(AmiPur®) – Continuous Heat Stable Salts Removal from Amine ...

Amine Purification System (AmiPur®) – Continuous Heat Stable Salts Removal
from Amine Solutions
1. Introduction
Jenny Shao, Group Leader – Oil & Gas, Eco-Tec Inc. Canada
Amine scrubbing solutions are used to remove hydrogen sulfide (H 2 S) and carbon
dioxide (CO 2 ) from gas streams and LPG in many oil refineries and natural gas
conditioning plants. Due to its high selectivity to H 2 S, Methyldiethanolamine (MDEA) is
most commonly used to remove H 2 S in the presence of CO 2 from gas streams and LPG.
Amine plant operational problems, such as excessive foaming, corrosion, and capacity
reduction, are often attributed to the accumulation of amine heat stable salts. These heat
stable salts lead to costly maintenance problems such as corrosion, frequent filter
replacement, foaming in the absorber column, absorber tower plugging, heat exchanger
fouling and a reduction in the amount of amine available for gas treating.
Continuous amine purification is being increasingly recognized as the most effective
solution for HSS related problems. The benefits of continuous HSS removal go beyond
limiting the level of impurities in the amine loop. A continuous on-line purification
system helps to ensure a stable and uniform gas conditioning operation where
contaminant level in the amine solution is prevented from building up, thus minimizing
the rate of corrosion. It also ensures that amine unit operation is reliable and provides the
designed gas treating efficiency.
Developed by Eco-Tec Inc. Canada in 1998, AmiPur® (Amine Purification System) uses
anion exchange technology to continuously remove heat stable salts. Therefore, it ensures
reliable operation of amine plant.
2. AmiPur® – Heat Stable Salt Removal System
Eco-Tec AmiPur® employes its Reciprocating Flow (Recoflo TM ) ion exchange
technology, which has been extensively used since 1973 in many chemical recovery and
water treatment systems. The AmiPur®, a unique and cost effective on line amine
purification system has the following features:
• Fine particle size resins;
• Countercurrent regeneration;
• Short column heights (12 inch, 30 cm);
• Low resin loading;
• Fast flows and short cycles;
These on-line Eco-Tec Amine Purification (AmiPur®) systems are now successfully
operating in 25 petroleum refineries and natural gas plants in 10 countries worldwide,
Table 1.

Table 1. AmiPur® user’s list
Customer
Crown Central Petroleum Corp.
Motiva Enterprises LLS
Shell Opus
Conco Phillips
Sunoco Mid-America
Torch Energy Marketing
Duke Energy
Marathon Ashland Petroleum
Tampa Electric/Polk Power Plant
Marathon Ashland Petroleum
Petrox S.A.
Lyondell-CITGO Refining Company
La Gloria
Nerefco – Europort
Reliance Petroleum – Jamnager Complex
Amoco (BP) Sharjah Oil Company
Sinopec Zhenhai
Praxair Inc.
P.T. Susila – Krakatau Steel
Enbridge Pipelines LP
San Nazzaro Gasification Plant – Snamprogetti
Vintage Petroleum Inc.
PXP/DCOR
SINCOR
Valero Aruba Refining
Location
Pasadena, Texas, USA
Port Arthur, Texas, USA
Bakersfield, California, USA
Ferndale, Washington, USA
Toledo, Ohio, USA
Snyder, Texas, USA
Hallettsville, Texas, USA
Garyville, Louisiana, USA
Mulberry, Florida, USA
Robinson, Illinois, USA
Talcahuano, CHILE
Houston, Texas, USA
Tyler, Texas, USA
NETHERLANDS
Gujarat, INDIA
Sharjah, UNITED ARAB EMIRATES
Zhejiang, CHINA
Texas City, Texas, USA
Jakarta, INDONESIA
Texas, USA
San Nazzaro de Burgondi, ITALY
California, USA
California, USA
VENEZUELA
ARUBA
Eco-Tec offers seven different models of AmiPur®, with different HSS removal capacity.
A typical AmiPur® unit is presented at Figure 1.
There are basically two steps in the AmiPur® operating cycle: amine loading and caustic
regeneration. This cycle is automatically repeated every 10-15 minutes.
Lean amine solution is pumped through a cartridge filter and into the resin column. The
ion exchange resin removes the heat stable salts and the purified amine solution is
directed to the flash tank or returned into the amine batch.
Loading step: R’OH + RN 3 + HHCOO -
R’HCOO + RN 3 + H 2 O
During caustic regeneration step, dilute caustic soda is used to regenerate the resin
column. The unit draws concentrated caustic from tanks or drums and dilutes it to the
proper strength automatically.

Regeneration step: R’HCOO + NaOH
R’OH + HCOONa
Note: R’OH – resin surface, RN 3 – tertiary amine, HCOOH - HSS
Figure 1. Skid mounted AmiPur® unit
With the same HSS removal capacity, AmiPur® has the following advantages over other
amine purification systems using ion exchange technology,
• AmiPur® uses the least amount of NaOH for regeneration;
• AmiPur® generates the least amount of waste;
• AmiPur® uses the least amount of resin;
• AmiPur® has the least amine loss;
• AmiPur® has the smallest skid size.

3. Case Study I: Crown Central Petroleum Corporation (CCPC), USA
The amine unit in CCPC contains a gas liquid contactor or fuel gas absorber, a liquidliquid
C3/C4 amine treater, one amine regenerator a flash drum, heat exchangers, amine
filters, a slip stream amine reclaimer, and several associated pumps.
The main fuel gas absorber is a packed column with 2 beds of random packing and
demister type separation at the top gas outlet. The lean amine feeds the top bed of
packing through a distributor and flows down the column, contacting the sour fuel gas
and removing the H 2 S. The sour gas enters the bottom of the column above the tower’s
rich amine liquid level. The tower’s pressure drop is measured over inlet gas line to outlet
gas line, and this pressure drop is used to monitor tower pluggage and foaming.
The liquid-liquid amine contactor is a trayed tower with 15 trays. This tower also serves
as an amine surge tank, since about 80% of the amine unit inventory is kept in this tower.
The tower is designed to remove about 1000 ppm H 2 S from 21,000 BPD C3/C4 mix.
The tail gas unit’s amine system is very similar to the main amine system, with no flash
drum and only a single amine absorber.
As HSS build, the amine filters plugged more frequently. Iron in the solution started to
climb. Heat exchanger surfaces became fouled forcing the operator to increase the energy
input to the unit’s regenerator reboiler. Tower internals became fouled, increasing
velocities and pressure drop to the point of increasing the overall amine losses. The
amine solution itself started to “foam” more easily due to the increase of impurities in the
solution, and an rapid changes in absorber feed rates caused amine carryover, amine
losses, tower instability, potentially poor H 2 S treat, environmental non-compliance, and
sulfur plant upsets.
AmiPur® Operation at CCPC
At Crown Central Petroleum’s Pasadena, Texas refinery, an AmiPur® unit was installed
in 1998 to effectively remove HSS from MDEA solution. The unit was started up in
October 1998.
The HSS in solution were at approximately 2.4 wt% (as MDEA) when the AmiPur® unit
was started up, and within 30 days the HSS went down to less than 2 wt.%. Material that
had been accumulated from the amine unit prior to installation with HSS level of 3.5
wt.% was then introduced back into the process. The HSS level in the solution increased
back to 2.4 wt.%.
By March 1999, after a unit shut down for maintenance and a replacement of the amine
regenerator tower, the HSS level was down to 1.75 wt.%. A significant decrease in
corrosion rate was observed. The ultimate goal of the refinery is to keep corrosion rate as
close to zero as possible. To achieve this goal, it was decided to decrease the HSS

concentration further, from 1.5 wt.% to 0.5 wt.%, so the unit was upgraded with extra
capacity. Figure 2 is the curve of the heat stable salt decline.
Due to the decrease in HSS level, corrosion probe readings, which had been as high as
160 mpy before, now average less than 10 mpy. As shown in Figure 3, since year 2001,
the readings have always been close to zero.
As shown in Figure 4, filter change frequency decreased from more than 10 times per
month to average once per month.
Due to more stable operation, less filter change, and less foaming, annual amine purchase
has been decreased from 200,000 pounds in 1998 to about 50,000 pounds since year 2000,
see Figure 5.
Figure 6 shows that the total hours H 2 S out of compliance each year decreased from
hundreds of hours each year (even more than one thousand hours sometimes) to less than
50 hours ( sometimes zero 0 hour).
HSS By INEOS
% HSS
6
5
4
3
2
1
0
1997/05/16
1998/04/27
5.46 5.38
4.97
4.4
3.76
2.95
2.62
2.16 2.13
2.14
1.86 1.88
1.62
1.49 1.59
1.77
1.311.2
1.15
0.82 0.71
0.49
0.42 0.41 0.27 0.28 0.42 0.56 0.42 0.5 0.34
0.53
0.69 0.73 0.6 0.77 0.998
0.701 0.598 0.62 0.71 0.8352
0.6309 0.6153
0.34 0.25 0.26 0.28 0.22 0.28 0.41 0.3962
0.5755 0.7151 0.6368 0.5565
0.2978
1998/11/23
1999/04/26
1999/08/23
2000/01/03
2000/05/15
2000/09/25
2001/03/19
2001/07/30
DATE
2002/02/26
2002/07/29
2002/12/02
2003/07/28
2004/01/23
Figure 2. HSS level at the main amine unit at CCPC Pasadena refinery.

MONTHLY MPY
120
100
102
108
103
100
80
84
87
85
81
75
60
48
50 51 50
53
40
33
40
37
28
27
MONTHLY MPY
20
0
May 97 Ave
Dec 97 Ave
July 98 Ave
20
17 17 17 15
1313 12
10
4 5 5 65
1 1 23 46 4 7 4
2111 00000000000000000 00000000000000000
Feb 99 Ave
Sept 99 Ave
Apr 00 Ave
Nov 00 Ave
July 01 Ave
Apr 02 Ave
Nov 02 Ave
July 03 Ave
Feb 04 Ave
Figure 3. Corrosion probe readings at CCPC Pasadena refinery.
Filter Changes Per Month
# Changes per Month
15
10
5
0
11 11
Ave
97
Ave
98
2.6
Ave
99
1.1 1 2.1
Ave
00
Ave
01
Ave
02
0.8 1
Ave
03
Ave
04
Figure 4. Filter changes per month at CCPC Pasadena refinery.

Amine Purchases
Pounds MDEA
500000
450000
400000
350000
300000
250000
200000
150000
100000
50000
0
1992
Purchases
1994
Purchases
1996
Purchases
1998
Purchases
2000
Purchases
2002
Purchases
Figure 5. Annual amine purchase at CCPC Pasadena refinery
Total Hours H2S Out Of Compliance
2500
2000
2037
1938
1500
1166
1000
500
504
420
525
0
55 21 0 30 10 0
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Figure 6. Total Hours H 2 S out of Compliance at CCPC Pasadena refinery

4. Case Study II: SINOPEC Zhenhai refinery, China
Problems in #2 catalytic cracking/amine scrubbing unit
#2 catalytic cracking unit in Zhenhai refinery, China, has cracking capacity of 3,000,000
Tonne/year. This FCC unit is connected to an amine scrubbing unit using MDEA, which
treats 160,000 Tonne/year of dry gas and 450,000 Tonne/year of LPG. In 2001, treating
capacity of LPG was increased to 600,000 - 700,00 Tonne/year. Major problems with the
amine scrubbing unit are: (1) high concentration of suspended solids, frequent filter
clogging, amine losses due to foaming and equipment fouling (see Figure 7, 9). (2) severe
corrosion problems found in reboiler, higher temperature piping and lean/rich heat
exchanger (see Figure 8). Corrosion was also observed at all connections. On December
5, 2001, leaking in gas piping was found. In July 2002, both inlet and outlet piping and
lean/rich heat exchanger started leaking. In September 2002, the whole unit was shut
down for repair. There was 60 Tonne of 24% dirty amine drained from the unit.
AmiPur® operation at Zhenhai refinery
Based on the HSS analysis results shown in Table 2, an Eco-Tec AmiPur® unit (AM15)
was selected to keep the system HSS level below 1 wt.% (as MDEA). There are two
operation modes: hig HSS mode and low HSS mode. The high mode is used to bring
HSS level down to 1 wt.% as fast as possible. The low mode will keep the HSS
concentration in amine solution below 1 wt.%
Table 2. #2 FCC amine scrubbing unit Heat Stable Salt analysis results in 2001
Date 6.22 6.25 6.26 6.27 6.28 6.29 7.2
HSS,wt% 6.42 6.75 6.76 6.81 6.82 6.90 7.2
The system was installed on August 11, 2003 and started up on August 22, 2003. By
September 6, the system had been running for 2300 cycles at high HSS mode and the
HSS level was brought down from 3.8 wt.% to 1.0 wt.%. The system was switched to
low HSS mode and the HSS level in solution has been kept below 1 wt.% (as MDEA),
lowest at 0.27 wt.%, as shown Figure 10.

Figure 7.Lean/rich heat exchanger piping
Figure 8. Reboiler piping
Figure 9. Erosion inside lean/rich heat

HSS l evel
4. 0%
3. 5%
3. 0%
2. 5%
HSS in AmiPur®
i l t
2. 0%
1. 5%
1. 0%
0. 5%
HSS in AmiPur®
tl t
0. 0%
8/ 7 8/ 17 8/ 27 9/ 6 9/ 16 9/ 26 10/ 6 10/ 16 10/ 26 11/ 5 11/ 15
Figure 10. HSS level change in amine solution at Zhenhai refinery, China
Due to the continuous removal of HSS by AmiPur®, system corrosion rate has been
decreased dramatically. Average Corrosion rate at the top of the regenerator before
AmiPur® was 90 mpy as shown in Figure 11. When HSS level was brought down to 0.5
wt.%, the corrosion rate at the top of regenerator is as low as 2 mpy, shown in Figure 12.
When HSS level was 6 wt.% (as MDEA), foam height was 20 cm and break time was 20
seconds. Because of the low HSS level, both foam height and break time in #2 FCC
amine unit are obviously better than other amine units, especially break time, shown in
Table 3.
When the HSS level is lowered, more amine is available for sour gas treating. In Zhenhai
refinery, a 25% of amine saving was realized one month after the start up of AmiPur®.

Figure 11, Corrosion rate before AmiPur®® operation at Zhenhai refinery,
Figure12, Corrosion rate after AmiPur®® operation at Zhenhai refinery, China

Table 3. Comparison of HSS level(wt%),foam height(cm), and break time(s)in
different amine units at Zhenhai refinery, China
Time #2 FCC #1 FCC Delayed coking
HSS Foam height Break
time
HSS
Foam
hetight
Break time HSS Foam height Break time
10.1 0.63 3.5 5 4.62 4.0 12 3.58 5.0 18
5
10.1 0.65 3.0 5 4.65 4.5 10 3.62 5.5 21
6
10.1 0.62 3.5 6 4.69 4.0 12 3.67 5.0 23
7
10.1 0.60 3.5 5 4.76 4.5 13 3.75 6.0 18
8
10.1 0.59 3.0 6 4.88 4.0 11 3.8 5.5 19
9
10.2 0.59 3.5 5 4.95 4.0 12 3.87 5.0 20
0
11.5 0.45 3.5 5
5. Summary
Amine degradation causes the formation of heat stable salts (HSS) that can lead to
corrosion. The amine unit performance begins to deteriorate as the HSS level increases,
and the performance absorber and regenerator becomes less stable.
One of the most important results of an AmiPur® installation is the STABLE and
RELIABLE operation of the amine plant, which in turn has a dramatic environmental
impact. The continuous removal of HSS has immediate and easily quantifiable results:
reduction of filtration costs; elimination of periodic chemical cleaning of the absorber
tower; improved gas treating capacity of the unit due to increased amount of amine
available for gas treating; elimination or reduced use of antifoamers, neutralizers and
corrosion inhibitors; elimination of the cost associated with previously used methods of
HSS removal. All AmiPur® installations have demonstrated the benefits of continuous
removal of HSS for both oil refineries and natural gas plants.