January 14, 2019

Production of pharmaceutical substances (APIs) – New approaches for the removal of catalysts from API suspensions

Extensive lab tests

BHS experts carry out extensive laboratory trials

Not only has the pharmaceutical industry seen significant growth over the last two decades, it has also changed considerably. This is particularly the case for safety measures in the production of pharmaceutical substances (so-called APIs – Active Pharmaceutical Ingredients). This also applies to the removal of catalysts from API suspensions in particular, a processing step that has a direct impact on the quality of pharmaceutical products. BHS-Sonthofen, a leading expert for the separation of solids from liquids, supports customers from the pharmaceutical industry in using new filtration solutions that boast improved efficiency and reduce environmental impacts in the production of active ingredients.

Catalysts are commonly used in the production of APIs to trigger, accelerate or control reactions. Once the active pharmaceutical ingredient has been synthesized, these catalysts must be removed from the API suspension. Manual plate filters, filter presses, bag filters, cartridge filters and other conventional filters are the technical solutions most commonly used for this task. These systems require not only manual cleaning and emptying between batches or jobs, but they also result in higher personnel, maintenance and disposal expenditures. To make things worse, employees and the environment are exposed to toxic and hazardous solvents and solids as well as contaminated filter cloths, filter bags and filter cartridges.

Many pharmaceutical companies are thus looking for new technological approaches to make the filtration of API suspensions more efficient and also safer. “There actually are real alternatives to conventional filters. And they are already being used with success by an increasing number of customers in the chemical and pharmaceutical industry,” says Detlef Steidl, Director of Sales Filtration Technology at BHS-Sonthofen. “These technologies are particularly suitable for use in pharmaceutical production plants. As a leading company in the separation of solids and liquids, we actively support our customers in selecting and implementing these solutions, both in existing and new plants for the production of APIs.”

Candle and pressure plate filters optimize the API filtration process

New, alternative solutions for clarifying API suspensions are mostly based on candle and pressure plate filters, which is something the BHS filtration experts are particularly versed at. Both solutions have a lot in common: They are pressure filtration systems run in batches, and they are used in applications where liquids must be removed or solids recovered (e.g., catalysts) from liquids with a low ratio of solids.

“Most importantly, both solutions have proven to be extremely reliable and also happen to be a more efficient alternative compared to using manual and conventional filters,” Steidl points out. “They offer higher filtration quality and better yield with fully automatic and self-contained processes. That makes them a safe investment over the long term. And even though the acquisition costs are higher compared with manual plants, they offer a more reliable, efficient and optimized process while at the same time reducing the risk to personnel and the environment. The ongoing operating costs are also much lower, so that the fully automatic filtration systems make economical sense after a very short time of operation.”

Structure of the filter cake is decisive for selecting suitable filtration technology

The performance of the two solutions is comparable. The main difference lies in the technology: Candle filters have vertical filters, while pressure plate filter systems feature horizontal filter elements. Which of the two technological approaches is better for the respective application depends largely on the composition of the filtration cake: Filter cakes that remain stable when arranged vertically are compatible with candle filters, while filter cakes that remain stable horizontally work better with pressure plate filters. Pressure plate filters are best suited to the processing of very dense or very loose filter cakes, for example. Even if the cake height tends to be higher (> 20 mm), horizontal plate filters are the better choice particularly for heavy solids.

Candle and pressure plate filtration can remove particles with a size of 1-3 μm and enables precoat filtering. In many applications, candle filters can also remove finer particles up to 0.5 μm. Both systems use synthetic filter media. Pressure plate filters can also be used for metallic filter media, such as for high-temperature applications (above 200 °C) or if steaming is required.

Clean-in-Place (CIP) operation can be carried out similarly with both systems. The container is filled with cleaning fluid, which circulates in the system while gas is introduced in the opposite direction. This creates a turbulent mixture with a quasi-ultrasonic cleaning effect. Pressure plate filters are easier to clean by vibrating the plates, thus reducing manual labor to a minimum.

Extensive laboratory trials for optimal results

To ensure that the new filtration technologies lead to optimal results, the experts at BHS leave nothing to chance. They perform extensive laboratory testing to give customers a solid foundation upon which they can base their decisions. The tests examine the filter media, operating pressure and cake thickness in order to arrive at the best possible design and size of the filtration system. A specific solution is only recommended based on these trials. “We consider ourselves specialists for solid-liquid separation, and we don’t limit our expertise to just one particular technology,” says Steidl. “This is why we meticulously examine all alternatives before we select the best solution for the customer’s specific application. We know empirically that the results of these trials are very accurate and realistic, and that means we don’t make any promises that we can’t keep.”

Filter cake in the candle filter

Filter cakes that remain stable when arranged vertically are compatible with candle filters

Solid material on the filter medium

The solid matter accumulates as a filter cake on the surface of the filter medium due to the pressure difference applied during the filtration cycle.

Compact candle filter unit

The candle filter is a compact unit, operates fully automatically and allows high throughput rates

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