JP2869409B1 - Operating method of filter press - Google Patents

Abstract

An object of the present invention is to simplify management items in an operation method of a filter press and to improve uniformity of a moisture distribution inside a dewatered cake. A method of operating a filter press in which pulverized slurry of ceramic raw material particles or the like is pressed into a filter press by a reciprocating pump and dewatered to obtain a dewatered cake having a suitable amount of water for a subsequent kneading and molding step. The pressure of the pulsating pump is measured over time, and the differential pressure between the set of maximum value P _{H (n)} and the minimum value P _{L (n + 1)} or the set of maximum value P _{L (n + 1)} is measured. _The reciprocating pump is stopped when the pressure difference between _{H (n)} and the minimum value P _{L (n-1)} reaches a predetermined set value Ps.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method of operating a filter press for dewatering a slurry obtained by mixing a ceramic raw material with water to obtain a dewatered cake.

[0002]

2. Description of the Related Art Conventionally, in a method of manufacturing a ceramic, wet mixing and pulverization of a raw material, dehydration, kneading, molding, drying, and firing are performed in this order. In this dewatering step, the slurry having a water content of about 50% produced by the wet mixing and pulverization in the previous step is dewatered by a filter press to obtain a dewatered cake having a water content suitable for molding, for example, a water content of about 20%. This filter press includes a large number of opposed and closely-attached filter plates, and a filter space is formed between the filter plates by opposed filter cloths. Then, into this filtration space, the slurry is press-fitted from the inlet at the center portion of the filter plate and is filled. At the same time, the water in the slurry is separated by passing through the filter cloth by pressurization, and the remainder is filtered as a dewatered cake. It can be obtained with the space filled.

The operation of such a filter press will be further described with reference to FIG. 1. First, in order to press the slurry from the slurry tank 1 into the empty filter press 2, the air valve 22 is closed and the turbo pump 4 is turned off. Drive, valve 4
1. Feed into the filter press 2 via the slurry inlet valve 31. This is because there is almost no pressure load in the so-called early stage of operation when the filter press 2 is empty, and therefore the turbo pump 4 which is not suitable for high pressure but has high discharge capacity is suitable.

[0004] Next, when the filter press 2 is temporarily filled with mud and dewatering starts, the press-fitting pump is switched from the turbo pump 4 to the diaphragm pump 3 which is a kind of reciprocating pump. Thereafter, the press-in of the slurry is continued and the dewatering proceeds at the same time, and the dewatered cake is accumulated in the filter press 2. The operation termination timing of the diaphragm pump 3 is as follows. It was determined by various methods.

(1) The total operation time of the diaphragm pump is determined empirically, and the operation is stopped when the total time comes. Although this method is the simplest and the most error-free management method, it cannot cope with fluctuations in water and particle size of the slurry, or fluctuations in conditions such as filter cloth clogging. There is a problem that the distribution and the like vary widely.

(2) The elapsed time from when the maximum pressure is reached is empirically determined, and when the time has arrived, the operation is stopped. Although this method has the advantage that a uniform dewatered cake can be easily obtained compared to the previous method, the operation time must be set longer on the safe side to reduce the variation in the internal moisture distribution. There was a waste that the press was operated for an unnecessarily long time.

(3) The amount of dewatered water is measured, and the operation is stopped when a predetermined amount of water is dehydrated. In this method, in FIG.
It is based on the idea that if the amount is measured, the water content of the dehydrated cake accumulated in the filter press can be estimated based on the slurry water value measured in advance. The water estimated by the method is an average value of the whole dewatered cake, and is a relatively reproducible method in this respect, but is an index independent of the uniformity of the internal water distribution in the dewatered cake. There was a problem in the dispersion of the internal moisture distribution.

[0008] As described above, the diaphragm pump 3
After stopping the operation, the inlet valve 31 is closed, the return valve 21 is opened, the air valve 22 is opened, and compressed air is supplied to return the slurry remaining in the center portion of the filter press 2 to the slurry tank 1. Then, a series of dewatering steps by the filter press is completed. Then, the target dewatered cake can be taken out by opening the filter plate of the filter press.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can simplify the management items in a method of operating a filter press using a reciprocating pump, and can reduce the amount of dewatered cake. Provided is a method for operating a filter press that can improve the uniformity of internal moisture distribution.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method of operating a filter press according to the present invention is directed to a filter press in which slurry is pressed into a filter press by a reciprocating pump and dewatered to obtain a dewatered cake. Operating method, characterized in that the stop time of the reciprocating pump is determined based on the differential pressure between the adjacent maximum value and minimum value of the pulsating pressurizing pressure.

The method for operating a filter press of the present invention can be preferably embodied in the following mode. (1) A mode in which the reciprocating pump is stopped when the differential pressure between the highest value and the lowest value reaches a predetermined set value. (2) A mode in which the differential pressure between the highest value and the lowest value is continuously measured a predetermined number of times, and the reciprocating pump is stopped when the average value reaches a predetermined set value. (3) An embodiment using a diaphragm pump as the reciprocating pump.

[0012]

Next, an embodiment of a filter press operating method according to the present invention will be described with reference to FIGS. First, the reciprocating pump used in the present invention will be briefly described. FIG. 3 is a schematic sectional view for explaining the principle of a diaphragm pump which is a kind of a reciprocating pump, and a pump casing is formed of an elastic membrane plate (diaphragm). 5
It is composed of a driving liquid chamber 51 and a suction / discharge liquid chamber 52 partitioned by zero. The driving liquid chamber 51 is filled with hydraulic oil such as machine oil, and communicates with a plunger 53 that is reciprocally movable by an external crankshaft (not shown) or the like. Corresponding to the above, the elastic membrane plate 50 itself is assembled so as to reciprocate in the direction from the driving liquid chamber 51 to the suction / discharge liquid chamber 52 and then in the direction from the suction / discharge liquid chamber 52 to the driving liquid chamber 51.

On the other hand, an inlet valve 54 and an outlet valve 55 having a check function are disposed in the suction / drainage chamber 52, and the suction / drainage chamber 52 is first opened in accordance with the reciprocating operation of the elastic membrane plate 50 described above. When expanded, the outlet valve 55 is closed and the inlet valve 54 is opened to suck the transport liquid into the suction / drain chamber 52. Next, when the suction / drainage chamber 52 is reduced, the inlet valve 54 is closed and the outlet valve 55 is opened to allow the target liquid to flow through the suction / drainage chamber 5.
2 will be pushed out. Thus, in the diaphragm pump, the reciprocating operation of the plunger 53 causes
The target liquid can be pulsated while the driving operation is repeated in the order of delivery, pause, delivery, and pause.

As shown in FIG. 3, in the diaphragm pump, although the target liquid passes through the suction / drainage chamber 52, it does not come into contact with the drive liquid chamber 51 including the plunger 53. There are many examples of pumps suitable for conveying and pressurizing a slurry made of a ceramic raw material, since contamination of wear impurities including the like can be avoided.

In this diaphragm pump, even if the elastic membrane plate 50 is omitted and the driving liquid chamber 51 is also included in the suction / discharge liquid chamber 52, the same pump operation is performed by the reciprocating operation of the plunger 53. It is possible to do. The reciprocating pump referred to in the present invention includes a pump in which an elastic membrane plate (diaphragm) is omitted, in addition to the above-mentioned diaphragm pump.

By using a reciprocating pump having such an operation principle, a liquid containing a solid content is fed into a filtration device, the solid content is blocked by a filtration membrane, the liquid portion is permeated, and a solid-liquid separation is performed. By examining the elapse of the pump time and the transition of the pump pressure in the operation, it is possible to know a pulsating and changing situation as shown in the graph of FIG.

The graph of FIG. 2 exaggerates the pulsating and changing situation. When the target liquid is sent out from the reciprocating pump, the pump pressure increases due to the permeation resistance of the filtration membrane. However, when the feeding is temporarily stopped, the water pressure permeates through the filtration membrane, so that the pump pressure decreases. This shows a situation in which filtration proceeds while repeating rising and falling. Here, the line shown in FIG.
₅ is a graph sequentially connecting _{H (n)} and a minimum pressure P _{L (n + 1)} . The line is a graph showing the time course of the differential pressure between the maximum pressure and the minimum pressure.

The present invention is based on the technical background of the pressure characteristics of the reciprocating pump described above. The slurry, which is a solid-liquid mixture composed of crushed ceramic raw material particles and a predetermined amount of water, is applied to a filter press by the reciprocating pump. Press in,
It is premised on a method of operating a filter press for dewatering and obtaining a dewatered cake having a suitable amount of water for the subsequent kneading and molding steps.

The most characteristic point is that the pressurizing pressure of the pulsating pump is measured with the passage of time to determine the stop time of the reciprocating pump when the operation of the filter press is completed. Then, the differential pressure between the adjacent highest value and lowest value is calculated and determined based on this.

More specifically, the following form is preferable. (1) The difference between an arbitrary maximum value PH _(n) after a certain amount of time and the next minimum value minimum value PL _{(n + 1)} or the minimum minimum value PL _(n-1) which appears before it. When the pressure reaches a predetermined set value Ps, the reciprocating pump is stopped. This differential pressure converges as the operation time advances, as indicated by the line in FIG. 2. However, when the internal water distribution of the dehydrated cake becomes substantially uniform, it converges to show a substantially constant value. Therefore, a set value Ps at which such a situation can be reproduced may be determined in advance as a comparison standard, and the set value Ps may vary depending on various conditions such as the moisture, particle size, viscosity, and temperature of the target slurry. Therefore, it is preferable that a test operation is performed in advance and the most preferable value is checked and determined in advance.

(2) The differential pressure between the maximum value and the minimum value is continuously measured a predetermined number of times, and when the average value reaches a predetermined set value Ps, the reciprocating pump is stopped. In this case, there is an advantage that the measurement error of the differential pressure itself can be minimized, the operation of the reciprocating pump can be stopped under optimal conditions, and useless operation can be prevented. Note that _{(n) in} the display of the maximum value P _{H (n)} means that it is the nth time after the start of operation.

(3) Further, in the present invention, to determine the stop time of the reciprocating pump, a rate of change per hour of the differential pressure between the maximum value and the minimum value is calculated, and the rate of change of the differential pressure is determined. The reciprocating pump may be stopped when the value converges below a predetermined set value.

The line in FIG. 2 is a graph showing such a change in the differential pressure, and shows the convergence state. The movement of this line represents a situation in which the filtration resistance increases and the value of the differential pressure decreases as filtration proceeds as the filtration chamber fills the filtration chamber of the filter press. When the dehydration cake reaches a state where it is full, that is, when the internal water distribution of the dehydration cake becomes substantially uniform, the differential pressure converges and shows a substantially constant value.

Therefore, if the reciprocating pump is stopped when the rate of change of the differential pressure converges to a predetermined value close to zero, a dehydrated cake with less variation can be obtained. Further, in the present invention, the pump is stopped when the microstructure in the cake such as the degree of filling of the filled solid particles and the arrangement of the particles is in a state as described above. Even if there are fluctuations in the composition, slurry viscosity, temperature, pH, particle size distribution, etc., which are factors that cause the filter press time to vary, the advantage is obtained that the influence on the stop timing of the reciprocating pump set by the present invention is small. It is a field that can be done.

Next, experimental examples of the present invention are shown together with comparative examples 1 and 2. In this experimental example, the pulsating pressurizing pressure of the diaphragm pump shown above was measured with the passage of time, and the next highest value P _{H (n)} and the next lowest value P
The differential pressure from _{L (n + 1)} is calculated, and when the pressure reaches a predetermined set value Ps, the reciprocating pump is stopped.
In Comparative Examples 1 and 2, the same diaphragm pump, filter press, and slurry as those in the above-described experimental example were used, but the pressure reached a predetermined set pressure after a lapse of time since the operation of the pump. A method was adopted in which the operation was continued for a certain set time from the time point and then stopped. The set pressure patent set time was determined as described below.

The experimental results are shown in Table 1 for Comparative Example 1 and Table 2 for Comparative Example 2. Comparative Example 1
Investigated the pressure and duration for obtaining the best results in the case where a new filter cloth was used, and determined the above-mentioned constant set pressure and set time based on the result. Therefore, the first condition of Comparative Example 1 is similar to the first condition of the experimental example of the present invention, and the result is similar.
Further, in Comparative Example 2, constant set pressure and set time were similarly determined based on a state where the filter cloth was clogged after 50 uses. Therefore, the 50th condition of Comparative Example 2 was:
This is similar to the 50th condition of the experimental example of the present invention, and the result is almost the same. In addition, the value of the water distribution was compared with the difference between the average water content of the central portion and the average water content of the surface in the thickness direction of the cake.

[0027]

[Table 1]

[0028]

[Table 2]

According to the experimental results, in the experimental example of the present invention, the variation of the average moisture Rmax = 0.5, the moisture distribution difference inside the cake = 0.8 to 1.4, and the change of the required operating time = 1.
Compared to 20 to 140 minutes, in Comparative Example 1,
Even after the first to 50th operation, the dispersion of the average moisture Rmax = 3.5, and the difference in moisture distribution inside the cake = 1.4 to
3.0, the required operation time = 120 to 100 minutes, and the variation in the average moisture value was remarkably large, and there was a problem in quality as it was.

In Comparative Example 2, the average moisture variation R
max = 1.0, moisture distribution difference inside the cake = 1.0-1.
6. The required operating time = 160 to 140 minutes, and the distribution of moisture inside the cake is fair, but the variation in the average moisture is large, especially the operating time reaches a maximum of 160 minutes, and is a maximum of 140 in the case of the present invention. It can be understood that useless driving for 20 minutes was performed in comparison.

[0031]

The operation method of the filter press of the present invention is as follows.
As described above, the control items in the operation method of the filter press can be simplified, the uniformity of the internal moisture distribution of the dewatered cake can be improved, and the useless operation time can be reduced. There is an excellent effect that the operation efficiency can be improved because it can be saved. Therefore, the present invention has an extremely large industrial value as an operation method of a filter press which has solved the conventional problems.

[Brief description of the drawings]

FIG. 1 is a summary flowchart showing an outline of a filter press device.

FIG. 2 is a graph showing a relationship between pump pressure and time.

FIG. 3 is a sectional view of a main part for explaining the principle of a diaphragm pump.

[Explanation of symbols]

1 Slurry tank, 2 filter press, 21 return valve, 22 air valve, 3 diaphragm pump, 3
1 inlet valve, 4 turbo pumps, 41 valves, 6
Measuring tank.

Claims (4)

(57) [Claims] 1. A method for operating a filter press in which a slurry is pressed into a filter press by a reciprocating pump and dewatered to obtain a dewatered cake, wherein a difference between adjacent maximum and minimum values of pulsating pressure is determined. A method for operating a filter press, wherein a stop time of a reciprocating pump is determined based on pressure. 2. The method of operating a filter press according to claim 1, wherein the reciprocating pump is stopped when the pressure difference between the highest value and the lowest value reaches a predetermined set value. 3. The filter press according to claim 1, wherein the differential pressure between the highest value and the lowest value is continuously measured a predetermined number of times, and the reciprocating pump is stopped when the average value reaches a predetermined set value. Driving method. 4. The method according to claim 1, wherein said reciprocating pump is a diaphragm pump.