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What should be the design pressure for wash water system in air cooled exchanger in atmospheric distillation unit? Is it mandatory to apply wash water in spray form? It will be helpful to if anyone provide reference about the spray nozzle for this application.
 
Answers
11/08/2015 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Purpose wash water injection is washing of salt deposits in the overhead section equipment (piping / exchanger tubes etc.,). For best results the wash water must cover maximum surface area of contact. spray nozzles are a must to achieve this. Spray nozzles details can be obtained from various column internals manufacturers for selecting site specific requirements.
14/01/2015 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
Dependent on whether fins are aluminium or steel and what the fouling characteristics are.
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14/01/2015 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
There are several designs of the “quill” being used today. The flow should be in the direction of the oil flow. Corrosion experts recommend an injection point at every inlet nozzle of the air cooler, not at headers or sub-headers. Design pressure of the pipe and fittings should be the pump shutoff pressure of the water supply, at normal suction pressure.
14/01/2015 A: Sam Lordo, Nalco Company, salordo@comcast.net
The design pressure will based on the pressure need to get the flow to the injection point and into the line plus that need for the spray nozzle so it operates properly. i would recommend you work with the nozzle designer, someone like spray systems (or equivalent). They have the design capability to help you in the selection of the proper size spray nozzle.
Yes you really need a properly design spray nozzle to get the distribution and effective washing of the hydrocarbon you need. For finfans you may need injection into each finfan bank inlet pipe