Solid-liquid extraction, using microwaves as an energy source.
In very dry material, some microwave absorbing agent should be introduced into the biomass.
Properties of a substance which determine its response to an electromagnetic field.
Compounds subject of degradation under prolonged thermal exposing.
Microwaves heat mostly the extractant, which diffuses into the plant material.
In mono-mode microwave equipment the design of the resonant (extraction) unit allows the formation of only one ”standing wave” - the key for a uniform energy distribution inside the flowing medium.
Multi-mode microwave resonant (extraction) unit allows the formation of more then one ”standing wave”.
(also called microwave-assisted extraction) is an efficient method which involves deriving natural compounds from raw plants or seaweed biomass.
What differentiates this novel method from the conventional routines is the mechanism of the extraction process.
In conventional methods the heated extraction agent (extractant) diffuses into the plant material from the outside, while microwaves directly heat the target component inside the plant cells
, swelling them as their walls burst under the internal pressure and constituents are released out to the surrounding medium.
Microwave extraction allows organic compounds to be derived from the biomass more rapidly, with similar or better yield as compared to conventional extraction methods:
Microwave Extraction also offers better selectivity, less extractant use, and lower energy input.
Under microwave conditions, the extracting agents are chosen except for their compatibility to the compounds of interest also according to their dielectric properties
for the required temperature range and electromagnetic radiation frequency.
Low or non-absorptive (transparent) to microwave energy extractants are used for maximizing the effect of microwave extracting mechanism and less energy consumption.
Also, the surrounding medium remains relatively cool, which allows rapid extraction of thermally labile natural compounds
If microwaves' high-absorptive extraction agent is used, then the process is similar to the conventional extraction methods
, but even so the process takes less time, because of the instant volumetric heating of the medium.
Sometimes, mixtures of high and low microwave's absorbing agents were found to produce optimum results.
The Microwave Extractor (ME) is mono-mode microwave equipment
- the same used in Microwave Chemical Processing
and Microwave pretreatment
Its principal structure is presented on Figure 4.
Figure 4. shows only one microwave extraction unit, but most likely the Microwave Extractor to have two or more units for optimizing the extraction process.
The equipment structure shown is presented in it's most basic form.
The actual configuration design of the Microwave Extractor and the peripherals depends on the specific requirements defined as a process steps with their interconnections on the flowsheet.
The Microwave Extractor and it's peripherals could be designed as a multi-purpose extraction equipment. It basically means that it could perform different types of solid-liquid extraction with optimized mass and energy balance through automated change-over in the system setup (programmed readjusting of the microwave power, reagent's flow rate, switching the streams' path over the pipe network between the extraction units, etc.)
Numbering up the Microwave Extractor's units connected in parallel makes the maximum end-product throughoutput virtually unlimited.
This approach greatly simplifies the final industrial plant lay-out, providing solutions for small and large scale production processes.
The Microwave Extractor allows for easy integration with existing continuous processing lines from previous conventional solid-liquid extraction process.