Systems and methods for controlling the particle size of metal oxide gel particles

Abstract

Metal oxide gel particles having a desired particle size are produced by preparing a low temperature aqueous metal nitrate solution containing hexamethylenetetramine as a feed solution; flowing the feed solution through a first conduit and exiting the first conduit as a first stream at a first flow rate to contact a high temperature non-aqueous drive fluid. The drive fluid flows through a second conduit at a second flow rate. Shear between the first stream and the drive fluid breaks the first stream into metal nitrate solution particles and decomposition of the hexamethylenetetramine converts the metal nitrate solution particles into metal oxide gel particles. A sensor device directed at the flow of the metal oxide gel particles within the stream of the drive fluid is used to optically measure the size of the metal oxide gel particles. The sensor measures the transmission of light absorbed by the metal oxide gel particles or the drive fluid so that as the metal oxide gel particles pass through the optical sensor, the transmission of light by the drive fluid changes over time. If the measured particle size is not approximately equal to the desired particle size, the particle size is corrected by adjusting the ratio of the first flow rate to the total flow rate, where the total flow rate is the sum of the first flow rate and the second flow rate.

Description

Technical Field

[0001] This invention generally relates to the preparation of metal oxide gel particles with controlled particle size. Background Technology

[0002] Metal oxide gel particles can be prepared by dispersing droplets of a metal salt solution in a non-aqueous fluid and causing the metal salt in the droplets to undergo internal gelation to form a gel phase in the form of metal oxide gel particles.

[0003] Metal oxide gel particles can be prepared using a two-fluid nozzle from solutions of various metal salts or metal oxide salts, including nitrates of uranium, thorium, plutonium, and lanthanides (such as cerium). The salt solution contains hexamethylenetetramine (HMTA) and urea, and flows from a first nozzle into a non-aqueous driven fluid in a second nozzle at a first flow rate. The non-aqueous driven fluid is heated to a temperature sufficient to cause the decomposition of HMTA.

[0004] In the case of uranyl nitrate solution, before the salt solution comes into contact with the driving fluid, it forms the formula UO2((NH2)2CO)2. +2 Metal ion-urea complexes, in which urea helps mitigate premature gelation. When these metal ion-urea complexes are heated by the driving fluid, they may dissociate to form UO2. +2 Or similar uranium oxide. Simultaneously, HMTA decomposes to form ammonium hydroxide. The decomposition of HMTA occurs in two steps, as shown in reactions (1) and (2):

[0005]

[0006]

[0007] The metal ions undergo further hydrolysis and condensation, as shown in reactions (3) and (4):

[0008]

[0009]

[0010] The ammonium hydroxide produced during reaction (2) increases the pH of the solution, promotes hydrolysis and condensation (3), and leads to the formation of spherical gel particles 2UO3. 2H2O. Uranium oxide gel spheres are collected and sintered to form ceramic particles that can be used as nuclear fuel cores.

[0011] During gel particle formation, metal oxide solution droplets are dispersed at high speed in the driving fluid and rapidly gel due to HMTA decomposition. The particle size of these gel particles is crucial from a nuclear fuel specification perspective. Specifically, the particle size of the sintered ceramic particles used in nuclear fuel pellets is controlled by the particle size of the gel particles. After sintering, the mass loss of the gel particles is approximately 35%, while the particle radius shrinks by approximately 65%. During the formation of gel particles through internal gelation, the particle size of the formed gel particles is unknown until gelation is complete and the particles are recycled. Characterization of the gel particles may reveal that they are too large to produce the desired product, such as nuclear fuel. Alternatively, the particles may be too small or have a wide particle size distribution, failing to meet the requirements for the desired application.

[0012] The present invention relates to a method for preparing metal oxide gel particles with controlled particle size, the method allowing the particle size to be adjusted during particle formation.

[0013] The purpose of this description is to illustrate the advantages that can be achieved through the various embodiments disclosed herein, and it is not an exhaustive list or limitation of the possible advantages that can be achieved. Other advantages of the various embodiments disclosed herein will be apparent from the description, or may be learned from practicing the various embodiments disclosed herein, or may be modified according to any variations that may be apparent to those skilled in the art. Therefore, the present invention relates to novel methods, arrangements, combinations, and improvements shown and described in various embodiments. Summary of the Invention

[0014] The various embodiments disclosed herein relate to optical sensors that allow for real-time analysis of the particle size of gel particles formed in a dual-fluid nozzle, as well as the flow rate of the gel particles within the nozzle.

[0015] The various embodiments disclosed herein relate to methods for optimizing the particle size of metal oxide gels, including preparing a low-temperature aqueous solution of a metal nitrate containing hexamethylenetetramine as a feed solution; flowing the feed solution through a first nozzle and exiting the first nozzle as a first stream at a first flow rate; and flowing a high-temperature non-aqueous driving fluid through a second nozzle as a second stream at a second flow rate, wherein the second stream contacts the first stream. In various embodiments, shearing between the first and second streams breaks the first stream into droplets of the metal nitrate solution, and thermal decomposition of the hexamethylenetetramine by the high-temperature driving fluid converts the droplets of the metal nitrate solution into metal oxide gel particles. The gel particles are carried in the second stream of the driving fluid. In various embodiments, a sensor device guiding the flow of metal oxide gel particles in the driving fluid is used to optically measure the average particle size or the average flow rate of the metal oxide gel particles in the driving fluid.

[0016] In various embodiments, the sensor device measures the transmission of light absorbed by the metal oxide gel particles or the driving fluid, such that the transmission of light through the driving fluid changes over time as the metal oxide gel particles pass through the sensor device. This change in light transmission over time can be used to measure the average particle size or volumetric flow rate. In various embodiments, if the measured particle size or volumetric flow rate is not approximately equal to the desired droplet size or flow rate, the droplet size or flow rate is adjusted by regulating the ratio of a first flow rate to a total flow rate, where the total flow rate is the sum of the first and second flow rates.

[0017] In various embodiments, if the measured particle size is larger than the desired particle size, the measured particle size can be reduced by increasing the flow rate of the driving fluid, reducing the flow rate of the feed solution, or both. In various embodiments, if the measured particle size is smaller than the desired particle size, the measured particle size can be increased by reducing the flow rate of the driving fluid, increasing the initial flow rate of the feed solution, or both.

[0018] In various embodiments, the sensor device includes a first optical sensor and a second optical sensor spaced apart from each other by a first distance along a driving fluid; the first and second sensors each include a first optical fiber and a second optical fiber located on opposite sides of the driving fluid. The first optical fiber in each sensor transmits a signal through the driving fluid, and the second optical fiber receives the signal. In various embodiments, the signal transmitted by the first optical fiber in each sensor is an optical signal whose wavelength is not absorbed by the driving fluid but is absorbed by the metal oxide gel particles. Within each sensor, the distance between the first and second optical fibers is at least equal to the diameter of the conduit delivering the driving fluid, and this distance is small enough to prevent signal attenuation propagating through the driving fluid.

[0019] In various embodiments, the first sensor and the second sensor are spaced apart from each other by a first distance along a second flow path of the driving fluid. The first distance between the two sensors is less than the average diameter of the gel particles, wherein the average diameter of the gel particles can be 0.8 mm to 3.2 mm, 1 mm to 2.5 mm, 1 mm to 2 mm, 1 mm to 1.5 mm, or 1.5 mm to 2 mm. In various embodiments, the distance between the sensors is smaller than the required target diameter of the gel particles by 0.1 mm to 1 mm, 0.2 mm to 0.9 mm, 0.3 mm to 0.8 mm, or 0.5 mm to 0.7 mm.

[0020] In various embodiments, the average particle size can be estimated by first calculating the velocity of the metal oxide gel particles passing through a first optical sensor and / or a second optical sensor. In various embodiments, the two sensors are spaced a known distance apart along the flow path, and the gel particle velocity is calculated based on the time it takes for the front or rear end of the gel particle to travel that known distance. Once the gel particle velocity is determined, the flow rate of the driving fluid carrying the gel particles through the sensors can be calculated. Once the flow rate is calculated, the flow fraction (gel particle volume) filling the gel particles is then calculated by dividing a first time length for a single gel particle to pass through a single optical sensor by a second time length for two consecutive gel droplets to reach the single optical sensor.

[0021] In various embodiments, the apparatus for producing metal oxide gel particles with controlled particle size includes a system for forming metal oxide gel particles, characterized in that:

[0022] A drive fluid nozzle that defines a flow path, the drive fluid nozzle being configured to deliver a drive fluid stream along the flow path at a first flow rate;

[0023] A metal salt solution nozzle having an outlet, the metal salt nozzle being configured to deliver a first stream of a cryogenic metal salt aqueous solution containing hexamethylenetetramine into the flow path at a second flow rate; and optionally...

[0024] The heater is configured to maintain the temperature of the driving fluid at a level where hexamethylenetetramine is sufficient to cause the metal salt in the metal salt solution to gel.

[0025] In various embodiments, the apparatus further includes a system for controlling the average particle size of the metal oxide gel particles, the system being located downstream of the metal oxide gel particle formation system. The system for controlling the gel particle size includes a sensor device comprising:

[0026] A first sensor and a second sensor, spaced apart from each other by a first distance along the flow path, are configured to measure the average particle size and particle flow rate of the gel particles; and

[0027] A control system for adjusting the average particle size of metal oxide gel particles based on input from a sensor device.

[0028] In various embodiments, the system for controlling the average gel particle size is configured to calculate the volumetric flow rate based on a first passage time taken for the metal oxide gel particles to pass through the distance between the first and second sensors.

[0029] In various embodiments, if the calculated gel particle size differs from the desired gel particle size, the system for controlling the average particle size is configured to adjust the average particle size of the gel particles by adjusting the ratio of a first flow rate to a total flow rate of the driving fluid, wherein the total flow rate is the sum of the first and second flow rates of the metal salt solution.

[0030] In view of the current need for improved methods for preparing metal oxide gel particles with predictable particle sizes, a brief description of various exemplary embodiments is given. Some simplifications and omissions may occur in the following description, which are intended to highlight and introduce some aspects of various exemplary embodiments, and not to limit the scope of the invention. A detailed description of preferred exemplary embodiments sufficient to allow those skilled in the art to make and use the concepts of the invention will be provided in later sections. Attached Figure Description

[0031] To better understand the various exemplary embodiments, reference is made to the accompanying drawings, in which:

[0032] Figure 1 An apparatus for monitoring the particle size of metal oxide gel particles formed in a dual-fluid nozzle is shown.

[0033] Figure 2 and Figure 3 This illustrates when the sensor detects metal oxide gel particles, Figure 1 The output data generated by the sensors in the device; and

[0034] Figure 4 A process flow diagram is shown for controlling the particle size of metal oxide gel particles formed in a dual-fluid nozzle.

[0035] Figure 5 It shows Figure 1 The device, as well as the CPU and the CPU-controlled pump;

[0036] Figure 6 It is shown that:

[0037] The change in core diameter of sintered metal oxide particles prepared from gel particles over time;

[0038] The change in flow rate of metal oxide adhesive over time; and

[0039] Changes in total flow over time; and

[0040] Figure 7 The diagram shows the change in core diameter as a function of the ratio of metal oxide liquid flow rate to total flow rate.

[0041] Due to generation Figure 6 and Figure 7The data used in the middle section employs a large number of data points, and the data is shown as a data cloud representing overlapping data points, rather than plotting individual data points. Detailed Implementation

[0042] The term “about” as used herein can be interpreted as “within 10% of the specified value,” “within 5% of the specified value,” or “within 3% of the specified value.” All numbers without qualifiers can be interpreted using significant figures.

[0043] Just as the language applied to a device or its components is “configured as,” it means that the listed device or component is designed or constructed to perform the listed functions.

[0044] The term "diameter," referred to herein as m1, means the length of the particle as it passes through the tube and passes the optical sensor. In some cases, the tube diameter may be smaller than the particle length, causing the particle to elongate along the tube length. In other cases, the tube diameter may be greater than or approximately equal to the particle length, thus making the particle essentially spherical. In either case, the distance along the particle's length should be referred to as its diameter m1.

[0045] Referring now to the accompanying drawings, in which similar figures indicate similar components or steps, a wide range of exemplary embodiments are disclosed.

[0046] Figure 1 This is a system for measuring the particle size of metal oxide gels. The system includes a nozzle 1 (“driving fluid nozzle”) configured to deliver a non-aqueous driven fluid, wherein the driving fluid is delivered within the nozzle 1 at a first flow rate in a flow path marked by arrow A. Gel particles 3 with a diameter m1 (in…) Figure 1 The particle size (displayed as the length equal to the elongated particle) travels along pipe 1 in the direction of arrow A, passing through first sensor 4 and second sensor 5, each sensor being connected to CPU 10. Sensor 4 has two optical fibers, 6 and 7, separated by pipe 1. A light signal of a selected wavelength is transmitted from fiber 6 to fiber 7 in the direction of arrow B. The driving fluid is transparent to the selected wavelength, while the gel particles 3 are translucent or opaque to the selected wavelength. The signal showing the change in light intensity over time between the light transmitted from fiber 6 and the light received by fiber 7 is transmitted to CPU 10. The outputs of sensors 4 and 5 are transmitted to CPU 10 via cables 13 and 14, where the particle size is calculated.

[0047] Figure 2The diagram illustrates the change in light intensity over time as a series of gel particles pass through sensor 4. If the change in light intensity between the light transmitted from fiber 6 and the light received by fiber 7 is less than a predetermined background value, the CPU outputs a zero value. If the change in light intensity exceeds the predetermined background value due to the presence of gel particles 3 between fibers 6 and 7, the CPU outputs a value of 1, thus generating a series of time-dependent signals in the form of square waves 11. Each square wave 11 has a leading edge 11a and a trailing edge 11b. The length of each square wave corresponds to the time period (period P) during which a single gel particle passes through sensor 4. The time between the leading edges 11a (or trailing edges 11b) of adjacent square waves provides the frequency F of the gel particle passing through sensor 6. If all particles 3 have similar particle sizes, the period and frequency can be determined from two adjacent square waves. If particles 3 have different particle sizes, the average or median of the period and frequency can be determined from the series of square waves 11.

[0048] like Figure 1 As shown, sensor 5 has two optical fibers 8 and 9 separated by conduit 1. A light signal of a selected wavelength is transmitted from fiber 8 to fiber 9. A signal showing the time-varying light intensity between the light transmitted from fiber 6 and the light received by fiber 7 is transmitted to CPU 10. Figure 3 The diagram illustrates the change in light intensity over time as a series of gel particles pass through sensor 4 and sensor 5. Sensors 4 and 5 are arranged such that the distance x1 between optical fibers 6 and 7 is less than the required gel particle size m1.

[0049] like Figure 3 As shown, sensors 4 and 5 each provide a series of square waves 11 representing the change in light intensity over time, offset by a time interval ΔT. The period P and frequency F can be calculated from the output of sensor 4 or sensor 5, or as an average value obtained from sensors 4 and 5.

[0050] Once the period P, frequency F, and offset ΔT are determined, the particle velocity, flow rate, and particle volume can be determined. First, the particle velocity can be determined based on the offset time ΔT, which corresponds to the time required for the front or rear end of a single particle to travel the distance x1 between sensors 4 and 5. The velocity V can be calculated as follows:

[0051]

[0052] The total volumetric flow rate Flow of the metal ion solution and the driving fluid through pipe 1 can be calculated from the velocity v and the inner diameter d1 of pipe 1 as follows:

[0053]

[0054] Flow rate of metal ion solution M The following can be calculated:

[0055]

[0056] The above formula can be rewritten as follows:

[0057]

[0058] When will Flow M When plotting the particle size of the core obtained from sintered gel particles against the flow control, at least 0.4... <Flow M When / Flow < 0.8, the particle size and Flow M The flow rate is linearly correlated with the particle size. Therefore, by controlling this flow rate ratio, the particle size can be controlled.

[0059] The volume of gel particles can be estimated by multiplying the period P by the flow rate:

[0060]

[0061] Back Figure 1 A solution carrying a metal oxide salt solution is passed through pipe 12, intersecting with pipe 1, which delivers a driving fluid at a first flow rate in the flow path marked by arrow A. Pipe 12 delivers a cryogenic aqueous solution of the metal salt (“salt solution”) at a second flow rate in the flow path marked by arrow C. The outlet of pipe 12 is located within the flow path of the driving fluid in pipe 1. The metal oxide salt can be a salt of lanthanides, plutonium, uranium, or thorium. The metal oxide salt can also be any salt that gels upon reaction with ammonia or ammonium hydroxide.

[0062] As the salt solution exits pipe 12, the shear between the salt solution stream and the drive fluid stream breaks the salt solution stream into salt solution particles dispersed in the drive fluid. In various embodiments, the salt solution contains hexamethylenetetramine (HMTA), and the drive fluid is heated to a temperature sufficient to decompose the HMTA into ammonia and formaldehyde. The ammonia then gels the salt solution particles into spherical metal oxide gel particles 3. Particles 3 are conveyed along nozzle 1 by the drive fluid stream in the direction of arrow A.

[0063] Although Figure 1 The metal oxide solution transport pipe 12 shown intersects pipe 1 at a right angle, but this is not... Figure 1 Essential features of the device. In some embodiments, pipe 1 and pipe 12 may be coaxial, with pipe 12 inside pipe 1. Alternatively, pipe 1 and pipe 12 may intersect to form a single common pipe. The only requirement is that the salt solution in pipe 12 flows into the flow-driven fluid transported by pipe 1.

[0064] In various embodiments, metal oxide compounds, such as UO3, U3O8, UO2(NO3)2, thorium or plutonium nitrates, or lanthanide metal nitrates, are used to form metal oxide salt solutions. The metal oxide compound is dissolved in an aqueous solution to form a metal-containing salt solution. In various embodiments, the metal oxide compound is a uranium compound, such as UO3, U3O8, or UO2(NO3)2. The salt solution may also contain urea and HMTA. In various embodiments, the salt solution may be a uranyl nitrate solution containing water, UO3, and HNO3 or UO2(NO3)2. Urea reacts with metal ions at low temperatures to form a complex that prevents premature gelation, such as UO2(NH2CO)2. +2 .

[0065] The non-aqueous driving fluid can be heated to temperatures of 50°C to 90°C, 50°C to 80°C, 55°C to 75°C, 55°C to 70°C, or approximately 60±5°C. In the case of uranyl nitrate solution, when the salt solution leaves pipe 12 and comes into contact with the driving fluid, the metal ion-urea complex may dissociate to form UO2. +2 Simultaneously, HMTA decomposes to form ammonium hydroxide and formaldehyde. The ammonium hydroxide produced by HMTA decomposition neutralizes uranium oxide and promotes the formation of metal ion polymers (UO2(OH)) in spherical gel particles 3 within nozzle 1. n +n .

[0066] Based on the inputs from sensors 4 and 5 via cables 13 and 14, CPU 10 controls the control system to adjust the average particle size of the metal oxide gel particles, such as... Figure 4 As shown. The CPU receives data from sensors 4 and 5, which defines the first travel time (ΔT) of the first distance x1 between the gel particle travel sensors 4 and 5. Figure 4 In step 15, the particle velocity is calculated by using the above equation (5) to calculate the time ΔT from the distance x1 traveled by the metal oxide gel particle, and the volumetric flow rate is determined by multiplying the particle velocity by the cross-sectional area of ​​the driving fluid flow according to the above equation (6), thereby converting the passage time ΔT into the volumetric flow rate.

[0067] exist Figure 4 In step 16, such as Figure 1 The particle size m1 of the metal oxide gel shown is calculated as follows: multiply the volumetric flow rate calculated in step 13 by... Figure 4 The period P shown is used to determine the particle volume.

[0068] exist Figure 4In step 17, the calculated particle size m1 is compared with the required particle size m2. If m1 = m2 (step 18), the particle gelling conditions in nozzle 1 are not changed and the analysis ends (step 19). If m1 > m2 (step 20), the gel particles are too large and the CPU adjusts Figure 1 the relative flow rates of the driving fluid in pipe 1 and the salt solution in pipe 12. By reducing the ratio of the salt solution flow rate A to the sum of the flow rate A and the driving fluid flow rate B, for example by reducing the flow rate of the salt solution relative to the driving fluid flow rate (step 20a), Figure 1 the shear between the two solutions in nozzle 1 increases, reducing the particle size of the salt solution particles dispersed in the driving fluid.

[0069] If m1 < m2 (step 21), the gel particles are too small and the CPU increases the ratio of the salt solution flow rate A to the sum of the flow rate A and the driving fluid flow rate B, for example by increasing the flow rate of the salt solution relative to the driving fluid flow rate (step 20a), to reduce the particle size of the salt solution particles dispersed in the driving fluid.

[0070] Figure 5 shows Figure 1 the device shown, and the CPU 10, as part of a system that allows the user to adjust the particle size of the gel particles 3. Figure 5 shows pipe 1, configured to convey a driving fluid at a first flow rate in the flow path marked by arrow A; and pipe 12, configured to convey a metal salt aqueous solution at a second flow rate in the flow path marked by arrow B. The outlet of pipe 12 is within the flow path of pipe 1 (note that pipes 1 and 12 are Figure 5 coaxial in the system, but Figure 1 perpendicular to each other in ). The driving fluid is driven from pipe 1a to pipe 1 by pump 22. The salt solution is driven from pipe 12a to pipe 12 by pump 23. Data from sensors 4 and 5 are transmitted to the CPU 10 via cables 13 and 14, where the volumetric flow rate, particle volume, and particle diameter of the material flow in nozzle 1 can be calculated, as Figure 4As shown, if the calculated gel particle size m1 is not approximately equal to the required particle size m2, the CPU sends signals to pumps 22 and 23 via cables 24 and 25 to change the relative speeds of pumps 22 and 23. If d1 > x1, the gel particles are too large, and the CPU changes the relative flow rates of the driving fluid in nozzle 1 and the salt solution in nozzle 2 of FIG. 1 by increasing the speed of pump 22, decreasing the speed of pump 21, or by both means. If d1 < x1, the gel particles are too small, and the CPU decreases the relative flow rates of the driving fluid and the salt solution by decreasing the speed of pump 22, increasing the speed of pump 23, or by both means. The CPU thus manipulates the relative flow rates of the driving fluid and the salt solution to control the degree of shear between the driving fluid and the salt solution after the salt solution exits nozzle 2 and contacts the driving fluid. An increase in shear causes the salt solution to break into smaller droplets, and a decrease in shear causes the salt solution to break into larger droplets.

[0071] Example 1: Controlling Gel Particle Size by Controlling Flow Rate

[0072] An underacid uranyl nitrate solution with a concentration of 1.3 M was prepared based on UO2(NO3)2. The solution contained 1.7 M urea and 1.7 M HMTA and had a viscosity of approximately 1.2 cP. The salt solution was pumped into Figure 1 pipe 12 of the device at a temperature of 0°C to 5°C. As Figure 6 shown, the salt solution or gel solution exits pipe 12 at a flow rate generally ranging between 0.5 mL / min and 1.5 mL / min. Then, the salt solution enters the driving fluid pipe 1.

[0073] The driving fluid was pumped into Figure 1 pipe 1 of the device. The driving fluid was silicone oil with a viscosity of 100 cP and an initial temperature of 0°C to 5°C. The flow rate of the driving solution was controlled to maintain the total flow rate generally between 1.3 mL / min and 2.25 mL / min, as Figure 6 shown. Once the driving fluid and the salt solution enter pipe 1, the contents of pipe 1 are heated to approximately 56°C, and the uranyl nitrate is induced to gel by HMTA, thereby inducing the thermal gelation of the salt solution to form uranium oxide gel particles.

[0074] Using Figure 1 the device to record data. The diameter of nozzle 1 is 1 mm. Referring to Figure 1 , the distance x1 between sensors 4 and 5 is 6.35 mm. The distance between the optical fibers in each of sensors 4 and 5, for example, the distance between optical fibers 6 and 7 in sensor 4, is 3.2 mm. The diameter of each optical fiber sensor 6, 7, 8, and 9 is 1.6 mm. When the gel spheres pass through the optical fiber sensors, the gel spheres are detected using red light with a wavelength of 680 nm.

[0075] In the first experiment, the flow rates of the driving fluid and the salt solution were recorded by the processor as a function of time, such as... Figure 6 As shown. The processor also records the period P and frequency F of the gel particles in the flow-driven fluid. The heated drive fluid causes HMTA decomposition, resulting in thermal gelation and uranium oxide gel particles. According to equation (8), the gel particle volume is calculated as a function of period P and total flow rate. The processor is configured to calculate the volume and diameter of the sintered uranium oxide particles based on an expected 65% loss of gel particle volume during sintering. The calculated diameter of the sintered uranium oxide particles or core is plotted against time, as shown. Figure 6 As shown. Figure 6 As shown in Table 1, controlling the total flow rate and the salt solution flow rate will change the diameter of the core particles obtained by sintering the gel particles.

[0076] Table 1.

[0077]

[0078] Flow / Flow M Plotting the graph according to the core diameter, such as... Figure 7 As shown, when 0.3 <Flow / Flow M <0.8, or 0.4 <Flow / Flow M When <0.75, the core diameter and the flow ratio Flow / Flow M A linear dependence exists. This indicates that the core diameter can be controlled by manipulating the ratio of the metal ion solution flow rate to the total flow rate.

[0079] While various exemplary embodiments have been described in detail with specific reference to certain exemplary aspects, it should be understood that other embodiments of the invention are possible, and their details can be modified in various obvious ways. As will be apparent to those skilled in the art, these variations and modifications can be achieved while remaining within the spirit and scope of the invention. Therefore, the foregoing disclosure, description, and drawings are for illustrative purposes only and do not limit the invention in any way, which is defined only by the claims.

Claims

1. A method of measuring the size of metal oxide gel particles in a flowing stream within a constant pipe having an internal diameter dl, wherein the internal diameter dl of the constant pipe is less than the length of the metal oxide gel particles in the direction of flow, the size ml, the method comprising: a. flowing a driving fluid stream comprising metal oxide gel particles through at least two sensors, the at least two sensors being separated by a distance less than the desired size in the direction of flow of the driving fluid stream; b. optically measuring the size or flow of the metal oxide gel particles in the flowing stream within the internal diameter dl of the constant pipe using the at least two sensor devices; the sensors measuring the transmission of light absorbed by the metal oxide gel particles or the driving fluid, such that the transmission of light by the driving fluid changes over time as the metal oxide gel particles pass through the optical sensors; each of the sensors comprising an emitter and a corresponding receiver, the emitter and the receiver being located on opposite sides of the driving fluid; and the emitter of each of the sensors being configured to send light to the corresponding receiver.

2. The method of claim 1, wherein the measuring the flow of the metal oxide gel particles comprises: measuring the velocity of the metal oxide gel particles in the flowing stream by measuring the time AT for the leading or trailing edge of the metal oxide gel particles to travel from the first sensor to the second sensor and dividing AT by the distance between the first sensor and the second sensor; and multiplying the velocity of the metal oxide gel particles by the cross-sectional area of the flowing stream.

3. The method of claim 1, wherein the measuring the size of the metal oxide gel particles comprises: measuring the velocity of the metal oxide gel particles in the flowing stream by measuring the time AT for the leading or trailing edge of the metal oxide gel particles to travel from the first sensor to the second sensor and dividing AT by the distance between the first sensor and the second sensor; and multiplying the velocity of the metal oxide gel particles by the cross-sectional area of the flowing stream to determine the flow of the flowing stream; and multiplying the flow by the time for the metal oxide gel particles to pass the first sensor.

4. A method of optimizing the size of metal oxide gel particles in a flowing stream within a constant pipe having an internal diameter dl, wherein the internal diameter dl of the constant pipe is less than the length of the metal oxide gel particles in the direction of flow, the size ml, the method comprising: a. preparing a low temperature metal salt solution containing hexamethylenetetramine as a feed solution; b. flowing the feed solution through a first nozzle and exiting the first nozzle as a first stream at a first flow rate; c. flowing a non-aqueous driving fluid as a second stream through a second nozzle at a second flow rate, wherein the second stream contacts the first stream; wherein: the shear between the first stream and the second stream breaks the first stream into particles of the metal salt solution, and the decomposition of the hexamethylenetetramine converts the metal salt solution particles into metal oxide gel particles; d. using a sensor device that directs the flow of the metal oxide gel particles within the second stream to optically measure the size or flow rate of the metal oxide gel particles in the flowing stream within the inner diameter dl of the constant pipe; the sensor measures the transmission of light absorbed by the metal oxide gel particles or the driving fluid, such that the transmission of light by the driving fluid changes over time as the metal oxide gel particles pass through the optical sensor; e. if the measured size or flow rate is not approximately equal to the desired size or flow rate, adjusting the size or flow rate by adjusting the ratio of the first flow rate to the total flow rate, where the total flow rate is the sum of the first flow rate and the second flow rate; wherein the sensor device includes a first sensor and a second sensor, the first sensor and the second sensor are spaced apart from each other by a first distance along the second stream of the driving fluid, the first distance is less than the desired size; each of the first sensor and the second sensor includes a transmitter and a corresponding receiver, the transmitter and the receiver are located on opposite sides of the driving fluid; and the transmitter of each of the first sensor and the second sensor is configured to send light to the corresponding receiver.

5. The method of claim 4, wherein the measured size is greater than the desired size, the measured size is decreased by decreasing the first flow rate of the feed solution.

6. The method of claim 4, wherein the measured size is less than the desired size, the measured size is increased by increasing the first flow rate of the feed solution.

7. The method of claim 4, wherein the measured size is different than the desired size, the measured size is changed by changing the first flow rate of the feed solution.

8. The method of claim 4, wherein the measuring the flow rate of the metal oxide gel particles comprises: measuring the velocity of the metal oxide gel particles in the flowing stream by measuring the time AT that the leading edge or the trailing edge of the metal oxide gel particles travels from the first sensor to the second sensor and dividing AT by the distance between the first sensor and the second sensor; and multiplying the velocity of the metal oxide gel particles by the cross-sectional area of the flowing stream.

9. The method of claim 4, wherein the measuring the size of the metal oxide gel particles comprises: measuring the velocity of the metal oxide gel particles in the flowing stream by measuring the time AT that the leading edge or the trailing edge of the metal oxide gel particles travels from the first sensor to the second sensor and dividing AT by the distance between the first sensor and the second sensor; and multiplying the velocity of the metal oxide gel particles by the cross-sectional area of the flowing stream to determine the flow rate of the flowing stream; and multiplying the flow rate by the time that the metal oxide gel particles pass through the first sensor.

10. A system for producing metal oxide gel particles having a controlled size in a flowing stream within the inner diameter dl of a constant pipe, comprising: A subsystem for forming metal oxide gel particles in a flowing stream within an inner diameter d1 of a constant conduit, wherein the inner diameter d1 of the constant conduit is less than a length of the metal oxide gel particles in a flow direction is a particle size m1, the subsystem for forming metal oxide gel particles in a flowing stream within an inner diameter d1 of a constant conduit comprising: a drive fluid nozzle defining a flow path, the drive fluid nozzle configured to transport a second stream of drive fluid along the flow path at a second flow rate; a metal salt solution nozzle having an outlet, the metal salt nozzle configured to transport a first stream of a low temperature metal salt solution containing hexamethylenetetramine into the flow path at a first flow rate; and a heater configured to maintain a temperature of the drive fluid at a level sufficient for the hexamethylenetetramine to cause the metal salt in the metal salt solution to gel; a subsystem for controlling an average particle size of the metal oxide gel particles, the subsystem for controlling an average particle size of the metal oxide gel particles located downstream of the subsystem for forming metal oxide gel particles in a flowing stream within an inner diameter d1 of a constant conduit, comprising: a sensor arrangement, wherein the sensor arrangement comprises a first sensor and a second sensor, each of the first sensor and the second sensor comprising a transmitter and a corresponding receiver, the transmitter and the receiver located on opposite sides of the drive fluid; and the transmitter of each of the first sensor and the second sensor configured to send light to the corresponding receiver: wherein the first sensor and the second sensor are spaced apart from each other along the flow path by a first distance, the first sensor and the second sensor configured to measure a volume flow rate and an average particle size of the metal oxide gel particles; and a control module for adjusting the average particle size of the metal oxide gel particles based on input from the sensor arrangement.

11. The system of claim 10, wherein the first sensor and the second sensor are spaced apart from each other along the flow path by the first distance, the first distance being less than the desired particle size of the metal oxide gel particles.

12. The system of claim 10, wherein the subsystem for controlling an average particle size of the metal oxide gel particles is configured to calculate the volume flow rate based on a first transit time of the metal oxide gel particles to travel the first distance between the first sensor and the second sensor and a second transit time of the metal oxide gel particles to pass through a single sensor.

13. The system of claim 10, wherein the subsystem for controlling an average particle size of the metal oxide gel particles is configured to calculate the average particle size of the metal oxide gel particles based on a first transit time of the metal oxide gel particles to travel the first distance between the first sensor and the second sensor and a second transit time of the metal oxide gel particles to pass through a single sensor.

14. The system of claim 12, wherein the subsystem for controlling the average particle size of the metal oxide gel particles is configured to adjust the average particle size of the metal oxide gel particles by adjusting the ratio of the first flow rate to a total flow rate, wherein the total flow rate is the sum of the first flow rate and a second flow rate.

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