The Paderborn-based company Gebrüder Lödige Maschinenbau specializes in the production and development of application-specific process technology and is an expert in basic process engineering operations such as the mixing, drying and granulation of bulk materials.

Lödige supplies customized mixers, dryers and reactors to companies from the life science industry to the chemical and building materials industries. The plowshare mixers achieve the highest mixing quality with short mixing times and excellent product protection. They work according to the spinning and whirling process developed by Lödige. The mix is always completely caught by the blades, so that there are no zones with little movement. This allows various process steps to be combined, for example mixing, granulating and drying.

Ploughshare mixers are used in almost all industries for a wide variety of mixing tasks. They consist of a horizontal cylindrical drum in which the centrally mounted shaft, equipped with ploughshare blades, moves the product into a mechanically generated fluidized bed. Due to the intensive mixing and the resulting frequent contact of the particles with the optionally heatable apparatus wall, a high heat transfer can be achieved without local overheating. The intensity of the particle movement increases during drying as the moisture content and viscosity decrease.

When nothing is allowed to escape

Lödige used simple straight plug-in connections with release sleeves in three sizes in the customer project. © Eisele

Lödige machines are specific special machines based on various basic types such as the GMP (Good Manufacturing Practice) ploughshare mixer for pharmaceutical and food applications, a dynamic compulsory mixer. In a system for the pharmaceutical industry in which a hormone preparation for veterinary medicine is to be processed, absolutely safe containment is important to prevent hormones from being released into the environment. Even minimal doses of these can cause strong reactions, even in humans. In addition, absolutely no substances from the environment may enter the cleanroom.

In this application, batch mixing, granulation and drying take place in one and the same machine, whereby the process area is located in the clean room and the connections and operating elements are accessible from an external technical area. The ploughshare mixer has a temperature control jacket that ensures gentle heating and drying of the product in the process. In order to achieve faster drying at a low temperature, a vacuum pump generates negative pressure in the process chamber. This not only protects the temperature-sensitive product, but also supports safe containment, as no material can escape under negative pressure. As the machine is used in an American pharmaceutical company, the regulations of the Food and Drug Administration (FDA) must also be met in addition to the GMP requirements mentioned above.

Top priority for absolute tightness

As the connections need to be particularly tight and secure, Lödige used stainless steel connections from Eisele Pneumatics ' 17A range for various compressed air connections required to operate the paddle dryer. The easy-to-clean design and corrosion resistance of the stainless steel connections also played a role. The plug-in connections and the associated hoses are permanently installed on the system and only need to be removed for repairs or inspections. Due to the design of the connections, however, this is possible without any problems. Three different connection types are used. Stainless steel was chosen to create optimum hygienic conditions and to enable easy cleaning. The connections come into contact with nitrogen and air as operating media. Neither medium requires any particular corrosion resistance, but in a sterile application they must not be contaminated by the materials or contaminated with particles.