MVR Distillation Technology:
MVR is the abbreviation of Mechanical Vapor Recompression, which is an energy-saving technology that uses compressed secondary vapor as a heat source to reduce the demand for external energy.
MVR technology consumes a small amount of compressor compression work to upgrade the large amount of low-grade waste heat carried by secondary vapor to high-grade for reuse, so it is also called MVR heat pump technology. Combining MVR heat pump technology with traditional distillation production processes, fully recovering the latent heat of tower top vapor, and reducing the consumption of cold and hot utilities in the distillation system.
MVR heat pump distillation technology only consumes heating vapor during the start-up phase of the distillation system. After stable operation, the compressed high-temperature and high-pressure secondary vapor is used as the system heat source, saving energy by more than 40%, which is helpful to reduce the energy consumption of the distillation process and solve the problem of high energy consumption in the chemical industry.
Classification Of MVR Distillation System
MVR Distillation Process Scheme:
MVR heat pump distillation is generally suitable for distillation processes with small temperature difference between the top and bottom of the tower. Since the compression ratio of the steam compressor generally does not exceed 2, if the temperature of the tower bottom is too high, the condensation temperature of the steam after one compression is difficult to meet the temperature difference required for heat exchange in the tower bottom. ENCO has a single-stage distillation unit and a multi-stage MVR stripping unit. The number of configuration stages of the multi-stage MVR stripping unit is determined according to the raw material composition and the purity requirements of the separation. According to the different locations of the MVR stripping unit, it is divided into a multi-stage MVR stripping unit and an intermediate-stage MVR stripping unit. The specific process scheme is as follows:
① MVR-conventional two-tower distillation process;
MVR-conventional two-tower distillation process flow. T1 tower adopts MVR heat pump distillation and concentration, and T2 tower adopts conventional distillation. Both towers are operated at normal pressure. The steam V1 at the top of T1 tower enters the compressor for compression and then increases the temperature and pressure to provide heat for the reboiler at the bottom of T1 tower. After the condensate is reduced in pressure, part of it is refluxed and part of it is extracted as wastewater. The TI tower bottom liquid (DMAC concentrate) enters the T2 tower, and the remaining water is removed at the top of the tower in the T2 tower. The T2 tower bottom liquid is the qualified DMAC finished product. The T1 tower is heated by compressed steam, and the T2 tower is heated by external steam.
② Three-stage MVR single-tower distillation process;
Three-stage MVR single-tower distillation process flow. Since the DMAC finished product is obtained at the bottom of the tower, the temperature of the tower bottom material is about 155℃ (bubble point temperature when the DMAC content is 99%). Single-stage compression cannot make the top tower steam temperature meet the requirements of the tower bottom heat transfer temperature difference, so multi-stage compression must be used to increase the top tower steam temperature. According to the tower bottom temperature and the specified heat transfer temperature difference (15℃), it can be seen that the steam temperature leaving the final compressor should reach 170℃ (155+15=170℃, saturation temperature), and the corresponding pressure is 0.8 MPa (absolute). The tower adopts normal pressure operation, and the compression ratio of each stage is specified to be 2, so three-stage compression can meet the process requirements. The whole system does not need external steam heating, and all energy consumption is provided by the compressor.
③ Three-stage MVR three-tower distillation process.
Three-stage MVR three-tower distillation process flow. All three towers are operated at normal pressure, and the steam at the top of the tower is collected and enters the C1 compressor. The steam part after the first compression is heated by the reboiler at the bottom of the TI tower, and part enters the C2 compressor for recompression; the steam part of the second compression is heated by the reboiler at the bottom of the T2 tower, and part enters the C3 compressor for the third compression; the steam of the third compression is all heated by the reboiler at the bottom of the T3 tower. After the condensate after heat exchange at the bottom of the three towers is reduced in pressure, part of it is distributed to each tower for reflux, and part of it is extracted as wastewater. The whole system does not need external steam heating, and all energy consumption is provided by the compressor.
Advantages Of MVR Distillation Technology:
Distillation technology, that is, compressing the water vapor at the top of the tower through a mechanical steam compressor, increasing its temperature and pressure, and condensing it in the reboiler to transfer heat to the material at the bottom of the tower, and only using the compressor to maintain the energy balance of the distillation system. A small amount of electricity is used to improve the thermal grade of the steam at the top of the tower, and the latent heat of vaporization of the steam at the top of the tower is efficiently recovered, which reduces the heat supply at the bottom of the tower and reduces the consumption of cooling capacity at the top of the tower, thereby achieving the purpose of energy saving.
①Distillation technology can save 90% of steam and circulating cooling water, saving considerable operating costs.
② The Distillation and stripping composite device and its process method designed by ENCO belong to the field of distillation process technology. Through the efficient coupling of distillation process and stripping process, the process energy consumption of liquid mixture separation can be significantly reduced.
③ It is simple and easy to operate, has strong adaptability to changes in the concentration ratio of raw material liquid, and has large operational flexibility. While saving energy consumption, it can make the separation of the mixed liquid more thorough, significantly improve the purity of the separated liquid, and meet the process production requirements.
Scope of application of Distillation technology
MVR heat pump distillation technology is suitable for the separation of small temperature difference systems such as ethanol-isopropanol, which can greatly reduce the energy consumption of the separation process. It is especially suitable for the recovery of low-concentration and high-boiling point organic solvents (such as DMF, DMSO, DMAC, etc.), and can also be used for the concentration of solvents such as ethanol, methanol, and dichloromethane.
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