Why the Need for Evaporation
Multiple Effect Evaporator System
Types of Evaporation System
Evaporators used in wastewater primarily fall in below categories
A)Depending on the type of Vapour compression
1)Thermo Vapour Recompression based Evaporators (TVR based Evaporator)
2)Mechanical Vapour Recompression based Evaporators (MVR based Evaporator)
B)Depending on Type of Liquid Flow
1) Forced Circulation Evaporators – Used in majority of the cases
2) Falling Film Evaporators – Used Rarely
What is Vapour Recompression
Vapour Recompression can be done using –
1) Thermal Energy using high pressure Boiler steam (Motive Steam) or
2) Mechanical energy of reciprocating / lobe compressors
A) Thermo Vapour Recompression (TVR) – When Thermal energy is used for vapour compression it is called Thermo Vapour Recompression (TVR) and the evaporator systems are called TVR based evaporators.
B) Mechanical Vapour Recompression (MVR) – When mechanical energy of reciprocating / lobe compressors is used for vapour compression it is called Mechanical Vapour Recompression (MVR) and the evaporator systems are called MVR based evaporators.
Thermo Vapor Recompression Based Evaporator
Please follow the process flow diagram and the description mentioned for Multiple Effect Evaporator System above.
Mechanical Vapour Recompression Based Evaporators
Comparison Between TVR and MVR
Advantages of MVRE over TVR
Comparison of Forced and Falling Film Evaporators
The Evaporator system can be Forced Circulation type or Falling Film type. In the Forced Circulation Evaporators the effluent is pumped through the calendria at a high velocity by the recirculation pump. In the Falling Film Type the liquid trickles from top to bottom forming a thin film along the inside wall of the tube. Generally for handling of effluents Forced Circulation Type evaporators are preferred as they are much more resistant to scaling and salting in the inside of the tubes than falling film type.
Type of Heating Medium
Below are frequently and easily available heating mediums
Comparison for Steam and Thermic Fluid
Steam, Hot water and Thermic Fluid can be used as the heating medium for evaporators. Steam is preferably used as a heat source for evaporation because it is clean fluid and comparatively the most economical.
Zero Liquid Discharge
Goldfinch has designed and executed many Zero Liquid discharge (ZLD) projects for various kinds of challenging effluents.
The recycled wastewater is being regularly used as cooling tower make up, vessel washings and sometimes as process water also. We have also installation where the recycled wastewater is used as Boiler feed.
The typical ZLD schemes comprise of Bio – ETP followed by RO. RO reject is evaporated in evaporator. But as in case of high TDS effluents, the ZLD schemes comprise of Multiple Effect Evaporator upfirst. The condensate of MEE is then treated in Bio – ETP followed by RO. The RO reject is then recycled back to MEE in closed loop.
Goldfinch has successfully designed and executed ZLD projects for speciality chemicals, API, paint effluents etc.