JPH0472600B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for dewatering incompressible sludge made 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 It was difficult to reduce the ratio to 35% or less. Therefore, in order to further reduce the moisture content, 3~
Compressed air of 6 kg/cm ² is introduced to expel moisture in the cake using air pressure, and an air blow process is performed to remove moisture adhering to the filter cloth surface and improve the peelability of the cake from the filter cloth. is being attempted. (For example, JP-A-53-67173, JP-A-57
(Publication No. 150410) (Problem to be solved by the invention) However, since incompressible sludge has a property of being highly permeable, it tends to crack due to the compressed air introduced during air blowing, and most of the Compressed air wastefully passes through the cracks and is discharged, making it impossible to significantly reduce the moisture content in the cake.For non-compressible compressed sludge, pressurization treatment and air blow treatment are required. It was considered difficult to reduce the moisture content in the cake to 30% or less even by combining the above methods. Therefore, there has been a need for a dewatering method that can dewater incompressible sludge 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 these conventional problems, and involves dewatering incompressible sludge using a dehydrator using a conventional method, and then filtering it. In a dewatering method for non-compressible sludge that involves introducing compressed air into the room and performing air blow treatment, the flow rate of filtrate per unit time discharged by air blow treatment is detected, and if the detected flow rate is higher than the set flow rate, This method is characterized in that the flow rate or pressure of compressed air is not changed, and when the detected flow rate is less than a set flow rate, the flow rate or pressure of compressed air is sequentially increased while draining the moisture in the cake. 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 supplied into the filter chamber 2 by a sludge pump 4 via a sludge valve 5 and a sludge pipe 6, and is dehydrated by a conventional method to remove moisture. The cake will have a ratio of about 40%. Next, with the mud feeding valve 5 open, the compressed air pressurized by the compressor 7 and stored in the tank 8 is reduced to 3 to 4 kg/cm ² by the valve device 9, and then passed through the pipe 15 to the mud feeding pipe 6. It is introduced into the interior for a very short period of time to perform back blowing 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/cm ² is again introduced into the filter chamber 2 from the valve device 9 to start the air blowing process. At this time, the first line 9a consisting of a pressure reducing valve 10a and a solenoid valve 11a of the valve device 9 is used, and the filtration area is 0.4 to 0.6 per ^m2 .
Air blow treatment is performed using compressed air at a low flow rate of about m ³ /min. As a result, the cake made of incompressible sludge does not crack, 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, when the flow rate of the filtrate decreases to about 100/m ² ·min after 2 to 3 minutes, the controller 14 closes the solenoid valve 11a of the first line 9a and closes the pressure reducing valve 10b and the solenoid valve 11.
The solenoid valve 11b of the second line 9b consisting of the second line 9b is opened, the flow rate of the compressed air is increased to, for example, 0.8 m ³ /min, and the air blowing process is continued. When a large amount of compressed air is introduced into the filter chamber 2 in this way, the moisture from the cake is actively discharged again, and when the flow rate of the filtrate decreases to a predetermined value again, the electromagnetic valve in the third line 9c 11c is opened to increase the flow rate of compressed air to, for example, 1.2 m ³ /min.
The above change in the flow rate of compressed air is as shown by the broken line A in Figure 2, and the final flow rate per unit time of compressed air is shown by the straight line B, which is the unit of compressed air in the conventional air blow treatment method. Even if the flow rate is higher than the flow rate per hour, the cake has been hardened by the air blowing process before that, so no cracks will occur, and the moisture content in the cake will decrease as shown by curve A in Figure 3. It is discharged until it reaches 20-25%. 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. Furthermore, according to the method of the present invention, the amount of filtrate can be increased as shown as A in FIG. has reached saturation and cannot be expected to increase over time. 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. Note that the pressure in the table indicates the original pressure inside the tank 8.

【table】

[Table] 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, there is also a method of increasing the flow rate of compressed air continuously in response to the flow rate of filtrate. Alternatively, 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 applicable not only to filter presses but also to other dehydrators such as belt presses and 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 water content in the cake of incompressible sludge, which was difficult to reduce to 30% or less by air blowing, can be reduced to 22-25%. 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. A graph showing the relationship between air blow time and moisture content, and FIG. 4 is a graph showing the relationship between air blow time and filtrate amount. 1: Dehydrator, 2: Filter chamber, 9: Valve device, 1
2: Flowmeter.

Claims (1)

[Claims] 1 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 unit discharged by air blow treatment. The flow rate of filtrate per hour is detected, and if the detected flow rate is higher than the set flow rate, the compressed air flow rate or pressure is not changed, and if the detected flow rate is lower than the set flow rate, the compressed air flow rate or pressure is increased sequentially. A method for dewatering incompressible sludge, which is characterized by draining water in a cake while dewatering the cake.