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Submitted Chris Haslego, Nov 21 2011 11:21 AM | Last updated Nov 21 2011 01:29 PM




Category: Refining
Question: How can I clean a welded plate heat exchanger and prevent future problems in our reforming unit?
Keywords: welded,plate,heat,exchanger,plugging,increased,pressure,drop,cleaning,in,place,reforming,unit
Answer: BACKGROUNDIn a catalytic reforming unit, we are experiencing an increased pressure drop across a welded plate heat exchanger.ANSWERYou have essentially two options:1. Contact the manufacturer and see if they have a service department that can perform a CIP (Cleaning in Place). This is the only way to clean a truly welded plate unit.2. Buy a new unitOther suggestions would be the following: During a shutdown, check the ports to see if there is obvious plugging in the ports. If not, then the plugging is probably equally distributed in the channels. I'm not sure what kind of plugging you'd be getting in a gas plant, but if there is any risk of suspended solids entering this exchanger, then you need to filter the streams before they enter the unit. You'll need to know what the free channel spacing is of the unit. Then, filter any particles over 75% of the free channel spacing.FOLLOW-UPIf you are running a Catalytic Reformer plant I'm speculating that you may have entrained catalyst fines over into the effluent product stream coming out of the reformer. I know I'm speculating, but somehow you have plugged the exchanger and this can only be a hard, unsoluable solid if the exchanger is in hot service. I also suspect the plug is not going to be capable of being dissolved and, consequently, the exchanger must be sacrificed. Presumably, the exchanger came as original equipment with the reformer plant and was designed to work well. If the process design allows for the possible entrainment of solids, a protective filtering system must have been designed into the plant. If the filtering system exists upstream of the plate exchanger, it must have failed or it might have been by-passed for some reason. Regardless, the result is that you now face an increased pressure drop across the exchanger that is subject to getting worse and shutting you down. If the exchanger is running hot and you can bypass it, I would try to inspect it while it is off the line. There is a chance that you could discover the tell-tale signs of solid plugging in the gas inlet nozzle area. If you do not find the reason for the plugging, you still wind up with same bad news: the exchanger is probably not salvageable because of the prohibitive labor and repair costs. The reason for trying to find the cause is to design against the effect taking place again in the future.I suspect you would be well advised to prepare for an upcoming exchanger replacement and eventual scraping of the existing unit. The harm has already been done to a unit that simply is not designed (nor expected) to tolerate solids' inclusion in the process stream. You should identify the source of the plugging and take positive steps to mitigate it in future operations. A plate heat exchanger is very economically and size efficient and my hunch is that you would be better off with a similar replacement instead of a shell and tube design. However, you must protect the plate exchanger from solids in the process stream. You are almost obligate to go with the welded (sealed) design because of the safety hazards involved with a gasketed plate design in this critical service. The fact that you plugged the unit is not the fault of the plate exchanger design. You should not have to tolerate solids in your reformed gas streams outside of the reformer.


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