Distillation, during the production of spirits, is the process that comes after the mash has been prepared and fermented. Distillation is based on the different boiling points of alcohol at 173.3 °F (78.5 °C) and water at 212 °F (100 °C). During distillation, heat is applied on the still. Liquids with boiling points above 173.3 °F (78.5 °C) will vaporize first since they have a lower boiling point. Their condensate will have higher alcohol by volume (ABV).
Heating the still
- Electric element. Electric stills might be expensive but they are cheaper and convenient to run. Secondly, they will give you the best control over temperature compared to other heat sources and are relatively safe since there will be no open fires.
- Propane. Propane is a form of direct heat which is also convenient to use. It is easy to set-up and propane gas is readily available although sometimes considered expensive. While you should be able to heat your alcohol within a short time, controlling the boiler’s temperature afterward can be challenging.
- Wood. wood is the cheapest option. However, you may have to hassle lighting it and maintaining constant heat. Controlling the heat means adding or removing wood from the fire and will definitely require some expert skill to get your fire to the right temperature. Secondly, wood is not a clean fuel.
Why does an electric still need a digital controller?
As we have already seen, temperature control is critical to running any still. Application of heat on the still has two effects, boiling the liquids to bring them up to their specific boiling points and increasing the boiling speed to vaporizing alcohol after it attains the boiling point.
Electronic controllers are installed on stills to automate the distilling process and make it more manageable, ideally having steady heat throughout the distillation process rather than instances of on and off cycles. A good controller should be able to keep the cycle times low at 1 cycle per second or perhaps none at all in a perfect situation.
To do this, one will need:
- Stainless steel or copper still
- Electric heating element
A temperature controller is a device used to control the temperature in a still. The controller is connected to a heating element. It will first take the temperature from a sensor and compare it to the set or required temperature to get the variance. It then triggers the heating element to either bring up or cool down the temperature to achieve the desired temperature.
Types of controllers
1. The on/off controller
This is the most basic type of controller. This controller operates as a switch. When the temperature goes below the desired, it turns on the heating element. When the temperature rises above the desired, it turns off the heating elements. However, where switching between on and off happens rapidly, the valves of these controllers are bound to get damaged. Usually, a hysteresis will be installed on the set-up to prevent the controllers from making fast switches.
2. Proportional controllers
In the on/off controllers, we saw that one disadvantage is the rapid cycling or switching between the on and off modes. Proportional controllers are designed to overcome this disadvantage. In a proportional controller, the output signal is usually equal to the variance signal. In other words, the output signal triggers the heating element to adjust the boiler temperature by either slowing down or raising it around the variance point to the desired point and then keeps it at this constant. Beyond the variance proportion, it will turn the element on or off as in the on/off controller.
Hence proportional controllers are best suited in situations where
- The variance between the desired and the actual boiler temperature is small
- The variance comes about gradually
3. PID Controllers
PID stands for proportional with integral and derivative control. These controllers automatically apply the most accurate and responsive correction to a temperature variance in the still. PID controllers are best suited where continuous tuning, in relation to the variance obtained, is required. It operates by continuously calculating boiler temperature variance and then continuously signaling the heating element for more responsive correction and with close to zero delay.
Using a PID controller on your still
As we had seen earlier, a complete set-up requires a still, a heating element, a controller, and an adaptor.
- Install your heating element on to the still.
- Around where the thermometer is placed on the still, install a thermowell. The function of the thermowell is to protect the temperature sensor.
- Now take your temperature sensor and install it onto the thermowell by sliding it into position.
- Fill the still and turn on the heating element.
- Allow the still to heat to maximum power until it starts producing the distillate.
Correcting the variance in temperature depends on a number of factors including the size of the heating element, the surrounding temperature, as well as the amount of insulation on the oven.
Opting for an electric heating element together with an electronic controller offers you the advantage of a fully automated still. You are more in control of the distillation process yet still you can run it without the hassle of having to stick around to supervise it closely because the controller takes up this function. With temperature and power controls taken care of, you have time to focus on what’s most important, producing flavorful spirits.