The impact of the subcooling specification option for the condenser.
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This post was last edited by Wille on 2009-12-16 at 16:43. In continuous distillation, when defining the blocks, under design-specific conditions (such as setting the product quality rate to 0.995 and the reflux ratio as a variable), if a subcooling specification for the condenser is entered that is below the boiling point of the substance (I usually don’t enter such a value; by default, it is assumed that the condenser simply liquefies the gas), it will be found that the required reflux ratio decreases in the operational results, while the total heat duty of the condenser and its subcooling duty remain more or less the same as when no such specification was entered. Of course, the quality of the products remains unchanged. I removed the design constraint to keep the reflux ratio constant; here, the reflux ratio is no longer a variable. By changing the value of the subcooling specification (decreasing it), the power consumption of the condenser increases significantly (as is inevitable). The lower the value of the subcooling specification, the better the separation effect. In other words, under the specified design conditions, if the gas at the top is cooled further using a condenser to achieve the same separation effect, a lower reflux ratio is required, and there is not much increase in the power consumption of the condenser. Reaching an optimization – is that correct?
The person upstairs is definitely a thinker!
1# Wille I’m a bit confused – after the design specifications were removed, why did the reflux ratio increase? Did the original poster change the reflux ratio? To compare the reflux ratio under the same separation efficiency, energy consumption also comes into play.
Thank you, onlyforyou; I was wrong. It is independent of the reflux ratio. What I mean is that after removing the design regulations, it is necessary to achieve the same level of separation that was obtained under those regulations. With the reflux ratio kept constant, when the value of the subcooling specification is changed (decreased), the power consumption of the condenser increases significantly (as is inevitable). The smaller the value of the subcooling specification, the better the effect.
Cold reflux is commonly used in practice, and it is difficult for industries to control the bubble point temperature. I have also thought about this issue: after cold reflux, the temperature of the liquid phase carried out from the top of the tower is low. Meanwhile, as the temperature difference increases from bottom to top, the recombined components in the gas phase are more likely to enter the liquid phase (as the gas absorbs heat), making the separation conditions easier. I’m not sure if the analysis is correct; please point out any mistakes! !