Q & A > Question Details
Recycle gas compressor of CRU had ammonium chloride salt deposition in its impeller vanes during regeneration activities. Can we wash the rotor with DM water or steam condensate without opening the machine. If yes, can you suggest some guidelines?

30/09/2017 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
There are specific procedures to avoid ammonium chloride slippage to compressor.
Compressor vendors provide possibilities and methods to clean off line or on line.
26/09/2017 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
The unit can be modified to allow insitu cleaning and inspection to take place and the fins safely cleaned free from fouling without profiling the blades as experienced when using aluminium oxide blasting
06/12/2007 A: Roger Haglund, Eprom, r_haglund44@hotmail.com
Under the assumption you have a variable speed drive you can perform a condensate wash at low speed. I have seen such a procedure but never performed such a wash myself. If I recall correctly it is based on time and/or appearance of the water, i.e. until clean water has been seen with some extra time to assure cleanliness.
The compressor manufacturer has to approve the procedure so there is no risk for damage to the seal etc.
Consult UOP; I think they might have a generic procedure available.
06/09/2007 A: Andrew Vieler, Simulation Engineering NL bv, avieler@simeng.nl
I have done some further thinking and investigation. My original hypothesis is almost certainly incorrect. My apologies. It seems to me that the deposition is occurring as gas is compressed. Why? The partial pressures of the NH3 and HCl in the gas increase then NH4Cl forms and sublimes. I understand the HCl is generated during the CRU catalyst regeneration and that this is probably unavoidable. NH3 is also present and/or is being formed. Is this avoidable? Can these species be removed from the gas stream before compression? Washing with water?......
06/09/2007 A: Andrew Vieler, Simulation Engineering NL bv, avieler@simeng.nl
I recall a case of an offshore gas compressor getting salt deposits on the vanes - turned out to be from poor KO and droplets of salty water getting through then vaporising within the compressor. It was washed off then, in addition to reducing the KO problem, they used anti-caking agent (as used in table salt) to stop crystallization on the vanes.
Seems to me that ammonium chloride is entering in water droplets in your case so a similar cause. Be wary - dilute NH4Cl solutions are acidic (pH < 5.5) and become more acidic with increasing concentration. Another possible route: I am not totally familiar with the sublimation phase diagram of ammonium chloride but it may be forming directly from the vapour phase. This is a nastier problem as NH4Cl can sublimate in many places. The source of the NH4Cl should be identified.
04/09/2007 A: Hermann Kempen, Kurita Europe GmbH, kempen@kurita.de
Ammonim chloride salts are highly soluble in water or steam condensate, but the corrosion potential will increase and the ammonium chloride salts can deposit again. By using ACF technology the ammonia will be replaced and the formed salts are liquid salts with a neutral pH. There is no fouling tendency and the corrosion potential is very low. The ACF product can also be dosed during normal process operation if the compressor vibrations increase. This is a very interesting alternative to throughput reduction, if the compressor vibration reaches a defined level. By using an injection quill with a nozzle the ACF product can be dosed together with hydrogen into the compressor feed line. The ACF will remove the ammonium salts, which results in reduced compressor vibrations. ......