Block for chemically dosing a stream of fluid and an apparatus for housing the block

A block for chemically dosing a stream of fluid flowing past the block, the block comprising at least one surface for the fluid to flow past to dissolve and/or erode the block, wherein the block is shaped to enable the at least one surface to be dissolved and/or eroded without a substantial change in the area of the at least one surface.

FIELD OF THE INVENTION

The present invention relates to chemically dosing a stream of fluid. The present invention also relates to an apparatus used in chemically dosing a stream of fluid.

BACKGROUND OF THE INVENTION

There are numerous applications where chemicals, dissolved or suspended in a fluid, are required to be applied over large areas or volumes.

One such application is in fire fighting, where fire retardant foam may sometimes be employed to smother a fire, particularly in the case of electrical fires or flammable liquid fires (such as oil fires) in which water is not a suitable fire extinguishing material.

The chemical components of the fire retardant foam are typically dissolved or suspended in water, the foam readily forming as the water and chemicals are sprayed out of a nozzle. The primary component of the fire retardant foam is a surfactant, which readily foams when sprayed out of the nozzle. The concentration of the surfactant in the water is typically less than 1%. Some types of surfactants employed include synthetic surfactants such as alpha-olefin sulfonates, perfluorooctane sulfonate, perfluorooactanoic acid and protein based surfactants. Other components of fire retardant foams may include organic solvents such as trimethyltrimethylene glycol and hexylene glycol, foam stabilisers such as lauryl alcohol and corrosion inhibitors.

For hand held fire extinguisher cylinders, the foam components and water are held in a compressed volume, similar to the arrangement in an aerosol can. When operated, the compressed gas which compresses the water and foam components escapes through a valve, causing the application of a pressure on the water, driving it out of the cylinder through a nozzle. As this occurs, the foaming components form the foam.

For fire trucks, having a foam system, a foam tank containing water and the foam components is provided on board the fire truck. In this instance, however, the pressure required to drive the water carrying the foam components through a nozzle to form the foam is provided by the fire truck's onboard pump.

Although both these arrangements enable an operator to apply a controlled concentration of chemicals to produce a fire retardant foam, a significant disadvantage is that large volumes of water and these chemicals are required to be stored.

In more recent developments, solid blocks containing surfactants supported in a polyethylene glycol matrix have been employed to create fire retardant foams by placing the solid blocks in the path of a stream of water. Typically, the block is housed in a chamber at some point between a water source and a nozzle. As the stream of water passes around the block in the chamber, the block including the surfactant dissolves and/or erodes into the fluid. The rate of loss of material from the block is directly proportional to the exposed surface area of the chemical block. The fluid, now containing surfactant, may flow through a nozzle to create the fire retardant foam. A significant advantage of this arrangement is that it is not necessary to provide a large storage tank of water containing the foaming compounds. However, a noticeable problem in relation to such solid blocks is that the loss of material from the blocks into the fluid does not occur evenly over the surface of the block over time. It has been found that this problem causes a rapid reduction in the concentration of foaming agents in the fluid. It is consequently necessary to regularly replace the solid block in the chamber, without a substantial portion of the solid block having been used, in order to maintain the required concentration.

Another application where chemicals dissolved or suspended in a fluid need to be applied over a large area or volume is in the application of agricultural products such as fertilisers, pesticides, insecticides and herbicides. Such chemicals may be made up into a solution and sprayed over the necessary area using an irrigation system or a hose for example. Again, one problem with this arrangement is that it requires storage of large volumes of chemical containing solution. Furthermore, such chemicals can be difficult to handle when in liquid form.

In a further application, cleaning apparatus for cleaning cars and other vehicles may have accessories which enable a liquid detergent concentrate to be added to a stream of water to assist in the cleaning process. The detergent is added by flowing the water past an opening to a volume of the detergent through the opening and, which draws some of the detergent out into the water under a “venturi” effect.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a block for chemically dosing a stream of fluid flowing past the block, the block comprising at least one surface for the fluid to flow past to dissolve and/or erode the block, wherein the block is shaped to enable the at least one surface to be dissolved and/or eroded without a substantial change in the area of the at least one surface.

In an embodiment, the at least one surface is substantially flat.

In an embodiment, the at least one substantially flat surface of the block is of any suitable shape, such as rectangular, triangular, circular or hexagonal for example, however, preferably it is rectangular.

In another embodiment, the block comprises two substantially flat surfaces, parallel to one another.

In this embodiment, both substantially flat surfaces are for flowing the stream of fluid to flow past.

In an embodiment, the block comprises opposing side walls extending between the two substantially flat surfaces.

In an embodiment, the block comprises opposing end walls extending between the two substantially flat surfaces and between the opposing side walls.

In an embodiment, the block is of any suitable shape provided that as the at least one substantially flat surface dissolves/erodes, the effective surface area which is dissolving/eroding does not substantially change.

In an embodiment, the block is a rectangular prism.

In an embodiment, the surface(s) for the fluid to flow past is an outer surface(s) of the rectangular prism.

In another embodiment, the block is a hollow rectangular prism and the at least one surface for the fluid to flow past is the inner surfaces of the hollow rectangular prism.

The composition of the block is dependent on the application for which it is to be used.

In an embodiment, the block consists of one or more active ingredients and a solid carrier for carrying the one or more active ingredients.

In an embodiment, the active ingredients are evenly distributed throughout the solid carrier matrix.

Preferably, the solid carrier is soluble in water.

In an embodiment, a suitable solid carrier is polyethylene glycol. However, the solid carrier may be any other suitable substance for carrying the active ingredients.

In an embodiment, the polyethylene glycol has an average molecular weight of between 1000 and 8000 MW.

In an embodiment, the one or more active ingredients comprise at least one surfactant for a fire fighting application.

In an embodiment, the surfactants are for forming a fire retardant foam.

In an embodiment, the one or more active ingredients comprise a foam stabiliser.

In an embodiment, the one or more active ingredients comprise a corrosion inhibitor.

In another embodiment, the one or more active ingredients comprise at least one detergent for a cleaning application.

In yet another embodiment, one or more active ingredients comprise any one or more compounds selected from the group consisting of fertilisers, pesticides, insecticides and herbicides for an agricultural or a gardening application.

According to a second aspect of the present invention, there is provided an apparatus for housing a block for chemically dosing a stream of fluid flowing past the block, by dissolution and/or erosion of the block, the apparatus comprising a chamber for the block to reside in, the chamber having an inlet and an outlet to enable the stream of fluid to flow therethrough.

In an embodiment, the block is the block according to the first aspect of the present invention.

In an embodiment, the chamber is arranged to provide a substantially constant concentration of chemicals in the fluid at its outlet for a given flowrate when the block resides therein.

Preferably, the shape of the chamber is generally the same as the shape of the block.

In an embodiment, the chamber is rectangular in shape.

The chamber is preferably arranged to house the block whereby, in use, only the at least one surface of the block which does not substantially change in area as it dissolves and/or erodes is exposed to the flow of fluid.

In an embodiment where the block comprises two substantially flat surfaces, the chamber is shaped to enable the block to reside therein with its opposing side walls snugly abutting the side walls of the chamber.

Preferably, the chamber is shaped so that the opposing side walls of the block cannot dissolve and/or erode in use, when the block resides in the chamber.

In an embodiment, the chamber is arranged so that, in use, fluid entering and exiting the chamber does not significantly dissolve and/or erode the opposing end walls of the rectangular block.

In an embodiment, the chamber is shaped to enable the at least one surface of the block to be positioned approximately perpendicular to the side walls of the chamber when the block resides therein.

In this embodiment, the chamber is preferably shaped to provide a space next to the at least one surface of the block for the stream of fluid to flow through when the block resides therein.

In an embodiment where the block comprises two substantially flat surfaces, the chamber is shaped to provide spaces next to the respective surfaces of the block when it resides therein for the stream of fluid to flow through.

In this embodiment, the apparatus also comprise a regulating mechanism, which regulates flow of the fluid to enable flow to one or both of the spaces next to the surfaces respectively in order to vary the concentration of the chemicals in the dosed fluid exiting the apparatus.

By “next to” it is understood that the space(s) may be above, below or beside the at least one surface(s) of the block.

In an embodiment, the apparatus also comprises a retaining mechanism for holding the block in position in the chamber.

In an embodiment, the retaining mechanism comprises an opposing pair of ridges formed on the side walls of the chamber for engaging corresponding grooves formed in the opposing side walls of the block.

In another embodiment, the retaining mechanism comprises an opposing pair of grooves formed in the side walls of the chamber for receiving corresponding ridges formed on the opposing side walls of the block.

The apparatus also comprises an inlet and an outlet. In an embodiment, the inlet and the outlet of the chamber are fluidly connected to the inlet and the outlet of the apparatus respectively.

In an embodiment, the apparatus also comprises a bypass for allowing some or all of the fluid stream to bypass the chamber.

In an embodiment, the bypass is fluidly connected to the inlet and the outlet of the apparatus.

In an embodiment, the apparatus also comprises a baffle wall for separating the chamber from the bypass.

In an embodiment, the baffle wall forms one side of the chamber.

In an embodiment, the apparatus also comprises a bypass regulator for regulating the flow of fluid through the bypass.

In an embodiment, any fluid flowing through the bypass is used to dilute the fluid from the outlet of the chamber which has been chemically dosed by the block.

In an embodiment, the apparatus also comprises a mixing well, located prior to the outlet of the apparatus for mixing fluid from the bypass and the chemically dosed fluid from the outlet of the chamber.

The bypass regulator may be any suitable mechanism, but preferably is a two-way valve.

The bypass regulator may be infinitely or discretely variable from zero flow through the bypass to 100% flow through the bypass.

In an embodiment, the apparatus also comprises a removable end cap for access to the chamber.

The removable end cap may be readily removed to enable the block to be inserted or removed and a new block inserted.

In an embodiment, the apparatus also comprises a non-return valve located in the outlet of the chamber.

Preferably, the non-return valve prevents any flow of fluid from the bypass into the chamber through the chamber's outlet.

The apparatus may be hand held or mounted to a skid, or fixed permanently to a truck (or other vehicle) or the ground.

In an embodiment, the apparatus is manufactured from any suitable plastic or metallic material or a combination thereof.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring firstly toFIGS. 1 and 2, an apparatus10for housing a block11for chemically dosing a stream of fluid according to an embodiment of the present invention is shown. The stream of fluid flows past the block11(by flowing through the apparatus10), the block11chemically dosing the stream of fluid by dissolving and/or eroding into the fluid.

The block11comprises at least one surface30for the fluid to flow past to dissolve and/or erode the block11, wherein the block11is shaped to enable the at least one surface30to be dissolved and/or eroded without a substantial change in the area of the at least one surface30. Because the surface area of the block11which dissolves and/or erodes does not change, this enables the block11to provide a constant rate of chemical dosing to the fluid for a given flowrate of the fluid past the surface30of the block11for a substantial portion of the working life of the block11.

The at least one surface30of the block11shown inFIGS. 1 and 2comprises two substantially flat surfaces, parallel to one another, in which case the block11, in use, may be arranged to enable the stream of fluid to flow over both substantially flat surfaces. The block11also comprises opposing side walls31extending between the two substantially flat surfaces30.

However, it is to be understood that the block11may have only one substantially flat surface for flowing the fluid over.

The substantially flat surface(s)30enable the block11to provide a constant rate of chemical dosing to the fluid for a given flowrate because as the block11dissolves and/or erodes, the effective surface area of the block11which is dissolving/eroding does not substantially change. The flat surface(s)30of the block11may be of any suitable shape, such as rectangular, triangular, circular or hexagonal for example, however, preferably it is rectangular.

The block11itself may be of any suitable shape provided that as the at least one surface dissolves/erodes, the effective surface area which is dissolving/eroding is not substantially reduced. Although the block11may be of any suitable shape, preferably it is a rectangular prism.

The composition of the block11is dependent on the application for which it is to be used. The block11may consist of surfactants for fire fighting applications, detergents for cleaning applications or fertilisers, pesticides, insecticides or herbicides for agricultural or gardening applications or any other one or more active ingredients as desired.

In any of these applications, the block11also consists of a solid carrier for carrying the one or more active ingredients of the block11, which in the case of the fire fighting application is the surfactant(s). The surfactant(s) or other active ingredients are evenly distributed throughout the solid carrier matrix. A suitable solid carrier is polyethylene glycol having an average molecular weight of between 1000 and 8000 MW. However, any other suitable substance may be employed as the solid carrier, which is preferably water soluble.

The one or more active ingredients may also comprise a foam stabiliser(s) and may also comprise a corrosion inhibitor(s). The stream of fluid is dosed with the surfactant(s) and any other chemicals present in the block11, as the block11, including the solid carrier, dissolves and/or erodes into the fluid flowing over the surfaces30of the block11.

The apparatus10comprises a chamber12for the block11to reside in. The chamber12has an inlet13and an outlet14to enable the stream of fluid to flow through the chamber12. The chamber12houses the block11such that, in use, only the surfaces30of the block11which do not substantially change in area as they dissolve and/or erode are exposed to the flow of fluid.

The chamber12is shaped so that the block11resides therein with its opposing side walls31snugly abutting the side walls of the chamber12. Thus, the substantially flat surfaces30of the block11are approximately perpendicular to the side walls of the chamber12. The snug abutment of the opposing side walls31of the block11against the side walls of the chamber12prevent the opposing side walls31from being eroded and/or dissolved because fluid cannot flow past the opposing side walls31. If this were to occur then it could cause a reduction in the surface area of the substantially flat surfaces30of the block11, which in turn would reduce the rate of dosing by the block11.

The chamber12is also shaped to provide a space next to the substantially flat surfaces30of the block11for the stream of fluid to flow through and past the surfaces30when the block11resides therein. In order to hold the block11in position in the chamber13so that the space next to the each of the substantially flat surfaces30are maintained, the apparatus10is also provided with a suitable retaining mechanism. In one embodiment (not shown), the retaining mechanism comprises an opposing pair of ridges formed on the side walls of the chamber12. The opposing pair of ridges are shaped to engage corresponding grooves formed in the opposing side walls31of the block11. In a variation (also not shown), the retaining mechanism comprises an opposing pair of grooves formed in the side walls of the chamber12which are shaped for receiving corresponding ridges formed on the opposing side walls31of the block11.

The chamber12is preferably arranged to provide a substantially constant concentration of chemicals in the fluid at its outlet14for a given flowrate when the block11resides therein. However, in a variation, the apparatus10may also comprise a regulating mechanism, which regulates flow of the fluid to enable flow to one or both of the spaces next to the surfaces30respectively in order to vary the concentration of the chemicals in the dosed fluid exiting the apparatus10.

The chamber12is also arranged so that fluid entering and exiting the chamber12does not significantly dissolve and/or erode the opposing end walls32of the rectangular block11. The end walls32extend between the substantially flat surfaces30and between the opposing side walls31. As with the opposing side walls31, it is highly desirable to substantially prevent dissolution and/or erosion of the end walls32so as to avoid causing any significant reduction in the surface area of the substantially flat surfaces30.

The apparatus10also comprises an inlet15and an outlet16. The inlet13and the outlet14of the chamber are fluidly connected to the inlet15and the outlet16of the apparatus10respectively. The outlet16of the apparatus10may be fluidly connected to a hose, sprinkler or other suitable delivery mechanism. The apparatus10also comprises a bypass17for allowing some or all of the fluid stream to bypass the chamber12. The bypass17is fluidly connected to the inlet15and the outlet16of the apparatus10.

The apparatus10also comprises a baffle wall18. The baffle wall18separates the chamber12from the bypass17. In the embodiment shown in the figures, the baffle wall18forms one side of the chamber12.

The apparatus10also comprises a bypass regulator19for regulating the flow of fluid through the bypass17. This enables an operator to vary the concentration of the chemicals in the dosed fluid exiting the apparatus10. Any fluid flowing through the bypass17is used to “dilute” the fluid from the outlet14of the chamber12which has been chemically dosed by the block11. The apparatus10also comprises a mixing well20, located prior to the outlet16of the apparatus10, in which fluid from the bypass17and chemically dosed fluid from the outlet14of the chamber12are mixed prior to exiting the apparatus10.

The bypass regulator19may be any suitable mechanism, but preferably is a two-way valve. The bypass regulator19may be infinitely or discretely variable from zero flow through the bypass17(as inFIG. 1) to 100% flow through the bypass17(as inFIG. 2). This is particularly advantageous for fire fighting applications as it enables a fire fighter to readily switch between spraying foam and water only from the same hose without having to disconnect the apparatus from the hose. Control of the bypass regulator19is thus preferably provided in a hand held device, which may be the apparatus10itself or may be device, remote from the apparatus10.

The apparatus10also comprises a removable end cap21for ready access to the chamber12. The removable end cap21may be readily removed to enable the block11to be inserted or removed and a new block inserted.

Although not shown in the Figures, the apparatus10may also comprise a non-return or one-way valve located in the outlet14of the chamber12. The non-return valve prevents any flow of fluid from the bypass17into the chamber12through the chamber's outlet14. Fluid may only through the non-return valve in the chamber's outlet14to exit the chamber12. Advantageously, this enables continuous flow of fluid through the apparatus10whilst replacing the block11in the chamber12with a new block. With the bypass regulator19closing off the inlet13to the chamber12, fluid flows solely through the bypass17and cannot “backflow” into the chamber12through the chamber's outlet14because of the non-return valve therein. Whilst this is occurring, the end cap21may be removed and the new block inserted. This is particularly important in fire-fighting applications of the apparatus10, where it would be highly undesirable to have to stop the flow of water through the apparatus10(and onto a fire) in order to replace the block11.

The apparatus10may be hand held or mounted to a skid, or fixed permanently to a truck (or other vehicle) or the ground. The apparatus10may be manufactured from any suitable plastic or metallic material or a combination thereof.

Referring now toFIGS. 3 and 4, an apparatus110for housing a block ill for chemically dosing a stream of fluid according to another embodiment of the present invention is shown. The apparatus110is similar to the apparatus10shown and described in relation toFIGS. 1 and 2. Similar features of the apparatus110have been given the same reference number, but have been prefixed with the numeral1.

For the apparatus110ofFIGS. 3 and 4, the bypass regulator119is located approximate to the inlet113of the chamber112as opposed to the apparatus10ofFIGS. 1 and 2, in which the bypass regulator19is located approximate to the outlet14of the chamber12.

In a variation to that shown inFIGS. 1 to 4, the bypass regulator may comprise two two-way valves, located at either end of the bypass17, one to a valve being located approximate to the inlet and outlet of the chamber, respectively.

EXAMPLE

A comparative trial was conducted to compare the performance of a conventional block for chemically dosing a stream of fluid against a block according to an embodiment of the present invention. The conventional block was cylindrical in shape. The block according to an embodiment of the present invention was rectangular in shape, having two substantial flat surfaces, substantially parallel to one another. The rectangular block was used to dose a stream of water in an apparatus whereby the water flowed past only the two substantially flat surfaces. The cylindrical block was used to dose a stream of water using a conventional apparatus, whereby the water flowed past the cylindrical surface of the block.

Graphs 5 and 6 show the relative concentration of the active agent in the water after flowing past the conventional cylindrical block and the rectangular block respectively, against the volume of water treated. As can be seen in Graph 5, for the conventional block, the concentration of the active agent in the water decreases in an inverse square relationship.

However, for the rectangular block, Graph 6 shows that the concentration of the active agent in the water is substantially constant throughout its usable treatment life. The concentration of active agent in the water drops rapidly to zero at the end of the treatment life, indicating that the majority of the rectangular block has been dissolved and/or eroded prior to it becoming unusable to satisfactorily dose the water.