In many chemical, pharmaceutical, botanical and food processes, extracting valuable components from solid raw materials is a core operation.
The performance of this step directly affects yield, quality and overall production cost. Among the various types of solid liquid extraction apparatus, agitated extraction tanks are one of the most versatile and widely used solutions.
Nanjing Hjchem Equipment Co.,Ltd specializes in the design and manufacture of agitated extraction tanks tailored specifically for solid liquid extraction.
From laboratory research systems to pilot plants and large industrial lines, we provide customized equipment that helps customers achieve stable, efficient and scalable extraction processes.
What Is Solid Liquid Extraction?
1. Definition and Role in Process Industries
Solid liquid extraction (also called leaching) is a separation process in which a soluble component (solute) is removed from a solid matrix using a liquid solvent. The solute dissolves into the solvent, forming a liquid extract, while the remaining solid becomes the raffinate.
Typical applications include:
Extracting active ingredients from herbal and plant materials with water or ethanol
Leaching APIs or intermediates from filter cakes in pharmaceutical production
Removing impurities or residual monomers from polymer pellets or resins
Extracting flavors, colors, and antioxidants from food raw materials
Leaching metals or salts from catalysts, ores or inorganic solids
In all these cases, an efficient solid liquid extraction step is essential to maximize recovery, control impurities and reduce solvent consumption.
2. Principle of Solid Liquid Extraction
The principle of solid liquid extraction is based on mass transfer and diffusion:
The liquid solvent wets and penetrates into the pores of the solid particles.
The solute dissolves into the solvent at the solid–liquid interface.
The dissolved solute diffuses from inside the solid particle into the bulk liquid.
The concentration gradient between the solid interior and the surrounding liquid drives continued mass transfer until equilibrium is approached.
The rate and efficiency of this process depend on:
Particle size and structure of the solid
Solvent type, polarity, viscosity and temperature
Agitation and mixing intensity
Solid–liquid ratio and contact time
An effective solid liquid extraction apparatus must therefore provide intimate contact between solids and solvent, maintain uniform temperature, and promote strong but controlled mixing. This is exactly where agitated extraction tanks excel.
What Are Agitated Extraction Tanks?
1. Basic Concept
An agitated extraction tank is a vessel designed specifically to perform solid liquid extraction with mechanical agitation. In its simplest form, it consists of:
A cylindrical or vertical tank with top charging and bottom discharge
A mechanical agitator (anchor, paddle, propeller, turbine, or combination)
Heating/cooling jacket or coils for temperature control
Ports for solvent addition, sampling and pressure relief
Instruments for temperature, level and sometimes pressure monitoring
During operation, solids and solvent are charged into the tank, the agitator is started, the mixture is held at the desired temperature for a specified extraction time, and then the extract is discharged for solid–liquid separation.
2. Why Agitation Matters
Agitation is the key feature that distinguishes agitated extraction tanks from static percolation columns or simple soaking vessels:
Enhanced mass transfer: Agitation refreshes the liquid at the solid surface, maintaining a strong concentration gradient.
Uniform temperature: Mixing prevents hot or cold spots, ensuring consistent extraction conditions throughout the tank.
Reduced extraction time: Better mass transfer means the target yield can be reached faster.
Improved handling of complex solids: Swelling, fibrous or cohesive materials that are difficult to percolate can often be processed efficiently in an agitated tank.
For many modern plants that handle diverse raw materials and multiple products, agitated extraction tanks provide the flexibility and performance needed for both routine operations and new product development.
Main Components of Agitated Extraction Tanks
Design Features of Nanjing Hjchem Agitated Extraction Tanks
1. Materials and Construction
To meet the requirements of different industries, our agitated extraction tanks are typically built in:
SS304 or SS316L stainless steel for contact parts
Optional higher-alloy materials for corrosive solvents or aggressive media
Sanitary finishes and hygienic design for pharmaceutical and food applications
The tank geometry, nozzles and internal structures are carefully designed to:
Promote efficient mixing and drainage
Minimize dead zones and product retention
Facilitate cleaning and inspection
2. Agitation and Mixing Options
We select and design agitators based on your specific process:
Anchor or paddle agitators for high-viscosity slurries and fragile solids
Propeller or turbine agitators for low-to-medium viscosity and intensive mixing
Combined multi-level agitators for tall tanks and high solid loadings
The agitation system is engineered to provide sufficient power input for effective mass transfer, while avoiding excessive shear that might damage sensitive particles or generate unwanted fines.
3. Temperature and Process Control
Because temperature significantly affects solubility and diffusion, Nanjing Hjchem provides:
Jacketed tanks and/or internal coils for heating and cooling
PID-based temperature control loops for stable operation
Optional vacuum operation for low-temperature extraction of heat-sensitive materials
In addition, our agitated extraction tanks can be equipped with:
Level, temperature and pressure instruments
Sampling ports and sight glasses
PLC/HMI-based control panels for automated operation, recipe management and data logging
Frequently Asked Questions (FAQ)
1.What is an agitated extraction tank?
An agitated extraction tank is a solid liquid extraction apparatus that uses mechanical agitation to mix solid raw materials with a solvent. It promotes mass transfer, ensuring that soluble components are efficiently leached from the solids into the liquid phase under controlled temperature and time.
2.What kinds of materials can be processed?
Agitated extraction tanks can handle a wide range of solids, including plant materials, filter cakes, pellets, granules and some fibrous or swelling materials. They are widely used for herbal extracts, APIs, fine chemicals, food ingredients and specialty products.
3. How is an agitated extraction tank different from a percolation column?
Percolation columns rely on solvent flowing through a relatively static bed of solids. Agitated extraction tanks use mechanical mixing to suspend solids and solvent together. This often provides faster extraction, better temperature control and greater flexibility for different raw materials, especially those that are difficult to percolate.
4. Can Nanjing Hjchem supply lab, pilot and industrial tanks?
Yes. Nanjing Hjchem Equipment Co.,Ltd designs and manufactures laboratory, pilot and industrial-scale agitated extraction tanks. A consistent design approach across scales simplifies process development and scale-up.
5. Can the tanks be integrated with concentration and distillation equipment?
Absolutely. Our agitated extraction tanks can be integrated with vacuum concentrators, solvent recovery systems, molecular distillation units, spray dryers, forming a complete process line from raw material to final product.
6. Are explosion-proof or ATEX options available?
For processes using flammable solvents such as ethanol, we can provide explosion-proof electrical components and ATEX-compliant designs, including motors, control panels and instrumentation, in accordance with your local regulations and hazard classification.