Tekimkmkl'k

8/13/2019 Tekimkmkl'k

1/25

Shell Global SolutionsConfidential Technical Proposal PPGJ Project : CPP Gundih AGTU

Confidential3

This Confidential Technical Proposal for a Sulfinol-M/XProcess Acid Gas Removal Unit (AGRU),Molecular Sieve Dehydration and Mercaptan Removal unit (MSU) and a Shell-Paques Process SulphurRecovery Unit (BSRU) has been prepared based on the an updated information received from PT PTTripatra Engineering & Construction(herein after refered to as TRIPATRA) on 18th of July 2008entitled SPECIFICATION FOR SHELL GLOBAL COMPANY, hereinafter referred to as theRequest For Proposal (RFP).

This proposal also incorporates inputs from the meetings and discussions held throughout the period ofthe proposal development.

This Proposal provides preliminary AGRU, MSU and SRU design information based on the feedconditions as specified in the RFP. As the project entails a complex gas treating challenges, we believe thatthe solution provided best meets the project requirements as outlined by Pertamina EP PPGJ project team.

This technical proposal is provided under the Secrecy and Restricted Use Agreemet between Shell andTRIPATRA for the purpose of enabling TRIPATRA to consider the Shell Licensed Processes forapplication in the PPGJ Project.

The corresponding commercial offer shall submitted as a separate document from this technical proposal.

Sulfinol is a trademark of Shell

DISCLAIMER

The p urpose of this proposal is to assist Customer, as recipient, in deciding whether or not to proceed with discussions with Shell concerning an engagement o f Shell for thelicense and services stated herein. This proposal is not intended to constitute an offer or acceptance or to give rise to any binding obligation unless and until a formal contract issigned by both parties. Nothing contained herein shall constitute otherwise. Until a final contract is signed, either party may close discussions for any reason with no liability tothe other.

Shell disclaims any and all liability for representations or warranties, express or implied, contained in the proposal or in any other written or oral communications with Customerconcerning this subject matter. Only those particular representations and warranties which may be made in a written contract shall, subject to such limitations and restrictions asmay be specified in the contract, have any legal effect.

This proposal is confidential and subject to t he te rms of the Confidentiality Agreement between t he p arties dated as of 31st July 2008. This Pro posal is being d elivered forinformational purposes only and upon the express understanding that it will be used only for the purposes set forth above.


2/25


Confidential4

Document HistoryDate Issue Reason for

ChangeAuhors Reviewed/Verified by Approved by

20/9/2008 A Issued forinternalappoval

Blas, Wilfredo

Koh, Boon Eng

Srivathsan, Bharath

Bajpai, Vishrut

de Oude, Matthijs

Sakthivel, Ramachandran

Srinivasan, Rajiv

van Heeringen, Gijs

Paques B.V.

Van Hooijdonk, Jeroen


3/25


Confidential5

Block Flow Diagram of Acid Gas Treating Unit (AGTU)

The general process line-up for the Acid Gas Treating Unit for the CPP Gundih Station is as follows (onlymain process streams shown):

Figure I: Acid Gas Treating Unit up Simplified Block Flow Diagram (CPP Gundih)

Most of the contaminants (CO2, H2S, COS, and Mercaptans) in the Feed Gas to the AGTU are removedby the Acid Gas Remval Unit (AGRU) with the remainder of mercaptans recovered in the Molecular SieveUnit (MSU). The MSU also dries the gas to sales specification. Fuel Gas is partially taken from the sales gasto provide the requirements of the CPP.

The sulphur species in the acid gas stream out of the AGRU are then recovered in the Biological SulphurRemoval Unit (BSRU) and the desulphurized CO2stream is then routed to the incinerator.

Additional offgas feed stream from the upstream processing units in the CPP are routed to the thermaloxidizer of the BSRU for disposal.

Feed Gas toAGTU

LP Separator,CondensateStabiliser andProduced WaterInjection UnitOffgas Streams

Sales Gas from AGTU

ACID GAS

REMOVAL UNIT

(AGRU)

MOLECULAR

SIEVE UNIT (MSU)

BIOLOGICAL SULFUR

RECOVERY UNIT

(BSRU)

HP Fuel Gas to Distribution

Incinerator Gases

Recovered Sulfur

Bleed Stream to EffluentTreatment Plant

By SHELL By EPC ContractorBy SHELLBy EPC Contractor

Water Make-Up


4/25


Confidential6

Table of Contents

Document History 4

Block Flow Diagram of Acid Gas Treating Unit (AGTU) 5

Table of Contents 6

1. Background Information 8

1. Background Information 8

1.1 Overview of the Project 8

1.2 Scope of Proposal 8

2. The Integrated Treating Line-up 9

2.1 Feed Gas Specifications 9

2.2 Product Specifications 112.3 AGTU Plant Capacity 12

2.4 Design Considerations & Assumptions 12

2.4.1 Mercaptan Speciation & Handling 12

2.4.2 Feed Gas Condition 12

2.4.3 Use of Shell Proprietary Contacting Internals in the AGRUAbsorber 12

2.4.4 Use of Solvent Flash Vessel 12

2.4.5 AGRU Feed Gas and Treated Gas Knock Out Drums 132.4.6 Integration with the Molecular Sieve Regeneration GasRecovery 13

2.4.7 Use of a Mechanical Refrigeration Loop in the MSU 13

2.4.8 Mercaptans Conversion in the BSRU 14

2.4.9 Heat Integration Opportunities 14

2.4.10 Re-use of Water Streams 14

3. The Sulfinol - X Process 15

3.1 Process Overview 15

3.2 Process Description 15

3.3 AGRU Process Flow Diagram 16

3.4 Heat & Material Balance 16

3.5 Equipment 16

3.6 Utility, Catalyst & Chemical Requirements 16


5/25


Confidential7

4. The Shell-Paques Process Biological Sulfur Recovery Process 17


4.2 Process Chemistry 19

4.3 Process Description 194.4 BSRU Process Flow Diagram 20


4.6 Equipment 20

4.7 Stream Summary 20


5. The Molecur Sieve Process 22


5.2 Process Description 24

5.3 MSU Process Flow Diagram 25


5.5 Equipment 25



6/25


Confidential8

1. Background Information

1.1 Overview of the Project

PT Pertamina E&P intends to produce the gas wells in various fields in the Gundih Area located in

Kabupaten Blora, Central Java, Indonesia. The sales gas is to be used for power generation.The gas is characterized as difficult due to the high levels and the prescence of the various impurities inthe gas (CO2, mercaptans, H2S and COS) as further described in Section 2 of this proposal.

To meet the sales gas specifications, PT Pertamina EP plans to construct and operate a Central ProcessingPlant (CPP) which will comprise of flowlines, inlet manifolds, gas separation units, condensate handlingunit, acid gas treating unit, produced water injection unit and other required supporting systems (e.g.utilities).

TRIPATRA is participating in the tender of the PPGJ Project for the development of the CentralProcessing Plant and as required by Pertamina, the process design of the AGTU shall be developed byapproved licensor.

1.2 Scope of Proposal

Shell Global Solutions has been asked to provide a confidential technical proposal for the processesrequired for the Acid Gas Treating Unit for CPP, which includes the following units:

Acid Gas Removal Unit (AGRU)

Molecular Sieve Unit (MSU)

Biological Sulphur Recovery Unit (BSRU)

Caustic Unit*

Some equipment items within the AGTU have been excluded from Shell scope in clarification withTRIPATRA and these include:

Unit Equipment Items Remarks

AGRU Filter coalescer, F-0205 on feed to AGRU As specified by TRIPATRA

MSU Filter coalescer, F-0301 A/B on feed to MSU As specified by TRIPATRA

*Refer to Section 2.4.6 with respect to the recommeded removal of the caustic unit from the AGTU.


7/25


Confidential9

2. The Integrated Treating Line-upThe AGTU integrated design is based on the feed gas conditions and product specifications as outlined inthe RFP and as described further below.

2.1 Feed Gas SpecificationsThe main feed gas stream to the AGTU comes from the from the Filter Coalescer, F-0102 A/B. Thefollowing table outlines the composition given:

Table 1: Feed Gas to AGTU

Feed Gas Conditions

Flow rate 75 MMSCFD

Temperature 108 F

Pressure 400 psig

Composition (dry basis)

Carbon Dioxide 23.00 %-mole

Nitrogen 0.47 %-mole

Oxygen 0.00%-mole

Methane 70.78 %-mole

Ethane 2.23 %-mole

Propane 0.8 %-mole

i-Butane 0.17 %-mole

n-Butane 0.19 %-mole

i-Pentane 0.08 %-mole

n-Pentane 0.06 %-mole

n-Hexane 0.08 %-mole

n-Heptane 0.09 %-mole

n-Octane 0.04 %-mole

n-Nonane 0.01 %-mole

n-Decane 0 %-mole

H2S 7000 ppmv

Mercaptans 1700 ppmv

Carbonyl Sulphide 50 ppmv

Notes:(1) Contaminant levels of CO2, H2S, RSH and COS have been taken with a+/- 10% variance as advised by TRIPATRA(2) Feed Gas compositions have been normalized with water exception ofwater content(3) Mercaptan speciation was taken as 100% methyl mercaptan

Offgases from the LP Separator and Condensate Stabiliser are combined and with the offgas from theProduced Water Injection Unit are routed to the BSRU. The following tables outline the compositiongiven for each of the streams.


8/25


Confidential10

Table 2: Off Gas Feed to BSRU

Feed Gas Conditions

Flow rate 0.01 0.045 MMSCFD

Temperature 120 127 F

Pressure40

91 psig

Composition (dry basis)

CO2 4.390 32.66000 %-mole

Nitrogen 0.600 0.19700 %-mole

Methane 90.286 0.00000 %-mole

Ethane 2.841 57.33700 %-mole

Propane 1.017 3.74200 %-mole

i-Butane 0.215 1.68500 %-mole

n-Butane 0.240 0.37300 %-mole

i-Pentane 0.100 0.41800 %-mole

n-Pentane 0.074 0.17000 %-mole

n-Hexane 0.096 0.12600 %-mole

n-Heptane 0.099 0.15100 %-mole

n-Octane 0.037 0.14300 %-mole

n-Nonane 0.007 0.04800 %-mole

H2S 45 0.00800 ppmv

M-Mercaptan 13 0.00000 ppmv

COS 0.4 137 ppmv

H2O 0 39 %-mole

Condensate 0 0 %-mole

Total 100.00 100.00

Notes:(1) Feed Gas compositions have been normalized with water exception of

water content;(2) Mercaptan speciation was taken as 100% methyl mercaptan;


9/25


Confidential11

2.2 Product Specifications

The AGTU has a total of 3 final products and 3 intermediate products as described below.

Table 3: List of Product Streams from AGTU

Final Products

Stream Unit From To

Sales Gas MSU Custody Transfer Metering

Recovered Sulfur BSRU Site Storage

Incinerator Stack Gas BSRU Environment

Intemediate Products

Stream Unit From To

Flash Gas AGRU Fuel Gas System

Fuel Gas MSU Fuel Gas System

Bleed Stream BSRU Effluent Treatment Plant

The following product specifications have been applied:

Table 4: Sales Gas Specification

Parameter Value Unit

Temperature, max 120 oF

Pressure, min 330 psig

Water content, max 7 lbs/MMscf

Particles, size 5-10 micron

CO2content , max. 5 %-mole

H2S , max. 3 ppmv

Total sulphur, max. 30 ppmv

Table 5: Recovered Sulphur Specification


Sulfur Purity, min. 99.5 %wt

Inorganic Ash, max. 0.05 %wt

Carbon Content, max. 0.05 %wt

H2S Content, max. 10 ppmwt

Water Content, max. 1 %wt

Color Bright Yellow

Flake Size 10-15 cm

Odour Odourless

Notes:(1) The biosulphur product, out of the Shell Paques Unit has proven use in the

agricultural industry and will result in savings on investment of the sulphur work-up section.

(2) The sulphur work-up section (melter and flaking system) is not a Shell licensedprocess and thus performance guarantees shall have to be made with therespective vendors.


10/25


Confidential12

Table 6: Incincerator Stack Gas Specification


Sulfur Dioxide, SO2 2600 mg/Nm3

Notes:(1) Based on 25oC and 1 atm.(2) Maximum O2content of stack gas is 3% vol.

2.3 AGTU Plant Capacity

The AGTU has been sized for a maximum capacity of 75 MMSCFD of the Feed Gas to the AGRU. Nofurther overcapacity has been incorporated at this stage of the project.

2.4 Design Considerations & Assumptions

Reference is made to the Block Diagram of the AGTU.

2.4.1 Mercaptan Speciation & Handling

The mercaptan speciation plays an important role in determining how the desired total sulphur

specification can be achieved out of the AGTU. In discussion with TRIPATRA the speciationadopted for the feed gas was advised as 100% methyl-mercaptan.

The amount of mercapatans in the feed gas to the AGTU is high and on the basis thatmercapatans removal in the AGRU is to be achieved using an enhanced MDEA process (i.e.Shells ADIP-X), the amount of mercaptan removal to be performed by the MSU is too highand will result in a bed size which is beyond the practical limitations of Molecular Sievestechnology. For this reason, the use of an MDEA hybrid solvent Shells Sulfinol-X, has beenapplied, such that bulk of the mercaptans (~97%) can be removed in the AGRU and sent forSulphur recovery.

Appendix VIII contains a reference list of Sulfinol applications wherein similar combination ofcontaminants have been addressed.

2.4.2 Feed Gas Condition

For the purpose of the current design, the following assumptions have been made for the feedgas to the AGRU:

It is free of any solid particles

It is free of liquid hydrocarbons

The gas is at its (water) dewpoint

2.4.3 Use of Shell Proprietary Contacting Internals in the AGRU Absorber

The RFP mentions the use of a packed column for the AGRU absorber, however uponcomparison the use of Shell Proprietary Calming Section/Hi-Fitrays in the AGRU absorber isexpected to reduced the column height by about 2-4 meters as use of packing will requireadditional space internal liquid redistributors.

Calming Section, Hi-Fi,ADIP-X and Sulfinol are trademarks of Shell

2.4.4 Use of Solvent Flash Vessel

Though the amount of hydrocarbon entrainment can be minimized through the use of specialinternals at the bottom of the main absorber, the use of a solvent flash vessel was reviewed andretained for the following reasons:


11/25


Confidential13

(a) The solvent flash vessel provides a buffer/surge capacity which contributes to theoperational stability of the system as it protects the regeneration section of the AGRU frombeing directly affected by any upset in the absorber;

(b) A Flash Gas Absorber (FGA) has been included to produce a desulfurized flash gas stream,which will be available for use as fuel gas.

2.4.5 AGRU Feed Gas and Treated Gas Knock Out Drums

TRIPATRA has confirmed the inclusion of a filter colaescer vessel in the following locations:

1) upstream the AGRU Feed Gas Knock out Drum

2) downstream the AGRU Treated Gas Knock Out Drum

which are expected to perform the same if not better removal efficiency of liquids from the gasstream. Hence it can be considered to remove the assocaited AGRU Feed and Treated GasKnock Out Drums under the conditions that:

The filter coalescer is located inside the AGRU plot or such that omission of the AGRUSweet/Treated Gas Knock Out Drum does not create a portion of piping that can havecondensation of free liquids, which could lead to corrosion.

The design of the filter coalescer is the responsibility of TRIPATRA.

2.4.6 Integration with the Molecular Sieve Regeneration Gas Recovery

The option of the proposed Caustic Unit for the recovery of the MSU Regen Gas was comparedto the use of an amine scrubber as an alternative option.

The initial conclusion from a +/- 35% FOB cost comparison of main equipment items was thatthere is no significant difference but the main benefits of employing an amine absorber for regengas treating in the MSU are:

Lower plot space requirements due to lower equipment count as well as associatedauxillary and caustic storage facilities which will impact the overall installed cost;

1 less toxic waste stream (Di-Sulphide Oil, DSO) to store/dispose;

1 less unit to operate as the amine scrubber can be treated as part of the AGRU and does

not require a different skill/competence to operate;

Less regret cost should there be a lower mercaptan content during actual operatingconditions;

Presence of about 5 % CO2 in the regen gas will lead to very high consumption / loss ofcaustic. This is not an issue with an amine scrubber because the used up amine iscompletely regenerated.

Hence it is recommended to use an Amine Scrubber to recover the MSU Regen Gas.

2.4.7 Use of a Mechanical Refrigeration Loop in the MSU

The RFP specifies the use of an Air Cooled Exchanger to cool and AGRU Sweet/Treated Gasstream prior to entering the Sweet/Treated Gas Knock Out Drum. This will bring the gas

temperature down to approximately 116o

F (46o

C), which is much above the typical inlettemperature to a mol sieve unit based on LNG applcations. It is typically not recommended todesign a MSU unit a high inlet temperature.

The following are the key benefits seen in the design of the Molecular Sieve Unit if designed onthe basis of an inlet temperature of 21oC as compared to a design at a high inlet temperature(about 46oC):

The height of the water removal mol-sieves is halved

Around 5% decrease in the height of Sulphur removal mol-sieves.

About 17% decrease in the mol-sieve vessel diameter.


12/25


Confidential14

Regen gas flow decreases by about 50%.

The effect on the regen gas flow is crucial as this also affects the sizing of the Regen GasScrubber and the associated solvent circulation rate and thus the final sizing of the AGRU.

The estimated duty requirement is approximately 1.5 MW and is recommended to be included as

part of the utilities system. Propane can be used as the refrigerant for this purpose.

Further benefit of the refrigeration system can be utilized by cooling the main sour gas feed to theAGTU, which will subsequently improve the sizing of the AGTU.

2.4.8 Mercaptans Conversion in the BSRU

With most of the mercaptans removed in the AGRU and sent to the BSRU in the acid gas streamexiting the AGRU regenerator column, it is required to include a feed pre-treatment unit as partof the BSRU to enable mercaptan conversion into H2S. This is further described in Section 4 andis based on existing and well proven process technologies.

2.4.9 Heat Integration Opportunities

Heating and Cooling duties have been specified in Appendix III Equipment Summary Sheets,for consideration by TRIPATRA to be able to quantify the benefits of heat integrationopportunities and its effect to the rest of the plant that is outside the Shell scope of licensedprocesses (e.g. Hot Oil System).

This can be further explored and developed in the BDP/FEED stage of the project.

2.4.10 Re-use of Water Streams

At several points of the process free water is knocked out of the system and can be consideredfor re-use in the system as water make-up. The main considerations will be the presence ofhydrocarbons in the water stream, which can cause foaming in the amine system.

This can be further explored and developed in the BDP/FEED stage of the project.


13/25


Confidential15

3. The Sulfinol - X Process

3.1 Process Overview

The Shell Sulfinol Process is a regenerative amine-based solvent technology for the removal of CO2, H2S,and organic sulfur compounds such as mercaptans, COS, and CS2 from natural gas feed streams. TheSulfinol Process AGRU solvent utilizes a non-proprietary formulation of amine, Sulfolane and water. Themolecular structure of Sulfolane is shown below.

CH2 CH2

CH2 CH2

S

O O

Sulfolane (2,3,4,5-tetrahydrothiopene-1, 1-dioxide)

The presence of Sulfolane in the solvent enables the Sulfinol Process to achieve highly efficient absorptionand removal of organic sulfur compounds such as mercaptans and COS from natural gas feed.

The Sulfinol Process AGRU design for the PPGJ Project is based on application of a solvent formulationcontaining 50 wt%amine (43%wt MDEA with 7% wt Piperazine), 25 wt%Sulfolane, and 25 wt%water.

3.2 Process Description

The Sulfinol Process AGRU description and equipment tag numbers referenced below correspond to theProcess Flow Diagram inAppendix 1

The natural gas feed first passes through a knockout vessel V-1001 to prevent gas gathering systemcontaminants such as well treating chemicals, pipeline corrosion inhibitors, compressor oils and pipelinescale, etc, from entering the gas absorber C-1001. These contaminants can accumulate in the amine systemand potentially lead to operating problems such as foaming and fouling. Oxygen should also be excludedfrom the natural gas feed to the AGRU to minimize the potential for oxidative degradation of the solvent.

The feed gas is then contacted counter-currently in the absorber (C-1001) over Shell proprietary Calming

Section/Hi-Fi trays with lean solvent, which is supplied under flow and temperature control. The leansolvent feed temperature to C-1001 is maintained at 5 C higher than the feed gas temperature to avoidcondensation of hydrocarbons in the absorber, which can increase the potential for foaming in the AGRUand operational difficulties in the downstream SRU.

The treated gas is then cooled by the treated gas cooler E-1005 to 21oC and free liquids are knocked out inthe filter coalescer, V-1002 before the gas is sent to the MSU.

Rich solvent leaves the absorber column under level control and is routed to a rich solvent flash vessel V-1003, in which the pressure is reduced. Dissolved and entrained hydrocarbons are separated from the richsolvent in the flash vessel. The lighter hydrocarbons form flash gas, which is treated with a smallslip-stream of lean solvent in the flash gas absorber column (C-1003) positioned on top of V-1003 toreduce the H2S and organic sulfur content. The treated flash gas is routed to the plant fuel gas system.

The solvent from the MSU Regan Gas Absorber is added downstream the Flash Vessel to minimize theeffects of the amount of mercaptans going to the flash gas stream and thus the corresponding height of the

Flash Gas Absorber. Entrained heavier hydrocarbons, which are insoluble in the rich solvent, are skimmedfrom the upper layer of the liquid phase in V-1003.

The solvent regeneration system consists of a regenerator column C-1002 with a water wash section, anoverhead condenser E-1003, and a reboiler E-1004. The regenerator operates at low pressure and hightemperature. The pre-heated rich solvent is stripped counter-currently in the regenerator column over amedium of trays with steam generated in the reboiler. The reboiler is heated by a hot oil loop. Thebottom section of the regenerator column holds some volume which can be used as the system's bufferstorage and surge facility by allowing the liquid level to float freely.


14/25


15/25


Confidential17

4. The Shell-Paques Process Biological Sulfur RecoveryProcessThe significant advantages of utilizing Shell-Paques technology in this project include:

A lower CAPEX compared to a Claus-based solution

Ability to handle high levels of CO2produced in the acid gas from the AGRU

System operates at a lower pressure


The Shell-Paques Process is an environmentally friendly biological process for H2S removal and recoveryas elemental sulfur (S) from sour gas streams. The most unique aspect of the process is that it utilizes aliving biocatalyst to oxidize H2S to elemental S. The biocatalyst belongs to the group of naturally occurringcolourless sulfur oxidizing organisms known as Thiobacilli. These are autotrophic organisms, which meansthat CO2is required as their sole carbon source. The Thiobacilli catalyst is fast growing and highly resistantto varying process conditions. The energy needed for growth is obtained from the sulphide oxidation

process. These organisms are naturally occurring and are not genetically manipulated nor modified.

The Shell-Paques Process has the following performance features:

Achieves essentially complete H2S removal and recovery as elemental S.

Simple process configuration and control with stable operation.

Low operating and chemical costs.

Wide and flexible operating range with short system start-up and shut down times.

Environmentally friendly process based on a naturally occurring Thiobacilli biocatalyst.

Recovered sulfur is hydrophilic and directly usable for fertilizer/agriculture applications.

Inherently safe operation

The Shell-Paques process can be applied to sour feed gases with H2S concentrations ranging from 50 ppmvto 100 vol%. Regeneration of the scrubbing solution, rather than its disposal, is a key feature of the Shell-

Paques Process. Regeneration of the scrubbing solution is possible because the caustic consumption due tothe absorption of H2S is compensated by the oxidation of H2S to elemental sulfur and hydroxide.

A simplified Shell-Paques Process block flow diagram is shown below.

Sour feed gas enters the bottom of a packed absorber column. H2S is removed from the sour gas in theabsorber by the alkaline Shell-Paques solvent. The treated gas passes through a demister to minimizeentrainment of solvent and exits the absorber.


16/25


Confidential18

The H2S rich solvent from the bottom of the absorber is routed to the bioreactor. The bioreactor is spargedwith air to enable the biocatalyst to convert the dissolved sulfide into elemental sulfur (S), therebyregenerating caustic soda. The sulfur slurry is then sent to the sulfur recovery section, where it is processed ina sulphur settler and then the decanter and centrifuge, with the recovered water recycled back to the processvia the bioreactor.

The regenerated solvent is recycled from the bioreactor back to the absorber. A small slipstream of solvent is

typically bled from the system to prevent any build-up of salts.

The Shell-Paques Process consists, in principle, of three integrated process sections: an absorber, an aerobicbiological reactor, and a sulfur separator and/or recovery unit.

Feed Pre-treatment Unit

Mercaptans have been identified as a contaminant that, above a certain concentration, will havean impact on the process performance due to its tendency to foam. Mercaptans (especiallymethyl-mercaptan) are expected to be fully oxidised to dimethyl disulphide (DMDS) in thebioreactor. DMDS oil will interfere with the sulfur particles, and consequently foam. Tomaintain operability of the Shell-Paques unit, a pre-treatment is specified.

The pre-treatment unit includes a reduction section to enable conversion of all sulphurcompounds present in the feed gas (especially Mercaptans) into hydrogen sulphide. The acid gasis first heated to ~350C with fuel gas prior entering the reactor. In the reactor, the Mercaptans

are reduced to produce H2S. The reduction process is exothermic and the gas needs to be cooledto a suitable temperature (35C) before entering the Shell-Paques Absober.

Absorber

In the absorber, the sour feed gas is contacted counter-currently with the solvent, which issprayed downwards through the column by nozzles. From the absorber bottoms, the H2S richsolvent is routed to the aerobic bioreactor, where the dissolved sulfides are oxidized intoelemental S. It is important to note that the elemental S is produced in the bioreactor and not inthe absorber. Because of this feature, plugging problems that frequently occur in conventionalcaustic or liquid iron based scrubbing systems are minimized in the Shell-Paques Process. Thebiologically produced elemental S actually increases the operational reliability of the system andenhances the H2S absorption.

BioreactorThe aerobic bioreactor contains Thiobacilli microorganisms that oxidize the dissolved sulfidesinto elemental S. Appropriate bioreactor internals are used to ensure complete mixing. Thevolume of the bioreactor is designed to achieve optimal activity of the biocatalyst. The exhaust airfrom the reactor can normally be emitted to the atmosphere without further treatment.

The air supply to the bioreactor must be controlled to minimize the formation of sulfate, and isautomated by a control system.

The conversion of H2S into elemental S is a biological process, and the biocatalysts periodicallyrequire nutrients to maintain good performance. The nutrients include certain salts for theirgrowth and maintenance. Extensive laboratory and field research has led to the optimisation ofthe nutrient solution and dosing rate for this process. The nutrient solution is called Nutrimix34/32 Solution and contains up to 12 different salts.

Material Safety Datasheet (MSDS) for the biocatalyst is as attached inAppendix VIISulfur Recovery

The produced elemental S is separated from the solvent in a settler. A portion of the bioreactorcontents is recycled over the settler to maintain the desired dry solid content in the system. Theelemental S slurry is then further processed in a decanter-centrifuge to obtain an S concentrationof ~50 60 wt%. The elemental sulfur typically has a purity of ~95-98% on dry basis. Therecovered water is recycled back to the process via the bioreactor.


17/25


Confidential19

Sulfur Work-Up Section

Optional equipment for upgrading of the biosulphur out of the Shell-Paques Unit to createindustrial (molten) sulphur quality is added to comply with the requirements of the RFP.

This is not part of the licensed process and further information is given inAppendix V.

Thermal Oxidizer (TOx)/IncineratorThe purpose of the Thermal Oxidizer/Incinerator is to combust the remaining sulphur speciesfrom the main processes of the BSRU

The treated gas from the Shell Paques absorber and the Bioreactors are sent directly to the TOx,where it is combusted along with the offgas streams from units outside the AGTU. The TOxoxidizes all sulphur compounds and hydrogen in the gas at ~850 C in the presence of a surplusof air to SO2and CO2.

The gas streams are heated to ~ 850C in the TOx mixing chamber. Fuel gas is combusted withair to provide the high temperature required. There are two air lines to the TOX, the primary airto the TOX burner to combust all of the fuel gas and the secondary air to the TOX mixingchamber to ensure that there is sufficient O2at the outlet (greater than 2 %v) to oxidise all of thesulphur compounds.

The SO2off-gas from the TOx is routed to the vent stack.

4.2 Process Chemistry

In the Shell-Paques Process absorber, H2S is removed from the sour gas by the alkaline scrubbing solutionin the absorber, which is maintained at a pH of ~8-9. The absorption of H2S proceeds according to thefollowing reaction:

OHNaHSNaOHSH 22 ++

In the above reaction, alkalinity is consumed. This alkalinity consumption is compensated by the oxidationof H2S to elemental sulfur, which proceeds under oxygen controlled conditions according to the followingreaction:

NaOHo

SONaHS ++ 2

In the Shell-Paques Process, the Thiobaccilli biocatalyst oxidizes the H2S to elemental sulfur. Thebiocatalyst is highly resistant to varying process conditions.

A small part of the dissolved sulfide will be oxidized to sulfate according to the following side-reaction:

424242 242 SOHSONaNaHSOONaHS ++

A small amount of thiosulfate is also formed. As a result of this side-reaction, caustic is required toneutralize the sulfuric acid formed. A small bleed stream is typically withdrawn from the system to preventthe build-up of sodium sulfate, sodium thiosulfate, and other salts. The bleed stream, which containssodium salts and some elemental S particles, is harmless and can typically be discharged without furthertreatment, depending on local environmental regulations.


The Shell-Paques Process SRU was designed to remove and recover ~25.7 MT/D of sulfur from the acidgas produced by the AGRU unit.

The Shell-Paques Process unit shall be a single train with one absorber, in which the AGRU Acid Gas istreated counter-currently over a three-packed bed configuration. The absorber has liquid and gasdistribution devices in the top and bottom and liquid and gas redistribution devices between the packedbeds. The absorber operates at low pressure so no flash vessel is required upstream of the bioreactor.

The bioreactor is a CIRCOX-type air-lift loop reactor, which consists of a tall cylindrical reactor containingmultiple internal cylinders to create distinct aerated and non-aerated zones. Lean scrubbing solution is


18/25


Confidential20

collected in the top of the bioreactor in a degassing module. The bioreactor internals are proprietary and issupplied by Paques B.V.

The sulfur settler is a Tilted Plate Settler (TPS) type, which operates continuously. Sulfur is recovered fromthe solution by gravitational settling, which produces a sulfur slurry containing ~10 wt% of solids. Theliquid overflow from the settler is low in solids content and is collected in the settler effluent tank andrecycled to the bioreactor. The TPS module in the sulfur settler is a proprietary internal that is supplied by

Paques B.V.

The sulfur dewatering unit is designed to remove the maximum sulfur load in a 24 hr/day runtime. Whennot operating at maximum load, either the feed rate to the sulfur dewatering unit can be reduced or theruntime can be shortened, the latter typically being the preferred option. The standard sulfur dewateringunit used in this technical estimate is a decanter-centrifuge type, which produces a sulfur cake with a drysolids content of ~50-60 wt%.

The bioreactor, sulfur settler, and tanks are operated at atmospheric pressure. A Vent Air Treatmentsystem can be installed if required to remove any residual H 2S present in the bioreactor exhaust air(typically < 1-2 ppmv H2S), however, it has not been included in the scope of this technical estimate.

4.4 BSRU Process Flow Diagram

Refer to Appendix I

4.5 Heat & Material Balance

Refer to Appendix II

4.6 Equipment

Equipment Summary Sheets with preliminary sizing of the main equipment items shown above are inAppendix III.

4.7 Stream Summary

The estimated stream conditions and compositions based on the design conditions (per Shell-Paques

Process train) are shown in the following tables:Table 8 Stream Conditions (per train)

Stream Flow

Temperature

C

Pressure

bara pH

DownstreamUnit (1)

Stack Gas fromIncinerator

43,064Nm3/hr 750 1.01

SO2

< 2600Nm3/hr

Environment

Sour Water 1.0 m3/hr 35 1.40 NAEffluent

Treatment Plant

Bleed 5.4 m3/hr 40 TBD 8.0-9.3Effluent

Treatment Plant

Sulfur Cake @60 wt% Solids 1656 kg/hr 40 NA 8.0-9.3

Sulphur

ProcessingSection

Notes: (1) To be confirmed during the BDP / FEED design phase.

Table 9 Vapor Stream Compositions

Stream H2S, ppmv H2O, vol%

Treated Gas H2S Absorber < 25 saturated

Vent Air Bioreactor < 1 saturated


19/25


Confidential21

Table 10 Liquid Stream & Sulfur Cake Compositions

Stream SHS-mg/l

Na+

kg/m3SO42-+ S2O32

kg/m3HCO3-+ CO32-

kg/m3

Bleed < 2 g/l


20/25


Confidential22

5. The Molecur Sieve Process


In natural gas dehydration and mercaptan removal applications with type 4A or 3A sieves, thermal swing

regenerative adsorption process is used. The water removal (4A or 3A) and mercaptan removal (5 A or 13X ) molecular sieves are used in series to achieve simultaneous dehydration and mercaptan removal in acommon vessel. Dehydration and mercaptan removal of the process gas is achieved by its passage throughone or more fixed molecular sieve bed(s). A bed is removed from adsorption service and regenerated bypassage of hot gas which desorbs and carries away the adsorbed water and mercaptans from the sieves.The regenerated bed containing small amounts of water and mercaptans (residual loading) is returned toadsorption service after cooling. In the meantime the process gas dehydration is achieved by another otherbed(s). Thus the natural gas dehydration and mercaptan removal is continuously accomplished while thebeds themselves undergo cyclic batch operations of adsorption and regeneration.

Relevant adsorption and regeneration fundamentals are discussed in greater detail below with respect todehydration molecular sieves. These fundamentals are similar and are equivalently applicable to mercaptanremoval molecular sieves as well.

Adsorption

In adsorption, gas flows usually from top to bottom of a regenerated bed. During the course ofadsorption two zones will develop. The bed at the top will be saturated with water under the feedconditions of temperature, pressure and water concentration and is called the Saturation Zone(SZ). No water adsorption takes place in the saturation zone.

A finite part of the bed below the saturation zone is engaged in dehydrating the gas from feedwater concentration (wet) to effluent water concentration (dry), called the Mass Transfer Zone(MTZ). Correspondingly, the sieve loading in the mass transfer zone progressively drops fromsaturation level at top to rest loading at bottom.

With time, the saturation zone gets longer and moves downward. The length of the mass transferzone, on the other hand, remains constant for the given application. The mass transfer zone,however, moves down with the same speed as the elongation of the saturation zone. This speed isdirectly related to the rate of water removed from the feed gas. The bed below the mass transferzone is potentially active but takes no part in dehydration. In general, the length of the mass

transfer zone in natural gas dehydration is a function of the molecular sieve grade, gas superficialvelocity and water concentration in feed. In normal operating range, temperature and pressurehave little influence.

The adsorption step should be terminated before imminent breakthrough to allow a reliableoperation which will meet the required specification. In doing so, a non-utlized zone is created, aspresented in Figure V.


21/25


Confidential23

Saturated Zone (SZ)

Mass transfer or

chemical reaction

zone (MTZ/CZ)

Contaminant conc. in process stream

Directionof the flow

ProductSpec.

FeedConcentration

Non-utilised zone (NZ)

a) The saturated zone (SZ) wherein the

adsorbent has achieved its maximum

loading and the concentration of thecontaminant in the process stream does not

change.

b) The mass transfer or chemical reaction

zone (MTZ/CZ) wherein the adsorbent is

only partially loaded and the contaminant

level drops from its feed concentration

down to the product level.

c) The non-utilised zone (NZ) wherein both

concentration and adsorbent loading

changes are negligible.

Figure V Bed Zones

Regeneration

The objective of regeneration is to strip off the adsorbed impurities from the bed, after it hasbeen taken out of adsorption service. This is conveniently done by passage of hot gas and thencold gas through the bed. Water stripped off by the hot gas is condensed and disposed of.

The hot regeneration gas serves two important purposes: provide heat to desorb water and act ascarrier gas to carry away the desorbed impurities, thus enabling deep regeneration. Theregeneration is carried out at the normal operating pressure, using a slip stream of the driedproduct gas supplied counter-currently, based on the low water content specification.

Heating gas temperatures of 320C is required for 4A molecular sieves and is dictated by the

thermal stability limitations of these sieves. Lower temperatures are impractical from strippingkinetics point of view and may lead to less efficient removal.

At the end of heating step and before the bed is returned into service, it is necessary to cool thebed to restore its adsorption capacity. This is done by continuing the passage of regeneration gaswithout the supply of heat. This counter-current dried gas cooling is adequate in dehydrationapplications and has an advantage of valving simplicity and "thermal pulse", in which the initialpart of the cooling step also achieves some stripping due to hot cooling outlet gas.

For both the heating and cooling steps the rise and fall of gas temperature (at the start of heatingand cooling steps respectively) is controlled to minimise thermal fatigue stresses of the steel.

The gas outlet temperature is expected to come to within 15 - 20C of the inlet temperature at theend of heating and cooling steps. While the shape of the outlet heating gas temperature varieswidely from application to application. The presence of a plateau (at approx. 150C) is sometimesreported. This can be attributed to bulk desorption of water.


22/25


Confidential24

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

0 1 2 3 4 5 6 7 8 9 10 11

time from start of regen. [ hour ]

temperature[C]

heating cooling stand-by

Figure 3 Typical temperature profile for a type 4A mol sieve dehydration unit

Water is typically desorbed in the "flat" peak and the peak flow rate is a rule of thumb 3 timesthe average stripping rate . It is important to realise that during the initial part of the heatingstep, free water can be formed in the upper section of the bed and on the inside of the topdome of the vessel. This is because these parts offer relatively cold surfaces for moisture inregeneration gas to condense. Later in the heating step the condensed water is re-vaporised, asthe temperature climbs up.

Ageing of Mol sieveThe deactivation rate of molecular sieves as a function of number of regenerations. And molseive units are generally sized for 3 years lifetime


The treated gas from the Acid Gas Removal Unit (AGRU, U-1000) leaves at 21 C and is passed overmolecular sieve beds, removing the remaining mercaptan content and water to meet the sales gas

specification.The recommended adsorbent for dehydration is 4A molecular sieve and the additional bedfor mercaptan removal can use either 5A or 13X molecular sieves.

Each molecular sieve bed can be completely isolated from the process to allow molecular sieve change outduring operation.

Two beds operate in parallel in adsorption mode and one bed operates in regeneration mode. Eachmolecular sieve bed cycles consecutively through adsorption, heating, and cooling modes under control ofa sequence control system. During the adsorption, gas flows downwards through the bed; during theheating and cooling stages, gas flows upwards through the bed. The gas leaving the molecular sieveadsorbers is split into three streams which are:

a) as sales gasb) fuel gas supplyc) regeneration gas


23/25


Confidential25

The regeneration gas, is routed to the regeneration-gas heater (E-1301), where it is heated and subsequentlyused for regeneration of the regenerating bed. The slipstream is normally heated to 320C, with amaximum of 350C in E-1301,using hot oil.The regeneration-gas flow rate is constant and temperaturecontrol of this gas stream is achieved by bypassing E-1302. The heated gas stream passes upwards throughthe molecular sieve bed, thereby driving the water and mercaptans from the molecular sieves.

After passing through the bed in heating mode, the regeneration gas is cooled by air cooler E-1302.Condensed water, which also may contain co-adsorbed hydrocarbons, is knocked out in vessel V-1301 androuted to water effluent treating/re-injection. The gas leaving V-1301 still contains the mercaptansremoved from the adsoprtion beds and is recovered by the regen Regen gas Gas absorberAbsorber, C-1302, which is a Sulfinol-X absorber integrated with the rest of the AGRU. The desulphurized regen gaspasses through the regen gas knockout vessel, V-1302 and is then compressed by a centrifugal compressorK-1301 and routed back to the inlet of the treated gas cooler (E-1005) in the AGRU where it combineswith the feed gas.

5.3 MSU Process Flow Diagram

Refer toAppendix I

5.4 Heat & Material Balance

Refer to Appendix II

5.5 Equipment

Equipment Summary Sheets with preliminary sizing of the main equipment items shown above are inAppendix III.

5.6 Utility, Catalyst & Chemical Requirements

The following utilities, catalyst/adsorbent and chemicals are required for the MSU

Electricity for motor drives of air cooler and any associated pumps;

Nitrogen for purging

Instrument Airfor actuation of the valves

Heating Mediumfor actuation of the valves

The estimated utility consumption is shown in Table 12.

Table 12 Operating & Equipment Parameters

Utility Unit Consumption

4A Adsorbent m3 29.5

5A/13X Adsorbent m3 18.5

Heating Duty kW 875

Electrcity kW 520

Nitrogen Intermittent use

Notes: (1) Adsorbent volumes are based on the total requirement for 3 beds, rounded upto the nearest 0.5 m3 and does not contain any volume for contingency (e.g breakageduring shipping)


24/25


Confidential26

Appendices

The following Appendices are supplied as attachements to this proposal

Appendix I Simplified Process Flow Diagrams

Appendix II Heat & Material Balances

Appendix III Equipment Summary Sheets

Appendix IV General Information on Biosulphur

Appendix V Biosulphur Workup Options

Appendix VI Sulphur Melter Information

Appendix VII Material Safety Data Sheets

Appendix VIII Reference Lists


25/25

Tekimkmkl'k

Documents

Transcript of Tekimkmkl'k