WO2022010992A1 - Electrostatic sprayer in-line flow measurement arrangement - Google Patents

Abstract

An in-line instantaneous direct flow rate measurement arrangement for an electrostatic spraying system is described. The arrangement includes a liquid feed stock line (125) supplying a liquid feed stock (115). The arrangement further includes an electrostatic spray nozzle assembly including: a spray nozzle (130) and an electrode (140) configured to provide an electrical charge potential to the liquid feed stock (115) emitted by the spray nozzle (130). The arrangement also includes an in-line instantaneous flow rate measurement arrangement comprising: an electrically isolating pipe segment (155); and an in-line instantaneous flowmeter (150) configured to sense a flow rate of the liquid feed stock (115) passing through the electrically isolating pipe segment (155).

Description

ELECTROSTATIC SPRAYER IN-LINE FLOW MEASUREMENT ARRANGEMENT

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This patent application claims the benefit of U.S. Provisional Patent Application No. 63/049,450 filed July 8, 2020, which is incorporated by reference.

AREA OF THE INVENTION

[0002] The present disclosure generally relates to electrostatic sprayer systems. More particularly, the present disclosure relates to an arrangement for performing in-line measurement instantaneous flow rate of liquid feed stock within a feed line for an electrostatic spraying system.

BACKGROUND OF THE INVENTION

[0003] In electrostatic spraying systems, liquid feed stock is charged to an electrical potential of tens of thousands of volts (e.g., 30 kilovolts) prior to discharge at a spray outlet. The high voltage potential causes the resulting spray droplets, upon discharge, to repel one another and thereby ensure a wide and uniform dispersal of the spray droplets and thereby facilitate efficient and complete drying of solids, which are suspended in the liquid feed stock, during a spray drying operation.

[0004] In many electrostatic spray drying operations, it is important to monitor a flow rate of material discharged from a spray nozzle. One way to gauge such flow rate is to monitor a change in weight of a vat containing feed stock. However, such measurement is typically too imprecise to provide an instantaneous rate of flow. Such precise information is important, for example, to monitor uniformity of a spray process and/or to quickly respond to a malfunction of the spraying system to avoid the need to discard a current batch of a batch spray-drying process.

[0005] One manner of providing an instantaneous flow-monitoring is to pass a feed line containing a liquid feed stock through a mass flowmeter (e.g. a Coriolis flowmeter). However, attempts to provide such direct flow rate measurement apparatus in line with the electrically charged fluid have been thwarted by damaging effect of high voltages present in the feed pipe upon the sensitive electronic circuitry of in-line flow sensors. SUMMARY OF THE INVENTION

[0006] In view of the challenges summarized above, a direct flow rate measurement arrangement is provided herein for use in an electrostatic spraying system. The arrangement includes a liquid feed stock line supplying a liquid feed stock. The arrangement further includes an electrostatic spray nozzle assembly including: a spray nozzle and an electrode configured to provide an electrical charge potential to the liquid feed stock emitted by the spray nozzle. The arrangement also includes an in-line instantaneous flow rate measurement arrangement comprising: an electrically isolating pipe segment; and an in-line instantaneous flowmeter configured to sense a flow rate of the liquid feed stock passing through the electrically isolating pipe segment.

BRIEF DESCRIPTION OF THE DRAWINGS [0007] While the appended claims set forth the features of the present invention with particularity, the invention and its advantages are best understood from the following detailed description taken in conjunction with the accompanying drawings, of which:

[0008] Figure 1 is a schematic diagram of an exemplary electrostatic spray drying system in in accordance will an illustrative example; and

[0009] FIG. 2 is a perspective view of an exemplary mounting arrangement of an in-line flowmeter on a feed stock pipe segment in accordance will an illustrative example.

DETAILED DESCRIPTION OF THE INVENTION [0010] In the present disclosure, an arrangement is provided for providing a direct, instantaneous, in-line flow-rate of a liquid feed stock for an electrostatic sprayer. Turning to FIG. 1, an exemplary electrostatic spray drier system 100 is illustratively depicted. In the illustrative example, a tank 110 holds a liquid feed stock 115. The liquid feed stock 115 is drawn by a motor-driven pump 120 from the tank 110 into and through a feed line 125 for discharge at a spray nozzle 130 inside a spray drying chamber 135. Importantly, an electrode 140 charges the liquid feed stock 115 to a desired electrical potential (e.g., 30 kVolts) while being discharged at the spray nozzle 130.

[0011] A controlled liquid feed stock delivery system, including the pump 120, delivers the liquid feed stock 115 at a specified flow rate to the spray nozzle 130. The motor-driven pump 120 is controlled by a controller 145 (e.g. a programmable logic controller) in accordance with a specified set point and a currently sensed flow rate. An operator specifies, for example, a flow rate set point via a human-machine interface (HMI) and then activates the motor-driven pump 120. Thereafter, the controller 145 monitors (via sensor input signals) a flow rate of the liquid feed stock and adjusts (via motor control signals) motor speed of the motor-driven pump 120 to maintain a set/specified flow rate of the liquid feed stock 115 to the spray nozzle 130. In order to maintain a desired flow, the controller 145 continuously receives a measurement signal indicative of an instantaneous flow rate of the liquid feed stock passing through a feed line to the spray nozzle.

[0012] In accordance with the present disclosure, an in-line flowmeter 150 measures instantaneous flow rate of the liquid feed stock 115 through an electrically insulated and ground protected pipe section 155 to which the in-line flowmeter 150 is operationally mounted. In accordance with illustrative examples, the pipe section comprises a pipe having a diameter of about four inches or less and a pipe thickness of 0.4 inches or less. The dimensions of a pipe of the pipe section 155 are selected to achieve a combination of desired properties including: electrical isolation from the feed stock 115 raised to an electrical potential tens of thousands higher than the potential of the in-line flowmeter 150, structurally strong to withstand a pressure at which the pump 130 provides the feed stock 115 flowing through the pipe section 155, sufficiently “transparent” to ultrasound that must pass into and from the pipe section 155 to be sensed by the in-line flowmeter 150, and is sufficiently non-interactive with the material of the feed stock 115 (especially for food and pharmaceutical electrostatic spray drying applications). By way of example, the following pipe materials are considered suitable for use at least in the pipe section 155 and exhibit properties favorably meeting the above-identified needs for the pipe section 155. Such pipe materials include: TEFLON, PEEK, and Kynar pipe materials. Additional potentially suitable materials include: polyvinylchloride (PVC), CPVC, Poly HD, Poly LD, Acrylic. In other instances, a metal pipe section may be used in combination with appropriate electrically insulating layer interposed between the flowmeter 150 and the metal pipe material. [0013] A variety of flowmeters (discussed further herein below) are capable of being used that maintain an electrical isolation of the flowing liquid feed stock 115 through the pipe section 155 and the in-line flowmeter 150. [0014] The in-line flowmeter 150, in turn, provides a signal to the controller 145 that maintains a historical record of sensed flow and provides control over the overall operation of the electrostatic spray drier system 100 (including a speed of the motor-driven pump 130).

[0015] Details of the general structure of the electrostatic spray drying system 100, including the controller 145, are well known to those in the industry and thus are not discussed in detail herein. Rather, attention is directed to an exemplary electrical/structural arrangement facilitating an electrically isolated functional/operational mounting of the in-line flowmeter 150 onto the electrostatic spraying system feed stock supply line in accordance with an example of the present disclosure.

[0016] By way of a first specific example, the in-line flowmeter 150 is any of many well- known Doppler flowmeters. The Doppler flowmeter uses a sensed frequency shift in a received (reflected) ultrasonic sound waves (transmitted into the feed stock flow at a known frequency and angle) to measure the fluid velocity in the pipe section 155. By measuring the frequency shift between the ultrasonic frequency source, the receiver, and the fluid carrier, the relative motion particles within the fluid flow (and thus the speed of the fluid flowing in the pipe) are measured. The sensor transmits continuous high-frequency sound through the pipe wall into the flowing liquid. Sound is reflected back to the sensor from particles or gas bubbles in the liquid. If the liquid is flowing, the reflected sound returns at an altered frequency (the Doppler Effect).

The flowmeter continuously measures the frequency shift to accurately measure an instantaneous velocity of fluid passing through the pipe section 155.

[0017] By way of a second specific example, the in-line flowmeter 150 is a well-known transit time ultrasonic flowmeter. E.g. GREYLINE DFM 6.1 FLOWMETER. Transit time ultrasonic flowmeters send and receive ultrasonic waves between transducers in both the upstream and downstream liquid feedstock flow directions in a pipe segment. At no flow conditions, it takes the same time to travel upstream and downstream between the transducers. Under flowing conditions, the upstream wave will travel slower and take more time than the (faster) downstream wave. When the fluid moves faster, the difference between the upstream and downstream times increases. The transmitter processes upstream and downstream times to determine the effectively instantaneous flow rate of the fluid within the pipe section 155. [0018] Both examples of the flowmeter 150 are suitable for carrying out substantially/effectively instantaneous measurements of flow rate of a liquid feed stock 115 passing through the pipe section 155 (i.e., determining a volume flow rate based upon the instantaneous flow speed and a known cross-section area of the pipe section 155). However, both flowmeter types contain electronic components that cannot operate in (or even survive) a high voltage of the magnitude to which the liquid feedstock is raised when passing from the tank 110 to the spray nozzle 130.

[0019] Turning to FIG. 2, an exemplary electrical/structural arrangement is illustratively depicted for the flowmeter 150 and the pipe section 155 containing a liquid feedstock 115 flow of interest. A first aspect of providing electrical isolation of the flowmeter 150 from disruptive high voltages arising from the electrode 140 (conducted upstream via the liquid feed stock and/or piping), involves providing an electrically non-conductive material for the pipe section 155 (e.g. a TEFLON pipe) that provides a high-voltage electrical break between the liquid feed stock 115 passing through the pipe section 155 and the flowmeter 150 mounted to the outside surface of the pipe section 155 to sense the fluid flow therein. The material must provide a high voltage electrical break without being so thick as to excessively attenuate the sensed ultrasound signals by the flowmeter 150.

[0020] A second aspect of providing electrical isolation of the flowmeter 150 from disruptive high voltages arising from the electrode 140 is to provide a first ground line 210 clamped to the pipe section 155 upstream of the flowmeter 150 and a second ground line 220 clamped to the pipe section 155 downstream of the flowmeter 150. In the illustrative example, the first ground line 210 and the second ground line 220 are secured by a first clamp 230 and a second clamp 240, respectively, to the pipe section 155. The flowmeter 150 is thus mounted to a part of the pipe section 155 between the first clamp 230 and the second clamp 240. The clamps 230 and 240 are connected to earth ground, thus shielding electronic circuitry of the flowmeter 150 from any stray electrical charge or electrostatic fields that may otherwise disrupt operation of the flowmeter 150.

[0021] Furthermore, while the illustrative examples have been depicted and described with reference to an exemplary electrostatic spray (drying) system, the disclosure is not limited to such systems. It will be readily appreciated that, in view of the current disclosure, the advantages of the current disclosure are also applicable to a variety of electrostatic spraying systems. As such, the current disclosure is intended to apply to a wide variety of direct in-line instantaneous flow rate sensing and monitoring arrangements - with appropriate adjustments to the above- described structures to accommodate variations in particular electrostatic spraying applications. [0022] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. [0023] The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0024] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

What is claimed is:

1. An electrostatic spraying system comprising: a liquid feed stock line supplying a liquid feed stock; an electrostatic spray nozzle assembly including: a spray nozzle; and an electrode configured to provide an electrical charge potential to the liquid feed stock emitted by the spray nozzle; and an in-line instantaneous flow rate measurement arrangement comprising: an electrically isolating pipe segment; and an in-line instantaneous flowmeter configured to sense a flow rate of the liquid feed stock passing through the electrically isolating pipe segment.

2. The electrostatic spraying system of claim 1 wherein the in-line instantaneous flow rate measurement arrangement further comprises: a first ground line coupled to the electrically isolating pipe segment upstream of the in-line instantaneous flowmeter; and a second ground line coupled to the electrically isolating pipe segment downstream of the in-line instantaneous flowmeter.

3. The electrostatic spraying system of claim 1 wherein the electrically isolating pipe segment comprises an electrically insulating material.

4. The electrostatic spraying system of claim 1 wherein the electrically isolating pipe segment has an inner surface diameter in a range of four inches or less.

5. The electrostatic spraying system of claim 1 wherein the electrically isolating pipe segment has a thickness in a range of 0.4 inches or less.

6. The electrostatic spraying system of claim 1 wherein the flowmeter is an ultrasound flowmeter.

7. The electrostatic spraying system of claim 6 wherein the flowmeter is a Doppler flowmeter.

8. The electrostatic spraying system of claim 6 wherein the flowmeter is a transit time flowmeter.