Limiting Conditions for Evaporation System
Essay by gambiosi • June 4, 2019 • Lab Report • 367 Words (2 Pages) • 709 Views
Limiting conditions for Evaporation system
- TDS:
Following are the TDS limits for the feed to an evaporation system with automatic pusher type centrifuge. This limitation is based on the market availability of minimum solid processing capabilities of pusher type centrifuge.
Capacity | TDS limit |
5-10 m3/day | >15,000 ppm |
10-20 m3/day | >10,000 ppm |
20-50 m3/day | >8,000 ppm |
50-75 m3/day | >5000 ppm |
- Hardness:
Presence of hardness causing salts contribute towards scaling of the tubes of the evaporator system which in turn will reduce the overall evaporation capacity of the system. Also, this would result in the increase of the CIP frequency.
Typically Ca2+, Mg2+, SO42-, CO32 based salts cause scaling.
Calcium scales in evaporators are mostly due to CaCO3 which is nearly insoluble in water at high pH or as co-preciptating with Na2CO3 as the double salt, prissonite which can form insoluble deposits in the heat transfer surfaces of the evaporator.
Hence, hardness should be limited to about 2000 ppm. However, the scaling can be mitigated by addition of anti-scalants (Indion 2370/ 2375) to the feed.
- Silica:
Colloidal Silica:
Presence of colloidal silica in the feed may result in Silica being carried over into the condensate which can result in scaling of the vapour piping & the condenser tubes. Hence, colloidal silica should be limited to about 50 ppm.
...
...