properties

The
essential components for supercritical fluid extraction setup include a an
extraction vessel,pump  separator and a
depressurization valve (Figure 1). The fluid source, preferably  a tank of carbon dioxide and syringe pump with
a pressure rating of at least 400 atmosphere are used. There is an exit valve
leading to a flow restrictor that depressurizes the fluid and transfers it into
a collection device. There is valve to control the flow of the critical fluid
into a heated extraction cell .At the start of 
the process  raw material is
placed in an extractor vessel, which has controller of  temperature and pressure controllers to
regulate these variables . The pretreated plant material with desirable  particle size and  moisture content  and  is
usually placed into a basket fitted with filters at both ends to with the aim
to  hold the solid material in place ,
allowing  the CO2  to  pass
through (Martinez et al., 2008). The
basket is afterwards placed into the extraction vessel. The lab scale units may
or may not be having baskets fitted 
which are aavailable commercially. Before sealing the extraction vessel
,the  basket is placed inside the
extraction vessel afterwards the system  at tank pressure is filled with CO2,while
the depressurization valve is closed, with the aim to prevent any  leakage in the system. For proper temperature
control ,the  thermocouple should be
put  inside the extraction as
thermocouples on the outside of the vessel are unable  to record the any  temperature variation  due to pressurization of CO2. Onces
there is   stabilization of the extractor pressure  and temperature the depressurization valve is
 opened to start the movement of SC-CO2
through the cell. As  the fluid and the
dissolved compounds are moved  to
separators, the products are collected via tap located in the lower part of the
separators. Therefore SC- CO2 extracts the components that can be
solubilized under the set of pressure and temperature conditions and moves them
out to the separation vessel. After depressurization, SC- CO2
becomes a gas, gets separated from the extract and subsequently  extract is collected in the separation vessel.
In addition, the valve ought to be heated to avoid freezing on depressurization
due to the well-known Joule–Thomson effect (Lemasson et al., 2016).afterwards the expanded CO2 goes through a
flow meter and a gas meter to assess the total volume of CO2 used throughout
 in an experiment. In general,
laboratory-scale units are do not  not
have setup  to recycle the CO2 so
the exhaust CO2 is vented. It is 
Obvious that this is non feasible in  the large-scale industrial plants
,concequently exhausted CO2 is collected in a tank and recycled back
to the extraction vessel. Finally, the fluid is regenerated and cycled or in
some cases  released to the environment
(Sihvonen et al., 1999).