A miller’s tale

Claude Lefebvre, Frewitt, looks at how production bottlenecks with the milling of solids and difficult-to-process API products can be overcome easily and economically.

A customer of Frewitt was confronted with a manufacturing bottleneck in processing solids and this became a major obstacle to achieve the production capacity needed. The situation occurred at pharmaceutical manufacturer Sanovel.

Sanovel manufactures final (oral solid dosage) OSD forms of anti-diabetic drugs formulated with metformin as one of the active ingredient. The Sanovel manufacturing site in Istanbul receives metformin packaged in 25-80 kg bags which, due to the hygroscopic properties of the product, become hard solid blocks during transport and storage. For the metformin to be processed, the blocks need to go through a time consuming grinding step which disagglomerates the product into a fine powder of 200-300µm.

Requiring several hours to process a 275 kg batch in the high shear mixer, this dissaglomeration step was clearly a bottleneck of the whole wet granulation process for Sanovel. A sound technical solution to that issue would shorten the cycle of the high-shear mixer allowing a balanced process flow between all components of the whole wet granulation process and as a result substantial gains in terms of global manufacturing capacity.  

Jürgen Abel made an interesting comparison in his article about flexible production: "The bottleneck can be compared to the weakest link in a chain that breaks if the load is too great." Sanovel's weakest link in this case was processing metformin using the time-consuming disagglomeration in the high-speed mixer. Production throughput through the weakest link had to be significantly increased in order to increase overall system performance.

Metformin blocks are manually charged to a high-shear mixer, initially dissaglomerated to 250 micron powder before being processed in a wet granulation suite.

Back in 2011, the dissaglomation of a 275 kg metformin batch was a time-consuming step taking several hours. Sanovel's target was to reduce this to 20 minutes.

To find a solution to this challenge, Frewitt, a long-time partner to Sanovel, was contacted so as to benefit from the expertise and years of experience with milling systems. 

Since Frewitt had already dealt with the problem with other customers, it didn't have to reinvent the wheel for Sanovel. The solution was readily available: the DelumpWitt.

Compared with the conventional approach, which consists of a two-step process lump breaker and a mill the DelumpWitt is is a one process step breaking big lumps and fine milling them to target particle size. This integration into one system also means low height, low weight and small footprint.

The DelumpWitt consists of a conical feed funnel for product blocks up to a size of 60 x 30 x 20cm, a crusher and a conical sieve mill which can be used with different type of sieves or rasps for fine grinding of the product. The rotor and sieve can be easily changed and cleaned.

Installed at Sanovel, the DelumpWitt has since totally achieved its objectives: Metformin blocks are manually charged to the feeding hopper, pre-broken, and milled to the final particle size of 250µm. A batch of 275kg today is disagglomerated in 10 minutes, crushed and processed to a fine, free-flowing powder easily conveyed by vacuum to a high-speed mixer. From there the product is ready for processing and transfers to downstream operations of the wet granulation suite. No longer does it takes several hours to dissaglomerate. Today, the high-shear mixer can deliver its full capacity.

Ersin Ünal, Sanovel's production equipment eaintenance Executive, said: "Our collaboration with Frewitt provided the sound solution to our bottleneck challenge. The DelumpWitt gives us the manufacturing flexibility and capacity increase paramount to our success.”