Wash water for CDU OVHD AFC

[canhnm]

Hi everyone
My refinery is using spray nozzle (full cone nozzle, 45deg, flow rate 1000L/h at dP=2 bar) to spray water for CDU OVHD AFC. There is a phenomenon of corrosion inside the tubes at upper rows (7 rows for the 1st pass and one row for the 2nd pass. Some opinions said that due to high flow rate at low dP, then the water droplet size is too big. As a reult, the water distribution is not proper, the heavy water droplet will settle down leading to less wash water supply for upper row of tube.
I know that some refineries are using Quill nozzle instead of spray nozzles for the same service. I think that the water droplet size of quill nozzle may be much bigger than by spray nozzles.
Could you share the design of your wash water system for CDU OVHD AFC?
Thanks and best regards

 

[georgeverghese]

Suspect this common problem in fin fan ovhd condensors is in part also caused by poor air flow at the upper rows of the fintube bank. Also air flowing over the upper tubes is higher than that over the lower tube rows. Poor quality fins on tubes may also have corroded leading to higher pressure drop and lower air throughput from fans below. Resulting higher tube operating temps in these upper rows leading to accelerated corrosion. Wider tube pitch / more air flow will result in better air flow distribution over the entire tube bank.