Vacuum distillation is one of the distillation methods under reduced pressure. It is generally used to separate substances that are easily decomposed or polymerized when heated to boiling under atmospheric pressure or to combine with other distillation methods such as steam distillation to lower the distillation temperature. Commonly used in chemical, petroleum and other industries.
This article mainly introduces the vacuum distillation system in the application from CNSL to cardanol designed by our company.
Cardanol is widely used in coatings, friction materials, composites and macro-molecule additives. It is a water-insoluble, renewable resource that is soluble in organic solvents such as ethanol and ether. It is produced by vacuum distillation of CNSL, which is a brown, viscous liquid that is toxic, irritant and corrosive and is extracted from the cashew nut shell.
Normally, CNSL has 90% cardanol.
The real extraction rate from CNSL to cardanol is normally from 44% -88%, the factors that influence this rate are mianly: vacuum, time, temperature. Therefore, the vacuum system is especially important in order to increase the conversion rate.
In the choice of vacuum system, according to our experience, our peers’ experience and customers’ feedback, Roots water ring unit is the most suitable choice.
Roots-liquid ring vacuum solution
CNSL to Cardanol (for reference)
Firstly the inlet air temperature of the water ring pump can not be higher than 60 degrees Celsius and the actual temperature of the air intake is usually higher than 60 degrees Celsius. So we need to equip the front condensation to reduce the temperature of the air and also transfer some gas into liquid. Condensers are mainly divided into tube heat exchanger and plate heat exchanger. For more information, please consult EVP.
The specific selection of water ring pump and Roots pump need to refer to the specific requirements of customers: the required degree of vacuum, pumping volume, etc., Usually we recommend a single-stage water ring pump with three Roots pumps, coupled with water circulation system, constitute a four-stage Roots-water ring unit which can better improve the conversion rate of cardanol. Of course, for financial reasons, some customers will also choose a two-stage water ring pump with two roots pump unit, but the effect is not as good as the first solution.
The role of the buffer tank between the water ring pump and the Roots pump is to prevent the working fluid in the water ring pump from returning to the Roots pump during the working process. Because of the high requirements of the unit, gas volume and vacuum, we need to supply water Ring pump is equipped with steam separator (specific selection, please consult EVP) to replace the intake and exhaust side box.
In addition, the selection of the motor we use explosion-proof models to ensure safety, usually using DIIBT4, IP54 motor. Of course, according to customers’ requirements, we can supply different types of explosion-proof motor. WEG, ABB, SIEMENS are all our long-term partners.
EVP vacuum, our professional team will customize the most suitable vacuum system for you, providing one-stop service, please feel free to consult any questions related to the vacuum system.
Edited by: Emily Fu (Shanghai EVP Vacuum Technology Co., Ltd.)