multi-effect evaporation

There aren’t many people who truly understand this. I’ve also worked on this process, but I didn’t fully grasp the aspects related to vacuum technology before leaving my job. The formulas for calculating quantities are provided by the manufacturer; if you have any relevant information, could we exchange it so that we can learn from each other?*

The requirements are quite high; who are you anyway? Those who truly understand it might not be willing to help you

The evaporation system used for urea concentration can be used as a reference; most systems in use currently employ two-stage evaporation, with water or steam being used for vacuum creation

It should be the evacuation of non-condensable gases resulting from the cooling of post-evaporation gases.

Multiple trials have been conducted to determine the vacuum level required to lower the boiling point; for some materials, there is little relationship between vacuum level and boiling point, which results in high energy consumption and makes it uneconomical. It’s listed in the calculation sheet; the key is the empirical value.

The pumping capacity of a vacuum pump is primarily determined by the condensation efficiency of the condenser located before the vacuum pump, as well as the amount of non-condensable gases present in the raw water. The vacuum level at each stage is self-balanced by the final-stage vacuum level, the heating steam used in the first stage, the material concentration in each stage, and the heat exchange area.

In the multi-effect evaporation systems you have worked with, is the heat exchange area of each effect made consistent?

It is also common to make the heating area of each effect the same.

Thank you for the guidance. If three-effect counter-current evaporation is used with the same heat exchange area for each effect, can it be assumed that the secondary evaporation pressure difference between adjacent effects, as well as the amount of water evaporated in each effect, are roughly equal?

Firstly, the evaporation volume in multi-effect evaporation decreases step by step, and it is not essentially equal. As the pressure decreases, the vaporization latent heat of the steam increases; the next stage is supplied with heat by the secondary steam from the previous stage, and according to the law of conservation of energy, the amount of evaporation decreases continuously. The pressure difference and temperature difference of the secondary steam between adjacent stages are also not equal: the temperature difference of the secondary steam between adjacent stages increases from stage to stage (mainly due to the rising boiling point of the material from stage to stage and the decreasing heat transfer coefficient). The pressure difference between the secondary steam of adjacent effects gradually decreases. As can be seen from the saturated steam pressure thermometer, as the pressure drops, the effect of pressure changes on temperature becomes increasingly noticeable. Therefore, the pressure of the secondary steam between adjacent effects gradually decreases.