Oxamide powder drying device

Abstract

The utility model discloses an oxamide powder drying device. The oxamide powder drying device comprises a filter, a drying device and a drying device, wherein the filter is used for solid-liquid separation of oxamide-containing slurry; the pneumatic dryer is used for drying the solid phase filtered by the filter; the vacuum disc dryer is used for secondary drying of the materials dried by the pneumatic dryer; and the waste gas treatment assembly is connected with the pneumatic dryer and the vacuum disc dryer and is used for treating waste gas. According to the drying device, no waste gas, waste liquid or waste solid is discharged in the drying process and the circulating gas treatment process, the requirement for the filtering precision of the dryer / filter in the drying process is low, the filter can not be blocked, and then large-scale continuous environment-friendly production of the drying process for preparing oxamide through dimethyl oxalate ammonolysis is achieved.

Description

Technical Field

[0001] This utility model relates to the field of chemical production technology, and in particular to a drying device for oxalamide powder. Background Technology

[0002] Oxalide powder is non-toxic, has low solubility in water, and is easy to store. It is used in agriculture and chemical industries. Its proper use can effectively promote plant growth and improve the yield and quality of crops.

[0003] In the liquid-phase reaction of ammonolysis of dimethyl oxalate to prepare oxalamide, powder drying is an important step in industrial production. Currently, there are no continuous industrial plants operating for large-scale continuous drying of oxalamide powder, and there are no detailed reports in the literature on the environmentally friendly treatment and recycling of the solvent that removes oxalamide powder.

[0004] In addition, the oxalamide powder produced by the liquid phase method has a small particle size, about 5-30μm. Common powder drying equipment has high requirements for filter filtration accuracy, which can lead to easy clogging of the filter and thus affect the continuous operation of the entire plant. Utility Model Content

[0005] Based on the technical problems existing in the background technology, this utility model proposes an oxamide powder drying device. The drying process and the circulating gas treatment process have no waste gas, waste liquid, or solid waste emissions. Moreover, the drying process has low requirements for the filtration accuracy of the dryer / machine filter, which can achieve the goal of preventing filter clogging. This enables large-scale continuous and environmentally friendly production of oxamide by ammonolysis of dimethyl oxalate.

[0006] The oxamide powder drying device proposed in this utility model includes:

[0007] Filters are used for solid-liquid separation of oxalamide-containing slurries;

[0008] An airflow dryer is used to dry the solid phase filtered by a filter.

[0009] Vacuum disc dryer is used for secondary drying of materials after airflow dryer drying;

[0010] An exhaust gas treatment assembly, connected to the airflow dryer and the vacuum disc dryer, is used for exhaust gas treatment.

[0011] Preferably, a mixing buffer tank is also provided between the filter and the airflow dryer, and the discharge pipe of the airflow dryer is connected to the mixing buffer tank and the vacuum disc dryer respectively.

[0012] Preferably, the airflow dryer is further connected to a nitrogen compressor, and a nitrogen heater is provided between the nitrogen compressor and the airflow dryer.

[0013] Preferably, the exhaust gas treatment assembly includes a quench scrubber, the air inlet of which is connected to the airflow dryer and the vacuum disc dryer, and the liquid inlet of which is connected to a DMO methanol mixer.

[0014] Preferably, the gas outlet of the quench scrubbing tower is further connected to a gas condenser separator, and the liquid outlet of the gas condenser separator is connected to the quench scrubbing tower.

[0015] Preferably, the outlet of the gas condenser is connected to the nitrogen compressor.

[0016] Preferably, an induced draft fan is provided between the vacuum disc dryer and the waste gas treatment component.

[0017] The beneficial technical effects of this utility model are as follows:

[0018] This invention improves the drying capacity of oxalamide by using a closed-loop airflow dryer and a vacuum disc dryer connected in series. Ammonia in the gas from the airflow dryer is absorbed by a quench scrubbing tower, and the nitrogen exiting the quench scrubbing tower is dried by a gas condenser separator. The circulating nitrogen is pressurized by a nitrogen compressor to achieve nitrogen recycling. This invention produces no waste gas, waste liquid, or solid waste emissions during the drying and circulating gas treatment processes. Furthermore, the drying process requires low filtration precision from the dryer filter, preventing filter clogging. This enables large-scale, continuous, and environmentally friendly production of oxalamide from dimethyl oxalate through ammonolysis. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the oxalamide powder drying device proposed in this utility model.

[0020] In the diagram: 1-Filter, 2-Mixing buffer tank, 3-Airflow dryer, 4-Vacuum disc dryer, 5-Exhaust fan, 6-Nitrogen heater, 7-Nitrogen compressor, 8-DMO methanol mixer, 9-Quick cooling scrubber, 10-Gas condenser separator. Detailed Implementation

[0021] The present invention will be further explained below with reference to specific embodiments.

[0022] The oxamide powder drying device proposed in this utility model includes: a filter 1 for solid-liquid separation of oxamide-containing slurry; the liquid phase is discharged from the filter and undergoes alcohol and ammonia treatment processes, while the solid phase enters an airflow dryer 3; the filter 1 is a closed filter, preferably a horizontal spiral centrifuge or a vacuum scraper filter; the airflow dryer 3 is used to dry the solid phase of the filter 1; the airflow dryer can be closed, and the operating pressure can be -0.1 MPaG to 0.5 MPaG, with lower operating pressure being beneficial for powder drying; a vacuum disc dryer 4 is used for secondary drying of the material after drying in the airflow dryer 3; the powder after secondary drying enters the packaging process; and an exhaust gas treatment component connected to the airflow dryer 3 and the vacuum disc dryer 4 for exhaust gas treatment; an induced draft fan 5 is installed between the vacuum disc dryer 4 and the exhaust gas treatment component. The gas outlet filter of the vacuum disc dryer and the gas outlet filter of the airflow dryer have an accuracy requirement of 5-100 μm, preferably 40-60 μm.

[0023] In addition, a mixing buffer tank 2 is provided between the filter 1 and the airflow dryer 3. The discharge pipe of the airflow dryer 3 is connected to the mixing buffer tank 2 and the vacuum disc dryer 4 respectively. After drying by the airflow dryer, part of the material enters the vacuum disc dryer for further drying, and the other part of the material is returned to the mixing buffer tank to mix with the filtered solid material and the oxalamide slurry exiting the filter, thereby improving the fluidity of the oxalamide slurry exiting the filter. The proportion of powder returned from the airflow dryer to the mixing buffer tank is adjustable.

[0024] The airflow dryer 3 is also connected to a nitrogen compressor 7, and a nitrogen heater 6 is provided between the nitrogen compressor 7 and the airflow dryer 3; the gas from the nitrogen compressor is not cooled before entering the nitrogen heater, so as to effectively utilize the heat energy of the compressed gas; the nitrogen gas temperature of the nitrogen heater is 70 to 300°C, preferably 110 to 150°C.

[0025] The exhaust gas treatment assembly includes a quench scrubber 9, whose inlet is connected to an airflow dryer 3 and a vacuum disc dryer 4, and whose liquid inlet is connected to a DMO-methanol mixer 8. The DMO-methanol solution entering the quench scrubber has a molar ratio of DMO to methanol of 3:7 to 9:1, preferably 4:6 to 6:4. The DMO-methanol solution entering the quench scrubber operates at a temperature of 40 to 63°C, preferably 45 to 55°C. The oxamide powder contained in the gas from the quench scrubber is washed and returned to the oxamide reactor, so that the continuous production of the entire plant will not be affected by insufficient filtration accuracy.

[0026] The gas outlet of the quench scrubbing tower 9 is also connected to a gas condenser separator 10, and the liquid outlet of the gas condenser separator 10 is connected to the quench scrubbing tower 9. The operating temperature of the gas condenser separator is -18 to 60°C, preferably -15 to 35°C. Low temperature is beneficial to reduce the methanol content in the circulating nitrogen.

[0027] To enable the recycling of nitrogen, the outlet of the gas condenser separator 10 is connected to the nitrogen compressor 7.

[0028] Application examples

[0029] After the entire drying system is purged with nitrogen, the slurry containing oxamide, methanol, and a small amount of ammonia from the oxamide reactor, with a solid content of approximately 20% and a mass flow rate of 5000 kg / h, is pumped into a plate-type scraper filter centrifuge for liquid-solid separation. The separated liquid is then sent to an ammonia-methanol separation unit; the separated solid phase, containing 70% oxamide and 30% methanol and ammonia, enters mixing buffer tank A. Approximately 1000 kg / h of 95% oxamide powder discharged from the airflow dryer is mixed with the separated solid phase. After mixing, the solid content is approximately 80%, and the powder flowability meets the requirements of the airflow dryer. This mixture is then fed into the airflow dryer by a screw conveyor and mixed with nitrogen at a nitrogen flow rate of approximately 25000 m³ / h. 3 The drying process is carried out at a rate of approximately 1000 kg / h and a temperature of 150℃. After drying, the powder has a moisture content of approximately 5%. A portion of this powder, at a rate of approximately 1000 kg / h, is fed via a screw conveyor to a heat exchange area of ​​approximately 50 m². 2 The vacuum disc dryer produces powder containing approximately 5 ppm of methanol and ammonia, which is then sent to the powder packaging plant; another portion, approximately 1000 kg / h, is sent to the mixing buffer tank B to mix with the solid phase separated by the filter.

[0030] The gas exiting the vacuum disc dryer and airflow dryer is filtered and discharged into the bottom of the quench scrubber, moving upwards along the tower. It comes into countercurrent contact with the DMO methanol solution from the DMO methanol mixer. Ammonia in the gas reacts with DMO to produce ammonium methyl oxalate and oxalamide, which enter the tower bottom with the methanol liquid. The liquid entering the tower bottom is pumped into the reactor to participate in the reaction. The quench scrubber operates at approximately 1 barA, the sprayed DMO methanol solution is at 50°C, and the molar ratio of DMO to methanol is 1:1. The gas exiting from the top of the quench scrubber enters the gas condenser separator. The refrigeration fluid in the gas condenser separator is 5°C chilled water. After the methanol in the gas is separated, it flows by gravity back to the top of the quench scrubber separator to wash and cool the gas exiting the quench scrubber. The nitrogen exiting the gas condenser separator is compressed by a compressor and heated to 150°C using 0.5 MPaG low-pressure steam before entering the airflow dryer to complete the nitrogen recycling process.

Claims

1. A drying device for oxalamide powder, characterized in that, include: The filter (1) is used for solid-liquid separation of oxalamide-containing slurry; Airflow dryer (3) is used to dry the solid phase filtered by filter (1); Vacuum disc dryer (4) is used for secondary drying of materials after airflow dryer (3); The exhaust gas treatment assembly is connected to the airflow dryer (3) and the vacuum disc dryer (4) for the treatment of exhaust gas.

2. The oxalamide powder drying apparatus according to claim 1, characterized in that, A mixing buffer tank (2) is provided between the filter (1) and the airflow dryer (3), and the discharge pipe of the airflow dryer (3) is connected to the mixing buffer tank (2) and the vacuum disc dryer (4) respectively.

3. The oxalamide powder drying apparatus according to claim 1, characterized in that, The airflow dryer (3) is connected to a nitrogen compressor (7), and a nitrogen heater (6) is provided between the nitrogen compressor (7) and the airflow dryer (3).

4. The oxalamide powder drying apparatus according to claim 3, characterized in that, The exhaust gas treatment assembly includes a quench scrubber (9), the air inlet of which is connected to the airflow dryer (3) and the vacuum disc dryer (4), and the liquid inlet of which is connected to a DMO methanol mixer (8).

5. The oxalamide powder drying apparatus according to claim 4, characterized in that, The gas outlet of the quenching scrubbing tower (9) is connected to a gas condenser separator (10), and the liquid outlet of the gas condenser separator (10) is connected to the quenching scrubbing tower (9).

6. The oxalamide powder drying apparatus according to claim 5, characterized in that, The outlet of the gas condenser (10) is connected to the nitrogen compressor (7).

7. The oxalamide powder drying apparatus according to claim 1, characterized in that, An induced draft fan (5) is provided between the vacuum disc dryer (4) and the waste gas treatment component.

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