Discussion on the decision-making and practice of heat pump distillation
The heat pump technology is adopted in the domestic Jinzhou refinery and Jiujiang refinery propane-propylene separation unit, which saves a lot of energy consumption. Heat pump rectification is an inverse Carnot cycle system that supplies heat to the bottom of the tower and to the top of the tower. The energy saving effect is remarkable. Therefore, it is important to use heat pump distillation to reduce energy consumption and cost to improve economic efficiency in the rectification process. The practical significance. But how to apply heat pump distillation in production is the difficulty of process integration and process strengthening. To this end, a hierarchical strategy is proposed to solve the optimal heat pump distillation process, and each layer is solved separately, so that the complexity of constructing a better heat pump distillation process is better solved, and the application research proves The feasibility of the strategy. Heat pump heating must have a clever and matched set of equipment. Due to the different types of equipment used, different types of heat pump production processes are formed. The heat pump is applied to the rectification system and is mostly Yanqi compression type. According to the different working medium, the Yanqi compressor type heat pump rectification can be divided into two types: closed heat pump and open heat pump. The common process structure is kind. The open type should be connected to the Yanqi compression heat pump rectification diagram. The open heat pump rectification is the heat pump rectification with the overhead gas as the working medium. The gas at the top of the rectification tower is compressed by the compressor and then enters the bottom reboiler. The condensation heat is released to make the kettle liquid reboil. After the condensate is depressurized and cooled by the throttle valve, a part is discharged as a product, and the other part is used as a reflux of the top of the distillation column. It eliminates the overhead condenser and replaces it with a bottom reboiler, which in effect uses a heat exchanger as both a top condenser and a bottom reboiler. Figure open heat pump rectification process shows the rectification column rectification pump compressor throttle valve auxiliary condenser bottom heat exchanger reboiler open heat pump distillation process characteristics required heat transfer medium is ready-made 2 because It is simple, stable and reliable to use only one heat exchanger, that is, a reboiler. The compression ratio of the compressor is usually lower than that of the single-cycle circulation type compression ratio system. The compressor has a narrow operating range and poor control performance, which is easy to cause instability of the tower operation. It needs to be paid attention to during the design, especially in the design of the control system. 5 It cannot be used for separating the product and is not suitable for the distillation operation of the heat carrier medium. Scope of application of open heat pump distillation process The direct heat pump rectification at the top of the tower is suitable for application in the temperature difference between the top of the tower and the bottom of the tower, or the components of the separated system are difficult to separate due to the similar boiling point, and a large reflux ratio must be adopted. A large amount of heated Yanqi, that is, a high-load reboiler, or a top-end condensate, that is, a rectification system in which a fraction needs to be cooled at a low temperature, etc., is used. The open heat pump rectification is shown in the figure. The open heat pump rectification process is to directly reduce the liquid discharge of the tower tank by throttling, and then use it as a refrigerant after cooling. It is sent to the top of the condensing and reboiler for heat exchange, and the heat is absorbed into the vapor, and then heated by the compressor to return to the tower as a heat source. The steam at the top emits heat to form a liquid during the heat exchange process. Characteristics of the open heat pump distillation process This process not only saves the condensing agent å® é˜³ 比 , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , å†·å‡ å†·å‡ å†·å‡ å†·å‡ å†·å‡ å†·å‡The reflux pump compressor throttle valve reduces or avoids the external heat agent, and at the same time, the tower top condenser and the tower kettle reboiler are combined into one, saving one heat exchange device. Scope of application of open heat pump distillation process This process is especially suitable for the tower top product which is not suitable for direct compression and the tower kettle product is vaporized and then compressed. It is especially suitable for normal pressure or pressure, bottom and tower top temperature is less than Distillation process. The tower liquid is clean and non-toxic. Whether the process is economical or not is calculated. It is evaluated after using the optimized design program. The closed heat pump distillation process is shown in the figure. After the heat exchange between the refrigerant and the top material, the heat is evaporated to gas. After the gas is passed through the compressor, the temperature is raised or superheated, and then sent to the tower to heat the kettle liquid. For the liquid, the liquid is depressurized by throttling, and then the heat exchange at the top of the tower is completed to complete a cycle, so that the heat at the low temperature of the top of the tower is transferred to the high temperature of the top of the tower by the action of the refrigerant, that is, the refrigerant is supplied to the top of the tower. Cold, and heat the bottom of the tower. The characteristics of the closed heat pump distillation process are replaced by working medium instead of the top Yanqi steam. The distillation system and the heat pump system form a closed system. The materials are separated from the working medium, and the pressure of the product tower is not polluted, and the pressure of the heat pump is different, which can be easily controlled. Therefore, the material of the process operation stabilization tower and the heat pump system can also be different. The closed heat pump should not only consider the temperature difference of the tower refiller, but also consider the temperature difference of the top condenser, which is the disadvantage of the closed heat pump. The applicable range of the closed heat pump distillation process is applicable to the system with small temperature difference between the top of the tower and the bottom of the tower. The working medium currently being applied limits the maximum output temperature. Steam recompression heat pumps using overhead steam as a heat pump are generally the most economically attractive. Yanqi compressor type heat pump rectification is applied in the following occasions, and it is expected to achieve good results. "The temperature difference between the top of the tower and the bottom of the tower is small. For this complex problem, it should be decomposed into a relatively independent sub-question, and then a sub-problem is combined according to certain steps by a certain solution strategy, and finally the whole problem is solved. Based on this, we propose a hierarchical solution strategy for constructing a multi-component better heat pump distillation process. Analyze the characteristics of the distillation column. Determine the applicability of the heat pump distillation process. Determine the heat pump rectification process. The distillation process is simulated and optimized, and the qualitative and quantitative knowledge is combined to obtain a better process. Applicability of the heat pump rectification process The selection of the heat pump rectification scheme in the rectification process integration is a comprehensive problem. It is important to consider not only the characteristics of the rectification system itself, but also the trade-offs of the entire background process before deciding whether the heat pump rectification scheme is feasible. For an independently operated heat pump, in order to make it economical, the temperature difference across the heat pump must be small. For the distillation column, this means the separation of the mixture of similar boiling points. The applicability rules for heat pump rectification as shown below are summarized as Identify the knowledge of applying a heat pump rectification scheme. Angular Contact Ball Bearing,ISO Angular Contact Ball Bearing,Brass Cage Angular Contact Ball Bearing Kaiming Bearing Co., Ltd , http://www.jn-thrustBearings.com