AU8322598A - Mixing and dispensing system - Google Patents

Description

-1I- RM0011 Rgulation,72-

AUSTRALIA

Patents .ct 1I990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Name of Applicant: Actual Inventors: Address for service TECHNICFIEM PTY LTD James Garnilis and Emmanuel ANTHONY in Australia: CARTER SMITH BEADLE 2 Railway Parade Camberwell Victoria 3124 Australia Invention Title: MIXING AND DISPENSING SYSTEM Details of Associated Provisional Application: P09 101 filed 10 September 1997 The following statement is a full description of this invention, including the best method of iperorming it known to us TITLE MIXNG AND DISPENSING

SYSTEM

This invention relates to dispensing of aqueous solutions and a mechanism of creating the solution to be dispensed in a single continuous process.

There are many situations where a solution, prepared manually or automatically by mixing water and a chemical, needs to be dispensed in a single continuous operation. For example, a solution may need to be applied under high or low pressure to a surface to clean the surface. In other situations the solution is prepared for storage in a suitable container or the reservoir or conduit of a machine that accepts the solution as part of that machine's process.

Engine coolants often need to be diluted with water before introduction to the cooling system of automotive and other machinery. In other applications, *i disinfectant chemicals are diluted before application to surfaces or mixed proportionately with water as they are charged, for example into cooling towers.

The automatic proportional mixing of water and chemicals is commonly undertaken commercially by a range of methods which, on examination, reduce to three broadstream approaches.

The first of these approaches involves the metering of a chemical additive into a water stream which itself is monitored by flowmeter, for example, to provide by it: he individually metered parameters, a proportional mix. Chemical metering is typically achieved with a diaphragm or positive displacement pump which can provide pulsed signals related to flow rate.

oo* Secondly, a proportional mix of a chemical and water can be achieved by employing a venturi device fitted to the water supply line. By Bemoulli's principle, an additive introduced into the water stream via the venturi can be shown, under certain conditions, to follow a mix ratio of fixed proportionality to the water stream itself.

Thirdly, many combinations of the two approaches described above are commonly used in conjunction with an electronic signal that is generated by the Swater/chemical mix to provide a means of regulating the proportionality ofthe mix.

For example, a pH electrode can be used to regulate the addition of a mineral acid BGCJ .ll 2,CAP 9 19 ri j r

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-3to water. In this case, a property of the mix, pH, regulates the proportionality and therefore the role of the pumps or venturis changes from a metering means to that of delivery means.

Proportional mixing of chemicals and water however remains a problem in terms of the cost versus accuracy tradeoff. In the cases one and three above, highly accurate proportioning is possible, however, cost remains a significant disincentive to implementing such automation particularly on systems of medium to small scale.

For this reason simple venturi devices are most commonly employed as the cheapest means of achieving proportional mixing; but venturis are inherently inaccurate for the following reasons.

When a venturi is introduced to a fluid stream, for the purpose of drawing liquid into the stream, the pressure at the venturi throat (the narrowest point), must be less than one atmosphere to draw in liquid situated under the venturi. As the container of liquid drawn in diminishes in volume, the venturi must work against an 15 ever increasing "head" before the liquid is drawn. This results in a constantly changing proportionality in the mix as the liquid supply diminishes. Although compensation can be made for this constant change, by, for example, changing the venturi throat diameter via a needle valve, such adjustments are impractical for automated systems.

20 A second problem of proportionality erodes the value of venturis as metering devices. It is frequently the case that the drawn liquid is viscous. The changing flow rate of a viscous liquid as temperature changes introduces a second flow variable that changes the proportionality in a water/liquid mix. As viscosity and "head" are independent properties of the drawn liquid, the needle or other orifice adjustment method of sustaining a constant proportionality is not feasible for systems requiring mix accuracy in an essentially automated system.

It is an object of this invention to provide an apparatus which provides accurate proportional mixtures of one or more chemical components with water which are independently introduced into the solution and avoids the problems associated with mixing and dispensing solutions in two separate operations.

BGC:JHI2449.CAP 9 Sc r r 1i9 S Accordingly the invention provides a mixing and dispensing system including a container, and a mixing circuit having an outlet to the container and a conduit. the conduit being connected to a pump means for circulating liquid through the mixing circuit, the container having a concentrate indicator means proximate to the inlet conduit of the mixing circuit, the mixing circuit having a concentrate inlet for a concentrate liquid to be mixed with liquid in the mixing circuit, the concentrate inlet having flow control means responsive to the concentration indicator means for controlling the amount of concentrate added to the mixing circuit.

In a preferred form of the invention the pump means defines a low pressure section and a high pressure section in the mixing circuit. The mixing circuit may be provided with an outlet to the high pressure section and a means to direct liquid in the high pressure section through the outlet.

The container preferably has a liquid diluent inlet and a means for maintaining a constant head of liquid in the container.

The flow control means may include a valve in the concentrate line operable by a controller. The controller may be responsive to a signal from the concentration indicator means and the valve in the concentration line is adjusted to control the amount of concentrate being added through the concentrate lines.

The mixing circuit may further include a venturi device in which the 20 concentrate line is preferably connected to the low pressure region of the venturi.

The means to direct flow in the mixing circuit may include a reduction valve in the mixing circuit and an outlet valve to regulate flow through the high pressure outlet. To dispense high pressure liquid, the outlet valve is opened and the reduction valve is closed so that high pressure liquid is dispensed through the high pressure outlet. The container may also have a low pressure outlet in the bottom region thereof, the pressure of the liquid discharged through the low pressure outlet being equivalent to the hydrostatic head of liquid above the outlet.

In operation the pump means circulates liquid through the mixing circuit.

Concentrate is added to the liquid circulating in the mixing circuit and discharged from the mixing circuit into the container. The rate at which concentrate is added BGC1jI97HP qT.CAP

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*J'K to the mixing circuit is dependent on the concentration parameters measured by the indicator means proximate to the inlet conduit of the mixing circuit. Once the indicator means signals a predetermined concentration, the high pressure outlet may be opened to dispense high pressure diluted concentrate.

As liquid is discharged through the high pressure outlet, diluent liquid is added through the constant head means in the container and the rate at which concentrate is added to the mixing circuit varied depending on the signal received from the indicator means.

The apparatus in accordance with the invention provides a means whereby a solution can be mixed and dispensed on demand. Since the solution to be dispersed may be prepared at the same time as it is needed, only a small mixing container is required. This reduces the storage space required and problems associated with storing mixed solutions.

The apparatus also allows the concentration of a solution being dispensed to be changed in a much shorter time interval than would otherwise be necessary in situations where mixing and dispensing is conducted in two separate operations.

Thus the present invention is able to provide a means whereby a solution may be prepared and stored for immediate or use a short time later. Furthermore, the invention is able to provide a means to deliver the solution at a predetermined S. 20 concentration under a range of pressures which allows either the simple transfer of S a solution to an outside point or as a spray under pressure or simultaneously S replacing transferred solution with a continuously replenished supply.

While the invention has been described with regard to aqueous solutions, it would be apparent to those skilled in the art that the invention is equally applicable to use with non aqueous liquid solutions.

Other features objects and advantages of the present invention will become apparent from the description of the following preferred embodiments and drawings in which:- Figure 1 is a section through one embodiment of the apparatus according to "30 the invention, *GCJRJ2CA 9 SePiabc 1991 BGCWI~i4fA i IL~_ ~I_ Figure 2 is a section through a second embodiment of the apparatus in accordance with the invention, and Figure 3 is a third embodiment of the apparatus in accordance with the inventions.

Referring to Figure 1, in one embodiment of the invention, the apparatus includes a container body 12 which forms part of a mixing circuit 13, having an inlet conduit 13a and an outlet 13b to the container body 12. The apparatus may also include a pump means 14, pressure reduction valve 26, venturi, 15a, fitted with non-return valve 15b and solenoid valve 27.

Container body 12 is fitted with a diluent or water supply line 16 which is independently regulated by, for example, float valve 17, a ball valve 18, at the base of container body 12, allowing access to solution under gravity, and an electronic :sensing probe 19, located within the container near the connection of inlet conduit 13a to the container.

To non-return valve 15b is connected a chemical concentrate supply line incorporating a solenoid valve 21 and chemical detector 22. The two signal devices 19 and 22 are connected to electronic controller 23 which regulates the output to pump 14 and solenoid valve 21 according to set points allocated on control panel, 24. Solenoid valves 27 and 18 may also be connected to controller 23. Apparatus 10 may operate as follows.

Water is admitted to container 12 via supply line 16 and fills container 12 to waterline 29, determined by float valve 17. Controller 23 is switched on after a desired proportionality is set on control panel 24, initiating through controller 23, a reading of the chemical composition of container 12 via sensing probe 19.

To satisfy the desired proportionality condition set on panel 24, controller 23 causes pump means 14 to recirculate water within mixing circuit 13 which terminates in container body 12 at a point below water line 29, established by float valve 17, and above sensing probe 19. Simultaneous with the initiation of pump 14, controller 23 causes solenoid valve 21 to open, admitting chemical liquid to enter mixing circuit 13 via chemical detector 22, venturi 15a and non-return valve BGCJHR2491..CAP 9 3qtesbe- 19 -7- Once open, solenoid valve 21 continues to admit chemical liquid into mixing Scircuit 13 and ultimately into container body 12 under the influence of pump means 14 in conjunction with venturi 15a. It is important to note that the action of ventur is designed only to deliver chemical liquid into the mixing circuit 13 and not to meter said liquid. For this reason, the viscosity and how this influences flow rate of the drawn chemical liquid or the changing "head" of the drawn chemical is irrelevant, as the metering process is independent of the drawing capacity of venturi r 91 r o I r rc ro ,r rrr e o r 1 ori When the desired proportionality condition set in controller 23 ihas ee achieved, solenoid valve 21 is closed. Controller 23 then initiates a timed duty cycle on pump means 14 to ensure complete mixing between drawn chemical liquid and water present throughout loop 13 and container body 12. Any solution passing sensing probe 19 that fails to satisfy the set proportionality condition in controller 23 causes the controller to repeat the chemical uptake cycle and the mixing cycle 15 until all solution consists of the correct proportional mixture of chemical liquid and iattr When the mixing duty cycle has elapsed and the proportionality of the mixture in container 12 satisfies the set-point on panel 24, controller 23 switches pump means 14 off but continues to monitor the condition of the solution, in terms 20 of its chemical/water proportionality.

The proportional solution can now be dispensed from the apparatus either under gravity at exit valve 18, independent of pump means 14 or under pressure at exit valve 27 when the pump means is switched on.

A benefit in the arrangement of both exit valves is seen if it is observed that, provided, in each case, the valve opening is of fixed aperture, say, fully open, and only one valve is opened at a time, solution flow through a particular valve will remain constant indefinitely. The reason for this is that, in the case of solution dispensed via valve 18, the "head" is always constant by the action of float valve 17.

Since flow rate is determined by the product of pressure and aperture, the flow rate does not change over time. The same constancy of flow rate applies to solution SGCJH24497CP Spcm be 1991 i

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0 01 d dispensed via valve 27. In this case however the flow rate constancy is determined by the capacity of pump means 14 to maintain a constant "head" to the exit point, valve 27, provided its open aperture does not change. Clearly, the rates of solution flow will differ between valves 18 and 27 depending on the particular geometry of 5 apparatus 10, the capacity of pump means 14 and the chosen pressure setting of pressure reduction valve 26.

Therefore, controller 23 can equate flow rate and/or volume dispensed, because a flow rate calibration constant, k, can be determined for any particular pressure or "head" and valve aperture combination chosen for valve 18 or valve 27 within apparatus 10. Thus, apparatus 10 allows for dispensings to be determined accurately by employing only an internal timer in controller 23 and without requiring any further flow transducers to establish flow directly, or indirectly, by, for example, the use of a pressure transducer. Instead the simple relationship which follows will establish flow: 15 Solution Flow (litres) k x t where k is the calibrated solution flow rate, litres/minute, through a particular valve, and t is the elapsed time measured by internal timer in controller 23 over which the said valve remained open.

It is of increasing interest, as part of an information system, to establish the exact usage of additives to water that make up a solution being dispensed or transferred from an apparatus such as apparatus 10. Furthermore, water itself is an increasingly valuable commodity which needs to be accounted for by metering processes.

The ability of apparatus 10 to establish the exact usage of a dispensed or transferred mixture or solution, together with the continuous monitoring of solution strength via sensing probe 19, means that as the solution is dispensed, it is possible to determine the rate or quantity of chemical additive leaving apparatus To establish additive flow, in the context of the example above, the relationship establishing solution flow, is modified as follows: Additive Flow (litres)= Solution Flow x C k x t x C where k is the calibration flow constant in litres/minute for the valve in BGCJH:V4497.CAP 9 19ib question; t, the elapsed tir the valve stays open; C, t probe 19 as litres additive valve stays open.

ne measured by internal timer in controller 23 that he concentration of additive, measured by sensing !itre solution over the time duration t that the exit t r nir To establish the corresponding water flow from apparatus 10, the additive flow equation above is modified as follows: Water Flow (litres)= Solution Flow x (1 C) k x t x (1 C) where k, t and C represent the same parameters as the equations above.

It should be noted that, because controller 23 can be configured to output dispensing activity in terms of chemical flow (litres), apparatus 10 can be useful in delivering specific quantities of a chemical additive in the form of its solution. In such a case, the volume or strength of solution as such is not of primary importance because, for example, a further dilution is anticipated at a later stage.

This means that apparatus 10 could dispense solution via valve 18 driven by the constant "head" provided by float valve 17 with or without further additive entering container body 12. The same is true of dispensings via valve 27, for in both cases chemical flow is established via sensing probe 19 at the same time as solution flow constancy is being established. That is, the flow information processed from signals of sensing probe 19 are only meaningful in the context of solution flow constancy inherent in the configuration of apparatus It has been shown that constancy of solution flow, both at valve 18 and valve 27, makes it possible to interpret signals from sensing probe 19 in terms of solution flow or in terms of solution component flow; chemical additive flow and water flow.

It can be seen therefore that variation of solution strength on the basis of varying demand in solution strength from an external source, can be achieved by apparatus SAn example of such a requirement follows.

It is common in water treatment processes to monitor the pH of water prior to discharge to sewer in order to comply with discharge regulations. Should pH drift outside prescribed limits, chemical dosing of high pH or low pH chemicals (as the SGC-Jatj244.CAP I19 ~r~----~^~asas~3~apW~;r~7~iTNpll~~mn-- 10 case may be) are added to the- discharge. Typically, the rate of addition is modulated to the difference between actual pH and the target pH- Hence chemical dosing rates are ramped up and down to achieve balance as quickly as possible.

As it is sometimes preferable to vary not the rate of supply of a neutralising chemical, but the concentration, it can be seen that apparatus 10 can supply varying concentration of such a chemical, under constant flow, to achieve a target pH. In this instance, the proportionality setting is governed by the outside pH signal, which, translated in controller 23, results in modulation of valve 21 so as to vary solution strength in container 12 in relation to the incoming signal.

Response time is a major factor in many dispensing situations as the above example demonstrates. In that particular example, concentration response is a more Ssignificant factor than flow volume response. In such circumstances, apparatus is configured to maximise concentration response by restricting the volume of container body 12 and recirculation loop 13 to a minimum.

Where flow volume response is a major factor in performance, apparatus is configured to maximise volume of container body 12 and recirculation loop 13 consistent with solution concentration factors necessary to achieve response targets.

To this end, adjustments to pressure reduction valve 26, and outlet valves 18 and 27 are all variables in terms of pressure and aperture respectively, that will contribute 20 to flow volume response characteristics of the configuration of apparatus Apart from configurations where physical dimensions are varied to maximise flow performance, concentration flexibility or storage capacity, a second embodiment of the apparatus according to the invention is shown in Figure 2, which results in higher pressure stored solution.

In the embodiments of figures 2a and 3, features identical to the embodiment of figure 1 have ben given the same reference number.

Apparatus 11, as displayed in Figure 2 is essentially the same as apparatus displayed in Figure 1 with the exception that float valve 17 has been replaced by spring loaded one-way valve 30, which protrudes above water line 29 into head space 40. In addition, water supply line 16 is fitted with pressure reduction valve BGCJ'H tM97 CAP 11 31 which acts to maintain a constant regulated supply of water of fixed pressure into container body 12.

Water supply line 16 and recirculation loop 13 are joined on the intake side of pump 14 by two 3-way valves, 32 and 33. Valves 32 and 33 can be manual types or electrically actuated. If electrically actuated, controller 23 is used to set the valve position.

Because water entry into container body 12 is regulated to water line 29 under pressure determined by the setting of pressure reduction valve 31, container body 12 is a sealed container capable of sustaining water pressures common to industrial and domestic water supply pressures. The configuration of apparatus 11 described provides three advantages over apparatus Firstly, the overall pressure available at outlet valve 27 is higher for apparatus 11 than for apparatus 10 because the intake pressure is higher in the former case.

Secondly, after solution make-up to a preset proportionality has been achieved in apparatus 11 by the same process already described for apparatus proportionally mixed solution is available at outlet valve 18 at nearly mains water pressure.

Furthermore, higher potential solution flow rates are also available compared to an equivalent configuration of apparatus Thirdly, the two 3-way valves 32 and 33, when oriented to isolate container body 12 and place pump 14 in alignment with water supply line 16 via pressure reduction valve 31, and a bypass conduit, allow access of high pressure water to outlet valve 27. Thus, proportionally mixed solution and mains water can be delivered under pump assisted pressure to outlet 27 by diverting valves 32 and 33 to either supply.

The by-passing of high pressure solution stored in container 12 to access mains water and deliver it under pressure of pump 14 to exit valve 27 is seen to not interfere with stored solution. This is so because pressurised container body 12 impedes the flow of mains water into it and because in by-pass "mode" pump 14 can only be switched on by controller 23 simultaneous with exit valve 27 being opened. A K9 Sqlimbr 1993 ife.7 12 Figure 3, is a third embodiment of the apparatus according to the invention.

The apparatus shown in Figure 3 demonstrates an alternative method of delivery of a chemical liquid into the storage unit, container body 12 and mixing loop 13 other than by venturi.

In all respects, apparatus 12 follows the physical configuration of apparatus but with the following differences: 1. Uptake of chemical liquid occurs at section 44 on the suction side of pump 14, and integral in loop 13.

2. Exit valve 27 has been removed because unmetered solution could potentially access it.

3. Venturi 15a is not fitted, replaced by the section 44 mentioned above.

4. Pressure reduction valve 26 has been removed.

Apparatus 12 operates in the same way as described for apparatus 10 with the exception that high pressure solution is no longer available.

In all other respects, apparatus 12 provides the same flow signals and flow characteristics through exit valve 18, as does apparatus 10. Furthermore, the same constancy of solution proportionality is sustained by this embodiment of the invention, as apparatus It should be noted that whereas venturi devices fitted to a fixed high velocity I" stream of water can uptake a drawn liquid to a fixed limit, the present invention as embodied in apparatus 10, 11 and 12 is not confined to such limits. This is the case because solutions can be cycled around loop 13 via container body 12 indefinitely, and in so doing continue drawing from the chemical supply either through venturi 15a or suction 44, as the case may be.

The purpose of chemical detector 22 is now explained.

The possibility of chemical supply line 20 becoming empty would create a problem in the event controller 23 activated solenoid valve 21. Air, rather than chemical liquid, would then enter recirculation loop 13 and container body 12. In the event foam stabilising chemicals have been already drawn, dense foams develop BGCIHKMW7.CA 13 causing signal difficulties in sensing probe 19.

A typical chemical detector would be a conductivity cell since the conductivity of air is significantly different from that of most chemical liquids.

Sensing probe 19 is any electrical cell capable of providing an electrical signal in a wide range of concentrations of chemical solutions in water of the drawn chemical supplied through line Examples of sensing probes useful in embodiments of the invention discussed include: Conductivity Cell pH Electrode Capacitance Cell Optical Density Transceiver Ion Selective Membrane Electrode It is necessary for sensing probe 19 to have a temperature compensation capability 15 to render signals free of temperature related deviations in the output to controller 23.

Clearly, the range of probes that are suited to the function of sensor 19 as it applies to the invention is very wide. Any device capable of supplying an electrical signal versus concentration gradient will fulfill the application requirement in the context of the invention as described.

8 GC-JH:02449?CAP 9 1_- 0

Claims (13)

1. A mixing and dispensing system including a container, and a mixing circuit having an outlet to the container and a conduit, the conduit being connected to a pump means for circulating liquid through the mixing circuit, the container having a concentrator indicator means approximate to the inlet conduit of the mixing circuit, the mixing circuit having a concentrate inlet for receiving a concentrate liquid to be mixed with liquid in the mixing circuit, the concentrate inlet having flow control means responsive to the concentratation indicator means for controlling the amount of concentrate added to the mixing circuit.

2. The mixing and dispensing system according to claim 1, wherein the pump means defines a low pressure section and a high pressure section in the mixing circuit.

3. The mixing and dispensing system according to claim 2, wherein the mixing circuit is provided with a high pressure outlet from the high pressure section and the 15 means to direct liquid in the high pressure section through the high pressure outlet.

4. The mixing and dispensing system according to any one of claims 1, 2 or 3 wherein the container has a liquid diluent inlet and a means for maintaining a constant head of liquid in the container.

5. The mixing and dispensing system according to any one of the preceding 20 claims, wherein the flow control means includes a valve in the concentrate line operable by a controller.

6. The -mixing and dispensing system according to claim 5, wherein the controller is responsive to a signal from the concentration indicator means and the value in the concentration line is adjusted to control the amount of concentrate being added through the concentrate lines.-

7. The mixing and dispensing system according to any one of the preceding claims, wherein the mixing circuit includes a venturi device, said concentrate line being connected to a low pressure region of the venturi.

8. The mixing and dispensing system according to any one of claims 3 to 7, wherein the means to direct flow in the mixing circuit includes a reduction valve in BCEC:I244n.CAP 9 Squcibe 191 j r i ki R _a~RLW ~WlsS_~Si~e~_C 15 the mixing circuit and an outlet valve to regulate flow through the high pressure outlet.

9. The mixing and dispensing system according to any one of the preceding claims, wherein the container is provided with a low pressure outlet in the bottom thereof, the pressure of the liquid discharged through the low pressure outlet being equivalent to the hydrostatic head of liquid above the outlet.

The mixing and dispensing system according to any one of claims 1 to 6 and 9 wherein the inlet conduit is provided with said concentrate inlet.

11. The mixing and dispensing system according to any one of claims I to 9 wherein said diluent inlet is provided with a flow diverter for directing diluent liquid Sdirectly to said inlet conduit.

12. The mixing and dispensing system according to claim 1 wherein said flow diverter includes a diverting valve in each of said diluent inlet and said inlet conduit, and a bypass conduit connectingsaid diverting valves.

13- A mixing and dispensing system substantially as hereinbefore described with reference to one of embodiments illustrated in the accompanying drawings. DATED: 9 September 1998 CARTER SMITH BEADLE Patent Attorneys for the Applicant: TECHNICHEM PTY LTD BGCJtlU"97CAP