Air blowing method for filter press

Abstract

To provide an air blow method of a filter press that can efficiently decreases water content ratios of dehydrated cake, while preventing air consumptions required in air blow from being increased unnecessarily.SOLUTION: In an air blow method of a filter press, in which undiluted liquid is supplied to a filtration chamber 9 formed of a plurality of filter plates 5 and is compressed and dehydrated in a diaphragm 10 annexed to the filtration chamber 9, and air is introduced into the filtration chamber 9 so as to perform air blow, a reference value at which a pressure in a diaphragm chamber 11 is preliminarily increased and a pressure boosting value at which the pressure in the diaphragm chamber 11 is gradually boosted by a predetermined pressure are set, a measured value is compared with the reference value in an air-blow step, the air blow step is continued in a same condition, when the measured value is in a range of the reference value, and a holding pressure in the diaphragm chamber 11 is boosted by the pressure boosting value, when the measured value is out of the range of the reference value, and then the air blow step is continued, which can block voids in dehydrated cake and can perform the air blow efficiently.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to air blowing for a filter press, and more particularly to a method of air blowing for a filter press in which the retained pressure in a diaphragm chamber is increased during air blowing. [Background technology]

[0002] Conventionally, in filter presses that compress dehydrated cake by expanding a diaphragm, there has been an air blow method in which compressed air is sent to the cake in the filtration chamber as a means for removing moisture between cake particles that is difficult to push out with mechanical squeezing pressure.

[0003] Patent Document 1 discloses a technique for detecting the flow rate of the filtrate discharged by an air blowing process in which compressed air is introduced into a filter chamber, and gradually increasing the flow rate or pressure of the compressed air according to the detected flow rate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 15715 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional air blowing methods have a problem in that voids (air passages) are generated inside the cake as moisture is discharged from the cake, and the air sent into the filtration chamber passes preferentially through voids with low resistance (short pass). This increases the amount of air required to reduce the moisture content of the cake. Furthermore, increasing the amount of air supplied causes cracks to form in the dehydrated cake, resulting in uneven dehydration of the dehydrated cake and increased work in the post-processing process, making efficient air blowing difficult.

[0006] The technology of Patent Document 1 can slightly reduce the moisture content of the cake by gradually increasing the flow rate or pressure of the compressed air used for air blowing, but it also promotes the action of air blowing to widen the voids inside the cake. Since the voids generated at the beginning of air blowing are further expanded as the flow rate or pressure increases, the tendency of compressed air to short-pass accelerates, and the moisture content of the cake cannot be reduced uniformly. In addition, if an attempt is made to reduce the moisture content of the cake from this state, there is a problem that a huge amount of compressed air is consumed.

[0007] The present invention provides an air blowing method for a filter press that prevents a wasteful increase in air consumption due to cracks in a dehydrated cake or gaps between cake particles that occur during air blowing, thereby providing an efficient air blowing method. [Means for solving the problem]

[0008] In a filter press air blowing method, a raw liquid is supplied to a filtration chamber formed by a plurality of filter plates, and the raw liquid is compressed and dehydrated by a diaphragm attached to the filtration chamber, and air is introduced into the filtration chamber to blow the raw liquid. At least one of the flow rate of air supplied to the filtration chamber, the flow rate of air discharged from the filtration chamber, and the pressure of air supplied to the filtration chamber. Reference value for increasing pressure in the diaphragm chamber In addition to setting A boost value is set to gradually boost the pressure in the diaphragm chamber by a predetermined pressure, and during the air blowing process, the measured value is compared with a reference value. If the measured value is within the range of the reference values, the air blowing process is continued under the same conditions. If the measured value is outside the range of the reference values, the retained pressure in the diaphragm chamber is increased by the boost value and the air blowing process is continued. This eliminates voids in the dehydrated cake that occur during air blowing, and enables efficient air blowing.

[0010] When the retained pressure in the diaphragm chamber is increased by the boost value, the amount of air supplied to the filtration chamber is increased by a specified amount, thereby making it possible to reduce the moisture content of the dehydrated cake without applying a sudden force to it. Effect of the Invention

[0011] The air blowing method for a filter press according to the present invention can prevent cracks and voids from occurring in the dehydrated cake, and the air does not short-pass. Since the air can be uniformly sent into the dehydrated cake, the air can be supplied with high efficiency, and the moisture content of the dehydrated cake can be further reduced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a conceptual diagram of a filter press according to the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 13 is a partial conceptual diagram of a filtration chamber formed by closing parallel filter plates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] FIG. 1 is a conceptual diagram of a filter press according to the present invention. In the filter press 1, a number of filter plates 5... are movably supported on guide rails 4 that are bridged between front and rear frames 2 and 3. A clamping cylinder 6 provided on one of the frames 3 moves the multiple filter plates 5... in the axial direction.

[0014] FIG. 2 is a partial vertical cross-sectional perspective view of the filter plates arranged in parallel. A concave filter bed 7 is formed on each filter plate 5, and a filter cloth 8 is suspended from this filter bed 7 to form a filtration chamber 9 between adjacent filter plates 5, 5. A diaphragm 10 is stretched over one of the filter beds 7, forming a diaphragm chamber 11 inside the filtration chamber 9.

[0015] FIG. 3 is a schematic diagram of a part of a filtration chamber formed by closing parallel filter plates. A raw liquid supply port 12 is provided at the top of the filter plate 5, and raw liquid is pressure-fed into the filtration chamber 9 from a raw liquid supply pipe (not shown) and solid-liquid separation is performed by the filter cloth 8. The separated filtrate is extracted from a filtrate discharge hole 13 provided at the lower end of the filter beds 7, 7 of the filter plates 5, 5 and discharged into filtrate pipes 14a, 14b. The filtrate discharged into the filtrate pipes 14a, 14b is collected in a discharge pipe 15 and discharged outside the apparatus.

[0016] A pressurized fluid supply pipe 16 communicating with the diaphragm chamber 11 is connected to the filter plate 5 on which the diaphragm 10 is stretched. The pressurized fluid supply pipe 16 is branched and connected to the pressurized fluid supply holes 19 of each filter plate 5 so as to supply pressurized fluid to all of the diaphragm chambers 11, and the pressurized fluid drawn up from a water supply tank 17 by a water supply pump 18 is supplied from the pressurized fluid supply pipe 16 through the pressurized fluid supply holes 19 to each diaphragm chamber 11. The diaphragm chamber 11 to which the pressurized fluid is supplied expands toward the filtration chamber 9, and the dehydrated cake formed in the filtration chamber 9 is squeezed and dehydrated.

[0017] A pressure gauge 20 is provided in the pressure fluid supply pipe 16, and is capable of measuring in real time the pressure held in the diaphragm chamber 11 when pressure fluid is supplied to the diaphragm chamber 11. The measured value is transmitted from the pressure gauge 20 to a control device 21.

[0018] The pressure held in the expanded diaphragm chamber 11 increases, and by closing the valve V1 disposed in the pressure fluid supply pipe 16, the pressure held in the diaphragm chamber 11 can be kept constant.

[0019] The pressure fluid used in this embodiment may be a liquid (for example, water) or a gas, and is not particularly limited. When a gas is used, a known air tank or the like is provided instead of the water tank 17.

[0020] The diaphragm 10 may be stretched on both sides of the filter bed 7 constituting the filtration chamber 9, or may be stretched on only one side. When the diaphragm 10 is stretched on both sides of the filter bed 7, the dehydrated cake is squeezed from both sides, thereby further reducing the moisture content of the dehydrated cake. When the diaphragm 10 is stretched on only one side of the filter bed 7, the filter plates 5 having the diaphragms 10 stretched on both sides and the filter plates 5 having no diaphragms 10 stretched on either side may be arranged in parallel, alternately, or the filter plates 5 having the diaphragms 10 stretched on only one side may be arranged in parallel.

[0021] An air supply pipe 22 is connected to one of the filtrate pipes 14a communicating with the filtration chamber 9, and air blowing is performed by flowing air pressurized by a supply source 23 from the air supply pipe 22 through the filtrate pipe 14a into the filtration chamber 9. The air that has flowed into the filtration chamber 9 passes through the dehydrated cake and is discharged from the other filtrate pipe 14b, carrying with it the moisture in the dehydrated cake.

[0022] When air is supplied to the filtration chamber 9, the valve V2 disposed in the air supply pipe 22 is opened and the valve V3 disposed in each filtrate pipe 14a is closed, thereby preventing the air from flowing out of the discharge pipe 15 without passing through the filtration chamber 9. During the pressing / squeezing process, in order to transport the filtrate from both the filtrate pipes 14a and 14b to the discharge pipe 15, the valve V2 is closed and each valve V3 is open.

[0023] A flow meter 24 is provided in the air supply pipe 22, and measures in real time the amount of air supplied from the supply source 23 during air blowing. The measured value is sent from the flow meter 24 to the control device 21. The supply source 23 that generates high-pressure air uses a known technology such as a compressor.

[0024] As air blowing progresses, voids form in the dehydrated cake in the filtration chamber 9, reducing its volume, so that by increasing the amount of pressurized fluid supplied to the diaphragm chamber 11 during air blowing to further expand the diaphragm 10, the dehydrated cake formed in the filtration chamber 9 can be pressed against the other filter bed 7. At this time, the cake is compressed and the voids disappear, so by blowing air on the cake that has blocked the voids, it is possible to prevent short-passing of air, suppress an increase in air consumption, and efficiently remove moisture from the cake.

[0025] Therefore, in the air blowing method in this embodiment, a reference value for the air flow rate to be supplied during air blowing and a pressure boost value for boosting the diaphragm chamber 11 in stages by a predetermined pressure are set in advance in the control device 21. During the air blowing process, the air flow rate introduced from the supply source 23 is measured by the flow meter 24 and sent to the control device 21. The control device 21 compares the measured value with the reference value, and if the measured value is outside the range of the reference values, the control device 21 sends an instruction to the water supply pump 18. Based on the pressure held in the diaphragm chamber 11 measured by the pressure gauge 20, the pressure in the diaphragm chamber 11 is boosted by the boost value. The time intervals for measuring the air flow rate and the pressure held in the diaphragm chamber 11 are set appropriately. EXAMPLES

[0026] The air blowing method of the present invention will be described in detail below with reference to Figs. A reference value for the air flow rate supplied from the supply source 23 to the air supply pipe 22 during air blowing and a pressure increase value for increasing the pressure in the diaphragm chamber 11 stepwise by a predetermined pressure are set in advance in the control device 21. The filter press 1 closes the filter plates 5, 5 in advance to form the filtration chamber 9.

[0027] <Press-fitting process> First, each valve V3 is opened and valve V2 is closed. The open / close state of valve V1 is not particularly limited. Raw liquid is supplied to each filtration chamber 9 from raw liquid supply port 12, and a dehydrated cake is formed. At this time, filtrate discharged from the dehydrated cake by the injection pressure passes through filter cloth 8 and is discharged from filtrate pipes 14a, 14b via discharge hole 13. The filtrate passing through each filtrate pipe 14a, 14b is collected in discharge pipe 15 and discharged outside the machine.

[0028] <Compression process> Valve V1 is opened, and pressurized fluid drawn up from a water supply tank 17 by a water supply pump 18 is supplied from the pressurized fluid supply pipe 16 through the pressurized fluid supply hole 19 to the diaphragm chamber 11. The diaphragm chamber 11 to which the pressurized fluid is supplied expands toward the filtration chamber 9, and the dehydrated cake formed in the filtration chamber 9 is squeezed and dehydrated. The filtrate passes through the filter cloth 8 and is discharged from the filtrate pipes 14a and 14b to the discharge pipe 15.

[0029] After the squeezing time has elapsed, the valve V1 is closed to maintain a constant pressure in the diaphragm chamber 11. Alternatively, the pressure in the diaphragm chamber 11 may be maintained by continuously supplying pressurized fluid to the diaphragm chamber 11 at a constant pressure by running the water supply pump 18.

[0030] <Air blow process> The air blowing process is started with the diaphragm 10 inflated in the previous squeezing process. By opening valve V2 and closing valve V3, the pipeline is formed in one direction, from the air supply pipe 22 to the filtration chamber 9 via one filtrate pipe 14a, and from the same filtration chamber 9 to the discharge pipe 15 via the other filtrate pipe 14b.

[0031] High-pressure air is supplied from a supply source 23 to the air supply pipe 22. The air is then supplied from each filtrate pipe 14a to each filtration chamber 9 via the discharge hole 13. The air penetrates the filter cloth 8 and collides with the dehydrated cake, eliminating moisture in the dehydrated cake. The eliminated moisture, together with the air, penetrates the other filter cloth 8 and is discharged from the other discharge hole 13 that communicates with the filtrate pipe 14b.

[0032] At this time, the removed moisture creates voids in the dehydrated cake inside the filtration chamber 9, reducing the volume of the dehydrated cake. If air blowing is continued in this state, the air will short-pass the voids in the dehydrated cake, resulting in a huge amount of air consumption and making it impossible to reduce the moisture content. Therefore, in this embodiment, when the consumption of air supplied at a constant rate exceeds a specified value, it is determined that a void has occurred in the dehydrated cake, and pressurized fluid is supplied to the diaphragm chamber 11 to expand the diaphragm 10, thereby pressing against the dehydrated cake and eliminating the void.

[0033] The flow rate of air supplied from the supply source 23 to the air supply pipe 22 is measured during air blowing. As air blowing progresses, the air passes through the gaps formed in the dehydrated cake, increasing the air flow rate. The control device 21 compares the measured value with a reference value, and when the measured value increases beyond the range of the reference values, pressurized fluid is supplied to the diaphragm chamber 11 to expand the diaphragm 10.

[0034] At this time, the pressure in the diaphragm chamber 11 is increased by a predetermined pressure increase value. The pressure held in the diaphragm chamber 11 is measured by a pressure gauge 20, and based on the measured value, the control device 21 controls the water supply pump 18 to set the diaphragm chamber 11 to a desired pressure, thereby expanding the diaphragm 10.

[0035] By expanding the diaphragm 10, the gaps in the filtration chamber 9 are filled by the diaphragm 10, and the voids in the dehydrated cake are also eliminated. Air blowing is performed in this state, improving the air blowing efficiency and further reducing the moisture content. If the measured air flow rate does not exceed the standard value, air blowing continues.

[0036] By repeating the above control, the moisture content of the dehydrated cake can be reduced to any desired level. By supplying pressurized fluid to the diaphragm chamber 11 in sequence during air blowing, the diaphragm 10 can be expanded in stages, and sudden pressure is not applied to the dehydrated cake. This prevents cracks from occurring in the dehydrated cake, and allows the cake to be compressed uniformly. By compressing the dehydrated cake in sequence, short-passing of air can be prevented, and air consumption can be reduced.

[0037] In this embodiment, the reference value and the boost value are set to fixed values ​​that are initially set, but variable values ​​that vary with time or the maintained pressure may also be used.

[0038] The amount of air supplied may be increased each time the holding pressure of the diaphragm chamber 11 is increased. Since the dehydrated cake, which has become stronger due to the expansion of the diaphragm 10, has a large resistance when air is blown, if the amount of air supplied to the filtration chamber 9 is increased by a specified amount when the holding pressure of the diaphragm chamber 11 is increased by the increased pressure value, more water can be removed from the dehydrated cake and voids will not occur in the dehydrated cake. In addition, since the amount of air supplied is not increased abruptly, cracks will not occur in the dehydrated cake.

[0039] In this embodiment, whether or not voids have occurred in the dehydrated cake is judged by measuring the amount of air supplied to the filtration chamber 9, but a reference value for increasing the pressure in the diaphragm chamber 11 may be set based on any of the flow rate of air discharged from the filtration chamber 9, the pressure of air supplied to the filtration chamber 9, the flow rate of filtrate discharged from the filtration chamber 9, the elapsed time from the start of air blowing, etc., or a combination of multiple reference values. In this case, a known measuring device, etc. is used.

[0040] When the dehydrated cake in the filtration chamber 9 reaches a predetermined moisture content, the air blowing process is terminated. Alternatively, only the control of the holding pressure in the diaphragm chamber 11 is terminated, and air blowing is continued until a desired moisture content is reached. Note that each control may be terminated based on the flow rate of the filtrate discharged from the filtration chamber 9, the elapsed time from the start of the air blowing process, etc., in addition to the moisture content of the dehydrated cake. [Industrial Applicability]

[0041] The air blowing method for the filter press according to the present invention can reduce the moisture content of the dehydrated cake while reducing the amount of air consumed by expanding the diaphragm while supplying air to the filtering chamber. This can be done without additional equipment if the filter plate is equipped with a diaphragm, and highly efficient air blowing can be performed by setting each value according to the sludge properties, making this a very useful technology for various production processes such as drinking water / industrial water sludge treatment, chemical industry, and paper / pulp industry. [Explanation of symbols]

[0042] 5 Filter plate 9. Filtration Room 10 Diaphragm 11 Diaphragm chamber

Claims

1. In a method for blowing air in a filter press, a raw liquid is supplied to a filtering chamber (9) formed of a plurality of filter plates (5), and the raw liquid is compressed and dehydrated by a diaphragm (10) attached to the filtering chamber (9), and air is introduced into the filtering chamber (9) to blow air therein, A reference value for increasing the pressure in the diaphragm chamber (11) is set in advance from at least one of the flow rate of air supplied to the filtration chamber (9), the flow rate of air discharged from the filtration chamber (9), and the pressure of the air supplied to the filtration chamber (9), and a pressure increase value for increasing the pressure in the diaphragm chamber (11) in stages by a predetermined pressure is set; During the air blow process, the measured value is compared with the reference value. If the measured value is within the standard range, the air blow process is continued under the same conditions. If the measured value is outside the range of the reference value, the pressure held in the diaphragm chamber (11) is increased by the boost value and the air blow process is continued. A method for blowing air into a filter press.

2. When the pressure held in the diaphragm chamber (11) is increased by the pressure increase value, the amount of air supplied to the filtration chamber (9) is increased by a specified amount. The method for blowing air into a filter press according to claim 1.

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