A. Liquid mixing1. Soluble liquids (including simple liquid)Propeller impellers (of various designs) or pitched paddle impellers of high discharge circulation performance are used at an extremely low Pv value (mixing drive force per unit volume). Impellers with large and wide blades or paddles may be used at low speed of revolution for relatively large volumes (approx. 10m3).B. Solid-liquid mixing(Solid particle dissolution, specific fluidization, suspension, dispersion, colloidal suspension, crystallization, etc)Recently, mixing needs for this type of liquid are met in a more energy-saving manner by propellers of higher discharge type (HR100 impeller, HR700 impeller) or improved pitched paddle type (HR320 impeller, HS400 impeller).Multi-bladed turbine impeller (DS impeller), fan-turbine impeller, pitched turbine impeller, pitched paddle impeller are usually preferred for high shearing and discharge circulation performances.The ratio of the blade diameter to the tank diameter (d/D) is between 0.15 and 0.4. The impeller height should preferably be near the interface. For liquid mixing ratio of 1:2 or more, or when Z/D is 1.2 or greater, a multi-stage blade type will give a better result. Specific gravity differences, mixing ratios, tank shapes, non-baffle eccentricity, baffle conditions and other factors must be taken into full consideration.Propeller impellers are used at a low Pv value for soluble solid particles. Paddle type impellers may be used at low speed of revolution in case of large tank volumes (over 10m3). Non-soluble particle may be mixed by using a combination of an impeller of high shearing performance and an impeller of high discharge circulation performance at a relatively high speed of revolution.For solid particles that tend to float to the surface, the baffle should be positioned at about half the liquid surface to create vortexes and introduce particles into swirls by force.Dissolution of solids accompanies an increase in viscosity. In this case, Impellers with large and wide blades (MR203 impeller, MR205 impeller) will give a better result as they are designed for a broader range of viscous liquids.Flat turbine impeller with disks are most often used for gas dispersion because of their outstanding shearing performance. Impellers with propellers or paddles are also used with gases of fast absorption speed or when the gas supply is small.2. Particle fluidization and suspensionConventionally, impellers with propellers are used with small-volume mixing (up to 10m3) or liquids of low particle density, and pitched paddle impellers with large-volume mixing (over 10m3) or liquids of high particle density. HR800 impeller of high discharge characteristics at low drive force is a better choice when particle fluidization is critical. Similarly, HS600 type impeller may be used at the tank bottom for uniform mixing and uniform discharge at the same time when uniform dispersion in the tank and uniform discharge of slurry from the bottom is critical.C. Gas-liquid mixing1. SpargingManufacturing equipment is normally designed for combination of two or more stages. Turbine impellers are often used for dispersion at the bottom stage and the high discharge propeller impellers (axial flow blades) in the middle or top stage for promoting circulation and gas stagnation. Inclined turbine impellers (pitched turbine impellers) generate mixed flows and are often preferred for ideal contact between gas and liquid containing solids. For liquid mixing, holes are often provided in the disk to promote convection between over and under the disk. For gas dispersion, however, such holes are not used to eliminate short passing of gas. Cone cave turbines are often used because of the relatively large differential ratio Pg/Po between drive power without gas introduction (Po) and drive power with gas introduction (Pg). This means the mixer requires only a small motor drive power. The turbine type impeller HS100 from recent efforts is designed to meet conflicting needs of aeration drive characteristics and gas absorption performance.This type of gas and liquid contact mixing is found in surface aeration tanks in water treatment plants. Various products of high efficiencies (propeller, turbine, cone, and other types) have been developed. Satake have developed high lift type surface aeration impellers (SA100 impeller, SA200 impeller) in consideration of mixing effects in the aeration tank.The “super-mix” impellers, developed exclusively for this type of surface aeration, are designed to allow for large liquid depths.2. Non-soluble liquids1. Solid particles dissolution2. Surface aeration6
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