Continuous urea extraction and purification device

Abstract

The utility model discloses a continuous urea extraction and purification device which comprises a material conveying system, an extraction system, a drying system, a recovery system and a waste liquid recovery system, the material conveying system is used for conveying materials to be extracted to the extraction system, and then the materials treated by the extraction system are conveyed to the drying system to be dried; finally, the materials treated by the drying system are conveyed to a recovery system, and the extraction system and the drying system are respectively connected with a waste liquid recovery system. In order to solve the technical problems that intermittent operation is adopted and the handling capacity is small in the existing urea extraction and purification process, the urea is continuously extracted and dried through the material conveying system, so that the purification effect of the urea can be improved, a large batch of urea can be simultaneously purified, and the energy consumption is reduced.

Description

Technical Field

[0001] The utility model relates to a purification device, in particular to a continuous urea extraction and purification device. Background Art

[0002] The automotive urea standard solution (AUS32) is suitable for trucks, buses, non-road heavy-duty vehicles and other vehicles with diesel engines that have SCR (selective catalytic reduction) systems. The National VI B standard will be officially implemented in July 2023, which has stricter requirements for automobile exhaust emissions. For the automotive urea standard solution, stricter emission requirements mean higher quality requirements.

[0003] The automotive urea solution is made of high-purity water and high-purity urea, and has strict index requirements. GB 29518-2013 specifies technical indicators including biuret, phosphate, insoluble matter and various metal ions. Among them, excessive biuret content in automotive urea will cause scaling and blockage inside the diesel engine post-treatment SCR system and urea nozzles, and in severe cases, the post-treatment SCR system will fail or even cause engine damage.

[0004] At present, urea is mostly purified by recrystallization or extraction to reduce the biuret content in urea. Among them, the recrystallization method has a long process cycle, and the urea yield is low due to the high solubility of urea in water, and more wastewater is generated, which is not conducive to production cost control; the extraction method has a simple process, but the purification effect is lower than that of the recrystallization method. At present, the extraction method uses intermittent operation to extract and purify urea particles by stirring, and the amount of urea particles processed in a single batch is small. Utility Model Content

[0005] Purpose of the utility model: The utility model aims to provide a continuous urea extraction and purification device with good purification effect and large-scale processing.

[0006] Technical solution: The continuous urea extraction and purification device described in the utility model includes a material conveying system, an extraction system, a drying system and a recovery system. The material conveying system is used to convey the material to be extracted to the extraction system, and then convey the material processed by the extraction system to the drying system for drying, and finally convey the material processed by the drying system to the recovery system.

[0007] Furthermore, the material conveying system includes a material feeding area and a material conveying belt connected to the material feeding area.

[0008] Furthermore, the material conveyor belt is a mesh structure, the aperture of the mesh structure is smaller than the aperture of the material to be extracted, so that the material to be extracted on the material conveyor belt can be easily refluxed in the extraction solution in the extraction system.

[0009] Furthermore, the extraction system comprises an extraction kettle, the top of which is provided with a feed port, the bottom of which is provided with an extraction discharge port, and the outside of the extraction kettle comprises a reflux device for refluxing the extract in the extraction kettle.

[0010] Furthermore, the extraction kettle also includes a pulse stirring device, a temperature monitoring device and a heat-insulating jacket arranged on the outer shell of the extraction kettle.

[0011] Furthermore, the reflux device includes a reflux pipe and a reflux pump arranged on the reflux pipe, one end of the reflux pipe is connected to the top of the extraction kettle, and the other end is connected to the bottom of the extraction kettle; a heating copper pipe is arranged inside the reflux pipe.

[0012] Furthermore, the middle of the extraction kettle is provided with an opening for the material conveying system to pass through, and a fence is provided outside the opening. The amount of the extracting liquid fed does not exceed the kettle opening, and the extraction process is to quickly reflux the extracting liquid through the action of a reflux pump. During the reflux process of the extracting liquid, the urea to be extracted on the material conveyor belt will be rinsed and extracted to achieve the purpose of extraction and purification.

[0013] Furthermore, the drying system includes a drying device, a drying hot fan is provided on the top of the drying device, and a drying discharge port for collecting the dried extract is provided at the bottom of the drying device; the wind direction of the drying hot fan is perpendicular to the conveying direction of the material conveying system, and the purpose of the vertical installation of the hot fan is that if the extract is a non-volatile solvent, the hot fan is used to blow the extract to the lower part of the dryer, thereby achieving a faster and better drying effect.

[0014] Furthermore, an opening for allowing a material conveying system to pass through is provided in the middle of the drying device.

[0015] Furthermore, the recovery system includes a receiving funnel.

[0016] Furthermore, the continuous urea extraction and purification device also includes a waste liquid recovery system, and the extraction system and the drying system are respectively connected to the waste liquid recovery system.

[0017] Principle of the invention: The utility model places the urea to be purified in the feeding area and conveys the material through the material conveyor belt. The material passes through the extraction kettle, and the extract in the extraction kettle is a urea-water saturated solution, a urea-20% ethanol water saturated solution or other pure organic solvents with similar effects such as methanol, ethanol, etc. Because the solubility of urea and biuret impurities in the material to be extracted is different in the extractant, the biuret impurities in the urea particles are dissolved in the extract by the rapid reflux of the extract to achieve the purification effect. After purification, the urea particles are conveyed to the dryer through the material conveyor belt, dried by the top hot fan, and the extracted liquid under the purge is collected to complete the purification and drying of the urea particles. After processing a certain amount of urea particles, the biuret impurities in the extract are close to saturation, and the extraction and purification effect is reduced. At this time, the waste liquid recovery process is entered. Pulse stirring is turned on, the temperature in the extraction kettle is cooled and crystallized, and part of the urea in the waste liquid is recovered, and the crystallization mother liquor is used as waste water.

[0018] Beneficial effects: Compared with the prior art, the utility model has the following advantages: the utility model continuously extracts and dries urea through a material conveying system, which can not only improve the purification effect of urea, but also purify large quantities of urea at the same time, reduce energy consumption, shorten the process cycle, and reduce the complexity of manual operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a continuous urea extraction and purification device. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0021] Example 1: Figure 1 As shown, the continuous urea extraction and purification device provided by the utility model includes a material conveying system, an extraction system, a drying system and a recovery system, and a waste liquid recovery system. The material conveying system is used to convey the material to be extracted to the extraction system, and then convey the material processed by the extraction system to the drying system for drying, and finally convey the material processed by the drying system to the recovery system. The extraction system and the drying system are respectively connected to the waste liquid recovery system.

[0022] The material conveying system comprises a feeding area 1 and a material conveying belt 6 connected to the feeding area, and the material conveying belt 6 is a mesh structure.

[0023] The above-mentioned extraction system includes an extraction kettle 2, a feed port 13 is provided at the top of the extraction kettle 2, an extraction discharge port 10 is provided at the bottom of the extraction kettle 2, and the outside of the extraction kettle 2 includes a reflux device for refluxing the extract in the extraction kettle 2, the reflux device includes a reflux pipe 3 and a reflux pump 4 arranged on the reflux pipe 3, one end of the reflux pipe 3 is connected to the top of the extraction kettle 2, and the other end is connected to the bottom of the extraction kettle 2; a heating copper tube is arranged inside the reflux pipe 3; an opening for allowing a material conveying system to pass through is provided in the middle of the extraction kettle 2, and a baffle 9 is provided outside the opening; the extraction kettle 2 also includes a pulse stirring device 11, a temperature monitoring device and an insulation jacket arranged on the outer shell of the extraction kettle 2.

[0024] The drying system comprises a drying device 5, a drying hot fan 8 is arranged on the top of the drying device 5, and a drying discharge port 12 for collecting the dried extract is arranged on the bottom of the drying device 5; the wind direction of the drying hot fan 8 is perpendicular to the conveying direction of the material conveying system, and an opening for allowing the material conveying system to pass is arranged in the middle of the drying device 5.

[0025] The above-mentioned recovery system comprises a receiving hopper 7 .

[0026] The specific method of using the above device is as follows:

[0027] S1: A saturated urea-ethanol solution (40°C) is transferred as an extraction solution to the extraction kettle 2 through the extraction kettle feed port 13, the extraction solution is kept warm at 40°C by the extraction kettle heat exchange jacket, the reflux pump 4 is turned on to allow the extraction solution to reflux continuously, and the reflux pipe 3 is provided with a heating copper pipe to prevent the extraction solution from crystallizing and clogging.

[0028] S2: The urea granules to be purified are put into the feeding area 1, and the urea granules are transported to the extraction kettle 2 through the material conveyor belt 6, and the urea granules are extracted and purified by the refluxed extraction solution; the extraction solution is prevented from splashing out by the outer enclosure 9 of the extraction kettle.

[0029] S3: The extracted urea particles are transported to the drying device 5 through the material conveyor belt 6, and the hot fan 8 is turned on to vertically blow and dry the urea particles on the conveyor belt; the extraction solution generated by the blowing is transported to the waste liquid treatment system through the drying discharge port 12.

[0030] S4: The dried urea granules are purified urea granules, which are transported to the material receiving hopper 7 through the material conveyor belt 6 for material collection.

[0031] S5: Regularly sample the extraction solution from the extraction kettle 2 and test the biuret content of the urea solution according to the method described in Appendix C of GB29518-2013. When the biuret content is too high, the extraction solution is scrapped. Pause the conveying of the material conveyor belt 6, turn off the reflux pump 4, turn on the pulse stirring device 11, and let cold water enter the heat exchange jacket to cool and crystallize the extraction solution; after the cooling is completed, turn off the pulse stirring device 11, and convey the scrapped extraction solution to the waste liquid treatment system through the extraction discharge port 10 of the extraction kettle 2. At the same time, turn on the temperature monitoring device to control the temperature of recrystallization when the waste liquid is recovered; finally, feed the new extraction solution through the extraction kettle feed port 13, turn on the reflux pump 4, and resume the conveying of the material conveyor belt 6.

Claims

1. A continuous urea extraction and purification device, characterized in that: It includes a material conveying system, an extraction system, a drying system and a recovery system. The material conveying system is used to convey the material to be extracted to the extraction system, then convey the material processed by the extraction system to the drying system for drying, and finally convey the material processed by the drying system to the recovery system.

2. The continuous urea extraction and purification device according to claim 1, characterized in that: The material conveying system comprises a material feeding area (1) and a material conveying belt (6) connected to the material feeding area (1).

3. The continuous urea extraction and purification device according to claim 2, characterized in that: The material conveyor belt (6) is a mesh structure.

4. The continuous urea extraction and purification device according to claim 1, characterized in that: The extraction system comprises an extraction kettle (2), the top of the extraction kettle (2) is provided with a feed port (13), the bottom of the extraction kettle (2) is provided with an extraction discharge port (10), and the outside of the extraction kettle (2) comprises a reflux device for refluxing the extract in the extraction kettle (2).

5. The continuous urea extraction and purification device according to claim 4, characterized in that: The extraction kettle (2) further comprises a pulse stirring device (11), a temperature monitoring device and a heat-insulating jacket arranged on the outer shell of the extraction kettle (2).

6. The continuous urea extraction and purification device according to claim 4, characterized in that: The reflux device comprises a reflux pipe (3) and a reflux pump (4) arranged on the reflux pipe (3); one end of the reflux pipe (3) is connected to the top of the extraction kettle (2), and the other end is connected to the bottom of the extraction kettle (2); a heating copper pipe is arranged inside the reflux pipe (3).

7. The continuous urea extraction and purification device according to claim 4, characterized in that: An opening for allowing a material conveying system to pass through is provided in the middle of the extraction kettle (2), and a baffle (9) is provided outside the opening.

8. The continuous urea extraction and purification device according to claim 1, characterized in that: The drying system comprises a drying device (5), a drying hot fan (8) is provided on the top of the drying device (5), and a drying discharge port (12) for collecting the dried extract is provided on the bottom of the drying device (5); the wind direction of the drying hot fan (8) is perpendicular to the conveying direction of the material conveying system.

9. The continuous urea extraction and purification device according to claim 1, characterized in that: The recovery system comprises a receiving hopper (7).

10. The continuous urea extraction and purification device according to any one of claims 1 to 9, characterized in that: It also includes a waste liquid recovery system, and the extraction system and the drying system are respectively connected to the waste liquid recovery system.

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