As mentioned in the section on the beer-stripper construction, it's important to use lead-free plumbing solder for constructing a still. Also, remember to use Teflon tape on all threaded connections to ensure a watertight seal. Simply wrap the Teflon tape around the male threads two or three times before inserting the connector into the female fitting.
As shown in Figure 5, the apparatus consists of a boiler with a 114 cm (45") reflux column made from H" copper pipe. At the top of the column is the still head where the vapours rising from the boiler are condensed and split into two streams. The major stream flows back down the column while the remaining stream flows into the receiver. Let's look at each part of the still in more detail.
The Boiler: Just as we did for the beer-stripper we use a domestic electric hot water heater for the boiler but in this case it is quite a bit smaller in size. A 45L (12 US gallon) size, very common for cottages or small apartments, is ideal and is usually heated by a single 1500W, 120 V immersion element.
The thermostat will have to be bypassed. Remove the thermostat access panel and bypass it just as is done in the case of the beer stripper. See Figure 4.
The packed 1W column has only a limited capacity to allow vapours to rise up through the packing against the downward flow of condensed liquid (see the section on the Principles of Fractional Distillation in the chapter on Distillation) so the boil-up rate must not be too great or the column will choke. The 1500W heater supplied is, in fact, unnecessarily large so the power output must be reduced.
A simple and cheap way to do this is to substitute a 750W heater for the 1500W one supplied. However, 750W elements are hard, if not impossible, to find nowadays, so an excellent way to accomplish this same end is to purchase a 3000W, 240V heater and run it on 120V. The current is cut in half, as is the voltage, so the wattage is reduced to one-quarter (i.e. 3000 x H = 750W). A bonus with this arrangement is that the current density in the heater will be so much below its rated capacity that it should have a very extended life.
There will be a hole at the top or side of the sheet-metal cover of the hot-water tank where the wires to the 120 V immersion element come out. Connect the wires to a 120 V three-prong plug. The two wires to the 120 V immersion heater will be black and white, and there will be a green or bare ground wire. The three-prong plug has a round-shaped ground prong and two blade-shaped power prongs. One blade-shaped prong is wider than the other. Connect the white wire to the widest blade-shaped prong, and the black wire to the other blade-shaped prong. Connect the green or bare ground wire to the round-shaped prong. The wires are then secured to the sheet-metal cover using a 90o electrical box connector.
Use a heavy-duty extension cord to plug the still into a standard 120 V wall socket. A grounded electrical timer can be used at the wall socket to turn the still on (or off) at a prescribed time.
A still with 20L or so of mash will take about 3^ hours to boil (and about 5^ hours with 40L). It's useful to have the still switch on automatically at, say 4 o'clock in the morning, and come to boil at 7:30. By 8:00 it will be equilibrating and ready to run off. This eliminates having to wait 3^ to 4 hours for boil-up and equilibration before beginning the run.
Of course, it's important to note that the heat-exchanger water will have to be running before boil-up, or the alcohol and congeners will not be condensed and therefore lost to the air. One way to mitigate this is to set the timer to shut off 15 minutes or so before it's expected to come to boil. The operator then attends to the still 20 or 30 minutes prior to expected boil-up and turns on the heat-exchanger water and disables the timer shutoff.
Another way is to simply turn the heat-exchanger water on at setup time and let it run all night. It is just a slow trickle. Perhaps you're not concerned about such a small loss.
A more creative way to address turning on the heat-exchanger water is to employ a 120V water solenoid. The water solenoid would be placed on the water supply tube to the heat exchanger and plugged into the same extension cord as the still. This way the heat-exchanger water would start running at the same time as the timer switched the still on.
A further refinement would be to attach a thermostor to the stillhead and set the thermostor to activate the water solenoid when the temperature of the stillhead exceeded a certain value. This way the heat-exchanger water wouldn't start running until the still actually began boiling
To the two side connectors of the boiler (/" male-threaded plumbing connectors) attach /" ball valves. Fit the ball valves with female garden-hose couplings.
Remove the sheet-metal cover from the top of the tank. This is where the magnesium rod (i.e. the anode) used as an anticorrosion device is installed. Remove it since it is not needed in our application and we need the 3 " female connector for the installation of the reflux column.
The anode is usually torqued in very tightly, so the best way to remove it is to place a socket wrench (often 1 1/8") on the anode fitting and use a 1M (3') length of pipe to extend the socket drive. Secure the water heater firmly and use the pipe and socket wrench to turn the fitting in a counter-clockwise direction to loosen it. Once loosened, it will remove easily.
Somewhere on the side of the tank is a /" female pipe connector where a pressure-release valve would normally be installed. For our purposes we will not be installing a pressure-release valve, so this connector will need to be plugged. Take the anode removed from the top fitting and unscrew the magnesium rod from the 3 " male plug fitting and discard the magnesium rod. The male plug fitting can then be used to plug the pressure-release valve connector.
To attach the column to the boiler, as shown in Figure 6, a series of adapters will be needed to go from the /" female pipe thread in the top of the boiler where the anode was, to the W copper pipe used for the reflux column. Connect a /" copper or brass male adapter (/" male thread to /" female sweat) to the female pipe thread in the top of the tank.
Next, solder a 5 cm (2") piece of /" copper pipe to the sweat fitting of the adapter. Onto the piece of copper pipe, solder a /" x 1W copper coupling. Onto the copper coupling solder a 5 cm (2") piece of 1W copper pipe. Onto the piece of copper pipe solder the flare-and-nut end of a W copper union.
Solder a 114 cm (45") piece of 1W copper pipe into the male-thread end of the W copper union. The 114-cm (45") piece of W copper pipe (the reflux column) can now be connected to and disconnected from the boiler by means of the union.
It's useful to use some Teflon tape at the interface of the union to ensure a good watertight seal.
A 1W copper union is used in this set of adapters instead of a union as used in the beer stripper. This is to allow access to the packing in the 114-cm (45") reflux column.
The Reflux Column: The fractionating column, or reflux column, consists of 114 cm (45") of W I.D. copper pipe. The bottom end of the column is joined to the top of the boiler by means of a union to permit disassembly when required.
At the top of the column a tee is provided for the passage of vapour across to the stillhead condenser and for a thermometer to measure the vapour temperature.
The column must be well insulated to ensure a stable temperature regime within the column while it is refluxing. Use a 1 3/8" I.D. x wall closed-cell foam insulating sleeve, such as
Armiflex®, as used in refrigeration and air conditioning systems. Cut it to length and secure it in place with 3" hose clamps at the top and bottom to prevent air from circulating between the insulation and the column.
The Stillhead: See Figure 7. The purpose of the stillhead is to condense the vapours emerging from the column into a liquid and divide the liquid into two streams. It condenses the vapour back to a liquid in the heat exchanger and, as the liquid runs back down towards the column, diverts a portion of it to the outside via a needle valve.
The stillhead is fabricated by soldering an 18 cm (7") piece of 1W pipe into the 1W tee at the top of the column to form the horizontal part of the stillhead. A valuable refinement is to have a tongue protruding into the middle of the column, as shown in Figure 7, to ensure the returning liquid cascades down the centre of the column.
To the horizontal part of the stillhead, solder a 1W copper elbow facing upward parallel to the column. To the other end of the elbow solder a 30 cm (12") piece of 1W copper pipe.
Solder a short length of 3/8" copper tubing, say 2 cm (3/4"), into a 3/8" hole drilled in the 1W copper elbow as shown in Figure 7. Attach a 3/8" needle valve with a compression fitting. This will avoid the necessity of having to heat the valve itself during soldering.
The hole for the 3/8" tube should be drilled in the elbow at a place where it will pass through both the elbow and the copper pipe. This will give the 3/8" tube a better purchase in the stillhead. Make sure the 3/8" tube is not inserted into the hole too far so as to dam up the condensed liquid and prevent the flow to the needle valve.
Insert another short piece of 3/8" tube in the output of the needle valve as shown in Figure 7. This is also connected using a compression fitting.
The condenser (heat exchanger) for cooling the vapour and returning it to the column is made from about 5M (16') of 3/16" copper tubing wound around a piece of %" pipe. It's best to start out with 7.6M (25') of tubing and wind the coils tight together until the condenser is 28 cm (11") or so long. Leave 30-60 cm (1 or 2') of tubing at each end to attach the cold-water supply and drain tubes.
The top of the stillhead must be open to the air. A still has to be a completely open system with no build-up of pressure. The heat exchanger is inserted loosely into the top of the stillhead, suspended by its input and output tubes as shown in Figure 7.
As for supplying cold water to the heat exchanger, a standard forced-air furnace humidifier tap-valve kit can be used, the same as for the beer stripper.
The cold water should be input at the opposite end of the coil to where the hot vapours approach the coil. So in the case of the spirit still, the cold water should enter the tube that leads to the end of the coil closest to the top of the stillhead, and exhausted at the bottom of the coil.
Heat exchangers of this design are remarkably efficient, and require a surprisingly slow trickle of cold water to thoroughly condense the vapours. When the still is boiling and in full operation the output water should not feel hotter than luke warm to the touch. If it's hotter, then the flow of cold water needs to be turned up slightly.
A thermometer in the stillhead measures the temperature of the vapour at the top of the column and is an excellent indicator of just when reflux has started. It's also useful to help indicate when the foreshots are finished, when the tails are starting to appear, and when the tails are complete. However, determining the different phase transitions is much more subjective than simply taking a thermometer reading. This will be explained in detail in the chapter on Distillation.
For mounting the thermometer in the stillhead, solder a 7 cm (2%") piece of W copper pipe into the top of the W tee. You can either drill a hole in a W cork and insert the thermometer in the cork and place the cork in the top of the column, or you can use a shorter piece of 1W pipe and solder a 1W x %" coupling to it. This allows you to use a %" cork which is not only much cheaper than a 1W cork, but you can use a standard wine-bottle cork. A used wine-bottle cork with a fairly straight, fairly centred corkscrew hole will work just fine. The bulb of the thermometer should be positioned right at the branch where the horizontal pipe connects to the tee.
A way to mount the thermometer in the top of the stillhead that avoids having to use corks altogether, is to drill a 3/8" hole in the middle of a 1W" copper cap, and solder a 2.5 cm (1") piece of 3/8" copper tubing into the hole. The tubing should protrude into the hole about V cm (3/16"). See Figure 8.
Next, take a 3/8" x W" compression coupling and remove both compression nuts and both ferrules. Place the coupling in a vice with the W" end up. Looking through the coupling it
will be evident that the passage is too narrow for the thermometer to pass through it. Drill out the passage with a 17/64" drill bit. Try the thermometer in the passage. If it's still too narrow, either drill it out with a slightly larger drill bit or ream it out until it fits. A slightly loose fit is no problem. The W" compression nut will need drilling out with a 17/64" bit as well.
Place the 3/8" compression nut and ferrule around the piece of 3/8" tubing that's soldered into the 1W" cap and tighten the compression coupling into place. Next, solder the 1W" cap onto the piece of 1W" pipe on top of the tee.
Gauge the position of the thermometer bulb so it extends to the branch of the tee, but stays well above the tongue. It's important that the thermometer does not come into contact with the condensed liquid or the temperature reading will be incorrect.
To install the thermometer in the W" end of the compression coupling, discard the W" ferrule and wrap 10-15 layers of Teflon tape around the shaft of the thermometer where it meets the compression coupling. Use enough Teflon tape so that the thermometer fits snuggly into the W" compression nut. And finally, tighten the W" compression nut to secure the thermometer in place.
The overall height of the spirit still will be about 2.16M (7'1"-7'2") given that the 45L (12 US gallon) hot water heater is 56 cm (22") high. If height is at a premium, it helps to minimize the length of the copper tubes used as connectors for the plumbing adapters (see Figure 6) from the boiler to the column. Also, the 114-cm (45") column could be made a few centimeters shorter if required.
Packing: The packing inside a fractionating column is very important, and many articles in the scientific literature have been devoted to the subject. What is needed are pieces of glass, ceramic, or metal which are inert to the liquid being refluxed and which have the following characteristics: they should not pack tightly, but should be of such a shape that they leave plenty of free space for vapour to rise up against a descending flow of liquid; and they should have a large surface area and crevices where liquid can be trapped.
An excellent and cheap packing is copper or stainless steel scouring pads as used in the kitchen for cleaning pots and pans. Copper ones are by far more common and typically come in packages of two. Generally, you will need about 16 of the size sold in most supermarkets (i.e. 8 packages of 2). To install them in the reflux column, remove the rubber band that holds them together and gently push them up the column from the bottom. Pack them firmly but avoid causing tight compaction. The packing should go up the column as far as where the tongue from the horizontal section of the stillhead enters the column at the tee. The tongue also serves as a convenient stop for the scouring pads as they are being packed in the column.
Once the spirit still is set up and ready to operate, you will need a way to mount a receiver under the output of the needle valve. One very good way to do this is to stand the still up against a wall (typically in the basement) with the horizontal section of the stillhead parallel to the wall. Mount an adjustable shelf on the wall behind the still, and adjust the shelf so as to place a receiver about 3 or 4 cm (1^-2") below the output from the needle valve.
Filling and Draining the Spirit Still: The upper and lower ball valves on the boiler are used in conjunction with the transfer hoses described above. Typically, the upper ball valve is used to siphon the mash, or low wines (i.e. output from the beer stripper), into the spirit still, and the lower one is used to drain it.
To fill the spirit still, the container with the strained mash, or the low wines if a beer stripper was employed, is placed at a level higher than the boiler. The filler-hose is connected to the upper ball valve of the boiler and the siphon starter is placed in the mash container. The operator then opens the upper ball valve and, ensuring the bottom one is closed, operates the siphon starter to initiate the siphon from the mash container to the boiler. When the transfer is complete, the upper ball valve is closed and the filler-hose is removed from the boiler.
It's important to note that if you are transferring low wines (40% or more alc/vol) the siphon starter must be made of alcohol resistant material. Acrylic is a common material for siphon starters these days, and is not alcohol resistant and must not be used with low wines. Acrylic will dissolve in alcohol and will contaminate the alcohol rendering it nonpotable. This, of course, is not a problem when transferring an 8-10% alc/vol corn mash.
After the distillation is complete, the still can be drained by attaching the drain-hose to the lower ball valve. Lead the drain-hose to a drain and open the lower ball valve.
After the still has been drained, it can be flushed out by connecting the flushing-hose to the top ball valve and a faucet. With the bottom ball valve still connected to the drain-hose, and both valves wide open, the operator can flush water from the faucet through the boiler to rinse it out.
The upper side connector where the upper ball valve is connected is a %" pipe that leads into the centre of the hot-water heater and bends upward and leads to within a cm (^") or so from the very top of the tank. This is because, as a hot-water heater, the hot water must be drawn off the very top of the tank. In this application it serves very well to create a fountain effect inside the boiler when you are flushing it out.
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