Secondary Reformer Refractory Damage

[sahsanb]

Dear Experts,

Hope you are well. . I am writing this post to seek your expert opinion and guidance regarding a refractory issue faced recently at our site. Details are appended below.

We have a catalyst loaded vessel (secondary reformer) at our ammonia plant. This equipment is refractory lined with operating temperatures up to 1400 OF. Please see below presented equipment diagram for refractory thickness and other relevant details.

An in-service hot spot (up to 550 OC) was observed on this equipment a couple of weeks ago based on which our team decided to shut down the plant. Hot spot location has been marked on drawing for reference (see purple highlighted area). Upon inspection, condition of service side refractory above the catalyst portion near hot spot region was observed satisfactory. Shell side refractory was also observed to be in satisfactory condition. Please note that both layers of refractories above the catalyst level were replaced in year 2005. However, upon removal of catalyst, the condition of refractory just beneath the catalyst was not in satisfactory condition. This portion is highlighted by green box in below diagram. Service side refractory was observed detached from shell side refractory layer and wide cracks/ gaps were also observed in this portion (see pictures below). Shell side layer in this area was observed flaky and could be easily removed by hand. Condition of refractory below this portion (yellow highlighted) was again observed satisfactory and no major concern was recorded in this area.

We conduct thermography inspection of all refractory lined equipment at site on quarterly basis. No hot spot or any concern was reported during thermography surveys of this equipment for the past many years.

We need your expert advice regarding possible reasons for this in-service degradation of refractory layers at the catalyst region. We would also be grateful if you can shared your feedback on following few queries.

- What are the service related issues that may result in localized refractory damage?
- What are your recommendations for in-service monitoring of refractory lined equipment? Is there is any specific guideline/document w.r.t. same.
- What in your expert opinion should be the internal inspection frequency of refractory lined equipment?
- Do you have any recommendation w.r.t. maximum useful life of refractory? Do you recommend replacing the refractory after certain interval irrespective of refractory condition and/or external thermography results.
- For refractory lined equipment that are loaded with catalyst (i.e. Secondary Reformer), do you recommend removing all the catalyst to inspect its refractory internally during each internal inspection opportunity? Or do you recommend to inspect the refractory in area available for inspection and proceed for removing entire catalyst only if there is any increasing temperature trend in area under catalyst bed?
What are the service related issues that may result in localized refractory damage?

Regards,

 

[SWComposites]

a) no drawing posted
b) sounds like you need to hire an expert to examine the site in person.

 

[sahsanb]

Attaching the drawing and picture for review.

 

[Chumpes]

hello
what type of anchors were implemented ?
what were the results of mechanical testing (cold crushing test, PLC, ...) of this refractory on production mockup ?
regards

 

[Dhurjati Sen]

Check the production log for some mal-operation in the recent past.

Replace the damaged refractory with identical material and anchors. No deviation from the original is permitted.

DHURJATI SEN
Kolkata, India

 

[0707]

Have you had letly emergency shutdwons? The concrete lining above catalyst line seems to be result of several, thermal shocs, due to unexpected shut down cycles. To do periodic thermography is a correct practice. Is it your material a monolitic lining type Resco RS9?
At least this linings in refining industry are internaly inspected each five years and montorized by thermography in a contoled periodic basis.

regards

 

[sahsanb]

Dear 0707,

Yes we did have a forced shutdown a month before this observation. Plant was shutdown in a controlled manner and within pre-defined IOWs for OPS team. Our hot face refractory is rich in Alumina (~ 94%) while our insulating side refractory is quite close to Resco RS9 grade. High silica refractory cannot be installed on hot face in secondary reformer due to chemical incompatibility with steam and synthesis gas.

Refractory at hot face in highlighted region had given away as it's anchors wing nuts were broken off. Main anchors welds were in satisfactory condition and no issues were observed in their welding. Our insulating layer condition was like a mush (completely devoid of any mechanical strength and could easily peel off with hand.)