GB2253575A - Screw press feed system - Google Patents

Abstract

A submerged pump 2 pumps farm slurry from a pit 1 to a screw press 3 which separates solid and liquid fractions. The pump outlet is divided, so that only part of the slurry flows up line 6 to the press, while the rest is recycled directly back into the pit to effect mixing of the pit contents. A valve 8, comprising an annular bladder inflatable by a remote hand pump 11, controls the flow of the recycled fraction and thus indirectly controls the flow to the press. The press outlet has a counterweighted door 23. <IMAGE>

Description

Fluid flow control apparatus This invention relates to fluid flow control apparatus, particularly but not exclusively for controlling the flow of a fluid comprising a mixture of a liquid and said separable matter to a separator for separating the separable matter. A preferred application of the invention is for separating solid matter from the liquid of a farmyard slurry.

It is known to pump farmyard slurry to a separator from a reservoir or tank which is usually below ground level, the separator serving to separate out the solid matter from the liquid, which may either be returned to the slurry tank or passed to another tank for subsequent disposal. For all types of separator, it is important not to overload the separator, which typically can treat about 5 cubic metres of slurry per hour. To pump this slurry out of a below ground tank, it is necessary to provide a powerful pump to ensure an adequate supply of material to the separator under all circumstances. Typically, a head of 5-10 metres has to be pumped and there is the added problem that the consistency of the slurry varies considerably. Therefore, a large pump which is often too powerful under normal operating circumatances is used to ensure that the flow rate is always satisfactory.

One known solution to this problem is to provide an overflow for the fluid pumped to the separator via which in normal circumstances, most of the pumped slurry (typically 50-95%) is returned to the tank untreated. It is also necessary to provide additional stirring means to stir the slurry in the tank to mix it as thoroughly as possible prior to starting pumping to break down the solid matter to a pumpable form thereby to reduce the risk of blockages.

The present invention seeks to provide a practical, economic and efficient apparatus to alleviate the drawbacks of the existing systems.

According to a first aspect of the present invention there is provided fluid flow control apparatus for separating separable solid matter from a fluid comprising liquid containing said solid matter, including pump means at least part of which is submersible in said fluid and adapted to pump said fluid to separator means for separating said solid matter from the liquid, and valve means for determining the proportion of fluid pumped by the pump which is pumped to the separator, the remainder of the pumped fluid being recycled through the fluid in the tank thereby to mix the solid matter and the liquid.

Thus, the invention has the advantage that efficient pumping of fluid to the separator takes place without wastage while the slurry itself is adequately mixed prior to pumping to thereby facilitate efficient pumping.

According to a second aspect of the present invention there is provided fluid flow control apparatus for separating a slurry into more than one stream, including a flow divider having an inlet and two outlets, first one of the outlets comprising a reverse swept Tee, the second outlet incorporating a flow control valve to control the rate of fluid flow through the second outlet.

By this means, for a given rate of flow through the inlet, the rate of flow through the first outlet is controllable by limiting the rate of flow through the second outlet by operation of the control valve.

Preferably, the inlet and second outlet are co-axial. In a preferred embodiment of this aspect of the invention, the control valve comprises a diaphragm or bladder valve.

Preferably, the valve has a valve closure member in the form of a resilient section which forms a resilient wall of an annular chamber pressurisable to extend the resilient wall radially inwardly to reduce the size of the opening of the valve.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows a schematic sketch of the apparatus, and Figure 2 shows a side view of the pump arrangement in accordance with the second aspect of the invention.

Referring now to Figure 1, there is shown a schematic layout of a slurry pumping installation having a below ground slurry tank 1 from which slurry is pumped by a pump 2 to a separator 3 located above the tank 1. The slurry consists essentially of farmyard animal waste and includes, typically, waste water, mud, urine, excrement and vegetable matter such as straw and grass.

The separator 3 consists of an electrically driven screw compressor 21 to which the slurry is fed by the pump 2 via line 6. The screw 21 rotates in a cylinder 22 having a perforated wall through which liquid expressed from the slurry drains out through an outlet 27 into a separate tank (not shown) for subsequent disposal. At its end remote from the screw 21, the cylinder 22 is closed by a movable end wall 23 slidable on guides 24 against the bias of a counterbalance weight 25, the position of which is adjustable to control the amount of compression imparted to the slurry. The movable wall 23 is moved clear of the cylinder 22 by the slug of solid matter built up by the screw 21 to enable the solid matter to drop from the separator into a catch tank 26.

The output from the pump 2 passes to an automatic flow controller 4 which consists of a Tee shaped pipe layout 5 with two output pipes one of which comprises the line 6 and includes a reverse swept Tee branch 6a via which fluid- is pumped to the separator 3. An overflow pipe 13 leads from the separator back to the slurry tank 1. The other output pipe 7 leads to a flow control valve 8 which serves to control the amount of fluid passing through the pipe 7, diverting the remainder up the line 6 to the separator 3.

The valve 8 comprises a diaphragm or bladder valve containing a valve closure member 9 in the form of a resilient pipe section which is surrounded on its outside by an annular chamber 10 into which oil can be pumped by a handpump 11 located at ground level and connected to the chamber by flexible pipe 12. The pressure in the chamber 10 determines the opening size of the valve 8 and hence the amount of fluid which can pass therethrough for a given pump flow. The maximum pressure in the chamber 10 is limited by a pressure relief valve (not shown). In the event of the valve 8 becoming blocked with solid matter contained within the slurry, the blockage may be simply cleared by reducing the oil pressure in the chamber 10 and thus increasing the size of the opening 8 and thereby ejecting the trapped solids into the tank.

In operation, when a farmer wishes to separate the solid matter from a slurryr he first of all has the valve 8 fully open so that all of the fluid pumped by the pump 2 is circulated round the tank 1 to break up the solid matter and to mix the solid matter and liquid. Thereafter, the valve 8 is progressively closed until just sufficient flow is diverted to the branch 6 to allow the separator 3 to function efficiently with a minimum of slurry flowing back through the overflow pipe 13. The flow of the remainder of the pumped fluid through the valve 8 serves to keep the slurry adequately mixed prior to pumping. A pressure gauge shows the pressure in the chamber 10.

Preferably, the valve 8 and associated pipework 6 and 7 are integrally formed in one casting.

Although the embodiment described relates to the separation of the solid matter in farmyard slurry, the invention is not limited to this application. For example, the invention may be applied to the pumping of any fluid and the division of the fluid flow into two streams, the valve arrangement being operable to adjust the relative rates of flow between the two streams.

Claims (13)

1. Fluid flow control apparatus for separating separable solid matter from a fluid comprising liquid containing said solid matter, including pump means at least part of which is submersible in said fluid and adapted to pump said fluid to separator means for separating said solid matter from the liquid, and valve means for determining the proportion of fluid pumped by the pump which is pumped to the separator, the remainder of the pumped fluid being recycled through the fluid in the tank thereby to mix the solid matter and the liquid.

2. Fluid flow control apparatus for separating a slurry into more than one stream, including a flow divider having an inlet and two outlets, first one of the outlets comprising a reverse swept Tee, the second outlet incorporating a flow control valve to control the rate of fluid flow through the second outlet.

3. Fluid flow control apparatus according to claim 2 wherein the inlet and second outlet are co-axial.

4. Fluid flow control apparatus according to claim 2 or 3, wherein the control valve comprises a diaphragm or bladder valve.

5. Fluid flow control apparatus according to claim 4 wherein the valve has a valve closure member in the form of a resilient section which forms a resilient wall of an annular chamber pressurisable to extend the resilient wall radially inwardly to reduce the size of the opening of the valve.

6. Fluid flow control apparatus according to claim 5, including manually operable hydraulic means for pressurising said chamber.

7. Fluid flow control apparatus according to any one of claims 2 to 6 wherein the inlet and outlets and a housing of the control valve are formed in a one-piece casting.

8. Fluid flow control apparatus according to claim 1 in combination with any one of claims 2 to 7, wherein the separator comprises a screw compressor.

9. Fluid flow control apparatus according to claim 8, wherein the screw compressor has a cylindrical wall with one or more orifices through which liquid in the slurry is pressed out of the cylinder by the screw.

10. Fluid flow control apparatus according to claim 8 or 9, wherein the screw compressor has a movable end wall, biassed by resilient means to a closed position, solid matter compressed by the screw being effective to move the wall to an open position to enable the compressed solid matter to be released from the separator.

11. Fluid flow control apparatus according to claim 10, wherein the bias of the resilient means is adjustable to thereby adjust the amount of compression of the said solid matter.

12. Fluid flow control apparatus according to claim 11 wherein the bias is provided by a weight or weights.

13. Fluid flow control apparatus substantially as described herein, with reference to, and as illustrated in, the accompanying drawings.