The definition of an essential oil, which was adopted by the International Standards Organization (ISO) at the 9th Plenary Meeting of the Technical Committee ISO/TC54 Essential Oils, held in Lisbon, 5th-9th March, 1968, was:

Essential oils are volatile oils, generally odorous, which occur in certain plants or specified parts of plants, recovered by accepted procedures such that the nature and composition of the product is, as nearly as practicable, unchanged by such procedures.

"This is an important definition. It specifies clearly that the nature and composition of the oil must be unchanged by the process of extracting it and is therefore one reason why steam distillation is an appropriate method of extraction. Furthermore, because steam distillation has been the extraction method for most essential oils, the market accepts steam distilled oil as normal oil.
Oil derived by another technique might be of slightly different chemical composition and therefore might not be accepted by the market."
- Department of Trade and Industry Document South Africa Dec 2004

Components of a Distillation Unit

Essential Oils Distillation Process

1. Steam Generator or Boiler

The boiler or steam generator supplies the steam for the system and each plant material has its own steam flow rate.
The fuel source can vary due to customers various circumstances and preferences.

Over the years we have built up relationships with suppliers and can supply boilers for you at competitive rates or use an existing steam source.

Please note boilers fall under government laws as they are pressurised vessels and have to be inspected on a continuous basis. They are normally the only thing that can go wrong with our machines and this is why we normally work with your countries suppliers and adhere to your rules and regulations that these pressure vessels fall under.
Should a problem occur with the boiler your supplier is close at hand.
Please see your government gazette for these laws.

Electric Boiler

Electric Boiler Distilling Essential Oils

Classed as a steam generator, if it is set to operate at atmospheric pressure, it therefore does not fall under governing laws as conventional boilers do.
We also supply pressurised electrical boilers and they are classed as boilers. They need to be inspected regularly by an inspector in your country.
They all require a specific water type
These electrical boilers are easy to clean and service.

Diesel or LP Gas

LP Gas Boiler for Distilling Essential Oils

Diesel or gas boilers fall under the laws and need to be inspected by government officials.
They normally need to pass an inspection when installed.
They are harder to clean and to do maintenance on.
They cannot handle certain water types

Wood/Coal or Bio Mass

Wood burning distillation boiler for essential oil extraction

These can be hand fed or have an automatic feed, depending on the size. 
The heat supply for steam may vary depending on the rate of wood being fed.
Need to be cleaned regularly.
These boilers do not all require inspections (depending on the size and type – low pressure/high pressure).

2. Heat Exchanger

The heat exchanger turns steam and the volatile oil vapour back into liquid. Designed according to the machine's steam flow rate, plant material oil properties and water quality.

3. Separator

The Separator separates the oil and hydrosol. Designed for the machine's flow rate and oil properties of plant material used. 
Separators are available for oils lighter and/or heavier than water.

Distillation Heat Exchanger and Separator

4. Still

The size of the still is determined by the field capacity and plant material. E.g. lavender has a window period and all material has to be harvested and processed in a short time, which increases machine size and boiler steam flow rate required independently from the field size (as to other plants in the same field capacity).

Essential Oils Pot Still submerged installation
Stainless steel essential oils pot still manufactured by EDE from Riebeek Kasteel South Africa
Large stainless steel pot stills for essential oil distillation

Optional Extras (not always so optional)

5. Gantry or Lifting Equipment

Lifting gantries for distilling essential oil plants

To make matters easier we design gantries and lifting solutions for you to increase production and effectively process biomass.

6. Coolers

Air Cooler for Distillation

If there is not an abundance of cool water available, water can be recirculated using either an evaporative cooling tower or a dry cooler (will be subject to the location climate and required cooling capacity)

Dry cooler
Requires a pump and a storage tank for water. The piping is usually completed on machines so you can plug and play. Very efficient in terms of water usage, loses minimal amounts of cooling water.

Evaporative cooling tower
Usually more feasible when the wet bulb temperature is relatively lower. Also requires a circulation pump, but contains its own reservoir within the tower. These units are only available for larger units. Some water loss due to evaporative action.