Q & A > Question Details
Currently, I am working on proposal of Ammonia flare system project for one of the client based in GCC. I have an experience on the HC flare system.
There are 2 flare header coming to the ammonia flare system as below.
1. PSV discharge having liquid + gas stream
2. PSV discharge having only Gas stream
The PSV discharge having liquid + gaseous stream will be transferred to the Flash tank for separation of liquid & gas stream. The separated liquid stream will be sent to ammonia storage tank & Gas stream connect with the main gas flare header & transferred to Ammonia KOD.
I have following question regarding the system, may u consider silly also
1.Why water seal drum is not considered to in this design? HC flare system have a separate KOD & water seal drum for adequate protection against flash back form the flare tip while Ammonia have only KOD integral with flare stack.
2.What is reason for providing the steam tracing to the flash tank?
 
Answers
06/12/2011 A: keith bowers, B and B Consulting, kebowers47@gmail.com
1) When liquid ammonia is discharged to a lower pressure environment (like a flare header), it will rapidly vaporize, absorbing heat from that environment. The evaporating temperature can easily drop to -40 degrees, which would freeze any water seal rapidly potentially blocking the flare system.
2) Steam tracing provides a heat source to vaporize any liquid ammonia that results in the flash tank and remains after the relieving event stops.
3) Please note the steel used in an ammonia flare system MUST be suitable for the very low temperature potential of liquid ammonia boiling at atmospheric temperature.