GB2084476A

GB2084476A - Liquid mixing

Info

Publication number: GB2084476A
Application number: GB8032027A
Authority: GB
Original assignee: BOC Nowsco Ltd
Current assignee: BOC Nowsco Ltd
Priority date: 1980-10-03
Filing date: 1980-10-03
Publication date: 1982-04-15

Abstract

Apparatus for mixing a surfactant with water (or many other two liquids) includes a surfactant supply (16) connected to the inlet of an air-driven dosing pump (18) and a water supply which passes through a water meter (48) to a mixing, injector T-piece (40) from which the mixed surfactant and water is delivered to a consumer apparatus which may be remote from the mixing apparatus. The pump and the various control valves and pressure gauges may be mounted within a portable enclosure (10). <IMAGE>

Description

SPECIFICATION Liquid mixing This invention relates to apparatus for and a method of mixing two liquids such as a liquid surfactant and water.

Many apparatus for mixing liquids have been proposed but where the proportion of one liquid relative to the other is small such apparatus do not always provide the necessary control of the quantity of the said one liquid particularly where the apparatus is for use outside a laboratory. The degree of control is particularly important if the one liquid is costly, such as many surfactants.

According to the present invention there is provided apparatus for mixing two liquids comprising means for providing a supply of one liquid at substantially constant pressure and a controllable flow rate, means for supplying the second liquid at a substantially constant pressure, and injector means for receiving the two liquids from the said supply means whereby to mix the liquids in constant proportion.

According to the present invention there is further provided apparatus for mixing two liquids including means for supplying a first liquid at a substantially constant pressure and at a controllable flow rate, means for supplying a second liquid at a substantially constant pressure and a controllable flow rate, mixing means connected to receive the two liquids from both supply means, said second means including a fluid-driven pump.

According to the present invention there is still further provided apparatus for mixing two liquids including means for supplying a first liquid at a substantially constant pressure and at a controllable flow rate, means for supplying a second liquid at a substantially constant pressure and a controllable flow rate, and a T-piece mixer connected to receive the two liquids from both supply means.

According to the present invention there is yet further provided apparatus for mixing two liquids comprising means for providing a supply of one liquid at substantially constant pressure and a controllable flow rate, means for supplying the second liquid at a substantially constant pressure, and injector means for receiving the two liquids from the said supply means whereby to mix the liquids in constant proportion, said second liquid supply means including a pump of which the strike rate determines the mass flow output.

According to the present invention there is yet further provided apparatus for mixing two liquids including means for supplying a first liquid at a substantially constant pressure and at a controllable flow rate, means for supplying a second liquid at a substantially constant pressure and a controllable flow rate, mixing means connected to receive the two liquids from both supply means, said second means including a pump arranged to shut down automatically in the event that back-pressure downstream of the pump rises beyond a predetermined level.

According to the present invention there is yet further provided a portable unit for mixing water and a surfactant including means for supplying water at a substantially constant pressure and at a controllable flow rate, an air-driven pump for supplying the surfactant at a substantially constant pressure and a controllable, monitored, flow rate, a mixing T-piece connected to receive the water and surfactant, releasable couplings to the supply means for the liquids, a non-return valve in each supply pipe from the supply means to the T-piece and a flow meter in the watersupply piping.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing, in which: Figure 1 is a circuit diagram of one embodiment of liquid mixing apparatus in accordance with the invention; and Figure 2 is a diagram illustrating a portion of the circuit of Figure 1 but also indicating the pressures at different points in the circuit.

Referring first to Figure 1 the apparatus is enclosed in an appropriate portable enclosure 10 which can be used at a location remote from a consumer apparatus for the liquid mixture produced. Conveniently, the gauges referred to hereinafter can be mounted on the door of the enclosure.

Externally of the enclosure, the apparatus requires connection to a water supply 12, which may be the mains supply or if the pressure is inadequate or liable to fluctuate, a pump will be incorporated in that supply. A compressed air supply 14 is also required and this may take any convenient form such as an air compressor or an air bottle of suitable capacity. If a compressor is used it can be disposed remote from the site. A surfactant supply 16 is also provided in a convenient, non-pressurized container.

In the preferred embodiment, the surfactant is pressurized by a dosing pump 18 for example, where relatively low output pressure is required that marketed by Pump s General under their trade name "PAGEBOY SFD 15" has been found suitable. It is possible with pumps of this kind to control accurately the output and the pump itself is operated by compressed air. The pump 18 is supplied with compressed air from the air supply 14 througha quick-release coupling 20, an in-line filter with integral drain, a pressure-reducing regulator 24, a pressure gauge 26 and narrow bore flexible nylon tubing 28 to the air intake of the pump 18.

The surfactant supply 16 is connected, again through a quick-release coupling 30 to a liquid intake of the pump 1 8 and pressurized surfactant is delivered to large bore flexib'e nylon tubing 32 which leads to a fine control needle valve 34. The driving compressed air of the pump is exhausted through a conventional silencer 36. The length of large bore tubing 32 between the surfactant outlet of the pump and the fine control needle valve 34 is made sufficient to ensure that any pulsations generated by the pump are properly damped upstream of the needle valve.

The needle valve 34 is itself connected at its outlet to a pressure gauge 36, a non-return valve 38 and a surfactant injection T-piece 40 which also receives the water supply.

The water supply 12, whether derived from a pump or directly from the mains is connected through a quick-release, coupling 42 to a pressure gauge 44, a conventional hand control valve 46 and a flow meter 48 mounted horizontally and giving a visual indication of the flow rate. The outlet of the flow meter is connected by large bore nylon tubing 50 through a pressure gauge 52 to the water inlet of the injection T-piece 40.

The injection T-piece is of conventional construction and the outlet is connected through a further quick-release coupling 54 to the pipe leading to consumer apparatus, which may be at a location remote from the mixing apparatus.

The operation of the apparatus will now be described, partly in conjunction with Figure 2.

When the portable enclosure 10 is brought to site, connections are made to the water, air and surfactant supplies 12, 14, 1 6 with the aid of the corresponding quick-release couplings. For correct, most economical, running the pressures at the various points in the apparatus are critical and the pressure water injection (pawl) is the only one which cannot readily be increased although the flow rate can, of course, be controlled by the hand control valve 46 immediately upstream from the flow meter 48. However, any major fluctuations in the water pressure will be monitored by the pressure gauges 44, 52 upstream and downstream of the flow meter and if necessary appropriate remedial action can be taken.

The air-driven dosing pump 18 operates over a wide range of applied driving air pressures (pea) and this range determines the pressure of the surfactant to be injected into the water flow at a pressure Psl. The surfactant is discharged from the pump 18 at a pressure approximately equal to the applied pressure (PA; but owing to frictional losses in the output line 32 and the control needle valve 34, pressure is finally somewhat less at the injector 40. The pressure (pal) of the surfactant must be slightly higher than the water line pressure (pal) at the injector to enable injection to take place. Pwl should be greater than PA and P greater than P,,.

In the event that a substantial back pressure arises downstream of the outlet coupling 54 of the surfactant/water mixture the pressure in the surfactant will correspondingly rise and this causes an automatic shut down of the dosing pump 1 8 thereby avoiding incorrect dosing. This is important in avoiding changes in surfactant/water ratios which might otherwise arise if a slug of surfactant were to be left in the delivery line at the end of an operation which would affect the ratio on start-up.

The equipment being supplied with the water/surfactant mixture determines the water flow rate required and the hand control valve is all that is necessary to vary this.

Once the various pressures have been correctly set, the fine control needle valve 34 is adjusted to supply a fixed quantity of surfactant which can then be injected into the water supply at the required flow rate.

Since the dosing pump 18 displaces a fixed, known, volume of liquid per stroke, monitoring of the stroke rate will give the injection flow rate of the surfactant. Alternatively, in a modification, the necessary monitoring can be provided by a suitably valved calibrated vessel at the outlet of the surfactant supply. A flow meter is not included in the surfactant line owing to the inherent inaccuracy at low flow rates and sensitivity to viscosity changes due to temperature variations.

It has been shown that the mixing of surfactant into the water stream is adequately thorough by means of the conventional injectorT-piece 40 but it can be further enhanced if necessary by the addition of an in-line motionless mixer (not shown) coupled directly downstream of the outlet of the injection T-piece.

If it is known that the water supply pressure will vary to a substantial extent a pressure-regulating valve may be incorporated into the water supply line upstream of enclosure.

As an alternative to a calibrated vessel for monitoring the surfactant supply, a pneumaticallyoperated pulsation counter may be used with the dosing pump to give an instantaneous visual display of the surfactant injection rate.

While the apparatus hereinbefore described is primarily intended for blending water with a surfactant, it will be readily understood that the apparatus can also be used for blending many other liquids.

The apparatus hereinbefore particuiarly described has the advantage that it is light in weight and therefore easily transportable. The cost can be kept small owing to the simplicity of the component parts, but the control of liquid/liquid ratios can be kept precise and constant once the operating pressures have been set.

Claims

1. Apparatus for mixing two liquids comprising means for providing a supply of one liquid at substantially constant pressure and a controllable flow rate, means for supplying the second liquid at a substantially constant pressure, and injector means for receiving the two liquids from the said supply means whereby to mix the liquids in constant proportion.

2. Apparatus for mixing two liquids including means for supplying a first liquid at a substantially constant pressure and at a controllable flow rate, means for supplying a second liquid at a substantially constant pressure and a controllable flow rate, mixing means connected to receive the two liquids from both supply means, said second means including a fluid-driven pump.

3. Apparatus for mixing two liquids including means for supplying a first liquid at a substantially constant pressure and at a controllable flow rate, means for supplying a second liquid at a substantially constant pressure and a controllable flow rate and a T-piece mixer connected to receive the two liquids from both supply means.

4. Apparatus for mixing two liquids comprising means for providing a supply of one liquid at substantially constant pressure and a controllable flow rate, means for supplying the second liquid at a substantially constant pressure, and injector means for receiving the two liquids from the said supply means whereby to mix the liquids in constant proportion, said second liquid supply means including a pump of which the strike rate determines the mass flow output.

5. Apparatus for mixing two liquids including means for supplying a first liquid at a substantially constant pressure and at a controllable flow rate, means for supplying a second liquid at a substantially constant pressure and a controllable flow rate, mixing means connected to receive the two liquids from both supply means, said second means including a pump arranged to shut down automatically in the event that back-pressure downstream of the pump rises beyond a predetermined level.

6. A portable unit for mixing water and a surfactant including means for supplying water at a substantially constant pressure and at a controllable flow rate, an air-driven pump for supplying the surfactant at a substantially constant pressure and a controllable, monitored, flow rate, a mixing T-piece connected to receive the water and surfactant, releasable couplings to the supply means, for the liquids, a non-return valve in each supply pipe from the supply means to the T-piece and a flow meter in the watersupply piping.