INTRODUCTION TO A NAUTA BLENDER or NAUTA MIXER:
NAUTA mixer Or blender refers to a popular industrial mixer which consist of a conical vessel (like a funnel) in which an inclined screw rotates in both planetary, as well as, in axial motion. Which means, the screw rotates along its own axis of rotation while taking a planetary along the internal wall of the mixer vessel.
The conical blender Or mixer Or Dryer is very popular among many manufacturing industries including Pharmaceutical, Nutraceutical, Dyes and Pigments, Food colors, Food items, Spices, Cosmetics and many more. Let is discuss it objectively, as well as, in comparative fashion (comparing with other popular industrial blenders such as Octagonal Blender, Double Cone Blender, V Blender, Vertical Conical Spiral Blender and Ribbon Blender.
One of the Best Books on Powder Technology for You
HISTORY OF NAUTA BLENDER or NAUTA MIXER:
The word NAUTA has nothing to do with Nautical Science Or Mariners Or Sailors. The word NAUTA is believed to have arrived from the legendary Mr. Johannes Ewardus Nauta (1890 - 1957), the founder of Nautamix company, who first started manufacturing of the conical mixer in 1939 in Netherlands. Soon the conical mixer NAUTA became very popular and got sold worldwide. Later Nautamix company got acquired by another giant engineering OEM and today few companies globally owns the trademark rights of "NAUTA". At the same time, many local engineering OEMs too are manufacturing the conical mixer without the name NAUTA, as they have studied and understood the technology.
TYPES OF SOLID-SOLID MIXINGS:
Solid-Solid mixing (may it be in powder-powder Or granules mixing) is usually classified into four categories viz.
A. Convective Mixing:
Convective mixing essentially involves the movement of mass in bulk Or gross displacement of the mass which leads to mixing on a large level.
B. Shear Mixing:
Shearing action takes place due to sliding of a layer of powder or solid mass past another layer. Shear mixing may take longer than convective mixing, as the later appeals to the bigger volume of mass.
C. Diffusive Mixing:
The kind of mixing resulting from the random movement of particles within the mass is known as diffusive mixing, which results into more homogeneous mixture, however, can be a lot time consuming.
D. Chaotic Mixing:
The most irregularly patterned mixing, mostly resulting out of a random or undefined combination of convective and shear mixing is termed as chaotic Mixing.
NAUTA MIXER - ADVANTAGES AND APPLICATIONS:
One of the Best Books on Powder Technology for You
Conical Mixer (also known as the NAUTA Mixer) simultaneously generates local and rational convective mixing currents with the help of its axially rotating screw which also rotates in the planetary motion (along the inner wall of the cone), while its helical ribbon lifts the power mass to the top from the bottom of the cone.
While Horizontal Ribbon Blender, Vertical Conical Ribbon Blender and V Blender works on the principle of convective mixing, the Octagonal and Double Cone Blender follows the shear type mixing. When it comes to fine and homogeneous mixing, NAUTA is found to be the preferred choice, as the local convective currents gradually dominate the rational mixing currents resulting into more consistent and homogeneous mixing.
NAUTA mixers blenders are popularly used in many industries. In some cases, it is also used as a Mixer-Dryer, thereby removing the core moisture Or recovering the solvents.
MAJOR COMPONENTS OF THE NAUTA MIXER - BLENDER - DRYER:
1. Vertical Conical Shell (with Optional Limpet and Insulation) and the Top Dish: This vertical conical and optionally limpeted vessel is designed to handle desired volume of the mass with an optional provision of heating and vacuum (however, it is not mandatory). The limpet usually covers almost 80% of the height of the vessel. Incase it is limpeted, the conical vessel is also insulated with hot insulation material such as Mineral Wool Or Rock Wool and further cladded. The top dish is designed to take weight of the drive assembly, as well as, has a number of nozzles including the manhole.
2. Agitator Or Stirrer: A specially designed agitator majorly consist of two parts viz. a Rotary Arm and a Screw with helical ribbon on it.
Rotary Arm is connected to the vertical central shaft, which is driven by the central motor and gearbox at a low rpm. The objective of this Rotary Arm is to rotate along the central axis and thus carry the hanging screw along the inside wall of the cove (like a merry-go-round). At the same time, the hanging screw rotates along its own axis and is driven by a separate motor and gearbox. The shaft that drives this motion is passed through the hollow central shaft of the rotary arm. The complex gear arrangement ensures that both Rotary Arm and Screw rotates as per their desired orbital and axial path.
The Hanging Screw needs to be well balanced dynamically, as well as, passes through a suitable Mechanical Seal (fulfilling the vacuum and temperature requirements). As per the required torque calculations, both the AC frequency Motors and Gearboxes are designed. Suitable couplings may be provided inside the vessel, as well as, outside before gearbox in order to protect the drive assembly from damage due to rare case of jamming of screw. A soft starter along with VFD (variable frequency drive) is recommended to manage the torque.
3. Optional Vacuum Filter Assembly: Incase of a vacuumized operation, a vertical cylindrical filter housing mounted on the vacuum nozzle located on the top dish. The filtration assembly includes a course PP filter (say 10 to 20 micron) whose objective is to arrest the powder particles from going into the condenser Or vacuum pump along with the vapors.
4. Optional Chopper assembly Or Lump Breaker Assembly: A high speed chopping set of blades (rotating at around 200 to 300 rpm) mounted inside of the conical vessel (on the lateral surface) can be optionally provided with a gearbox and an AC frequency motor.
5. Optional Condenser: Typically a Shell and Tube Type Heat Exchanger is used to condense the vapors coming out of the Conical Dryer. Usually the process side fluid (vapors) are passed through tubes, whereas, on the Shell side the utility fluid (mostly chilled water Or cooling water) is circulated. However, it can be the other way around too (depending on the heat load calculations). Condenser can be insulated and cladded for avoiding heat loss to the ambience.
6. Optional Receiver: A solvent recovery receiver is provided at the bottom of the STHE condenser. Receiver can be either Vertical Cylindrical with legs supports Or Horizontal Cylindrical with saddle supports. A vacuum breaking arrangement is provided with a Control/ On-Off valve on the receiver.
7. Optional Vacuum Pump: A suitable capacity Vacuum Pump is connected to the system (mostly to the receiver), which creates vacuum inside the Conical Dryer, and, also facilitates the extraction of the vapors, hence complements the condensation process.
8. Optional Water Heating system Or Low Pressure Steam (for heating the Dryer, Shaft, Ribbon): Incase of a Hot Water System, a dedicated skid mounted vertical cylindrical vessel is provided with external heating i.e. either with steam (LPS) Or with Electrical Heaters. A circulation pump pushes the hot water into the Limpet, and the return water goes back into the Hot Water Generation tank. The level guage/switch on this tank ensure water doesn't spill over, and, make up water valves gets ON when level goes down. The Temperature sensor on the Hot Waters Tank, as well as, sensor on the Inlet of the Limpet coil together controls the flow of Steam (through PID control valve) Or the Electrical Heater, thus ensures the inlet water temperature stays in control. Incase of direct steam heating, the PID valve ensures steam is throttled and uniform temperature is maintained in the limpet.
9. CIP Or Spray Ball arrangement: Optionally, spray balls can be provided on the top dish of the conical shell, which can facilitate cleaning and washing of the main vessel post the batch operation is over.
10. Rotary Bottom Discharge Valve: The blended product is taken off from the bottom and is usually facilitated by the rotary discharge valve. A motorized rotary valve serves the purpose of uniform discharge flow without much wastages. In the rare case scenario, a knife gate valve Or a butterfly valve can also be used.
One of the Best Books on Powder Technology for You
MATERIAL OF CONSTRUCTION:
Post a Comment