I’m posting this thread in an effort to incorporate all the modifications that can improve the output of a CM still. In one easy to find thread. Lets face it the two main suppliers of good quality reflux stills. Both sell CM stills. Mile High and Brewhaus. Not everyone wants to or has the ability to build a still. That’s where these company’s step in and provide a decent still for those customers. I didn’t say it was the best. But they can produce a good product. If used in the best way possible. With more and more of these popping up every day. I felt we should provide those owners with the needed information to get the most out of their investment. So if we could please just keep this thread about improving of a CM still. So those who need the help don’t have to wade through a bunch of non relevant information. To get what they need to do so. So lets get to it.
Little about what a CM still is.
Taken from Kiwistiller’s thread Basic Overview of Common Reflux DesignsCooling Management
This is (unfortunately) a very common design. The cooling management still features cooling of the column before the product takeoff. This condenses a portion of the vapour and sends it back down the column as reflux. It is controlled via the manipulation of cooling water to the reflux condenser. If water flow is reduced, the reflux ratio drops and output increases. If cooling water is increased, the reflux ratio is increased. It is possible to completely stop output by increasing water flow (total reflux). The CM designs has a lot of variations.
One good thing about CM is they achieve great tails compression. However, there are several implicit drawbacks to the CM, however. The most irritating is that to control the reflux ratio, you have to tweak the level of coolant flow to the reflux condenser. It is a very, very fiddly design to run. Coolant settings are not predictable, either - a hotter day could mean your water supply is warmer, or the still charge could be different. If you are recirculating your water, then it will get warmer, requiring constant attention. Heads compression is poor compared to other reflux designs. While these stills can make very palatable neutral, I have not heard reports of them performing as well as a VM or LM. I think this is not so much the stills fault, but more the difficulty of tuning them exactly with cooling flow. Regardless, reliable reports of CM stills achieving aezotrope purity are pretty few and far between.
I would strongly recommend avoiding these designs if you are building. The CM is generally regarded as an inferior design.
Commercially available cooling managment stills*:
Essencia Express, Still Spirits Reflux / Super Reflux, Spirits Unlimited Eurostill, All of Mile-Hi's designs (at time of writing), Brewhaus Essential Extractor series.
http://homedistiller.org/forum/viewtopi ... 46&t=13360
I will add this. I can achieve 95% with my CM. And it is a 2" X 32" column. So if I can do it. So can you.
So now we have that out of the way. Lets get to the modifications.
First one that should be done is to reroute the Coolant Flow. This will give you better control over the reflux ratio and product output. Basically you need to separate the two condensers. So the flow is not routed through one into the other. With the water flowing through the product condenser then into the reflux condenser. You get a temperature flux making it hard to adjust the flow. For the optimal reflux ratio and product output. By adding a simple manifold with two valves on it. One a ball valve for the product condenser. And the other a needle valve for the reflux condenser. The product condenser doesn’t need a fine adjustment. As long as you have adiquit flow to knock down all the vapors. It will work. A little extra wont hurt it. The reflux condenser however needs a fine control over the water flow. Using a needle valve gives you the fine control you need. Here is a simple diagram for a coolant water flow manifold. Based on what I use. You could make it as basic or as complicated as you like. Your choice. I use a 1/2" ball valve and a 1/4" needle valve on mine. a 3/8" needle valve will work also.
Now there are a few different designs out there as mentioned earlier. And hose routing is different between them. I have made a diagram for the two most used designs you can buy premade.
The first is a Mile High new style Jacketed column condenser. It has a jacketed area around the column that the water flows through. Cooling the outside of the column walls. Which is another problem I will cover later with another mod. Hose routing for this style should be as follows.
From the water tap or a recirculation pump to the input of the flow manifold.
From the ball valve on the manifold to Product condenser port A on diagram. Then out Product condenser port B to the drain or recirculation reservoir. If using a recirculation pump and reservoir.
From the needle valve to the Reflux condenser port C on the diagram. Then out Reflux condenser port D to the drain or recirculation reservoir.
The reason you want the coolant flowing from the bottom of the reflux condenser up and out the top is. You want it to be flooded at all times. If the flow was reversed it mite lead to a siphoning action pulling all the water out of the condenser. By it flowing up it has to fill it to the point of the outlet before it can leave. This maybe contradictory of the way it really should flow. But unless you can devise a system to make sure the condenser stays flooded at all times. The way I described it is the easiest and best way to do it. Especially for a new still operator.
The second is the older Through tube reflux condenser style. Mile High’s first version was this type. Along with the one Brehaus sells the Essential Extractor PSII. These styles can have two or more through tubes. I have seen one with six. Can’t remember who made it? But anyway the reflux condenser on this style is comprised of tubes that are routed through the column. So one end of the tube sticks out one sid of the column and the other end the other side of the column. Some the tubes are criss crossed. Some are inline. My diagram shows a four tube inline setup. For ease of making the diagram. This style the water flowing through the tubes causes the vapors to condense on the tubes. And fall back down the column. The drip is not really centered but can drip in the center. So this style will also benefit from the mod I will go over later. Here is how the water should be routed for this style.
From the water tap or a recirculation pump to the input of the flow manifold.
From the ball valve on the manifold to Product condenser port A on diagram. Then out Product condenser port B to the drain or recirculation reservoir. If using a recirculation pump and reservoir.
From the needle valve to the lowest most Reflux condenser tube in the column the. Out from the other side of that tube to the next higher tube. Out from the other side of that tube to the next higher tube. So on and so forth until you get to the upper most tube. Then out the last tube to the drain or recirculation reservoir.
And again for ease to keep the tubes full is why I described it this way. Although the tubes have been described as not having the same problems of not staying flooded. And yet others say they are worse.
Another modification to increase the efficiency of the reflux condensers. Add some copper mesh packing loosely within the reflux condenser area. This does two things.
One it causes turbulents in the vapors. Helping to keep them from bypassing the condenser.
Two the mesh makes contact with the cooling surface of the condenser. This creates more cooling surface. Making the mesh like a heatsink.
One of the problems with this design is the reflux forms on the walls of the column. Then runs back down the column walls bypassing the packing. This defeats the purpose of the packing. You want the reflux to fall back down the middle of the packing. So it can mingle with the rising hot vapors to be re vaporized. Thus creating the scrubbing action that the packing is there for. So on to the next modification.
Centering Ring
In order to get the reflux to mingle within the center of the packing. We need to get it there. So making a simple centering ring to redirect the reflux flow to the center of the packing. This can be done by making a simple funnel out of a sheet of copper. Or a flattened piece of copper pipe. You want the larger end to be just a touch bigger then the inside diameter of the column. So when you slide it into pace it will stay there. And fit snug so the falling reflux doesn’t bypass it. The smaller end will depend on the column diameter. Recommended sizes are.
For a two inch column 3/4" to 1”. One inch being the best. And not to go smaller then 3/4". Or it could choke the still out.
For a three inch column 1 1/4" to 1 1/2". Same reasons as above.
The centering ring can be made from whatever you want. I made mine from a 1 1/2" to 1” reducer. That I expanded or flared the 1 1/2" side out to fit snug in the column. I have included the placement of these centering rings in the diagrams. Placement may be different for each still. But you can move them to find the optimal location. You can also add more then one. Place them throughout the column if you like.
Another quick and easy mod is to just add a packed column extension. I know Mile High sells them. And I think Brewhaus does to. By adding 12" to the column length your purity will climb. And it will make hitting that magic number that much easier.
The last thing I would like to mention is the rubber plug used to cap off the top of the column. It also houses the thermometer. Replace it with something other then a synthetic material. A large natural cork plug will work. As long as it is not a composite cork made by gluing a bunch of little pieces together to make a big one. I’ve seen the use of a large cap made from wood. Just make sure the wood is safe to use. Not treated or a poisonous variety. A copper pipe cap can also be fitted to it. It doesn’t mater what it is made of as long as it is safe for use in hot high ABV vapors. And remember it needs to be sealed tight. You don’t want the alcohol vapors escaping.
Ok one more last thing. To extend your product output to reach your collection jar. Please use a safe material to do so. I would like to detour you from any synthetics. A piece of soft copper tube can be fitted over the end and clamped on. Then it can be bent to reach what ever you want it to. Or you can get a stainless tube and a compression fitting to extend it out. Just please stay away from the plastic hose that everyone seams to think they can use.
A note on running in pot still mode.
These are purely my observations. Take it as you will. I have found by leaving the packing in during pot still operation. No reflux condenser operation. I only get like maybe a 5% gain in ABV. Over removing the packing. And that's on a good run. So I feel its a waste of time pulling it out just for a pot still run. Others may disagree. Those are just my findings. Your mileage may vary.
Speaking of packing. These commercial available stills come with two kinds of packing copper mesh and Ceramic Raschig Rings. Again this is only an observation on my part. I have no proof on this one. Would like some feed back on it from those that do. But it is my understanding if both types are used in the same column. The two different types will hamper the columns ability to equalize with a proper temp gradient. Since the copper mesh and the Ceramic Raschig Rings handle heat differently. The gradual temp gradient from bottom to the top will be broken with the change from one packing to the other. I'm not going to say one is better then the other. What I am trying to say is it is better to stick with one kind of packing throughout the whole column. And a little copper in the vapor path will help remove sulfides created during fermentation.
This information was comprised of info I have gathered from many different threads around HD. And some real world experimenting with my own CM still. I would like to thank all those that helped me learn all of this. But that is so many. So I will say Thank you to HD.
And feel free to point out other things I mite have missed or forgotten. I would like to update it so it is a one stop shop. For those that need it. Forgive my crappy paint pics. Its all i have to work with.
Mods I placed it here in the novice section because. I thought it should be available to the new members. And they would come across it easier here. If you think we need to move it that's fine.