistivity describes the amount of conduction across the surface, while volume resistivity describes the amount of conduction through the material. Typical values of resistivity are the following: Conductive ⁇ 10 4 , 10 4 > Dissipative ⁇ 10 11 , Insulating > 10 11 (ANSI-ESD Surface Units: ⁇ ; ANSI-ESD Volume Units: ⁇ -cm).
  • Useful coating materials include, for example, polyethylene.
  • Coating of static probes can be carried out by any means known in the art. One method is to heat the static probe with a heat gun then submerge it into a bed of polymer particles with suitable melting point and adhesive properties (if desired, the probe can be heated with an oven to ensure uniform heating). The particles then stick to the probe. With the particles in place, they can then be heated to the point where they begin to "flow" using the heat gun. Once the particles have formed a uniform coating, the heat source is removed so the coating can harden. This process is commonly called a dip coating. Other known dip coating methods may also be used.
  • Acoustic probes measure energy transfer due to collisions and/or vibration. Ideal data acquisition for these probes would be high speed (>20 kHz) to allow for Fourier analysis to determine particle flux. The signal from these probes can be dominated by mechanical noise and tube waves. It would be desirable to have methods for filtering out such noise and waves.
  • RF Probes [0071] In the present disclosure, we are utilizing a novel spark detector to detect discharges inside a commercial PE reactor. These reactors are typically operated at about 80 degrees C and 20 atmospheres of pressure. No existing spark detectors such as the 3M EM Aware can survive in these conditions. Therefore we developed a custom RF probe that feeds through the reactor wall (shown in Fig. 1 1). The RF probe employs double pressure containment for extra safety because reactor gas leaks can be extremely dangerous. Reactor gas components include ethylene, hydrogen, and other potentially explosive components.
  • the electronics used to detect the RF events cannot be located within the reactive environment due to problems such as chemical compatibility of components, electronics stability, electronics failure, high and variable temperatures, spurious signal generation, and electrical energy input into a potentially explosive environment.
  • the specialized technology which we employ to address these various issues around safety, spurious signal suppression, and overall performance is referred to herein as "hardened”.
  • the probe sensing tip, or antenna is also an important component in our design. Most notably, the probe cannot be located too close to metal surface such as a reactor wall, flange or other grounded metal surface.
  • the probe sensitivity is also tunable as the sensitivity is proportional to the antenna length within the reactor environment. This antenna length, however, must not be too great as to interfere with the fluidized bed operations or present a surface that is prone to fouling due to its size, shape, and or location within the reactor environment.
  • the RF antenna was connected using coax to the receiver/amplifier electronics located in an electromagnetic interference (EMI)-shielded and cooled enclosure outside the reactor.
  • EMI electromagnetic interference
  • Effective EMI shielding required pi filters on the dc power supply lines at the shield surface to block spurious radio signals carried into the enclosure by the dc lines.
  • the receiver/amplifier filter and threshold settings were optimized for the reactor electrical environment.
  • a custom data acquisition program was written to monitor and record the spark counts and intensities.
  • the schematic drawing of an example of the hardened RF probe is shown below in Fig. 1 1.
  • the probe contains a flange (1) that is bolted to the mating flange welded on the outside of the reactor wall.
  • a large section of the probe assembly (2, 10, 1 1, 12) protrudes inside the reactor volume.
  • the probe is comprised of a solid metal cylindrical rod antenna (2) connected to a metal rod (2a) that feeds through the reactor wall and flange (1).
  • This rod (2a) is hermetically sealed, using high- strength, high-temperature-rated insulating materials such as fiberglass (10) and Peek (3), to the flange housing in order to keep the antenna electrically isolated from the grounded flange (1); while also being able to pass high-pressure testing.
  • Both ends of the rod (2a) are threaded: one attaches to the antenna (2) and the other accepts a washer (4) and jam-nut (5) which attaches the center conductor of a coax cable to the rod (2a).
  • the electronics module (15) is installed in the secondary pressure containment housing (14).
  • the housing (14) is located outside the reactor, and is attached to the flange (1) using threaded nuts (8, 9). Viton O-ring (6) is used as part of the secondary pressure seal.
  • a dc power supply (13) for the module (15) can also be optionally installed in the housing (14). In this embodiment, the presence of the electronics module (15) in the housing (14) necessitates cooling it when ambient temperatures are high.
  • the electronics module and dc power supply are located in a separate shielded, cooled external enclosure.
  • the antenna is connected to the electronics using coax cable that is run through metal conduit connecting the housing (14) to the shielded external enclosure.
  • the unique F probe of the present disclosure exhibits the following properties:
  • RF Probe detects electrical discharges of various types Unique elements:
  • Electrode designed to increase sensitivity while minimizing fouling
  • RF Probe in holding or shipping vessels such as railcars or trucks.
  • RF Probe for use in a chemical plant, refinery, or other field-based or mobile hydrocarbon processing facility such as an offshore rig or marine vessel.
  • FIG. 12a A small spark gap generator was fabricated as shown in Fig. 12a. This spark gap was attached to the end of the 21 -foot tube as shown in the right side of Fig. 12b.
  • Fig. 12b also shows the circuit which contains a 10 kV DC power supply connected to a ⁇ 1 ⁇ adjustable resistor in series with the spark gap.
  • the resistor is a wooden dowel with alligator clip electrodes clipped to it with various separation distances. The resistance is adjusted by changing the separation distance. The resistance controls the repetition frequency of the spark by changing the charging current to the capacitance of the electrodes.
  • a capacitor can also be added to increase the energy of the spark by simply coating the wire with aluminum foil and attaching it to ground, but the tests here created the smallest spark possible without the capacitor.
  • the energy of the spark was determined by first measuring the breakdown voltage of the gap by ramping up the voltage until the gap sparked. This was found to be 8.1 kV.
  • the energy of the spark is approximately 1 ⁇ 2 CV 2 , where V is the voltage at breakdown (8.1 kV). The calculated energy was 417 ⁇ .
  • Measurements of the RF signals generated by the sparks were recorded using the RF Probe with the 3M EM Aware electronics module. A low- light video camera was also used to verify that a spark occurred. A data acquisition program was written so that logs of spark events could be recorded. An example of the output text file is shown in the Fig. 13 below.
  • the name of the file contains the date and time of an RF event. Using the recommended camera exposure time of 500 mS yields a log file that recorded for 0.5 seconds.
  • the file contains the trigger type and how the event was triggered, as well as data for all the RF sparks that occurred during that 0.5 second period.
  • the RF probe signal magnitude of each spark is given in volts (4.3962 in this case). Exposure time, camera temperature, and binning parameters are also given in the data file.
  • GUI graphical user interface
  • RF Probe Data The signals from the RF Probe are displayed in the RF Probe Data box. The bottom scale is time and the y-axis is the ESD event magnitude in volts. All of the ESD event processing is performed within the RF Probe using the EM Aware® electronics module. The 4..20 mA output of the EM Aware® from the RF Probe is converted into a 0-10 volt signal using a Burr-Brown RCV420 DIP chip which is read by the National Instruments DAQ A/D connected to the computer using the PCI bus. The NI DAQ board is a model PCI-6259 and is controlled from within the MATLAB program.
  • RF Probe Controls can be sent remotely using this box on the GUI.
  • the threshold magnitudes range from 1 to 10 can be controlled by the user. Once a threshold is chosen, the user clicks "Send to RF Probe" and a voltage output from the NI DAQ D/A connected to the computer is converted to a 4..20 mA signal using an external Burr-Brown XTR1 10 DIP chip. A corresponding verification signal is sent back from the RF Probe and is displayed in the RF Probe Data box.
  • RF Log Mode The RF Log Mode is designed to store RF Data for long periods of time. It can be triggered to save data Always, Only When Triggered, or None. The result is a small text file (shown in Figure 3) that outputs the event magnitude date and time stamp. Each subsequent event is appended to that file.
  • Trigger Mode - Rf data is stored for every event. Trigger occurs for the RF probe when events occur that are larger than the threshold set by the user in the RF Probe Controls box.
  • Event Data The Event Data box displays a running total of the number of RF Events triggered, Saved Triggered Events, RF Events per Cycle, Total RF Events and whether the program is running or not. It also displays the current state of the program.
  • Fig. 9 depicts an embodiment of a conventional gas-phase fluidized bed reactor system 10.
  • System 10 has a gas-phase reactor 12 employing a recycle stream 30 for imreacted gas and solids.
  • Reactor 12 typically has a bed 14, an expanded section 16, a distributor plate 18, a first product chamber 20, a second product chamber 22, and product conduits 24 and 26 for conveying product to chambers 20 and 22, and an enhanced fill line 29.
  • the enhanced fill line is defined any part of the product discharge system that is used to permit unreacted gas and fine particles to return to the reactor system.
  • reactor 12 contains a solid phase 28, typically a catalyst.
  • a reactant gas (not shown) is passed through distributor plate 18 through solid phase 28 in bed 14 and out of expanded section 16 into recycle stream 30.
  • Recycle stream 30 has a compressor 32 and a heat exchanger 34 (such as a cooler) there along for pressurization, transport, and temperature modification of the reactant gas prior to return to reactor 12.
  • Enhanced fill line 29 permits gas (and tiny particles entrained therein) to be recycled from product chamber 22 to the top of reactor 12.
  • a second, analogous enhanced fill line could be employed between product chamber 20 and the top of reactor 12.
  • System 10 has static probes 31, 32, 34, 36, 38, and 40 positioned into reactor 12 approximately at bed 12, the upper region of bed 12, expanded section 36, product chamber 20, and product chamber 22, respectively.
  • System 10 has acoustic probes 38 and 40 positioned within the inlet and outlet, respectively, of heat exchanger 34. Precise placement, number and types of these probes can vary from reactor to reactor.
  • Fluidized bed reactor systems are disclosed by way of example in EP0784637 B2; EP0970970 B 1 ; EP1623999 A1 ; EP2263993 A2; U.S. 6,660,812 B2; WO2005/1 13615 A2; and WO2002/06188 A2, all of which are incorporated herein by reference in their entireties.
  • a signal is received from a probe in contact with the interior of the reactor or a process component in communication with the reactor.
  • the signal can be measured by a variety of measurement techniques and equipment, including amplifiers, filters, analog-to- digital converters, oscilloscopes, and or a computer.
  • the signal is modified, processed, or analyzed by mathematical processing or signal analysis techniques. This processing can be done in real- time using a computer system or specialized hardware. The processing can also be done as a post-analysis step resulting in a time-lag between measurement and human ability to react.
  • the processed result is derived, i.e., promulgated in response to, a physical property or condition within the reactor or a process component thereof, e.g., a recycle line or heat exchanger.
  • Physical properties or conditions include fluctuating electric field, sign of passing individual charged particles, presence of transient surface active species, bubbles in charged fluid beds, bubble size, bubble transit time, particle flux, gas velocity, and or mass flow.
  • one or more operating parameters of the reactor are adjusted if the value for the physical property or condition is different than a desired or predetermined value.
  • the desired or predetermined value may be a constant or may be variable-dependent or an algorithm or operator input.
  • instruments for measuring and/or monitoring electrostatic phenomena within a gas-phase, fluidized-bed reactor. These instruments are used to make adjustments within the reactor to minimize electrostatic forces so as to improve performance and reduce negative effects, such as fouling and material carryover into the recycle system. These instruments function by measuring a particular electrostatic parameter such as, but not limited to, charge, electric field, and/or current; and then suppressing spurious signals such as tribocharging due to particle impacts, through specialized instrument design and data analysis methods.
  • the specialized instrument is a coated or uncoated static probe for measuring electric field and or particle charge state.
  • the specialized instrument is an oscillatory electric field probe for measuring electric field.
  • the specialized instrument is a chopped electric field probe for measuring electric field.
  • the specialized instrument is a radio-frequency antenna probe for detecting electrostatic discharges.
  • a typical fluidized bed, gas phase polyethylene reactor operates at approximately 300 psig and 85 degrees C with a feed gas composition dependent upon the desired product but largely composed of ethylene.
  • Important components of the reactor system include the main reactor vessel, the fluidized bed, a distributor plate at the bottom of the bed, a disengagement zone above the bed, a recycle gas system, a compressor, a heat exchanger, and a product discharge system.
  • Static probes are available, for example, from Progression, Inc, and are described in US Patent Nos. 6,008,662 and 6,905,654, which are incorporated herein by reference.
  • Acoustic probes are available, for example, from vendors such as Process Analysis and Automation, LTD. These vendors provide proprietary hardware and software for measuring their probe signals.
  • Equation 1 is a summation form of a Fourier analysis technique that takes into account the imaginary components of the waveform.
  • Sp(t) a periodic function wherein t is time
  • This Fourier analysis technique converts an amplitude versus time spectrum to an amplitude versus frequency spectrum, which can then be modified using a digital filter.
  • the digital filter is another waveform with a sharp transition to zero at the maximum frequency that is desired.
  • the 5Hz trace does not follow the short time scale fluctuations which are characteristic of these phenomena.
  • the 5 Hz trace exhibits roll-off, which limits the amplitude and resolution, therefore making it unreliable for measuring particle impacts or the charge of particles passing by the probe.
  • Another type of event that has been shown to occur in the reactor and can be analyzed using these same methods on the static probe data is electrostatic discharges. Electrostatic discharges occur on a timescale of hundreds of nanoseconds requiring data acquisition rates on the order of MHz or GHz. In this case, the static probe is used more as an antenna to detect radio- frequency discharge events within the reactor.
  • a set of probes referred to as the product chamber static probes are located outside of the main reactor vessel in the product chambers. Approximately one ton of the product is discharged to the chambers in one product discharge event. The product discharge event is easily seen in the data in both plots in Fig. 2 as an amplitude change occurring between 3 and 4 minutes on these plots.
  • the static probe is located at the top of the product chamber near the opening where the particles are discharged into the chamber.
  • the uncoated static probe measures current induced on a sensing tip due to charged particles passing by and is also susceptible to triboelectric charge transfer from particle impacts with the probe.
  • the product discharge chamber probes can be coated with a dielectric coating of polyethylene to mitigate tribocharging.
  • the induced probe current due to the changing electric field generated by the charged particles entering the chamber can be measured and the charge in the chamber calculated.
  • the measured current from the static probes has units of amps. As Equation 2 indicates, the integral of current over a definite time yields the charge,
  • ⁇ permittivity of material within volume (can be approximated as ⁇ 0 for gas environment)
  • Equation 4 The specific equation for determining the radial electric field within a cylindrical reactor, and uniform charge distribution, is given below as Equation 4 (variables similarly defined as in 3 above):
  • Electric field arising from the charged resin indicates the overall charge state of the reactor.
  • the long period charge signal from the product chamber has been shown to be inversely correlated to the amount of "co-feed” or antistatic that is added to the reactor.
  • Monitoring of the average DC baseline value can also provide an indication of the average triboelectric charge transfer to the probe, which can also prove useful in detecting particle type changes, or probe coating changes.
  • Equation 4 The long-term mean is calculated using Equation 4 wherein is small but is repeated for many iterations.
  • Static probes are susceptible to charge transfer due to particle collisions.
  • the mean signal is the DC signal and is an indication of the charge transfer from particles to the probe, therefore the mean signal is interpreted as particle flux.
  • the mean can also give additional qualitative information.
  • the sign of charge transfer is dependent on the materials that collide and the environment in which they collide. In this example, the charge transferred between the static probe and the particles is a net negative as seen by the probe.
  • Fig. 3 is a plot of the inverse of the recycle line static probe mean over a period of one month.
  • the inverse of the mean is plotted in Fig. 3 to aid interpretation.
  • the black line in the plot is the base line, and when the mean signal has a sharp transition toward the baseline (opposite of normal activity, often crossing over the base line), it is interpreted as due to a poison in the reactor. This interpretation has been shown experimentally through multiple poison events in a reactor as displayed in Table 1 below.
  • a bare metal static probe in the presence of contaminants, can experience multiple physical processes, each of which results in unique signatures in probe response.
  • Contaminant species adsorbed by the colliding materials can change the sign of the triboelectric charge transfer.
  • the inhibited polymerization productivity leads to an increase in the carryover of particles from the bed. This is dominated by smaller particles. If the bed is experiencing bipolar charging, these additional particles could become positively charged, resulting in a change in sign of the probe response. In the case of contaminant species that cause additional particles to stick to the probe tip, the probe response may show an increase in unipolar charge of the opposite sign.
  • Acoustic probes measure the energy transferred from particles colliding with the reactor walls and plumbing.
  • the mean of the acoustic probe signals in the recycle line is indicative of mass flow.
  • Two acoustic probes can be employed, for example, to demonstrate feasibility.
  • the current charge state can be characterized according to the four following scenarios:
  • Scenario #1 Acoustic probe means are changing (increase or decrease) and the static probe means remains constant. Combined Interpretation: Charge state of the particles is changing.
  • Scenario #2 Acoustic probe means remain constant and the static probe means are changing (increasing or decreasing).
  • Equation 4 The variance is calculated using Equation 4, wherein, "n” is small and repeated for many iterations.
  • n length of set x
  • the time resolved variance of the static probes is the moving or fluctuating portion of the signal from the static probes. This fluctuating signal is associated with the induced charge from a changing electric field due to charged particles or bubbles passing the sensing tip.
  • the variance of the main vessel static probes correlates well with the electric field interpreted from the product chamber static integration as shown in Fig. 4. The variance of the main vessel static probes can then be interpreted as an unsealed version of the bulk electric field in the resin bed.
  • the variance of the recycle line static can be generally interpreted as the fluctuation in flow rate of charge particles and has many variables associated with its meaning.
  • the fluctuations in flow rate are caused by variables such as changes in gas flow velocity and turbulence, particle flux, and particle charge.
  • the variance of the acoustic probes is interpreted as the particle flux and average momentum transfer from particles hitting the recycle line cooler.
  • the autocorrelation of the recycle line static yields the same macroscopic information as the variance but offers more information on a microscopic scale.
  • the long term peak value of the autocorrelation is what is similar to the variance but the bipolar nature of the autocorrelation indicates that the signal is derived from particles that pass by the probe tip.
  • Equation 6 is the summation form of the cross-correlation algorithm. def ⁇
  • the location of the peak of the cross-correlation of the acoustic probes yields the transit time of the particles through the recycle line cooler.
  • the peak in Fig. 6 is located to the left or negative side of the center of the cross- correlation. This indicates that the features of the signal from the cooler inlet acoustic occur before the features of the cooler outlet acoustic signal and that they are strongly correlated at that point. The interpretation is that the same particles that transfer energy to the cooler inlet acoustic probe transfer energy to the cooler outlet acoustic probe 2 seconds later. So the transit time of particles through the cooler is 2 seconds.
  • the peak of the cross-correlation of the recycle line static with the acoustic probes yields the transit time of particles in the recycle line.
  • the cross- correlation between the recycle line static and the cooler inlet acoustic yields the recycle line gas velocity assuming the linear distance between the two probes is known.
  • the tail of the cross-correlations indicates that not all of the entrained particles travel at the cycle gas velocity.
  • the term "tail" is meant to indicate those relatively few particles that are correlated at a later time from the main population of particles.
  • the two processing schemes as shown in Fig. 8, indicate the movement of bubbles in the bed.
  • the peak of the autocorrelation yields the size of the bubbles or the distance from the probe to the bubble.
  • the offset of the two poles of the cross-correlation of main vessel static with its integral indicates the transit time of the bubbles.
  • Fluidized bed reactors with modified product discharge systems can have a greater distributor plate fouling rate than other reactors of similar size and production rate.
  • the increased plate fouling is due to the modified product discharge system's fill-line return to the top of the reactor.
  • the modified fill-line allows for pressure equalization of the product chamber resulting in better fill rates of the product discharge tanks.
  • Particles are then entrained in the gas and carried up the modified fill-line and potentially entrained into the recycle line. These entrained particles can potentially where they end up at the distributor plate where they get stuck but continue to polymerize causing them to grow and foul the distributor plate. Any increased entrainment of particles is potentially detectable on a static probe installed into the cycle gas line. However, in practice it is very difficult to see a change in the raw static probe signal on a short timescale because the variance of the data is three orders of magnitude larger than the mean.
  • Product discharge events can be used as time reference points for other analyses. For example, the front point of inflection of the peak of the integral of the product discharge static probe current signal indicates the beginning of a discharge to the product chamber. Using this as the starting point to look for increases in the short period mean value of the recycle line static and acoustic probes will determine if extra particles are entrained in the recycle line due to operation of the improved product discharge system (IPDS) or enhanced fill line.
  • IPDS improved product discharge system
  • the enhanced fill line permits gas (and tiny entrained particles) to be recycled from the product chamber to the top of the reactor.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Electrochemistry (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
  • Testing Relating To Insulation (AREA)

Abstract

La présente invention porte sur des sondes de surveillance de phénomènes électrostatiques dans des environnements difficiles, tels que des réacteurs à lit fluidisé. Ces sondes comprennent une sonde statique revêtue ou non revêtue pour mesure de champ électrique et/ou d'état de charge de particule, une sonde de champ électrique oscillant pour mesure de champ électrique, une sonde de champ électrique haché pour mesure de champ électrique, et une sonde d'antenne radiofréquence pour détection de décharges électrostatiques.
PCT/US2013/078044 2012-12-28 2013-12-27 Instruments de surveillance de phénomènes électrostatiques dans des réacteurs WO2014106078A2 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US201261746640P 2012-12-28 2012-12-28
US61/746,640 2012-12-28
US14/141,857 2013-12-27
US14/141,857 US9328177B2 (en) 2012-12-28 2013-12-27 Methods for processing and interpreting signals from static and acoustic probes in fluidized bed reactor systems
US14/142,179 US9360453B2 (en) 2012-12-28 2013-12-27 Instruments for monitoring electrostatic phenomena in reactors
US14/142,179 2013-12-27

Publications (2)

Publication Number Publication Date
WO2014106078A2 true WO2014106078A2 (fr) 2014-07-03
WO2014106078A3 WO2014106078A3 (fr) 2014-09-18

Family

ID=49998708

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2013/078044 WO2014106078A2 (fr) 2012-12-28 2013-12-27 Instruments de surveillance de phénomènes électrostatiques dans des réacteurs

Country Status (1)

Country Link
WO (1) WO2014106078A2 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104931561A (zh) * 2015-05-11 2015-09-23 西安交通大学 一种能实现高温高压水环境下声发射监测的电化学试验装置
CN110297131A (zh) * 2018-03-22 2019-10-01 中兴通讯股份有限公司 射频测试探头、射频测试系统及方法
WO2020030934A1 (fr) * 2018-08-10 2020-02-13 Envea Uk Ltd Capteur de concentration de particules
DE102021101409B3 (de) 2021-01-22 2022-05-05 Bundesrepublik Deutschland, Vertreten Durch Das Bundesministerium Für Wirtschaft Und Energie, Dieses Vertreten Durch Den Präsidenten Der Physikalischen Bundesanstalt Verfahren zum Bestimmen zumindest eines Ladungskennwerts von elektrischen Ladungen von Partikeln in einem Fluidstrom und Fluidstromladungsmessgerät

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0784637B1 (fr) 1994-10-03 1999-10-20 Exxon Chemical Patents Inc. Procede de polymerisation de monomeres sur lits fluidises
US6008662A (en) 1996-10-31 1999-12-28 Oxford Instruments America, Inc. Apparatus and method for measuring conditions in fluidized beds
WO2002006188A2 (fr) 2000-07-13 2002-01-24 Exxonmobil Chemical Patents Inc. Production de derives d'olefines
EP0970970B1 (fr) 1994-10-03 2003-12-10 ExxonMobil Chemical Patents Inc. Procédé de polymérisation de monomères en lit fluidisé
WO2004060940A1 (fr) 2002-12-26 2004-07-22 Univation Technologies, Llc Mesure et detection de charges statiques dans un reacteur a polyethylene en phase gageuse
US6905654B2 (en) 2000-10-06 2005-06-14 Univation Technologies, Llc Method and apparatus for reducing static charges during polymerization of olefin polymers
WO2005113615A2 (fr) 2004-05-20 2005-12-01 Univation Technologies, Llc Procede de polymerisation
EP1623999A1 (fr) 1993-04-26 2006-02-08 ExxonMobil Chemical Patents Inc. Procédé de polymérisation de monomères en lit fluidisé
WO2009014682A2 (fr) 2007-07-24 2009-01-29 Univation Technologies, Llc Procédé de surveillance d'une réaction de polymérisation
US7799876B2 (en) 2006-07-31 2010-09-21 Univation Technologies, Llc Method and apparatus for controlling static charge in polyolefin reactors

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4247299A (en) * 1978-06-19 1981-01-27 Johnson Controls, Inc. Non-conductive polar gas sensing element and detection system
US5315255A (en) * 1992-07-16 1994-05-24 Micron Technology, Inc. Non-contact, electrostatic, discharge detector
US5731392A (en) * 1996-09-20 1998-03-24 Mobil Oil Company Static control with TEOS
JP5164896B2 (ja) * 2009-03-12 2013-03-21 日本碍子株式会社 粒子状物質検出装置

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1623999A1 (fr) 1993-04-26 2006-02-08 ExxonMobil Chemical Patents Inc. Procédé de polymérisation de monomères en lit fluidisé
EP0970970B1 (fr) 1994-10-03 2003-12-10 ExxonMobil Chemical Patents Inc. Procédé de polymérisation de monomères en lit fluidisé
EP0784637B1 (fr) 1994-10-03 1999-10-20 Exxon Chemical Patents Inc. Procede de polymerisation de monomeres sur lits fluidises
US6008662A (en) 1996-10-31 1999-12-28 Oxford Instruments America, Inc. Apparatus and method for measuring conditions in fluidized beds
US6660812B2 (en) 2000-07-13 2003-12-09 Exxonmobil Chemical Patents Inc. Production of olefin derivatives
WO2002006188A2 (fr) 2000-07-13 2002-01-24 Exxonmobil Chemical Patents Inc. Production de derives d'olefines
EP2263993A2 (fr) 2000-07-13 2010-12-22 ExxonMobil Chemical Patents Inc. Production de dérivés d'oléfine
US6905654B2 (en) 2000-10-06 2005-06-14 Univation Technologies, Llc Method and apparatus for reducing static charges during polymerization of olefin polymers
WO2004060940A1 (fr) 2002-12-26 2004-07-22 Univation Technologies, Llc Mesure et detection de charges statiques dans un reacteur a polyethylene en phase gageuse
US6831140B2 (en) 2002-12-26 2004-12-14 Univation Technologies, Llc Static measurement and detection in a gas phase polyethylene reactor
WO2005113615A2 (fr) 2004-05-20 2005-12-01 Univation Technologies, Llc Procede de polymerisation
US7799876B2 (en) 2006-07-31 2010-09-21 Univation Technologies, Llc Method and apparatus for controlling static charge in polyolefin reactors
WO2009014682A2 (fr) 2007-07-24 2009-01-29 Univation Technologies, Llc Procédé de surveillance d'une réaction de polymérisation

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104931561A (zh) * 2015-05-11 2015-09-23 西安交通大学 一种能实现高温高压水环境下声发射监测的电化学试验装置
CN110297131A (zh) * 2018-03-22 2019-10-01 中兴通讯股份有限公司 射频测试探头、射频测试系统及方法
CN110297131B (zh) * 2018-03-22 2022-01-28 中兴通讯股份有限公司 射频测试探头、射频测试系统及方法
WO2020030934A1 (fr) * 2018-08-10 2020-02-13 Envea Uk Ltd Capteur de concentration de particules
CN112771363A (zh) * 2018-08-10 2021-05-07 Envea英国有限公司 颗粒浓度传感器
DE102021101409B3 (de) 2021-01-22 2022-05-05 Bundesrepublik Deutschland, Vertreten Durch Das Bundesministerium Für Wirtschaft Und Energie, Dieses Vertreten Durch Den Präsidenten Der Physikalischen Bundesanstalt Verfahren zum Bestimmen zumindest eines Ladungskennwerts von elektrischen Ladungen von Partikeln in einem Fluidstrom und Fluidstromladungsmessgerät
WO2022157033A1 (fr) 2021-01-22 2022-07-28 Bundesrepublik Deutschland, Vertreten Durch Das Bundesministerium Für Wirtschaft Und Energie, Procédé de détermination d'au moins une valeur caractéristique de charges électriques de particules dans un courant de fluide, et dispositif de mesure de charges dans un courant de fluide

Also Published As

Publication number Publication date
WO2014106078A3 (fr) 2014-09-18

Similar Documents

Publication Publication Date Title
US9513360B2 (en) Method for testing mainframe performance of different types of partial discharge detectors based on analog voltage signal injection
Cleary et al. UHF and current pulse measurements of partial discharge activity in mineral oil
US20160168278A1 (en) Methods for processing and interpreting signals from static and acoustic probes in fluidized bed reactors
WO2014106078A2 (fr) Instruments de surveillance de phénomènes électrostatiques dans des réacteurs
CN103913681A (zh) 一种高频电压下局部放电检测系统与方法
CN101655536B (zh) 气体绝缘组合电器局部放电检测方法
JP5854468B2 (ja) 非接触放電評価方法及び装置
Reid et al. Ultra-wide bandwidth measurement of partial discharge current pulses in SF6
Wang et al. Signal decoupling and analysis from inner flush-mounted electrostatic sensor for detecting pneumatic conveying particles
US9360453B2 (en) Instruments for monitoring electrostatic phenomena in reactors
JP5052629B2 (ja) 電気機器の標的回路内の部分コロナ放電を検出する方法
Mutakamihigashi et al. Relationship between AE waveform frequency and the charges caused by partial discharge in mineral oil
CN106932672B (zh) 一种设备辐射干扰的评估方法
CN112924555A (zh) 一种使用声发射检测移动床径向反应器状态和故障诊断的方法及装置
Jongen et al. Identification of partial discharge defects in transformer oil
JP2006208017A (ja) ガス絶縁機器における部分放電検出装置
Najafi et al. The influence of corona near to the bushing of a transformer on partial discharge measurement with an acoustic emission sensor
JP5204558B2 (ja) インパルス試験用放電計測装置及び放電判別方法
CN102590643A (zh) 气固两相管流静电测量装置及测量方法
CN112213605A (zh) 基于二氧化氮监测的电缆局部放电跟踪预警方法及系统
Wang et al. Induced and transferred charge signals decoupling based on discrete wavelet transform for dilute gas-solid two-phase flow measurement
Kasten et al. Partial discharge characteristics at low pressures in dry air and argon
Lu et al. Time domain reflectometry technique for detecting the degradation of solder joints
US7038460B1 (en) Electrostatic dust detector
Zhang et al. Diagnostics of partial discharge measurements utilizing multi-sensor temporal pulse sequence analysis

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 13822068

Country of ref document: EP

Kind code of ref document: A2

122 Ep: pct application non-entry in european phase

Ref document number: 13822068

Country of ref document: EP

Kind code of ref document: A2