The availability of a new glass-lined agitator blade design that combines the advantages of hydrofoil agitator blades and trapezoidal agitator blades for improved mixing in glass-lined vessels has been announced by De Dietrich Process Systems.

The geometry of the new blade, trademarked OptiFoil, is said to maximise the pumping action required for homogenisation, suspension, heat transfer and crystallisation of fragile particles.

Furthermore, the shape of the blade produces effective mixing of minimum product volumes, creates strong flow at the reactor bottom, and facilitates evacuation of the vessel by reducing the gap between the blades and the bottom of the reactor, keeping particles in suspension while they exit the vessel.

Smoother contact

According to the company, the blades can mix a minimum of five gallons in a 500-gallon vessel, and 20gallons in a 4000-gallon vessel.

The pitch angle of the OptiFoil blades also results in smoother contact with the product than vertically-orientated trapezoidal blades, less shear, and is said to prevent the alteration of fragile crystals.

In addition, the blades can reportedly mix higher viscosity liquids than can hydrofoil blades or standard flat blades, and produce axial and radial flow characteristics that are suitable for virtually every process.

Engineered for use in glass-lined steel vessels, OptiFoil blades are available as an option on one-piece glass-lined mixers, or as removable blades when used in conjunction with the company’s GlasLock interchangeable glass-lined agitator blade system. A range of sizes allows matching of the blades to the process and vessel capacity.

Top-entering agitators

For Chemineer, the focus is on ease of maintenance. With this in mind, the company’s new model 20HT/GT top-entering agitators feature a swing out seal change design for easy seal maintenance and reduced maintenance cost.

With these agitators, there is no need to lift or remove the gearbox, saving labour and downtime.

For replacement of the mechanical seal, simply rotate the gearbox 90° around the pivot pin.

The top of the seal pedestal opens for a clear, line-of-site view and ample room for easy removal of the coupling half and seal assembly.

Chemineer Model20HT/GT agitators are designed for a wide range of service in many industries, including chemicals.

They feature a new, high-efficiency gearbox with helical gearing and a parallel shaft configuration designed specifically for agitator service.

The agitators also feature a modular design package that reduces the number of replacement parts that need to be carried in inventory by the customer.

The wide range of speeds available with the new agitators provides improved process control and greater application versatility.

Model20HT/GT agitators are designed to meet AGMA, OSHA, ANSI, IEC, DIN, EU and ATEX standards and requirements. A variety of seal options are available for application versatility. It also has high energy efficiency due to an optimised gear design and lighter weight shaft diameter requirements.

A standard cast dry well seal eliminates lubrication oil leakage from gearbox – this design is superior to maintenance intensive, unreliable lip seals.

0Reversible rotation to meet a variety of process requirements. Reliable performance and long life resulting from the cast gearbox with heavy duty output shaft and bearings

Meanwhile, Munson Machinery’s focus is on sanitary rotary continuous mixing. Its new model 16-4SS mixer blends ingredients in ratios as extreme as one part per million with 100percent uniformity regardless of disparities in the bulk densities, particle sizes or flow characteristics of ingredients, which may include liquid additions. Capacity ranges from 2.45m3/h at one-minute residence time, to 1.19m3/h at two-minutes residence time.

Eliminating internal restrictions

The slowly rotating 406 x 1219mm cylinder contains proprietary mixing flights that impart a forward- and reverse-pitch, ‘back flow’ mixing action that distributes bulk ingredients thoroughly and gently in short residence times, while eliminating internal restrictions where material could plug or accumulate.

An optional internal stainless steel spray line with spray head allows uniform introduction of a liquid additive to the blended material.

The line is suited for spray coating, de-dusting, perfuming, agglomerating and conditioning of materials. The tumbling and cascading effect produced by internal flights achieves 100percent uniform distribution of liquids with no overspray.

Unlike designs that shift masses of material back and forth and distribute weight unevenly, the steadily rotating cylinder reportedly produces a gentle and consistent mixing action using a smaller drive motor of 0.5HP. RPM may be adjusted to compensate for angles of repose and densities of different mixtures.

The drum angle can be adjusted from 0° to 12° to control product residence time and throughput rate.

Solid weirs on the discharge end act as a ‘dam’ allowing materials to build a ‘residence volume’ in the machine and overflow the weir.

Dust-tight diaphragms at both the intake and discharge ends are securely retained against the mixing drum and revolving cylinders, preventing the escape of dust or fumes.

Material is fully discharged at the end of a run for rapid sanitising and changeovers.

The mixing drum is supported by heavy-duty Nylon or hardened steel ‘trunnion rollers’ that ride on machined ‘trunnion rings’ for minimum power consumption and rapid maintenance.

The company also offers large-scale sanitary rotary continuous mixers with up to 20HP in diameters to 152cm and lengths to 457cm, having capacities of 121m3/h at one-minute residence time, and 59m3/h at two-minutes residence time.

Compact mixer

Developed by Hosokawa Micron, the new Intensomix is a cylindrical mixer having a central shaft with three agitating blades. Their design ensures transport of the material upwards in the centre of the mixer. The Intensomix is a compact mixer that can efficiently and speedily blend a variety of materials with viscous liquids which in other blenders may form lumps and agglomerates.

The Intensomix features two high-speed lump breakers fitted to the mixer walls and these effectively disperse and blend in viscous liquids. The mixer is in monobloc design with a compact discharge valve for optimum cleanability.

Access door and drainage openings have been manufactured using water jet cutting technology sealings under an angle of 45degrees, providing a dust and water-tight operating environment. The mixer is available in sizes up to 25000litres.

Independent R&D

Mixing is central to the vast majority of processes in the chemical industry. Whether blending, dosing, dispersing, carrying out chemical reactions, operating a bioreactor, formulating a product, aerating, stripping, extracting or crystallising, close attention to mixing can yield substantial economic, safety, environmental and product benefits.

UK company BHR Group provides independent research and consultancy services in fluid engineering and process technology to a wide range of markets worldwide. Over the years, its work has included many aspects of mixing, including single and multiphase, design, scale up/scale down and practical applications.

One recent success for a chemical company concerned a problem with the intense mixing needed in a low-density polyethylene reactor. Poor mixing was leading to poor thermal stability, high initiator requirements and a lot of product wastage.

BHR Group investigated all the main design parameters around the reactor, including reaction rate and timescale, micromixing of initiator, feed positions, impeller types, and baffling.

This investigation found that very good mixing is required in LDPE reactors to blend in initiator rapidly, to ensure that mixing produces a homogeneous distribution and remove the heat of reaction to ensure decomp products are minimised and initiator usage maximised. Even local hot-spots were found to cause runaway reactions.

The company then recommended modifications to the production process including modified impellers, feed positions and baffle arrangements on both mixing and reaction. The result was improvements in both reactor thermal stability and product quality.