Separating and filtering method applied to ammoximation reaction liquid

Abstract

The invention provides a separation and filtration method applied to an ammoximation reaction liquid, and belongs to the technical field of ammoximation reaction liquid separation, and the separation and filtration method comprises the following steps: dispersing an ammoximation feed liquid containing a catalyst in a reaction kettle; after dispersion, the ammoximation feed liquid containing the catalyst enters a front cross-flow filter; at least two front cross-flow filters are arranged in parallel, and each front cross-flow filter is positioned outside the reaction kettle; an ammoximation feed liquid containing a catalyst flows through the tubular filter element at a preset flow speed in the front cross-flow filter, and a filter cake filter layer with a preset thickness is formed on the inner circumferential wall of the tubular filter element; the filtered clear liquid is discharged from the side part of the front cross-flow filter, and the filtered thick slurry enters a circulating pump from a filter circulating material outlet in the bottom of the front cross-flow filter and flows back to the reaction kettle under the action of the circulating pump; according to the arrangement, the online operation period of the front cross-flow filter can be prolonged, and the pressure needed during back flushing can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of separation of ammoximation reaction liquid, and in particular relates to a separation and filtration method applied to ammoximation reaction liquid. Background Art

[0002] Caprolactam (CPL) is an important organic chemical raw material and a monomer for synthetic fibers and engineering plastics. It is mainly used to produce polyamide engineering plastics and polyamide fibers, and is an important chemical raw material in short supply in the Chinese market. At present, caprolactam is mainly obtained from cyclohexanone oxime through rearrangement reaction, and the production process of cyclohexanone oxime mainly relies on the chemical catalytic reaction of hydrogen peroxide, ammonia and cyclohexanone under the action of titanium silicon molecular sieve catalyst, and then relies on filtering technology to separate the oximation reaction liquid from the titanium silicon molecular sieve catalyst. The titanium silicon molecular sieve catalyst continues to stay in the ammoximation reaction system to participate in the chemical reaction, and the filtered clear liquid containing cyclohexanone oxime exits the system.

[0003] At present, there are two main filtering methods for ammonia oxime reaction liquid filtration technology. One is the built-in filtering technology that arranges the filter element in the reactor, and the other is the external cross-flow membrane filtration technology that places the filter after the circulation pump (on the circulation pipeline).

[0004] Both of the above technologies have some problems: the operating cycle of the built-in membrane filtration technology is greatly affected by the filtering effect of the filter element. Once the filter element is contaminated, it is necessary to stop the machine and replace the filter element; the specific process is: after the reactor stops feeding, cooling, depressurizing, discharging, and cleaning, enter the reactor to remove the filter elements one by one, install new filter elements, and then restart the machine after feeding; the operating cycle of this filtration technology is affected by many factors, such as the filtration accuracy of the membrane element, the filling area of ​​the membrane element, the membrane filtration load, the stabilizer in the hydrogen peroxide, the catalyst concentration, and the catalyst particle size, all of which have a great impact on the operating cycle of the device.

[0005] The existing ammonia oxime external cross-flow membrane filtration technology arranges the filter component after the circulation pump, and multiple filter components are connected in series and parallel. The parallel connection increases the circulation volume of the circulation pump, and the multi-stage series connection increases the head of the circulation pump, resulting in an increase in the cost and operation cost of the circulation pump. At the same time, the higher head makes the subsequent pre-cross-flow filter filtration pressure difference higher, increasing the risk of filter element clogging. Summary of the invention

[0006] The embodiment of the present invention provides a separation and filtration method applied to an ammoximation reaction liquid, aiming to reduce the risk of filter element clogging and to extend the operation cycle of the filtration equipment.

[0007] To achieve the above object, the technical solution adopted by the present invention is: Provided is a separation and filtration method for an ammoximation reaction liquid, comprising the following steps: The ammoximation liquid containing the catalyst is dispersed in the reactor; after being dispersed, the ammoximation liquid containing the catalyst enters the pre-cross-flow filter; the pre-cross-flow filters are at least two arranged in parallel, and each pre-cross-flow filter is located outside the reactor; The ammoximation liquid containing the catalyst flows through the tubular filter element at a preset flow rate in the pre-cross-flow filter, and during the flow, a filter cake filtration layer of a preset thickness is formed on the inner peripheral wall of the tubular filter element; The filtered clear liquid is discharged from the side of the pre-cross-flow filter, and the filtered concentrated slurry enters the circulation pump from the filter circulation material outlet at the bottom of the pre-cross-flow filter, and flows back to the reactor under the action of the circulation pump.

[0008] In a possible implementation, a heat exchanger and a pipeline mixer are connected in sequence to the pipeline between the discharge end of the circulation pump and the circulating material reflux port of the reactor. Under the action of the circulation pump, the filtered concentrated slurry flows back to the reactor after passing through the heat exchanger and the pipeline mixer.

[0009] In a possible implementation, at the beginning of startup, the pre-cross-flow filter is disconnected from the reactor and the circulation pump respectively, the clear liquid outlet valve and the backwash inlet valve of the pre-cross-flow filter are closed, and the discharge port at the bottom of the reactor is connected to the liquid suction end of the circulation pump through a pipeline; Start the reactor and the circulation pump so that the mixed liquid in the reactor can circulate; when the mixed liquid in the reactor meets the filtering requirements, close the discharge port at the bottom of the reactor, connect the pre-cross-flow filter with the reactor and the circulation pump, and open the clear liquid outlet valve of the pre-cross-flow filter to filter the mixed liquid.

[0010] In a possible implementation, the clear liquid outlet of each pre-cross-flow filter is connected to the clear liquid main pipeline through a branch pipe, and the clear liquid main pipeline is connected to a regulating valve for regulating the outflow of the clear liquid.

[0011] In a possible implementation, when one of the pre-cross-flow filters needs to be backwashed, the clear liquid outlet valve of the pre-cross-flow filter is closed, and the backwash inlet valve of the pre-cross-flow filter is opened; During backwashing, the pressure of the backwashing medium is higher than the pressure of the mixed liquid in the tubular filter element. The backwashing medium enters the tubular filter element from the outside and mixes with the mixed liquid. The filter cake filter layer on the inner wall of the tubular filter element separates from the tubular filter element and flows out of the front cross-flow filter with the mixed liquid. After the backwash is completed, close the backwash inlet valve of the pre-cross-flow filter and open the clear liquid outlet valve of the pre-cross-flow filter.

[0012] In a possible implementation, the front cross-flow filter is a single-stage backwash or a multi-stage backwash; when the front cross-flow filter is a multi-stage backwash, a plurality of backwash inlets are provided along the axial direction of the front cross-flow filter.

[0013] In a possible implementation, when the diameter of the pre-cross-flow filter is greater than a preset diameter, a plurality of backflushing inlets are arranged along the circumference of the pre-cross-flow filter.

[0014] In a possible implementation, a recoil baffle aligned with the recoil inlet is provided on the inner peripheral wall of the pre-cross-flow filter, and during the backwashing process, the recoil medium flows in a preset direction under the action of the recoil baffle.

[0015] In a possible implementation, when one of the pre-cross-flow filters needs to be repaired, the pre-cross-flow filter inlet valve, the pre-cross-flow filter outlet valve, the clear liquid outlet valve, and the backwash inlet valve are closed.

[0016] The present invention provides a separation and filtration method for ammoximation reaction liquid, which has the following beneficial effects: 1. Compared with the method of setting the filter membrane in the reactor, the present invention can cut out one of the pre-cross-flow filters from the system for maintenance without stopping the reactor, which provides a guarantee for the long-term stable operation of the ammoximation device.

[0017] 2. Compared with the arrangement of the pre-cross-flow filter after the circulation pump, the present invention arranges the pre-cross-flow filter before the circulation pump, which can make the filter operating pressure lower, reduce the filtration pressure difference, and reduce the probability of rapid clogging and contamination of the filter element due to the large pressure difference. It can effectively reduce the recoil frequency, extend the online operation period of the pre-cross-flow filter, and also reduce the pressure required for recoil.

[0018] 3. The pre-cross-flow filter is arranged before the circulating pump to reduce the head of the circulating pump. At the same time, it can reduce the pipeline flow rate of the tubular filter element under the premise of ensuring the filtering capacity, thereby reducing the circulation volume of the circulating pump and reducing the overall cost and operating energy consumption of the circulating pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A structural diagram of a separation and filtration method for an ammoximation reaction liquid provided in an embodiment of the present invention Figure 1 ; Figure 2 A schematic diagram of the structure of a reactor for a separation and filtration method of an ammoximation reaction liquid provided in an embodiment of the present invention; Figure 3 A schematic diagram of the structure of a pre-cross-flow filter used in a separation and filtration method for an ammoximation reaction liquid provided in an embodiment of the present invention; Figure 4 A schematic diagram of a multi-stage backwash of a pre-cross-flow filter applied to a separation and filtration method of an ammoximation reaction liquid provided in an embodiment of the present invention; Figure 5 A schematic diagram of the arrangement of the same-plane backwash inlet of a pre-cross-flow filter in a separation and filtration method for an ammoximation reaction liquid provided in an embodiment of the present invention.

[0020] Description of reference numerals: 1, reactor; 2, front cross-flow filter; 3, circulation pump; 4, heat exchanger; 5, pipeline mixer; 1a, reactor shell; 1b, side circulation material outlet; 1c, circulation material reflux port; 1d, discharge port; 2a, circulation material inlet; 2b, filter circulation material outlet; 2c, clear liquid outlet; 2d, backwash inlet; 2e, distributor; 2f, upper tube sheet; 2g, lower tube sheet; 2h, tubular filter element; 2i, Backwash baffle; G1, pre-cross flow filter inlet pipeline; G2, pre-cross flow filter outlet pipeline; G3, circulating pump feed pipeline; G4, heat exchanger inlet pipeline; G5, heat exchanger outlet pipeline; G6, reactor reflux pipeline; G7, clear liquid main pipeline; G8, backwash pipeline; V1, pre-cross flow filter inlet valve; V2, pre-cross flow filter outlet valve; V3, clear liquid outlet valve; V4, backwash inlet valve; V5, regulating valve. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] Please also read Figures 1 to 5 Now, a separation and filtration method for ammoximation reaction liquid provided by the present invention is described. The separation and filtration method for ammoximation reaction liquid comprises the following steps: The ammoximation liquid containing the catalyst is dispersed in the reactor 1; after dispersion, the ammoximation liquid containing the catalyst enters the pre-cross-flow filter 2; there are at least two pre-cross-flow filters 2 arranged in parallel, and each pre-cross-flow filter 2 is located outside the reactor 1; the ammoximation liquid containing the catalyst flows through the tubular filter element 2h at a preset flow rate in the pre-cross-flow filter 2, and during the flow, a filter cake filtration layer of a preset thickness is formed on the inner wall of the tubular filter element 2h; the filtered clear liquid is discharged from the side of the pre-cross-flow filter 2, and the filtered concentrated slurry enters the circulation pump 3 from the filter circulation material outlet 2b at the bottom of the pre-cross-flow filter 2, and flows back to the reactor 1 under the action of the circulation pump 3; the reactor 1 has a reactor shell 1a.

[0023] The present invention provides a separation and filtration method for ammoximation reaction liquid. Compared with the method in which the filter membrane is arranged in the reactor 1, the present invention can cut out one of the pre-cross-flow filters 2 from the system for maintenance without stopping the reactor, which provides a guarantee for the long-term stable operation of the ammoximation device. Compared with the pre-cross-flow filter 2 being arranged after the circulation pump 3, the present invention arranges the pre-cross-flow filter 2 before the circulation pump 3, which can make the filter operation pressure lower, reduce the filtration pressure difference, reduce the probability of rapid blockage and pollution of the tubular filter element 2h due to the large pressure difference, effectively reduce the frequency of recoil, extend the online operation cycle of the pre-cross-flow filter 2, and also reduce the pressure required for recoil; the pre-cross-flow filter 2 is arranged before the circulation pump 3 to reduce the head of the circulation pump 3, and at the same time, the pipeline flow rate of the tubular filter element 2h can be reduced under the premise of ensuring the filtering capacity, thereby reducing the circulation volume of the circulation pump 3, and reducing the cost and operation energy consumption of the circulation pump 3 as a whole.

[0024] It should be noted that the ammoximation liquid containing the catalyst flows in the tubular filter element 2h at a preset flow rate in the pre-cross-flow filter 2, so that a filter cake layer of a preset thickness can be formed on the inner wall of the tubular filter element 2h, and the filter cake layer is relatively loose and has good permeability.

[0025] Exemplarily, a filtration system applied to an ammoximation reaction liquid includes a reactor 1, a pre-cross-flow filter 2, a circulation pump 3, a heat exchanger 4 and a pipeline mixer 5; the reactor 1 is provided with a circulation material reflux port 1c on the top, a discharge port 1d on the bottom, and at least two side circulation material outlets 1b on the side; the pre-cross-flow filter 2 is provided with a circulation material inlet 2a on the top, and the circulation material inlet 2a is connected to the side circulation material outlet 1b through a pre-cross-flow filter inlet pipeline G1, and a pre-cross-flow filter inlet valve V1 is provided on the pre-cross-flow filter inlet pipeline G1; the pre-cross-flow filter is provided with a filter circulation material outlet 2b at the bottom, and the filter circulation material outlet 2b is connected to a pre-cross-flow filter outlet pipeline G2, and several pre-cross-flow filter outlet pipelines G2 are arranged in parallel, and are connected to a circulation pump feed pipeline G3 after being connected in parallel. Through the above arrangement, the filter circulation material outlet 2b can be connected to the circulation pump 3; the pre-cross-flow filter outlet pipeline G2 is connected to a pre-cross-flow filter outlet valve V2.

[0026] The side of the pre-cross-flow filter is provided with a clear liquid outlet 2c, the number of the pre-cross-flow filters 2 corresponds to the number of the side circulating material outlets 1b, the plurality of pre-cross-flow filters 2 are all located outside the reactor 1, and the plurality of pre-cross-flow filters 2 have the same height; the suction end of the circulation pump 3 is connected to the discharge port 1d of the reactor 1 through a pipeline, and the discharge end of the circulation pump 3 is connected to the circulating material reflux port 1c of the reactor 1 through a pipeline; the clear liquid outlet 2c of each pre-cross-flow filter 2 is connected to the clear liquid main pipeline G7 through a branch pipe, and the clear liquid main pipeline G7 is connected to a regulating valve V5 for adjusting the outflow of the clear liquid.

[0027] The pipeline between the discharge end of the circulation pump 3 and the circulation material reflux port 1c of the reactor 1 is connected with a heat exchanger 4 and a pipeline mixer 5 in sequence. The circulation pump 3 is connected with the heat exchanger 4 through the heat exchanger inlet pipeline G4. The heat exchanger 4 is connected with the pipeline mixer 5 through the heat exchanger outlet pipeline G5. The pipeline mixer 5 is connected with the circulation material reflux port 1c at the top of the reactor 1 through the reactor reflux pipeline G6.

[0028] During the filtration process, the filtered concentrated slurry of the pre-cross-flow filter 2 flows back to the reactor 1 through the heat exchanger 4 and the pipeline mixer 5 under the action of the circulation pump 3, and the filtered concentrated slurry of the pre-cross-flow filter 2 undergoes heat exchange in the heat exchanger 4.

[0029] In some embodiments, Figures 1 to 5 As shown, the pre-cross-flow filter 2 is single-stage backwash or multi-stage backwash; when the pre-cross-flow filter 2 is multi-stage backwash, a plurality of backwash inlets 2d are arranged along the axial direction of the pre-cross-flow filter 2; a plurality of backwash inlets 2d on the pre-cross-flow filters 2 are connected to the backwash pipeline G8 through a branch pipe; a backwash inlet valve V4 is provided on the branch pipe connected to the backwash inlet 2d on the pre-cross-flow filter 2.

[0030] Exemplarily, at the beginning of startup, the pre-cross-flow filter 2 is disconnected from the reactor 1 and the circulation pump 3, that is, the pre-cross-flow filter inlet valve V1 and the pre-cross-flow filter outlet valve V2 are closed, the clear liquid outlet valve V3 is closed, and the backwash inlet valve V4 is closed; at this time, the pre-cross-flow filter 2 can be disconnected from the reactor 1 and the circulation pump 3; during maintenance, the above valves can also be closed to repair the pre-cross-flow filter 2.

[0031] Dispersion process of the mixed liquid in the reactor 1: the discharge port 1d at the bottom of the reactor 1 is connected to the liquid suction end of the circulation pump 3 through a pipeline, the reactor 1 and the circulation pump 3 are started, and the mixed liquid in the reactor 1 can be discharged from the discharge port 1d at the bottom of the reactor 1, and flow back to the reactor 1 from the circulating material reflux port 1c at the top of the reactor 1 under the action of the circulation pump 3. Through the circulation flow of the above process, the ammoximation liquid containing the catalyst can be dispersed in the reactor 1.

[0032] Filtration process: when the mixed liquid in the reactor 1 meets the filtration requirements, close the valve of the discharge port 1d at the bottom of the reactor 1, open the clear liquid outlet valve V3 of the pre-cross-flow filter 2, open the pre-cross-flow filter inlet valve V1, and open the pre-cross-flow filter outlet valve V2; at this time, the pre-cross-flow filter 2 is connected with the reactor 1 and the circulation pump 3, and the pre-cross-flow filter 2 can filter the mixed liquid while it flows through the pre-cross-flow filter 2.

[0033] Exemplarily, the interior of the pre-cross-flow filter 2 is divided into a dispersion zone, a filtration zone and a confluence zone from top to bottom; when the vertical height of the filtration zone is less than 1200 mm, it is set as a single-stage backwash; the backwash inlet 2d is set in the filtration zone, and the backwash inlet 2d is perpendicular to the central axis of the pre-cross-flow filter 2; a distributor 2e is provided at the top position inside the pre-cross-flow filter 2, and the distributor 2e can disperse the mixed liquid entering the pre-cross-flow filter 2.

[0034] An upper tube sheet 2f and a lower tube sheet 2g are provided in the pre-cross-flow filter 2, a plurality of tubular filter elements 2h are provided between the upper tube sheet 2f and the lower tube sheet 2g, and a plurality of through holes communicating with the tubular filter elements 2h are provided between the upper tube sheet 2f and the lower tube sheet 2g.

[0035] When the vertical height of the filtration area is 1200~2400mm, it is set to two or three stages of recoil; the recoil inlet 2d is set in the filtration area and is perpendicular to the center axis of the filter, and each section of the recoil inlet 2d is equally divided along the center axis.

[0036] When the vertical height of the filtration zone is greater than 2400 mm, at least three sections of recoil are provided, and the recoil inlet 2d is provided in the filtration zone and is perpendicular to the central axis of the filter, and each section of the recoil inlet 2d is equally divided along the central axis.

[0037] Exemplarily, a recoil baffle 2i aligned with the recoil inlet 2d is provided on the inner peripheral wall of the pre-cross-flow filter 2. During the backwashing process, the recoil medium flows in a preset direction under the action of the recoil baffle 2i.

[0038] In some embodiments, Figure 1 As shown, when the diameter of the pre-cross-flow filter 2 is greater than the preset diameter, a plurality of backwash inlets 2d are arranged along the circumference of the pre-cross-flow filter 2 .

[0039] Exemplarily, when the diameter of the front cross-flow filter 2 does not exceed 450 mm, one backwash inlet 2d is arranged on the same backwash plane; when the diameter of the front cross-flow filter 2 is greater than 450 mm, at least two backwash inlets 2d are arranged on the same plane.

[0040] Exemplarily, when there are multiple recoil inlets 2d on the same horizontal plane, a valve can be set for each recoil inlet 2d, or only one valve can be set; when one valve is set, multiple recoil inlets 2d are connected to the recoil pipeline G8, an inlet pipe is set on the recoil pipeline G8, and a valve is set on the inlet pipe.

[0041] Exemplarily, the tubular filter element 2h is one or more of a metal powder sintered filter element, a ceramic filter element, and a powder mesh composite filter element; preferably, the tubular filter element 2h is a metal powder sintered filter element and / or a powder mesh composite filter element.

[0042] Exemplarily, a single tubular filter element 2h may have one or more flow channels, and preferably, one flow channel.

[0043] In some embodiments, Figures 1 to 5 As shown, when one of the pre-cross-flow filters 2 needs to be backwashed, the clear liquid outlet valve V3 of the pre-cross-flow filter 2 is closed, and the backwash inlet valve V4 of the pre-cross-flow filter 2 is opened.

[0044] During backwashing, the pressure of the backwashing medium is higher than the pressure of the mixed liquid in the tubular filter element 2h, and the backwashing medium enters the tubular filter element 2h from the outside and mixes with the mixed liquid; the filter cake filtration layer on the inner wall of the tubular filter element 2h separates from the tubular filter element 2h under the pressure of the backwashing medium, and finally mixes with the filtered solid-containing material in the central flow channel of the tubular filter element 2h along with the backwashing medium, re-participates in the filtration cycle, and flows out of the pre-cross-flow filter 2 with the mixed liquid.

[0045] After the backflushing is completed, the backflushing inlet valve V4 of the pre-cross-flow filter 2 is closed, and the clear liquid outlet valve V3 of the pre-cross-flow filter 2 is opened.

[0046] Exemplarily, during the filtering process, the ammonia oxime feed liquid containing the catalyst flows through the tubular filter element 2h at a preset flow rate, so that a filter cake filtration layer of a preset thickness is formed on the inner wall of the tubular filter element 2h. The filter cake filtration layer can not only filter, but also protect the tubular filter element 2h, thereby reducing the occurrence of small particles of matter being compacted on the tubular filter element 2h and increasing the service life of the tubular filter element 2h. After the small particles of matter are compacted on the tubular filter element 2h, it is difficult to recoil. Therefore, in the present application, the tubular filter element 2h can be protected by forming a filter cake filtration layer.

[0047] Exemplarily, the pre-cross-flow filter 2 is arranged outside the reactor 1 and before the circulation pump 3. It only needs to rely on the reactor pressure and the static liquid level pressure for filtering, and does not need to provide additional pressure, thereby reducing the energy consumption of the circulation pump 3.

[0048] Embodiment 1: The volume of a single reactor is about 120m³, the single reactor production capacity is equipped with 100,000 tons / year of caprolactam production capacity, and the operating pressure is 2bar; Circulation pump 3: circulation volume 800m³ / hr, head 38m; Four side circulation material outlets 1b1b are evenly distributed on the outer wall of the middle part of the reactor, and are respectively connected to a pre-pre-cross-flow filter 2, a total of four filters, which are placed vertically, and the filtration area height of each filter is about 2350mm, the filter diameter is DN600, and each filter is provided with a clear liquid outlet 2c at the upper part of the filtration area. At the same time, three-stage backwashing is adopted, and three backwashing inlets 2d are arranged on each backwashing plane. The three backwashing inlets 2d share a backwashing inlet valve V4, and a total of three backwashing inlet valves V4 are arranged for each filter; the inner filter element 2h of the filter adopts a metal powder sintered tubular filter element 2h, the filter element 2h has a diameter of 13mm, a wall thickness of 1.5mm, a single channel, and a filtration layer accuracy of the filter element 2h is 0.5μm; the backwashing pressure difference is 2bar, and the backwashing frequency is 6 times / hour.

[0049] Embodiment 2: The volume of a single reactor is about 120m³, the single reactor production capacity is equipped with 100,000 tons / year of caprolactam production capacity, and the operating pressure is 2bar; Circulation pump 3: circulation volume 800m³ / hr, head 38m; Six side circulation material outlets 1b1b are evenly distributed on the outer wall of the middle part of the reactor, and are respectively connected to a pre-pre-cross-flow filter 2, a total of four filters, which are placed vertically, and the filtration area height of each filter is about 1100mm, the filter diameter is DN600, and each filter is provided with a clear liquid outlet 2c at the upper part of the filtration area. At the same time, three-stage backwashing is adopted, and three backwashing inlets 2d are arranged on each backwashing plane. The three backwashing inlets 2d share a backwashing inlet valve V4, and a total of three backwashing inlet valves V4 are arranged for each filter; the filter element 2h in the filter adopts a metal powder sintered tubular filter element 2h, the filter element 2h has a diameter of 13mm, a wall thickness of 1.5mm, a single channel, and a filter layer accuracy of 0.5μm; the backwashing pressure difference is 2bar, and the backwashing frequency is 8 times / hour.

[0050] Embodiment 3: The volume of a single reactor is about 120m³, the single reactor production capacity is equipped with 100,000 tons / year of caprolactam production capacity, and the operating pressure is 2bar; Circulation pump 3: circulation volume 800m³ / hr, head 38m; Four side circulation material outlets 1b1b are evenly distributed on the outer wall of the middle part of the reactor, and are respectively connected to a front cross-flow filter 2, a total of four filters, which are placed vertically, and the filtration area height of each filter is about 2350mm, the filter diameter is DN3, and each filter is provided with a clear liquid outlet 2c at the upper part of the filtration area. At the same time, three-stage backwashing is adopted, and three backwashing inlets 2d are arranged on each backwashing plane. The three backwashing inlets 2d are respectively equipped with a backwashing inlet valve V4, and a total of 9 backwashing inlet valves V4 are arranged for each filter; the filter element 2h in the filter adopts a metal powder sintered tubular filter element 2h, the filter element 2h has a diameter of 13mm, a wall thickness of 1.5mm, a single channel, and a filter layer accuracy of 0.5μm; the backwashing pressure difference is 2bar, and the backwashing frequency is 3 times / hour.

[0051] Embodiment 4: The volume of a single reactor is about 120m³, the single reactor production capacity is equipped with 100,000 tons / year of caprolactam production capacity, and the operating pressure is 2bar; Circulation pump 3: circulation volume 800m³ / hr, head 38m; Four side circulation material outlets 1b1b are evenly distributed on the outer wall of the middle part of the reactor, and are respectively connected to a pre-pre-cross-flow filter 2, a total of four filters, which are placed vertically, and the filtration area height of each filter is about 3600mm, the filter diameter is DN400, and each filter is provided with a clear liquid outlet 2c at the upper part of the filtration area. At the same time, five-stage backwashing is adopted, and a backwashing inlet 2d is provided on each backwashing plane, and a backwashing inlet valve V4 is provided. A total of 5 backwashing inlet valves V4 are provided for each filter; the inner filter element 2h of the filter adopts a metal powder sintered tubular filter element 2h, the filter element 2h has a diameter of 13mm, a wall thickness of 1.5mm, a single channel, and a filter layer accuracy of the filter element 2h is 0.5μm; the backwashing pressure difference is 2bar, and the backwashing frequency is 5 times / hour.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A separation and filtration method for an ammoximation reaction liquid, characterized in that: The following steps are involved: The ammoximation liquid containing the catalyst is dispersed in the reactor; After dispersion, the ammoximation liquid containing the catalyst enters a pre-cross-flow filter; the pre-cross-flow filters are at least two arranged in parallel, and each pre-cross-flow filter is located outside the reactor; The ammoximation liquid containing the catalyst flows through the tubular filter element at a preset flow rate in the pre-cross-flow filter, and during the flow process, a filter cake filtration layer of a preset thickness is formed on the inner peripheral wall of the tubular filter element; The filtered clear liquid is discharged from the side of the pre-cross-flow filter, and the filtered concentrated slurry enters the circulation pump from the filter circulation material outlet at the bottom of the pre-cross-flow filter, and flows back to the reactor under the action of the circulation pump.

2. The separation and filtration method for ammoximation reaction liquid according to claim 1, characterized in that: The pipeline between the discharge end of the circulation pump and the circulating material return port of the reactor is connected with a heat exchanger and a pipeline mixer in sequence. Under the action of the circulation pump, the filtered concentrated slurry flows back to the reactor after passing through the heat exchanger and the pipeline mixer.

3. The separation and filtration method for ammoximation reaction liquid according to claim 1, characterized in that: At the beginning of the startup, the pre-cross-flow filter is disconnected from the reactor and the circulation pump respectively, the clear liquid outlet valve and the backwash inlet valve of the pre-cross-flow filter are closed, and the discharge port at the bottom of the reactor is connected to the liquid suction end of the circulation pump through a pipeline; Start the reactor and the circulation pump so that the mixed liquid in the reactor can circulate; when the mixed liquid in the reactor meets the filtering requirements, close the discharge port at the bottom of the reactor, connect the pre-cross-flow filter with the reactor and the circulation pump, and open the clear liquid outlet valve of the pre-cross-flow filter to filter the mixed liquid.

4. The separation and filtration method for ammoximation reaction liquid according to claim 1, characterized in that: The clear liquid outlet of each pre-cross-flow filter is connected to the clear liquid main pipeline through a branch pipe, and the clear liquid main pipeline is connected with a regulating valve for adjusting the outflow of the clear liquid.

5. The separation and filtration method for ammoximation reaction liquid according to claim 1, characterized in that: When one of the pre-cross-flow filters needs to be backwashed, close the clear liquid outlet valve of the pre-cross-flow filter and open the backwash inlet valve of the pre-cross-flow filter; During backwashing, the pressure of the backwashing medium is higher than the pressure of the mixed liquid in the tubular filter element. The backwashing medium enters the tubular filter element from the outside and mixes with the mixed liquid. The filter cake filter layer on the inner wall of the tubular filter element separates from the tubular filter element and flows out of the front cross-flow filter with the mixed liquid. After the backwash is completed, close the backwash inlet valve of the pre-cross-flow filter and open the clear liquid outlet valve of the pre-cross-flow filter.

6. The separation and filtration method for ammoximation reaction liquid according to claim 5, characterized in that: The front cross-flow filter is single-stage backwash or multi-stage backwash; when the front cross-flow filter is multi-stage backwash, the backwash inlet is set to be several along the axial direction of the front cross-flow filter.

7. A separation and filtration method for ammoximation reaction liquid as claimed in claim 5 or 6, characterized in that: When the diameter of the pre-cross-flow filter is larger than the preset diameter, a plurality of backwash inlets are arranged along the circumference of the pre-cross-flow filter.

8. The separation and filtration method for ammoximation reaction liquid according to claim 5, characterized in that: The inner peripheral wall of the pre-cross-flow filter is provided with a recoil baffle which is aligned with the recoil inlet. During the backwashing process, the recoil medium flows in a preset direction under the action of the recoil baffle.

9. The separation and filtration method for ammoximation reaction liquid according to claim 5, characterized in that: When one of the pre-cross-flow filters needs to be repaired, close the pre-cross-flow filter inlet valve, the pre-cross-flow filter outlet valve, the clear liquid outlet valve and the backwash inlet valve.

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