The formula to calculate the run time of a still stripping 5 gallons (18.9 L) of 10% ABV wash with a 1500W element is:
Run time = (Total Energy Required ÷ Power Input) ÷ 60
Total Energy Required = mass of wash (in grams) x specific heat capacity of wash (in J/g·°C) x temperature change (in °C)
For this example, assuming the specific heat capacity of the wash is approximately 4.18 J/g·°C (similar to that of water), and that the wash is heated from room temperature (20°C) to boiling point of the wash (approximately 78.37°C for a 10% ABV solution):
- Calculate the mass of the wash in grams: 5 gallons x 3.785 L/gallon x 1000 g/L = 18925 g
- Calculate the total energy required to heat the wash to boiling: Total Energy Required = 18925 g x 4.18 J/g·°C x (78.37°C – 20°C) = 5,500,704 J
- Calculate the run time: Run time = (5,500,704 J ÷ 1500 W) ÷ 60 = 6.11 hours
Note that this is just an estimate and the actual run time may vary depending on factors such as the efficiency of the still and the specific heat capacity of the wash.
To calculate the total run time of a 100L still running at 4kW, performing a reflux run with a 2:1 reflux ratio, and filled with low wines that are 40% ethanol and 60% water, with a take-off rate of 4L/hr, we can use the following formula:
Total run time = Total volume of liquid in still ÷ (Take-off rate + Reflux rate)
First, let’s calculate the total volume of liquid in the still:
100L x 0.4 (ethanol) = 40L of ethanol 100L x 0.6 (water) = 60L of water Total volume of liquid = 40L + 60L = 100L
Next, let’s calculate the reflux rate:
Reflux rate = Take-off rate x Reflux ratio
Reflux ratio = 2:1 Take-off rate = 4L/hr
Reflux rate = 4L/hr x 2 = 8L/hr
Now we can plug in the values into the formula:
Total run time = 100L ÷ (4L/hr + 8L/hr) = 100L ÷ 12L/hr = 8.33 hours
Here’s a worked example for calculating the total run time of a 200L still running at 6kW that is performing a stripping run of 12% ABV sugar wash:
- Determine the amount of alcohol in the wash. In this case, we have a 12% ABV sugar wash, which means that 12% of the liquid is ethanol.ethanol mass = total mass x ABV = 200 L x 1 kg/L x 0.12 = 24 kg
- Calculate the energy required to vaporize all of the ethanol in the wash. The heat of vaporization of ethanol is approximately 841 kJ/kg.energy = ethanol mass x heat of vaporization = 24 kg x 841,000 J/kg = 20,184,000 J
- Determine the distillation rate of the still. This depends on a variety of factors, such as the size and design of the still, the temperature and pressure of the wash, and the efficiency of the condenser. For the purposes of this example, let’s assume a distillation rate of 1 L per minute.
- Calculate the total run time using the formula:time = energy / (power x distillation rate)where power is the power input of the still in watts, which in this case is 6,000 W.time = 20,184,000 J / (6,000 W x 60 s/L) = 562 minutesThis is equivalent to approximately 9 hours and 22 minutes.
So in this example, it would take approximately 9 hours and 22 minutes to strip a 12% ABV sugar wash in a 200L still running at 6kW with a distillation rate of 1 L per minute. Note that this is just an estimate and the actual run time may vary depending on the specific conditions and variables involved in the distillation process.