JP2003024977A - Operation method for aeration stirrer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method for an aeration stirrer enabling aerating operation without lowering the efficiency of an oxygen dissolving speed even if a water level lowers largely and enabling stirring operation even if the water level rises largely on the contrary. SOLUTION: Stirring blades 4 rotated in water and aerating blades 3 rotated above the surface of the water are formed to the shaft 2 rotated by an electromotor M and the cylindrical body 5 covering the aerating blades 3 is arranged in a state concentric to the shaft 2 from the vicinity of the stirring blades 14 and water introduced into the cylindrical body 5 by the stirring blades 4 is scattered to the periphery by the cylindrical body 5. In this operation method for the aeration stirrer, the rotary speed of the shaft 2 is made higher than that at the time of usual aerating operation until at least the cylindrical body 5 is filled with water from the start of aerating operation.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an aeration stirrer, and more particularly, to an aeration operation without lowering the oxygen dissolution rate efficiency even when the water level drops significantly. The present invention also relates to a method of operating an aeration stirrer that enables stirring operation even when the water level rises significantly. 2. Description of the Related Art Conventionally, when performing sewage treatment, an aeration device is provided near the surface of a rectangular water tank, a fountain is scattered around, and air is sent into the water by falling water to perform aeration. As such an aeration device, for example, a stirring blade rotating in water and an aeration blade rotating above the water surface are respectively formed on a vertical shaft rotated by an electric motor, and the periphery of the aeration blade is covered. There is an aeration stirrer in which a cylindrical body is disposed concentrically with a shaft from near a stirring blade, and water introduced into the cylindrical body by the stirring blade is scattered around by an aeration blade. This aeration stirrer
An aeration operation for dissolving oxygen in water (aerobic operation) and a stirring operation for dissolving oxygen in water (anaerobic operation) can be selectively performed by switching the rotation direction of the shaft between normal and reverse. [0003] In this aeration stirrer, during the stirring operation, the upper aeration blade idles or the lower portion of the aeration blade is not aerated even if it comes into contact with surface water. Also, during the aeration operation, the lower stirring blades in the water are reversely rotated to fill the cylinder disposed so as to protrude above the water surface, and the upper aeration blades provide the water. Water introduced into the cylinder is continuously scattered around. [0004] However, in the above-mentioned conventional aeration stirrer, when the water level in the water tank is greatly reduced,
Since the upper aeration blade rises relatively greatly with respect to the water surface, the filling height of the water introduced into the cylinder from the lower stirring blade is insufficient, and as a result, the water is agitated. The aeration operation cannot be performed without reaching the temperature. In addition, if the lower end of the upper aeration blade is provided at a position low enough to make contact with the water surface deep, the upper aeration blade may come into contact with surface water even during the stirring operation when the water level rises significantly. As a result, the water is unnecessarily agitated by the aeration blades, and there is a problem in that the water is scattered around, or air is mixed in, and the like. By the way, in the above-mentioned conventional aeration stirrer, in order to increase the oxygen dissolving rate efficiency, the outlet area and shape are determined so that the resistance of the outlet formed at the upper end of the cylindrical body is reduced. However, when the resistance of the outlet is small as described above, when the water level is lowered as described above and the aeration blade is far away from the water surface, the pressure in the vicinity of the aeration blade in the cylinder decreases, and a large amount of bubbles are generated. Therefore, the aeration operation cannot be started normally despite the filling of the water by the lower stirring blade. Conversely, when the resistance of the outlet is increased, the aeration start is good, but the power is consumed to flow the water against the resistance, so that there is a problem that the oxygen dissolution rate efficiency is reduced. . The present invention has been made in view of the above-mentioned problems of the conventional aeration stirrer, and enables the aeration operation without lowering the oxygen dissolving rate efficiency even when the water level is greatly reduced,
Another object of the present invention is to provide a method of operating an aeration stirrer that enables a stirring operation even when the water level rises significantly. [0007] In order to achieve the above object, an operation method of an aeration stirrer according to the present invention comprises a rotating shaft driven by an electric motor, a stirring blade rotating in water, and a rotating blade above the water surface. And a cylinder covering the periphery of the aeration blade is disposed concentrically with the shaft from near the stirring blade, and water introduced into the cylinder by the stirring blade is used for the aeration blade. In the method of operating an aeration stirrer that is scattered to the surroundings, the rotation speed of the shaft is set to be larger than at the time of the normal aeration operation during at least the time from the start of the aeration operation until the inside of the cylinder is filled with water. In this method of operating the aeration stirrer, the rotation speed of the shaft is set higher than usual when the aeration operation is started, and a large flow rate is generated in the cylinder by the stirring blade. At this time, since the outlet has a large resistance to the flow rate, it is possible to prevent the pressure in the cylinder from dropping, so that even when the water level drops, a good aeration operation without bubble generation is started. You. After the cylinder is filled with water and the aeration operation is started normally, even if the rotation speed is reduced to the normal operation, the suction of water into the cylinder is continuous even with the aeration blade alone. The normal aeration operation is continued without generating air bubbles. On the other hand, the flow rate of water is reduced by reducing the rotation speed after the start of the aeration operation, but the shape of the outlet is adapted to this reduced flow rate,
The aeration operation can be continued in a state where the resistance of the outlet is reduced and the oxygen dissolution rate efficiency is increased. In this case, if the operation is continued in a state where the rotation speed of the shaft is increased more than necessary, excessive aeration occurs and the water treatment is deteriorated. Since the aeration operation is performed, the oxygen dissolution rate efficiency becomes high overall. As described above, the operation method of the aeration stirrer of the present invention can reliably perform the aeration operation without lowering the oxygen dissolving rate efficiency even when the water level is greatly reduced, and the aeration ability is high due to the high aeration ability. Since the blades need not be installed unnecessarily low, the stirring operation can be reliably performed even when the water level rises significantly. An embodiment of the method for operating an aeration stirrer according to the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a method for operating an aeration stirrer according to the present invention. FIG. 1 shows a state in which an aeration stirrer is installed in an aeration tank for sewage treatment.
FIG. 1A shows a state during the stirring operation, respectively, in FIG. Although the aeration tank A is not particularly limited, it has a rectangular shape, and the aeration stirrer 1 is installed in the aeration tank A. The installation position of the aeration stirrer 1 with respect to the aeration tank A is a position where the aeration tank A having a rectangular shape is uniformly stirred and aerated, for example, as shown in FIG. In such a case, it is suspended from a stand (not shown) or floated on a float F. The aeration stirrer 1 is provided with a stirring blade 4 rotating in water and an aeration blade 3 rotating above the water surface on a vertical shaft 2 rotated by an electric motor M, respectively. Is arranged concentrically with the shaft 2 from the vicinity of the stirring blade 4 so that water introduced into the cylinder 5 by the stirring blade 4 is scattered around by the aeration blade 3. Has become. The aeration stirrer 1 can selectively perform the aeration operation and the stirring operation by switching the rotation direction of the shaft 2 between forward and reverse. As shown in FIG. 2, a control circuit including an inverter INV, a relay R, a timer T, and the like is connected to the motor M of the aeration stirrer 1 so that the motor is rotated forward and backward, and the set time is controlled. Selective switching is performed to control switching between the aeration operation and the stirring operation. Thus, for example, when the shaft 2 rotates counterclockwise, the sewage is stirred and, at the same time, the water at the bottom of the aeration tank is sucked into the cylindrical body 5 and sprayed into the air by the aeration blades 3 to perform the aeration operation. When the shaft 2 rotates in the opposite direction, only the stirring blade 4
The agitation operation of only agitation of sewage is performed. A conical disk 6 is mounted between the electric motor M of the shaft 2 and the aeration blade 3, and water stirred by the aeration blade 3 is supplied by the conical disk 6. The direction is changed and emitted radially. In this case, in order to increase the oxygen dissolution rate, it is necessary to determine the outlet area and the shape so that the resistance of the outlet formed at the upper end of the cylindrical body 5 is reduced. When the resistance of the outflow port is small, when the water level of the aeration tank A decreases and the aeration blade 3 is largely separated from the water surface, the pressure in the vicinity of the aeration blade 3 in the cylindrical body 5 decreases and a large amount of bubbles are generated. Therefore, the aeration operation cannot be started normally despite the filling of the water by the lower stirring blades 4. Conversely, when the resistance of the outlet is increased, the aeration start is good, but the power is consumed in flowing the water against the resistance, which causes a problem that the oxygen dissolution rate is reduced. Hereinafter, a method of operating the aeration stirrer of the present embodiment will be described. When the shaft M is rotated counterclockwise by the motor M, the aeration blades 3 are idle at the beginning of the rotation, but the stirring blades 4 provided in the water generate an upward flow. Thereby, water is filled in the cylindrical body 5 provided from underwater to above the water surface. Inside the cylinder 5, the aeration blades 3 that are inclined in the same direction as the stirring blades 4 are arranged.
Since it rotates counterclockwise in the same direction as the stirring blades 4, the water filled in the cylindrical body 5 flows further upward, and is jetted by the conical disk 6 from the opened outlet into the air. Aerating is performed by scattered radially. In this case, the time from the start of the aeration operation of the aeration stirrer 1 to the time when at least the inside of the cylinder 5 is filled with water, specifically, a short time of 20 to 60 seconds, preferably 30 seconds, from the start of the aeration operation, The rotation speed (the number of rotations) of the shaft 2 is set to be higher than the rotation speed during the normal aeration operation. As a result, the stirring blades 4 provided in the water generate a flow with a large flow rate upward, but the outlet width and shape of the flow outlet have a large resistance to the large flow rate, so that the cylindrical body 5 has a large resistance. It is possible to prevent the internal pressure from dropping, so that even when the water level drops, a good aeration operation can be started without generating bubbles. Also, after the aeration operation is normally started, even if the rotation speed of the shaft 2 is reduced to the rotation speed during normal operation (set rotation speed), once water is filled in the cylinder 5, In addition, since the suction of water into the cylindrical body 5 is performed continuously even with the aeration blade 3 alone, the continuous operation of the aeration becomes possible, and the normal aeration operation is continued without generating bubbles. On the other hand, after the aeration operation is started normally, the rotational speed of the shaft 2 is reduced to the preset rotational speed of the normal operation, so that the flow rate of water suction into the cylinder 5 decreases. However, since the shape of the outlet is suitable for the reduced flow rate during normal operation, the outlet resistance is small and the oxygen dissolution rate efficiency increases. During the total aeration time, most of the time other than the start-up time, the operation is performed with the outlet resistance small, so that the oxygen dissolution rate efficiency is high overall. In this case, if the steady rotation speed during aeration is increased more than necessary and the operation is continued, overaeration occurs and the water treatment deteriorates. When the shaft 2 is rotated in the opposite direction to the above, the rotation of the stirring blade 4 while the aeration blade 3 is idling causes the waste water in the aeration tank A to rotate as shown in FIG. Without generating air bubbles therein, a downward flow of water is generated to perform only stirring of the wastewater, and a good stirring operation can be performed. As described above, the method of operating the aeration stirrer of the present embodiment can reliably perform the aeration operation without lowering the oxygen dissolving rate efficiency even when the water level is greatly reduced. Since the aeration ability does not require the aeration blades to be installed unnecessarily low, the stirring operation can be reliably performed even when the water level rises significantly. FIG. 3 shows the control of the rotation speed of the shaft 2 at the start of the aeration operation. For example, the inverter INV, the relay R and the timer T are used so that the rotation speed becomes high only at the start of the aeration operation. , Pole number conversion motor (not shown)
And a relay and a timer are used. According to the operation method of the aeration stirrer of the present invention, the rotation speed of the shaft is increased at the start of the aeration operation, and a large flow rate is generated in the cylinder by the stirring blade. By increasing the resistance of the outlet with respect to the flow rate, it is possible to prevent the pressure inside the cylinder from dropping, so that even if the water level drops, a good aeration operation can be started without generating bubbles. After the start of the aeration operation, even if the rotation speed is reduced to the normal operation, even if the aeration blade is used alone, water is continuously sucked into the cylinder, so that normal aeration without generating air bubbles is performed. Driving can be continued. And, by reducing the rotation speed after the start of the aeration operation, the flow rate of water is reduced,
The aeration operation can be continued in a state where the resistance of the outlet is reduced and the oxygen dissolution rate efficiency is increased. in this way,
The operation method of the aeration stirrer of the present invention can reliably perform the aeration operation without lowering the oxygen dissolving rate efficiency even when the water level is greatly reduced, and requires the aeration blades due to the high aeration ability. Since it is not necessary to set the water level as low as above, the stirring operation can be reliably performed even when the water level rises significantly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of a method for operating an aeration stirrer according to the present invention, wherein (A) is an explanatory diagram showing an aeration operation, and (B) is an explanatory diagram showing a stirring operation. FIG. 2 is a front view showing an aeration stirrer used in the operation method of the embodiment. FIG. 3 is a graph showing an operation state of the aeration stirrer of the embodiment. [Description of Signs] 1 Aeration agitator 2 Shaft 3 Aeration blade 4 Agitating blade 5 Cylindrical body A Aeration tank M Motor R Relay T Timer INV Inverter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C02F 3/24 C02F 3/24 BF term (reference) 4D029 AA11 CC06 4D040 BB07 BB63 BB91 4G035 AB25 AE02 4G078 AA21 AB20 BA05 BA09 CA06 CA20 DA09 DA19 DB03

Claims (1)

Claims 1. An agitating blade rotating in water and an aeration blade rotating above the water surface are formed on a shaft rotated by an electric motor, and cover the periphery of the aeration blade. In the operation method of the aeration stirrer in which the cylinder is disposed concentrically with the shaft from near the stirring blade and the water introduced into the cylinder by the stirring blade is scattered around by the aeration blade, the aeration operation is started. A method of operating the aeration stirrer, wherein the rotation speed of the shaft is set to be larger than that during the normal aeration operation for at least the time until the cylinder is filled with water.