JPS6125478B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a belt press type dewatering apparatus for dewatering sludge generated in the treatment of water such as tap water, sewage, and industrial wastewater.

In a belt press type dewatering device, the first stage is a flocculating section that uniformly mixes and stirs sludge and a polymer flocculant to create flocculated sludge, and the gravity dewatering section that dewaters the flocculated sludge by gravity on a running endless cloth belt. Then, the sludge obtained in the gravity dewatering section is squeezed between two belts, the endless cloth belt and an endless cloth belt running at the top, which is provided in parallel with the belt, and the sludge is passed between a plurality of rolls. A pressurized dehydration section is provided for further dehydration by compression and shear force.
This belt press type dewatering apparatus has become rapidly popular in recent years because it is easy to operate, easy to maintain, and uses a small amount of flocculant, has a high solid content recovery rate, and has a high dewatering effect. In the gravity dewatering section of the device, unless the entire amount of supplied sludge is treated, the sludge may protrude from the belt side and the performance cannot be fully demonstrated. A certain amount of flocculant is automatically supplied based on the determined amount, forming an optimal flocculation floc. However, if there is a change in the properties of the sludge, the amount of flocculant may be too much or insufficient, resulting in incomplete flocculation, causing sludge to protrude from the belt side, turbidity of the liquid, etc., and the solids recovery rate to deteriorate. For this reason, there is a drawback that automatic operation is difficult when there are many variations in sludge properties. The present invention has been made in view of these circumstances, and provides a control method that eliminates the above-mentioned drawbacks, maintains optimal operating conditions, and enables automatic driving. A cloth belt is stretched so as to be conveyed between a plurality of rolls, and a gravity dehydration section and a pressure dehydration section are provided, and a flocculant supply device, an endless belt conveyance drive device, and a stock solution supply device each having a control circuit are provided. In a method for controlling a belt press type dewatering device, a means for detecting a sludge liquid level is provided in the gravity dewatering section, and the flocculant supply amount and endless belt feeding are controlled based on an output signal from the detecting means so that the sludge liquid level is constant. This is a method of controlling a belt press type dewatering apparatus, characterized in that the control circuit is operated to sequentially adjust the speed and the amount of stock solution supplied in the above order.

An embodiment of the present invention will be described based on the drawings.
FIG. 1 is a system diagram of an embodiment according to the present invention.
1 is a stock solution supply device that supplies a fixed amount of stock solution A such as sewage sludge, 2 is a flocculant supply device that supplies a fixed amount of flocculant B such as a polymer flocculant, and 3 is the sludge supplied from the devices 1 and 2. A flocculation mixing tank that uniformly mixes flocculant with a stirrer attached to the top and measures the flocculation of sludge, and 4 is a belt press type dewatering device that is equipped with a gravity dewatering section 4' and a pressure dewatering section 4'', which will be described later, to dewater the sludge. machine,
4' is a gravity dewatering section that dewaters the coagulated sludge introduced from the flocculation mixing tank 3 by gravity on a running endless cloth belt 5; A pressurized dehydration section which further dehydrates water by compression and shear force by being sandwiched between two belts with an upper running endless cloth 6 provided and running between a plurality of rolls, 5 and 6 are synthetic fibers such as nylon and polyester, etc. It is a cloth belt with a constant width woven with a belt, stretched endlessly between rolls, and run at a constant speed in the direction of the arrow by a drive device 7.
8 is a cloth belt drive device for the cloth belts 5 and 6; 8 is a sludge receiving tank in which the flocculated sludge is received and retained using the cloth belt 5 of the gravity dewatering section 4' as a bottom surface; 9 is a sludge conveyed between the cloth belts 5 and 6; The cloth belts 5 and 6 run between the rolls, and the fabric belts 5 and 6 run between the rolls. This applies shearing pressure to the cake. Reference numerals 11 and 11' denote drive rolls for the cloth belts 5 and 6, which invert the cloth, peel off the dehydrated sludge with a scraper 17, and discharge it as a dehydrated cake C out of the system. 12 is a liquid collector for collecting the filtered liquid. The collected liquid D is extracted and discharged outside the system. In the sludge receiving tank 8 provided in the gravity dewatering section 4' of such a known belt press type dewatering device, as a liquid level detection means,
A liquid level control meter 13 equipped with a signal transmission circuit is installed,
Each control circuit 1 continuously detects the liquid level of sludge.
Optimum operation is always performed by sequentially issuing signals to 5, 16, and 14. In the belt press type dewatering device having the above configuration, a case where the sludge liquid level in the sludge receiving tank 8 exceeds a predetermined height due to an insufficient amount of flocculant added will be described. outputs a signal to the supply amount control circuit 15 of the flocculant supply device 2 and increases the rotation speed of the supply device 2, thereby increasing the supply amount proportionally.If the liquid level does not drop even after a certain period of time, outputs a signal to the rotation speed control circuit 16 of the endless belt running drive device 7 to increase the number of rotations of the drive device 7, thereby increasing the running speed of the cloth belts 5, 6, and even after a certain period of time has elapsed, there is no improvement. If this is not observed, a signal is output to the supply amount control circuit 14 of the stock solution supply device 1 to reduce the number of rotations of the supply device 1, thereby reducing the stock solution supply amount. If necessary, an alarm may be installed to issue an alarm. If the above operations do not resolve the problem, stop supplying the stock solution and flocculant, and after a certain period of time, shut down the entire system including attached related equipment. In addition, the above system continuously detects the liquid level of sludge in the sludge receiving tank 8 and outputs a signal, and each control circuit 15,
16 and 14 in sequence, but if the flocculant supply rate is increased and the liquid level does not drop even after a certain period of time has passed, further increase the flocculant supply rate, and if no improvement is seen, further increase the flocculant supply rate. Each control circuit 15, 16, 14 may be switched in a stepwise manner in response to a signal from the liquid level controller 13 to increase the flocculant supply amount, or in other embodiments, the sludge receiving tank When the liquid level of the sludge in step 8 becomes below a predetermined height, the amount of flocculant supplied can be proportionally reduced to operate with the optimum amount of flocculant.

When dewatering sludge generated in the treatment of water such as clean water, sewage, and industrial wastewater, the control of the present invention is carried out using a belt press type dehydrator equipped with the control mechanism of the present invention configured as described above. If sludge is dehydrated using this method, even if the properties of the sludge change, the amount of flocculant supplied will be insufficient and the flocculation of the sludge will be incomplete, resulting in sludge protruding from the belt side and turbidity of the liquid. This is an extremely effective control method industrially because it can completely automate the equipment and enable unmanned operation.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an embodiment according to the present invention. 1: Stock solution supply device, 2: Coagulant supply device, 3:
Coagulation mixing tank, 4: Belt press type dehydrator, 4':
Gravity dewatering section, 4'': Pressure dewatering section, 5, 6: Cloth belt, 7: Cloth belt drive device, 8: Sludge receiving tank,
9: Low pressure roll, 10: Press roll, 11,1
1: Drive roll, 12: Liquid collector, 13: Liquid level controller, 14: Stock solution supply amount control circuit, 15: Coagulant supply amount control circuit, 16: Rotation speed control circuit, 17:
Scraper, A: Stock solution, B: Coagulant, C: Dehydrated cake, D: Liquid.

Claims (1)

[Claims] 1. An endless cloth belt is stretched between multiple rolls, and a gravity dehydration section and a pressure dehydration section are provided.
In the method for controlling a belt press type dewatering device including a flocculant supply device, an endless belt conveyance drive device, and a stock solution supply device each having a control circuit, a means for detecting a sludge liquid level is provided in the gravity dewatering section, and the sludge liquid level is The belt is characterized in that the control circuit is operated to sequentially adjust the amount of coagulant supplied, the endless belt feeding speed, and the amount of stock solution supplied in this order based on the output signal from the detection means so that the surface of the belt is constant. Control method for press type dewatering equipment.