Loss-in-Weight Feeder for Continuous Processes

Switching from batch to continuous processing can be well worth it. In direct compression and dry granulation applications, the advantages are particularly apparent in the feeding of recipe ingredients. Overall operating costs drop, the feeders require less space, and consumption of recipe ingredients is reduced. What's more, high feeding accuracy helps meet rigorous end product specifications. Coperion K-Tron supplies the right technology with the K3 Pharmaceutical Feeders.

Both continuous direct compression processes as well as continuous mixing for dry granulation processes require accurate feeding of APIs and various excipients into a continuous mixer. Typical residence times in continuous mixing are minimal, usually just a matter of seconds. Intake speed and feed accuracy are of high importance for the overall mixture homogeneity. In many cases, the mixer is dependent upon the feeders, whereby the feeder’s mass flow represents the decisive variable for end product quality. In most cases, several feeders are used at the mixer inlet, one for each excipient in the recipe as well as one for the actual API. Since most pharmaceutical materials are not free-flowing, the construction and design of the feed hopper, screw, and agitator configurations, as well as the feeder’s refill system must be engineered such that a constant flow of ingredients into the process is ensured.

The K3 Pharmaceutical Feeder line from Coperion K-Tron takes all of these requirements into account. The significantly reduced size allows the feeders to be arranged flexibly around the same single inlet on the mixer. With the Quick Change module, cleaning cycles are markedly shortened. Furthermore, due to its modular construction, feeder output can be increased eightfold by using a 35 mm screw instead of a 20 mm one.

Simple Handling Included
The K3 Pharmaceutical Feeder line’s modular construction simplifies cleaning and maintenance, saving time and effort. Moreover, the Quick Change design allows for easy, rapid product changes; the feeder module, including the horizontal agitator and screw, can be quickly uncoupled from the drive. Only two clamps need to be loosened to remove the feeder module and replace it with a clean one. Both the QT20 and QT35 feeder modules can be used with the same scale and drive combination. They are interchangeable and can be implemented based on the product to be fed, the desired feed capacity, and the necessary weighing resolution. To achieve an optimal result in WIP cleaning, each unit features a two degree pitch, maximizing drainage during the cleaning process. The re-worked sealing concept prevents product accumulation on the sealing lip and safely keeps the product within the process. The K3 feeder line fulfills the strict requirements of the pharmaceutical industry, including cGMP guidelines and standards, and is constructed exclusively with FDA-approved materials.

High-Accuracy Weighing
Due to the high demands on feeder accuracy in continuous pharmaceutical processes, loss-in-weight screw feeders are usually implemented for feeding dry ingredients. In the case of bulk materials with highly variable bulk density, gravimetric feeders can identify and compensate for resultant — in some cases significant — variations in feeder output, because they continually calculate the true mass flow based on the system’s weight loss during a particular time interval. This method also provides an advantage with cohesive materials that often tend to bridge or pack in the hopper, such as APIs and micronized excipients. Coperion K-Tron’s gravimetric feeders feature state-of-the-art SFT weighing technology. The D4 platform scale used in the K3 feeder line has the same modern, sanitary construction as Coperion K-Tron’s proven D5 scale. Smooth, crack and crevice free surfaces prevent dust and product deposits, making cleaning effortless. The trapezoidal design facilitates the compact arrangement of a group of feeders within a minimal footprint compared to the round form of previous designs. Since space is often limited, this advantage is especially helpful when feeding several ingredients into one inlet. The core of the new D4 scale is the SFT scale technology. It is based on the vibrating wire principle, delivering a precise weight signal at a resolution of 1:8,000,000 in 20 ms. At 450 measurements per second, it registers the tiniest fluctuations in feeding and can react correspondingly quickly. The electronics include linearization, temperature compensation, and a digital low pass filter to reduce the effect of machine vibrations. Due to its digital design, no calibration is required.

Intelligent Flow Activation
As mentioned above, both APIs and excipients with poor flow properties create a number of challenges. In such cases, the proven ActiFlow™ intelligent bulk solid flow aid can be used. ActiFlow works without coming into contact with the product. This bulk solid activator consists of two parts, the device itself and the control unit. The ActiFlow device is mounted onto the outside of the hopper, above the feeder. Working together with the ActiFlow control, the material in the hopper is activated with an optimized frequency and amplitude. ActiFlow is self-calibrating: the KCM feeder control constantly monitors the system and automatically adjusts the frequency and amplitude to fit the fill level and material behavior in order to prevent flow behavior disruptions and bridging.

Designed for Continuous Processes
The modularly constructed K3 feeders are specially designed for the increasing demands of continuous processes. Thanks to the reduced footprint, several feeders can be grouped into one cluster, for example in continuous processes such as direct compression (CDC), heat melt extrusion, wet and dry granulation, and continuous loading, as well as in traditional batching processes. Furthermore, traceability can be significantly increased with the addition of an optional extension to the new KCM-III feeder control, allowing process data to be stored for up to 180 days.