Q & A > Question Details
We are having some fouling in our packinox plate welded heat exchanger. Are there ways to do the cleaning without taking any shutdown?
Also what could be the fouling materials ?
The Heat exchanger plates are stainless steel s321 adn the feed is mainly c8 aromatics with some c7 and c9
gas is also used in the exchanger mainly containing hydrogen and ethane
The temps are 105 and 334 for cold fluid and 120 and 384 for hot side
 
Answers
04/10/2018 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
I have seen three primary foulants in this service on the reactor effluent side of the exchanger. You can get catalyst fines if screens/filters fail or don't work properly. You can form polymer that comes out at the colder end of the exchanger, and you can get ammonium chloride at the cold end of the exchanger if your naphtha hydrotreater is not getting N levels in the feed low enough. The latter two issues often go hand in hand, especially when there is coker naphtha in the feed. Increased end point on the naphtha increases the N content of the feed and can carry in some nitrogen compounds that are more difficult to hydrotreat. The higher EP material is also more likely to form a high boiling polymer. If you get multiple fouling mechanisms going on at the same time, it can be very difficult to effectively clean the exchanger.
30/07/2018 A: Jesus Perez, Alfa Laval Packinox, jesus.perez@alfalaval.com
It's possible to perform an online cleaning without any shutdown by means of a dew point shift wash on the effluent side where the last reactor temperature is lowered thus the physical dew point in the bundle shifts to a higher elevation dissolving some foulants. This is also a common practice on shell and tube exchangers.
Per the temperature profile and and feed composition you mention, this seems to be an aromatics plant in which case the fouling occurs mostly on the feed side after a long run.
Alfa Laval Packinox has developed a controlled combustion procedure to clean the Packinox exchanger where most foulants are burned over a long period of time at low temperature and low oxygen content. We have a list of about 10 customers who have performed this procedure with great results. References exist in all continents.
24/07/2018 A: NS Murthy, Suez, murthy.ns.ext@suez.com
Can you pl provide the following information?
1. Extent of fouling as seen by drop in pr and drop in Ud.
2. Did you ever check for impurities in the feed (such as olefins & dienes; heavy boilers including Px adsorbents, if any; any traces of oxygen in case mixed xylene is brought from other sites for recovery of Para Xylene; Chloride spill from u/s reformer; etc.)
3. Any analysis of foulant including LOI, C/H/N/O, Ash, etc.
23/07/2018 A: Muhammad Akhtar, Orpic, mbadgk@gmail.com
If the pressure drop has increased from effluent side than we can carry out dew point cleaning of the exchanger. This will help in partial cleaning of effluent side by dissolving deposited gums on the plate. This activity will require reduction in reactor temperature without cutting out the feed. We have performed it twice and saw effective results.
23/07/2018 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
If it’s hard fouling it cannot be removed. Chem cleaning needs a passage way , chemicals still won’t clean it if you have passage through hydrocarbon scale.
PCA, PNA gummy coke like scale are easy to remove from the tube and shell side of a floating head designed exchanger mechanically than a packinox.
If you know it will never foul with coke and tenacious hard stuff buy a packinox, if not - buy a shell and tube design and we will show you how to clean and inspect it regardless of fouling - guaranteed!!