A method for reducing the moisture content of filter cake of pressure filter

Abstract

The present invention relates to a method for reducing the moisture content of filter cake of a pressure filter. The pressure filter comprises a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit. The method comprises the following steps: step 1, conveying the slurry to the filtering unit for filtering and separation to obtain filter cake and mother liquor; step 2, conveying the filter cake of step 1 to the washing unit for washing; step 3, conveying the filter cake washed in step 2 to the primary drying unit and the secondary drying unit in sequence for drying; step 4, conveying the filter cake after the secondary drying in step 3 to the discharging unit for discharging; wherein the primary drying unit uses a fixed pressure gas to pass through the filter cake for drying, and the secondary drying unit uses a fixed flow gas to pass through the filter cake for drying. The method of the present invention can significantly reduce the consumption of drying gas, reduce the moisture content of the filter cake, and greatly reduce energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of a PTA pressure filter of a refining unit in PTA production and preparation, and in particular to a method for reducing the moisture content of a PTA pressure filter. Background Art

[0002] PTA is the main raw material for producing polyester fiber, resin, film and container resin, and is widely used in chemical fiber, container, packaging, film production and other fields. In recent years, the PTA process has developed rapidly, and with it, the PTA pressure filtration technology has developed rapidly. This technology integrates filtration, washing and pre-drying, greatly simplifying and shortening the PTA refining unit process. Pre-drying greatly reduces the moisture content in the filter cake, and it is continuous and stable, greatly reducing the load of the downstream drying section; the PTA pressure filtration technology adopts 1-stage filtration, 1-2-stage washing, 1-2-stage drying, and unloading process. The slurry is pressurized by the pump into the filter, filtered first, and then washed in the washing area after filtration. After washing, it is dried in the drying area, and after drying, it is unloaded in the unloading area. However, due to the influence of the drying medium, the number of times, the control method, and the inability to discharge the residual liquid in the drum filtrate pipeline in time, the moisture content of the filter cake discharge will be significantly higher, thereby increasing the load of the downstream drying section. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for reducing the moisture content of filter cakes of a pressure filter, so as to overcome the defect of high moisture content of filter cakes obtained by using a pressure filter in the prior art.

[0004] In order to achieve the above object, the present invention provides a method for reducing the moisture content of filter cake of a pressure filter, the pressure filter comprises a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit, and the method comprises the following steps:

[0005] Step 1, transporting the slurry to a filtration unit for filtration and separation to obtain a filter cake and a mother liquor;

[0006] Step 2, transporting the filter cake in step 1 to a washing unit for washing;

[0007] Step 3, conveying the filter cake washed in step 2 to a primary drying unit and a secondary drying unit in sequence for drying;

[0008] Step 4, transporting the filter cake after secondary drying in step 3 to a discharging unit for unloading;

[0009] The primary drying unit uses a fixed pressure gas to pass through the filter cake for drying, and the secondary drying unit uses a fixed flow gas to pass through the filter cake for drying.

[0010] The method for reducing the moisture content of filter cake of the pressure filter of the present invention, wherein the pressure of the fixed pressure gas is 0.2-0.6Mpa, and the volume flow rate of the fixed flow rate gas is 50-1000Nm 3 / h.

[0011] The method for reducing the moisture content of filter cake of a pressure filter described in the present invention, wherein the pressure filter also includes a mother liquor chamber, a washing filtrate chamber, a primary drying filtrate chamber and a secondary drying filtrate chamber, the mother liquor is transported to the mother liquor chamber through a pipeline, the washing filtrate is transported to the washing filtrate chamber through a pipeline, the primary drying filtrate is transported to the primary drying filtrate chamber through a pipeline, and the secondary drying filtrate is transported to the secondary drying filtrate chamber through a pipeline.

[0012] The method for reducing the moisture content of filter cake of a pressure filter described in the present invention, wherein the pressure filter also includes a residual liquid chamber, the residual liquid chamber includes a drain port, and the step 4 is: the filter cake after secondary drying is transported to a discharge unit, the secondary drying filtrate remaining in the pipeline is discharged through the drain port of the residual liquid chamber, and then the discharge gas enters the filtrate pipeline from the discharge gas port on the control head side to back-blow and discharge the filter cake.

[0013] The method for reducing the moisture content of filter cake of a pressure filter described in the present invention, wherein the pressure filter includes a frame, a drum and a control head, the drum is arranged between the frame and the control head, the drum rotates relative to the frame and the control head, the frame includes a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit, the control head includes a mother liquor chamber, a washing filtrate chamber, a primary drying filtrate chamber, a secondary drying filtrate chamber and a residual liquid chamber, the filtering unit, the washing unit, the primary drying unit, the secondary drying unit and the discharging unit are respectively arranged in a one-to-one correspondence with the mother liquor chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber.

[0014] The method for reducing the moisture content of filter cake of a pressure filter of the present invention, wherein the filter cake is formed in a drum unit, and a pipeline is provided at a position of the drum corresponding to any chamber of a mother liquor chamber, a washing filtrate chamber, a primary drying filtrate chamber, a secondary drying filtrate chamber and a residual liquid chamber, so that the mother liquor is transported to the mother liquor chamber through the pipeline, the washing filtrate is transported to the washing filtrate chamber through the pipeline, the primary drying filtrate is transported to the primary drying filtrate chamber through the pipeline, the secondary drying filtrate is transported to the secondary drying filtrate chamber through the pipeline, and the secondary drying filtrate remaining in the pipeline is transported to the residual liquid chamber.

[0015] The method for reducing the moisture content of filter cake of a pressure filter described in the present invention comprises the following steps: the filtering unit, the washing unit, the primary drying unit, the secondary drying unit and the unloading unit are separated by isolation blocks, respectively; and the mother liquor chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber are separated by isolation blocks, respectively.

[0016] In the method for reducing the moisture content of filter cake of a pressure filter of the present invention, the gas is an inert gas, other gas or steam.

[0017] In the method for reducing the moisture content of filter cake of a pressure filter of the present invention, the number of the liquid discharge port is at least one.

[0018] The method for reducing the moisture content of filter cake of a pressure filter described in the present invention, wherein the washing unit comprises a primary washing unit and a secondary washing unit, and in step 1 the filter cake is sequentially conveyed to the primary washing unit and the secondary washing unit for washing.

[0019] In the method for reducing the moisture content of filter cake of a pressure filter of the present invention, the washing liquid entering the washing unit chamber is a high-temperature liquid, and the high-temperature liquid refers to a liquid having a temperature higher than the standard boiling point.

[0020] Beneficial effects of the present invention:

[0021] 1. The present invention adopts two-stage drying. The first stage drying adopts a pressure control mode. Based on the principle of filtration, the liquid in the filter cake is pressed out by gas with a fixed pressure. At the same time, the details of the pressure setting can prevent the washing liquid in the adjacent area from leaking into the primary drying area, thereby reducing the load of the primary drying and reducing the moisture content of the product; the second stage drying adopts a flow control mode, and a large flow of gas is used to bring out the liquid in the filter cake under the action of pressure; the use of two different drying control modes can achieve the purpose of reducing the moisture content of the filter cake under the premise of consuming less total amount of gas.

[0022] 2. The present invention sets a drain port in the residual liquid chamber to ensure that after secondary drying, the secondary drying filtrate and tail gas that are not completely discharged in the pipeline connecting the unloading unit are discharged in time at the drain port, and will not flow back into the dried filter cake with the backwash gas, thereby reducing the moisture content of the filter cake.

[0023] 3. The present invention sets a back pressure in the drying gas-liquid tank, which can avoid flash evaporation of the discharged high-temperature liquid on the one hand, and on the other hand, control the pressure difference before and after drying by setting the back pressure, avoiding uneven gas distribution and local gas short circuit during the drying process of the drying gas penetrating the filter cake, thereby reducing the moisture content of the filter cake and improving the drying effect.

[0024] 4. The present invention uses washing water above 140°C to ensure that the temperature of the filter cake is also around 140°C, so that part of the liquid can be evaporated through pressure relief flash evaporation in the unloading area, thereby reducing the moisture content of the filter cake and improving the drying effect.

[0025] 5. The present invention improves the pre-drying technology of the pressure filter from the aspects of process flow, control mode and equipment structure, thereby significantly reducing the consumption of drying gas, reducing the moisture content of the filter cake, and greatly reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a schematic diagram of a process for reducing the moisture content of filter cake of a pressure filter according to an embodiment of the present invention.

[0027] Figure 2 This is a simplified schematic diagram of a pressure filter in one embodiment of the present invention.

[0028] Wherein, the reference numerals are:

[0029] 1—Pressure filter

[0030] 2—Mother liquid tank

[0031] 3—Washing filtrate tank

[0032] 4—Dry gas and liquid tank

[0033] 5—Mother liquid pump

[0034] 6—Washing filtrate pump

[0035] 7—Dry filtrate pump

[0036] 8—Residual liquid tank

[0037] 9—Primary drying gas control valve

[0038] 10—Secondary drying gas control valve

[0039] 11—Framework

[0040] 12—Filter unit

[0041] 13—Mother Liquid Chamber

[0042] 14—Isolation Block

[0043] 15—Isolation Block

[0044] 16—Control Head

[0045] 17—One-time washing unit

[0046] 18 - Isolation Block

[0047] 19—Primary washing filtrate chamber

[0048] 20—Secondary washing unit

[0049] 21—Isolation Block

[0050] 22—Secondary washing filtrate chamber

[0051] 23—Isolation Block

[0052] 24—Isolation Block

[0053] 25—primary drying unit

[0054] 26—Primary drying filtrate chamber

[0055] 27—Pipeline

[0056] 28 - Isolation Block

[0057] 29—Isolation Block

[0058] 30—Secondary Drying Unit

[0059] 31—Secondary drying filtrate chamber

[0060] 32—Isolation Block

[0061] 33 - Isolation Block

[0062] 34—Unloading unit

[0063] 35—Residual liquid chamber

[0064] 36 - Isolation Block

[0065] 37—Isolation Block

[0066] 38—Drain port DETAILED DESCRIPTION

[0067] The following is a detailed description of the embodiments of the present invention. The embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The experimental methods in the following embodiments where specific conditions are not specified are usually based on conventional conditions.

[0068] The present invention provides a method for reducing the moisture content of filter cake of a pressure filter, wherein the pressure filter comprises a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit, and the method comprises the following steps:

[0069] Step 1, transporting the PTA slurry to a filtration unit for filtration and separation to obtain a filter cake and a mother liquor;

[0070] Step 2, transporting the filter cake in step 1 to a washing unit for washing;

[0071] Step 3, conveying the filter cake washed in step 2 to a primary drying unit and a secondary drying unit in sequence for drying;

[0072] Step 4, transporting the filter cake after secondary drying in step 3 to a discharging unit for unloading;

[0073] The primary drying unit uses a fixed pressure gas to pass through the filter cake for drying, and the secondary drying unit uses a fixed flow gas to pass through the filter cake for drying.

[0074] The pressure filter of the present invention adopts two-stage drying. The first stage of drying adopts a pressure control mode. Based on the principle of filtration, a gas with a fixed pressure is used to press out the liquid in the filter cake to reduce the moisture content of the product. The second stage of drying adopts a flow control mode. A large flow of gas is used to bring out the liquid in the filter cake under the action of pressure. By adopting two different drying control modes, the purpose of reducing the moisture content of the filter cake can be achieved under the premise of consuming a relatively small total amount of gas.

[0075] The present invention does not particularly limit the type of slurry, as long as it is a suspension formed by a mixture of solid and liquid, such as PTA slurry. The present invention does not particularly limit the specific structure of the pressure filter, such as a pressure filter commonly used in the art. The pressure filter of the present invention includes a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit. The slurry is transported to the filtering unit for filtering and separation to form a filter cake, and then the filter cake passes through the washing unit, the primary drying unit, the secondary drying unit and the discharging unit in sequence.

[0076] The primary drying unit of the present invention uses a fixed pressure gas to pass through the filter cake for drying. In one embodiment, the pressure of the fixed pressure gas is 0.2-0.6Mpa; the secondary drying unit of the present invention uses a fixed flow gas to pass through the filter cake for drying. In one embodiment, the volume flow rate of the fixed flow gas is 50-1000Nm 3 / h. The present invention can further reduce the amount of drying gas while achieving the purpose of drying by optimizing the pressure and flow rate. For example, compared with using a fixed pressure gas or a fixed flow rate gas for both drying operations, the amount of gas can be saved by 20%.

[0077] The present invention does not specifically limit the drying gas, and it can be, for example, an inert gas, other gas or steam, and other gas can be, for example, compressed air; it can be a normal temperature gas or a high temperature gas. The drying gas used in the primary drying unit and the secondary drying unit of the present invention can be the same or different, and the present invention does not specifically limit it.

[0078] In one embodiment, the PTA pressure filter of the present invention includes a frame, a drum and a control head, the frame is, for example, a cylindrical hollow structure, and is divided into a plurality of regions along the circumferential direction, namely, a filtration unit, a washing unit, a primary drying unit, a secondary drying unit and a discharge unit, and two adjacent units are separated by an isolation block. The drum is, for example, a cylindrical hollow structure, and the control head is, for example, a cylinder. The drum is arranged between the frame and the control head, and rotates relative to the frame and the control head, for example, the drum is sleeved on the control head and the frame. The control head is divided into a plurality of regions along the circumferential direction, namely, a mother liquor chamber, a washing filtrate chamber, a primary drying filtrate chamber, a secondary drying filtrate chamber and a residual liquid chamber, and two adjacent chambers are separated by an isolation block, and the mother liquor chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber are respectively arranged in a one-to-one correspondence with the filtration unit, the washing unit, the primary drying unit, the secondary drying unit and the discharge unit.

[0079] Wherein, after the PTA slurry passes through the frame, a filter cake is formed on the drum, and the mother liquor enters the mother liquor chamber of the control head after passing through the drum. The drum of the present invention is provided with a pipeline corresponding to the position of any chamber of the mother liquor chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber, so that the mother liquor is transported to the mother liquor chamber through the pipeline, the washing filtrate is transported to the washing filtrate chamber through the pipeline, the primary drying filtrate is transported to the primary drying filtrate chamber through the pipeline, the secondary drying filtrate is transported to the secondary drying filtrate chamber through the pipeline, and the secondary drying filtrate remaining in the pipeline is transported to the residual liquid chamber.

[0080] In detail, the liquid flowing through the area of ​​the drum corresponding to the mother liquid chamber is transported to the mother liquid chamber through the pipeline, the liquid flowing through the area of ​​the drum corresponding to the washing filtrate chamber is transported to the washing filtrate chamber through the pipeline, the liquid flowing through the area of ​​the drum corresponding to the primary drying filtrate chamber is transported to the primary drying filtrate chamber through the pipeline, and the liquid flowing through the area of ​​the drum corresponding to the secondary drying filtrate chamber is transported to the secondary drying filtrate chamber through the pipeline. In one embodiment, the pipeline is arranged on the inner cylinder of the drum in contact with the control head.

[0081] The pressure filter of the present invention makes the filter cakes in each area of ​​the drum pass through the filtering unit, washing unit, primary drying unit, secondary drying unit and unloading unit in sequence through the rotation of the drum, and the pipeline connected to the drum will also flow through the mother liquor, washing filtrate, primary drying filtrate and secondary drying filtrate in sequence. When the filter cake in a certain area of ​​the drum rotates to the corresponding unloading unit and residual liquid chamber, the residual liquid of the secondary drying filtrate will be stored in the pipeline connected to the drum in this area. The present invention sets a drain port in the residual liquid chamber, so that the residual secondary drying filtrate in the pipeline can be discharged through the drain port of the residual liquid chamber, and then the unloading gas enters the drum filtrate pipe from the unloading gas port on the control head side to back-blow the filter cake for unloading, so as to avoid the residual liquid being back-blown to the filter cake, resulting in a high moisture content of the filter cake.

[0082] The present invention does not impose any particular limitation on the number of the liquid discharge ports, which may be one or more, as long as they are disposed in the residual liquid chamber.

[0083] In one embodiment, the pressure filter of the present invention further comprises a mother liquid tank, a washing filtrate tank and a drying gas-liquid tank. The mother liquid tank is connected to the mother liquid chamber to transport the mother liquid to the mother liquid tank through the mother liquid chamber; the washing filtrate tank is connected to the washing filtrate chamber to transport the washing filtrate to the washing filtrate tank through the washing filtrate chamber; the drying gas-liquid tank is connected to the primary drying filtrate chamber and the secondary drying filtrate chamber to transport the primary drying filtrate and the secondary drying filtrate to the drying gas-liquid tank through the primary drying filtrate chamber and the secondary drying filtrate chamber. In another embodiment, the drying gas-liquid tank can be set with a back pressure, which can avoid flash evaporation of the discharged high-temperature liquid on the one hand, and on the other hand, by setting the back pressure, the pressure difference before and after drying is controlled, and the uneven distribution of gas and the local short circuit of gas during the drying process of the drying gas penetrating the filter cake are avoided, thereby reducing the moisture content of the filter cake and improving the drying effect.

[0084] In one embodiment, the pressure filter of the present invention further comprises a residual liquid tank which is in communication with the residual liquid chamber so as to transport the secondary drying filtrate remaining in the pipeline to the residual liquid tank through the discharge port of the residual liquid chamber.

[0085] In one embodiment, the washing unit of the present invention includes a primary washing unit and a secondary washing unit, and the filter cake in step 1 is sequentially transported to the primary washing unit and the secondary washing unit for washing. Accordingly, the washing filtrate chamber includes a primary washing filtrate chamber and a secondary washing filtrate chamber, the primary washing filtrate flows into the primary washing filtrate chamber, and the secondary washing filtrate flows into the secondary washing filtrate chamber.

[0086] In one embodiment, the method for reducing the moisture content of filter cake of the pressure filter of the present invention is used to reduce the moisture content of the filter cake formed by PTA slurry, such as Figure 1 and Figure 2 As shown, the following steps are included:

[0087] (1) The PTA slurry in the PTA slurry tank is pressurized by a slurry pump and enters the pressure filter 1, and enters the filter unit 12 through the feed area of ​​the frame 11 of the pressure filter 1 for filtration and separation, and obtains mother liquor, pipeline residual mother liquor (referring to the mother liquor remaining in the pipeline 27) and filter cake respectively. The filter cake is formed on the drum; the mother liquor passing through the drum enters the mother liquor tank 2 through the mother liquor chamber 13 of the control head 16 of the pressure filter 1, and is output through the mother liquor pump 5 connected to the mother liquor tank 2; the pipeline residual mother liquor enters the next chamber of the control head 16 as the drum rotates, that is, the primary washing filtrate chamber 19.

[0088] (2) The filter cake is transported to the primary washing unit 17, and the primary washing water is pressurized by the washing water pump and enters the primary washing unit 17 of the frame 11 for washing, thereby obtaining the primary washing filtrate, the primary washing filtrate remaining in the pipeline, and the filter cake after the primary washing respectively; the primary washing filtrate flowing through the drum enters the washing filtrate tank 3 through the primary washing filtrate chamber 19 of the control head 16, and is output through the washing filtrate pump 6 connected to the washing filtrate tank 3; the primary washing filtrate remaining in the pipeline enters the next chamber of the control head 16 as the drum rotates, namely, the secondary washing filtrate chamber 22.

[0089] (3) As the drum rotates, the filter cake after primary washing is transported to the secondary washing unit 20, and the secondary washing water is pressurized by the washing water pump and enters the secondary washing unit 20 of the frame 11 for washing, thereby obtaining a secondary washing filtrate, a secondary washing filtrate remaining in the pipeline, and a filter cake after secondary washing, respectively; the secondary washing filtrate enters the washing filtrate tank 3 through the secondary washing filtrate chamber 22 of the control head 16, and is output through the washing filtrate pump 6 connected to the washing filtrate tank 3; the secondary washing filtrate remaining in the pipeline enters the next chamber of the control head, i.e., the primary drying filtrate chamber 26, as the drum rotates.

[0090] (4) As the drum rotates, the filter cake after secondary washing is transported to the primary drying unit 25 for primary drying, and the pressurized drying gas enters the primary drying unit 25 of the frame 11 through the primary drying gas control valve 9 to obtain primary drying filtrate, primary drying tail gas, primary drying filtrate remaining in the pipeline, primary drying tail gas remaining in the pipeline and filter cake after primary drying; the primary drying filtrate and the primary drying tail gas both enter the drying gas-liquid tank 4 through the primary drying filtrate chamber 26 of the control head 16; the primary drying filtrate remaining in the pipeline and the primary drying tail gas remaining in the pipeline enter the next chamber of the control head 16, i.e., the secondary drying filtrate chamber 31, as the drum rotates.

[0091] The drying gas may be an inert gas, other gases or steam; the control mode of the primary drying gas control valve 9 adopts pressure control, and the primary drying gas control valve is set so that the drying gas pressure is the same as or slightly higher than the pressure of the adjacent secondary washing unit 20, so that the liquid in the secondary washing unit 20 will not leak to the primary drying unit 20 under the action of the pressure difference, thereby reducing the workload of the primary drying unit 20; the drying gas-liquid tank 4 can be set with a back pressure, so that the discharged high-temperature drying gas and liquid will not flash, and there will be no short circuit when the drying gas penetrates the filter cake, thereby improving the drying effect.

[0092] (5) As the drum rotates, the filter cake after primary drying is transported to the secondary drying unit 30, and the pressurized drying gas enters the secondary drying unit 30 of the frame 11 through the secondary drying gas control valve 10 for secondary drying, thereby obtaining secondary drying filtrate, secondary drying tail gas, secondary drying filtrate remaining in the pipeline, secondary drying tail gas remaining in the pipeline, and filter cake after secondary drying respectively; the secondary drying filtrate and the secondary drying tail gas both enter the drying gas-liquid tank 4 through the secondary drying filtrate chamber 31 of the control head 16; the secondary drying filtrate remaining in the pipeline and the secondary drying tail gas remaining in the pipeline enter the next chamber of the control head 16, i.e., the residual liquid chamber 35, as the drum rotates, and are discharged through the drain port 38 on the residual liquid chamber 35.

[0093] The drying gas medium may be an inert gas or other gas; the control mode of the secondary drying gas control valve 10 adopts flow control, and the control valve drying gas flow rate is set, and a large drying gas flow rate is used to remove the residual filtrate in the filter cake, thereby reducing the liquid content in the filter cake; the drying gas-liquid tank 4 is set with a back pressure, so that the discharged high-temperature drying gas and liquid will not flash, and there will be no short circuit when the drying gas penetrates the filter cake, thereby improving the drying effect; the drain port 38 discharges the residual secondary drying filtrate and the residual secondary drying tail gas in the pipeline, so as to avoid the residual secondary drying filtrate and the residual secondary drying tail gas in the pipeline being blown back into the filter cake under the action of the unloading gas and the back-blowing gas, thereby increasing the liquid content in the filter cake, and then increasing the moisture content of the filter cake.

[0094] (6) After the secondary drying is completed, as the drum rotates, the filter cake enters the unloading unit 34 of the frame 11, and the unloading gas and back-blowing gas enter from the unloading gas port and back-blowing gas port of the control head 16 to back-blow the filter cake, and the filter cake is unloaded to the downstream equipment for output.

[0095] In one embodiment, the isolation blocks 14, 18, 23, 28, 33, and 37 divide the frame 11 into the filtering unit 12, the primary washing unit 17, the secondary washing unit 20, the primary drying unit 25, the secondary drying unit 30, and the unloading unit 34. The isolation blocks 15, 21, 24, 29, 32, and 36 divide the control head 16 into the mother liquid chamber 13, the primary washing filtrate chamber 19, the secondary washing filtrate chamber 22, the primary drying filtrate chamber 26, the secondary drying filtrate chamber 31, and the residual liquid chamber 35. The isolation blocks 14, 18, 23, 28, 33, and 37 are arranged one by one with the isolation blocks 15, 21, 24, 29, 32, and 36.

[0096] In one embodiment, the primary drying gas control valve 9 and the secondary drying gas control valve 10 are pneumatic regulating valves, electric regulating valves or other valves with regulating and controlling functions.

[0097] The washing water of the present invention can be washing water above 140°C, so that the temperature of the filter cake can be ensured to be around 140°C, so that part of the liquid can be evaporated through pressure relief flash evaporation in the unloading area, thereby reducing the moisture content of the filter cake and improving the drying effect.

[0098] The present invention provides a method for reducing the moisture content of filter cakes of pressure filters, which is particularly suitable for PTA slurry and can be used in the pressure filtration process of the PTA slurry refining unit. A two-stage drying process is designed in terms of the process flow, and pressure control and flow control are respectively adopted in the control mode of the two-stage drying to effectively reduce the amount of drying gas and the drying load. Back pressure is set in the drying gas-liquid tank to avoid flash evaporation and short circuit of the drying gas, and a discharge hole is designed in the control head unloading area to avoid the residual liquid in the filtrate tube after drying from reversely entering the dried filter cake, thereby achieving the purpose of reducing the moisture content of the filter cake. The present invention is characterized in that the pre-drying technology of the pressure filter is improved from three aspects of process flow, control principle and equipment structure through calculation, thereby significantly reducing the consumption of drying gas, reducing the moisture content of the filter cake, and greatly reducing energy consumption. By adopting the method of the present invention, the moisture content in the obtained filter cake can be further reduced from the previous ~10wt% to within ~7.5wt%, which has a significant effect.

[0099] The method of the present invention is not only applicable to PTA slurry, but also applicable to the separation and pre-drying of other solid-liquid mixed slurries.

[0100] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for reducing the moisture content of filter cake of a pressure filter, characterized in that: The pressure filter comprises a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit. The method comprises the following steps: Step 1, transporting the slurry to a filtration unit for filtration and separation to obtain a filter cake and a mother liquor; Step 2, transporting the filter cake in step 1 to a washing unit for washing; Step 3, conveying the filter cake washed in step 2 to a primary drying unit and a secondary drying unit in sequence for drying; Step 4, conveying the filter cake after secondary drying in step 3 to a discharging unit for unloading; Wherein, the primary drying unit uses a fixed pressure gas to pass through the filter cake to dry, and the secondary drying unit uses a fixed flow gas to pass through the filter cake to dry; The pressure filter also includes a mother liquor chamber, a washing filtrate chamber, a primary drying filtrate chamber and a secondary drying filtrate chamber, the mother liquor is transported to the mother liquor chamber through a filtrate pipeline, the washing filtrate is transported to the washing filtrate chamber through a filtrate pipeline, the primary drying filtrate is transported to the primary drying filtrate chamber through a filtrate pipeline, and the secondary drying filtrate is transported to the secondary drying filtrate chamber through a filtrate pipeline; The pressure filter also includes a residual liquid chamber, and the residual liquid chamber includes a drain port. The step 4 is: the filter cake after secondary drying is transported to the discharge unit, and the secondary drying filtrate remaining in the filtrate pipeline is discharged through the drain port of the residual liquid chamber, and then the discharge gas enters the filtrate pipeline from the discharge gas port on the control head side to back-blow and discharge the filter cake; The pressure filter comprises a frame, a drum and a control head, the drum is arranged between the frame and the control head, the drum rotates relative to the frame and the control head, the frame comprises a filtering unit, a washing unit, a primary drying unit, a secondary drying unit and a discharging unit, the control head comprises a mother liquid chamber, a washing filtrate chamber, a primary drying filtrate chamber, a secondary drying filtrate chamber and a residual liquid chamber, the filtering unit, the washing unit, the primary drying unit, the secondary drying unit and the discharging unit are arranged one by one corresponding to the mother liquid chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber respectively; The liquid flowing through the area of ​​the drum corresponding to the mother liquor chamber is transported to the mother liquor chamber through the pipeline, the liquid flowing through the area of ​​the drum corresponding to the washing filtrate chamber is transported to the washing filtrate chamber through the pipeline, the liquid flowing through the area of ​​the drum corresponding to the primary drying filtrate chamber is transported to the primary drying filtrate chamber through the pipeline, and the liquid flowing through the area of ​​the drum corresponding to the secondary drying filtrate chamber is transported to the secondary drying filtrate chamber through the pipeline.

2. The method for reducing the moisture content of filter cake of a pressure filter according to claim 1, characterized in that: The pressure of the fixed-pressure gas is 0.2-0.6Mpa, and the volume flow rate of the fixed-flow gas is 50-1000Nm³ / h.

3. The method for reducing the moisture content of filter cake of a pressure filter according to claim 1, characterized in that: The filter cake is formed in the drum unit, and the drum is provided with pipelines at positions corresponding to any chamber of the mother liquor chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber, so that the mother liquor is transported to the mother liquor chamber through the pipeline, the washing filtrate is transported to the washing filtrate chamber through the pipeline, the primary drying filtrate is transported to the primary drying filtrate chamber through the pipeline, the secondary drying filtrate is transported to the secondary drying filtrate chamber through the pipeline, and the secondary drying filtrate remaining in the pipeline is transported to the residual liquid chamber.

4. The method for reducing the moisture content of filter cake of a pressure filter according to claim 1, characterized in that: The filtering unit, the washing unit, the primary drying unit, the secondary drying unit and the unloading unit are separated by isolation blocks, and the mother liquor chamber, the washing filtrate chamber, the primary drying filtrate chamber, the secondary drying filtrate chamber and the residual liquid chamber are separated by isolation blocks.

5. The method for reducing moisture content of filter cake of a pressure filter according to claim 1, characterized in that: The method is used for separating solid-liquid mixed slurry; the washing unit comprises a primary washing unit and a secondary washing unit, and the filter cake in step 1 is sequentially transported to the primary washing unit and the secondary washing unit for washing.

6. The method for reducing moisture content of filter cake of a pressure filter according to claim 1, characterized in that: The number of the liquid discharge port is at least one.

7. The method for reducing the moisture content of filter cake of a pressure filter according to claim 1, characterized in that: The pressure filter also includes a mother liquid tank, a washing filtrate tank and a drying gas-liquid tank; the mother liquid tank is connected to the mother liquid chamber to transport the mother liquid to the mother liquid tank through the mother liquid chamber; the washing filtrate tank is connected to the washing filtrate chamber to transport the washing filtrate to the washing filtrate tank through the washing filtrate chamber; the drying gas-liquid tank is connected to the primary drying filtrate chamber and the secondary drying filtrate chamber to transport the primary drying filtrate and the secondary drying filtrate to the drying gas-liquid tank through the primary drying filtrate chamber and the secondary drying filtrate chamber; the drying gas-liquid tank sets a back pressure.

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