Nitrogen closed circulation system for PTA (pure terephthalic acid) conveying

Abstract

The invention discloses a nitrogen closed circulation system for PTA conveying, and belongs to the technical field of chemical production, the nitrogen closed circulation system comprises a rotary kiln for drying PTA powder, the PTA powder is conveyed to the rotary kiln in a closed manner through a nitrogen tube pass, the nitrogen tube pass is communicated with an oxidation tail gas tube pass of an oxidation reactor, the PTA powder dried by the rotary kiln enters a PTA cooler, and the PTA cooler is communicated with the rotary kiln. The PTA cooler cools powder and then enters the PTA finished product bin along with the oxidized tail gas, entrained powder is removed from gas in the PTA finished product bin through the bag filter, the oxidized tail gas entering the water washing tower is washed through a water washing tower washing agent, and the washed oxidized tail gas sequentially passes through the gas-liquid separation tank and the tail gas drying system and then is sent to the nitrogen compressor; oxidized tail gas is pressurized and sent to the buffer tank through the nitrogen compressor, tube pass closed circulation conveying is achieved through the pressurized tail gas in the buffer tank, the technical problems that due to the adoption of an external gas source, the powder quality is reduced, and micro powder is mixed in gas and discharged are solved, and the device is mainly applied to powder closed conveying.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and in particular relates to a nitrogen closed circulation system for PTA transportation. Background Art

[0002] The conveying methods of powdered PTA are divided into solid conveying method and pneumatic conveying method. The solid conveying method can be belt conveyor, bucket elevator or screw conveyor. The pneumatic conveying method mainly consists of air source, conveying pipeline, feeding device, separation device and receiving device. The airflow generated by the air source forms a certain air velocity in the conveying pipeline, and the powdered PTA is suspended in the airflow and then transported along the pipeline. In the positive pressure pneumatic conveying system, the fan compresses the air and sends it into the pipeline, so that PTA is carried by the airflow at the entrance of the pipeline and sent to the rotary kiln for drying by pneumatic conveying.

[0003] In the pneumatic conveying method, the conveying gas is discharged into the air after passing through the filter of the PTA finished product silo. At this time, the exhaust air still contains PTA fine powder, and due to the use of an external air source, impurities will be mixed into the powder, resulting in a decrease in quality. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a nitrogen closed circulation system for PTA transportation, which solves the technical problems of using an external gas source leading to a decrease in powder quality and the discharge of micro-powder mixed in the gas.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions: a nitrogen closed circulation system for PTA transportation, comprising a rotary kiln for drying PTA powder, the PTA powder is sealed and transported to the rotary kiln through a nitrogen pipe line, the nitrogen pipe line is connected to the oxidation tail gas pipe line of the oxidation reactor, and the dried powder enters the PTA cooler through the rotary kiln, the PTA cooler reduces the temperature of the powder to 85°C and then enters the PTA finished product silo with the oxidation tail gas, the gas in the PTA finished product silo is sent to a water washing tower after removing the entrained powder through a bag filter, the oxidation tail gas entering the water washing tower is washed by a water washing tower detergent, the washed oxidation tail gas is sent to a nitrogen compressor after passing through a gas-liquid separation tank and a tail gas drying system in turn, the liquid phase of the gas-liquid separation tank is refluxed to the water washing tower for reuse, the oxidation tail gas is pressurized by a nitrogen compressor and sent to a buffer tank, and the pressurized tail gas in the buffer tank is used to realize the closed circulation transportation of the pipe line;

[0006] The washing liquid from the washing tower is recovered to the pulping tank, and the material in the pulping tank is sent to the refined batching pipe for use, reducing PTA loss.

[0007] Furthermore, a group of equidistantly distributed annular grid plates are arranged inside the rotary kiln, and the number of micro-powder cages is less than that of the grid plates, and the micro-powder cages are connected at intervals along the annularly arranged grid plates.

[0008] Furthermore: the inlet of the rotary kiln is connected to the preheater body through a transfer chute, and the upper part of the preheater body is provided with a preheater lower hopper, which is used to connect the materials transported by the oxidation tail gas pipe, and the tail of the rotary kiln is used to connect to the PTA cooler.

[0009] Furthermore: the rotating assembly includes a rotating wheel driven by a motor, the rotating wheel is fixedly connected to the first rotating shaft, after the first rotating shaft passes through the lower hopper of the preheater, there is a diverter plate on the first rotating shaft in the lower hopper of the preheater, and the powder intermittently enters the preheater body through the rotation of the first rotating shaft.

[0010] Furthermore: a screen is provided in the transfer chute, the second rotating shaft is installed on the transfer chute, a single-sided pressure roller is provided on the second rotating shaft, the single-sided pressure roller is used to press the upper surface of the screen, and one end of the second rotating shaft is fixedly connected to the gear.

[0011] Further: the swing arm mechanism for driving the gear to rotate comprises a third rotating shaft, a third rotating shaft, the third rotating shaft is rotatably mounted on the lower hopper of the preheater, a swing arm fixedly connected to the third rotating shaft and a fan-shaped swing plate, the swing arm has a strip groove, and the bottom surface of the fan-shaped swing plate is a meshing tooth, which meshes with the gear through the meshing tooth;

[0012] The rotating wheel extends a swing rod, the swing rod is provided with a protrusion, and the protrusion is inserted into the bar groove.

[0013] Compared with the prior art, the present invention has the following advantages: 1. By utilizing the property that the oxidation tail gas is insoluble in water, the gas carrying PTA dust and impurities is washed by a water washing tower detergent to obtain clean oxidation tail gas, and the washed oxidation tail gas is dried and compressed and used as a gas source to realize closed circulation transportation;

[0014] 2. By adding partition plates and micro powder cages in the rotary kiln, the powder entering the rotary kiln falls unevenly into the grooves between the adjacent partition plates, and slides freely when it is at a high position as the rotary kiln rotates, thereby extending the contact time between the product and the rotary kiln and improving the distribution rate of the product in the rotary kiln. On the other hand, when the rotary kiln rotates, the micro powder between the partition plates falls into the micro powder cage when the opening of a part of the micro powder cage is at a high position, and the powder in the micro powder cage is separated when the opening of a part of the micro powder cage is at a low position, thereby shortening the heating contact time between the micro powder and the kiln body of the rotary kiln;

[0015] 3. By adding a rotating component and a swing arm mechanism, the rotating wheel of the active component drives the swing rod to rotate during rotation, and the swing rod drives the protrusion to slide in the strip groove during rotation. During the sliding process, the swing arm and the fan plate are driven to swing along the rotating connection point of the third rotating axis and the lower hopper of the preheater. The swing of the fan plate causes the gear meshing with its meshing teeth to rotate. During its rotation, the second rotating axis drives the single-sided pressure roller to roll on the surface of the screen to crush the agglomerated materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a working diagram of the nitrogen closed cycle delivery of the present invention;

[0017] Figure 2 It is a schematic diagram of the connection between the rotary kiln and the cooler of the present invention;

[0018] Figure 3 is a cross-sectional view of a rotary kiln of the present invention;

[0019] Figure 4 The present invention Figure 2 Partial cross-sectional view at point A;

[0020] Figure 5 It is a structural diagram of the rotating assembly of the present invention;

[0021] Figure 6 It is a structural diagram of the swing assembly of the present invention;

[0022] Figure 7 It is a schematic diagram of the connection between the active component and the swing component of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] In the description of the invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0025] Embodiment 1:

[0026] In one technical solution of the present invention, Figure 1As shown, a nitrogen closed circulation system for PTA transportation comprises a rotary kiln 1 for drying PTA powder, the PTA powder is sealed and transported to the rotary kiln 1 through a nitrogen pipe line, the nitrogen pipe line is connected with the oxidation tail gas pipe line of the oxidation reactor 14, the PTA powder dried by the rotary kiln 1 enters the PTA cooler 2, the PTA cooler 2 reduces the temperature of the powder to 85°C and then enters the PTA finished product silo 3 with the oxidation tail gas, the gas in the PTA finished product silo 3 is sent to a water washing tower 5 after the entrained PTA powder is removed by a bag filter 4, the oxidation tail gas entering the water washing tower 5 is washed by a water washing tower detergent, the washed oxidation tail gas is sequentially sent to a nitrogen compressor 8 through a gas-liquid separation tank 6 and a tail gas drying system 7, the liquid phase of the gas-liquid separation tank 6 is refluxed to the water washing tower 5 for reuse, the oxidation tail gas is pressurized by the nitrogen compressor 8 and sent to a buffer tank 9, and the pressurized tail gas in the buffer tank 9 is used to realize the closed circulation transportation of the pipe line;

[0027] The washing liquid from the washing tower 5 is recovered to the pulping tank 10, and the materials in the pulping tank 10 are sent to the refined batching tank 11 for use, thereby reducing the loss of PTA.

[0028] In the above technical scheme: the PTA product is a raw material PX300 which undergoes an oxidation reaction with oxygen in the air in an oxidation reactor with brittle acid as a solvent under the action of a cobalt-manganese-bromine catalyst to generate terephthalic acid. The terephthalic acid slurry is subjected to step-by-step pressure reduction flash evaporation and crystallization in an oxidation crystallizer, and then is sent to an oxidation filter for filtration, washing and drying to obtain crude terephthalic acid. The crude terephthalic acid powder and hot water are slurried in a refined batching tank 11, and the slurry obtained by slurrying is heated step by step and then subjected to a hydrogenation reaction in a hydrogenation reactor. The catalyst for the hydrogenation reaction can be solid palladium-carbon particles. The discharge from the hydrogenation reactor is subjected to pressure reduction flash evaporation and crystallization in a refined crystallizer. The discharge from the bottom of the refined crystallizer is sent to a refined pressure filter for solid-liquid separation to obtain a refined terephthalic acid product.

[0029] The nitrogen compressor pressurizes the gas to 4.7 Barg to meet the delivery pressure;

[0030] The pressurized gas in the buffer tank and the low-pressure nitrogen added to the buffer tank make the oxidation tail gas and the obtained phthalic acid product form a gas-solid in the pipeline and be transported into the rotary kiln 1. The rotary kiln 1 adopts a jacket heating type. Its heating medium can be steam or heat transfer oil. The heating medium flows in the jacket and transfers the heat to the internal material through the kiln wall. The rotary kiln 1 is composed of a rotary kiln roller and a transmission device, which makes the rotary kiln 1 rotate. The rotary kiln 1 is inclined at 3.5 degrees to the ground along the center line. The PTA powder dried in the rotary kiln 1 falls into the PTA cooler 2. The PTA cooler The cooler reduces the temperature of PTA powder from 120-140°C to 85°C, and the powder enters the PTA finished product silo 3 along with the oxidized tail gas. The gas in the PTA finished product silo 3 is sent to the water washing tower 5 after the entrained PTA powder is removed by the bag filter 4. The oxidized tail gas entering the water washing tower 5 is washed by the water washing tower detergent. The washed oxidized tail gas passes through the gas-liquid separation tank 6 and the tail gas drying system 7 in turn and is sent to the nitrogen compressor 8. The liquid phase of the gas-liquid separation tank 6 is refluxed to the water washing tower 5 for reuse. The oxidized tail gas is pressurized by the nitrogen compressor 8 and sent to the buffer tank 9. The buffer tank 9 is externally connected to low-pressure nitrogen.

[0031] Embodiment 2:

[0032] In one embodiment of the present invention, Figure 2 and Figure 3 As shown, a group of equally spaced dividing plates 12 are arranged inside the rotary kiln 1, and the number of micro-powder cages 13 is less than the number of the dividing plates 12, and the micro-powder cages 13 are connected at intervals along the dividing plates 12 arranged in an annular manner.

[0033] By adopting the above technical solution: a group of grid plates 12 are evenly distributed in a ring on the inner wall of the rotary kiln 1, and the powder entering the rotary kiln 1 falls unevenly into the grooves between the adjacent grid plates 12, and slides freely when it is at a high position as the rotary kiln 1 rotates, thereby extending the contact time between the product and the rotary kiln and improving the distribution rate of the product in the rotary kiln;

[0034] In this embodiment, the number of the grid plates used is even, such as 6, 8, 10, 12, etc. The number of the micro-powder cages 13 is half of the grid plates 12. For example, if 12 grid plates are used, the number of the micro-powder cages 13 is 6. Each micro-powder cage 13 is fixedly connected to a non-adjacent grid plate 12. The micro-powder cage 13 is composed of a plate mesh with micropores, one end of which is open and the other end is closed.

[0035] The powder entering the rotary kiln 1 falls unevenly into the grooves between adjacent partition plates 12. When the rotary kiln 1 rotates so that the openings of some micro-powder cages 13 are at a high position, the micro-powder between the partition plates 12 falls into the micro-powder cages 13. At the same time, when the openings of some micro-powder cages 13 are at a low position, the powder in the micro-powder cages 13 is separated. In this way, the heating time of the micro-powder is shortened, and the micro-powder is prevented from being heated for a long time so that the carboxyl part is oxidized to a carbonyl group (-C=O), resulting in a decrease in purity.

[0036] Embodiment 3:

[0037] In one embodiment of the present invention, Figure 2-Figure 7 As shown, a nitrogen closed circulation system for PTA transportation, the inlet of the rotary kiln 1 is connected to the preheater body 16 through a transfer chute 15, the upper part of the preheater body 16 is provided with a preheater lower hopper 17, the preheater lower hopper 17 is used to connect the material transported by the oxidation tail gas pipe, and the tail of the rotary kiln 1 is used to connect the PTA cooler 2;

[0038] The rotating assembly includes a rotating wheel 19 driven by a motor 18, and the rotating wheel 19 is fixedly connected to a first rotating shaft 20. After the first rotating shaft 20 passes through the preheater lower hopper 17, a diverter plate 21 is provided on the first rotating shaft 20 in the preheater lower hopper 17, and the powder intermittently enters the preheater body 16 through the rotation of the first rotating shaft 20;

[0039] The transfer chute 15 is provided with a screen 27, a second rotating shaft 28 is installed on the transfer chute 15, a single-sided pressing roller 29 is provided on the second rotating shaft 28, and the single-sided pressing roller 29 is used to press the upper surface of the screen 27, and one end of the second rotating shaft 29 is fixedly connected to the gear 30;

[0040] The swing arm mechanism for driving the gear 30 to rotate includes a third rotating shaft 31, the third rotating shaft 31 is rotatably mounted on the preheater body 16, a swing arm 32 fixedly connected to the third rotating shaft 31 and a fan-shaped swing plate 33, the swing arm 32 has a strip groove 34, and the bottom surface of the fan-shaped swing plate 33 is a meshing tooth 35, which meshes with the gear 30 through the meshing tooth 35;

[0041] The rotating wheel 19 extends a swing rod 36 , and a protrusion 37 is formed on the swing rod 36 . The protrusion 37 is inserted into the strip groove 34 .

[0042] By adopting the above technical solution: the starter motor 18 drives the runner 19, the first rotating shaft 20 and the diverter plate 21 to rotate, and the pressurized gas in the buffer tank 9 and the low-pressure nitrogen added to the buffer tank 9 make the oxidation tail gas and the obtained purified terephthalic acid product form a gas-solid in the pipeline and be transported into the preheater lower hopper 17. A part of the PTA powder entering the preheater lower hopper 17 directly enters the preheater body 16, and a part is blocked by the diverter plate 21, which slows down the speed of entering the preheater body 16. The PTA powder on the diverter plate 21 falls into the preheater body 16 as the diverter plate 21 rotates, which reduces the descending speed of the product and prolongs the preheating time.

[0043] At the same time, the swing rod 36 is driven to rotate during the rotation of the rotating wheel 19, and the protrusion 37 is driven to slide in the strip groove 34 during the rotation of the swing rod 36. During the sliding process, the swing arm 32 and the fan plate 33 are driven to swing along the rotation connection point between the third rotating shaft 31 and the preheater lower hopper 17. The swing of the fan plate 33 causes the gear 30 meshing with its meshing teeth 35 to rotate. During its rotation, the second rotating shaft 29 drives the single-sided pressure roller 29 to roll on the surface of the screen 27 to crush the agglomerated materials.

[0044] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention. These improvements should also be regarded as within the scope of protection of the present invention.

Claims

1. A nitrogen closed circulation system for conveying PTA, comprising a rotary kiln (1) for drying PTA powder, wherein the PTA powder is conveyed to the rotary kiln (1) in a closed manner through a nitrogen pipe line, wherein the nitrogen pipe line is connected to an oxidation tail gas pipe line of an oxidation reactor (14), wherein the PTA powder dried in the rotary kiln (1) enters a PTA cooler (2), wherein the PTA cooler (2) lowers the temperature of the powder to 85° C. and then enters a PTA finished product silo (3) along with the oxidation tail gas, wherein: The gas in the PTA finished product silo (3) is sent to a water scrubber (5) after the entrained PTA powder is removed by a bag filter (4). The oxidized tail gas entering the water scrubber (5) is washed by a water scrubber detergent. The washed oxidized tail gas passes through a gas-liquid separation tank (6) and a tail gas drying system (7) in sequence and is sent to a nitrogen compressor (8). The liquid phase of the gas-liquid separation tank (6) is refluxed to the water scrubber (5) for reuse. The oxidized tail gas is pressurized by the nitrogen compressor (8) and sent to a buffer tank (9). The pressurized tail gas in the buffer tank (9) is used to realize a closed circulation transportation in the pipeline. The washing liquid from the water washing tower (5) is recovered to the pulping tank (10), and the material in the pulping tank (10) is sent to the refined batching tank (11) for use, thereby reducing PTA loss.

2. A nitrogen closed circulation system for PTA transportation according to claim 1, characterized in that: The rotary kiln (1) is provided with a group of equidistantly distributed dividing plates (12) in an annular shape, and a number of micro-powder cages (13) which is less than the number of the dividing plates (12). The micro-powder cages (13) are connected at intervals along the annularly arranged dividing plates (12).

3. A nitrogen closed circulation system for PTA transportation according to claim 1, characterized in that: The inlet of the rotary kiln (1) is connected to the preheater body (16) through a transfer chute (15). The upper part of the preheater body (16) is provided with a preheater lower hopper (17). The preheater lower hopper (17) is used to connect the materials transported by the oxidation tail gas pipeline. The tail of the rotary kiln (1) is used to connect to the PTA cooler (2).

4. A nitrogen closed circulation system for PTA transportation according to claim 3, characterized in that: The rotating assembly comprises a rotating wheel (19) driven by a motor (18), the rotating wheel (19) being fixedly connected to a first rotating shaft (20), and after the first rotating shaft (20) passes through a preheater lower hopper (17), a diverter plate (21) is provided on the first rotating shaft (20) in the preheater lower hopper (17), so that the powder intermittently enters the preheater body (16) through the rotation of the first rotating shaft (20).

5. A nitrogen closed circulation system for PTA transportation according to claim 3, characterized in that: A screen (27) is provided in the transfer chute (15), and a second rotating shaft (28) is installed on the transfer chute (15). A single-sided pressing roller (29) is provided on the second rotating shaft (28), and the single-sided pressing roller (29) is used to press the upper surface of the screen (27). One end of the second rotating shaft (29) is fixedly connected to a gear (30).

6. A nitrogen closed circulation system for PTA transportation according to claim 5, characterized in that: The swing arm mechanism for driving the gear (30) to rotate comprises a third rotating shaft (31), the third rotating shaft (31) is rotatably mounted on the lower hopper (17) of the preheater, a swing arm (32) fixedly connected to the third rotating shaft (31) and a fan-shaped swing plate (33), the swing arm (32) having a strip groove (34), and the bottom surface of the fan-shaped swing plate (33) is meshing teeth (35), which mesh with the gear (30) through the meshing teeth (35); The rotating wheel (19) extends a swing rod (36), the swing rod (36) is provided with a protrusion (34), and the protrusion (34) is inserted into the strip groove (34).

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