Steam jacketed carbon steel rundown lines for molten sulfur

How effective are steam jacketed carbon steel rundown lines for molten sulfur? In particular, are there predictable failure mechanisms in the piping, either in the steam side or the sulfur side? Is there assumed/ measured corrosion rate? What proactive means are employed to keep the line from failing? Is there an active reliability strategy. This seems to be one of those failures whose consequence is enormous by probability is slim. 

Consider these comments from the Refining Community SulfurUnit.com forum? 

- Vaporizing Process Flow from heat tracing can lead to localized corrosion. Jacketed heat tracing can reduce heat transfer to prevent this. There is a helpful jacketed heat tracing software that can be used to calculate temperatures, steam demand, and such at https://www.thermon.com/software/default.aspx.? ?I recently used two bare 1/2″ stainless heat tracers (at the 2 and 10 o’clock positions) on a pipe header insulated with 1.5″ Calcium Silicate as the jacketed heat tracing would not provide the temperatures that I was looking for.? ? (Forum Guest)

I believe Heat tracing of pipe to be an Art.?

• Jacketed pipe and steam traced/Contro both have their place in process.?
• Jacketed pipe is a pain to repair or weld on. And then you have the issues of Valves in the system. But generally has decent heat transfer.? - Traced/Contro, if accurately engineered for optimum heat transfer can be an advantage in not having to deal with jacketed piping issues, lending itself to more flexibility. (Guest)?

In my pass life I work as a Maintenance Engineer on two sulphur units, the jacketed transfer lines were a problem. To help keep good hot steam in each section, we ran a common steam and condensate lines parallel to the sulphur line. I had good hot steam going into each section of jacketed line and had a good steam trap on each section. This keep the line hot and helped solve the problem of the steam cutting onto the inter line. (Claus Graf)

?One problem we had at the SRU I worked in was that the condensate drain lines from 3-4 jacketed sections was connected to only ONE steam trap. This arrangement would prevent some of the sections (at least 1) from draining because of the different pressure drops in the system.? ?Something to keep an eye on while building new SRU’s. (Pete Bisila)

?Speaking of new sulfur run down lines, what is considered the current best practice for long sulfur transport lines? Controtrace vs steam jacketed? How long of a run between steam supply and trap? Wireless/continuous condition monitors on steam traps? How often are the traps checked for proper operation? ?(Jeanne Rameau)

Skin effect heat tracing is very effective on long lines. No steam traps are needed, maintenance costs are low.? (Forum Guest)

I have not seen this in Refineries? It doesn’t seem like it would be cost effective to me. On the other hand, I could see it as you mentioned on a very long pipeline run, where you have no utility systems at hand? Do you know of any refineries that use this?? (Jeanne Rameau)

I have a frequently problem with sulfur rundown line. FYI: we use 2 stage reactors and 3 stage condensers so there are 3 line rundowns to seal pot and pit. We often face sulfur plugging on that sulfur rundown lines to solve that plug problem we usually open step by step every cross joint in rundown line and clean the sulfur plug. I have a few questions about rundown sulfur:? a. Actually what is your philosophy of sulfur rundown line?? b. Is there rule for rundown sulfur design? (In my plant we have 3 different layouts and no common design. One has 3 cross joints, other has 5 and 6 cross joints). ?c. Is there any relation between sulfur rundown design and the pressure system? ?d. Can I minimize the sulfur rundown length by removing 2 or 3 cross joints?? (Forum Guest)

General rules I have heard for run down lines:?1) Treat them like sewer lines, everything should flow downhill to the pit.?2) Install a cleanout/ rodding port at every change of direction. Make sure you can access all directions of the line. Minimize the number of turns in the rundown piping?We had one sulfur plant with the sulfur condenser drains on the bottom of the condenser and a horizontal rundown line coming out of a jacket pot under the condenser. The sulfur had to make two right angle turns to get into the rundown line. Worst of it was we had no way to rod directly through the two 90 degree bends. We hot tapped a new outlet into the condenser cover plate on the run and installed a new rundown line on the worst of the condensers and then replaced the rest of the cover plates with new nozzles at the next TA. Problem solved. (Peter Bisila)

Plugging off of a SRU steam jacketed sulfur rundown can be caused by a number of things. The single most common cause for plugging of the rundown lines is from a tube or tubesheet leak in the condenser. The BFW comes through from the shell side to the tube side and will freeze off the liquid sulfur in the area of where the leak is. As the leak worsens, odd behaviour is noted in the rundown lookbox which looks like slugging of the liquid sulfur. The next stage of severity will require rodding either horizontally in the rundown legs or vertically up into the belly of the condenser outlet. Eventually the problem becomes so serious that the rundown will cease to flow, the condenser will flood with liquid sulfur and then the liquid sulfur will be carried over to the next stage or case of the final condenser, it will show up as a large emissions spike from the CSEM.? Another cause of rundown plugging is from corrosion of the steam jacketing which will allow steam into the sulfur side and again will allow for solidification of the sulfur which can be rodded to keep the unit running. Eventually, the leak will worsen and the rundown line cannot be made to flow sulfur.? Another cause can be catalyst fines or a type of sulcrete which is a mixture of catalyst fines and corrosion products that can plug up the seal leg at the bottom where the dip tube ends which will stop of restrict the flow of liquid sulfur.?The final cause can be a failure in the converter grating used to support the catalyst which is allowing alumina catalyst to fall down and be swept into the condenser which then allows for the migration of the catalyst to the bottom of the dip tube.? Consultation with operations should allow for determination of which mechanism is the most likely that is causing the problems at which time a proper fix can be scheduled. (John O’Connell)

Has anyone ever seen a molten sulphur line being pigged? (Forum Guest)?

In my view,?

           A.) sulfur run down lines should be jacketed steam. One more serious thing, should not run Reactor very long on fuel gas or NG during shutdown. It may create later on coking problem in seal legs because it is very difficult to maintain stoichiometric ratio fuel: air during shutdown?

           B.) it should be 5% slope to flow sulfur (rundown line) reach to sulfur pit.?Electrical Heat tracing is a good example. (Wasiullah Khan)?     ?

Is there any possibility that molten sulfur can cause heart arrythmias or causes with muscles to spasm? (Forum Guest)?

While recovering sulfur in an SRU depends on condensation of sulfur, its unintended condensation and accumulation can present problems. The paper by Jacobs analyses areas where this may be expected and presents case histories of sulfur build-up in SRU equipment, such as waste heat boilers, reheaters, sulfur condensers and coalescers.?The risks involved in accumulation of sulfur are discussed, both for the operation of Claus plants and for the operation of SUPERCLAUS? plants, for which liquid sulfur may pose extra risks. Ways are discussed to prevent accumulation and minimize the risks? (Paul Orlowski)

For more posts, see the Refining Community SulfurUnit.com forum?     

===================================================

Noel Vicente, sulfur specialist at SulfurUnit.com, MC's the presentations and discussions at RefComm? Galveston 2017 May 10-11 and RefComm? Budapest 2017 4-5 October which apply to Sulfur Recovery Unit (SRU) as well as separate tracks for Delayed Coking (DCU), Fluid Catalytic Cracking (FCCU), and Instrumentation & Electrical (I&E) groups.

About the author: Paul Orlowski is a former Software Applications Engineer at ARCO and BP refineries. In 1998 he co-founder Coking.com Inc which has expanded into Refining Community.

Refining Community has been hosting RefComm? and other conferences for Delayed Coker, FCC, Sulfur and I&E since 2001. Refining Community also offers training courses and consulting services for greenfield and experienced producers.

Looking for more Sulfur Recovery Resources: SulfurUnit.com and Linked In Sulfur Recovery Discussion Group