Sepro Agitators Built For Gas Dispersion and Mechanical Stability

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Many applications in chemical processing, waste and water treatment, food or pharmaceutical productions, petrochemicals and minerals processing, require the injection of gas into the mixing vessel. This can be a variety of gasses, including air, oxygen, hydrogen, or a combination. The volume of gas introduced and the rate of introduction is critical for the efficiency of the system and operation of the gas dispersion agitator.

Too much gas beneath the gas dispersion impeller can cause cavitation, or ‘flooding’, resulting in poor dispersion, mechanical instability and solid settlement. Conventional aerofoil impellers, as used in convention leaching, blending, or general mixing, can only tolerate low volumes of gas before becoming ineffective.

The Sepro CHG4 high solidity, gassing impeller was specifically designed to accommodate the high gas dispersion requirements. Typically used in bioleaching, hydrogenation, fermentation, cyanide destruction and other similar processes, the Sepro CHG4 gas dispersion impeller has a high solidity ratio, meaning the gas ‘sees’ a rotating disc, minimizing the amount of gas passing through the impeller.

The impeller’s high pumping capacity provides effective gas retention, meaning the interfacial contact between gas and solid is extended. Older systems allow gas to exit the vessel almost immediately.

In mineral processing, the Sepro CHG4 impeller is used in bioleaching, cyanide detox, pressure lead reactors and more,  where effective gas dispersion and gas retention is critical for excellent process performance.

The Finer Details

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Agitator Components

Agitator Shafts

Shafts are manufactured to a stringent straightness tolerance of 1mm/metre of shaft length. Often, half of this limit is achieved with our standard agitator shafts. Ears are attached to circular hubs using deep penetrating continuous welds, which are systematically dye penned. Ears are never attached directly to hollow shafts. Hubs and ears are machined using CNC machines to minimise clearances between ear and hub; this ensures weld strength.

Mounting Bases

Mounting bases are critical components in ensuring gearboxes are correctly aligned and mounted to the beams or structure. This reduces the potential for twisting or flexing of the gearbox housing — a common cause of failure of proprietary gearboxes. All large, top entry Sepro Mixing agitators are fitted with integral mounting bases, or pedestals where necessary. All bases have machined pads, at the top and bottom, to ensure accurate and positive alignment

Large Sepro Mixing Impeller Blades

Impeller Blades

Sepro Mixing manufactures impellers for all applications, including high viscosity duty. However, as most applications are either flow or shear dependent, the Sepro Mixing CHF range of high flow impellers, or the Sepro Mixing CHG range of high efficiency gas dispersers, are the workhorses of the Sepro Mixing stable. Other impellers available are flat blade radials, pitch blade turbines, high viscosity anchors and helical impellers. We also build specialized impellers for pumping, foam breaking dispersion and Solvent Extraction.

Impellers can be manufactured in all materials, including exotics. They can  be supplied coated in rubber, urethane, epoxy or other specialized materials. Impeller blades are carefully checked to ensure that tolerances on angle, camber and curve are maintained. Out-of-spec blades are rejected. Blades are machined where hub and ear attach to ensure flatness. Often, the problem of loose blades is caused by blade flexing, resulting from a lack of flatness and poor contact with the hub ears.

Impeller blades in excess of 2″ thick and 21ft in diameter have been manufactured by Sepro Mixing in Canada.

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