JPH01207535A - Vacuum air lift mud pumping device - Google Patents

Abstract

PURPOSE:To improve the mud pumping efficiency by communicating the upper end of a mud pumping pipe provided with a suction nozzle at the lower section to a separate tank, decompressing it with a decompressing pump, and providing a mud discharging means to discharge mud under the atmospheric pressure. CONSTITUTION:A mud pumping pipe 12 is drooped to the water bottom from a service platform ship 11, a nozzle 13 is communicated to a compressor 16. The upper end of the mud pumping pipe 12 is communicated and opened to a separate tank 17, a vacuum pump 19 is communicated to the tank 17 via a suction pipe 18, an underwater sand pump 20 is provided in the tank 17. When the compressor 16 and the vacuum pump 19 are simultaneously operated, mud is made gas-solid-liquid three-phase slurry by the pressure difference and lifted through the mud pumping pipe 12 and fed into the tank 17, the separated air is discharged by the vacuum pump 19 and mud water is discharged by the sand pump 20 respectively. The mud pumping to the suction limit or more of the vacuum pump 19 can be thereby performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a vacuum air lift mud lifting device that lifts and discharges earth and sand on the bottom of water by a combined effect of vacuum and air lift.

(Prior art) Generally, in suction type dredging and mud pumping work, when the actual pumping head is high, mud is pumped when dredging in large water depth areas, mud is pumped with high concentration, mud is pumped with soil that has a high sedimentation rate, etc. In this case, there is a limit to the operation due to the suction limit of the bong 1 used, that is, the limit determined by the relationship between atmospheric pressure and gravity.

As a method to overcome this limitation, as shown in Fig. 5 (a), there is a method of pumping mud through a water flow hose 2 using a submersible sand pump 1, or a method of pumping mud through a water flow hose 2 as shown in Fig. 5 (b), There is a method in which air is supplied from a compressor 4 through an air supply pipe 5 to the lower end of the mud pipe 3 and the mud is lifted by an air lift, and a sand pump 7 is installed at the upper end of the mud pipe 6 as shown in FIG. Connect, attach the ejector 8 to the lower end,
A conceivable solution is one in which the driving water pump 9 injects water from the ejector 8 into the mud pumping pipe 6 to assist suction.

(The problem that the invention aims to solve!! M) However, with the method of using a submersible sand pump, maintenance such as blockage in the impeller is difficult, and it is necessary to have a water pressure resistant structure at great depths, which is expensive. Also, since the air lift method uses the difference in specific gravity between the inside and outside of the lower end of the slurry pumping pipe, it is not suitable for pumping high concentrations or large volumes of mud. Furthermore, the method assisted by an ejector requires a large-capacity pump for driving water, and has the problem of diluting the mud more than necessary.

The present invention aims to solve such conventional problems and provide a mud lifting device with high mud lifting capacity at low cost.

(Means for Solving the Problems) The gist of the present invention for solving the above-mentioned conventional problems and achieving the intended purpose is to provide a cylindrical mud pumping pipe, and the mud pumping pipe. An air supply nozzle that supplies air for airlift into the mud lifting pipe, a compressor that supplies air to the air supply nozzle, and an upper end of the mud lifting pipe are communicated with each other, so that the mud is lifted from the mud lifting pipe. a separate tank for separating solid liquid and air; a pressure reducing pump for forcibly discharging the air in the separate tank to reduce the pressure in the tank; and a mud discharge means for discharging the mud in the separate tank to atmospheric pressure. A vacuum air lift mud lifting device is provided.

(Function) In this device, air compressed by a compressor is injected into the mud pumping pipe from the air supply nozzle. At the bottom opening of the mud lifting pipe, mud is forced into the pipe due to the pressure difference inside and outside the mud lifting pipe, mixes with the air injected from the air supply nozzle, and becomes a gas-solid-liquid three-phase slurry containing a mixture of gas, solid, and liquid. Become. Negative pressure from a vacuum pump is applied to the gas-solid-liquid three-phase slurry from the top of the mud pumping pipe, and the combined effect of air lift and negative pressure lifts the slurry and sends it into a separate tank. Air and muddy water are separated in a separate tank, and the air is sucked into a vacuum pump. Further, since negative pressure is applied inside the separate tank, the muddy water is discharged to atmospheric pressure by a muddy water discharge means such as a submersible sand pump installed in the tank.

(Example) Next, an example of implementation of the present invention will be described with reference to FIGS. 1 to 4.

In the figure, numeral 11 is a work barge, and 12 is a mud pumping pipe that hangs down from the work barge 11 to the bottom of the water. The mud pumping pipe 12 is provided with an air supply nozzle 13 slightly above its lower end. As shown in FIG. 2, the air supply nozzles 13 are opened at regular intervals in the circumferential direction of the slurry pumping pipe 12, with their tips directed upward toward the center. The base end of the air supply nozzle 13 is connected to a ring-shaped manifold 14.
The manifold 14 is connected to the manifold 14 and the tip of the air supply pipe 15 is connected to the manifold 14. The air supply pipe 15 is placed above the work barge 11! The compressor 1
Compressed air is sent from 6 to an air supply pipe 15 through a manifold 14, and is ejected into the mud lifting pipe 12.

The upper end of the mud pumping pipe 12 is opened to communicate with the upper part of a separate tank 17 installed on the work barge 11. The top of the separate tank 17 is connected to one end of a suction pipe 18 . Fl of suction tube 18! ! The end is connected to a vacuum pump 19, and the inside of the separate tank 17 is reduced in pressure by the vacuum pump 19 through this suction pipe 18.

A submersible sand pump 20 is installed at the bottom of the separate tank 17 as a mud discharge means, and a sand discharge pipe 21 leading to the submersible sand pump 20 is led out of the separate tank 17, thereby forcibly discharging the mud in the separate tank 17. I'm trying to make it happen.

Next, the operation of the mud pumping device configured as described above will be explained.

First, the compressor 16 and the vacuum pump 19 are operated simultaneously with the lower end of the mud pumping pipe 12 facing into the mud at the bottom of the water. The air compressed by the compressor 16 is sent from the manifold 14 to the air supply nozzle 13 through the air supply pipe 15 and is injected into the mud lifting pipe 12. At the same time, vacuum pump 1
9, the pressure inside the separate tank 17 is reduced. As a result, the pressure at the lower end opening 12a of the mud pumping pipe 12 is reduced by the air lift effect caused by the air injection from the air supply nozzle 13 and the suction by the vacuum pump 19, and the mud is pushed into the mud pumping pipe 12 due to the pressure difference inside and outside the pipe. , gas, solid,
The liquid becomes a gas-solid-liquid three-phase slurry, which is pumped into the mud pumping pipe 1.
Separate tank 17 on the work barge 11
sent inside.

Inside the separate tank 17, air and muddy water are separated by a difference in specific gravity, and the air is forcibly discharged from the separate tank 17 by a vacuum pump 19 and the muddy water by a submersible sand pump 20.

The basic formula for vacuum airlift Fukudo is, from the equilibrium of pressure at the position of the air supply nozzle 13 of the work barge 11, γ ・D−H−
γ ・(D+H) 10h fW
v m・・・・・・・・・(1) γ: Liquid ratio type outside the tube γ: Apparent inside the tube is specific gravity (gas solid liquid) H: Vacuum pump negative pressure (negative value) (m)■ D: Supply Nozzle position water depth (m) H: Actual lifting head
(m) hf: Pipe friction loss head
(m), the left side of the equation is the driving energy, and the right side is the consumed energy.

At this time, hf, that is, [γi・D−Hv−γ□・(D
The larger the 'r-H) is, the more mud can be pumped with Dasui Jl (?L Endai).

In the case of a normal air lift, Hv-〇 is obtained in equation (1), so γ ・D=γ ・<D0H) 10h f・・・・・・(
2) W In From this equation, it is clear that the vacuum air lift has greater driving energy and is capable of lifting a large amount of mud.

In addition, the necessary conditions for lifting mud with an air lift are:
Therefore, from equation (2), γ□・(1)+H)<γ・D Therefore, γ<[D/ (D+H)]・γ.

m
W This means that in a normal airlift, the depth of the supply air nozzle position must be sufficiently large compared to the actual lifting height H, and γ must be less than γ.
W, so it is necessary to pump a large amount of air when pumping mud. On the other hand, vacuum airlift has a margin of -H, so D does not need to be so large, and even if γ is more than γ, it is possible to lift m
W Yes.

In addition, in the case of suction pumping (including turbine pumps of ordinary pumping ships), the suction lift is limited by the suction capacity of the pump, and does not exceed -760I1mh (-1011IAQ).For example, the specific gravity of the ground γ , = 1.7, was pumped with a vacuum pump without dilution (apparently the volumetric gold mud ratio was 10).
0%), vacuum limit Hv=-9,2m (70
01111H (1) Actual head H=Om, γ =1.0
Then, γ = γ, = 0.7 From basic formula (1), 1
．． 0xD-(-9,2)=1.7xD+hfSince hf>O at the start of mud pumping, 9.2-0.7xD=hf>O D<13.1m Therefore, under the above conditions, It is impossible to pump mud at a depth of 13.1 m or more. In addition, since the suction limit of a turbine pump is small, the limit water depth for pumping mud is even smaller.

Under the above conditions, 1/1 of the volume of mud is removed by vacuum air lift.
When air of 2 is blown out, the apparent inside of the pipe is specific gravity γ = 1.7/ (1 + 0. 5) = 1. 13 As above, from equation (1), 1, OxD9.2=1.13xD+hf9.2-0.
13xD>O D<70.8m Under the above conditions, the vacuum airlift lift limit is 70.8m
It can be seen that the value increases significantly as m.

Tables 1 and 2 show the results of a comparison experiment of pumping water using fresh water using the vacuum air lift of the present invention and using a conventional air lift and vacuum pump.

Table 1 Table 2 In addition to the above-mentioned means for discharging muddy water from the separate tank 17, as shown in FIG. By setting the liquid level height in the separate tank 17 so that the solid-liquid column pressure (m)≧1 vacuum pump negative pressure l (m), the solid-liquid has a pressure higher than atmospheric pressure at the discharge port. It can be discharged without backflow.

In addition, when lifting mud at a height of 1 degree, as shown in Fig. 4, a mud collecting cover 24 is attached to the lower end of the mud lifting pipe 12 via a visible pipe 23, and this is lowered down to the mud surface at the bottom of the water using a winch 25. Reduce suction and lift mud.

(Effect of the invention) The vacuum air lift mud lifting device of the present invention configured as described above has the following features:
It has the following effects.

■ It is possible to pump more mud than the suction limit of the pump, and it is possible to pump mud at deep water depths, pump mud at high concentrations, and pump mud at high lifting heights more efficiently than with conventional methods.

■ Since there are no mechanical parts such as impellers in the flow line, there are fewer failures and there is no risk of blockage due to obstacles, allowing objects as large as the pipe cross-sectional area to pass through.

■ When handling objects to be lifted that have a large sedimentation rate due to their large particle size or specific gravity, it is possible to increase the head loss, thereby increasing the flow velocity in the pipe and increasing work efficiency.

■ Maintenance is easy because all mechanical parts are above water.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view schematically showing the entire embodiment of the device of the present invention, Fig. 2 is an enlarged cross-sectional view of the air supply nozzle portion, and Fig. 3 is a longitudinal cross-sectional view schematically showing another example of the mud discharge means. Figures 4 and 4 are side views schematically showing an example of a case in which high-concentration mud pumping is performed, and Figs. 5 (a) to (c) are side views schematically showing conventional mud pumping devices, respectively. 11...Work barge, 12...Sludge lifting pipe,
13... Air supply nozzle, 15... Air supply pipe, 16... Compressor, 17... Separate tank, 18... Suction pipe, 19...
... Vacuum pump, 20 ... Submersible sand pump, 21 ... Sand discharge pipe.

Claims (1)

[Claims] a cylindrical mud lifting pipe; an air supply nozzle provided at the bottom of the mud lifting pipe for supplying air for air lift into the mud lifting pipe;
a compressor that supplies air to the air supply nozzle; a separate tank that communicates with the upper end of the mud lift pipe and separates air from the solid liquid lifted from the mud lift pipe; and a forced discharge of the air in the separate tank. A vacuum air lift mud pumping device comprising: a pressure reducing pump for reducing the pressure inside the tank; and mud discharge means for discharging the mud in the separate tank to atmospheric pressure.