How to Avoid the Costly Effects of Oil Contamination in Ammonia Dissociators

Posted by Tom McDevitt on Feb 15, 2016 8:00:00 AM

The Rose Corporation recommends using only Metallurgical grade NH3 in our Drever Ammonia Dissociators.  There are numerous documented cases over the years where non-metallurgical grade ammonia has been used, resulting in premature failure of the dissociator. More often than not, the cause is oil contamination. Often, cost reduction is the root-cause of lower grade ammonia, particularly agricultural grade ammonia, being used in atmosphere generation equipment. 

Typically, the ammonia dissociator works within performance parameters for 12 to 24 months; however flow and backpressure gradually decrease, eventually resulting in equipment failure.  When disconnecting the ammonia inlet pipe from the catalyst chamber, one can observe the interior diameter of the pipe is restricted to less than 1/8” with a dark gray, powder-like substance.  Dissection of the catalyst chamber reveals contamination of internal components with the same gray substance.  While this material is hard, it can be cut with a pocketknife.  The material is non-magnetic, slippery to the touch, and similar to talcum powder.

Here is an example of an uncontaminated partition sleeve:


Another indication of oil contamination is degradation of the alloy inlet pipe within the temperature gradient zone extending from the bottom of the catalyst chamber head to several inches down into the floor brickwork.  The attack manifests as a thinning of the pipe wall to near paper-thin thickness; a reaction commonly caused by sulfur attack on the inconel material.

Here is an example of an oil contaminated partition sleeve:


Such cases are the reason The Rose Corporation continues to recommend using only Metallurgical grade NH3 and checking periodically for contaminated ammonia supply to avoid unwanted production outages due to dissociator failures. The Rose Corporation recommends its customers use only personnel or contractors certified in safe handling practices for ammonia.

Here is an example of an oil contaminated alloy tube:


The best place to drain off ammonia for testing is at the lowest point in the system, and the best time to obtain the sample is immediately following an ammonia delivery.  Catch the liquid in a Pyrex beaker, allowing the liquid to drain slowly until seeing water-clear liquid.  The use of proper safety equipment during this process is imperative.  Your service provider can test this dirty liquid for oil contamination.  One customer operating a Drever ammonia dissociator performs this test after every ammonia delivery. He reports that quite often he encounters a lot of rusty, oily “muck” before seeing clear ammonia liquid.  This customer states routine elimination of these contaminants extended the life of the catalyst chamber and affected piping.

The Rose Corporation’s Industrial Furnace division manufactures for customers world-wide all types and configurations of industrial furnaces such as batch type reheat and forging, tip-up, roller hearth, bell, car-bottom, vacuum, electric arc, and many more for both atmosphere and non-atmosphere, batch and continuous applications.  The Rose Corporation has manufactured industrial furnaces under both our RoseTM  and DreverTM  furnace brands, as well as manufacturing customized furnaces to our customer-supplied design.  We also manufacture dissociative, atmosphere generating equipment. 

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