It is obtained from the semi-dry whole grass of lemongrass by steam distillation.
Temperature is an important factor governing the penetration rate of citronella oil. Increasing the steam pressure and the steam temperature correspondingly can accelerate the distillation speed and shorten the distillation time. According to tests, a small steam distillation plant with a boiler volume of about 2.5 cubic meters and a steam pressure of up to about 3.5 to 4 kg / cm2, when the top pressure of the steamed mash is 1 kg / cm2, its oil yield is 1.3 kg / With a height of 0.06% per square centimeter and 0.05% higher aldehyde content, there is not much difference in distillation time. Therefore, it is necessary to proceed from the safety of production, and it is advisable to use a top pressure of 1 kg / cm2. Regardless of water distillation or steam distillation, the air pressure must be kept stable. The high or low air pressure will reduce the oil yield. Therefore, the distillate firepower on water must be kept fierce, but it must not be too small. For steam distillation, the inlet steam must be from small to large to make the steam pressure rise smoothly.
Amount of steam
During the distillation process of citronella, the citronella oil exposed on the leaf surface is taken away by water vapor. Therefore, during the distillation process, a certain amount of steam is required. Reasonable units of steam production can be determined by themselves. It is necessary to shorten the distillation time and increase the oil output rate, and also to use steam economically in order to improve the equipment utilization capacity and reduce fuel consumption.
That is, the high-temperature oil-water mixed steam becomes a low-temperature oil-water mixture through the cooling effect of the condenser tube. The condensed oil-water mixture should be at 30-35 ° C. If it is above 60 ° C, the oil content will partially evaporate, especially vanillin. The condensate pipe should be placed straight in the center of the ditch. The flow direction of the mixed liquid is opposite to the flow direction of the cooling water. At the same time, the condensate tube cannot be buried in the mud of the ditch. . The condensate from the condenser tube must enter the oil-water separator to separate citronella oil from water.
Production units using water distillation have accumulated rich experience in saving fuel. The quality of using citronella slag as a processing fuel has a great impact on shortening the distillation time and improving the oil yield. The citronella residue dried on the same day can shorten the distillation time by 20 to 30 minutes and increase the oil yield by 0.02 to 0.28%.
There are two main types of citronella oil used for spices: Javanese and Sri Lanka. The main components of both are citronellal, citronellol and geraniol, and the acetates of these two alcohols. Javanese species have relatively high aldehyde content and total alcohol content, so the planting volume is also large. China is currently a large country for the cultivation, export and consumption of Javan citronella oil. Indonesia and Vietnam also have large production, but not much consumption.