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condenser cooling with glycol


MikeW

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Is anyone using Glycol straight from a chiller to cool a still's condenser? We are within 4 weeks of installing a 500 gallon still and have glycol plumbed across the ceiling directly past the place where the condenser will be. It would be very simple to plumb it straight into the condenser and out the top, back into the loop. It is chilled to 31 F. I know there must be a downside.

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Hi Mike,

You need to make sure that your glycol chiller system has enough extra capacity that the added btu/hr load from the still's condenser doesn't overload your chiller system.

Kind regards,

Damon.

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If you're using your glycol to cool your fermenters, that's a bad idea, imho. You'd be adding a heck of a load if you use it directly, and it's unlikely that your chiller can handle that unless you REALLY oversized the unit.

What you could do is chill a cold water tank that's jacketed using that glycol, and use the cooled water from that tank to cool the condenser on your still. However, you'd need a jacketed tank, as well as a pump to push the cooled water through the condenser.

You'd save water, but lose watts and $$ on equipment.

IMHO, leave the glycol alone unless the volume of your wastewater is a serious concern.

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I failed to mention, that we have a chiller that was handling everything we have, PLUS 8, 20 barrel fermenters that are no longer there. So we have a lot of extra chiller capacity. Also, someone may want to know, the condenser is made of copper.

Other than capacity of the chiller, are there other problems?

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It will still likely not have enough capacity if you're running glycol directly into the condenser. I'm speaking in generalities, since I obviously don't know the surface area of the condenser on your still, nor the rate that the chiller is pumping glycol across that surface area, but........

Think of what you're asking it to do: the glycol enters the pot still's condenser at ~32 F. At that condenser, the glycol now hits hot copper. Really hot copper. Depending on how you run your tails, parts of that copper will head well north of 190 degrees F (obviously the condenser temp won't be uniform). Do you think that the glycol chiller is going to be able take the hot glycol entering the heat exchanger in the chiller unit from well over 120 degrees, and cool it to 31 F at the exit? 20 barrel fermenters, by comparison, are really no load at all. The fermenter load is a fairly steady load with no spikes until you crash cool. When you run that still, you'll have a heck of a spike. Especially if you're running a 500 gallon still.

The chiller you bought wasn't designed to do this. It's taking glycol that's at room temperature and dropping it down 40 or 50 degrees.....not 150 or so degrees. Further, balancing the unit will be difficult because don't want your distillate coming off too cold or too hot.

Your best bet is to ignore me and call the chiller manufacturer and get the real scoop before trying something outside of the SOP for the unit.

What you could also do is run the glycol through a little plate and frame heat exchanger and run city water through the other side, cooling the city water on the way to the condenser. That would be a fairly light load, especially in the winter (assuming you have a cold winter and are using muni water, that is). This would make everything much simpler, and would save you water---but again, at the expense of electricity.

This is just my opinion, but chillers are enough of a PITA as it is. I wouldn't use glycol to directly chill a still condenser. Particularly if you're depending on it to cool any other processes. Indirect cooling is another story , as I mentioned above.

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Mike,

Denver makes some very good observations. The first one that comes to mind for me is the possability of cross contamination. if you have even the slightest leak in your condenser, you'd be getting glycol in your product instead of just water. The tank and recirc idea is a favorite of mine. pick a small low voltage pump and chill any tank it a simple immersion chiller and cycle the tank through your heat exchanger(condenser). I've heard a small amount of alcohol would keep your water from building bacteria, maybe tails at around 10% would be a good idea. you could even put a cheap temp controller on your return to only run the pump sporatically. not sure that would be best though. again, this all depends on a lot of variables and should have a good deal of "what if analysis" done before moving on anything. good luck!

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Mike,

Denvers responses are exactly what you should be concerned of when considering the high glycol temperatures that can come back to the chiller system from the still. With the high return temperatures, what could happen to your chiller is the refrigerant pressure will gradually increase beyond the reocmmended operationg ranges and create issues with compressor motor winding cooling and high refrigerant condensing pressures (both very bad). One thing that we offer to protect our chiller systems from this type of condition is to add a crank case pressure regulating valve, this valve is added to the refrigerant suction line and limits the pressure that the compresser will ever see.

If your wastewater is a major concern, I would urge you to consider using the cold liquor tank Denver suggested. There are manufacturers of stainless steel immersion coils and also strap on glycol coils - these can be used on non-jacketed tanks. You could use a valve to shut off the glycol supply to this tank when it's being used and then regulate the amount of glycol flow through the jacket manually to allow the tank to cool down during the evenings.

Shoot me an email if you want to discuss this further or if you'd like some suggestions on where to locate these jackets/coils.

damonr@prorefrigeration.com

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Think about running high proof and water instead of glycol. It won't freeze and if there is cross contamination you won't glycol in your spirit.

Mike,

Denvers responses are exactly what you should be concerned of when considering the high glycol temperatures that can come back to the chiller system from the still. With the high return temperatures, what could happen to your chiller is the refrigerant pressure will gradually increase beyond the reocmmended operationg ranges and create issues with compressor motor winding cooling and high refrigerant condensing pressures (both very bad). One thing that we offer to protect our chiller systems from this type of condition is to add a crank case pressure regulating valve, this valve is added to the refrigerant suction line and limits the pressure that the compresser will ever see.

If your wastewater is a major concern, I would urge you to consider using the cold liquor tank Denver suggested. There are manufacturers of stainless steel immersion coils and also strap on glycol coils - these can be used on non-jacketed tanks. You could use a valve to shut off the glycol supply to this tank when it's being used and then regulate the amount of glycol flow through the jacket manually to allow the tank to cool down during the evenings.

Shoot me an email if you want to discuss this further or if you'd like some suggestions on where to locate these jackets/coils.

damonr@prorefrigeration.com

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