The installation of 2 continuous vertical crystallisers (CVC) were completed earlier this year by Bosch Projects at Umfolozi Sugar Mill (USM). The CVC project timeline was extremely tight so as not to delay the factories crushing season start and a lot of effort went into achieving this without compromising safety or quality.
Both crystallisers comprise of 6 strakes, with each strake being split into halves to allow for ease of transport, rigging and installation. The top strake is installed first and then hoisted up to allow for the proceeding strake halves to be brought into position and welded up. Once the 2 halves are joined the new strake is welded to the strake above. This process is followed until all 6 strakes are in place.
Being a brown field installation, a lot of planning had to go into getting the strake segments rigged into position as both locations were too tight to allow crane access. The installation crew were able to use the factory structure for rigging the A CVC components into position, but with the C CVC location being outside the factory, a box structure had to be constructed around the unit to allow the installation team to rig off.
The CVCs were supplied with independent closed circuit cooling water systems comprising of 1 plate heat exchanger and 2 pumps (1 duty and 1 standby). This will allow for improved control of the massecuite cooling rate which can be adjusted depending on massecuite purities and process requirements.
Both CVCs have now been running for over 5 months and a noticeable improvement in massecuite exhaustions and tonnage per day (TPD) has been achieved. The decision to install 2 Bosch CVCs came at the perfect time as the majority of SA factories are now under pressure with the large cane crop expected this year. The additional crystallisers not only allow extra buffer capacity, but also improved recoveries which are essential for South African sugar factories to prosper, given the current local and global sugar prices.