JPS5945406B2 - Sludge stirring method for containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stirring sludge in a container, and more specifically, to a method for stirring sludge in a container with high stirring efficiency.

When extracting sludge from sludge storage tanks or tanks that are part of nuclear power plants and other industrial plants, it is necessary to mix the sludge uniformly to make a slurry of uniform consistency due to transportation and post-processing issues. There is a need.

In addition, some sludge becomes highly dense, and in this case, periodic stirring is required. Conventionally, for this type of stirring, air, water circulation, an externally inserted stirrer, an immersion type submersible pump, etc. have been used. However, various problems arise when plants have radioactive sludge, such as nuclear power plants, and when tanks or storage tanks become larger. That is, in the case of air, the amount of vent gas to be processed increases. In the case of water circulation, problems arise such as increased size of valves and pumps and clogging of nozzles. With an externally inserted stirrer, when the tank becomes larger,
There are mechanical and maintenance concerns. In addition, even immersion type submersible pumps are difficult to maintain, and as the tank becomes larger, the pump becomes larger in capacity. As mentioned above, the conventional stirring and mixing method has various problems.

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to provide a stirring and mixing method and method for stirring sludge in a container with good stirring efficiency.

When stirring and mixing using a mobile submersible agitator such as a hanging type or a submersible pump, the sludge layer is first rolled up in a downward flow, stirred at a relatively lower part of the storage tank, and then the sludge layer is stirred in an upward flow. Switching, uniform mixing throughout the storage tank, and maintaining a uniform state. Since the stirring device can be placed outside the system when stirring is not required, maintenance is improved and there is no need to worry about conventional nozzle clogging or vent gas generation. Further, in the early stage of stirring, since a downward flow is used, supernatant water can be blown into the sludge layer and rolled up, and even if the sludge becomes dense, the densification can be sufficiently removed. Then, by switching to an upward flow, the sludge can be carried to the water surface and mixed throughout the storage tank. In this case, since the stirring is done relatively at the bottom in the early stage of stirring, it is very easy to mix the entire storage tank. If the storage tank becomes larger, stirring and mixing of the entire storage tank can be made more efficient by moving the device to several locations and performing the operation using an initial downward flow and then an upward flow for a set period of time. I can do well.

In the inventor's experiments, the sludge layer could not be sufficiently stirred up by upward flow alone, and when the tank became large, if only downward flow Could not stir. As in the present invention, by switching the water flow direction, it is possible to efficiently stir the combined tank. below,
A preferred embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, and 4.

FIG. 1 shows the structure of the stirring device 40. The stirring device 40 is
It consists of a submersible motor 5, an impeller 42 and a casing 41. An impeller 42 for stirring is directly connected to the submersible motor 5.

There is a casing 41 on the outside for water guiding, which also prevents rotation and
Guide rests 44 are attached at several locations. The casing 41 is attached to the submersible motor 5 by a support 45. The rotation direction of the underwater motor 5 can be easily changed using a changeover switch outside the system. A slurry containing radioactive sludge generated from a nuclear power generation blunt is supplied into the sludge storage tank 1 .

While the slurry is stored in the sludge storage tank 1, the sludge settles at the bottom of the sludge storage tank 1 to form a sludge layer 2, and above the sludge storage tank 1, supernatant water 3 exists. The submersible motor 5 of the stirring device 40 is suspended from a wire 6 and inserted into the sludge storage tank 1 . A guide 7 is installed inside the sludge storage tank 1. Since the rest stop 44 meshes with this guide 7, the stirring device 40 can freely move up and down along the guide 7. A stopper 8 is installed at the bottom of the guide 7, which is sufficiently safe against the stirring device 40 falling due to gravity. Further, this guide 7 is connected to a stirring device 40.
It is designed to withstand sufficient rotational torque. The initial state of stirring will be explained based on FIG. 2.

When the underwater motor 5 is driven, the impeller 42 rotates, and the supernatant water 3 flows as shown by the arrow 11. The supernatant water 3 sucked into the casing 41 flows downward and forms a sludge layer 2.
The sludge layer 2 is scraped off and the sludge is rolled up. When the sludge storage tank 1 is large and the height of the sludge layer 2 is high, stirring is performed at several positions within the sludge layer 2 for a certain period of time. After the sludge layer 2 is completely scraped off, the submersible motor 5 is reversed to reverse the rotation direction of the impeller 42.

FIG. 3 shows the state at that time. The supernatant water 3 containing sludge becomes an upward flow as shown by an arrow 12 and agitates the sludge in the sludge storage tank 1. This shows a state in which the sludge layer 2 that has flowed upward is uniformly mixed, stirred, or maintained. In this case, the upward flow 12 carries the sludge close to the water surface and prevents subsequent settling of the sludge. In this case as well, if the sludge storage tank 1 is large-sized, the sludge is stirred at several locations from the bottom to near the water surface for a certain period of time. By performing such stirring, the stirring efficiency is significantly improved. As in this embodiment, the stirring device 40 can be easily taken out of the sludge storage tank 1 when not stirring or when the device 40 is being maintained. there is no problem.

Further, since the stirring device can be freely moved in the vertical direction, even when the sludge storage tank 1 is large in size and has a large overall height, stirring can be performed with a relatively small power. Furthermore, by switching the flow direction, overall uniformity can be achieved efficiently. In the previous example, it was applied to the square sludge storage tank 1, but
It can also be applied to circular tanks. Furthermore, when the sludge storage tank 1 becomes large and the required power is large compared to the performance of the stirring device 40, several stirring devices 40 can be used as shown in FIGS. 5 and 6. In this case, the number of electric power units may be used at the same time, or one unit may be used by sequentially changing its position. Depending on the properties of the sludge layer 2, it is possible to maintain a uniform state with a relatively small amount of power once the sludge has risen, so even in a large sludge storage tank 1, it may be necessary to hold the sludge after it has been uniformized. A stand stirring device is sufficient. According to the present invention, the efficiency of stirring sludge in a container can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a stirring device used in a preferred embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of a preferred embodiment of the present invention, and FIG. 4 is a diagram of FIGS. A plan view of the sludge storage tank shown in FIG. 3, and FIGS. 5 and 6 are explanatory diagrams showing other embodiments of the present invention. 1... Sludge storage tank, 2... Sludge layer, 3... Supernatant water, 5... Submersible motor, 7... Guide, 11...downward flow,
12... Rising flow, 40... Stirring device,
41...Casing, 42...Impeller.

Claims (1)

[Claims] 1. A stirring device consisting of a rotating blade and a driving means to which the rotating blade is attached is inserted into a container in which liquid and sludge are present, and the rotating blade is driven to generate a downward flow of the liquid, A method for stirring sludge in a container, in which the sludge present at the bottom of the container is rolled up, and then the rotating blade is reversed to generate an upward flow of the liquid.