Low-energy-consumption solvent evaporation recovery system

Abstract

The utility model belongs to the technical field of evaporation, and relates to a low-energy-consumption solvent evaporation recovery system which comprises a preheater, an evaporation tower, a heater, an MVR steam compressor, an MVR heater, a reflux tank, a circulating pump and a reflux pump, a liquid outlet pipe is arranged at the bottom of the evaporation tower, a liquid outlet is connected with the lower part of the evaporation tower, an evaporation pipe connected to a heating inlet is arranged at the top of the evaporation tower, the MVR vapor compressor is arranged on the evaporation pipe, a circulating pump conveys liquid at the lower part of the evaporation tower to a cooling inlet, and a cooling outlet is connected to the bottom of the evaporation tower through a liquid return pipe; the heating outlet is connected with the reflux tank, the outlet of the reflux tank is connected to the steam inlet through a pipeline, and the reflux pump is arranged on the pipeline. According to the system, steam reaching a boiling point is pressurized and heated by the MVR steam compressor to serve as an auxiliary heat source of the evaporation tower, and heat of wastewater serves as a heat source of the preheater, so that the heat is fully utilized, and the energy consumption is effectively saved.

Description

Technical Field

[0001] The utility model relates to the technical field of evaporation, and particularly relates to a low-energy-consumption solvent evaporation and recovery system. Background Art

[0002] Aramid 1313 is a high-performance organic fiber, which is widely used in the fields of aerospace, automobiles, electronics, etc. When producing aramid 1313, dimethylacetamide is used as an organic solvent, and m-phenylenediamine and isophthaloyl chloride are used as polymerization monomers for reaction. Dimethylacetamide does not participate in the reaction during the production process and can be recycled to reduce environmental pollution and production costs.

[0003] The wet spinning method adopted in the production of aramid 1313 results in a low concentration of the discharged dimethylacetamide aqueous solution. The traditional multi-effect rectification recovery method has problems such as high energy consumption, low recovery rate, and large environmental pollution.

[0004] Chinese Patent CN110648775A discloses an operation method for a nuclear power plant radioactive waste liquid MVR evaporation system. The evaporation system disclosed therein uses an electric heating device to heat the solution coming out of the distillation tank, so that the solution exchanges heat in the heater. Here, the temperature increase of the evaporation tower is not direct, and the temperature control in the heater is relatively complex, which is likely to cause heat waste.

[0005] Therefore, it is necessary to design a solution recovery system to solve the above problems. Summary of the Invention

[0006] The main purpose of the utility model is to provide a low-energy-consumption solvent evaporation and recovery system, which can make full use of heat and save energy consumption on the basis of purifying the organic solvent dimethylacetamide.

[0007] The utility model realizes the above purpose through the following technical solutions: A low-energy-consumption solvent evaporation and recovery system includes a preheater, an evaporation tower, a heater, an MVR steam compressor, an MVR heater, a reflux tank, a circulation pump, and a reflux pump;

[0008] The preheater includes a liquid inlet, a liquid outlet, a preheated liquid inlet, and a preheated liquid outlet. The liquid inlet and the liquid outlet are connected through a first flow channel in the preheater, and the preheated liquid inlet and the preheated liquid outlet are connected through a second flow channel in the preheater. The first flow channel and the second flow channel are separated by a pipe wall and exchange heat;

[0009] The MVR heater includes a heating inlet, a heating outlet, a cooling inlet, and a cooling outlet. The heating inlet and the cooling inlet are located at the upper part of the MVR heater, and the heating outlet and the cooling outlet are located at the lower part of the MVR heater. The heating inlet and the heating outlet are connected through a third flow channel inside the MVR heater, and the cooling inlet and the cooling outlet are connected through a fourth flow channel inside the MVR heater. The third flow channel and the fourth flow channel are separated by a pipe wall and exchange heat;

[0010] A heating circulation pipe is provided at the lower part of the evaporation tower. The heater is provided on the heating circulation pipe. A liquid outlet pipe is provided at the bottom of the evaporation tower. The liquid outlet is connected to the lower part of the evaporation tower. An evaporation pipe connected to the heating inlet is provided at the top of the evaporation tower. The MVR steam compressor is provided on the evaporation pipe. The circulation pump transports the liquid at the lower part of the evaporation tower to the cooling inlet, and the cooling outlet is connected to the bottom of the evaporation tower through a liquid return pipe;

[0011] The heating outlet is connected to the reflux tank. The outlet of the reflux tank is connected to the steam inlet through a pipe. The reflux pump is provided on the pipe.

[0012] Specifically, a gas return port communicating with the fourth channel is further provided at the lower part of the MVR heater. The gas return port is higher than the cooling outlet and is connected to the lower side wall of the evaporation tower through a gas return pipe.

[0013] Specifically, a temperature sensor is provided at the top of the evaporation tower. When the temperature at the top of the tower sensed by the temperature sensor is higher than the preset temperature, the MVR steam compressor is turned on, and when it is lower than the preset temperature, the MVR steam compressor is turned off.

[0014] Furthermore, a branch connecting from the outlet section of the reflux pump to the upper part of the evaporation tower is also provided on the pipe.

[0015] Specifically, a liquid outlet pump is provided on the liquid outlet pipe.

[0016] The beneficial effects of the technical solution of the present utility model are:

[0017] In this system, the MVR steam compressor pressurizes and heats up the steam that has reached the boiling point as an auxiliary heat source for the evaporation tower, and also uses the heat of the wastewater as the heat source for the preheater, so that the heat is utilized more fully, effectively saving energy consumption. Description of the Drawings

[0018] Figure 1 It is a pipeline schematic diagram of the low-energy consumption solvent evaporation recovery system for the embodiment.

[0019] The numbers in the figure represent:

[0020] 1 - Preheater, 11 - Liquid inlet, 12 - Liquid outlet, 13 - Preheated liquid inlet, 14 - Preheated liquid outlet;

[0021] 2 - Evaporation tower, 21 - Evaporation tube, 22 - Temperature sensor, 23 - Return branch;

[0022] 3 - Heater, 31 - Heating circulation pipe;

[0023] 4 - MVR steam compressor;

[0024] 5 - MVR heater, 51 - Heating inlet, 52 - Heating outlet, 53 - Cooling inlet, 54 - Cooling outlet, 55 - Gas return port;

[0025] 6 - Return tank;

[0026] 7a - Circulation pump, 7b - Return pump, 7c - Liquid outlet pump;

[0027] 8 - Liquid outlet pipe;

[0028] 9a - Liquid return pipe, 9b - Gas return pipe. Detailed implementation mode

[0029] The present utility model will be further described in detail below in conjunction with specific embodiments.

[0030] Embodiment:

[0031] As Figure 1 shown, a low - energy - consumption solvent evaporation and recovery system of the present utility model includes a preheater 1, an evaporation tower 2, a heater 3, an MVR steam compressor 4, an MVR heater 5, a return tank 6, a circulation pump 7a, a return pump 7b and a liquid outlet pump 7c.

[0032] As Figure 1 shown, the preheater 1 includes a liquid inlet 11, a liquid outlet 12, a preheated liquid inlet 13 and a preheated liquid outlet 14. The liquid inlet 11 and the liquid outlet 12 are connected through a first flow channel in the preheater 1, and the preheated liquid inlet 13 and the preheated liquid outlet 14 are connected through a second flow channel in the preheater. The first flow channel and the second flow channel are separated by a pipe wall and exchange heat. The liquid outlet 12 is connected to the lower part of the evaporation tower 2.

[0033] An aqueous solution containing 10% - 35% dimethylacetamide (DMAC) will enter the preheater 1 from the liquid inlet 11. During the process of passing through the first flow channel, the temperature of the solution rises from room temperature to 50 - 60 °C, and then enters the evaporation tower 2. The temperature in the evaporation tower 2 needs to be heated to between the boiling point of dimethylacetamide and the boiling point of water so as to achieve the purpose of fractional distillation. What remains at the bottom of the tower is the concentrated aqueous solution of dimethylacetamide (content about 75%), and what is discharged from the system is the evaporated water, and this part of water is also the heating source flowing through the second flow channel.

[0034] As shown Figure 1 in the figure, a heating circulation pipe 31 is provided at the lower part of the evaporation tower 2, a heater 3 is arranged on the heating circulation pipe 31, a temperature sensor 22 is provided at the top of the evaporation tower 2. When the temperature at the top of the tower sensed by the temperature sensor is higher than the preset temperature, the MVR steam compressor 4 is turned on, and when it is lower than the preset temperature, the MVR steam compressor 4 is turned off.

[0035] The direct heating source outside the evaporation tower 2 is the heater 3. The heater 3 heats the solution at the bottom of the evaporation tower 2, vaporizes it through the heating circulation pipe 31, and then returns it to the evaporation tower 2, forming a temperature gradient with a low temperature at the top and a high temperature at the bottom in the evaporation tower 2 and raising the temperature together. Since the boiling point of water is 100°C at room temperature and the boiling point of dimethylacetamide is 165°C at room temperature, the preset temperature is generally controlled at a temperature slightly higher than 100°C and lower than 165°C. When the temperature at the top of the tower just exceeds 100°C, water vapor will evaporate, and at this time, it is necessary for the MVR steam compressor 4 to compress and raise the temperature of the steam.

[0036] As shown Figure 1 in the figure, the MVR heater 5 includes a heating inlet 51, a heating outlet 52, a cooling inlet 53, a cooling outlet 54 and a gas return port 55. The heating inlet 51 and the cooling inlet 53 are located at the upper part of the MVR heater 5, and the heating outlet 52, the cooling outlet 54 and the gas return port 55 are located at the lower part of the MVR heater 5. The heating inlet 51 and the heating outlet 52 are connected through a third flow channel inside the MVR heater 5, and the cooling inlet 53, the cooling outlet 54 and the gas return port 55 are connected through a fourth flow channel inside the MVR heater 5. The third flow channel and the fourth flow channel are separated by a pipe wall and exchange heat. An evaporation pipe 21 connected to the heating inlet 51 is provided at the top of the evaporation tower 2, and the MVR steam compressor 4 is arranged on the evaporation pipe 21. The heating outlet 52 is connected to a reflux tank 6. The circulation pump 7a transports the liquid at the lower part of the evaporation tower 2 to the cooling inlet 53. The cooling outlet 54 is connected to the bottom of the evaporation tower 2 through a liquid return pipe 9a. The gas return port 55 is higher than the cooling outlet 54 and is connected to the lower side wall of the evaporation tower 2 through a gas return pipe 9b.

[0037] The MVR steam compressor 4 can compress steam with a temperature exceeding 100 °C to form secondary steam with a higher temperature and pressure. The temperature of the secondary steam will reach 120 °C and then be supplied to the MVR heater 5 for use. The MVR heater 5 is equivalent to a heat exchanger. Since the temperature of the bottom solution of the tower is relatively low, the heat of the secondary steam will be transferred to the bottom solution of the tower, playing the role of the first heat recovery. After the heat transfer and pressure release of the secondary steam, it becomes liquid and enters the reflux drum 6. After heating, a part of the solution flowing back from the bottom of the tower will be vaporized, but it also needs to return to the lower part of the evaporation tower 2. Therefore, a gas reflux pipe 9b needs to be set for the steam reflux so that while the liquid refluxes through the liquid reflux pipe 9a, the vaporized liquid can also directly return to the evaporation tower 2.

[0038] As Figure 1 shown, the outlet of the reflux drum 6 is connected to the steam inlet 13 through a pipeline. The reflux pump 7b is arranged on the pipeline, and a branch 23 connecting to the upper part of the evaporation tower 2 is also connected to the outlet section of the reflux pump 7b on the pipeline.

[0039] The liquid in the reflux drum 6 is mainly water and will eventually be discharged from the system. However, at this time, its temperature is 70 - 90 °C. If it is directly discharged, the heat is wasted. Therefore, this high-temperature water is used as the heat source of the preheater 1. In this way, the water flowing out from the preheated liquid outlet 14 has a lower temperature, but the initial temperature of the dimethylacetamide aqueous solution entering the evaporation tower 2 will increase, thus reducing the energy consumption of the heater 3. A part of the water sent out by the reflux pump 7b from the reflux drum 6 will return to the top of the evaporation tower 2. Since the temperature at the top of the tower must be controlled below 165 °C, this reflux water can inhibit the temperature at the top of the tower, reduce the evaporation of dimethylacetamide, and ensure the safety of the operation.

[0040] As Figure 1 shown, a liquid outlet pipe 8 is provided at the bottom of the evaporation tower 2, and the liquid outlet pump 7c is arranged on the liquid outlet pipe 8.

[0041] When the liquid outlet pump 7c is not started, it is equivalent to a closed valve. When the concentration of dimethylacetamide at the bottom of the evaporation tower 2 exceeds 75%, a part can be discharged; when the concentration of dimethylacetamide at the bottom of the evaporation tower 2 is lower than 75%, the liquid outlet pump 7c is closed. The above process alternates, and the concentration of the dimethylacetamide aqueous solution can reach a dynamic balance.

[0042] This system uses an MVR steam compressor 4 to pressurize and heat up the steam that has reached its boiling point as an auxiliary heat source for the evaporation tower 2, and also uses the heat of the wastewater as the heat source for the preheater 1, enabling more efficient use of heat. According to experience, a conventional distillation system requires 12 tons of gas to concentrate 18 tons of a 10% - 35% dimethylacetamide aqueous solution, while this system only requires 6 tons of gas to concentrate the same equivalent of dimethylacetamide aqueous solution, achieving a 50% energy savings. The working purpose of this system is essentially to concentrate components with low concentration and high boiling point, so it can also be used in other distillation scenarios where the boiling point of the effective component is higher than that of the ineffective component, as long as the set temperature is adjusted between the boiling points of the two new components.

[0043] The above are only some embodiments of the present utility model. For those of ordinary skill in the art, without departing from the creative concept of the present utility model, several modifications and improvements can still be made, and these all fall within the protection scope of the present utility model.

Claims

1. A low energy consumption solvent evaporation recovery system, characterized in that: Including preheater, evaporation tower, heater, MVR steam compressor, MVR heater, reflux tank, circulation pump and reflux pump; The preheater comprises a liquid inlet, a liquid outlet, a preheating liquid inlet and a preheating liquid outlet, the liquid inlet and the liquid outlet are connected in the preheater through a first flow channel, the preheating liquid inlet and the preheating liquid outlet are connected in the preheater through a second flow channel, the first flow channel and the second flow channel are separated by a tube wall and perform heat exchange; The MVR heater comprises a heating inlet, a heating outlet, a cooling inlet and a cooling outlet, wherein the heating inlet and the cooling inlet are located at an upper portion of the MVR heater, and the heating outlet and the cooling outlet are located at a lower portion of the MVR heater, the heating inlet and the heating outlet are communicated with each other through a third flow channel in the MVR heater, the cooling inlet and the cooling outlet are communicated with each other through a fourth flow channel in the MVR heater, and the third flow channel and the fourth flow channel are separated by a tube wall and perform heat exchange; The lower part of the evaporation tower is provided with a heating circulation pipe, the heater is arranged on the heating circulation pipe, the bottom of the evaporation tower is provided with a liquid outlet pipe, the liquid outlet is connected to the lower part of the evaporation tower, the top of the evaporation tower is provided with an evaporation pipe connected to the heating inlet, the MVR steam compressor is arranged on the evaporation pipe, the circulation pump transports the liquid at the lower part of the evaporation tower to the cooling inlet, and the cooling outlet is connected to the bottom of the evaporation tower through a liquid reflux pipe; The heating outlet is connected to the reflux drum, the outlet of the reflux drum is connected to the steam inlet through a pipeline, and the reflux pump is arranged on the pipeline.

2. The low energy consumption solvent evaporation recovery system according to claim 1, characterized in that: The lower part of the MVR heater is also provided with a gas return port connected to the fourth flow channel. The gas return port is higher than the cooling outlet and is connected to the lower side wall of the evaporation tower through a gas return pipe.

3. The low energy consumption solvent evaporation recovery system according to claim 1, characterized in that: A temperature sensor is provided on the top of the evaporation tower. When the tower top temperature sensed by the temperature sensor is higher than a preset temperature, the MVR steam compressor is turned on; when the tower top temperature is lower than the preset temperature, the MVR steam compressor is turned off.

4. The low energy consumption solvent evaporation recovery system according to claim 3, characterized in that: The pipeline is also connected from the outlet section of the reflux pump to a branch at the upper portion of the evaporation tower.

5. The low energy consumption solvent evaporation recovery system according to claim 1, characterized in that: The liquid outlet pipe is provided with a liquid outlet pump.

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