HK1017922B - Method to monitor and control chemical treatment of petroleum, petrochemical and processes with on-line quartz crystal microbalance sensors - Google Patents

Description

Method for monitoring and controlling petroleum, petrochemicals and process chemical treatments with on-line quartz crystal microbalance sensors

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Introduction to the word

Specialty chemicals are needed for addition to various industrial processes, and these processes are often required to operate efficiently, beneficially, and safely. The addition of specialty chemical treatments to such processes can help, among other things, reduce process fouling, corrosion, and foaming. These treatment chemicals are added to various processes at concentrations of several ppb to several percent. The dosage of the treatment agent is often determined by monitoring the process parameters for changes during the addition of the specialty chemical. Most suitably, one skilled in the art will wish to correlate dosage with changes in the process fluid. However, the method of determining the dose is often time-consuming, since often only process parameters that change over a long period of time will change significantly. For some procedures, proper determination of the correct specialty chemical dosage may take months. Once determined, these doses are fixed at a fixed value. For example, when the rate of fouling, corrosion or blistering changes during this period, the dosage does not increase or decrease either. This often results in either excessive amounts of specialty chemicals being added, resulting in waste, or insufficient specialty chemicals being added, resulting in poor process quality.

Examples of methods for controlling the addition of specialty chemicals include coupon analysis, off-line residual product testing, residual polymer testing, on-line pH monitors, conductivity monitors, and the like. However, these methods and many others for monitoring performance and controlling dosage are generally slow and do not show real-time changes in the process. For example, residue testing typically involves taking a sample fluid from a process and performing sample analysis at some point remote from the process. In the case of on-line meters such as pH probes and conductivity monitors, many of the methods are too high in detection limits and differences to provide accurate data for controlling the addition of specialty chemicals. That is, the sensitivity of on-line instruments is often not high enough to allow an operator to adjust the dosage of a specialty chemical in real time. Therefore, in order to accurately and precisely control the addition of specialty chemicals to an industrial process, a highly sensitive in situ method that provides real-time feedback of the fluid state of the process is needed.

Quartz crystal microbalances are known for measuring the amount of fouling, deposit formation or mass loss occurring in hydrocarbon and aqueous systems. These devices function by exciting a quartz crystal in contact with a fluid (liquid or vapor) to produce a resonant frequency, and then measuring the change in resonant frequency due to the loss or accumulation of mass from or on the crystal surface. While successful in measuring the mass of hard crystalline scale or fouling deposits, we have found that conventional quartz crystal microbalance devices are an unreliable measuring instrument for many types of phenomena occurring in both aqueous and non-aqueous systems. First, conventional quartz crystal microbalances are unable to accurately measure the mass of amorphous deposits, such as those formed by biofouling or amorphous hydrocarbon deposits on surfaces of processing equipment and the like. These types of measurements performed by means of conventional quartz crystal microbalances yield inaccurate and unreliable data that cannot be used to control the chemical feed used to correct the measurement conditions.

An example of a typical quartz crystal microbalance application for measuring the amount of crystalline scale formation in aqueous systems is found in co-pending U.S. patent application 08/421,206 filed on 13.4.1995, the disclosure of which is incorporated herein by reference. Although the apparatus and process disclosed in U.S. patent application 08/421,206 operate accurately and with excellent control when only crystalline scale is formed in the system, we have found that this apparatus does not work in systems that can form amorphous scale or a combination of amorphous and crystalline scale. Furthermore, devices such as those disclosed in U.S. patent application 08/421,206 cannot be used to detect changes in a fluid such as an increase or decrease in viscosity, an increase or decrease in density, the presence of immiscible fluids, or the growth of amorphous deposits that form inside a container containing the fluid.

Accordingly, the present invention relates to a method of measuring material properties and process stream properties, more particularly to a method of measuring material viscosity and density, and even more particularly to a method of accurately and rapidly measuring viscosity and density and mass deposition in aqueous and non-aqueous systems. The method of the present invention utilizes a thickness shear mode resonator device to determine the mass accumulation, viscosity and/or density of hydrocarbon solutions, vapors and mixtures, and the mass accumulation, viscosity and/or density of aqueous fluids. By means of this method, rapid and accurate measurements can be obtained in real time and during this time, which can be used to control the addition of treatment chemicals and process variables of the system. By using a thickness shear mode resonator apparatus, crude oil and chemical processing can be greatly improved by timely and timely addition of anti-fouling agents, by improving emulsion breaking in wastewater treatment and in the breaking of crude oil emulsions, as well as in the breaking of emulsions formed in crude oil processing (e.g., desalting, breaking, and certain emulsions formed in hydrocarbon processing such as in ethylene furnace quench towers), by appropriate addition of dispersants or other additives to hydrocarbons, and by adding biocontrol chemicals or stabilizers to the finished oil. Also, thickness shear mode resonator devices can be used in aqueous systems to measure growth and deposition of organisms; inorganic or organic fouling or the apparatus may be used to measure the rate of corrosion occurring in aqueous systems or in hydrocarbon systems. Additional applications of thickness shear mode resonator devices are discussed below

Background

Quartz crystal microbalances, sometimes also called piezoelectric sensors, have been proposed for measuring the mass of material precipitated from a fluid medium, measuring the viscosity of a flowing fluid, determining the rate of film deposition, monitoring corrosion, and the like. While there are some successful examples, quartz crystal microbalances that only measure changes in resonant frequency often yield erroneous readings when used in industry under certain conditions. For example, quartz crystal crystallite balances that are effective in measuring hard, adherent scales that actually deposit on crystals or damp crystal vibrations often fail to achieve correct results when amorphous or soft scales (biological growths, amorphous inorganic crystals, etc.) are deposited on the same crystals. This is because the apparatus relies only on measuring the change in resonant frequency. Therefore, these sensors are not useful as a means of controlling the addition of treatment chemicals like biocides and anti-polymerization agents.

Thickness shear mode resonators suitable for use in the practice of the present invention are known to those skilled in the art. A particularly suitable thickness shear mode resonator is disclosed in US5,201,215 to Granstaff et al, the disclosure of which is incorporated herein by reference. The apparatus can determine the density-viscosity product of a given fluid. It should be noted that the quartz crystal portion of this thickness shear mode resonator is essentially the same as the prior art quartz crystal microbalance. It is the manner in which the signals are processed in such a way as to make the use of Granstaff thickness shear mode resonators unique, which enables these thickness shear mode resonators to do something that typical quartz crystal microbalances cannot do. The thickness shear mode resonator suitable for use in the present invention differs from a quartz crystal microbalance in the oscillator circuitry which cannot be used to measure the density-viscosity product of a given flow. The oscillator circuit of the device disclosed in US5,201,215 to Granstaff provides not only a measurement of the resonant frequency, but also a measurement of the amplitude variation of the resonant frequency, which is sensitive to the physical properties of the fluid medium in which the crystal is immersed.

A second type of thickness-shear mode resonator suitable for use in the practice of the present invention is the S.J. Mar-tin, et alSensor and actuatorA, 44(1994)209-218, the disclosure of which is hereby incorporated by reference into the present specification. Such devices use a first sensor having a rough surface and a second sensor having a smooth surface. It has been found that by using such an apparatus it is possible to determine and resolve mass deposition, fluid viscosity and density simultaneously. By using smooth and rough surfaces with different mass adhesion, it is possible to distinguish between the amount of fluid mass deposition and the viscosity and density in contact with the piezoelectric crystal of the thickness shear mode resonator.

As described in US5,201,215 to Granstaff, the mass of a solid and/or the physical properties of a fluid can be determined when the mass and the fluid are in contact with the same quartz crystal by: applying an oscillating electric field across the thickness of the quartz crystal microbalance in contact with a solid mass interposed between the quartz crystal microbalance and the electric field; measuring at least one resonant frequency of the quartz crystal microbalance; and simultaneously measuring the magnitude of the input end signal under the resonance frequency, and correlating the resonance frequency with the magnitude of the input end signal to obtain the density of the surface quality and the product of the viscosity and the density of the fluid. On the other hand, as indicated by Granstaff, the oscillating circuit may be applied through the thickness of a quartz crystal microbalance; scanning the frequency of at least one crystal resonance frequency interval region; measuring the magnitude and phase of the signal at the input end of the frequency range; correlating the input signal data with a frequency; input signal/frequency correlation is used for equivalent line patterns; contacting a solid mass and/or a fluid with the crystal, wherein the solid mass is between the crystal and the fluid; repeating the step of scanning a frequency range spaced apart by a resonant frequency; measuring the magnitude and phase of the input signal in this frequency range; correlating the input signal data with a frequency; then the input end signal/frequency association is used for the equivalent line mode; the product of solid mass and fluid density-viscosity is then derived from the correlated input signal/frequency data.

While Granstaff et al disclose that the mass layer can be a metal, metal alloy, salt, some hard polymer or ice, and that these solids can be evaporated, plated, deposited or otherwise chemically or thermodynamically reacted onto the quartz crystal microbalance, Granstaff et al are unaware that this method can be effectively used in hydrocarbon processing or water treatment applications, or that the apparatus can be effectively used in such applications to control the addition of process additives.

However, we have found that certain types of quartz crystal microbalances substantially as described by Granstaff can be used to overcome those disadvantages of the prior art quartz crystal microbalance devices and provide accurate and instantaneous data for controlling chemical feeds for controlling or improving both aqueous and non-aqueous processes.

Accordingly, one embodiment of the present invention provides to the art a method for controlling chemical additives to hydrocarbon processing and water treatment processes by using a thickness shear mode resonator apparatus.

Another embodiment of the present invention provides to the art an accurate and real-time method of controlling the feed of chemical additives to hydrocarbon processing and water treatment processes.

Another embodiment of the present invention provides to the art an accurate and real-time method of controlling the feed of condition correcting chemical additives to hydrocarbon processing and water treatment processes.

Further embodiments of the invention will become apparent hereinafter.

The invention

The basic method of the present invention involves the use of a thickness shear mode resonator device, such a device being mounted where the quartz crystal surface of the device can be in contact with the fluid used herein, which may be a liquid or a vapor (gas); measuring the mass and viscosity-density output of the fluid; determining the condition of the system; and adding treatment chemicals, or taking other corrective action as mass and fluid viscosity-density output instructions. The thickness shear mode device may be mounted on the surface of a container for such fluids, or may simply be inserted into the fluid. Where the apparatus is temporarily or permanently inserted into a fluid, it is imperative to ensure that a representative fluid contacts the surface of the quartz crystal. The thickness shear mode resonator device is preferably inserted at the surface of a vessel containing the fluid. The term vessel refers to a line, tank or any other device that contains a fluid.

The invention is suitable for determining the properties of aqueous and non-aqueous systems. The main applications of the invention are the determination of scaling, corrosion and biofouling in aqueous systems, the determination of organic fouling and corrosion in hydrocarbon processes, and the determination of the rate of emulsion breaking of water-in-oil and oil-in-water emulsions, the determination of fluid properties such as viscosity, density, solids content, etc., the amount of sediment present in a tank or container and the rate of sediment present. As noted, these are merely some examples of the application of the present invention in the fields of water treatment and hydrocarbon processing.

The term "water treatment" as used herein refers to the prevention of inorganic scaling, corrosion and biofouling on surfaces in contact with a water supply-or industrial water system. As mentioned above, the present invention is particularly useful for determining the rate of biological growth occurring in aqueous systems. Also included in the term "water treatment" as used herein is the meaning of chemically and/or mechanically separating solids from fluids, either as steam or as liquids, and chemically and/or physically separating oil from water. As used herein, the term "hydrocarbon processing" refers to the transportation of crude oil through pipelines, railways, barges, or storage tanks and the processing of crude oil into various useful products by various methods: including desalination processes, distillation, cracking, and other processes for producing marketable products, and further processing of such hydrocarbon products in the chemical processing industry, including the production of such valuable materials as styrene, butadiene, isoprene, vinyl chloride, ethylene, propylene, acrylonitrile, acrylic acid, alkyl acrylates, and polymeric materials derived from these materials. In practice, the invention may be used in any situation where it is desirable to know the rate at which organic fouling is generated on the surfaces of heat exchange equipment, flow lines, storage tanks, and the like. To implement the method of the present invention, the thickness shear mode resonator can be installed at any of the following locations in the process: where organic fouling, inorganic fouling, corrosion or microbial growth is expected, or where changes in fluid properties may indicate that a processing problem exists that can be corrected by the addition of chemical treatments. Also, the present invention can be used to determine the rate at which an emulsion breaks, or to determine the conditions of an emulsion in real time, so that the appropriate breaking material can be added (and conversely, if the emulsion is the desired product, the emulsifier is added). Because the use of the present invention can provide real-time data to rapidly and accurately control scaling, fouling, microbial growth, etc. in an unprecedented manner. Other techniques are not known to the inventors at this point that provide both instantaneous, real-time mass deposition and fluid property data for controlling the feed of water treatment chemicals and/or hydrocarbon processing chemicals.

In a broad sense, the present invention is a method of determining the conditions of a fluid present on the surface of a container containing such fluid and taking various steps to correct such conditions either instantaneously or subsequently, the method comprising the steps of:

A. placing the thickness shear mode resonator device in a container and contacting a quartz surface of the thickness shear mode resonator device with a fluid;

B. continuously exciting the thickness shear mode resonator device, and measuring the frequency change and the damping voltage component output by the thickness shear mode resonator device;

C. continuously determining the condition of the surface of the thickness shear mode resonator device based on the frequency variation and the damping voltage component; and

D. continuously correcting the conditions detected on the surface of the thickness-shear mode resonator device by taking one of the following actions:

i starting or stopping a chemical feed pump that feeds a conditioning chemical into the fluid;

ii increasing the fluid flow rate out of the system; or

iii reducing the fluid flow rate out of the system.

While the frequency alteration and damping voltage components as the output of the thickness-shear mode resonator can be used directly, it is often suitable for converting this data into mass and viscosity-density components. As mentioned above, the thickness shear mode resonator device may be placed in the vicinity of the surface of a container holding the fluid, or may be inserted anywhere in the container where the fluid is in contact with the quartz crystal surface of the thickness shear mode resonator device. The vessels used may preferably be hydrocarbon processing units, hydrocarbon storage tanks, pipelines or transport vessels, such as barges, ships and rail cars.

Further, while the thickness shear mode resonator device of the present invention may be permanently placed in the system, such a device may also be temporarily placed in the system to determine if a fluid condition correction chemical should be added.

Although suitable for correcting conditions on surfaces in contact with fluids, the present invention can also be used to control the conditions of the fluid itself in a liquid or gaseous state and to adjust the conditions of the fluid such as consistency, viscosity, etc. In a broad sense, the present invention relates to determining fluid conditions in a fluid manufacturing process, including storage or transport of said fluid, and taking various steps to correct such conditions on-the-fly, including:

A. inserting a thickness shear mode resonator device into a container containing the fluid, such that a quartz surface of the thickness shear mode resonator device is in contact with the fluid;

B. continuously exciting the thickness shear mode resonator device, and measuring the frequency change and the damping voltage component output by the thickness shear mode resonator device;

C. continuously measuring the surface condition of the thickness shear mode resonator device on the basis of the frequency variation and the damping voltage component;

D. the following operations are taken to continuously correct the detection conditions on the surface of the thickness shear mode resonator device:

i starting or stopping a chemical feed pump that feeds a chemical for condition correction into the fluid;

ii increasing the fluid flow rate out of the system; or

iii reducing the fluid flow rate out of the system.

To describe the invention in another way, the basic invention described in this application works in a water treatment system by employing the following steps:

A. inserting a thickness shear mode resonator device into water, preferably on a surface of a container holding such water, such that a quartz surface of the thickness shear mode resonator is in contact with the industrial water;

B. continuously exciting a thickness-shear mode resonator device and measuring the mass and viscosity-density components output by the thickness-shear mode resonator device;

C. continuously measuring the conditions on the surface of the thickness shear mode resonator device on the basis of the mass and viscosity-density components;

D. continuously correcting conditions detected on the surface of a thickness shear mode resonator device by taking the following actions:

i starting or stopping a chemical feeding pump for feeding chemicals for condition correction into the industrial water system;

ii increasing the flow rate of water out of the system; or

iii reducing the flow rate of water out of the system.

Although in the above description the thickness shear mode resonator device is used in a single form, in certain systems it is often desirable to use a plurality of thickness shear mode resonator devices. Thus, a single form of a single thickness shear mode resonator, as used herein, includes one, two or more thickness shear mode resonator devices. This allows for other controls of the system. The use of multiple thickness shear mode resonator devices is particularly important when the device is used for the purpose of determining sediment in a storage tank, demulsification efficiency, height of foam in a vessel, height of each of two or more distinct phases in a vessel, and the like.

The use of the present invention provides a real-time determination of parameters affecting aqueous systems. In this way, scale, corrosion or biofouling can be detected visually in the system and scale formation, corrosion or biofouling can be detected long before other measurements provide the same information. Due to the sensitivity of the thickness shear mode resonators, various problems occurring in the system can be detected much earlier than in conventional methods, which can be controlled in real time by corrective action using suitable scale or corrosion inhibitors or biocides. By using the method of the invention to rapidly control the system, the industrial system can be well controlled. By using thickness shear mode resonator equipment in the method, accurate control of the aqueous treatment system can be achieved. The thickness shear mode resonator may also function in real time to avoid problems associated with chemical feed based sampling tube analysis, which has complicated sampling. Such monitoring does not indicate the condition at which the abnormality occurs.

In non-aqueous systems, such as in hydrocarbon processing plants, the present invention can determine, on a real-time basis, fouling, corrosion and/or biological growth conditions present on the surfaces of the hydrocarbon processing plant that are contacted by the hydrocarbon fluid (liquid or gas) contained within the hydrocarbon processing plant, and can immediately take various steps to correct such conditions. These steps include:

A. placing the thickness shear mode resonator device in a fluid contained in a hydrocarbon processing apparatus such that the quartz surface of the thickness shear mode resonator is in contact with the hydrocarbon;

B. continuously exciting a thickness shear mode resonator device and measuring mass and viscosity-density components;

C. continuously measuring the conditions on the surface of the thickness shear mode resonator on the basis of the mass and viscosity-density components;

D. the conditions detected on the surface of the thickness shear mode resonance instrument are continuously corrected by starting or stopping a chemical feed pump that delivers the condition correcting chemical to the hydrocarbon processing plant.

Also due to the sensitivity of the method, fouling and scaling can be detected at very low levels, and therefore corrective action is taken immediately before major problems arise. Although, as mentioned above, the thickness shear mode resonator device is preferably placed on the surface of the hydrocarbon processing apparatus such that the quartz crystal of the thickness shear mode resonator is in contact with the fluid, it is only important in the broad sense of the present invention that the quartz crystal surface of the thickness shear mode resonator device be in contact with the fluid to be measured. By using the process of the present invention, it is expected that major problems such as deposition of bitumen on the surfaces of heat transfer equipment in refineries will be noticed before they become severe, or even before life-threatening problems such as uncontrolled exothermic polymerization in monomer storage tanks occur. It should be noted that these are merely examples of the process of the present invention and that other areas of applicability to the present invention will be readily apparent to those skilled in the art of hydrocarbon processing, crude oil production and processing, refining and petrochemical production. Hydrocarbon processing facilities to which the process of the present invention can be applied include almost any crude oil processing facility, or a facility for distillation to produce fuels or petrochemicals. The apparatus may be a compressor, reboiler, heat exchanger, purification column, storage vessel or reactor. Likewise, the present invention can be used in virtually any hydrocarbon processing apparatus, including those downstream apparatus that process olefins and acetylenes (e.g., ethylene, propylene, styrene, acrylonitrile, acrylic acid, alkyl acrylates, vinyl chloride, butadiene, and isoprene) and further process olefins and acetylenes. Controllable chemical additives include scale and corrosion inhibitors, anti-fouling agents, anti-foaming agents, anti-polymerization agents, and the like. It should be apparent that the present invention is not limited to any particular type of specialty chemical additive to any particular process.

The present invention may also be used to determine the viscosity, density or viscosity/temperature conditions of the hydrocarbon fluid in the vessel and immediately take various steps to correct or correct such conditions. The steps used include:

A. inserting a thickness shear mode resonator device into a vessel containing such a hydrocarbon such that the quartz surface of the thickness shear mode resonator device is in contact with the hydrocarbon;

B. continuously exciting a thickness shear mode resonator device and measuring mass and viscosity-density components;

C. continuously determining the condition of the hydrocarbon fluid on the basis of the mass and viscosity-density components;

D. a chemical feed pump for delivering a conditioning chemical into the hydrocarbon fluid contained in the vessel is activated or deactivated.

This approach is useful, for example, for processing diesel or other fuels that require the addition of pour point depressants to maintain proper flow or additives such as viscosity index improvers or other additives that modify the properties of the hydrocarbon fluid. Also, as in aqueous systems, the present invention can be used to determine the presence and height of foam during processing, and to feed antifoam into processing systems.

The invention may also be used to add demulsifiers (or conversely emulsifiers) to oil-in-water or water-in-oil emulsions, such as those obtained in waste oil treatment, refinery desalters, wastewater treatment, and the like.

In this process, two or more typical thickness shear mode resonator devices of the present invention are typically placed at different heights in the vessel where the emulsion is located. The different fluid properties, which typically comprise two or more immiscible fluids, can be read using multiple thickness shear mode resonators, and the accumulated data describes the state of the emulsion at any particular level in such a vessel or tank. Since the water, oil and any intervening layers have different viscosities and densities, the progress of the emulsion breaking can be tracked and the emulsion breaker can be added based on mass, viscosity and density measurements obtained using a thickness shear mode resonator. Methods for determining the conditions of hydrocarbon/aqueous fluid mixtures and for adding demulsifiers to such systems generally include the steps of:

A. inserting a thickness shear mode resonator device into a vessel containing a hydrocarbon/aqueous fluid mixture, such that a quartz surface of the thickness shear mode resonator device is in contact with the hydrocarbon/aqueous fluid mixture;

B. continuously exciting a thickness shear mode resonator device and measuring mass and viscosity-density components;

C. continuously determining the conditions of the hydrocarbon/aqueous fluid mixture on the basis of mass, viscosity and density components;

D. the strips of hydrocarbon/aqueous fluid mixture are continuously calibrated by starting or stopping the chemical feed pump that delivers the conditioning chemicals to the processing unit containing the hydrocarbon/aqueous fluid mixture.

While this embodiment may be practiced with only one thickness shear mode resonator placed at a level in the vessel where it is desired to measure the presence of the phase, it is often suitable to use two or more thickness shear mode resonators placed at different levels in the vessel or tank to determine the state of the fluid at each measured level. In the most preferred manner of carrying out this embodiment of the invention, at least two devices are used, one of which is preferably at the location where the presence of the aqueous phase is determined and at least one of such devices is at the location where the presence of the hydrocarbon phase is determined. Another device may be used at this level where a mixed phase or interface between two immiscible fluids occurs. The hydrocarbon/aqueous fluid mixture to be treated is generally in a vessel selected from: the system comprises a crude oil demulsifying device, a crude oil heating processor, a crude oil desalting device, an ethylene quenching water tower, a dilution steam generation system, a hydrocarbon storage tank, a hydrocarbon transportation container, a wastewater purifier, a wastewater treatment device, a settling tank, an oil collecting tank and a metal processing liquid tank. The use of more than one thickness shear mode resonator allows the demulsifying operator to obtain real-time information about the emulsion state and the feed of demulsifiers or other chemicals into the emulsion for correcting control conditions. Mixtures in the above sense are meant to include water-in-oil emulsions, oil-in-water emulsions, mixed layers of emulsions, separate oil and separate water layers and dispersions of solids in liquids.

While this method is suitable for emulsion breaking, it is of course possible to produce an emulsion. By using the density-viscosity readings obtained from the thickness shear mode resonator apparatus, emulsifiers can be added to produce an emulsion having the desired characteristics.

As can be seen, each of the embodiments of the invention described herein utilizes a thickness shear mode resonator. In using a thickness shear mode resonator to determine the amount of fouling, fouling and/or corrosion that occurs, the thickness shear mode resonator is mounted such that the exposed surface of the quartz is in direct contact with the fluid circulating in the system. In designing such systems, it is important to take into account the turbulence of the fluid caused by the insertion of the thickness shear mode resonator. Thus, when measuring fouling, scaling, corrosion, or even viscosity or other characteristics of a fluid, it is often beneficial to mount the thickness shear mode resonator flush with the surface of the vessel or pipe through which the fluid flows. The optimum location of the thickness shear mode resonator can be readily determined by one skilled in the art when a flush mounting is not possible or where the thickness shear mode resonator cannot be mounted flush with the surface of a vessel or pipe through which the fluid flows. In all installations it is important that the exposed portion of the quartz surface of the thickness shear mode resonator be in contact with the fluid to be measured or the fluid from which the scale or fouling is deposited.

In another embodiment of the present invention, a portable thickness shear mode resonator may be used. In its simplest form, the portable clamp is easily inserted into a fluid, or headspace of a tank, kettle or open vessel.

The quartz crystal surface of the thickness shear mode resonator of the present invention may be as small as desired or may be as large as is practical. The quartz crystal microbalances required to make thickness shear mode resonators suitable for use in the practice of this invention are available in various sizes and from a variety of commercial sources. One of the features of the present invention is that the thickness shear mode resonator can quickly and accurately determine conditions and change parameters that control such conditions. The present invention can be used for various pressures and temperatures. When used at high pressures, it is preferred that the pressure on both sides of the quartz crystal is equal. When only one side of the crystal is subjected to high pressure, the crystal may deform, making the reading inaccurate. Also, the present invention is applicable to a wide range of temperatures, from well below freezing to temperatures as high as the melting point of the wire bonds used to receive signals from the quartz crystal. Thus, although the apparatus is not used directly in, for example, the hot cracking section of an ethylene furnace, the apparatus can be used at the exit of the furnace. In many applications of thickness shear mode resonators, special mention should be made of controlling the addition of specialty chemical materials for improving or harmonizing the measurement conditions, such as starting or stopping pumps containing biocides, corrosion inhibitors, scale inhibitors, fouling inhibitors, etc. It is well known in the art to develop methods for controlling the pump's circuit board with the output of a thickness shear mode resonator device. Such a circuit board uses such signals as corrected measurements of the desired signal level obtained by the thickness shear mode resonator device to drive such a pump. In addition to driving the pump, the signal may also be used to open or close a discharge valve in the case of a cooling water or boiler water system, or to increase or decrease the flow rate of hydrocarbon fluid through a system, increase or decrease the residence time of an emulsion contained in a vessel in which demulsification is desired, and the like.

In the operation of a thickness shear mode resonator for use in the present invention, an oscillating circuit is utilized to maintain a constant potential across the piezoelectric crystal (quartz crystal) to provide stable oscillation. The output is measured and processed according to the general principles disclosed in US5,201,215, previously incorporated by reference.

While the use of raw data obtained from a Granstaff device and processed to obtain calculated mass and viscosity-density results is the presently preferred mode of use of the invention, the "raw data" output, frequency variation and damping voltage obtained using the lines described by Granstaff or the lines described in US5,416,448 of Wessendorf, the disclosure of which is incorporated herein by reference, are also measures of the changes that occur on the sensor surface and can be used directly without conversion to physical property values. This technique may be particularly useful in situations where accurate mass or fluid property results are difficult to obtain. In these applications, empirical observations of frequency and voltage output can be used to control chemical addition.

This raw data is of course also a measure of the viscosity-density and mass components of the fluid in contact with the piezoelectric device, and the invention includes controlling the specialty chemical process using the raw frequency change and voltage data or using the viscosity-density and mass components calculated from the raw data.

Examples

Acrylonitrile is generally recovered from the gaseous effluent of a catalytic reactor by water extraction in a column commonly referred to as an absorber column. Hydrogen cyanide and acrylonitrile are selectively extracted from the effluent, and the mixture is boiled at the top of the recovery column and passed through a series of columns where the acrylonitrile is separated as a pure component by a series of distillations. In the stripping column, the residual organic matter is removed by distillation from the stream at the bottom of the recovery column and, in this recycling process, the majority of the remaining water is returned to the absorption column. The efficient operation of the recovery process is limited by fouling that occurs in the process, particularly on heat transfer equipment such as reboilers, heat exchangers and distillation columns. This problem can be alleviated by the addition of commercially available specialty chemical antifoulants. The addition of an antifoulant in an amount of 0.001-1000ppm to the process significantly slows the rate of fouling of the process, thereby extending the operating time of the plant, reducing the number of periodic equipment cleanings and increasing the throughput of the plant. The rate of application of the anti-fouling agent to such devices is now determined based on laboratory tests or empirical data on the number of days a device can be operated continuously with a given dosage of anti-fouling agent. In practice, if the heat exchanger run time is too short due to fouling, the dosage of the anti-fouling agent is increased until an acceptable run time is reached, or there is no fouling. This process often uses an excessively large dose of the anti-fouling agent because the dose of anti-fouling agent is maximized for the worst possible conditions, rather than based on actual fouling conditions in the device. There is no in-situ, on-line, real-time method for determining optimal antifoulant dosages.

To monitor the dosage of the anti-fouling agent, quartz crystal sensors of the type described herein are installed at important locations in the acrylonitrile purification process. Typical locations for the thickness shear mode resonator installation include in the solvent water stream just prior to the heat exchanger. This sensor is mounted so that it extends into the solvent water stream. The crystal is driven with an oscillating circuit on the outside of the tube wall. The oscillator and crystal are connected by a gas tight radio frequency circuit on the outside of the tube wall. The oscillator provides a frequency and an amplitude output. The change in resonant frequency is indicative of a change in mass and/or a change in fluid properties at the crystal surface. The change in amplitude is a reflection of the crystal damping. A measurement of crystal resistivity may be a particularly useful measurement because damping is affected by the viscoelastic properties of the deposit, which may be highly viscoelastic during acrylonitrile processing. Viscoelastic deposits in the acrylonitrile process would prevent the use of other quartz crystal microbalance sensors that cannot eliminate the effects of viscoelasticity. Since the resonant frequencies are each sensitive, damping is also important in order to resolve the change in mass from the change in fluid properties. Conventional quartz resonator sensors do not meet this requirement because these devices are sensitive only to changes in the resonant frequency. The sensor used here is suitable for controlling this process, since the associated oscillating circuit is sensitive to both variations in the resonance frequency and variations in the amplitude (damping voltage).

The oscillator output was measured in a sensor placed in the solvent water line using a frequency meter and a voltage meter, both connected to a personal computer. Other measurements collected include time and temperature. Using the output of the oscillator, a computer can be used to calculate and map the mass accumulation rate on the crystal surface. This rate is measured prior to the antifouling agent injection process and the deposition rate in the untreated solvent water is proportional to the fouling rate in the heat exchanger. This rate is continuously monitored during the time the anti-fouling agent is injected into the system. The dosage of the anti-fouling agent is then adjusted until the rate begins to change. This is shown on a computer by the change in slope of the line plotted against time by the deposition mass. Finally the dosage of the anti-fouling agent can be slowly adjusted until the slope of this line is zero (no detectable deposit over a certain time interval) in order to obtain an optimal anti-fouling agent dosage. The optimal dose is determined by actual real-time measurements rather than by non-selectable variables that are susceptible to other process parameters. At any time during the operation, if the deposition increases, the rate of the anti-fouling agent will increase to compensate for the higher fouling rate.

As an alternative to placing the thickness shear mode resonator in the solvent water stream, a small slip stream withdrawn from the acrylonitrile recovery process may be used. In some cases, it is expected that the entire deposition of the solid in bulk solvent water will overwhelm the thickness shear mode resonator. To reduce the large flow rate and fouling rate, a small stream of solvent water was diverted into a fluid vessel equipped with a thickness shear mode resonator. The amount of solids deposited from the slipstream is directly proportional to the amount deposited from the bulk solvent water, provided that process parameters such as temperature and pressure are maintained. To simplify these strips, the fluid container may be heated with a heating rod, a heating trap, steam, or other conventional means. In addition, a back pressure regulator may also be added to the slipstream conduit to maintain a constant pressure. In this case, the thickness shear mode resonator in the fluid vessel would be connected to the oscillator line outside the fluid vessel and slipstream conduit. The oscillator output was used to calculate the deposition rate and optimize the antifouling agent feed as described above.

It will be apparent to those skilled in the art that a microprocessor may be substituted for components such as a voltmeter and a frequency meter. The microprocessor makes the device more convenient to operate and enables the use of a data logger and portable computer. In this case, the output of the microprocessor interfaces with a portable computer or data logger. In another possible variation, the computer is used to automatically control the piston stroke of the pump during the addition of the anti-fouling agent to the acrylonitrile. The computer is programmed to adjust the piston stroke of the pump in a manner proportional to the change in the deposition rate of the solid on the crystal surface. When the fouling rate drops to zero, the computer instructs the pump to either keep its existing pump piston stroke unchanged or reduce the pump piston stroke by a certain percentage. In this way, the dosage of the chemical antifoulant will be automatically optimized.

Thickness shear mode resonators are also useful for controlling antifoulants sent to other hydrocarbon processing operations. As another example, this hypothetical example discloses a thickness shear mode resonator for use in controlling an antifoulant added to the caustic wash system of an ethylene plant.

In an ethylene plant, so-called acid gases such as carbon dioxide and hydrogen sulphide are removed from the hydrocarbon mixture by washing the gaseous hydrocarbons with an aqueous alkali solution. This operation is typically accomplished in a unit known in the process as a caustic tower. Caustic towers are prone to fouling due to base-catalyzed polymerization of reactive aldehydes such as acetaldehyde. Fouling in caustic towers and related equipment can be controlled by using commercially available antifouling agents. In most cases, there is no easy way to determine the optimal antifouling agent dosage required to reduce the fouling to an acceptable level or eliminate the fouling. In some cases, i.e. unsatisfactory, it is attempted to determine the dosage of the antifoulant on the basis of the amount of aldehyde fed to the caustic tower. In one possible configuration, a thickness shear mode resonator is installed in the fluid at the bottom of the column. The measured amount of solids in the bottoms is an indication of the amount of fouling formed during the hydrocarbon gas wash. The response values obtained from the sensors are used to set the optimum dosage of the caustic tower antifoulant required to eliminate fouling in the caustic tower. The optimum antifoulant dosage will be determined when little or no solids are detected in the bottoms stream.

The following hypothetical example describes the use of thickness shear mode resonators to control fouling in the processing of a light hydrocarbon stream.

In the recovery of light hydrocarbons in ethylene plants, butadiene plants, isoprene plants, and the like, distillation columns and associated equipment such as heat exchangers and reboilers foul by thermal and/or oxidative polymerization of reactive olefins such as butadiene. By placing a thickness shear mode resonator device suitable for use in the present invention below a selected tray in the vapor space, column, the generation of fouling from the vapor phase can be detected with a probe. Traditionally, before polymer fouling (often referred to as "popcorn polymer") damages the metal components within the tower, it is a difficult problem to detect it. Popcorn polymer grows from the vapor phase on the metal surfaces inside the column. The thickness shear mode resonator can be placed in the vapor space of a column, such as the vapor space of a main fractionation column, a depropanizer column, a debutanizer column, and a butadiene purification column. Thickness shear mode resonators are sensitive to the formation of viscoelastic polymers deposited on the resonator in the vapor phase. The deposition of the fouled viscoelastic film was detected by the above-mentioned oscillation circuit. If the formation of scale on the crystals is detected, the dosage of the vapor phase antifoulant should be adjusted accordingly. In this way, the correct amount of anti-fouling agent required to control vapor phase fouling can be determined.

The hydrocarbon recovery column also fouls in the liquid or gas phase. The placement of the thickness shear mode resonator described above into the liquid column bottom facilitates the detection of solids deposited in the column bottom and associated reboiler. These sensors can be used to control the amount of anti-fouling agent added to the column bottom and reboiler. These additives are generally different from additives added to control vapor phase fouling, although fouling is generally similar and insoluble in the viscoelastic polymers of the liquid hydrocarbons.

Sometimes, the foulants are carried into the column from other sources. The addition of pyrolysis gasoline to the main fractionation column is now investigated. In some cases, the spent lye is washed with pyrolysis gasoline from which benzene is removed prior to disposal of the spent lye. After separation of the pyrolysis gasoline from the lye, the pyrolysis gasoline is sometimes used as reflux for the main fractionator. During the washing process of the waste alkali liquor, the aldol condensation polymer is generated through the base-catalyzed polymerization of phenylacetaldehyde and other reactive carboxyl species in the pyrolysis gasoline. Any soluble gums formed during this process are carried into the main fractionation column where some of the gums are deposited onto the metal components in the main fractionation column. The build-up of gum in the main fractionation column fouls the column. The pyrolysis gasoline from the benzene stripper was found to contain up to 1 gram of gum per 100 ml of gasoline. Commercially available dispersants can be added to the gasoline to help control the deposition of gums in the main fractionator. The thickness shear mode resonator apparatus of the present invention installed in the process piping in the reflux return column can be used as an indication of the amount of gum in the pyrolysis gasoline reflux. The response of the sensor can be used to determine the appropriate anti-fouling agent dosage required to disperse the gum in the tower. The sensor is responsive not only to the deposition of gums on the crystal surface, but also to changes in the viscosity of the pyrolysis gasoline due to the level of soluble gums in the liquid.

As described above, thickness shear mode resonators can be used to monitor the growth of biofilm or "soft" deposits that cannot be measured with previously known quartz crystal microbalance devices. Applications of aqueous systems that can be monitored with thickness shear mode resonators include pulp and paper processes where microbial growth can cause problems, cooling water systems where bacterial and algal growth can cause serious problems, and certain wastewater treatment systems. The invention can also be an improved method for other systems of wastewater demulsification, oil phase separation from water phase and direct detection of different densities of liquid by using thickness shear mode resonance instrument equipment. Because the thickness shear mode resonator device is not in line with previously known devices, both mass loading and fluid property changes, such as density and viscosity, can be measured simultaneously, and side-stream sampling using the thickness shear mode device can be accurately used to monitor the microbial fouling process in real time. The output of the thickness shear mode resonator is directly related to the growth of the biofilm and can thus be used to control the chemical feed pump. Suitable control algorithms can be developed which will ensure that the growth rate of the film is still within acceptable limits. In the absence of a thickness shear mode resonance device, cuvette sampling analysis is the only direct measurement technique available. However, the tube sampling analysis requires a complicated sample to be obtained in the period, and cannot report timely when the system is abnormal. These abnormal conditions can be rapidly controlled by varying the dose of the chemical treatment agent using real-time monitoring provided by a thickness shear mode resonator.

Also, in the cooling tower, there are both inorganic fouling deposits and microbial fouling. The ability to measure and distinguish between these two fouling regimes enables the cooling tower process to be optimised. The thickness shear mode resonator described herein (as described in US5,201,215) describes an instrument that can simultaneously measure the mass build-up and the change in the product of fluid density-viscosity. The difference in these two properties allows the appropriate dosage of the chemical and biocidal treatment to be optimised for the anti-fouling treatment.

The ability to measure the viscosity of the sample on-line enables control of the addition of viscosity modifiers to the slurry in real time. Viscosity modifiers are added to slurries used in precious metal processing to reduce the energy consumption of pumping equipment. The process of the present invention enables the on-line control of the addition of these treatment chemicals using the sampling and control techniques described above.

As an example, the thickness shear mode resonator is mounted on the wall of the paper machine in contact with the furnish used. The thickness shear mode resonator will correct the response value for the increase in mass of the biofilm present on the quartz crystal surface. When a biofilm is deposited on the surface of the quartz crystal, the thickness shear mode resonator emits a signal indicative of the biofilm. This signal is amplified and the pump delivering the water-soluble microbiocide product is activated. The feeding of biocide continues as long as the mass of the deposit increases; and when the quality of the deposit decreases or remains unchanged, the feed is stopped. In a similar manner, the viscoelastic properties of the biofilm can also be used to monitor biofilm fouling. By another approach, the paper machine can be kept substantially free of biological growth. Due to the sensitivity of the thickness shear mode resonator, the biocide can be added at a rate necessary to achieve the goal of reducing biological growth and reducing chemical overdosing. This reduces the consumption of chemicals.

A thickness shear mode resonator was mounted on the wetted inside wall of an industrial cooling tower. The thickness shear mode resonator will correct the mass deposition exhibited on its surface and amplify the signal and connect to a pump that supplies a commercial biocide. A pump feeds the biocide material to the cooling tower. As the microorganisms grow, as evidenced by changes in mass or viscoelasticity of the sample, the thickness shear mode resonator delivers a signal indicative of the production of the microorganisms, and the pump is activated to begin delivery of biocide. When no further increase or a decrease is seen, the biocide feed will be stopped. By using this system, a clean cooling tower is obtained, during which the biocide is consumed less and the emissions are less.

The examples set forth herein are not intended to be inclusive of all applications to which the sensor of the present invention may be applied. One skilled in the art will readily recognize that in addition to measuring the fouling rate of a hydrocarbon system and controlling such fouling, the sensors may be used in a variety of applications, such as measuring the rate of demulsification in a desalter and real-time control of demulsifier feed, the rate at which biocides are delivered to the finished product, and the rate at which chemical treatment agents are added to the hydrocarbon stream in order to maintain fluidity and prevent fouling.

Claims (25)

1. A method for rapidly determining scaling, corrosion or biological growth conditions present on surfaces in contact with industrial water contained in an industrial water system and taking various steps to correct such conditions, the method comprising the steps of:

A. inserting a thickness shear mode resonator device into the industrial water, thereby contacting the quartz surface of the thickness shear mode resonator device with the industrial water;

B. continuously exciting the thickness-shear mode resonator device and measuring the output of the thickness-shear mode resonator device, i.e. the mass and viscosity-density component of the industrial water in contact with the thickness-shear mode resonator device;

C. continuously determining the condition of the industrial water in contact with the quartz surface of the thickness shear mode resonator device based on the mass and viscosity-density components of the industrial water;

D. continuously correcting the condition of said industrial water in contact with the quartz surface of the thickness-shear mode resonator by taking a measure selected from the group consisting of;

(i) starting or stopping a chemical feed pump that feeds chemicals for condition correction into the industrial water;

(ii) increasing the water flow rate out of the system; or

(iii) Reducing the water flow rate out of the system.

2. The method of claim 1, wherein the industrial water system is a cooling tower.

3. The method of claim 1 wherein the condition monitored in the industrial water in contact with the quartz surface of the thickness shear mode resonator apparatus is biofouling and the chemical feed pump adds a biocide or a biocide to the industrial water.

4. The method according to claim 1, characterized in that the industrial water system is an industrial boiler.

5. The method of claim 1, characterized in that the condition of the monitored industrial water is selected from the group consisting of inorganic scale, corrosion and biofouling, and the chemical feed pump adds one or more treatment chemicals selected from the group consisting of water-soluble scale inhibitors, biocides and corrosion inhibitors.

6. The method of claim 1, wherein the quartz surface of the thickness shear mode resonator device is mounted flush with the surface of the industrial water system, whereby the quartz surface of the thickness shear mode resonator device and the industrial water channel are contacted by the mounting.

7. The method of claim 1, wherein the quartz surface of the thickness shear mode resonator device is temporarily inserted into an industrial water system.

8. A method for rapidly determining fouling, corrosion, scaling or biological growth conditions present on surfaces of a hydrocarbon processing apparatus in contact with a hydrocarbon fluid and taking steps to correct such conditions, the method characterized by:

(A) placing the thickness shear mode resonator device in a fluid contained in a hydrocarbon processing apparatus such that the quartz surface of the thickness shear mode resonator device is in contact with the hydrocarbon;

(B) continuously exciting the thickness-shear mode resonator device and measuring the output of the thickness-shear mode resonator device, i.e. the mass and viscosity-density components of the hydrocarbon fluid in contact with the thickness-shear mode resonator device;

(C) continuously determining the condition of the hydrocarbon fluid in contact with the quartz surface of the thickness shear mode resonator device based on the mass and viscosity-density components of the fluid;

(D) the condition of the hydrocarbon fluid in contact with the quartz surface of the thickness shear mode resonator device is continuously corrected by starting or stopping the chemical feed pump that feeds hydrocarbon fluid condition correcting chemicals to the hydrocarbon processing plant.

9. The process of claim 8 wherein the hydrocarbon processing equipment is a compressor, reboiler, heat exchanger, purification column, storage tank or reactor and the chemical feed pump provides the fouling inhibitor.

10. The method of claim 8, wherein the hydrocarbon processing equipment is selected from the group consisting of hydrocarbon processing units that produce olefins and acetylenes, and the chemical feed pump provides one or more components selected from the group consisting of fouling inhibitors, corrosion inhibitors, and defoamers.

11. The method of claim 10, wherein the thickness shear mode resonator device is disposed on a surface of a hydrocarbon processing apparatus.

12. The process of claim 8 wherein the hydrocarbon processing equipment is selected from the group consisting of hydrocarbon processing units for the production of styrene, acrylonitrile, acrylic acid, alkyl acrylates, vinyl chloride, butadiene and isoprene.

13. The method of claim 12, wherein the thickness shear mode resonator device is positioned flush with a surface of the hydrocarbon processing apparatus, and a quartz surface of the thickness shear mode resonator device is in contact with a hydrocarbon fluid positioned in the hydrocarbon processing apparatus.

14. The method of claim 8, wherein the hydrocarbon processing facility processes crude oil and the chemical feed pump provides one or more chemicals for hydrocarbon fluid correction selected from the group consisting of fouling inhibitors, corrosion inhibitors, fouling inhibitors, and defoamers.

15. The method of claim 8, wherein the quartz surface of the thickness shear mode resonator device is positioned flush with the surface of the hydrocarbon processing apparatus, and the quartz surface of the thickness shear mode resonator device is in contact with a hydrocarbon fluid disposed in the hydrocarbon processing apparatus.

16. The method of claim 8, wherein the quartz surface of the thickness shear mode resonator device is temporarily contacted with a fluid placed in the hydrocarbon processing apparatus.

17. A method for rapidly determining viscosity-density or viscosity/temperature conditions of a hydrocarbon fluid and taking various steps to correct or correct such conditions, characterized by:

(A) inserting a thickness shear mode resonator device into the hydrocarbon fluid, thereby contacting the quartz surface of the thickness shear mode resonator device with the hydrocarbon fluid;

(B) continuously exciting the thickness-shear mode resonator device and measuring the output of the thickness-shear mode resonator device, i.e. the mass and viscosity-density components of the hydrocarbon fluid;

(C) continuously determining the condition of the hydrocarbon fluid in contact with the quartz surface of the thickness shear mode resonator device based on the mass and viscosity-density components;

(D) the condition of the hydrocarbon fluid is continuously corrected by starting or stopping a chemical feed pump that feeds a chemical for condition correction into the hydrocarbon fluid.

18. The process of claim 17, wherein the hydrocarbon fluid is contained in a vessel selected from the group consisting of a hydrocarbon processing plant, a hydrocarbon storage tank, a pipeline, and a transport vessel.

19. The method of claim 18, wherein the thickness shear mode resonator device is temporarily placed in a vessel containing such hydrocarbon fluid.

20. The method of claim 18, wherein the thickness shear mode resonator device is placed flush with the surface of a vessel containing such hydrocarbon fluid, and the quartz surface of the thickness shear mode resonator device is in contact with such hydrocarbon fluid.

21. A method for rapidly determining the condition of a hydrocarbon/aqueous fluid mixture contained in a vessel and taking various steps to correct or remedy such condition, characterized in that the method comprises the steps of:

(A) inserting at least one thickness shear mode resonator device into the hydrocarbon/aqueous fluid mixture such that the quartz surface of the thickness shear mode resonator device is in contact with the hydrocarbon/aqueous fluid mixture;

(B) continuously exciting the thickness-shear mode resonator device and measuring the output of the thickness-shear mode resonator device, i.e. the mass and viscosity-density components of the hydrocarbon/aqueous fluid mixture;

(C) continuously determining the condition of the hydrocarbon/aqueous fluid mixture based on the mass and viscosity-density components of the hydrocarbon/aqueous fluid mixture;

(D) the condition of the hydrocarbon/aqueous fluid mixture is continuously corrected by starting or stopping a chemical feed pump that feeds the condition correcting chemical into the hydrocarbon/aqueous fluid mixture.

22. The process of claim 21 wherein the hydrocarbon/aqueous fluid mixture is contained in a vessel selected from the group consisting of a crude oil demulsifier, a crude oil thermal processor, a crude oil desalter, an ethylene quench water tower, a dilution steam generation system, a hydrocarbon storage tank, a hydrocarbon transport vessel, a wastewater purifier, a wastewater treatment unit, a settling tank, a surge tank, and a metalworking fluid bath.

23. The method of claim 22, wherein the quartz surface of the thickness shear mode resonator device is inserted to a position flush with the surface of a vessel containing such hydrocarbon/aqueous fluid mixture, and the quartz surface of the thickness shear mode resonator device is in contact with such hydrocarbon/aqueous fluid mixture.

24. The method of claim 22, wherein the quartz surface of the thickness shear mode resonator device is temporarily inserted into the hydrocarbon/aqueous fluid mixture.

25. The method of claim 21, wherein two or more thickness shear mode resonator devices are used, at least one of such devices being mounted at a location for detecting the presence of the aqueous phase and at least one of such devices being mounted at a location for detecting the presence of the hydrocarbon phase.