JPS59228907A - Operating method of filter press - Google Patents

Abstract

PURPOSE:To provide an operating method causing no variance in the thickness of formed dehydrated cake, and to make the thickness of the dehydrated cake approximately constant even when the properties of sludge are changed, by controlling the pressure and supply of a pressing fluid to a diaphragm. CONSTITUTION:The original liquid to be filtered is sent into a filtration chamber 47 of a filter press 4 through a supply pump at the specified pressure of 2- 10kg/cm<2>, for example, and filtered. When the pressure of the filtration chamber 47 is increased to the pressure exceeding the specified pressure, a pressing fluid 11 in a supply tank 5 is sent into a diaphragm 44. The pressing pressure is set at the pressure lower than the maximum pressure by about 1-2kg/cm<2>, for example, when the original liquid 10 is forced in. The fluid 11 for pressing is taken into the diaphragm 44 in correspondence with the change of the pressure balance, and the cake 12 in the filtration chamber 47 is pressed to a constant thickness. In this way, the amt. of the fluid 11 consumed is increased in proportion to the formation of the cake 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a filter press with a built-in diaphragm.

In recent years, many studies have been conducted on how to effectively utilize dehydrated cake. Along with this, facilities that can effectively utilize dehydrated cakes are being constructed. Many dehydrated cakes in such equipment that can be used effectively are processed to a certain size in consideration of handling during effective use. Therefore, even in the filtration process using a filter press, operation is required to always produce a dehydrated cake of a constant thickness.

Therefore, in the conventional operating method, the supply amount of the stock solution is kept constant, thereby making the thickness of the dehydrated cake constant. Such quantitative supply of stock solution can be achieved by, for example, appropriately setting the injection time of stock solution based on the operator's experience, or by measuring the amount of stock solution supplied and stopping the supply of stock solution when a certain amount is reached. This is done by means such as.

However, the above operating method does not take into account the characteristics of the raw solution, and therefore does not follow changes in sludge properties. For this reason,
For example, when the sludge concentration is high, the dewatered cake will be thick despite the constant supply, and conversely, when the sludge concentration is low, the dehydrated cake will naturally become thin. As described above, variations in the thickness of the dehydrated cake occur in response to changes in the concentration of sludge, and there is a strong desire to improve this point.

Therefore, an object of the present invention is to provide an operating method that does not cause variations in the thickness of the dewatered cake even if the characteristics of the raw solution, that is, the sludge properties change, and to make the thickness of the dewatered cake almost constant. be.

Based on the above object, the present invention provides for the surface of the filter cloth in the filter chamber to
When a certain amount of cake adheres, the injection pressure of the stock solution is no longer propagated to the entire surface of the flow chamber as the same pressure value, and especially as cake is formed, the filtration pressure decreases by the amount of pressure loss that gradually increases at the outer periphery of the flow chamber. Therefore, even if a squeezing pressure lower than the filtration pressure is applied to the outer periphery during the filtration process,
At the outer periphery, we focused on the phenomenon that the cake in the filter chamber is compressed, and during the filtration process in the filter chamber, we supplied the squeezing fluid at a pressure lower than this filtration pressure, and The start of compression in a portion is detected by the flow rate of the compressed fluid, and filtration is terminated when a predetermined supply amount is reached. In this operating method, since the start of squeezing corresponds to a change in the sludge properties of the raw solution, it is possible to always form a dehydrated cake of a predetermined thickness even when the sludge concentration changes, for example.

Embodiments of the present invention will be specifically described below with reference to the drawings.

First, FIG. 1 shows the system of the filtration process.

The supply tank 1 contains a stock solution 10, and this stock solution 10
is press-fitted by a supply pump 2 through a supply valve 3 into a filter press 4 having a built-in diaphragm.

On the other hand, the squeezing fluid 11 is stored inside the supply tank 5 and guided into the filter press 4 via the supply valve 6 . The pressure inside the supply tank 5 is set to the pressure necessary for compression by a pressure setting valve 8 and a comb bracer 9.

Note that the level of the fluid 11 inside the supply tank 5 can be read from the outside using a liquid level gauge 7.

Next, FIG. 2 shows an example of a filter press 4 with a built-in diaphragm. This filter press 4 is
The main part is composed of a large number of laminated filter plates 41 and a filter cloth 42 provided for each filter plate 41. The filter plate 41 has a supply hole 43 for the stock solution 10 at the center thereof, and diaphragms 44 are integrally formed on both sides. The fluid 11 is introduced into each of the supply ports 45 of the diaphragm 44 . Further, the filter cloth 42 is provided along the filtering surface 46 of the diaphragm 44, is in a sealed state along the outer periphery of the filter plate 41, and is connected to the supply hole 43 at a portion corresponding to the recess of the diaphragm 44. A flow chamber 47 is formed respectively.

Next, the operating method of the present invention will be explained together with the operation of the filter press 40.

First, the supply pump 2 sucks the stock solution 10 inside the supply tank 1, and flows it through the supply hole 43 of the filter press 4 under a predetermined press-in pressure, for example, 2 to 100 kg/cIa, through the supply valve 3 in an open state. It is sent into the chamber 47 to start filtration. After a certain time, the pressure in the flow chamber 47 is increased to a predetermined pressure value. In this state, the compression fluid 11 in the supply tank 5 is fed into the diaphragm 44 through the supply valve 6 under a predetermined compression pressure,
Squeezing begins. The value of this squeezing pressure is smaller than the maximum pressure when the stock solution 10 is press-fitted, for example, 1 to 2 kg/c+
The value is set to about a low value.

Under such pressure conditions, the solid particles in the stock solution 10 inside the flow chamber 47 become cake-like and adhere to the surface of the filter cloth 42, and are deposited one after another. As a result, inside the flow chamber 47, the stock solution flow path is pinched, and the flow resistance gradually increases. Moreover, since the cake 12 adheres and forms quickly on the outer periphery of the flow chamber 47, its resistance value is smaller than the supply hole 43,
In other words, it gradually becomes larger at a position farther away than part A, that is, part B on the outer circumferential side. In this way, a pressure difference is created between the A part and the B part inside the flow chamber 47, and the pressure in the B part eventually becomes lower than the compression pressure of the corresponding part of the diaphragm 44, that is, the pressure value of the fluid 11. At this point, the diaphragm 44 at that portion presses against the filter cloth 42 at the corresponding position and begins a squeezing operation in parallel with press-in filtration. In this way, the squeezing operation sequentially moves from part B to part A within the flow chamber 47 as the cake 12 is formed. When squeezing is started, the stock solution 10 no longer flows into the flow chamber 47 at that portion, so the thickness of the cake 12 at that portion becomes approximately constant in relation to pressure equilibrium.

In this way, the diaphragm 44 takes in the squeezing fluid 11 in response to changes in the pressure cover lance, thereby squeezing the cake 12 in the flow chamber 47 to a constant thickness. Correspondingly, the consumption amount of the fluid 11 increases in proportion to the formation of the cake 12. This consumption of a predetermined amount of the fluid 11 can be easily detected by the liquid level gauge 7.

When a predetermined amount of the fluid 11 is supplied, the supply valve 3 is closed, the operation of the supply pump 2 is stopped, and the supply of the stock solution 10 is ended. As already clear, the squeezing fluid 11
The consumption amount corresponds proportionally to the capacity, that is, the thickness, of the cake 12 inside the flow chamber 47. Therefore, when the supply of the stock solution 10 is finished in the above operating method, the cake 1 of a predetermined thickness is
This corresponds directly to the generation of 2.

In addition, although the above-mentioned Example shows the concave plate type filter press as -(j++, the type of this filter press 4 is naturally not limited to a concave plate type as long as it is a diaphragm compression type.

In the present invention, squeezing is started sequentially from the part where a predetermined amount of cake has been generated inside the flow chamber due to changes in the pressure balance, so that the generation of a cake of a constant thickness depends on changes in the sludge concentration in the raw solution. It is formed while following. Furthermore, since the filtration step and the compression step are performed in parallel, there is no need for switching from the undiluted solution injection step to the compression step, and moreover, the undiluted solution processing capacity per unit time is increased.

[Brief explanation of the drawing]

FIG. 1 is a system diagram for implementing the filter press operating method of the present invention, and FIG. 2 is a sectional view of essential parts showing an example of the filter press. 1. Supply tank, 2. Supply pump, 3. Supply valve, 4.
・Filter press with built-in diaphragm, 5. Supply tank, 6. Supply valve, 7. Level gauge 8. Pressure setting valve, 9. Combiner, 10. Raw solution, 11. For squeezing. Fluid, 12...cake, 41...filter plate, 42...filter cloth, 44...diaphragm, 45...supply port, 46...
Wave surface, 47...Flow chamber.

Claims (1)

[Claims] In a filter press with a built-in diaphragm, in which the stock solution is pressurized into a filter cloth placed between a large number of stacked filter plates, and the stock solution is squeezed by the expansion action of the diaphragm, the supply pressure of the stock solution is set to a predetermined pressure value. When this is reached, a squeezing fluid that expands the diaphragm is supplied at a pressure lower than the supply pressure of the stock solution, and when it is detected that the supply amount of this fluid has exceeded a certain amount, the injection of the stock solution is finished. A method of operating a filter press characterized by the following.