August 6, 2018

Production of antibiotics in the pharmaceutical industry: Significant increase in production thanks to continuous filtration

Typical rotary pressure filter of type RPF A09 with an active filter surface of 2.16 m² for use in pharmaceutical applications.

Significant savings, greater yields and improved throughput – pharmaceutical companies can reap significant benefits by moving from batch production to a continuous antibiotics manufacturing process. One stand-out project improved productivity figures by roughly 150 percent. The rotary pressure filter from BHS-Sonthofen plays a key part in this success story.

Pharmaceutical companies frequently find themselves in a position where they need to increase the production of an ingredient substantially. Before tackling such an expansion project, it generally makes sense to carefully analyze the production process. In one such case, project management evaluated the existing batch process and recommended adding more reactors and changing the separation stage by introducing a continuous process using a BHS-Sonthofen rotary pressure filter of type RPF P02.

The implemented continuous process increased production in the order of 150 percent, while incurring only a fraction of the investment costs of the previous manufacturing process. In addition, changing to continuous filtration increased the yield by close to a third and further improved the profitability of the new process. Moreover, monitoring the continuous filtration and cleaning process online delivers much more consistent product quality while at the same time allowing the manufacturer to reduce the consumption of consumables.

Batch process cannot unlock the full potential

A lot of potential remained untapped in the batch manufacturing process. For example, the amount of active ingredient produced in the reactor exceeded the actual yield after drying by far. That’s because a large amount of the active ingredient was lost in the turbid flow stage at the beginning of filtration due to the agitated Nutsche filter used. The continuous process, in turn, was able to unlock most of this potential.

As a fully continuous separator, the BHS rotary pressure filter with an active filter surface of 0.5 m² was easily able to accommodate double the previous production quantity in a continuous product flow. Also, in contrast to the batch system, which turns the entire solid material of a batch into a filter cake, the rotary pressure filter reduces the cake thickness significantly. This results in a much lower cake resistance.

Loss of the active ingredient is reduced to less than five percent

Due to the thinner filter cake, the filtration pressure can be reduced by a large degree. This enabled the process to be optimized to ensure high performance over the long term. It also allows the use of a much tighter filter medium, which results in an immediate clear flow. This prevents the previously unavoidable turbid flow stage – a decisive advantage of continuous filtration. Thanks to the elimination of the turbid flow stage, loss of the active ingredient is reduced from approx. 25 percent to less than 5 percent in the project.

Moreover, the compact structure of the filter cake, its low thickness and the optimized flow control in the form of a nearly perfect piston flow facilitate highly efficient washing of the solid. Additional online monitoring of the washing filtrates allows the operator to quickly optimize the quantity of the washing agent. The pharmaceutical company has been consequently able to reduce the amount of solvents by roughly 20 percent. This strengthens the entire production process and results in a much more stable configuration of the crystallization stage.

Optimized piston flow cake washing also means that the entire washing filtrate is usable. Here, too, continuous processing in connection with process-analytical technologies (PAT) leads to a more efficient use of utilities and thus higher yields: By reducing the overall solvent consumption in the process, former product rejections – as occurred with the agitated Nutsche filter – are a thing of the past.

Thanks to putting a continuous process in place, batch-based operation with a complex process flow, high consumable requirements and mediocre yield was turned into a self-regulating, easily controllable and highly efficient process.


Rotary pressure filter of type RPF P01 as a laboratory and pilot filter for test series and small-volume production with an active filter surface of 0.17 m².

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