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Morpholine Poisioning Clauss Claus Catalyst .pdf



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Morpholine Poisoning of Claus Catalyst
in Sulphur Recovery Units
Otis P. Armstrong P.E.
Process Engineer
Saudi Aramco
Abqaiq Plant Operations Engineering
Presented: 1st International Conference on Chemistry in Industry,
Bahrain 1992
pp 998-1018

CASE HISTORY
What is Morpholine?
degradation product of BHEEU conversion to DGA, always
present in small amounts in DGA type Amine Units,
minimize by keeping correct reclaimer Temperature

What are impacts on Sulfur Plant Operations?
Morpholine Carryover is typically slow & continuous
w/ little impact on operation of sulfur plant

What happened?
A DGA reclaimer tube leak dumped superheated steam into the
reclaimer & increased Morpholine production with a drastic
decrease in SRU recovery and increased DGA makeup

Sweet gas out
Offgas

Acid gas

Wash H2O
23
22
Contactor

Sp

19

21

Stripper

C

1

D

Sp
Separator Solids

S
5
2

3
2

X reflux

21

Drum, flash

Typical DGA Unit
Acid Gas goes to
SRU Gas Scrubber

1

Reclaimer

R

Table 1 shows vapor pressure
of Morpholine, which is about ½
that of water. Thus where water
goes, Morpholine goes. DGA has
only 1/100 of water and very little
is lost in well rectified units.

The normal concentration of
amine in the acid gas scrubber
is typically less than 0.20% by
weight. During this incident, the
concentration was 10-20 times
normal levels in SRU-1, which
is adjacent to the GT unit which
developed reclaimer tube leak

Table 1
vap
press mmHg
T, F
Morph
H20
DGA
90.00
20.00
36.00
0.35
120.00
40.00
88.00
0.61
212.00
310.00
750.00
2.30
Table 2
Total Amine in Acid Gas Scrubber %
Date Train 1
Train 2
Train 3
16-Sep 1.90
0.30
0.30
17-Sep 0.05
0.07
0.05
21-Sep <0.10
0.10
<0.10
29-Sep 1.10
0.15
<0.10
6-Oct 0.02
0.04
0.04

98

The rapid decline in recovery
after 13Sept.triggered this study.
A regression analysis was
made to determine if
operating parameters can
explain the decrease in %Rec.
But only 20% of the changes
in recovery could be explained
by operating parameters. The
main external effect was amine
in scrubber water.

Train 1 Recovery B4 & after incident
Amine in Scrubber H2O T1 & T2

0.15

96
0.30
94

0.05

92

SRU-T1 measured

90
88

0.10
T1 calc by T2 regr. eq.
1.10

%Recovery

Claus Unit 1 Recovery
B4 & after amine carryover.

0.09
1.90

86

0.05
Sept 1991

84
6

11

16

21

26

The primary increase of amine in
scrubber water is thought to be
Morpholine, due to the high vapor
pressure of Morpholine.

31

Misc DGA
Reclaimer
Dumps

Amine Make-up Sinks

The main source of Amine Loss
is Morpholine in a DGA unit 70%

Morpholine
Production
T&I
Shutdowns

The main egress of Morph.
is to the SRU Process, 73%
Morpholine Loss Routes

2/3 of egress is removed in
amine scrubber H2O, for
normal operation
upsets send more to SRU
Acid Gas Scrubber

Lo-Psi Fuel
Contactor
off gas

AcidGas
Scrubber

AcidGas to
SRU

Process Study Results
•Morpholine Lost is DGA Lost
•Morpholine losses go mainly to the SRU
•Morpholine deactivates Alumina catalyst

Conclusions
Abnormal Conditions Cause Excessive
Morpholine Carryover, such as:




excess generation in reclaimer
stripper overhead condenser failure
boilouts during unit shutdowns

Deactivation is thought to be from 2 effects
1. Temporary deactivation of active site by ammonia
2. Longer Term deactivation by coke formation
3. Normal Morpholine carryover is acceptable

Recommendations
1. Minimize Morpholine Production in reclaimer
2. Monitor Amine in Acid Gas Scrubber of SRU
3. Use Temperature Alarms on Amine Reclaimer

Appreciation is given to Saudi Arabian
Ministry of Mineral & Petroleum Resources
for permission to publish this work


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