JPS6115715A - Dehydration treatment of non-compressible sludge - Google Patents

Abstract

PURPOSE:To dehydrate non-compressible sludge until the moisture content in a cake is lowered to a large extent, by discharging moisture in the cake while successively increasing the flow amount or pressure of compressed air so as to allow the same to correspond to the flow amount of the filtrate discharged by air blow treatment. CONSTITUTION:The non-compressible sludge in a sludge tank 3 is subjected to dehydration treatment according to a usual method to form a cake with moisture content of about 40%. Subsequently, back-blow treatment is performed if necessary and, thereafter, a sludge valve 5 is closed and compressed air is introduced into a filter chamber 2 from a valve device 9 to start air blow treatment. At this time, air blow treatment is performed by a low flow amount of comppressed air. The flow amount of the discharged filtrate is detected by a flow meter 12 and, when the flow amount of the filtrate is reduced, the flow amount of compressed air is increased by a controller 14 to succeed air blow treatment. When the flow amount of the filtrate is again reduced to a predetermined value, the flow amount of compressed air is further increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for dewatering incompressible sludge consisting of incompressible fine particles such as coal slurry and inorganic sludge.

(Prior Art) Generally, filter presses are widely used for dewatering sludge, and pressure treatment is performed in which pressure is applied to sludge to discharge water. However, even if such pressure treatment is applied to incompressible sludge, it is difficult to significantly reduce the moisture content in the cake, and even with additional compression using a diaphragm, the moisture content in the cake is 3
It was difficult to keep it below 5%. Therefore, in order to further reduce the water content, 3 to 5 kg was added to the filter chamber after pressure treatment.
An air blow process was attempted in which compressed air at a rate of g/cJ was introduced to exhaust the moisture in the cake using air pressure, and at the same time remove the moisture adhering to the filter cloth surface and improve the peelability of the cake from the filter cloth. It is being (For example, JP-A-53
(Problems to be solved by the invention) However, since incompressible sludge has high air permeability, compressed air introduced during air blow treatment It is easy to cause cracks in the cake, and most of the compressed air wastefully passes through the cracks and is exhausted, making it impossible to significantly reduce the water content in the cake. However, it has been difficult to reduce the moisture content in the cake to 30% or less even when a combination of pressure treatment and air blow treatment is performed. Therefore, there has been a need for a dewatering method that can dewater incompressible lη mud until the water content in the cake is further significantly reduced.

(Means for Solving the Problems) The present invention was completed in order to solve the problems of the conventional art, and the present invention is made by dewatering incompressible sludge using a dehydrator using a conventional method, and then dewatering the incompressible sludge in a filter chamber. In a dewatering method for incompressible sludge that involves introducing compressed air and performing air blow treatment, the flow rate of the filtrate discharged during air blow treatment is detected, and the flow rate or pressure of compressed air is sequentially increased in response to the detected flow rate. It is characterized by draining the moisture in the cake at the same time.

Next, the present invention will be explained in more detail with reference to the drawings.
(1) is a dehydrator such as a filter press, (2) is its filter chamber, and the incompressible sludge in the sludge tank (3) is transported by the sludge pump (4) to the sludge valve (5) and the sludge pipe. (6) and into the filter chamber (2), where it is dehydrated using a conventional method to form a cake with a water content of approximately 40%.6 Next, with the slurry feeding valve (5) open, the compressor (7) )
The compressed air pressurized by the tank (8) and stored in the tank (8) is reduced to 3 to 4 kg/ct& by the valve N (9), and then pumped into the mud feeding pipe (6) via the pipe (15). Introduce it for a short time and perform back blow treatment. This back blowing process is performed to remove the sludge remaining in the sludge pipe (6), and may be omitted depending on the case. Next, the mud feeding valve (5) is closed and compressed air of 3 to 4 kg/cJ is again introduced into the filter chamber (2) from the valve device (9) to start the air blowing process. In this case, the first line (9a) consisting of a pressure reducing valve (10a) and a solenoid valve (lla) of the valve device (9) is used, and the filtering area is 0.4 to 0.6 per filtration area.
n? Air blow treatment is performed using compressed air at a low flow rate of about 1/2 min. As a result, the cake made of incompressible sludge does not crack, and the moisture in the cake is replaced by compressed air, and the discharged filtrate flows into the filtrate tank (13) while its flow rate is detected by the flow meter (12). However, after 2 to 3 minutes, the flow rate of the filtrate is, for example, 100 j!
/ When it decreases to about %・min, the controller (14)
The solenoid valve (Ila) in the first line (9a) is closed, and the solenoid valve (11b) in the second line (9b), which consists of a pressure reducing valve (10b) and a solenoid valve (llb), is opened to reduce the flow rate of compressed air. The air blowing process is continued by increasing the rate to, for example, 0.8%/min. In this way, a large amount of compressed air flows into the filter chamber (2
), the moisture from the cake will be actively drained again, and when the flow rate of the filtrate decreases to the predetermined value again, the solenoid valve (ll) in the third line (9c) will be activated again.
c) is opened to increase the flow rate of compressed air to, for example, 1.2n/min.
As shown by the broken line in the figure, even if the final flow rate of compressed air per unit time is larger than the flow rate of compressed air per unit time in the conventional air blow treatment method shown by straight line B, the Since the cake has been hardened by the air blow treatment, no cracks will occur, and the moisture in the cake will be discharged until the moisture content reaches 20 to 25%, as shown by curve 4 line A in FIG. On the other hand, in the conventional method, it is difficult to reduce the water content to 30% or less, as shown by curve B in FIG. Next, data obtained by implementing the method of the present invention under various conditions are shown in the following table in comparison with the conventional method.

In addition to the method of increasing the flow rate of compressed air in stages when the flow rate of filtrate decreases to a predetermined value as described above, the flow rate of compressed air may be increased continuously in correspondence with the flow rate of filtrate. Furthermore, in addition to increasing the flow rate of compressed air, a method of increasing its pressure may also be adopted. Furthermore, the method of the present invention is not limited to filter presses, but can also be applied to belt press machines,
It can also be applied to other dehydrators such as vacuum dehydrators.

(Effects of the Invention) As is clear from the above description, the present invention detects the flow rate of the filtrate discharged by air blowing, and sequentially increases the flow rate or pressure of compressed air in accordance with the detected flow rate, and Since the water inside is discharged, low flow rate or low pressure compressed air is introduced at the start of air blowing, which tends to cause cracks, and as dehydration progresses, a more powerful air blowing process can be performed. The moisture content in the cake of incompressible sludge, which was difficult to reduce to 30% or less by air blowing, has been reduced to 22% or less.
It can be reduced to 25%. Moreover, since no cracks occur in the cake, the total amount of air and running costs can be significantly reduced.Also, the state of water discharge from the cake can be detected by the flow rate of the filtrate, and the flow rate or pressure of the compressed air can be controlled. Since the number is increased sequentially, there is no wastage of operating time, and the dehydration process can be carried out efficiently. Therefore, the present invention greatly contributes to the development of industry as it solves the problems of the conventional dewatering treatment method for incompressible sludge.

[Brief explanation of drawings]

Fig. 1 is an explanatory layout diagram showing an example of a device used to implement the method of the present invention, Fig. 2 is a graph showing the relationship between air blow time and air amount in an embodiment of the method of the present invention, and Fig. 3 is the same. It is a graph showing the relationship between air blowing time and moisture content. (1): Dehydrator, (2): Filter chamber, (9): Valve device,
(12): Flowmeter.

Claims (1)

[Claims] In a dewatering method for incompressible sludge, in which incompressible sludge is dehydrated using a dehydrator using a conventional method and then compressed air is introduced into the filter chamber to perform air blow treatment, the flow rate of the filtrate discharged by air blow treatment is A method for dewatering incompressible sludge, which comprises detecting the detected flow rate and sequentially increasing the flow rate or pressure of compressed air in response to the detected flow rate while draining water in the cake.