bfi \

CONVERSION OF THE GAS PURIFICATION SYSTEM TOBASF aMDEA@SOLVENT AT PT. BADAK NGL

CONVERSION DU SYSTEME DE PURIFICATION DU GAZ : EMPLOIDU SOLVANT aMDEA@DE BASF CHEZ PT. BADAK NGL

Volker SchudaBASF Aktiengesellschaft, GermanyFax: +49 – 621 –60–41398

ABSTRACTThe solvent swap at the world’s largest LNG-plant to BASF’S aMDEA was a complete success insolving earlier corrosion and scaling problems. After two years of operation the iron content in theaMDEA-solvent for the C02-removal kept below 10 ppm and the plant reliability could be increased bymore than 10 Y. while the production costs dropped due to a significantly lower maintenancerequirement.

RESUMELe changement de solvant clans la plus grande unite mondiale de GNL au profit du produit aMDEA deBASF a entralne I’eradication de tous Ies problemes de corrosion et de calaminage. Apres deux ansd’utilisation operationnelle, la teneur en fer du solvant aMDEA destine a I’elimination du C02 estrestee inferieure a 10 ppm, la fiabilite de I’installation a pu @treaugmentee d’au moins 10 YO et Iescotlts de production ont rapidement diminue en raison de la baisse des frais de maintenance.

DISCLAIMER

Portions of this document may be illegible

in electronic image products. Images are

produced from the best available original

document.

.

1. INTRODUCTION

In 1977 PT. Badak started production of LNG, two trains with a LNG-capacity of 800,000 tons each.

During the period 1982 to 1999 six further trains were constructed. At present PT. Badak is operating

the world’s largest natural gas liquefaction plant and has an annual capacity of about 21 millions tons

of LNG, one million tons LPG Propane & Butane and one million tons of hydrocarbon condensate.

In the seventies, primary amines were particularly popular in gas treating and therefore, also PT.

Badak started with MEA as the solvent for C02 removal. After many operational troubles PT. Badak

tried to solve these problems by changing the solvent to one of the blended MDEA-based systems,

which became popular in the eighties and early nineties. However, the operational troubles became

even worse. Eventually, BASF’S aMDEA@was employed in one train. Two years later, all trains have

been converted to aMDEA@due to the superior performance with respect to process reliability.

Corrosion, scaling and foaming is no longer an issue for PT. Badak.

This paper will show the former troubles in details and how the solvent swap was carried out.

2. PROCESS HISTORY OF THE ACID GAS REMOVAL UNIT AT PT. BADAK

PT. Badak uses an amine based C02-removal system to achieve the LNG-specification of less than

50 ppm C02 in the sweetened gas. The acid gas removal unit in all eight parallel trains comprises a

single stage absorber, a high pressure flash-vessel and a stripper regenerator. Both columns are

equipped with bubble cap trays, the heat exchangers are either shell and tube or plate and frame

types. Fin-fan coolers are used for most of the cooling duty of the lean amine solvent.

2.1 First solvent swap from MEA to a formulated MDEA

The original solvent in the trains A - D right from start-up was MonoEthanolAmine (MEA). Despite the

addition of corrosion inhibitors, major equipment was subject to severe corrosion and scale formation,

together with foaming. Many leaks were caused by stress corrosion cracking as a result of primary

amine attack.

In the context of a capacity increase commencing 1990-91, a formulated MDEA solvent system

replaced the MEA solution consecutively in Trains A-D. The newer Trains E-G were directly

commissioned with this alternative solvent.

Understandably, the corrosivity of the solvent was investigated extensively. Following the swap,

solvent analyses showed no untoward heavy metal content in the solution for about two months.

Thereafter, a low concentration of heavy metals was observed and subsequently a steep increase of

the iron content in the solution took place.

The iron content reached a level of 700 ppmw (oversaturation of the solution), followed by a slight

reduction to about 250 ppmw as a result of precipitation of iron carbonate complexes. This coincided

with a considerable accumulation of heat stable salts. At this time, the formulated MDEA became

corrosive and abrasive. The operating conditions approached an equilibrium state of continuous

equipment corrosion on the one hand, and scaling of material surfaces with deposit layers on the other

hand. This required excessive defoamer dosage rates, which in turn enhanced the formation of scale.

Fig. 2: Sca/ing of tubes: The hot end bundles of the exchangers exhibited considerable scaling on

both the shellside (lean amine) but most severe on the tubeside (rich amine) causing

excessive pressure drop across the bundles.

Fig. 3: Example of MO tubes of above shown heat exchanger

,.

All major equipment as well as large sections of the pipework were subject to severe corrosion attack.

The corrosion problems led to several unplanned shutdowns and to the need to replace the corroded

equipment. This happened not only in the old trains A to D, but also in the new ones E, F and G, which

were never operated with the MEA solvent and which utilize much more stainless steel equipment.

Fig. 4: Window patching in order to repair the flash drum

.’*

The tubes of the lean solution fin fan cooler also exhibited severe thinning and a great number leaked.

This proves the corrosive/abrasive nature of the

ruled out for a fully regenerated lean solution.

former solvent as C02 pitting corrosion attack can be

Fig. 5: Leaks in the tube sheets of the heat exchangers after operating the former formulated solvent

about one year

A “material upgrade” – program was initialised. Sections of the rich and lean solution piping suffered

damage, due to erosion corrosion attack, mainly confined to elbows, flanges, reducers/expanders and

even some straight lines. These were replaced by stainless steel. However, even this measure failed.

S&a&-i@ SiwIb&3m

Fig. 6: Increasing chromium-ion content in the former formulated solvent

The hopes placed in this first solvent change to a formulated MDEA proved to be unfounded, as the

unit still suffered from leaks due to corrosion and severe scaling. Everything that PT. Badak tried,

however, was merely curing the symptoms. Therefore the “material upgrade” - program also failed.

3. SOLVENT SWAP

PT. Badak gave BASF the chance to prove the advantages of aMDEA@ in one train. The reason was

because BASF has demonstrated that the aMDEA@process is trouble-free which is clearly shown in

more than 100 reference plants. Whenever BASF made a solvent swap or a revamp we eradicated

the corrosion and scaling problems, because our solvent is chemically and thermally extremely stable.

Therefore, in all our reference plants there has never been a single re-swap to another solvent in

more than 20 years. This outstanding record can not be matched by any other amine-based solvent.

Train C was chosen for the trial of the second solvent swap. A straight solvent swap without any plant

modifications was carried out in October 1997. In a rapid turnaround, the previous solvent was drained

off, the unit cleaned, filled with aMDEA@-solutionand re-started.

3.1 Cleaning Procedure

The corroded equipment surfaces were washed off with a water jet. Corrosion cavities were then

hollow-ground and coated with an epoxy protection layer. The trays and the column base of the

absorber and stripper were covered with metal dust and residues and had to be cleaned with a

vacuum cleaner.

The heat exchanger tube bundles were removed and cleaned with a high pressure water jet. The

tubing at the hot end in the solvent heat exchangers was mostly replaced as the firm deposit layer

inside the tubes could not be removed. The outer surface of the tubes was covered with a greyish-

brown layer (mainly FeC03) after cleaning, which could partly be removed.

The second step was that the system was flushed by circulating potash solution, especially for the

removal of grease, corrosion and decomposition products, rust or other residues to minimize the

impact of the operational history on the aMDEA@performance. The caustic flushing should also be

employed when considerable construction work has been carried out, if new equipment has been

installed, or if the entire plant is new.

Afterwards, the whole unit was filled with condensate, heated up to about 90 “C and circulated for 6

hours. This procedure was repeated once more, with samples being taken to check for the absence of

residual suspensed particles in filtration tests. The condensate analysis after 6 hours circulation

showed no foam activity, no suspended particles and the samples had a clear coloration.

The aMDEA@-premixwas introduced into the system and diluted with water to an amine concentration

of 40 wtYo. The solvent circulation was started and afterwards the feed gas throughput stepwise

increased until 1107. of the former capacity was reached within 3 days. The C02-slip was less than

10 ppmv at a 30% lower solvent circulation rate. That means that there is a big potential for a LNG

capacity increase. This could be seen from another angle: the same gas throughput could be achieved

with a more compact aMDEA@-design with reduced CAPEX.

4. BENEFITS OF THE SOLVENT SWAP TO BASF’S aMDEA@

This solvent swap to BASF’S aMDEA@in the world’s largest LNG-plant may be the fastest solvent

change which has ever been carried out. Within two years the former solvent was exchanged in all 7

trains. This record was possible because right after start-up with aMDEA@ there was a complete

eradication of all the earlier operational troubles: no more corrosion, no more scaling. The plant

reliability has increased and the maintenance costs were significantly reduced.

The experience of about 90 months of operating aMDEA@at PT. Badak can be summarized as

follows:

Benefits of the Solvent Swap

no corrosion damage; iron content in the solution less than 10 ppmw; corrosion

rate measured from coupons lower than 0.1 mm per year.

plant reliability increased by more than 10%

solvent make-up 47 YOlower

steam consumption 2070

solvent circulation rate 30

lower

!/iOlower

Fig. 7: Benefits of the solvent swap

A reliable gas scrubbing process, providing long on-stream times, is thus essential for economic

production.

In hard times Gas Processors should move with the times. Although facing shrinking margins in times

of lower gas prices, this example shows that there is still a big potential for saving money.

5. CONCLUSION

The solvent change to BASF’S aMDEA@was a complete success. The plant reliability and plant safety

could be significantly increased and the maintenance costs reduced. There was a complete

eradication of the corrosion problems and unscheduled shut-downs in the amine C02 removal unit.

Secondly this success was possible because BASF knows how to carry out solvent swaps. Another

reason is that there is a big difference between so called “formulated MDEA solvents” and BASF’S

aMDEA@.This has been proven in so many units where BASF’S aMDEA@replaced formulated MDEA-

solvents.

BASF’S aMDEA@is a special formulation which is more than the sum of its components.