Reducing Waste in Tablet Coating

Q. In our tablet-coating process, we are losing up to 15% of our coating solution in each processing run. What can we do to prevent this problem in order to reduce waste and increase our cost efficiency?

A. Wasted coating material is an industrywide issue for companies using standard (conventional) tablet coaters, with the average coating loss between 10 and 15%. The only way to reduce loss in conventional coaters is to slow down the spray rate and airflow. This will improve efficiencies but lengthen the coating process. Although it comes at a significant capital cost, the most forward-thinking way to solve this problem now and in the future is to investigate the benefits of installing a high-efficiency tablet coater. These advanced coaters offer a variety of features that can streamline your processing.

For example, the size and shape of coating pans plays an important role in efficiency. Traditional coating pans are short in length and large in diameter, which creates a thick tablet bed when solids are put in the coater. Thicker tablet beds have a zone in the middle that is slow moving, and tablets in this area do not get exposed to the surface of the bed as often. The result is a longer coating process that uses more coating solution and wastes energy.

On the other hand, high-efficiency coaters have coating pans that are longer in length but smaller in diameter, which allows the tablet bed to be spread wider and eliminates the slow-moving zone. When tablets are in constant motion, they enter the spray zone more often. This leads to faster coating times, as well as less wasted coating materials. As an added bonus, tablets are coated more uniformly in this type of pan.

Advanced tablet coaters also reduce waste by eliminating spray drying. Conventional coaters send airflow from the top or side of the coater, across the spray zone, through the tablet bed, and out. Bringing hot air into direct contact with spray while it is airborne, however, dries part or all of the coating solution before it hits the tablets. The result is wasted coating product.

High-efficiency coaters are game changers because airflow enters from beneath the tablet bed and is distributed over the entire length of the pan. All airflow through the tablet bed is in the direction of flow, thereby leaving no hot air in the spray zone. High-efficiency coaters ensure droplets are wet when they hit the tablet surface, resulting in the use of less coating solution to achieve uniformity.

—Martin Hack, vice-president and general manager of L.B. Bohle.

If you have a problem with your equipment or process, an industry expert may have the solution. Please send your question to Jennifer Markarian, editor of Equipment and Processing Report, and we may be able to provide an answer in a future issue. All questions will remain anonymous.