(87b) Mol. Sieve Dehydration Unit Potential Problems for LNG Plant

Mol. Sieve Dehydration
unit potential problems for LNG plant.

AICHE 2014 spring meeting

By J C Kuo and Dr. K H Wang.

University of Houston      

Abstract

Many dehydration units in based
load plant have not been able to operate per design and premature moisture
breakthrough has been occurring. From RCA (Root Cause Analysis) indicate the
followings potential issues 

1.    
Regeneration Gas Flow

The design regeneration gas
flow rate is very critical.

2.    
Retrograde Condensation

Retrograde condensation can
impact the performance of numerous operations including amine absorption,
molecular sieve dehydration, and mercury removal.

Liquid hydrocarbons in the
amine unit can cause foaming and lead to reduced production. Liquid
hydrocarbons can damage the sieve in the dehydration beds resulting in poor
performance and lower production.

3.    
Liquid Carryover

The design of inlet separator
need to offer sufficient separation. Otherwise it carries liquid over with the
gas due to the high operating pressures and low surface tension.

4.   
Regeneration Gas temperature.

Some base load plant could use
315C high temperature in order to minimize the regeneration gas flow. However
for some impurities include heavy hydrocarbon, methanol or Amine solution,
lower temperature at 240 C ranges may be required.