A system and method for condensing and thermally rectifying gaseous fractions at the top of the tower

Abstract

The invention belongs to the fields of rectification and energy conservation and relates to a rectifying system and a rectifying method utilizing tower top gas-phase fraction condensation heat. In the rectifying system, water in a water storage tank and a gas-phase fraction distilled from the top of a rectifying tower perform heat exchange in a condensation and vaporization heat exchanger, water is vaporized into water vapor by the condensation and vaporization heat exchanger, the temperature of the water vapor is increased by a vapor compressor, high-grade water vapor with high temperature is obtained, and the high-grade water vapor can serve as a heating heat source of a reboiler or a raw material preheater, so that the potential heat of the tower top gas-phase fraction is utilized. According to the system and the method, consumption of externally supplied water vapor in the operating process of the rectifying tower is reduced, cooling water for condensation of the tower top gas-phase fraction is omitted, and the aims of saving energy and reducing consumption are fulfilled.

Description

technical field [0001] The technical field of rectification and energy saving of the present invention relates to a system and a method for rectifying heat by condensing gas phase fractions at the top of a tower. Background technique [0002] Due to its excellent separation ability, rectification operation is widely used in various fields of life and production. It is an important unit operation in the separation process. However, the rectification process consumes a lot of energy, and the energy utilization rate is not high. According to statistics, traditional The total energy consumed by the rectification operation accounts for about half of the total energy consumption of industrial production, which is a key step that restricts the entire production process; for example, although the production process of propylene oxide technology by HPPO method is simple, the product yield is high, and it is in line with green Clean production requirements, but the production process ...

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Problems solved by technology

[0002] Due to its excellent separation ability, rectification operation is widely used in various fields of life and production. It is an important unit operation in the separation process. However, the rectification process consumes a lot of energy, and the energy utilization rate is not high. According to statistics, traditional The total energy consumed by the rectification operation accounts for about half of the total energy consumption of industrial production, which is a key step that restricts the entire production process; for example, although the production process of propylene oxide technology by HPPO method is simple, the product yield is high, and it is in line with green Clean production requirements, but the production process needs to use a large amount of methanol as a solvent. After the product is separated, the methanol solvent must be rectified. However, in the operation of a conventional rectification system, the cooling condenser at the top of the tower generally uses cooling water to separate the gas phase at the top of the tower. The distillate is cooled and condensed, and part of the condensate is returned to the first tray at the top of the tower; the bottom reboiler generally uses external steam to heat and evaporate part of the liquid fraction at the bottom of the tower and then returns to the first tray at the bottom of the tower On the one hand, to maintain the rectification operation, on the one hand, the cooling condenser at the top of the tower needs to consume a large amount of cooling water; Improving the energy utilization rate in the rectification process, thereby reducing the energy consumed in the entire rectification process, has become the research focus of many scholars.

Chinese patent CN205287681U discloses a rectification energy-saving device for producing MBET. This device realizes accurate measurement of the temperature inside the tower by designing the heater and condenser of the rectification tower. Under the condition of ensuring the purity of the product, Reduce the temperature in the tower as much as possible to achieve the purpose of energy saving, but this method does not effectively use the heat from the top and bottom products of the rectification tower, and the energy saving effect is not very significant

Chinese patent CN204815741U discloses a rectification energy-saving device. This device extracts part of the material produced in the tower reactor, and the other part is turned into steam through throttling and expansion, and exchanges heat with the tower reactor feed liquid, and then enters the rectification tower through compression. , as reflux, the device effectively utilizes the energy generated by the tower kettle, which reduces the energy consumption of the rectification process to a certain extent, but does not make reasonable use of the large amount of latent heat at the top of the tower, and there is still a long way to go before the real energy saving and consumption reduction big gap

Chinese patent CN205549650U discloses a heat pump rectification system. The system is aimed at the ethanol rectification system. The ethanol vapor obtained at the top of the tower is compressed and heated, and then reused as a heat source for the reboiler. Although this system effectively utilizes the The heat brought out by the top stream, but the ethanol vapor is not suitable for direct compression, and there are safety hazards in the operation process, which limits the application field of the system to a certain extent

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