4 replies to this topic

[gu211]

Hello all,

 

I was just wondering if anyone knew a good reference for refrigerant choice for a total condenser for a vacuum distillation at 8 mmhg: to condense water that boils at 7.7 °C. Though this temperature value might increase slightly when the column is optimised in Aspen. 

 

The system is described in another post in the student forum: https://www.cheresou...llation-design/

My supervisor had mentioned the use of Ethylene Glycol if I'm not mistaken, but I can't seem to find any reference in the literature.

 

Thank you,

 

Have a nice day!

 

Gualtiero

[Pilesar]

Research "chilled glycol water system" on the world wide web. Choice of cooling medium depends on utilities available and total area cooling needs. A packaged water/glycol chilling system can be a good choice under some circumstances. You can certainly reach the utility temperature you need.

[gu211]

Research "chilled glycol water system" on the world wide web. Choice of cooling medium depends on utilities available and total area cooling needs. A packaged water/glycol chilling system can be a good choice under some circumstances. You can certainly reach the utility temperature you need.

 

Thank you Pilesar!  I'll give it a look and try to quantify the amount I need, so I can calculate condenser operating cost! Would you say that chilled glycol water is a commonly used refrigerant?

[Pilesar]

The glycol/water circuit (generally 50/50 mix like would be in an automobile) is not uncommon. Glycol/water is used as a medium to transfer heat from the process to a refrigeration system. You will have to determine the flowrate and temperature of glycol/water you require when you size your heat exchanger. This circuit is not part of the 'package' from the vendor. The refrigerant package consists of compressor and freon circuit which is used to chill the circulating glycol/water mix. These refrigerant packages are offered in 'standard sizes' pre-engineered by vendors who supply them mounted on a skid. Once you determine the flow, duty and temperature of glycol/water you need, then you choose the refrigerant package that best fits while still having extra capacity. There is usually some equipment design iteration required since the closed glycol/water circuit should match the refrigerant capabilities. The details are somewhat tricky since it can be difficult to assess how the vendor refrigerant package will perform under various process loads.

   Because you are purchasing a refrigerant compressor, this system is not a cheap option compared to using cooling tower water for condensing at a warmer temperature.

[Technical Bard]

The lowest cost refrigerant for this would be butane.