FRP failure in Nitration process

[Leon87]

Dear all,
we select FRP equipment working in nitration process, and some failure occured during operation, especially for flange face and agitator part.so, does anyone have relative practical experience about this kind of equipment in nitration process?
is it necessay to update materials to replace FRP, or maybe much more focusing on FRP fabrication and operation process?
photo shows detail information in flange face.
Thank you.

 

[Leon87]

sorry guys, it is glass lined equipment.

 

[AkhilMetallurgy]

Corrosion in nitration plants is complex as it depends strongly on Nitric Acid concentration, temperature (sharp rise in corrosion above 20 degrees C), purity of Nitric Acid (traces of Nitrous and other oxides of Nitrogen are very corrosive), and alloy composition. For pure nitric acid very pure 99.95 % aluminum is good but expensive, not readily available and mechanically very weak. There are also some proprietary high Silicon alloy steels for it. AISI 304L stainless steel is alright for below 20 degree C and below 0.02% nitrous oxide concentration.

 

[StoneCold]

Leon87
A lot of the time glass spalling has to do with stress to the nozzles. Over torqueing the bolts or incorrect gasket choice. Heavy agitator loads can cause nozzle movement and that can break the nozzles.
Chemsoft or Teflon Envelope gaskets seal well with minimal bolt toque required.

 

[moltenmetal]

Glass is not corroded by nitration acid to my knowledge. You are likely looking at mechanical/thermal shock damage as noted by StoneCold.