KORSCH meets temperature challenge with water-cooled turret

KORSCH AG has a tradition of constant innovation, much of which is driven by the challenges of meeting specific customer needs. A case in point is the company’s recent development of a water-cooling solution to overcome the problem of low melting point temperatures in some powders when under compression.

The innovation uses water flow through channels in feeder plate and tool turret to achieve cooling across the whole tableting process and can be offered as a customized solution for fitment to KORSCH presses.

Material temperature challenge

The processing of certain tablets for the pharmaceutical and food industries can be challenging when the compression powder exhibits melting temperatures of around 6°C, which requires maintaining maximum die table temperature at 5°C., significantly below normal tablet press operating temperatures.

A KORSCH technical investigation on behalf of a customer studied the temperature behavior of the compressed material flow from material feed to tablet discharge. The study concluded that the customer’s requirements could only be met with a comprehensive cooling strategy that focused particularly on the decisive role of die table temperature, which is subject to external heat input during the tableting process.

Cooling the material flow

Constant cooling along the tableting process was ultimately achieved by the following material flow measures:

• Limiting production room temperature to 15°C + 1°C at 50 % + 5 % humidity.
• Provision of a compression material at powder temperature of 4°C + 1 °C.
• Provision of a fluid cooling medium (water or compound) maintained at 2°C + 0.5°C including reprocessing.
• Engineering a cooling medium flow through the material feed, the clamping plate, and the turret (including die table) via separate cooling circuits.
• Fitting material feed with an insulated cooling jacket to maintain feed temperature below 4°C.
• Mounting an additional cooling plate on the feeder cover to keep clamping plate temperature below 4°C.
• Equipping the turret assembly with cooling channels through which cooling medium enters the inner area via a swivel joint and is fed through the upper part of the turret to the die table.
• Further guiding cooling medium around the dies up to the edge of the die table and on into the lower part of the turret before finally being pumped out of the inner area into a reservoir for cooling and recirculation.

Development and testing

To speed the development process, KORSCH engineers carried out prior CFD flow and temperature analysis of the turret cooling with iterative improvements. These simulations produced a design solution that kept die table temperature below 4°C even on its outside surface.

Prototype testing involved operating the cooled press ‘empty’ for 10 minutes to set the steady-state temperature of the die table to < 4 °C before adding powder flow.

Test results confirmed temperatures along the entire material flow at below 5°C. Measurements carried out with thermocouples at representative points of the material flow detected no condensation in the compression zone or melting of the compression material. Tablets produced on prototype met the requirements of European Pharmacopeia 2.9.5. for uniformity of mass, etc.

The development featured here represents the premium version of a cooling concept that can be individually adapted to customer requirements, from punch tip cooling to inside-cooled turrets and comprehensive cooling concepts. KORSCH is thus able to offer a perfectly customized cooling solution for customers who need to reduce heat during tablet compression.

Resources

Click on A Cooled Material Flow from the Material Supply to the Tablet to access original article.