How to condense saturated steam below its boiling point
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I have a question for everyone. Toluene has a boiling point of 110°C at normal pressure. The reaction vessel needs to be under vacuum, with a required vacuum level of -0.08 MPa. From what I’ve found, toluene boils at 60°C under this pressure level. However, the temperature in the reaction vessel needs to be maintained at 40°C. As a result, some of the saturated steam of toluene at 40°C is removed by the vacuum. How can this vapor be condensed?
Saturated steam below the boiling point can be condensed using a condenser. In this case, a condenser can be connected to the outlet of the reactor; the toluene saturated vapor at 40°C is directed into the condenser, where it is cooled to turn into a liquid state, allowing it to be collected. Normally, water or air can be used to cool the condenser in order to reduce the temperature. .
Then I have one more small question: I didn’t master university physical chemistry well. That is, for toluene at 40°C, its saturated vapor temperature should also be 40°C, right?
When saturated steam below its boiling point condenses, this process can be carried out through heat transfer, via conduction or convection, based on the principles of heat transfer. Specifically, a low-temperature condensing medium (such as water or coolant) can be brought into contact with steam through heat transfer devices such as condensers or heat exchangers, allowing it to absorb the heat from the steam and thereby cool the steam until it condenses into a liquid. Furthermore, low-temperature condensation can also be achieved using physicochemical methods such as adsorption and coagulation. For example, by placing steam into a specific adsorbent material, the tiny pores on the surface of this material can absorb the steam molecules, thereby achieving condensation. .
Condensation through heat exchange with refrigerant at sub-dew point temperature
Thank you. I also have a question: if I install a heat exchanger downstream to use circulating water for condensation, can the 40°C toluene vapor be condensed? The temperature of the circulating water is around 25°C℃
Hello, I would like to ask if there are any temperature requirements for this refrigerant medium; is it sufficient as long as its temperature is lower than that of toluene vapor at 40°C?
The lower the temperature of the refrigerant medium, the more favorable it is for the condensation of toluene vapor; a larger temperature difference between the two is beneficial for condensation.
The pressure at the vacuum pump outlet is increased to an appropriate level, and condensation is achieved using cooling water, either low-temperature water
Use circulating water for cooling: the temperature of the circulating water is 30–40°C. Use cold water for cooling: the water temperature is generally around 5°C. There are also low-temperature cooling methods such as ammonia cooling
Under high vacuum, you need to perform cryogenic cooling in order to keep the toluene concentration in the exhaust gases low enough. It is recommended to consider the option for the 11th floor, with the vacuum pump outlet featuring a multi-stage condensation system similar to this one using circulating water and brine.