Types Of Agitator
These vessels can be provided with different types of agitators such as anchor type, propeller type,paddle type, pitched blade turbine type of high-speed homogenizer
TYPES OF AGITATOR FOR REACTORS:
These are most efficient axial flow impeller. It is recommended for blending, solid suspension, heat transfer etc. It provides maximum flow at minimum power. Mostly available in three blade version. But different number & width of bade are also common in special applications. This is also called as fabricated propeller.
PITCHED BLADE TURBINES
These are axial mixing impeller with considerable amount of radial flow. It produces suction when placed near the liquid surface. Hence used for blending of immiscible liquids, solid incorporation etc. It is also a preferred choice for applications where the viscosity change during the process is large. These are mostly available in four blades @ 45 degree. But different numbers of blade with various angles are also used depending on application.
Mostly used for gas dispersion application. Curve blade (Concave, parabolic etc.) disc can handle 2 to 6 times more gas than flat blade disk turbine. Power drop between gassed and un-gassed condition is very less than conventional flat blade disk impellers. Hence it is preferred choice for gas dispersion application viz. Fermentation, Hydrogenation, Oxidation, Carbonisation, Ethylation etc.
ANCHOR/GATE TYPE IMPELLER
Anchor/Gate type impellers are close-clearance impeller that fit the contour if the vessel. This impeller provides adequate mixing under the laminar flow conditions encountered viscosity applications for heat transfer. These are many applications that other type of impellers is integrated with the anchor. This impeller sweeps the whole wall surface of the vessel and agitates most of the fluid batch through physical contact. Anchor impellers are used for liquid viscosities between 5,000 and 50,000 cP. When reaction /mixing homogeneity is required, other type of impellers are recommended.
HIGH SPEED DISPERSER
Disperser disk provides large amount of shear and mostly used for liquid-liquid dispersion and powder dissolution or de-agglomeration etc.
HIGH SHEAR MIXER
Tremendous amount of shear is required to produce stable emulsion and fine dispersion. Hence all the impeller blades are designed at high tip speed and high shear rate.
For low and medium viscosity fluid premixing and De-agglomeration of particles to every fine and stable dispersion is a well known use.
For high viscosity fluid co-axial or multi-shaft agitators are recommended with stator rotor or pump may be used for flow through inline homogenizer.
This machine is used for producing stable emulsions and very fine dispersion in micron range. Ultra high shear mixer can be used for sub micron range dispersion and emulsification.
SEALING OF SHAFT:
Reactors are provided with Gland box or Mechanical seals for shaft sealing arrangement of the shaft with the vessel.
Stuffing boxes accomplish sealing by the radial expansion of a soft, deformable material such as layer-wound rubber, plastic, fiber, or a combination of these. Stuffing boxes are lower in initial cost than mechanical seals but are significantly higher in maintenance expenses.
Mechanical seals are designed to prevent leakage between a rotating shaft and its housing under conditions of extreme pressure, shaft speed and temperature. Mechanical seals can be single acting or double acting. Single (acting) mechanical seals have one sealing gap.
The following type of mechanical seal:
SINGLE MECHANICAL SEAL:
A single mechanical seal consists of two very flat surfaces that are pressed together by a spring and slide against each other. Between these two surfaces is a fluid film generated by the product. This fluid film prevents the mechanical seal from touching the stationary ring. An absence of this fluid film (dry running of the pump) results in frictional heat and ultimate destruction of the mechanical seal.
Mechanical seals tend to leak a vapor from the high pressure side to the low pressure side. This fluid lubricates the seal faces and absorbs the heat generated from the associated friction, which crosses the seal faces as a liquid and vaporizes into the atmosphere. So, it's common practice to use a single mechanical seal if the product poses little to no risk to the environment.
DOUBLE MECHANICAL SEAL:
A double mechanical seal consists of two seals arranged in a series. The inboard, or "primary seal" keeps the product contained within the housing. The outboard, or "secondary seal" prevents the flush liquid from leaking into the atmosphere.
Double mechanical seals are offered in two arrangements:
Back to back
Two rotating seal rings are arranged facing away from each other. The lubricating film is generated by the barrier fluid. This arrangement is commonly found in the chemical industry. In case of leakage, the barrier liquid penetrates the product.
Face to face
The spring loaded rotary seal faces are arranged face to face and slide from the opposite direction to one or two the barrier liquid penetrates the product. If the product is considered "hot", the barrier liquid acts as a cooling agent for the mechanical seal.
Double mechanical seals are commonly used in the following circumstances:
a) When aggressive media is used at high pressures or temperatures.
b) For many polymerizing, sticky media stationary seal parts. This is a popular choice for the food industry, particularly for products which tend to stick in case of leakage.
Thermosyphon Vessel is used as a storage & unpressurising unit. Used for double mechanical seals in tandem seal arrangement. This is equipped with cooling coil inside the shell to bring down the temperature of buffer fluid coming from seal to Thermosyphon Vessel.
|Nominal Capacity (Lts.)
||Vessel Dimension Dia, (mm) x Straight Height (mm)
||Shaft Diameter (mm)
||Exchange Surface Area (sq. meters)
||Standard Design Pressure
||Half - Tube
||600 x 900
|Inside -3 bar or vacuum
|Jacket - 3 bar
|Half Tube 6-Bar
||800 x 1000
||1000 x 1400
||1200 x 1800
||1300 x 1900
||1400 x 2000
||1600 x 2500
||1750 x 2500
||2100 x 3000