Field of the Invention

The present invention relates to a method and apparatus for adding dry polymers directly to a fluid using in an inline flow system and relates particularly, though not exclusively, to such a method and apparatus for use in the mining industry for adding dry polymers to a drilling fluid or other operations where the addition of dry polymers is needed. Background to the Invention

Polymer additives are used in a variety of applications including wastewater treatment and underground mining. In drilling operations, dry polymers are added to drilling fluids, for example, as a dispersant, to improve cuttings carrying capacity, to counteract the sticking tendencies of day and reduce or eliminate bit balling, or more generally to control drilling fluid rheology.

In most conventional drilling operations, liquid or powdered polymers are mixed with the drilling fluid though a venturi type hopper and pumped into a mixing tank. An agitator in the mixing tank will keep the polymer moving, while the polymer is reaching its full yield, prior to the drilling fluid being pumped into the drilling string and down hole.

Drilling fluid mixing systems are generally not less than one cubic meter in volume and require some form of energy to allow for mixing of the polymers into the drilling fluid either through agitation or pumping, prior to being pumped down hole. This represents significant costs in plant infrastructure and maintenance, as well as energy consumption.

While it is common to find polymer blocks is various shapes and sizes the present invention relates to an apparatus for housing polymer blocks and a method of dosing polymer blocks using an inline flow system without the need for conventional mixing equipment. References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general knowledge in Australia or elsewhere.

Summary of the Invention According to one aspect of the present invention there is provided a dosing apparatus for housing polymer blocks in an inline flow system, the dosing apparatus comprising: an elongate vessel adapted to be connected in an inline flow system, the vessel comprising a cylindrical wall enclosed at each end to form a sealed flow path for liquid; a bottom end plate provided at a lower end of the cylindrical wall, the bottom end plate having a liquid exit port provided therein; and, a top end plate provided at an upper end of the cylindrical wall, the top end plate having a removable lid provided in connection therewith, the removable lid having a liquid entry port provided therein, whereby a polymer block may be inserted into the vessel by removing and replacing the lid, and wherein, in use, as liquid flows through the vessel, polymer from the polymer block is dispersed in the liquid at a controlled rate.

Advantageously the cylindrical wall of the vessel is made from a substantially transparent material wherein, in use, the rate at which the polymer is being dispersed in the liquid can be observed, and visual monitoring of the point at which the polymer block needs to be replaced is enabled.

Preferably the cylindrical wall is made from heavy walled clear acrylic pipe, sealed with an O-ring at each end between the top end plate and the bottom end plate respectively. Typically the top end plate and the bottom end plate are both of annular shape, and are in the form of stainless-steel plates. Preferably the top end plate and bottom end plate are joined to each other by a plurality of threaded connecting rods to compress the cylindrical wall between the end plates and form the sealed flow path for liquid in the vessel. Advantageously the connecting rods also make the vessel of the dosing apparatus mechanically rigid.

Advantageously the removable lid provided in connection with the top end plate is a cam-lock lid to permit rapid opening and closing of the vessel, whilst ensuring a sealed flow path for the liquid when it is in a closed condition.

According to another aspect of the present invention there is provided a method for dosing liquid with polymer in an inline flow system, the dosing method comprising: providing a dosing apparatus having an elongate vessel adapted to be connected in an inline flow system, the vessel comprising a cylindrical wall enclosed at each end to form a sealed flow path for liquid; providing a polymer block and inserting it into the vessel; connecting the vessel into an inline flow system; and, controlling the volume of liquid flowing through the vessel wherein, in use, as liquid flows through the vessel, polymer from the polymer block is dispersed in the liquid at a controlled rate. Typically the volume of liquid flowing through the vessel is controlled by bypassing some of the liquid around the dosing apparatus. By bypassing some of the liquid, the flow rate of liquid through the vessel and over the polymer block is reduced, which in turn decreases the rate at which the polymer block dissolves. Higher liquid flow rates will increase the rate at which the polymer block dissolves.

Advantageously providing the polymer block comprises selecting the composition of the polymer block to achieve a desired rate of dispersion of the polymer in the liquid as the block dissolves. Preferably the polymer block comprises a water-soluble wax polymer with a powdered polymer additive. Preferably the water-soluble wax polymer is Poly Ethelene Glycol (PEG). Preferably the PEG is heated to a liquid state, the powdered polymer additive is mixed into the liquid PEG, the liquid mixture is poured into a mould and allowed to cool to form a block.

Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word “preferably” or variations such as “preferred”, will be understood to imply that a stated integer or group of integers is desirable but not essential to the working of the invention. Brief Description of the Drawings

The nature of the invention will be better understood from the following detailed description of a specific embodiment of the method and apparatus for dosing a liquid with polymer, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a top perspective view of a first embodiment of a dosing apparatus for housing polymer blocks in an inline flow system according to the present invention;

Figure 2 is a side elevation of the dosing apparatus shown in Figure 1 ; Figure 3 is a cross-section view of the dosing apparatus of Figure 1 ; Figure 4 is an exploded view of the dosing apparatus of Figure 1 ; and,

Figure 5 is a schematic diagram illustrating the dosing apparatus of Figure 1 as used for dosing a liquid with a polymer in an inline flow system. Detailed Description of Preferred Embodiments

A preferred embodiment of a dosing apparatus 10 for housing polymer blocks 12 in an inline flow system in accordance with the invention, as illustrated in Figures 1 to 4, comprises an elongate vessel 14 adapted to be connected in an inline flow system 16 (see Figure 5). The vessel 14 comprises a cylindrical wall 18 enclosed at each end to form a sealed flow path for liquid. A bottom end plate 20 is provided at a lower end of the cylindrical wall 18, the bottom end plate 20 having a liquid exit port 22 of the vessel 14 provided therein.

A top end plate 24 is provided at an upper end of the cylindrical wall 18, the top end plate having a removable lid 26 provided in connection therewith. The removable lid 26 has a liquid entry port 28 of the vessel 14 provided therein. The top end plate 24 is also provided with a transverse liquid entry port 29, extending radially to one side of the vessel 14 (see Figures 2 and 3). One or more polymer blocks 12 may be inserted into the vessel 14 (see Figure 5) by removing and replacing the lid 26. A liquid inlet pipe of the inline flow system 16 is connected to the liquid entry port 28, and a liquid outlet pipe is connected to the liquid exit port 22 of the vessel 14 (see Figure 5). Alternatively, the liquid inlet pipe of the inline flow system 16 can be connected to the transverse liquid entry port 29, so that the lid 26 is kept free of hose connections, making it easier to remove and replace. In use, as liquid flows through the vessel 14, polymer from the polymer block 12 is dispersed into the liquid at a controlled rate as the polymer block 12 begins to dissolve.

Advantageously the liquid entry port 28 has a diffuser plate 52 inserted within a mouth of the liquid entry port, which acts to cause the liquid to spiral or swirl around the polymer block 12 as it flows through the vessel 14 (see Figures 1 , 3 and 4). The diffuser plate 52 is bifurcated in its lower half to form two members which are bent in opposite directions to create the spiral or swirling action in the fluid flow through the vessel 14. The spiral or swirling action helps to disperse the polymer in the liquid as it dissolves from the polymer block 12. Advantageously the cylindrical wall 18 of the vessel 14 is made from a substantially transparent material wherein, in use, the rate at which the polymer is being dispersed in the liquid can be observed, and to enable visual monitoring of the point at which the polymer block 12 needs to be replaced. In this embodiment the cylindrical wall 18 is made from heavy- walled clear acrylic pipe, sealed with a rubber O-ring 30 at each end between the top end plate 24 and the bottom end plate 20 respectively. In this embodiment the cylindrical wall 18 has an internal diameter of 142 mm and a minimum wall thickness of 10 mm.

Typically the top end plate 24 and the bottom end plate 20 are both of annular shape, and are in the form of stainless-steel plates. In the illustrated embodiment both end plates 20, 24 have an external diameter of 198 mm. Preferably both the top end plate 24 and the bottom end plate 20 are provided with an annular groove 32 therein, for receiving one of the O-rings 30 respectively. The grooves 32 also receive the respective ends of the cylindrical wall 18 therein.

Preferably the top end plate 24 and bottom end plate 20 are joined to each other by a plurality of threaded connecting rods 34. In the illustrated embodiment six connecting rods 34 are provided at regularly spaced angular intervals around the outside of the cylindrical wall 18. The connecting rods 34 compress the cylindrical wall 18 between the end plates 20, 24 to form the sealed flow path for liquid in the vessel 14. The connecting rods 34 screw directly into threaded apertures provided in the top plate 24, and pass through unthreaded apertures in the bottom end plate 20. Washers and nuts 36 are provided to fasten the connecting rods 34 to the bottom end plate 20. Advantageously the connecting rods 34 also make the vessel 14 of the dosing apparatus 10 mechanically rigid. In the assembled condition of the vessel 14 the spacing between the top end plate 24 and the bottom end plate 20 is 310 mm. The total height of the vessel 14, including the liquid entry port 22, is approximately 542 mm.

Advantageously the removable lid provided in connection with the top end plate 24 is a cam-lock lid 26 to permit rapid opening and closing of the vessel 14, whilst ensuring a sealed flow path for the liquid when it is in a closed condition. The lid 26 is received in a close fit within a mouth of a cam-lock sleeve 27, which is fixed to an annular lip 40 provided on the top end plate 26 (see Figure 3). The cam-lock sleeve 27 is connected to the annular lip 40 by a screw thread. Two cam-lock levers 38 are provided on diametrically opposite sides of the cam-lock sleeve 27, (see Figure 2) to facilitate rapid and secure closing and opening of the lid 26. The cam-lock levers 38 are shown in a locked position in Figures 1 and 2, in which the lid 26 is adapted to be tightly gripped and sealed within the mouth of the sleeve 27. When the levers 38 are lifted to an unlocked position, the lid 26 is released and can be removed from the mouth of the sleeve 27 to provide access to the interior of the vessel 14.

Preferably a filter plate 42 is also provided within the vessel 14. Preferably a plurality of perforations 44 are provided in a uniform pattern in the filter plate 42, the size of the perforations 44 being designed to prevent undissolved pieces of the polymer block 12 from passing through. The filter plate 42 in this embodiment is provided with four upstands 46, as can be seen most clearly in Figure 4, designed to maintain the filter plate 42 spaced a prescribed distance above the bottom end plate 20.

A preferred method for dosing liquid with polymer in an inline flow system will now be described with reference to Figures 1 to 5. The method comprises providing a dosing apparatus 10, as illustrated in Figures 1 to 4, having an elongate vessel 14 adapted to be connected in the inline flow system 16. The vessel 14 comprises a cylindrical wall 18 enclosed at each end to form a sealed flow path for liquid. The method further comprises providing a polymer block 12, inserting it into the vessel 14, and connecting the vessel 14 into the inline flow system 16, as shown in Figure 5.

The method further comprises controlling the volume of liquid flowing through the vessel 14 wherein, in use, as liquid flows through the vessel, polymer from the polymer block 12 is dispersed in the liquid at a controlled rate. Typically the volume of liquid flowing through the vessel 14 is controlled by bypassing some of the liquid around the dosing apparatus 10. A bypass flow valve 48 is provided for this purpose in the inline flow system 16 for regulating the bypass flow, and a control flow valve 50 is provided for controlling the flow of liquid through the dosing apparatus 10.

In Figure 5, the bypass valve 48 is shown in the fully closed position, and the flow control valve 50 is shown in the fully open position. By partially or fully opening the bypass valve 48, some of the liquid will bypass the dosing apparatus 10. By bypassing some of the liquid, the flow rate of liquid through the vessel 14 and over the polymer block is reduced, which in turn decreases the rate at which the polymer block 12 dissolves. Higher liquid flow rates will increase the rate at which the polymer block 12 dissolves.

Advantageously the step of providing the polymer block 12 comprises selecting the composition of the polymer block 12 to achieve a desired rate of dispersion of the polymer in the liquid, as the block 12 dissolves. Preferably the polymer block 12 comprises a water-soluble wax polymer with a powdered polymer additive. Preferably the water-soluble wax polymer is Poly Ethelene Glycol (PEG). Preferably the PEG is heated to a liquid state, the powdered polymer additive is mixed into the liquid PEG, and the liquid mixture is then poured into a mould and allowed to cool to form a block (not shown).

There are two ways to control the rate of dispersion of the polymer block:

(1) Different compositions of PEG and polymer can be used to control the dispersing time of the polymer block. (2) Controlling the volume of liquid flowing through the dosing apparatus and over the polymer block.

Now that a preferred embodiment of the method and apparatus for dosing a liquid with a polymer have been described in detail, it will be apparent that the described embodiment provides a number of advantages over the prior art, including the following:

(i) It is compact and simple in design, and can be installed in line with minimum disruption to the flow system.

(ii) It eliminates the need for a polymer mixing system, significantly reducing plant installation and maintenance costs.

(iii) It reduces energy consumption, as it requires no additional energy input to operate.

(iv) The polymer blocks are simple and inexpensive to manufacture.

(v) The rate of dispersion of the polymer in the liquid can be readily controlled by controlling the flow rate of liquid through the dosing apparatus and/ or modifying the composition of the polymer blocks.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing embodiments, in addition to those already described, without departing from the basic inventive concepts of the present invention. For example, the structure of the vessel in the dosing apparatus may vary considerably from that shown, so long as it forms a sealed flow path for the liquid. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described.