WO2006137502A1 - Method and apparatus for dehydrating and drying slurry - Google Patents

Method and apparatus for dehydrating and drying slurry Download PDF

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Publication number
WO2006137502A1
WO2006137502A1 PCT/JP2006/312556 JP2006312556W WO2006137502A1 WO 2006137502 A1 WO2006137502 A1 WO 2006137502A1 JP 2006312556 W JP2006312556 W JP 2006312556W WO 2006137502 A1 WO2006137502 A1 WO 2006137502A1
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WO
WIPO (PCT)
Prior art keywords
slurry
filter
heating medium
temperature
chamber
Prior art date
Application number
PCT/JP2006/312556
Other languages
English (en)
French (fr)
Inventor
Junichi Nomura
Shoichi Goda
Norio Yamada
Hiromi Takayasu
Kanroku Chonan
Michinari Itayama
Original Assignee
Ebara Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ebara Corporation filed Critical Ebara Corporation
Priority to JP2007558253A priority Critical patent/JP5478019B2/ja
Publication of WO2006137502A1 publication Critical patent/WO2006137502A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B5/00—Drying solid materials or objects by processes not involving the application of heat
    • F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
    • F26B5/042—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum for drying articles or discrete batches of material in a continuous or semi-continuous operation, e.g. with locks or other air tight arrangements for charging/discharging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
    • B01D25/12—Filter presses, i.e. of the plate or plate and frame type
    • B01D25/164—Chamber-plate presses, i.e. the sides of the filtering elements being clamped between two successive filtering plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
    • B01D25/28—Leaching or washing filter cakes in the filter handling the filter cake for purposes other than regenerating
    • B01D25/282—Leaching or washing filter cakes in the filter handling the filter cake for purposes other than regenerating for drying
    • B01D25/284—Leaching or washing filter cakes in the filter handling the filter cake for purposes other than regenerating for drying by gases or by heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D25/00—Filters formed by clamping together several filtering elements or parts of such elements
    • B01D25/28—Leaching or washing filter cakes in the filter handling the filter cake for purposes other than regenerating
    • B01D25/282—Leaching or washing filter cakes in the filter handling the filter cake for purposes other than regenerating for drying
    • B01D25/285—Leaching or washing filter cakes in the filter handling the filter cake for purposes other than regenerating for drying by compression using inflatable membranes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/008—Control or steering systems not provided for elsewhere in subclass C02F
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
    • C02F11/122—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering using filter presses
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F11/00—Treatment of sludge; Devices therefor
    • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
    • C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B7/00—Drying solid materials or objects by processes using a combination of processes not covered by a single one of groups F26B3/00 and F26B5/00
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/02—Temperature
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/44—Time
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/06—Pressure conditions
    • C02F2301/063—Underpressure, vacuum
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/06—Pressure conditions
    • C02F2301/066—Overpressure, high pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
    • F26B2200/18—Sludges, e.g. sewage, waste, industrial processes, cooling towers

Definitions

  • the present invention relates to a method and apparatus for dehydrating and drying slurry, and more particularly to a method and apparatus for dehydrating and drying slurry such as sludge discharged from a water supply and drainage system, a waste water treatment system in a rural village, a human waste treatment system, an industrial waste water treatment system, and the like.
  • a dehydrating apparatus and a drying apparatus are required to be separately provided, so that initial cost and labor of maintenance are greatly increased.
  • a dehydrating and drying apparatus having a filter press (pressure dehydrator).
  • a filter press pressure dehydrator
  • slurry in a filter chamber of a filter press is pressed while being heated by a heating medium.
  • the interior of the filter press is evacuated by a vacuum pump to dehydrate and dry the slurry.
  • the dehydrated and dried slurry is discharged as a cake from the filter press.
  • a conventional dehydrating and drying apparatus has an insufficient evaporation rate for organic sludge. Accordingly, the size of the apparatus is problematically increased. Further, if ease of separation of a cake from a filter cloth is deteriorated, much labor is required to maintain the dehydrating and drying apparatus. Furthermore, it disadvantageously takes much time to reduce a pressure in the filter press to a predetermined degree of vacuum after the vacuum pump is operated.
  • the present invention has been made in view of the above drawbacks. It is, therefore, an object of the present invention to provide a method and apparatus for dehydrating and drying slurry which can dehydrate and dry slurry efficiently in a short period of time and can improve ease of separation of a cake.
  • a method of dehydrating and drying slurry which can dehydrate and dry slurry efficiently in a short period of time and can improve ease of separation of a cake.
  • a first filter plate and a second filter plate are disposed so as to form a filter chamber between the first filter plate and the second filter plate.
  • the first filter plate has a filter cloth, a diaphragm, and a heating medium chamber formed therein.
  • the second filter plate has a filter cloth, a heat transfer member made of metal, and a heating medium chamber formed therein. Slurry is supplied to the filter chamber. The slurry is filtered in the filter chamber through the filter cloths of the first filter plate and the second filter plate.
  • the slurry is pressed in the filter chamber against the diaphragm of the first filter plate by supplying a heating medium to the heating medium chamber of the first filter plate. Heat of a heating medium is transferred to the slurry through the heat transfer member of the second filter plate by supplying the heating medium to the heating medium chamber of the second filter plate.
  • the slurry is heated to a preset temperature higher than a predetermined saturated vapor temperature.
  • the slurry is introduced to an atmosphere having a pressure corresponding to the predetermined saturated vapor temperature after the heating process of the slurry so that a temperature difference between the preset temperature and the predetermined saturated vapor temperature causes self-evaporation of water in the slurry.
  • the slurry may be heated during the filtering process of the slurry or during the pressing process of the slurry.
  • the self-evaporation of water in the slurry may be repeated a plurality of times.
  • a method of dehydrating and drying slurry which can dehydrate and dry slurry efficiently in a short period of time and can improve ease of separation of a cake.
  • filter plates are disposed so as to form a filter chamber between the filter plates.
  • Each of the filter plates has a filter cloth, a heat transfer member made of metal, and a heating medium chamber formed therein.
  • Slurry is supplied to the filter chamber.
  • the slurry is filtered in the filter chamber through the filter cloths of the filter plates.
  • Heat of a heating medium is transferred to the slurry through the heat transfer members of the filter plates by supplying the heating medium to the heating medium chambers of the filter plates.
  • the slurry is heated to a preset temperature higher than a predetermined saturated vapor temperature.
  • the slurry is introduced to an atmosphere having a pressure corresponding to the predetermined saturated vapor temperature after the heating process of the slurry so that a temperature difference between the preset temperature and the predetermined saturated vapor temperature causes self-evaporation of water in the slurry.
  • the slurry may be heated during the filtering process of the slurry or after the filtering process of the slurry.
  • the self-evaporation of water in the slurry may be repeated a plurality of times.
  • dehydrating used in the specification includes dehydration by filtration and dehydration by pressing.
  • a compressed gas may be passed through the filter chamber during the filtering process of the slurry, during the pressing s process of the slurry, after the filtering process of the slurry, after the pressing process of the slurry, during the self-evaporation of water in the slurry, or after the self-evaporation of water in the slurry.
  • the self-evaporation of water in the slurry may be repeated a plurality of times, and the ventilation of the compressed gas may be performed after at least one of the self-evaporations of water in the slurry.
  • At least one of stem, air, dehumidified air, and hot discharge gas may be used as the compressed gas.
  • the compressed gas may be supplied to the filter chamber through a blow line for blowing the compressed gas into the filter chamber, and discharged from the filter chamber through a filtrate discharge line for discharging a filtrate from the filter chamber.
  • the compressed gas may be supplied to the filter chamber through one of a plurality of filtrate discharge lines for discharging a filtrate from the filter chamber, and discharged from the filter chamber through another of the plurality of filtrate discharge lines.
  • the self-evaporation of water in the slurry may be repeated a plurality of times by connecting the filter chamber sequentially to a plurality of vacuum tanks.
  • Each of the vacuum tanks is held at a pressure equal to or lower than the pressure corresponding to the predetermined saturated vapor temperature. In such a case, drying can efficiently be completed in a shorter period of time, and the interior of the filter press can instantaneously be introduced into a vacuum atmosphere.
  • a physical property value reflecting a temperature of the slurry in the filter chamber may be measured to control start and stop of the self-evaporation of water in the slurry based on the measured physical property value. It is desirable to repeat the self-evaporation of water in the slurry.
  • the physical property value may be a temperature of the slurry in the filter chamber and a temperature difference between an inlet temperature of the heating medium chamber and an outlet temperature of the heating medium chamber.
  • the self-evaporation of water in the slurry may be started when the measured temperature of the slurry in the filter chamber is higher than a predetermined value.
  • the self-evaporation of water in the slurry may be stopped when the measured temperature difference between the inlet temperature of the heating medium chamber and the outlet temperature of the heating medium chamber is equal to a predetermined value.
  • the physical property value may be a temperature difference between an inlet temperature of the heating medium chamber and an outlet temperature of the heating medium chamber.
  • the self-evaporation of water in the slurry may be started and stopped when the measured temperature difference between the inlet temperature of the heating medium chamber and the outlet temperature of the heating medium chamber is equal to a predetermined value.
  • the physical property value may be a temperature difference between an inlet temperature of the heating medium chamber and an outlet temperature of the heating medium chamber.
  • the self-evaporation of water in the slurry may be started when the measured temperature difference between the inlet temperature of the heating medium chamber and the outlet temperature of the heating medium chamber is equal to a predetermined value.
  • the self-evaporation of water in the slurry is stopped a predetermined period of time after the starting the self-evaporation of water in the slurry.
  • the physical property value may be a temperature of a filtrate discharged from the filter chamber and a temperature difference between an inlet temperature of the heating medium chamber and an outlet temperature of the heating medium chamber.
  • the self-evaporation of water in the slurry may be started when the measured temperature of the filtrate discharged from the filter chamber is higher than a predetermined value.
  • the self-evaporation of water in the slurry may be stopped a predetermined period of time after the starting the self-evaporation of water in the slurry or when the measured temperature difference between the inlet temperature of the heating medium chamber and the outlet temperature of the heating medium chamber is equal to a predetermined value.
  • the physical property value may be a temperature of the slurry in the filter chamber.
  • the self-evaporation of water in the slurry is started when the measured temperature of the slurry in the filter chamber is higher than a predetermined value.
  • the self-evaporation of water in the slurry is stopped a predetermined period of time after the starting the self-evaporation of water in the slurry.
  • the self-evaporation of water in the slurry may be repeated a plurality of times at a predetermined frequency.
  • the difference between the preset temperature and the predetermined saturated vapor temperature is in a range of from 20°C to 70°C.
  • the pressure corresponding to the predetermined saturated vapor temperature is not more than an absolute pressure of 0.03 MPa.
  • an apparatus for dehydrating and drying slurry which can dehydrate and dry slurry efficiently in a short period of time and can improve ease of separation of a cake.
  • the apparatus has a filter press having a first filter plate, a second filter plate, and at least one filter chamber formed between the first filter plate and the second filter plate.
  • the first filter plate has a diaphragm, a filter cloth disposed between the diaphragm and the filter chamber, and a heating medium chamber for pressing the diaphragm to the filter chamber by a supplied heating medium.
  • the second filter plate has a heat transfer member made of metal with a heat transfer surface, a filter cloth disposed between the heat transfer surface of the heat transfer member and the filter chamber, and a heating medium chamber for transferring heat of a supplied heating medium to the slurry through the heat transfer surface.
  • the apparatus includes a heating mechanism operable to heat the slurry to a preset temperature higher than a predetermined saturated vapor temperature.
  • the apparatus also includes a decompressing mechanism operable to instantaneously introduce the slurry heated by the heating mechanism to an atmosphere having a pressure corresponding to the predetermined saturated vapor temperature.
  • the second filter plate may have a body made of resin disposed at a peripheral portion of the heat transfer surface of the heat transfer member.
  • the body may be formed integrally with the heat transfer member of the second filter plate.
  • an apparatus for dehydrating and drying slurry which can dehydrate and dry slurry efficiently in a short period of time and can improve ease of separation of a cake.
  • the apparatus has a filter press having filter plates and at least one filter chamber formed between the filter plates.
  • Each of the filter plate has a heat transfer member made of metal with a heat transfer surface, a filter cloth disposed between the heat transfer surface of the heat transfer member and the filter chamber, and a heating medium chamber for transferring heat of a supplied heating medium to the slurry through the heat transfer surface.
  • the apparatus includes a heating mechanism operable to heat the slurry to a preset temperature higher than a predetermined saturated vapor temperature.
  • the apparatus also includes a decompressing mechanism operable to instantaneously introduce the slurry heated by the heating mechanism to an atmosphere having a pressure corresponding to the predetermined saturated vapor temperature.
  • Each of the filter plates may have a body made of resin disposed at a peripheral portion of the heat transfer surface of the heat transfer member. The body may be formed integrally with the heat transfer member of the filter plate.
  • the apparatus may include a ventilation mechanism operable to allow a compressed gas to pass through the filter chamber. At least one of stem, air, dehumidified air, and hot discharge gas may be used as the compressed gas.
  • the ventilation mechanism may be configured to supply the compressed gas to the filter chamber through a blow line for blowing the compressed gas into the filter chamber and to discharge the compressed gas from the filter chamber through a filtrate discharge line for discharging a filtrate from the filter chamber.
  • the ventilation mechanism may be configured to supply the compressed gas to the filter chamber through one of a plurality of filtrate discharge lines for discharging a filtrate from the filter chamber and to discharge the compressed gas from the filter chamber through another of the plurality of filtrate discharge lines.
  • the ventilation mechanism may include a plurality of vacuum tanks connected in parallel to the filter chamber of the filter press. Each of the plurality of vacuum tanks may be held at a pressure equal to or lower than the pressure corresponding to the predetermined saturated vapor temperature.
  • the ventilation mechanism may include a plurality of valves operable to switch connections between the plurality of vacuum tanks and the filter chamber of the filter press.
  • the plurality of vacuum tanks may have a cooling mechanism.
  • the apparatus may include at least one sensor for measuring a physical property value reflecting a temperature of the slurry in the filter chamber.
  • the decompressing mechanism may be controlled based on the physical property value measured by the at least one sensor.
  • the at least one sensor may include a sensor for measuring a temperature of the slurry in the filter chamber.
  • the at least one sensor may include a first sensor for measuring an inlet temperature of the heating medium chamber and a second sensor for measuring an outlet temperature of the heating medium chamber.
  • the at least one sensor may include a sensor for measuring a temperature of a filtrate discharged from the filter chamber.
  • the difference between the preset temperature and the predetermined saturated vapor temperature is in a range of from 2O 0 C to 70 0 C.
  • the pressure corresponding to the predetermined saturated vapor temperature is not more than an absolute pressure of 0.03 MPa.
  • slurry is introduced into a decompressed atmosphere after the slurry is heated. Irrespective of types of slurry, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. Accordingly, a cake is cracked so as to increase an evaporation area. Thus, it is possible to efficiently dehydrate and dry the slurry in a short period of time.
  • the filter chamber is connected sequentially to a plurality of vacuum tanks held at a pressure lower than the pressure corresponding to the predetermined saturated vapor temperature. Therefore, the interior of the filter press can immediately be introduced into an atmosphere having a desired pressure. It is possible to reduce the volume of a cooling mechanism or a vacuum pump and operate the dehydrating and drying apparatus efficiently.
  • FIG. 1 is a schematic view showing a dehydrating and drying apparatus according to a first embodiment of the present invention
  • FIG. 2 is a cross- sectional view schematically showing a filter press in the dehydrating and drying apparatus shown in FIG. 1;
  • FIG. 3 is a side view showing a first filter plate in the filter press shown in FIG. 2;
  • FIG. 4A is a cross-sectional view taken along line A-A of FIG. 3;
  • FIG. 4B is a cross-sectional view taken along line B-B of FIG. 3;
  • FIGS. 5A and 5B are cross-sectional views showing a second filter plate in the filter press shown in FIG. 2;
  • FIG. 6 is a cross-sectional view showing a main portion of a filter press according to a second embodiment of the present invention.
  • FIGS. 7A and 7B are cross-sectional views showing a second filter plate included in the filter press shown in FIG. 6;
  • FIGS. 8A and 8B are cross-sectional views showing a filter plate according to a third embodiment of the present invention.
  • FIG. 8C is a partial enlarged view of FIG. 8B;
  • FIG. 9 is a cross-sectional view showing a main portion of a filter press according to a fourth embodiment of the present invention.
  • FIG. 10 is a cross-sectional view showing a main portion of a filter press according to a fifth embodiment of the present invention.
  • FIG. 11 is a cross-sectional view showing a main portion of a filter press according to a sixth embodiment of the present invention.
  • FIG. 12 is a schematic view showing a dehydrating and drying apparatus according to a seventh embodiment of the present invention.
  • FIG. 13 is a schematic view showing a dehydrating and drying apparatus according to an eighth embodiment of the present invention.
  • FIGS. 1 through 13 A dehydrating and drying apparatus according to embodiments of the present invention will be described below with reference to FIGS. 1 through 13. Like or corresponding parts are denoted by like or corresponding reference numerals in FIGS. 1 through 13, and will not be described below repetitively.
  • FIG. 1 is a schematic view showing a dehydrating and drying apparatus according to a first embodiment of the present invention.
  • the dehydrating and drying apparatus has a filter press 1 for dehydrating and drying slurry such as sludge.
  • the dehydrating and drying apparatus also has a slurry supply line 10 for supplying slurry into filter chambers formed in the filter press 1, a heating medium circulation line 20 for circulating a heating medium (e.g., hot water) through the filter press 1, a vacuum line 30 for evacuating the filter chambers in the filter press 1, a blow line 40 for blowing compressed air into the filter chambers in the filter press 1, and a slurry discharge line 50 for discharging remaining slurry from the filter press 1.
  • a heating medium circulation line 20 for circulating a heating medium (e.g., hot water) through the filter press
  • a vacuum line 30 for evacuating the filter chambers in the filter press
  • a blow line 40 for blowing compressed air into the filter chambers in the filter press 1
  • the slurry supply line 10, the heating medium circulation line 20, the vacuum line 30, the blow line 40, and the slurry discharge line 50 are connected to the filter press 1.
  • the filter press 1 includes a filter chamber temperature sensor 2 for detecting a temperature of the filter chambers and a relief valve 3 for discharging a gas accumulated in the heating medium circulation line 20 from the filter press 1.
  • a slurry supply pump 11 is connected to an end of the slurry supply line 10.
  • the slurry supply pump 11 serves to supply slurry through the slurry supply line 10 into the filter chambers in the filter press 1.
  • the slurry supply line 10 has a slurry supply valve 12 for controlling supply of the slurry to the filter press 1 and a slurry pressure sensor 14 for detecting a pressure of the slurry in the slurry supply line 10.
  • the heating medium circulation line 20 includes a heating medium circulation line 2OA upstream of the filter press 1 and a heating medium circulation line 2OB downstream of the filter press 1.
  • the heating medium circulation line 2OA has a heating medium circulation pump 21 for circulating the heating medium in the heating medium circulation line 20 and a first heating medium temperature sensor 22 for detecting a temperature of the heating medium at an inlet of the filter press 1.
  • the heating medium circulation line 2OB has a second heating medium temperature sensor 23 for detecting a temperature of the heating medium at an outlet of the filter press 1, a heating medium pressure sensor 24 for detecting a pressure of the heating medium at the outlet of the filter press 1, and a back-pressure valve 25 for regulating a pressure of the heating medium flowing through the heating medium circulation line 2OB.
  • the pressure of the heating medium to be supplied to the filter press 1 can be adjusted by operating the back-pressure valve 25.
  • the heating medium circulation line 2OA disposed upstream of the filter press 1 and the heating medium circulation line 2OB disposed downstream of the filter press 1 are connected to a heating tank 26 for heating the heating medium circulated in the heating medium circulation line 20.
  • the heating medium is heated by the heating tank 26 and supplied through the heating medium circulation line 2OA into the filter press 1 so as to at least heat slurry in the filter chambers of the filter press 1.
  • the heating medium flows out of the filter press 1 and returns through the heating medium circulation line 2OB to the heating tank 26.
  • the heating medium circulation lines 2OA and 2OB, the heating medium circulation pump 21, and the heating tank 26 form a heating mechanism for heating the slurry in the filter chambers of the filter press 1.
  • the slurry is heated in the filter chambers of the filter press 1 by the heating medium circulated in the heating medium circulation line 20 while the slurry is pressed in the filter chambers of the filter press 1.
  • the filter press 1 in the present embodiment is formed as a horizontal pressure dehydrating and drying device.
  • a vacuum pump 31 is connected to an end of the vacuum line 30.
  • the vacuum pump 31 serves to evacuate the filter chambers in the filter press 1 through the vacuum line 30.
  • the vacuum line 30 has a first selector valve (control valve) 32 A, a condenser 33 for condensing steam introduced from the filter press 1, and a vacuum tank 34.
  • the vacuum line 30, the vacuum pump 31, the first selector valve 32A, and the vacuum tank 34 form a decompressing mechanism for decompressing the slurry in the filter chambers of the filter press 1.
  • a coolant is supplied to the condenser 33. Heat is exchanged between steam introduced from the filter press 1 into the condenser 33 and the coolant in the condenser 33. Thus, the steam is condensed and then discharged as a condensate from the condenser 33.
  • a filtrate discharge line 35 is connected to the vacuum line 30.
  • the filtrate discharge line 35 serves to discharge a filtrate from the filter chambers in the filter press 1 during dehydration of the slurry.
  • the filtrate discharge line 35 has a second selector valve (control valve) 32B.
  • control valve control valve
  • the first selector valve 32A is opened while the second selector valve 32B is closed.
  • the second selector valve 32B is opened while the first selector valve 32A is closed.
  • the pressure of the filter chambers in the filter press 1 can be increased immediately from vacuum to an atmospheric pressure by opening the second selector valve 32B.
  • a compressor (not shown) is connected to the blow line 40 for generating compressed air.
  • compressed air is blown from the compressor through the blow line 40 into the filter chambers so that slurry remaining within the filter press 1 and slurry remaining at a slurry supply port of the filter chambers are discharged through the slurry discharge line 50 by the compressed air.
  • the blow line 40 has an air valve 41, and the slurry discharge line 50 has a slurry discharge valve 51.
  • FIG. 2 is a cross-sectional view schematically showing the filter press 1 shown in FIG. 1.
  • the filter press 1 includes first filter plates 100, second filter plates 110, and a pair of clamping plates 120A and 120B for clamping the filter plates 100 and 110 from both sides thereof.
  • the first filter plates 100 and the second filter plates 110 are alternately disposed so as to form filter chambers 130 between the first filter plates 100 and the second filter plates 110.
  • the first filter plates 100 and the second filter plates 110 are disposed on both sides of each filter chamber 130 so as to face each other.
  • a slurry supply pipe 121 is attached to a central portion of the clamping plate 120A and connected to the slurry supply line 10 (see FIG. 1).
  • a slurry discharge pipe 122 is attached to a central portion of the clamping plate 120B and connected to the slurry discharge line 50 (see FIG. 1).
  • the aforementioned filter chamber temperature sensor 2 is disposed near the clamping plate 120A. The temperature of the slurry in the filter chambers 130 is detected by the filter chamber temperature sensor 2.
  • a thermocouple can suitably be used as the filter chamber temperature sensor 2.
  • each of the first filter plates 100 has a body 101 made of resin, a diaphragm 102, and a filter cloth 103 disposed between the diaphragm 102 and the filter chambers 130.
  • Each of the second filter plates 110 has a body 111 made of resin, a heat transfer member 112 made of metal, and a filter cloth 113 disposed between the heat transfer member 112 and the filter chambers 130.
  • the filter press 1 employs two types of filter plates including the first filter plate 100 having the diaphragm 102 and the second filter plate 110 having the heat transfer member 112 made of metal. Accordingly, the filter press 1 serves as a single-side pressing device.
  • FIG. 3 is a side view showing the first filter plate 100 from which the filter cloth 103 is removed.
  • FIG. 4A is a cross-sectional view taken along line A-A of FIG. 3
  • FIG. 4B is a cross-sectional view taken along line B-B of FIG. 3.
  • the first filter plate 100 has an opening 104 formed at a central portion of the first filter plate 100 so as to correspond to the aforementioned slurry supply pipe 121.
  • the opening 104 extends through the body 101, the diaphragm 102, and the filter cloth 103.
  • Adjacent filter chambers 130 communicate with each other by the opening 104.
  • the diaphragm 102 has a plurality of projections 105 provided on a surface of the diaphragm 102 facing the filter cloth 103.
  • the projections 105 form a fine filtrate chamber Sl between the diaphragm 102 and the filter cloth 103.
  • the body 101 has filtrate discharge passages 106 communicating with the filtrate chamber Sl.
  • the filtrate chamber Sl between the diaphragm 102 and the filter cloth 103 is connected through the filtrate discharge passages 106 to the vacuum line 30 (see FIG. 1). Accordingly, vacuum can be formed in the filtrate chamber Sl by the vacuum pump 31. Water of the slurry passes through the filter cloth 103 into the filtrate chamber Sl and flows through the filtrate discharge passages 106 into the filtrate discharge line 35 (see FIG. 1).
  • the body 101 has recesses 107 formed in surfaces thereof. Each of the recesses 107 forms a heating medium chamber S2 between the body 101 and the diaphragm 102 covering substantially the entire surface of the body 101. Further, as shown in FIG. 4 A, the body 101 has heating medium supply passages 108 communicating with the heating medium chambers S2 and heating medium discharge passages 109 communicating with the heating medium chambers S2. The heating medium chambers S2 between the diaphragm 102 and the body 101 are connected through the heating medium supply passages 108 to the heating medium circulation line 2OA (see FIG. 1). Thus, the heating medium is supplied from the heating medium circulation line 2OA through the heating medium supply passages 108 to the heating medium chambers S2.
  • the heating medium chambers S2 are connected through the heating medium discharge passages 109 to the heating medium circulation line 2OB (see FIG. 1).
  • the heating medium supplied to the heating medium chambers S2 is discharged through the heating medium discharge passages 109 into the heating medium circulation line 2OB.
  • FIGS. 5 A and 5B are cross- sectional views of the second filter plate 110.
  • FIG. 5 A is a cross-section on the same plane as that of FIG. 4A
  • FIG. 5B is a cross-section on the same plane as that of FIG. 4B.
  • the second filter plate 110 has an opening 114 formed at a central portion of the second filter plate 110 so as to correspond to the aforementioned slurry supply pipe 121, as with the first filter plate 100.
  • the opening 114 extends through the body 111, the heat transfer member 112, and the filter cloth 113. Adjacent filter chambers 130 communicate with each other by the opening 114.
  • the heat transfer member 112 has a plurality of projections 115 provided on a surface of the heat transfer member 112 facing the filter cloth 113.
  • the projections 115 form a fine filtrate chamber SIl between the heat transfer member 112 and the filter cloth 113.
  • the body 111 has filtrate discharge passages 116 formed so as to communicate with the filtrate chamber SIl.
  • the filtrate chamber SI l between the heat transfer member 112 and the filter cloth 113 is connected through the filtrate discharge passages 116 to the vacuum line 30 (see FIG. 1). Accordingly, vacuum can be formed in the filtrate chamber SI l by the vacuum pump 31.
  • a support member (not shown) may be provided between portions of the heat transfer member 112 so as to bypass the heating medium.
  • the heat transfer member 112 made of metal has a hollow portion (heating medium chamber) S 1-2 formed therein.
  • the body 111 made of resin is disposed at a peripheral portion of the heating medium chamber S12. As shown in FIG. 5A, the body 111 has a heating medium supply passage 118 communicating with the heating medium chamber S 12 and a heating medium discharge passage 119 communicating with the heating medium chamber S 12.
  • the heating medium chamber S12 in the heat transfer member 112 is connected through the heating medium supply passage 118 to the heating medium circulation line 20 A (see FIG. 1).
  • the heating medium is supplied from the heating medium circulation line 2OA through the heating medium supply passage 118 to the heating medium chamber S 12.
  • the heating medium chamber S 12 is connected through the heating medium discharge passage 119 to the heating medium circulation line 2OB (see FIG. 1).
  • the heating medium supplied to the heating medium chamber S12 is discharged through the heating medium discharge passage 119 into the heating medium circulation line 2OB.
  • the first filter plates 100 and the second filter plates 110 are disposed alternately in parallel so as to form a plurality of filter chambers 130 between the filter cloths 103 of the first filter plates 100 and the filter cloths 113 of the second filter plates 110. These filter plates 100 and 110 are configured to move close to and away from each other.
  • the clamping plate 120A and the clamping plate 120B are fastened to each other by a fastening device (not shown) to fix the filter plates 100 and 110.
  • the slurry is supplied through the slurry supply line 10 (see FIG. 1), the slurry supply pipe 121, and the openings 104 and 114 of the first filter plates 100 and the second filter plates 110 into the filter chambers 130. .
  • the dehydrating and drying process of slurry in this example includes a dehydrating process to dehydrate slurry by filtration and pressing of the slurry, a drying process to dry the dehydrated slurry, and a blowing process to blow the dehydrated or dried slurry.
  • slurry is supplied to the filter press 1 through the slurry supply line 10, the slurry supply valve 12, and the slurry pressure sensor 14 by the slurry supply pump 11 and is thus filled in the filter chambers 130.
  • water of the slurry is converted into a filtration filtrate and discharged through the filtrate discharge passages 106 and 116 and the filtrate discharge line 35 from the filtrate chambers Sl and SI l.
  • the supply pressure of the slurry is set at, for example, a low absolute pressure of 0.15 MPa to 0.20 MPa at the beginning of the filtration.
  • the supply pressure of the slurry may be increased gradually according to the progress of the filtration. Then, eventually, the supply pressure of the slurry may be set at an absolute pressure of at least 0.6 MPa. It is desirable that the period of time of the filtration is selected optimally depending on properties of the slurry.
  • the slurry may be heated before being supplied to the filter press 1 (preliminary heating filtration). In this case, since the heated slurry is supplied to the filter press 1, the filterability of the slurry can be improved. Further, a heating medium heated in the heating tank 26 may be circulated in the heating medium circulation lines 2OA and 2OB by the heating medium circulation pump 21 and supplied into the heating medium chambers S2 and S 12 in the filter press 1 to heat the slurry during the filtration (heating filtration). In this case, since the slurry is filtered while being heated, the filterability of the slurry can be improved. (2) Pressing Step
  • a heating medium heated by the heating tank 26 is supplied through the heating medium circulation line 2OA to the heating medium chambers S2 and S 12 in the filter press 1 by the heating medium circulation pump 21.
  • the heating medium is returned to the heating tank 26 through the heating medium circulation line 2OB, the second heating medium temperature sensor 23, and the heating medium pressure sensor 24.
  • the heating medium is heated by the heating tank 26 and supplied again to the heating medium chambers S2 and S 12 in the filter press 1 through the heating medium circulation line 2OA.
  • the pressure (pressing pressure) of the heating medium in the heating medium chambers S2 is controlled at a predetermined value by the back-pressure valve 25, which is provided in the heating medium circulation line 2OB.
  • the diaphragms 102 of the first filter plates 100 are swelled toward the filter chambers 130 to thereby press and heat the slurry in the filter chambers 130.
  • Water in the slurry flows as a pressing filtrate out of the filtrate chambers Sl and SI l.
  • the pressing filtrate is discharged through the filtrate discharge passages 106 and 116 to the filtrate discharge line 35.
  • the slurry When the slurry is filtered and pressed in the above manner, the slurry is dehydrated and gradually converted into a cake. In the dehydrating process, only filtration step may be conducted without the pressing step to dehydrate the slurry.
  • the relief valve 3 At the beginning of the pressing step, the relief valve 3 (see FIG. 1) may temporarily be opened to discharge an accumulated gas in the heating medium chambers S2 and S 12.
  • the pressing pressure of the slurry is adjustable in a range of from an absolute pressure of 0.1 MPa (atmospheric pressure) to an absolute pressure of 1.6 MPa. It is desirable to increase the pressing pressure gradually to a pressure between the supply pressure of the slurry and 1.6 MPa after starting of the pressing step.
  • the temperature of the heating medium should be equal to or more than a saturated vapor temperature corresponding to a vacuum pressure, it is not limited to a specific value.
  • the heating medium should preferably have a temperature of at least 70°C.
  • the slurry is heated to a preset temperature higher than a predetermined saturated vapor temperature (a saturated vapor temperature corresponding to a vacuum pressure).
  • a heating medium is circulated through the filter press 1. It is desirable that the pressure of the heating medium is adjusted to be lower than the pressing pressure in the pressing step by the back-pressure valve 25.
  • the first selector valve 32A is opened to evacuate the filtrate chambers Sl and SI l in the filter press 1 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31.
  • the vacuum pump 31 may be operated to decompress the interior of the vacuum tank 34 in advance.
  • the filtrate chambers Sl and SI l can instantaneously be decompressed to a vacuum by opening the first selector valve 32A at the beginning of the drying process.
  • the slurry is sufficiently heated in the filter chambers 130 by the heating medium.
  • a large difference is produced between the preset temperature of the slurry and the saturated vapor temperature corresponding to the vacuum pressure. Accordingly, when the slurry in the filter press 1 is instantaneously introduced to an atmosphere under a vacuum pressure in the drying process, thermal energy of the slurry is used for evaporation in addition to heat supplied by the heating medium. As a result, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. The bumping increases a drying rate (evaporation rate) of the slurry.
  • the efficiency of the vacuum pump 31 can be increased by supplying a coolant to the condenser 33 so that steam produced from the slurry (cake) in the filter chambers 130 is converted into water. It is desirable that the vacuum pressure in the drying process is not more than an absolute pressure of 0.03 MPa.
  • the preset temperature is at least 100°C, which is a saturated vapor temperature of the atmospheric pressure
  • the first selector valve 32A may be left closed after the starting of the drying process, and the second selector valve 32B may be opened so that the steam produced from the slurry is discharged through the filtrate discharge line 35, not through the vacuum line 30.
  • the slurry is sufficiently heated in the filter chambers 130 during the pressing step, and a large difference is produced between the preset temperature of the slurry and a saturated vapor temperature corresponding to an atmospheric pressure. Accordingly, thermal energy of the slurry is used for evaporation to accelerate self-evaporation of water contained in the slurry. Therefore, bumping can be caused to increase a drying rate of the slurry.
  • the heating medium is also circulated at a pressure lower than the pressing pressure.
  • the first selector valve 32A is opened to evacuate the filtrate chambers Sl and SIl in the filter press 1 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31. After the temperature of the cake in the filter chambers 130 is decreased to a temperature lower than the temperature of the heating medium by a predetermined value, the first selector valve 32A is closed. Then, after the temperature of the cake in the filter chambers 130 is increased to a predetermined temperature, the first selector valve 32A is opened again to evacuate the filtrate chambers Sl and SI l by the vacuum pump 31. Such operation is repeated a predetermined number of times.
  • a blowing process may be performed at desired timing (e.g., after completion of the pressing step in the dehydrating process or after completion of the drying process).
  • the air valve 41 and the slurry discharge valve 51 are opened.
  • compressed air is supplied to the filter press 1 through the blow line 40, and the slurry is discharged through the slurry discharge line 50.
  • An end point of the filtration step or the pressing step in the dehydrating process, an end point of the drying process, or timing to proceed to perform a subsequent process may be determined by -a preset period of time.
  • the following methods may be employed to detect end points of the above processes.
  • An end point of the filtration step in the dehydrating process can be determined by detecting when the amount of a solid material supplied into the filter chambers 130 reaches a predetermined value.
  • An end point of the pressing step in the dehydrating process can be determined by detecting when the pressure of the filter chambers 130 becomes lower than the pressing pressure of the heating medium, or when a flow rate of the pressing filtrate or the amount of the pressing filtrate reaches a predetermined value, or when the temperature of the cake in the filter chambers 130 reaches a predetermined value.
  • An end point of the drying process can be determined by detecting a temperature change of the cake in the filter chambers 130, a temperature change of the heating medium, or a temperature change of the filtrate discharge passages 106 and 116.
  • the dehydrating and drying process of slurry in this example includes a dehydrating process to dehydrate slurry by filtration and pressing of the slurry, a drying process to dry the dehydrated slurry, and a blowing process to blow the dehydrated or dried slurry.
  • slurry is supplied to the filter press 1 through the slurry supply line 10, the slurry supply valve 12, and the slurry pressure sensor 14 by the slurry supply pump 11 and is thus filled in the filter chambers 130.
  • water of the slurry is converted into a filtration filtrate and discharged through the filtrate discharge passages 106 and 116 and the filtrate discharge line 35 from the filtrate chambers Sl and SIl.
  • the supply pressure of the slurry is set at, for example, a low absolute pressure of 0.15 MPa to 0.20 MPa at the beginning of the filtration.
  • the supply pressure of the slurry may be increased gradually according to the progress of the filtration. Then, eventually, the supply pressure of the slurry may be set at an absolute pressure of at least 0.6 MPa. It is desirable that the period of time of the filtration is selected optimally depending on properties of the slurry.
  • the slurry may be heated before being supplied to the filter press 1 (preliminary heating filtration). In this case, since the heated slurry is supplied to the filter press 1, the filterability of the slurry can be improved. Further, a heating medium heated in the heating tank 26 may be circulated in the heating medium circulation lines 2OA and 2OB by the heating medium circulation pump 21 and supplied into the heating medium chambers S2 and S 12 in the filter press 1 to heat the slurry during the filtration (heating filtration). In this case, since the slurry is filtered while being heated, the filterability of the slurry can be improved. (2) Pressing Step
  • a heating medium heated by the heating tank 26 is supplied through the heating medium circulation line 2OA to the heating medium chambers S2 and S12 in the filter press 1 by the heating medium circulation pump 21.
  • the heating medium is returned to the heating tank 26 through the heating medium circulation line 2OB, the second heating medium temperature sensor 23, and the heating medium pressure sensor 24.
  • the heating medium is heated by the heating tank 26 and supplied again to the heating medium chambers S2 and S 12 in the filter press 1 through the heating medium circulation line 2OA.
  • the pressure (pressing pressure) of the heating medium in the heating medium chambers S2 is controlled at a predetermined value by the back-pressure valve 25, which is provided in the heating medium circulation line 2OB.
  • the diaphragms 102 of the. first filter plates 100 are swelled toward the filter chambers 130 to thereby press and heat the slurry in the filter chambers 130.
  • Water in the slurry flows as a pressing filtrate out of the filtrate chambers Sl and SIl.
  • the pressing filtrate is discharged through the filtrate discharge passages 106 and 116 to the filtrate discharge line 35.
  • the slurry When the slurry is filtered and pressed in the above manner, the slurry is dehydrated and gradually converted into a cake. In the dehydrating process, only filtration step may be conducted without the pressing step to dehydrate the slurry.
  • the relief valve 3 may temporarily be opened to discharge an accumulated gas in the heating medium chambers S2 and S 12. Further, it is desirable that the pressing pressure of the slurry is adjustable in a range of from an absolute pressure of 0.1 MPa (atmospheric pressure) to an absolute pressure of 1.6 MPa. It is desirable to increase the pressing pressure gradually to a pressure between the supply pressure of the slurry and 1.6 MPa after starting of the pressing step.
  • the temperature of the heating medium should be equal to or more than a saturated vapor temperature corresponding to a vacuum pressure, it is not limited to a specific value.
  • the heating medium should preferably have a temperature of at least 70°C. Thus, the slurry is heated to a preset temperature higher than a predetermined saturated vapor temperature (a saturated vapor temperature corresponding to a vacuum pressure).
  • a heating medium is circulated through the filter press 1. It is desirable that the pressure of the heating medium is adjusted to be lower than the pressing pressure in the pressing step by the back-pressure valve 25.
  • the first selector valve 32A is opened to evacuate the filtrate chambers Sl and SIl in the filter press 1 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31.
  • the vacuum pump 31 may be operated to decompress the interior of the vacuum tank 34 in advance.
  • the filtrate chambers Sl and SI l can instantaneously be decompressed to a vacuum by opening the first selector valve 32A at the beginning of the drying process.
  • the slurry is sufficiently heated in the filter chambers 130 by the heating medium.
  • a large difference is produced between the preset temperature of the slurry and the saturated vapor temperature corresponding to the vacuum pressure. Accordingly, when the slurry in the filter press 1 is instantaneously introduced to an atmosphere under a vacuum pressure in the drying process, thermal energy of the slurry is used for evaporation in addition to heat supplied by the heating medium. As a result, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. The bumping increases a drying rate (evaporation rate) of the slurry.
  • the efficiency of the vacuum pump 31 can be increased by supplying a coolant to the condenser 33 so that steam produced from the slurry (cake) in the filter chambers 130 is converted into water. It is desirable that the vacuum pressure in the drying process is not more than an absolute, pressure of 0.03 MPa.
  • the preset temperature is at least 100°C, which is a saturated vapor temperature of the atmospheric pressure
  • the first selector valve 32A may be left closed after the starting of the drying process, and the second selector valve 32B may be opened so that the steam produced from the slurry is discharged through the filtrate discharge line 35, not through the vacuum line 30.
  • the slurry is sufficiently heated in the filter chambers 130 during the pressing step, and a large difference is produced between the preset temperature of the slurry and a saturated vapor temperature corresponding to an atmospheric pressure. Accordingly, thermal energy of the slurry is used for evaporation to accelerate self-evaporation of water contained in the slurry. Therefore, bumping can be caused to increase a drying rate of the slurry. As a larger difference is produced between the temperature of the slurry
  • the slurry As there is a larger difference between the preset temperature and the saturated vapor temperature, the slurry has a larger quantity of heat so as to enhance the effect of drying the slurry. Therefore, when the drying process is repeatedly performed, timing of starting and stopping the self-evaporation of the slurry have a great influence on an efficiency of the entire system.
  • the temperature of the slurry in the filter chambers is measured to determine this timing.
  • a temperature difference between the temperature of the heating medium at an inlet of the filter press 1 and the temperature of the heating medium at an outlet of the filter press 1 is considered to reflect the temperature of the slurry in the filter chambers.
  • timing of starting and stopping the self-evaporation of the slurry is determined based on a temperature difference between a temperature of the heating medium at the inlet of the filter press 1, which is detected by the first heating medium temperature sensor 22, and a temperature of the heating medium at the outlet of the filter press 1, which is detected by the second heating medium temperature sensor 23. It is desirable that the preset temperature and the saturated vapor temperature are in a range of from 20°C to 70°C. Further, it is desirable that a pressure corresponding to the saturated vapor temperature is not more than an absolute pressure of 0.03 MPa.
  • the self-evaporation of water in the slurry may be started. Further, when a temperature difference between an inlet temperature and an outlet temperature of the heating medium, which are detected by the heating medium temperature sensors 22 and 23, respectively, becomes a predetermined value, the self-evaporation of water in the slurry may be stopped. Alternatively, when a temperature difference between an inlet temperature and an outlet temperature of the heating medium, which are measured by the heating medium temperature sensors 22 and 23, respectively, becomes a predetermined value (e.g., less than 2°C), the self-evaporation of water in the slurry may be started.
  • a predetermined value e.g., less than 2°C
  • the self-evaporation of water in the slurry may be stopped. Further, when a temperature difference between an inlet temperature and an outlet temperature of the heating medium, which are detected by the heating medium temperature sensors 22 and 23, respectively, becomes a predetermined value (e.g., less than 2°C), the self-evaporation of water in the slurry may be started. Then, the self-evaporation of water in the slurry may be stopped after a predetermined period of time (e.g. several minutes, preferably 3 minutes to 10 minutes).
  • a predetermined period of time e.g. several minutes, preferably 3 minutes to 10 minutes.
  • the self-evaporation of water in the slurry may be started. Then, the self-evaporation of water in the slurry may be stopped after a predetermined period of time (e.g. several minutes, preferably 3 minutes to 10 minutes). Alternatively, starting and stopping of the self-evaporation may simply be repeated every period of time (e.g., every 3 minutes, preferably 3 minutes to 10 minutes).
  • the heating medium is circulated at a pressure lower than the pressing pressure to heat the cake in the filter chambers 130.
  • the first selector valve 32A is opened to evacuate the filtrate chambers Sl and SI l in the filter press 1 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31.
  • the first selector valve 32A When a difference between a measured value of the first heating medium temperature sensor 22 and a measured value of the second heating medium temperature sensor 23 reaches a predetermined value after the temperature of the cake in the filter chambers 130 is decreased to a temperature lower than the temperature of the heating medium by a predetermined value, the first selector valve 32A is closed. Then, after the temperature of the cake in the filter chambers 130 is increased to a predetermined temperature, the first selector valve 32A is opened again to evacuate the filtrate chambers S 1 and S 11 by the vacuum pump 31. Such operation is repeated a predetermined number of times. A period of time T from start of heating the slurry to a point where the slurry has the preset temperature may be calculated, and the slurry may be heated for this period of time T.
  • the slurry (sludge) is heated for this calculated period T of time, and then the first selector valve 32A is opened to evacuate the filtrate chambers Sl and Sl 1 by the vacuum pump 31.
  • a blowing process may be performed at desired timing (e.g., after completion of the pressing step in the dehydrating process or after completion of the drying process). In the blowing process, the air valve 41 and the slurry discharge valve 51 are opened. Thus, compressed air is supplied to the filter press 1 through the blow line 40, and the slurry is discharged through the slurry discharge line 50.
  • An end point of the filtration step or the pressing step in the dehydrating process, an end point of the drying process, or timing to proceed to perform a subsequent process may be determined by a preset period of time. Alternatively, the following methods may be employed to detect end points of the above processes.
  • An end point of the filtration step in the dehydrating process can be determined by detecting when the amount of a solid material supplied into the filter chambers 130 reaches a predetermined value.
  • An end point of the pressing step in the dehydrating process can be determined by detecting when the pressure of the filter chambers 130 becomes lower than the pressing pressure of the heating medium, or when a flow rate of the pressing filtrate or the amount of the pressing filtrate reaches a predetermined value, or when the temperature of the cake in the filter chambers 130 reaches a predetermined value.
  • An end point of the drying process can be determined by detecting a temperature change of the cake in the filter chambers 130, a temperature change of the heating medium, or a temperature change of the filtrate discharge passages 106 and 116.
  • a temperature difference between a temperature detected by the first heating medium temperature sensor 22 and a temperature detected by the second heating medium temperature sensor 23 is used as a physical property value reflecting a temperature of the slurry in the filter chambers.
  • the first selector valve 32A is opened and closed every certain period of time.
  • the physical property value reflecting a temperature of the slurry in the filter chambers is not limited to the above example.
  • temperature sensors may be inserted into the filtrate discharge passages 106 and 116 from the filtrate discharge line 35 near the filter press 1. Temperatures of the filtrate which are detected by these temperature sensors may be used as the aforementioned physical property value.
  • the self-evaporation of water in the slurry may be started when the detected temperature of the filtrate becomes at least a predetermined value, and stopped when a temperature difference between an inlet temperature and an outlet temperature of the heating medium, which are measured by the heating medium temperature sensors 22 and 23, becomes a predetermined value, or after a predetermined period of time.
  • FIG. 6 is a cross-sectional view showing a main portion of a filter press 201 according to a second embodiment of the present invention.
  • the filter press 201 differs from the filter press 1 according to the first embodiment in that the heat transfer member 112 and the body 111 located at a peripheral portion of the second filter plate 110 are replaced with a heat transfer member 312 integrally made of metal.
  • FIGS. 7 A and 7B are cross-sectional views showing the second filter plate 310.
  • the heat transfer member 312 of the second filter plate 310 is in the form of a hollow doughnut.
  • the hollow portion of the heat transfer member 312 serves as a heating medium chamber S22.
  • FIGS. 8 A and 8B are cross-sectional views showing a filter plate 410 according to a third embodiment of the present invention.
  • FIG. 8C is a partial enlarged view of FIG. 8B.
  • the filter plate 410 shown in FIGS. 8 A through 8 C may be used instead of the second filter plates 110 in the first embodiment.
  • the filter plate 410 differs from the second filter plate 110 of the first embodiment in that the filter plate 410 has an extensible portion 412 formed like bellows at ends of the heat transfer member 112. As shown in FIG. 8C, the heat transfer member 112 is secured to the body 111 by a fastener 112a.
  • Other structures of the filter plate 410 are the same as the second filter plate .110 in the first embodiment and will not be described repetitively.
  • FIG. 9 is a cross-sectional view showing a main portion of a filter press 501 according to a fourth embodiment of the present invention.
  • the filter plate 100 with the diaphragm 102 may have less heat transferability, and the life of the diaphragm 102 should be considered.
  • the filter plates 100 of the first embodiment are replaced with filter plates 110 (see FIGS. 5 A and 5B) each having a heat transfer member 112 made of metal.
  • Filter chambers 130 are formed between the filter plates 110.
  • the filter press 501 in the present embodiment is configured so as not to press slurry in the filter chambers 130. Accordingly, it is not necessary to provide the back-pressure valve 25 in the first embodiment.
  • the dehydrating and drying process of slurry in this example includes a dehydrating process to dehydrate slurry by filtration of the slurry, a drying process to dry the dehydrated slurry, and a blowing process to blow the dehydrated or dried slurry.
  • slurry is supplied to the filter press 501 through the slurry supply line 10, the slurry supply valve 12, and the slurry pressure sensor 14 by the slurry supply pump 11 and is thus filled in the filter chambers 130.
  • water of the slurry is converted into a filtration filtrate and discharged through the filtrate discharge passages 116 and the filtrate discharge line 35 from the filtrate chambers Sl.
  • the supply pressure of the slurry is set at, for example, a low absolute pressure of 0.15 MPa to 0.20 MPa at the beginning of the filtration.
  • the supply pressure of the slurry may be increased gradually according to the progress of the filtration. Then, eventually, the supply pressure of the slurry may be set at an absolute pressure of at least 1.6 MPa. It is desirable that the period of time of the filtration is selected optimally depending on properties of the slurry.
  • the slurry may be heated before being supplied to the filter press 501
  • a heating medium heated in the heating tank 26 may be circulated in the heating medium circulation lines 2OA and 2OB by the heating medium circulation pump 21 and supplied into the heating medium chambers S 12 in the filter press 501 to heat the slurry during the filtration (heating filtration). In this case, since the slurry is filtered while being heated, the filterability of the slurry can be improved.
  • a heating medium heated in the heating tank 26 is circulated and supplied into the heating medium chambers S 12 in the filter press 501 to heat the slurry to a temperature higher than a saturated vapor temperature corresponding to a predetermined vacuum pressure.
  • the first selector valve 32A is opened at the beginning of the drying process.
  • the filtrate chambers SI l in the filter press 501 are evacuated through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31 to introduce the slurry to an atmosphere under a vacuum pressure.
  • the vacuum pump 31 may be operated to decompress the interior of the vacuum tank 34 in advance. In such a case, the filtrate chambers SI l can instantaneously be decompressed to a vacuum by opening the first selector valve 32A at the beginning of the drying process.
  • the slurry is sufficiently heated in the filter chambers 130 by the heating medium.
  • a large difference is produced between the preset temperature of the slurry and the saturated vapor temperature corresponding to the vacuum pressure. Accordingly, when the slurry in the filter press 501 is instantaneously introduced to an atmosphere under a vacuum pressure in the drying process, thermal energy of the slurry is used for evaporation in addition to heat supplied by the heating medium. As a result, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. The bumping increases a drying rate (evaporation rate) of the slurry.
  • the heating medium is also circulated at a low pressure.
  • the first selector valve 32A is opened to evacuate the filtrate chambers SI l in the filter press 501 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31. After the temperature of the cake in the filter chambers 130 is decreased to a temperature lower than the temperature of the heating medium by a predetermined value, the first selector valve 32A is closed. Then, after the temperature of the cake in the filter chambers 130 is increased to a predetermined temperature, the first selector valve 32A is opened again to evacuate the filtrate chambers SI l by the vacuum pump 31. Such operation is repeated a predetermined number of times. [Blowing Process]
  • a blowing process may be performed at desired timing (e.g., after completion of the filtration in the dehydrating process or after completion of the drying process).
  • the air valve 41 and the slurry discharge valve 51 are opened.
  • compressed air is supplied to the filter press 501 through the blow line 40, and the slurry is discharged through the slurry discharge line 50.
  • FIG. 10 is a cross-sectional view showing a main portion of a filter press 601 according to a fifth embodiment of the present invention. As shown in FIG.
  • the filter press 601 differs from the filter press 501 of the fourth embodiment in that the second filter plates 310 (see FIGS. 7A and 7B) of the second embodiment are used instead of the filter plates 110 of the fourth embodiment.
  • Other structures of the filter press 601 are the same as the filter press 501 in the fourth embodiment and will not be described repetitively.
  • FIG. 11 is a cross-sectional view showing a main portion of a filter press 701 according to a sixth embodiment of the present invention. As shown in FIG.
  • the filter press 701 differs from the filter press 501 of the fourth embodiment in that the filter plates 410 (see FIGS. 8 A and 8B) of the third embodiment are used instead of the filter plates 110 of the fourth embodiment.
  • Other structures of the filter press 701 are the same as the filter press 501 in the fourth embodiment and will not be described repetitively.
  • FIG. 12 is a schematic view showing a dehydrating and drying apparatus according to a seventh embodiment of the present invention.
  • the dehydrating and drying apparatus has a similar structure to the dehydrating and drying apparatus shown in FIG. 1.
  • the dehydrating and drying apparatus shown in FIG. 12 differs from the dehydrating and drying apparatus shown in FIG. 1 as follows.
  • a filtrate is discharged from the filter chambers in the filter press 1 through a filtrate discharge line 35.
  • the filtrate discharge line 35 includes a first filtrate discharge line 35 A connected to a portion of a plurality of filtrate chambers and a second filtrate discharge line 35B connected to the rest of the plurality of filtrate chambers.
  • the second filtrate discharge line 35B has a third selector valve (control valve) 32C.
  • control valve control valve
  • the first selector valve 32 A and the third selector valve 32C are opened while the second selector valve 32B is closed.
  • the second selector valve 32B and the third selector valve 32C are opened while the first selector valve 32A is closed.
  • the pressure of the filter chambers in the filter press 1 can be increased from vacuum to an atmospheric pressure by opening the second selector valve 32B and the third selector valve 32C.
  • a compressor (not shown) is connected to the blow line 40 for generating compressed air.
  • compressed air is blown from the compressor through the blow line 40 into the filter chambers so that slurry remaining within the filter press 1 and slurry remaining at a slurry supply port of the filter chambers are discharged through the slurry discharge line 50 by the compressed air.
  • the blow line 40 is branched into a first blow line 40A connected to the filter press 1 and a second blow line 4OB connected to the second filtrate discharge line 35B.
  • the first blow line 4OA has a first air valve 4 IA
  • the second blow line 4OB has a second air valve 41B.
  • the slurry discharge line 50 has a slurry discharge valve 51.
  • the dehydrating and drying process of slurry in this example includes a dehydrating process to dehydrate slurry by filtration and pressing of the slurry, a drying process to dry the dehydrated slurry, a blowing process to blow the dehydrated or dried slurry, and a ventilation process to allow compressed air to pass through the filter chambers.
  • slurry is supplied to the filter press 1 through the slurry supply line 10, the slurry supply valve 12, and the slurry pressure sensor 14 by the slurry supply pump 11 and is thus filled in the filter chambers 130.
  • water of the slurry is converted into a filtration filtrate and discharged through the filtrate discharge passages 106 and 116 and the filtrate discharge line 35 from the filtrate chambers Sl and SI l.
  • the supply pressure of the slurry is set at, for example, a low absolute pressure of 0.15 MPa to 0.20 MPa at the beginning of the filtration.
  • the supply pressure of the slurry may be increased gradually according to the progress of the filtration. Then, eventually, the supply pressure of the slurry may be set at an absolute pressure of at least 0.6 MPa. It is desirable that the period of time of the filtration is selected optimally depending on properties of the slurry.
  • the slurry may be heated before being supplied to the filter press 1 (preliminary heating filtration). In this case, since the heated slurry is supplied to the filter press 1, the filterability of the slurry can be improved. Further, a heating medium heated in the heating tank 26 may be circulated in the heating medium circulation lines 2OA and 2OB by the heating medium circulation pump 21 and supplied into the heating medium chambers S2 and S 12 in the filter press 1 to heat the slurry during the filtration (heating filtration). In this case, since the slurry is filtered while being heated, the filterability of the slurry can be improved. (2) Pressing Step
  • a heating medium heated by the heating tank 26 is supplied through the heating medium circulation line 2OA to the heating medium chambers S2 and S 12 in the filter press 1 by the heating medium circulation pump 21.
  • the heating medium is returned to the heating tank 26 through the heating medium circulation line 2OB, the second heating medium temperature sensor 23, and the heating medium pressure sensor 24.
  • the heating medium is heated by the heating tank 26 and supplied again to the heating medium chambers S2 and S 12 in the filter press 1 through the heating medium circulation line 20 A.
  • the pressure (pressing pressure) of the heating medium in the heating medium chambers S2 is controlled at a predetermined value by the back-pressure valve 25, which is provided in the heating medium circulation line 2OB.
  • the diaphragms 102 of the first filter plates 100 are swelled toward the filter chambers 130 to thereby press and heat the slurry in the filter chambers 130.
  • Water in the slurry flows as a pressing filtrate out of the filtrate chambers Sl and SI l.
  • the pressing filtrate is discharged through the filtrate discharge passages 106 and 116 to the filtrate discharge line 35.
  • the slurry When the slurry is filtered and pressed in the above manner, the slurry is dehydrated and gradually converted into a cake. In the dehydrating process, only filtration step may be conducted without the pressing step to dehydrate the slurry.
  • the relief valve 3 At the beginning of the pressing step, the relief valve 3 (see FIG. 1) may temporarily be opened to discharge an accumulated gas in the heating medium chambers S2 and S 12.
  • the pressing pressure of the slurry is adjustable in a range of from an absolute pressure of 0.1 MPa (atmospheric pressure) to an absolute pressure of 1.6 MPa. It is desirable to increase the pressing pressure gradually to a pressure between the supply pressure of the slurry and 1.6 MPa after starting of the pressing step.
  • the temperature of the heating medium should be equal to or more than a saturated vapor temperature corresponding to a vacuum pressure, it is not limited to a specific value.
  • the heating medium should preferably have a temperature of at least 70°C.
  • the slurry is heated to a preset temperature higher than a predetermined saturated vapor temperature (a saturated vapor temperature corresponding to a vacuum pressure).
  • a heating medium is circulated through the filter press 1. It is desirable that the pressure of the heating medium is adjusted to be lower than the pressing pressure in the pressing step by the back-pressure valve 25.
  • the first selector valve 32A and the third selector valve 32C are opened to evacuate the filtrate chambers Sl and Sl 1 in the filter press 1 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31.
  • the vacuum pump 31 may be operated to decompress the interior of the vacuum tank 34 in advance.
  • the filtrate chambers Sl and SI l can instantaneously be decompressed to a vacuum by opening the first selector valve 32A and the third selector valve 32C at the beginning of the drying process.
  • the slurry is sufficiently heated in the filter chambers 130 by the heating medium.
  • a large difference is produced between the preset temperature of the slurry and the saturated vapor temperature corresponding to the vacuum pressure. Accordingly, when the slurry in the filter press 1 is instantaneously introduced to an atmosphere under a vacuum pressure in the drying process, thermal energy of the slurry is used for evaporation in addition to heat supplied by the heating medium. As a result, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. The bumping increases a drying rate (evaporation rate) of the slurry.
  • the efficiency of the vacuum pump 31 can be increased by supplying a coolant to the condenser 33 so that steam produced from the slurry (cake) in the filter chambers 130 is converted into water. It is desirable that the vacuum pressure in. the drying process is not more than an absolute pressure of 0.03 MPa.
  • the preset temperature is at least 100°C, which is a saturated vapor temperature of the atmospheric pressure
  • the first selector valve 32A may be left closed after the starting of the drying process, and the second selector valve 32B and the third selector valve 32C may be opened so that the steam produced from the slurry is discharged through the filtrate discharge line 35, not through the vacuum line 30.
  • the slurry is sufficiently heated in the filter chambers 130 during the pressing step, and a large difference is produced between the preset temperature of the slurry and a saturated vapor temperature corresponding to an atmospheric pressure. Accordingly, thermal energy of the slurry is used for evaporation to accelerate self-evaporation of water contained in the slurry. Therefore, bumping can be caused to increase a drying rate of the slurry.
  • the heating medium is also circulated at a pressure lower than the pressing pressure.
  • the first selector valve 32A and the third selector valve 32C are opened to evacuate the filtrate chambers Sl and SIl in the filter press 1 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31.
  • the first selector valve 32A is closed.
  • the first selector valve 32A is opened again to evacuate the filtrate chambers Sl and SIl by the vacuum pump 31.
  • a blowing process may be performed at desired timing (e.g., after completion of the pressing step in the dehydrating process or after completion of the drying process).
  • the first air valve 41A and the slurry discharge valve 51 are opened while the first selector valve 32 A, the second selector valve 32B, the third selector valve 32C, and the second air valve 4 IB are closed.
  • compressed air is supplied through the first blow line 4OA to the filter press 1, and the slurry is discharged through the slurry discharge line 50.
  • a ventilation process may be performed at desired timing (e.g., after completion of the filtration step or the pressing step in the dehydrating process, or during the drying process, or after the drying process).
  • a ventilation process may be performed several times during the drying process.
  • a ventilation process after completion of the filtration step in the dehydrating process serves to discharge water remaining in the slurry within the filter chambers 130.
  • a ventilation process after completion of the drying process serves to further dry a cake that has been dried mainly in the filter chambers 130 and cracked so as to increase its surface area.
  • One of steam, air, dehumidified air, and hot discharge gas may be used as compressed air to be supplied. Ventilation of compressed air in the ventilation process is classified into the following two types.
  • the compressed air is supplied through the filter cloths into the filter chambers 130. Water or steam in the filter chambers 130 is discharged through the first filtrate discharge line 35 A.
  • the second air valve 4 IB and the first selector valve 32A are opened, and the first air valve 41A, the second selector valve 32B, the third selector valve 32C, and the slurry discharge valve 51 are closed.
  • the vacuum pump 31 is operated to evacuate the filtrate chambers Sl and SI l.
  • the second blow line 4OB, the second filtrate discharge line 35B, and the first filtrate discharge line 35A form a ventilation mechanism for allowing compressed air to pass through the filter chambers 130.
  • the second air valve 4 IB and the second selector valve 32B may be opened, and the first air valve 4 IA, the third selector valve 32C, and the slurry discharge valve 51 may be closed.
  • An end point of the filtration step or the pressing step in the dehydrating process, an end point of the drying process, or timing to proceed to perform a subsequent process may be determined by a preset period of time. Alternatively, the following methods may be employed to detect end points of the above processes.
  • An end point of the filtration step in the dehydrating process can be determined by detecting when the amount of a solid material supplied into the filter chambers 130 reaches a predetermined value.
  • An end point of the pressing step in the dehydrating process can be determined by detecting when the pressure of the filter chambers 130 becomes lower than the pressing pressure of the heating medium, or when a flow rate of the pressing filtrate or the amount of the pressing filtrate reaches a predetermined value, or when the temperature of the cake in the filter chambers 130 reaches a predetermined value.
  • An end point of the drying process can be determined by detecting a temperature change of the cake in the filter chambers 130, a temperature change of the heating medium, or a temperature change of the filtrate discharge passages 106 and 116.
  • the filter press described in the second to sixth embodiments may be used instead of the filter press 1 in the present embodiment.
  • the dehydrating and drying process of slurry in this example includes a . dehydrating process to dehydrate slurry by filtration of the slurry, a drying process to dry the dehydrated slurry, a blowing process to blow the dehydrated or dried slurry, and a ventilation process to allow compressed air to pass through the filter chambers.
  • slurry is supplied to the filter press 501 through the slurry supply line 10, the slurry supply valve 12, and the slurry pressure sensor 14 by the slurry supply pump 11 and is thus filled in the filter chambers 130.
  • water of the slurry is converted into a filtration filtrate and discharged through the filtrate discharge passages 116 and the filtrate discharge line 35 from the filtrate chambers Sl.
  • the supply pressure of the slurry is set at, for example, a low absolute pressure of 0.15 MPa to 0.20 MPa at the beginning of the filtration.
  • the supply pressure of the slurry may be increased gradually according to the progress of the filtration. Then, eventually, the supply pressure of the slurry may be set at an absolute pressure of at least 1.6 MPa. It is desirable that the period of time of the filtration is selected optimally depending on properties of the slurry.
  • the slurry may be heated before being supplied to the filter press 501 (preliminary heating filtration). In this case, since the heated slurry is supplied to the filter press 501, the filterability of the slurry can be improved. Further, a heating medium heated in the heating tank 26 may be circulated in the heating medium circulation lines 20 A and 2OB by the heating medium circulation pump 21 and supplied into the heating medium chambers S 12 in the filter press 501 to heat the slurry during the filtration (heating filtration). In this case, since the slurry is filtered while being heated, the filterability of the slurry can be improved. [Drying Process]
  • a heating medium heated in the heating tank 26 is circulated and supplied into the heating medium chambers S 12 in the filter press 501 to heat the slurry to a temperature higher than a saturated vapor temperature corresponding to a predetermined vacuum pressure.
  • the first selector valve 32A and the third selector valve 32C are opened at the beginning of the drying process.
  • the filtrate chambers SIl in the filter press 501 are evacuated through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31 to introduce the slurry to an atmosphere under a vacuum pressure.
  • the vacuum pump 31 may be operated to decompress the interior of the vacuum tank 34 in advance.
  • the filtrate chambers SIl can instantaneously be decompressed to a vacuum by opening the first selector valve 32A and the third selector valve 32C at the beginning of the drying process.
  • the slurry is sufficiently heated in the filter chambers 130 by the heating medium.
  • a large difference is produced between the preset temperature of the slurry and the saturated vapor temperature corresponding to the vacuum pressure. Accordingly, when the slurry in the filter press 501 is instantaneously introduced to an atmosphere under a vacuum pressure in the drying process, thermal energy of the slurry is used for evaporation in addition to heat supplied by the heating medium. As a result, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. The bumping increases a drying rate (evaporation rate) of the slurry.
  • the heating medium is also circulated at a low pressure.
  • the first selector valve 32A and the third selector valve 32C are opened to evacuate the filtrate chambers SI l in the filter press 501 through the condenser 33, the vacuum tank 34, and the vacuum line 30 by the vacuum pump 31.
  • the first selector valve 32A is closed.
  • the first selector valve 32A is opened again to evacuate the filtrate chambers SI l by the vacuum pump 31. Such operation is repeated a predetermined number of times.
  • a blowing process may be performed at desired timing (e.g., after completion of the filtration in the dehydrating process or after completion of the drying process).
  • the first air valve 41 A and the slurry discharge valve 51 are opened, and the first selector valve 32A, the second selector valve 32B, the third selector valve 32C, and the second air valve 41B are closed.
  • compressed air is supplied to the filter press 501 through the first blow line 4OA, and the slurry is discharged through the slurry discharge line 50.
  • a ventilation process may be performed at desired timing (e.g., after completion of the filtration in the dehydrating process, or during the drying process, or after the drying process).
  • a ventilation process may be performed several times during the drying process. Either of the aforementioned methods (A) and (B) may be employed for the ventilation process.
  • FIG. 13 is a schematic view showing a dehydrating and drying apparatus according to an eighth embodiment of the present invention.
  • the dehydrating and drying apparatus has a similar structure to the dehydrating and drying apparatus shown in FIG. 1.
  • the dehydrating and drying apparatus shown in FIG. 13 differs from the dehydrating and drying apparatus shown in FIG. 1 as follows.
  • the filter chambers in the filter press 1 are evacuated through a vacuum line 30 having a first selector valve (control valve) 32A and three vacuum tanks 34A, 34B, and 34C. Although three vacuum tanks are provided in parallel in FIG. 13, the number of the vacuum tanks is not limited to three. At least two vacuum tanks may be provided.
  • the vacuum line 30, the vacuum pump 31, the first selector valve 32 A, and the vacuum tanks 34 A, 34B, and 34C form a decompressing mechanism for decompressing the slurry in the filter chambers of the filter press 1.
  • a cooling mechanism 33 is provided for cooling the vacuum tanks 34A, 34B, and 34C.
  • a coolant is supplied to the cooling mechanism 33. Heat is exchanged between steam introduced from the filter press 1 to the cooling mechanism 33 and the coolant in the cooling mechanism 33. Thus, the steam is condensed and then discharged as a condensate from the cooling mechanism 33.
  • the vacuum tank 34A has a vacuum pump valve 36A disposed between the vacuum pump 31 and the vacuum tank 34A, a filter press valve 37A disposed between the filter press 1 and the vacuum tank 34 A, and a condensate discharge valve 38A for discharging a condensate produced by the cooling mechanism 33.
  • the vacuum tank 34B has a vacuum pump valve 36B, a filter press valve 37B, and a condensate discharge valve 38B.
  • the vacuum tank 34C has a vacuum pump valve 36C, a filter press valve 37C, and a condensate discharge valve 38C.
  • Each of the vacuum pump 31 and the vacuum tanks 34A, 34B, and 34C has a pressure sensor (not shown). It is desirable that the volume of the vacuum tanks 34A, 34B, and 34C is about 5 to 20 times, more preferably about 5 to 10 times, the volume of the piping from the filter press 1 to the first selector valve 32A.
  • a filtrate discharge line 35 is connected to the vacuum line 30.
  • the filtrate discharge line 35 serves to discharge a filtrate from the filter chambers in the filter press 1 during dehydration of the slurry.
  • the filtrate discharge line 35 has a second selector valve (control valve) 32B.
  • the second selector valve 32B When the filtrate is to be discharged from the filter chambers, the second selector valve 32B is opened while the first selector valve 32A is closed. Further, the pressure of the filter chambers in the filter press 1 can be increased immediately from vacuum to an atmospheric pressure by opening the second selector valve 32B.
  • a compressor (not shown) is connected to the blow line 40 for generating compressed air.
  • compressed air is blown from the compressor through the blow line 40 into the filter chambers so that slurry remaining within the filter press 1 and slurry remaining at a slurry supply port of the filter chambers are discharged through the slurry discharge line 50 by the compressed air.
  • the blow line 40 has an air valve 41, and the slurry discharge line 50 has a slurry discharge valve 51.
  • the dehydrating and drying process of slurry in this example includes a dehydrating process to dehydrate slurry by filtration and pressing of the slurry, a drying process to dry the dehydrated slurry, and a blowing process to blow the dehydrated or dried slurry.
  • slurry is supplied to the filter press 1 through the slurry supply line 10, the slurry supply valve 12, and the slurry pressure sensor 14 by the slurry supply pump 11 and is thus filled in the filter chambers 130.
  • water of the slurry is converted into a filtration filtrate and discharged through the filtrate discharge passages 106 and 116 and the filtrate discharge line 35 from the filtrate chambers Sl and SI l.
  • the supply pressure of the slurry is set at, for example, a low absolute pressure of 0.15 MPa to 0.20 MPa at the beginning of the filtration.
  • the supply pressure of the slurry may be increased gradually according to the progress of the filtration.
  • the supply pressure of the slurry may be set at an absolute pressure of at least 0.6 MPa. It is desirable that the period of time of the filtration is selected optimally depending on properties of the slurry.
  • the slurry may be heated before being supplied to the filter press 1 (preliminary heating filtration). In this case, since the heated slurry is supplied to the filter press 1, the filterability of the slurry can be improved. Further, a heating medium heated in the heating tank 26 may be circulated in the heating medium circulation lines 2OA and 20B by the heating medium circulation pump 21 and supplied into the heating medium chambers S2 and S 12 in the filter press 1 to heat the slurry during the filtration (heating filtration). In this case, since the slurry is filtered while being heated, the filterability of the slurry can be improved.
  • a heating medium heated by the heating tank 26 is supplied through the heating medium circulation line 2OA to the heating medium chambers S2 and S 12 in the filter press 1 by the heating medium circulation pump 21.
  • the heating medium is returned to the heating tank 26 through the heating medium circulation line 2OB, the second heating medium temperature sensor 23, and the heating medium pressure sensor 24.
  • the heating medium is heated by the heating tank 26 and supplied again to the heating medium chambers S2 and S 12 in the filter press 1 through the heating medium circulation line 2OA.
  • the pressure (pressing pressure) of the heating medium in the heating medium chambers S2 is controlled at a predetermined value by the back-pressure valve 25, which is provided in the heating medium circulation line 2OB.
  • the diaphragms 102 of the first filter plates 100 are swelled toward the filter chambers 130 to thereby press and heat the slurry in the filter chambers 130.
  • Water in the slurry flows as a pressing filtrate out of the filtrate chambers Sl and SI l.
  • the pressing filtrate is discharged through the filtrate discharge passages 106 and 116 to the filtrate discharge line 35.
  • the pressing pressure of the slurry is adjustable in a range of from an absolute pressure of 0.1 MPa (atmospheric pressure) to an absolute pressure of 1.6 MPa. It is desirable to increase the pressing pressure gradually to a pressure between the supply pressure of the slurry and 1.6 MPa after starting of the pressing step.
  • the temperature of the heating medium should be equal to or more than a saturated vapor temperature corresponding to a vacuum pressure, it is not limited to a specific value.
  • the heating medium should preferably have a temperature of at least 70°C.
  • the slurry is heated to a preset temperature higher than a predetermined saturated vapor temperature (a saturated vapor temperature corresponding to a vacuum pressure).
  • a heating medium is circulated through the filter press 1. It is desirable that the pressure of the heating medium is adjusted to be lower than the pressing pressure in the pressing step by the back-pressure valve 25. It is desirable that the vacuum tanks 34A, 34B, and 34C are decompressed to a predetermined pressure, preferably at most an absolute pressure of 0.03 MPa, more preferably at most 0.02 MPa during the pressing step in the dehydrating process.
  • the vacuum tanks 34 A, 34B, and 34C and the vacuum pump 31 may be operated as shown in Table 1.
  • the vacuum pump valves 36 A, 36B, and 36C and the filter press valves 37A, 37B, and 37C of the vacuum tanks 34A, 34B, and 34C are opened, and the first selector valve 32A and the condensate discharge valves 38 A, 38B, and 38C of the vacuum tanks 34A, 34B, and 34C are closed.
  • the vacuum pump 31 and the cooling mechanism 33 are operated (preparation).
  • the vacuum pump valves 36 A, 36B, and 36C and the filter press valves 37A, 37B, and 37C of the vacuum tanks 34A, 34B, and 34C are closed, and the vacuum pump 31 is stopped (preset pressure).
  • Vacuum 1 listed in table 1 is established immediately after starting of the drying process. Then, Vacuum 2 to Vacuum 5 are repeated.
  • the vacuum pump 31 may continuously be operated to decompress the filter press 1 without switching the respective valves.
  • the slurry is sufficiently heated in the filter chambers 130 by the heating medium.
  • a large difference is produced between the preset temperature of the slurry and the saturated vapor temperature corresponding to the vacuum pressure. Accordingly, when the slurry in the filter press 1 is instantaneously introduced to an atmosphere under a vacuum pressure in the drying process, thermal energy of the slurry is used for evaporation in addition to heat supplied by the heating medium. As a result, self-evaporation of water contained in the slurry is accelerated so as to cause bumping. The bumping increases a drying rate (evaporation rate) of the slurry.
  • the efficiency of the vacuum pump 31 can be increased by supplying a coolant to the cooling mechanism 33 so that steam produced from the slurry (cake) in the filter chambers 130 is converted into water.
  • the preset temperature is at least 100°C, which is a saturated vapor temperature of the atmospheric pressure
  • the first selector valve 32A may be left closed after the starting of the drying process, and the second selector valve 32B may be opened so that the steam produced from the slurry is discharged through the filtrate discharge line 35, not through the vacuum line 30.
  • the slurry is sufficiently heated in the filter chambers 130 during the pressing step, and a large difference is produced between the preset temperature of the slurry and a saturated vapor temperature corresponding to an atmospheric pressure. Accordingly, thermal energy of the slurry is used for evaporation to accelerate self-evaporation of water contained in the slurry. Therefore, bumping can be caused to increase a drying rate of the slurry.
  • the heating medium is also circulated at a pressure lower than the pressing pressure.
  • the first selector valve 32A is opened to evacuate the filtrate chambers Sl and SIl in the filter press 1. After the temperature of the cake in the filter chambers 130 is decreased to a temperature lower than the temperature of the heating medium by a predetermined value, the first selector valve 32A is closed. Then, after the temperature of the cake in the filter chambers 130 is increased to a predetermined temperature, the first selector valve 32A is opened again to evacuate the filtrate chambers Sl and SI l by the vacuum pump 31. Such operation is repeated a predetermined number of times.
  • a blowing process may be performed at desired timing (e.g., after completion of the pressing step in the dehydrating process or after completion of the drying process).
  • the air valve 41 and the slurry discharge valve 51 are opened.
  • compressed air is supplied to the filter press
  • An end point of the filtration step or the pressing step in the dehydrating process, an end point of the drying process, or timing to proceed to perform a subsequent process may be determined by a preset period of time. Alternatively, the following methods may be employed to detect end points of the above processes. (1) An end point of the filtration step in the dehydrating process can be determined by detecting when the amount of a solid material supplied into the filter chambers 130 reaches a predetermined value.
  • An end point of the pressing step in the dehydrating process can be determined by detecting when the pressure of the filter chambers 130 becomes lower than the pressing pressure of the heating medium, or when a flow rate of the pressing filtrate or the amount of the pressing filtrate reaches a predetermined value, or when the temperature of the cake in the filter chambers 130 reaches a predetermined value.
  • An end point of the drying process can be determined by detecting a temperature change of the cake in the filter chambers 130, a temperature change of the heating medium, or a temperature change of the filtrate discharge passages 106 and 116.
  • vacuum tanks 34A, 34B, and 34C are provided in the present embodiment.
  • the number of the vacuum tanks is not limited to three. Two vacuum tanks can also achieve the above effects if a condensate is not discharged from the vacuum tanks.
  • the filter press described in the second and third embodiments may be used instead of the filter press 1 in the present embodiment.
  • a dehydrating process and a drying process of slurry can be performed with minimum energy consumption in a short period of time. Further, ease of separation of a cake can be improved.
  • the slurry supply pipe 121 is connected to the central portion of the clamping plate 120A, and each of the filter plates has an opening located at a central portion thereof.
  • the present invention is not limited to the illustrated examples.
  • the filter press may be configured such that slurry is supplied from above or blow the filter plates. [Example 1]
  • Table 2 As shown in Table 2, sludge including a large amount of organic matter having a concentration of 33 g/1 and an ignition loss of 68 %.was used as test slurry. Drying time was calculated based on a time point at which a water content of a dried cake became 40 % in experiments.
  • Drying was conducted under conditions in which a saturated vapor temperature corresponding to a vacuum pressure was 48°C, and in which a temperature difference between a cake temperature and the saturated vapor temperature was 5°C. Drying time at which a water content of a dried cake became 40 % was 52 minutes, and a filtration rate was 0.64 kg-m ⁇ -h "1 .
  • the temperature of the cake was maintained in a range of from 78°C to 88°C.
  • a saturated vapor temperature corresponding to a vacuum pressure was 48°C
  • drying was conducted in a state in which a temperature difference between the temperature of the cake and the saturated vapor temperature was in a range of from 30°C to 40°C.
  • Drying time at which a water content of a dried cake became 40 % was 30 minutes, and a filtration rate was 0.78 kg-m ⁇ 2 -h " ⁇
  • the filtration rate became 1.22 times that in the comparative experiment.
  • a power of the vacuum pump 31 and the condenser 33 during the drying process was equal to 42 % of that in the comparative experiment.
  • Sludge including a large amount of organic matter having a concentration of 28 g/1 and an ignition loss of 78 % was used as test slurry.
  • the filter press used in the experiment for the present invention had a filtration area of 3.45 m 2 and a filter chamber volume of 34 liters.
  • the filter press used in the comparative experiment had a filtration area of 3.45 m 2 and a filter chamber volume of 50 liters.
  • Vacuum pressure 0.01 MPa
  • Heating medium pressure 0.13 MPa
  • drying time was calculated based on a time point at which a water content of a dried cake became 55 % in a continuous operation.
  • the drying time at which a water content of a dried cake became about 55 % in a continuous operation was 70 minutes.
  • a filtration rate was 0.68 kg/m 2> h.
  • a preset temperature of slurry was 80°C.
  • the first selector valve 32A was opened, and the filter chambers were maintained at 0.01 MPa for 5 minutes. Then, the first selector valve 32A was closed. This operation was repeated 6 times. Operation results are listed in Table 3.
  • Organic sludge having a high compressibility was used as test sludge.
  • Inorganic sludge having a low compressibility may shrink due to drying.
  • the cake should be brought into continuous contact with heat transfer surfaces in order to maintain heat transfer.
  • an extensible portion 412 may be provided on the heat transfer member 112 of the filter plate 410 in the sixth embodiment shown in FIG. 11 to bring heat transfer surfaces into continuous contact with the cake.
  • the dehydrating and drying apparatus can be operated without a lowered efficiency.
  • the filter press used in the experiment had a filtration area of 3.45 m 2 and a filter chamber volume of 50 liters.
  • drying time was calculated based on a time point at which a water content of a dried cake became 55 % in a continuous operation.
  • the drying time at which a water content of a dried cake became about 55 % in a continuous evacuation operation was 70 minutes.
  • a filtration rate was 0.68 kg/m 2 -h.
  • a preset temperature Tl was set to be 80°C.
  • the first selector valve 32A was closed when a temperature difference between an inlet temperature T3 and an outlet temperature T4 of a heating medium was 1°C. Operation results are listed in Table 4.
  • the first selector valve 32A was opened and closed at a certain frequency under the same conditions as in Example 3 to perform self-evaporation of slurry. Operation results are listed in Table 5.
  • a compressed gas was supplied from the second blow line 4OB through the second filtrate discharge line 35B into the filtrate chambers Sl and SI l after completion of the drying process.
  • the compressed gas was supplied to the filter chambers 130 through the filter cloths. Water or steam in the filter chambers 130 was discharged through the first filtrate discharge line 35 A.
  • the second air valve 4 IB and the first selector valve 32A were opened, and the first air valve 4 IA, the second selector valve 32B, the third selector valve 32C, and the slurry discharge valve 51 were closed.
  • the vacuum pump 31 was operated to evacuate the filtrate chambers Sl and SI l.
  • the compressed air was supplied at a flow rate of the 100 1/min for 4 minutes.
  • the temperature of the cake was maintained in a range of from 78°C to 88°C.
  • a saturated vapor temperature corresponding to a vacuum pressure was 48°C
  • drying was conducted in a state in which a temperature difference between the temperature of the cake and the saturated vapor temperature was in a range of from 30°C to 40°C.
  • Drying time at which a water content of a dried cake became 40 % was 30 minutes, and a filtration rate was 0.78 kg-m ⁇ -h "1 .
  • the filtration rate became 1.22 times that in Comparative Experiment 1.
  • a power of the vacuum pump 31 and the condenser 33 during the drying process was equal to 42 % of that in Comparative Experiments.
  • the cake was heated even during the drying process, and operation of immediately introducing the filter press 1 to a vacuum atmosphere was repeated a plurality of times. As a result, it was possible to maintain acceleration of the self-evaporation due to sufficient thermal energy of the cake. Accordingly, drying could be completed in a shorter period of time. Further, the dried cake was not attached to the filter cloths and the heat transfer members and could be separated from the filter cloths and the heat transfer members by its own weight.
  • Heating medium pressure 0.13 MPa Heating medium temperature: 8O 0 C
  • Vacuum pressure 100 MPa [Ventilation Process]
  • a drying time was 60 minutes, a water content of a cake was 55 %, and a filtration rate was 0.60 kg-m ⁇ -h "1 .
  • a drying time was 40 minutes, a ventilation time was 4 minutes, a water content of a cake was 54 %, and a filtration rate was 0.68 kg-m ⁇ -h "1 .
  • the sludge could be dried in a shorter period of time.
  • a drying time at which a water content of a cake became 40 % was 30 minutes.
  • decompression of the filter press, discharge of a condensate, and decompression of the three vacuum tanks were simultaneously performed for each of the three vacuum tanks, and these processes were repeated. Accordingly, the filter press could sufficiently be decompressed, and drying could be completed in a shorter period of time.
  • the present invention is suitably used for a dehydrating and drying apparatus for dehydrating and drying slurry such as sludge discharged from a water supply and drainage system, a waste water treatment system in a rural village, a human waste treatment system, an industrial waste water treatment system, and the like.

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  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Molecular Biology (AREA)
  • Drying Of Solid Materials (AREA)
  • Treatment Of Sludge (AREA)
  • Filtration Of Liquid (AREA)
PCT/JP2006/312556 2005-06-21 2006-06-16 Method and apparatus for dehydrating and drying slurry WO2006137502A1 (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102092915A (zh) * 2010-12-07 2011-06-15 徐继开 污泥泵送式增压脱水机及污泥泵送式增压脱水法
EP2480506A1 (en) * 2009-09-23 2012-08-01 Kainuun Jätehuollon Kuntayhtymä Method for drying sludge
EP2636438A1 (de) * 2012-03-10 2013-09-11 LENSER Filtration GmbH Filterelement zum Einsatz als Kopf- oder Endelement für eine Filterpresse
JP2014004502A (ja) * 2012-06-21 2014-01-16 Unozawa Gumi Iron Works Ltd スラリー処理プラントの設計方法およびスラリー処理プラント
WO2019008224A1 (en) * 2017-07-06 2019-01-10 Lappeenrannan Teknillinen Yliopisto METHOD AND SYSTEM FOR ESTIMATING RESIDUAL LIQUID CONTENT AFTER A LIQUID REMOVAL PROCESS
CN111359276A (zh) * 2020-04-01 2020-07-03 安徽固德生物工程有限公司 一种乳酸酸解液的过滤方法

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4751739B2 (ja) * 2006-02-27 2011-08-17 株式会社宇野澤組鐵工所 脱水乾燥装置および脱水乾燥方法
TWI392538B (zh) * 2010-05-19 2013-04-11 Univ Nat Sun Yat Sen 具有電極之濾板組及使用該濾板組之壓濾機
TW201141664A (en) * 2010-05-27 2011-12-01 zong-yu Su Method of recycling and treating liquid with impurities
US20220184534A1 (en) * 2020-12-16 2022-06-16 Lifeng Li Pressure filter dewatering system and dewatering method
CN113443727B (zh) * 2021-06-18 2022-06-03 深圳市工勘岩土集团有限公司 洗车池污泥废水压滤处理装置

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US5558773A (en) * 1992-12-04 1996-09-24 Bertrams Dehydrat Ag Method for producing and drying a filter cake, while avoiding entering of the filter cake into a thermoplastic phase
EP0759318A1 (de) * 1995-08-16 1997-02-26 MUT Miljoevern-Umwelt-Technik GmbH Verfahren zum Entfeuchten und Trocknen von Feststoff/Flüssigkeits-Gemischen und Vorrichtung zur Durchführung des Verfahrens
EP0978304A2 (en) * 1998-08-03 2000-02-09 United States Filter Corporation Filter press with alternating diaphragm squeeze chamber plates and filtration chamber plates
WO2003013687A1 (en) * 2001-08-08 2003-02-20 Kwang-Soo An Filter press and filter press method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5558773A (en) * 1992-12-04 1996-09-24 Bertrams Dehydrat Ag Method for producing and drying a filter cake, while avoiding entering of the filter cake into a thermoplastic phase
EP0759318A1 (de) * 1995-08-16 1997-02-26 MUT Miljoevern-Umwelt-Technik GmbH Verfahren zum Entfeuchten und Trocknen von Feststoff/Flüssigkeits-Gemischen und Vorrichtung zur Durchführung des Verfahrens
EP0978304A2 (en) * 1998-08-03 2000-02-09 United States Filter Corporation Filter press with alternating diaphragm squeeze chamber plates and filtration chamber plates
WO2003013687A1 (en) * 2001-08-08 2003-02-20 Kwang-Soo An Filter press and filter press method

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2480506A1 (en) * 2009-09-23 2012-08-01 Kainuun Jätehuollon Kuntayhtymä Method for drying sludge
EP2480506A4 (en) * 2009-09-23 2013-03-06 Kainuun Jaetehuollon Kuntayhtymae PROCESS FOR DRYING SLUDGE
CN102092915A (zh) * 2010-12-07 2011-06-15 徐继开 污泥泵送式增压脱水机及污泥泵送式增压脱水法
CN102092915B (zh) * 2010-12-07 2012-12-05 徐继开 污泥泵送式增压脱水机及污泥泵送式增压脱水法
EP2636438A1 (de) * 2012-03-10 2013-09-11 LENSER Filtration GmbH Filterelement zum Einsatz als Kopf- oder Endelement für eine Filterpresse
JP2014004502A (ja) * 2012-06-21 2014-01-16 Unozawa Gumi Iron Works Ltd スラリー処理プラントの設計方法およびスラリー処理プラント
WO2019008224A1 (en) * 2017-07-06 2019-01-10 Lappeenrannan Teknillinen Yliopisto METHOD AND SYSTEM FOR ESTIMATING RESIDUAL LIQUID CONTENT AFTER A LIQUID REMOVAL PROCESS
CN111359276A (zh) * 2020-04-01 2020-07-03 安徽固德生物工程有限公司 一种乳酸酸解液的过滤方法

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JP2008546511A (ja) 2008-12-25
JP5478019B2 (ja) 2014-04-23
TW200708330A (en) 2007-03-01

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