Refinery Process Pipe Carbon Deposits - Restrictions to Flow

[Flamefront]

Gentlemen

I'm new to the industry and working on a petroleum process system where I've been asked to upgrade the alloy of some 4" ID pipes to prevent "carbon fiber" growth, which occurs in the section seeing over 500C. The carbon fibers grow at Fe sites and end up restricting the flow through the pipe.

How big of an issue is this in refineries? How often are plants shut down to pig or remove such deposits? I've been told that this plant shuts down every 18 months to remove these fibers, and I've been asked to find a better alloy for the pipe. Currently they are using 316 SS.

Thx for any comments on the problem and any alloy or coating suggestions. I'm curious about how much revenue is being lost due to this problem in the industry ...so I can justify a possibly expensive solution.

 

[unclesyd]

You might want to take a look at this process.

http://www.sub-one.com/index.html

 

[0707]

“Carbon fiber” growth or coke is common in crude distillation heaters, vacuum heaters, cocker heaters, visbreak heaters and in heavy residuum heat exchangers at high temperatures. Depending on process condition operations a vacuum heater is common to be stopped every 18-month, a visbreak heater 9 to 12 month, a cocker up to 6 month and a distillation heater every four years. These tube heaters material is normally 9 Chromium 1 Molybdenum. Colorizing treatments conducted at 1560ºF to 1870ºF for approximately 10 hours after the base metal is packed in Fe-Al alloy powder or Al powder with a small amount of homogenous compound seem to be benefic to avoid scale formation and accordingly the frequencies of decoking can be reduced.

Luis Marques

 

[unclesyd]

In addition to the post by 0707 here is a company that does Aluminum Calorizing. Another term used is Aluminizing.


ttp://q-c-inc.com/index.php?option=com_frontpage&Itemid=1

 

[JLSeagull]

I don't know what coating solutions may be available for 4 NPS piping. Coking can be reduced in tubing with smoother walls and silicon based coating. The examples in the analysis instrumentation world include coatings from Restek. According to Restek, carbon deposits are catalyzed by nickel, sulfur and carbon in steel lattice. Silcosteel-AC prevents the coke or soot from sticking. However I think that this process applies to smaller parts like injection valves instead of lined piping. You may want to web search for silicon coatings. Consider contacting the Restek Performance Coatings group. I would expect contact information on their web site.

 

[DBenson78]

With regard to how much revenue is being lost in the industry you may want to contact Tracerco as they carry out pipe scanning to determine deposits in pipelines, the link attached describes a scan they have done for carbon lay down

http://www.tracerco.com/pdf/Scan Pipe Study.pdf

They may be able to give you a "feel" for the number of issues they have been involved with

 

[Flamefront]

Thanks, DBenson78, that's a great lead to help me quantify the problem in the field. I appreciate your sending it along...

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