AU2008201000B2

AU2008201000B2 - Dosing

Info

Publication number: AU2008201000B2
Application number: AU2008201000A
Authority: AU
Inventors: Michael James Stanbrook
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-03-03
Filing date: 2008-03-03
Publication date: 2014-02-13
Anticipated expiration: 2028-03-03
Also published as: AU2008201000A1; NZ575203A

Abstract

Abstract A dosing mechanism for dosing a fluid flow in a conduit with an agent. The mechanism includes a bypass line for taking a selected portion of the fluid from the fluid flow conduit at a take off point and returning the selected portion to the fluid flow conduit at an injection point. The mechanism further includes an agent introducing means for introducing an agent to the fluid within the bypass line. An indicator means provides an indication of the quantity of agent in the introducing means. '/513 20Fk 1/ aL*e VJo+ 4 3o litII

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Dosing The following statement is a full description of this invention, including the best method of performing it known to me: 471 2 Dosing Field of the invention The invention relates to dosing a fluid flow with an agent, for example dosing a flow of agricultural water with iodine. 5 Background of the invention There are instances where a dosing agent is added to a water flow as a treatment agent for the water, such as when sterilising a water flow by the additional chlorine or iodine or to produce a dilute concentration of dosing agent in the water for spraying. 0 Various compounds but particularly iodine have been used for water disinfection on a large scale in the past and is often used as an antibiotic against pathogens when maintaining biologically safe water supplies and in treatment of food stuffs such as fruit. In order to effectively apply water borne dosing agents, it is desirable that the concentration of the dosing agent in the dosed fluid is maintained at a constant level 5 above an effective threshold or at a preset level. This can be made difficult by varying flow rates and varying input conditions such as varying pH and temperature of the fluid flow. Dosing stations have been proposed for forming an iodine concentrated aqueous solution in which water passes through a canister of iodine crystals dissolving the iodine 20 in solution at the solubility limit of the iodine in water. The concentration of iodine in the treated water varies significantly depending on the temperature and the pH of the water and the contact time of the water with the solid iodine. In such circumstances, it is sometimes difficult to control the concentration of iodine in the concentrated aqueous solution and in the resultant water flow where the flow can vary from the source. 25 Furthermore occasionally the supply of iodine particles within the canister is exhausted leading to untreated water passing through the system, and in some 471 3 instances canisters still having an operational amount of iodine particles are removed and discarded. It is an object of the invention to provide an improved dosing system and method or at least provide alternatives in the market place. 5 Summary of the invention In one aspect of the invention there is provided a dosing mechanism for dosing a fluid flow in a conduit with an agent, the mechanism including: a bypass line for taking a selected portion of the fluid from the fluid flow conduit at a take off point and returning the selected portion to the fluid flow conduit at an injection 1o point; agent introducing means for introducing an agent to the fluid within the bypass line; and an indicator means for providing an indication of the quantity of agent in the introducing means. 15 The agent introducing means could be a canister having apertures to permit fluid to flow therethrough and containing a quantity of solid agent. The indicator means preferably provides an indication of the weight of the agent introducing means, for example it could be a load cell. Preferably the injection point is downstream of the take off point. 20 A secondary bypass line can be arranged in parallel to the agent introducing means. Preferably the mechanism includes selection means for controlling the relative amount of fluid in the selected portion in response to a concentration of the agent in the fluid downstream of the injection point. Preferably an agent specific electrode is 25 positioned downstream of the injection point for providing an indication of the 471 4 concentration of agent. Preferably the selection means includes a pump positioned along the bypass line. The pump may be controlled by a variable speed drive. An ORP controller can be used in conjunction with the agent specific electrode to provide a millivolt signal indicative of the concentration of agent. 5 In another aspect of the invention there is provided a dosing mechanism for dosing a fluid flow in a fluid flow conduit with an agent, the mechanism including: a bypass line for taking a selected portion of the fluid from the fluid flow conduit at a take off point and returning the selected portion to the fluid flow conduit at an injection point; 10 agent introducing means for introducing an agent to fluid within the bypass line; and a selection means including a pump positioned along the bypass line for controlling the relative amount of fluid in the selected portion in response to a concentration of the agent in the fluid downstream of the injection point. 15 The pump may be controlled by a variable speed drive and/or an Orp controller included in the selection means. Preferably the agent is iodine. Advantageously the fluid might be water. In another aspect of the invention there is provided a dosing mechanism for dosing a fluid flow in a fluid flow conduit with an agent, the mechanism including: 20 a supply conduit for carrying a selected volume of fluid from a fluid supply to the fluid flow conduit at an injection point; agent introducing means for introducing agent to the fluid within the supply conduit; and 471 5 an indicator means for providing an indication of the quantity of agent in the introducing means. In another aspect of the invention there is provided a dosing mechanism for dosing a fluid flow in a fluid flow conduit with an agent, the mechanism including: 5 a supply conduit for carrying a selected volume of fluid from a fluid supply to the fluid flow conduit at an injection point; agent introducing means for introducing agent to the fluid within the supply conduit; and a selection means for controlling the relative amount of fluid in the selected 0 volume in response to a concentration of the agent in the fluid downstream of the injection point. In another aspect of the invention there is provided a dosing mechanism for dosing a fluid flow in a fluid flow conduit with an agent, the mechanism including: a pump for providing pressure head for the fluid to flow through the fluid flow 15 conduit; a bypass line to take a selected portion of the fluid from the fluid flow conduit at a take off point downstream of the pump and return the selected portion to the fluid flow conduit at an injection point upstream of the pump such that fluid is driven through the bypass line by the pump; and 20 agent introducing means for introducing an agent to fluid within the bypass line. This advantageously allows selection means including a simple valve mechanism to be used - the dosing pump for providing pressure head for the fluid to flow through the bypass line is not required.

471 6 In another aspect of the invention there is provided a system for treating articles with an agent, the system includes a vessel for containing a volume of fluid in which the articles may be immersed, a fluid flow conduit fitted with a previously described dosing mechanism, and means for recirculating the fluid through the fluid flow conduit. 5 The various aspects of the invention are complementary and each may incorporate the features of the other aspects. Brief description of the drawings Figure 1 is a schematic representation of a dosing mechanism according to an embodiment of the invention; and 10 Figure 2 is a schematic representation of treatment system according to an embodiment of the invention; Figure 3 is a schematic representation of a variant of the dosing mechanism of Figure 1 having a secondary bypass line; Figure 4 is a schematic representation of a dosing mechanism according to an 15 alternative embodiment of the invention; and Figure 5 is a schematic representation of a dosing mechanism according to a further embodiment of the invention. Component listing 1. Variable Speed Drive (VSD) 20 1'. Controller 2. Load Cell 3. Iodine Crystals Canister 4. Dosing Pump 4'. Control valve 25 5. Iodine Specific Electrode 6. Flow Switch 471 7 7. Tank 8. Agitation Pump 9. ORP Controller 10. Secondary bypass line 5 12. Take off point 13. Injection point 14. Mains Flow Pump 15. Modulating Valve 16. Non-Return Valve 10 17. Manual Valve 20. Fluid Flow Conduit 30. Bypass 30'. Water supply line 40. Pump 15 50. Water supply Detailed description of the embodiments Figure 1 shows a dosing mechanism according to an embodiment of the invention for dosing water with iodine. The mechanism includes fluid flow conduit 20 and bypass line 30. A pump (not shown) is positioned towards an upstream end of the 20 fluid flow conduit 20 and provides the pressure head for the fluid to flow through the conduit 20. A portion of the fluid is drawn from the fluid flow conduit 20 from the pump inlet 12 and returned to fluid flow conduit at the pump outlet 13. Dosing pump 4 is positioned in the bypass 30 and drives fluid through the bypass 30. Canister 3 is positioned along the bypass line 30 downstream of dosing pump 4. 25 The canister is apertured to permit water to flow therethrough and contains a quantity of iodine crystals such that the water leaving the canister is substantially saturated with iodine. Water from the bypass line 30 is returned to the fluid flow conduit 20 at the pump outlet 13 and mixes with the water in the conduit to produce a dilute iodine solution.

471 8 It is desirable to limit the water flow through the iodine canister 3 to 5 litres per minute, so as not to push iodine crystals out through the discharge port by over agitation. A preferred method of achieving this is illustrated in Figure 3. Secondary, bypass 5 line 10 is arranged in parallel to the canister 3. In a preferred arrangement the restriction in bypass line 3 is adjusted such that when dosing pump 4 is at its maximum output, the maximum desirable water flow through canister 3 (5 litres per minute) is achieved. In this way the full range of the pumps' speed can be used and thereby the ultimate control of the total amount of water flowing through bypass line 30 can be more accurately 10 controlled. Another advantage of this arrangement is that if fluid from the bypass line 30 is already somewhat diluted before returning to the injection point 13. The illustrated secondary bypass line 10 draws fluid from immediately upstream of canister 3 and returns fluid to bypass line 30 immediately after canister 3. It is also possible that bypass line 30 could be plumbed from immediately before canister 3 directly to fluid flow 15 conduit 20 to have similar results. A single iodine specific electrode 5 extends into conduit 20 at a location downstream of the pump outlet 13. An iodine specific electrode 5 has a built in earth probe to ground any current in the water. The iodine specific electrode 5 produces a signal indicative of the concentration of iodine in the fluid within the conduit 20. An 20 Oxidisation Reduction Potential (ORP) controller 9 cooperates with the electrode 5 to produce a millivolt signal. The ORP controller sends either a 0 to 20mA or 4 to 20mA signal to the variable speed drive 1. The ORP controller 9 provides an indication of oxidizing effect. A variable speed drive 1 controls the dosing pump 4 in response to the signal from electrode 5 (via the ORP controller) thereby controlling the concentration of 25 iodine in the fluid leaving conduit 20. The variable speed drive 1 controls the speed of the pump to be inversely proportional to a variation in the measured down stream concentration of iodine (as indicated by electrode 5) from a preselected desired concentration, i.e. if electrode 5 indicates that the concentration of iodine is too high, the variable speed drive 1 slows 30 the pump to reduce the volume of fluid travelling through bypass 30 and thereby 471 9 reduces the amount of iodine being dosed into conduit 20 via injection point 13. More sophisticated program logic may also be used. For example a delay corresponding to the transit time from the canister 3 to the electrode 5 may be introduced to minimise overcorrection of errors. By having an allowable concentration range in which the speed 5 of the pump is not adjusted the incidence of the pump continuously changing speed (which is sometimes referred to as "hunting") can be reduced. Load cell 2 provides a signal indicative of the weight of canister 3. In use canister 3 has a fixed internal volume which is full of iodine crystals and water. The rate and amount of dissolution of the iodine crystals in the water will depend on the residence 0 time of the water in the canister and the solubility of the iodine in the water. This depends not only on the temperature and pH of the water but also the other solutes in the water which will vary with time. As the iodine crystals are depleted the amount of water in canister 3 increases. As the iodine crystals are denser than water the weight of the canister will reduce as the iodine crystals are depleted. The load cell 2 thus provides 5 an indication of the consumption of iodine crystals, and with calibration can provide an indication of when the iodine crystals will be entirely depleted. This in turn allows for efficient replenishment of the canister before the iodine crystals are entirely depleted (thereby avoiding undosed water leaving conduit 20) and without the expense of removing partially filled canisters. 20 Flow switch 6 is positioned along conduit 20 intermediate of the pump outlet 13 and electrode 5. Flow switch 6 controls VSD 1 via a signal to the VSD 1 when the conduit 20 is flowing and this signal will make the VSD 1 start dosing. Figure 2 illustrates a treatment system incorporating the dosing mechanism of Figure 1. Dosed water is directed from a downstream end of conduit 20 into tank 7. 25 Water is drawn from tank 7 by agitation pump 8 and directed into an upstream end of conduit 20. This arrangement provides tank 7 with a supply of water having a controlled concentration of iodine. This is useful, for example for sterilising tomatoes. Figure 4 illustrates another embodiment of the invention. The embodiment of Figure 4 differs from the embodiment of Figure 1 in that the flow of fluid through the 471 10 bypass line 30 is reversed. The take off point 12 is positioned along the fluid flow conduit 20 downstream of the pump 40. Fluid flows from the take off point 12 along bypass line 30 and is returned to the fluid flow conduit 20 at injection point 13 which is upstream of the pump 40. The pump 40 provides a pressure head for the fluid to flow 5 through the conduit 20. The take off point 12 and the injection point 13 are positioned on either side of pump 40 and are therefore exposed to a pressure differential. The pressure differential drives fluid through bypass line 30 without the need for a separate dosing pump. Valve arrangement 4' restricts the flow through bypass line 30 and is responsive the controller 1' which is ultimately responsive to the iodine concentration 0 signal from the electrode 5. This embodiment advantageously functions without the need for a separate dosing pump. Another advantage of this arrangement is that fluid downstream of the injection point 13 is drawn into the bypass line 30 such that the electrode 5 may be positioned intermediate the take off point 12 and the canister 3 or along a secondary bypass line 5 bypassing the canister 3. Figure 5 illustrates yet another embodiment of the invention. This embodiment differs from the embodiment illustrated in Figure 4 in that the take off point 12 has been replaced with a water supply 50. It will be understood that the invention disclosed and defined in this specification 20 extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. It will also be understood that the term "comprises" (or its grammatical variants) as used in this specification is equivalent to the term "includes" and should not be taken 25 as excluding the presence of other elements or features.

Claims

1. A dosing mechanism for dosing a fluid flow in a conduit with an agent, the mechanism including: a bypass line for taking a selected portion of the fluid from the fluid flow conduit 5 at a take off point and returning the selected portion to the fluid flow conduit at an injection point; an agent introducing means for introducing an agent to the fluid within the bypass line; and an indicator means for providing an indication of the quantity of agent in the 0 introducing means; selection means for controlling the amount of fluid in the selected portion relation to the flow in the conduit in response to a concentration of the agent in the fluid downstream of the invention point; wherein an agent specific electrode is positioned downstream of the injection .5 point for providing an indication of the concentration of agent and the selection means is responsive thereto.

2. The mechanism of claim 1 wherein the indicator means provides an indication of the weight of the agent introducing means.

3. The mechanism of claim 2 wherein the indicator means includes a load cell. 20

4. The mechanism of claim 1, 2 or 3 wherein the agent introducing means is a canister having apertures to permit fluid to flow therethrough and containing a quantity of solid agent.

5. The mechanism of any one of the preceding claims wherein the injection point is downstream of the take off point. 25

6. The mechanism of any one of claims 1 to 5 wherein the selection means includes a pump positioned along the bypass line. 12

7. The mechanism of claim 6 wherein the selection means includes a variable speed drive for controlling the pump.

8. The mechanism of claim 7 wherein the selection means includes an ORP controller for providing a signal to the pump. 5

9. The mechanism of any one of the preceding claims having a secondary bypass line bypassing the agent introducing means to limit fluid flow through the agent introducing means.

10. The mechanism of claim 9 wherein the agent introducing means and secondary bypass line have a relative impedance selected such that a maximum desirable fluid 0 flow through the agent introducing means corresponds to a maximum selected portion.

11. The mechanism of any one of the preceding claims wherein the agent is iodine.

12. The mechanism of any one of the preceding claims wherein the fluid is water.

13. The mechanism of claim 6 wherein an agent specific electrode is positioned downstream of the injection point for providing an indication of the concentration of 5 agent and the selection means is responsive thereto.

14. The mechanism of claim 1 wherein the agent introducing means is a canister having apertures to permit fluid to flow therethrough and containing a quantity of solid agent.