Gea supplies Bracco with falling film evaporator for the concentration of contrast media

Caption: A 3D graphic of the Gea evaporator

Italian company Bracco in Torviscosa, located in the Udine Province, has placed an order with Gea for the supply of a falling film evaporator. This plant is a key component in the concentration of liquids and solutions in the manufacturing process of medical contrast media. The best-known products among the various contrast media are Iomeprol or Iodoftal. The evaporator Bracco ordered is specifically designed for use in the production of Iodoftal. A decisive factor in this order were the laboratory and pilot tests which took place in Gea’s test center in Karlsruhe in January and February of this year. Using the results, the system could then be individually tailored to Bracco’s requirements. The plant concentrates a solution, known as mother liquor, from 10% dry substance to 23-25% dry substance and has an evaporation capacity of approx. 3000 kg/h. Due to the use of a mechanical compressor for heat recovery, the plant is highly energy-efficient.

Bracco is one of the world's leading companies for diagnostic imaging. Their primary products include: contrast agents and medical substances to improve the diagnostic accuracy of biomedical imaging. Contrast media are routinely and widely used in diagnostic imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), ultrasound and nuclear medicine.

The liquid to be concentrated is fed at the top of the heating pipes via a unique distribution system and runs down the inner walls as a thin film. Due to the external heating of the tubes, the liquid film begins to boil and partially evaporates. The downward movement initially generated by gravity is then increasingly supported by the thrust effect of the vapors, which are also flowing downwards. In the lower part of the evaporator and the downstream centrifugal separator, residual liquid and vapors are separated from each other. For the efficient functioning of the falling film evaporator it is critical that the entire heating surface, particularly in the lower area, is evenly and sufficiently wetted with liquid. If this is not the case, dry spots will form, leading to severe incrustation.

The selection of a suitable distribution device to enable the liquid to be concentrated in the head of the evaporator body is of great importance for complete coverage; coverage can be increased by extending the heating tubes, subdividing the evaporator several times or recirculating the product. Falling film evaporators can be heated directly with steam or hot water and designed as single or multi-stage units. Heating with support from thermal and/or mechanical vapor compressors for heat recovery can deliver significant energy-savings.