Re-use of vacuum and vent system condensate

When Ghubrah MSF Unit no. 2 was commissioned in 1982, it was found that condensate from inter and after condensers was not suitable for boiler feed water as it contains CO2. This study discusses the modification carried out to re-use this condensate by connecting it to the last stage distillate tray box. All other evaporators were modified in the same way after confirming that ammonia and hydrazine levels were within the acceptable limits. This paper also discusses the proposal for modification to direct vent condenser condensate to brine recycle pump suction or last stage flash chamber, in parallel with the existing line to the last stage distillate tray box. Such an arrangement is necessary to avoid contamination of the distillate in case of tube leak in the vent condenser.

1. The ejector condensate water is not suitable for boiler feed as it contains dissolved carbon dioxide gas. 2. The ejector condensate ammonia content does not exceed the allowable limit and it can be utilized by adding it to the distillate produced. 3. The ammonia content in the ejector condensate can be continuously monitored and diverted to waste in case it exceeds the allowable limit. 4. The vent condenser condensate can be directed to the last stage brine, in case of tube leakage to avoid shutdown of the plant. 5. These modifications can be adopted in any future design.