LIQUID SOLVENT

This invention relates to the production of solutions of a gaseous solute in a liquid solvent.

BACKGROUND

The invention was devised to produce dilute sulphurous acid (solute sulphur dioxide, solvent water) on demand for use as a disinfectant, deodouriser and/or preservative and is described hereinafter primarily with reference to that application. It will be appreciated however that it is equally applicable to the production of other solutions from appropriate solutes and solvents.

SUMMARY OF THE INVENTION

The invention consists in apparatus for dissolving a gaseous solute in a liquid solvent comprising an operative chamber, a lute chamber of lesser capacity than the operative chamber, a transfer duct extending from the operative chamber to the lute chamber, an outlet duct extending from the lute chamber above the

outlet of the transfer duct therein to the exterior of said chamber, solvent supply means to admit solvent into the operative chamber from a pressurised solvent source, solute supply means to release solute into the operative chamber from a pressurised solute source, first valve means responsive to the liquid level in the operative chamber controlling the in-flow of solute and second valve means to control the in-flow of solvent.

When a gaseous solute is dissolved in a liquid solvent the resultant solution exhibits a vapour pressure which varies (for any particular combination of solute and solvent) in accordance with the concentration of the solution.

Thus the equilibrium concentration in the operative chamber depends on the pressure within that chamber (in particular in the head space above any accumulated solution therein) . That pressure may be determined in apparatus according to the invention by the altitude of the lute chamber relative to the operative chamber or to be more precise, the altitude of the inlet in the lute chamber of the outlet duct relative to the altitude of the liquid surface in the operative chamber.

Thus the physical parameters of the apparatus determine the concentration of the solution produced. BRIEF DESCRIPTION OF DRAWINGS

By way of example, embodiments of the invention are described in more detail hereinafter.

Figure 1 represents a simple form of the apparatus embodying the present invention.

Figure 2 represents a second embodiment of the invention being an automated apparatus.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown in Figure 1, the first embodiment of the invention comprises an operative chamber (1) connected to a smaller lute chamber (2) via a transfer duct (3). In this embodiment the two chambers are separated by a septum wall.

An outlet duct (4) extends from an open end within the lute chamber near the septum wall through the floor of the lute chamber.

The transfer duct (3) is in liquid tightly connected to the septum wall, and the outlet duct (4) is in liquid tightly connected to the floor of the lute chamber.

The roof of the operative chamber is furnished with two inlet (5,6) and one outlet port (9) structures.

One inlet port structure (5) comprises a spray nozzle connected externally to a pressurised source of solvent, in this instance the municipal water mains. A manually operable valve (7) is provided in the external connection to enable the in-flow of solvent to be controlled.

For preference the spray nozzle (5) is located centrally of the chamber roof and admits solvent as a

fine, misty, low-pressure spray.

The other inlet port (6) is a micro-valve connected externally to a pressurized source of solute, in this instance a cylinder of liquefied sulphur dioxide. For preference a further manually operable isolating valve (8) is provided in the connection between the micro-valve and the gas cylinder.

The "micro-valve" is a well known type of valve which opens and closes in response to thrust from a thrustor such as a push-rod or the like upon an operating element; it is characterised by the smallness of the movement of the thrustor needed to operate the valve.

The outlet port structure (9) is a manually operable, self-closing vent valve. It is preferably situated at the highest point of the roof of the operative chamber.

A float (10) is disposed within the operative chamber. It carries an upwardly extending push-rod (11) adapted to operate the micro-valve (6). The float (10) is guided to ensure correct engagement of the micro-valve (6) by the push rod (11).

The embodiment depicted in Figure 2 comprises an operating chamber (1) attached to a smaller lute chamber (2) via a transfer duct (3) . Above the level of the transfer duct (3) is an outlet (4) extending from the lute chamber (2) . A solvent inlet (5) supplies solvent

to the operating chamber (1) and a solute inlet (6) supplies solute. Both inlets may contain pressure sensitive valves (7,8). The operating chamber further contains an air purge valve (9) in its roof, and a float (10) attached via a push rod (11) to the micro-valve (6). The solute inlet lines attached to the inlet (6) may also contain shut off valves (12,13). The solvent inlet (5), preferably further also contains a pressure control valve (14). The solute inlet line and solvent inlet may be interconnected by a gas operated diaphragm valve (15) .

BEST METHOD OF PERFORMING THE INVENTION The operation of the apparatus may now be described. At initial start-up water is admitted to the operative chamber (1), with the outlet duct (4) temporarily blocked and the vent valve (9) open, until the apparatus is full of water and all air has been excluded.

The vent valve (9) is then allowed to close and the outlet duct (4) unblocked. Air will then bubble in through the outlet duct (4), and water will flow from the lute chamber (2) until an air filled head space is established in that chamber above the inlet end of the outlet duct (4). Thereafter there is a slow flow of water through the apparatus due to water issuing from the drowned spray nozzle.

The float (10) is at this stage holding the micro-valve (6) open and the isolating valve at the gas

cylinder may be manually opened.

There is an immediate inrush of solute gas which expels water from the apparatus to create a head space in the operating chamber (1) and expose the spray nozzle (7). This also causes the float (10) to fall and may allow the micro-valve (6) to close.

However very shortly thereafter the dissolving of the solute in the water reduces pressure in the operative chamber (1) and water is sucked back from the lute chamber (2). This causes the float (10) to rise and opens the micro-valve (6) to admit more solute.

After a brief settling down period a substantially "steady state" condition is reached with both chambers having solution of required concentration therein and a steady flow from the lute chamber via the outlet duct equating with the in-flow of water via the spray nozzle. In the steady state condition the level in the operative chamber rises and falls regularly just enough to cause the float to open and close the micro-valve to control the in-flow of gas to suit the in-flow of water.

If the water in-flow is now halted the out-flow of solution stops almost immediately with the solution level in the operative chamber that at which the micro-valve is caused to close.

Should the water be again turned on the "steady state" condition is immediately re-established and further product flows from the apparatus. That is to

say further control of the production of solution is effected merely by turning the water on or off as the case may be.

Under the steady state condition the pressure in the head space in the lute chamber is atmospheric. The pressure in the head space in the operative chamber equals the equilibrium vapour pressure of the solution and is less than atmospheric by an amount equal to the head of liquid in the operative chamber above the liquid level in the lute chamber.

The liquid level in the lute chamber is determined by the level in the operative chamber at which the float operates the micro-valve. Thus the concentration of the solution produced is determined by the effective length of the push-rod or other thrustors.

If solutions of different concentrations or different ingredients are required it may be that the equilibrium vapour pressure needed is super-atmospheric. In that event the lute chamber may be positioned beside or above the operative chamber to provide a positive head space pressure therein.

In the preferred embodiment illustrated in figure 2, the solvent inlet line is fitted with a pressure control valve (14) which acts to keep the pressure of the solvent constant at the diaphragm valve (15). Should the pressure of the solute inlet line be sufficiently increased, the diaphragm valve acts to

prevent the flow of solvent in the solvent line.

Conversely, when the solute pressure decreases, the diaphragm valve acts to open the solvent line, thus ensuring that no solute is dispensed into the operative chamber without sufficient solvent.

In operation, as the fluid level in the operative chamber (1) rises, the float (10) rises and closes the inlet valve (6). Pressure rises in the solute inlet line thus closing the diaphragm valve and closing the solvent inlet. As the level in the operative chamber

(1) drops, the float (10) descends, opening the valve

(6) and allowing solute to flow through the solute lines. The pressure reduces, opening the diaphragm valve (15), thus opening the solvent line.