JPH044474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a free piston pump for slurry.

BACKGROUND ART FIG. 4 shows a schematic configuration of a conventional free piston pump for slurry. In the figure, A, B, and C are the first to third vertical cylinders, and 1, 2, and 3 are free pistons that are disposed in each cylinder A, B, and C so as to be able to rise and fall freely, and they are mutually connected to each other. It is set to move up and down at different timings by /3 cycles.

Numeral 4 is a sealing material that is fitted into grooves on the outer peripheral surface of each free piston 1, 2, and 3 and abuts on the inner peripheral surfaces of cylinders A, B, and C. Numeral 5 is a slurry tank in which, for example, coal slurry is placed. 6 is a slurry supply pipe whose one end is connected to the lower end of the slurry tank 5, and each branch part 6a at the other end is connected to the lower part of the cylinders A, B, and C, respectively;
7 is a slurry pump interposed in the middle of the slurry supply pipe 6, 8 is a fresh water tank, 9 is connected at one end to the lower part of the fresh water tank 8, and each branch part 9a at the other end is connected to cylinders A, B, B, A fresh water supply pipe connected to the upper end of C; 10, 11, and 12 a fresh water high-pressure pump flowmeter and a flow control valve interposed in the middle of the fresh water supply pipe 9; 13 a branch part 1 at one end;
3a is a fresh water discharge pipe connected to the upper end of each cylinder A, B, C, and the other end is inserted into the fresh water tank 8; 14, each branch part 14a at one end is connected to the lower end of each cylinder A, B, C; It is a slurry transport pipe that is connected and the other end is extended to a predetermined location. A-SI, B-SI, C-SI are slurry supply pipes 6
A valve, A-WI, installed in each branch part 6a of
B-WI, C-WI are each branch part 9a of the fresh water supply pipe 9
Valves installed in A-SO, B-SO, C-
SO is a valve installed in each branch 13a of the fresh water discharge pipe 13, and A-SO, B-SO, and C-SO are valves installed in each branch 14a of the slurry transport pipe 14.

LS-H is a limit switch that detects the upper limit position of the piston of each cylinder A, B, C, LS-L
LS-M is a limit switch that detects the piston lower limit position of each cylinder A, B, and C, and LS-M is a limit switch that detects a position near the piston lower limit (intermediate position) of each cylinder A, B, and C. It is attached to the side walls of B and C. In addition, 15 is a slurry supply pipe 6
The slurry return pipe is connected in the middle, and SR is the valve inserted in the middle.

With such a configuration, operations were performed as follows, for example. First, the first cylinder A
The limit switch LS-L detects that the piston 1 has been lowered and reached the lower limit position, and the valve A-
SO, A-WI are closed. Next, valve A-WO
After opening the valve A-SI, the slurry is supplied through the slurry supply pipe 6. This causes the piston 1 to rise. next,
Limit switch LS-H detects that piston 1 has reached the upper limit position, and valves A-SI and A-WO are activated.
is closed. Next, open valve A-SO, then open valve A-WI, and open fresh water supply pipe 9.
Fresh water is supplied through. As a result, the piston 1 descends and the slurry is pumped out. Therefore, the limit switch LS-M detects that the piston 1 has reached the lower limit position, and the valve B-SO of the second cylinder B is opened. From then on,
Repeat the same operation for each cylinder A, B, and C. This allows the slurry to be continuously pumped.

Problems to be Solved by the Invention Incidentally, in the above configuration and operation, the reason why the piston 2 of the second cylinder B starts descending when the piston 1 reaches a position near the lower limit is that the reason why the piston 2 of the second cylinder B starts descending is that the pressure stroke is switched. This is to prevent flow rate fluctuations and pressure fluctuations from occurring.
However, if the slurry to be pumped contains air, an air layer is formed below the piston 1, so even the above method is effective in preventing flow rate fluctuations and pressure fluctuations at the time of switching the pumping stroke. There was a problem that could not be prevented.
The reason why air is included in the slurry is as follows.
This is because it is difficult to completely remove air when dry coal is turned into slurry, and air is sucked into the slurry liquid from the shaft seal of the slurry pump 7.

To explain the situation during this time in more detail based on FIG. 5, it is assumed that slurry is supplied to the second cylinder B, the piston 2 stops at the upper limit position, and enters a standby state for the pumping stroke. and valves B-SI, B- related to the second cylinder B;
When SO, B-WI, and B-WO are all temporarily closed, the pressure in the air layer 20 below the piston 2 is at a low pressure close to the discharge pressure of the slurry pump 7. Next, when the pumping stroke of the first cylinder A approaches the end and reaches the limit switch LS-M position, the second cylinder B receives this signal and prepares to start pumping. That is, at this time, the valve B-SO of the second cylinder B is opened, and the first cylinder A and the second cylinder B are brought into conduction. However, in this case, the pressure is high because the first cylinder A is being pumped, and a part of the slurry flowing through the slurry transport pipe 14 flows back into the second cylinder B, causing the air layer 20 in the second cylinder B to be compressed. will be done. Therefore, in the slurry transport pipe 14, the flow velocity decreases by the amount of the reverse flow from the first cylinder A to the second cylinder B, or in some cases, the flow rate stops.

It is an object of the present invention to solve these problems and provide a method for pumping slurry in a free piston pump that can prevent flow rate fluctuations and pressure fluctuations.

Means for Solving the Problems In order to solve the above problems, the free piston pump for slurry of the present invention includes a plurality of cylinders each having a free piston inside and a sealing material around the free piston. A driving water supply pipe and a driving water discharge pipe connected to one end; a slurry supply pipe and a slurry transport pipe connected to the other end of each cylinder; and the driving water supply pipe, driving water discharge pipe, and slurry supply pipe. and a valve interposed in the middle of the slurry transport pipe, a bypass pipe connected to the driving water supply pipe across the valve interposed in the driving water supply pipe, and a valve interposed in the middle of the bypass pipe. and before the discharge of the slurry supplied into the cylinder is completed, a pressure equalization valve interposed in a bypass pipe connected to the cylinder from which the slurry is to be discharged next. When the cylinder is opened, the pressure inside the cylinder from which the slurry is to be discharged is made equal to the pressure of the driving water.

In other words, with this configuration, the pressure equalizing valve is opened and high-pressure driving water is slowly introduced into the cylinder that is in standby for the pressure feeding stroke, compressing the air layer below the piston and equalizing the slurry pumping pressure. Keep it under pressure. This makes it possible to prevent flow velocity fluctuations and pressure fluctuations from occurring at the time of switching the pressure feeding stroke.

Embodiment Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a free piston pump for slurry according to the present invention. In the figure, parts having the same configuration as the conventional example are given the same numbers. In other words, as is particularly clear from the comparison with FIG.
A bypass pipe 16 spanning C-WI is connected to the fresh water supply pipe 9, and pressure equalizing valves 17, 18, and 19 are interposed in the middle of the bypass pipe 16. In this case, each valve A-WI, B-WI, C-
Since the WI is interposed in the branch part 9a of the fresh water supply pipe 9, one end of the bypass pipe 16 is connected to the main pipe side and the other end to the branch part 9a side.

Hereinafter, the effects of the above configuration will be explained. First, as shown in Fig. 1, the second cylinder B
The supply of slurry to valves B-SI and B is completed.
With -WO closed and valve B-SO closed, the pressure equalization valve 18 is opened and high-pressure fresh water is slowly introduced through the bypass pipe 16. and,
The air layer 20 below the piston 2 is compressed to equalize the pressure with the slurry pumping pressure. That is, the second
The pressure inside the cylinder B is made approximately equal to the discharge pressure (driving water pressure) of the high-pressure fresh water pump 10. Then, preparations are made to start pressure feeding, and valve B-SO is opened to bring the first and second cylinders A and B into conduction. This makes it possible to prevent flow rate fluctuations and pressure fluctuations from occurring.

In addition, in theory, the pressure equalizing valves 17, 18, 19
Existing valves A-WI, B-WI, C- without using
A similar effect can be obtained by adjusting WI, but valve A- used to supply high-pressure fresh water.
WI, B-WI, and C-WI have large diameters and are not easy to finely adjust. Therefore, in practice it is necessary to provide separate pressure equalizing valves 17, 18, 19 as in the present invention.

FIG. 2 shows the measurement results of flow rate fluctuations when the slurry free piston pumps of FIG. 5 (without pressure equalizing valve) and FIG. 1 (with pressure equalizing valve) are operated continuously. As is clear from the figure, pressure equalization valve 1
The free piston pump a for slurry without the pressure equalization valves 17, 18, and 19 shows a large flow rate fluctuation at the time of switching the pressure stroke.
Free piston pump b for slurry equipped with 9
The flow velocity of is always constant.

Figure 3 shows the recording results of the flow rate and pressure fluctuations of this free piston pump for slurry. As is clear from the figure, according to the present free piston pump for slurry, the pumping flow rate and the inlet pressure of the pumping pipe are always approximately constant.

Effects of the Invention According to the present invention, before the slurry is completely discharged from a predetermined cylinder, the pressure equalizing valve is opened to equalize the pressure in the cylinder to be discharged next with the drive water pressure. , the air layer formed below the piston in the cylinder is in a compressed state, making it possible to prevent flow velocity fluctuations and pressure fluctuations that occur at the switching point of the slurry pumping stroke, and to ensure stable slurry pumping. It can be carried out.

[Brief explanation of drawings]

Figures 1 to 3 are for explaining one embodiment of the present invention. Figure 1 is a schematic configuration diagram of a free piston pump for pumping slurry according to the present invention, and Figures 2 a and 2 are continuous pumps. FIG. 3 is a diagram showing flow velocity fluctuations during operation, FIG. 3 is a diagram showing flow velocity and pressure fluctuations during continuous pumping, and FIGS. 4 and 5 are schematic diagrams of a conventional free piston pump for pumping slurry. A...First cylinder, B...Second cylinder, C...Third cylinder, 1, 2, 3...Free piston, 6...Slurry supply pipe, 9...Fresh water supply pipe, 13...Fresh water discharge Pipe, 14... Slurry transport pipe, 16... Bypass pipe, 17, 18, 19
...Pressure equalization valve.

Claims (1)

[Claims] 1 A plurality of cylinders each having a free piston inside and a sealing material around the free piston, a driving water supply pipe and a driving water discharge pipe connected to one end of each cylinder, and a driving water supply pipe and a driving water discharge pipe connected to the other end of each cylinder. A connected slurry supply pipe and a slurry transport pipe, a valve interposed between the driving water supply pipe and the driving water discharge pipe, a slurry supply pipe and the slurry transport pipe, and a valve interposed in the driving water supply pipe. a bypass pipe connected to the driving water supply pipe across the valve, and a pressure equalizing valve interposed in the middle of the bypass pipe, and the slurry supplied into the cylinder is completely discharged. Before opening the pressure equalizing valve interposed in the bypass pipe connected to the cylinder from which the slurry is to be discharged next, so as to equalize the pressure in the cylinder from which the slurry is to be discharged next to the driving water pressure. A free piston pump for slurry, which is characterized by: