process analytics in claus

7/23/2019 Process Analytics in Claus

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With the increasing environmentalconcerns, sulfur recoveryhasbecome one of the leading issues inemissions reduction in industry.For gas processing and refining facili-ties sulfur recovery requirementsrange from 97.5% to 99.8% .The well known Claus Process withsome form of tailgas cleanup orspecial processing capability can meetthis requirements with the help ofhigh performance process analytics.

Siemens Sensors and Communica-tion, a leader in process analytics, hasproven over decades its competenceto plan, engineer, manufacture,implement and service analyzer sys-tems for use in Claus plants.

This Case Study provides details aboutthe Claus process and related analyzertasks.

Sulfur recovery

The relatively high sulfur content ofthe still available crude oil and natu-ral gas reserves and the more strin-gent standards for sulfur emissionsfrom oil, gas, and chemical process-ing facilities demand reliable andcost effective technologies for sulfurrecovery. Sulfur recoveryrefers tothe conversion of hydrogen sulfide(H2S) as byproduct of natural gasplants and crude oil refineries to ele-mental sulfur.The most common conversionmethod is the Claus Process.Approximately 90 to 95% of recov-ered sulfur is produced by the Clausprocess.First invented over 100 years ago,the Claus Process has undergone acontinuous evolution in attempts toincrease the sulphur recovery effi-ciency of the process.In the 1930s, a thermal stage wasadded to the two catalytic stages,which increased the recovery effi-ciency from 95% to approximately97%. In the 1970s, a hydrogena-tion/hydrolysis plus amine separa-tion was added to treat the tail gasfrom the Claus process. In 1988,SuperClaus was introduced, whichadded a selective oxidation reactorto the end of the Claus process,increasing the efficiency to approxi-mately 99%.

Sulfur recovered in Claus plants isused for manufacturing e. g. ofmedicines, cosmetics, fertilizers andrubber products.

Chemical analysis of the processstreams is required for controllingand monitoring the Claus process.Process gas chromatographytogether with continuous gas ana-lyzers has proven to be a very reli-able and cost efficient method.Siemens Sensors and Communica-tion provides efficient solutions forthis demanding analysis tasks.

Process Analytics in Claus Plants


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The Claus Process

Claus Process forH2S removalHydrogen sulfide (H2S) is commonlyfound in natural gas and products fromoil refineries, especially if the crude oilcontains a lot of sulfur compounds.

Typical sources are

Gas from natural gas fields

Sour refinery gas

Sour water stripper gas

Sour gas from chemical plant

Sour gas from salt production plant Sour gas from coal gasification

H2S is a smelly, corrosive, highly toxicgas, which also deactivates industrialcatalysts. Therefore it is converted tonon-toxic and useful elemental sulfurat almost all locations where it is pro-duced. The process of choice is theClaus Sulfur Recovery Process.

Most sulfur plants comprise two conver-sion stages: one non-catalytic, thermalconversion stage and two or more cata-lytic conversion stages in series (Fig.1).The Claus reaction is highly exothermic,

releasing a great deal of heat energythat can be recovered by generatingsteam in heat exchangers following theconversion stages.

Thermal conversion stage

The H2S containing gas (SWS acid gas,amine acid gas) is fed to the ThermicConverter where it is partially oxidizedwith air in a reaction furnace at hightemperatures (1000 to 1400 C).Combustion air is fed to the burner,with the amount of air controlled tocombust only 1/3 of the H2S to SO2(reaction 1). 2/3 of the H2S remain unre-acted due to lack of oxygen. Addition-ally air may be fed to combust alsoammonia and hydrocarbons enteringwith the acid gas streams.

The furnace acts as a thermal conver-sion stage, as the high temperature inthe furnace will cause part of the H2Sand SO2 to combine via reaction (2).Thus sulfur is formed, but some H2S andSO2remain unreacted.

Catalytic conversion stage

The hot combustion products from thefurnace enter the waste heat boiler andare partially cooled by generatingsteam. The gas is further cooled in thefirst sulfur condenser, to condense thesulfur formed in the furnace, whichis then separated from the gas anddrained to a collection pit.The gas leaving the sulfur condenser isheated again to avoid forming liquidsulfur in the downstream catalyst bedand enters the first catalytic converter.There, the remaining H2S reacts withthe SO2at lower temperatures over aconversion catalyst (mostly alumina-based) to make more sulfur. Unfortu-nately the reaction does not go to com-pletion even with the best catalyst.Typically, about 70% of the H2S and SO2in the gas will react via reaction (2) toform sulfur, which leaves the reactorwith the gas as sulfur vapor.The hot gas is cooled in the second sul-fur condenser, where more sulfur isformed, separated, and drained to thecollection pit. This is usually followed byone or two more heating, reaction, andcondensing stages to react most of theremaining H2S and SO2.

Fig. 1: Generic flowsheet of the Claus Process, simplified


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The Claus Process (ctd.)

Tailgas treatment stage

A small amount of H2S and SO2remainsin the tail gas. The tailgas is routed toeither a Tailgas Cleanup Unit (ModifiedClaus Process with Tailgas Cleanup) forfurther processing, or to a Tailgas Ther-mal Oxidizer to incinerate all of the sul-fur compounds in the tailgas to SO2before dispersing the effluent to theatmosphere.

Claus Process versions

Increasingly stringent standards for sul-fur emissions have caused further

developments of the Claus Process withthe objective of higher recovery rates.Table 1 shows a selection.

Analysis TasksThe continuous development of sulfurrecovery processes has increased thedemand in efficient process analyticaltechniques for process and emissioncontrol. Stringent requirements areplaced on the process analyzers andespecially on the tail gas analyzer todetermine process parameter airdemand.

Various measuring points with differenttasks are located along the processroute (Fig. 1 and table 2). The mostimportant task is the determination ofthe concentrations of hydrogen sul-phide (H2S) and sulphur dioxide (SO2)in the desulfurized gas (tail gas, MP 5 inFig. 1) and following from this the cal-culation of the H2S/SO2ratio.

This ratio is the only parameter fordirect process control through theamount of combustion air fed to the fur-nace of the thermal stage. The ratioshould be kept to 2:1 to run the processat optimum efficiency.

ChallengesThere are two major analysis challengesthat must be considered when choosingthe measuring principle of the analyzer:

Other gaseous components may bepresent in the sample gas such as

CO2, HC, COS and CS2with varyingconcentration levels.So the analyzer principle should befree from cross-interferences.

The sample gas is saturated by sulfurvapor or even elemtary sulfur may beproduced that may amongst othersblock sample lines. So the entire sam-pling system must be heated to a

temperature that prevents reliablyfrom sulfur condensation.

Solution from one hand

Siemens Process Analytics is able to sup-ply turnkey analyzer systems for Clausplants including CEM system, alongwith planning, engineering, start-up,commissioning and training services.

Sampling pointSampling stream

MeasuringComponents

SuitableSiemens Analyzer

1 Process gas feed H2S, SO2, CO2HC

MAXUM ClausFIDAMAT 6

2 Inlet of first catalytic converter H2S, SO2 MAXUM Claus

3 Outlet of first catalytic converter H2S, SO2 MAXUM Claus

4 Outlet of last catalytic converter H2S, SO2 MAXUM Claus

5 Tail gas downstream the last condenser H2S, SO2

COS, CS2N2, H2O, O2

MAXUM Claus

OXYMAT 6

6 At the sulfur collection pit H2S, SO2 MAXUM Claus

7 Before / at the stack (CEM) SO2, CO, NOxO2

ULTRAMAT 6OXYMAT 6

Measurements at MP 3, 4 and 5 can be performed with just one Analyzer using sample streamswitching

Tab. 2: Analysis measuring tasks and suitable Siemens analyzers

Claus process versions (selection)

Claus Process This original Claus process uses only the catalytic reaction

ModifiedClaus Process

This process uses the additional thermal conversion stage where 1/3 ofthe H2S is converted to SO2and S. The modified Claus process is generallylimited to a sulfur recovery efficiency of 94 ... 97%. Higher recovery ratesare achieved by adding a tail gas treatment unit.

OxygenClaus Process

This process uses an air/oxygen mixture to reduce the nitrogen content inthe process flow for better plant efficiency.

Super Claus This process uses a special catalyst material in the last catalytic reactor

Fig. 2: Claus plant

Tab. 1: List of Claus Process versions


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The MAXUM edition II Claus AnalyzerSolution provider for Tail Gas Analysis

MAXUM II Claus Analyzer

MAXUM II Gas Chromatograph

MAXUM Edition II represents the toptechnology in process gas chromatogra-phy with outstanding features resultingin a high versatility to solve any givenapplication task with best possible ana-lytical results at lowest costs:

Multiple analytical tools such asovens, detectors, valves etc.

Single and independent dual ovenconcept for minimizing the number

of analyzers Airbath and airless oven to reduce

utility costs

Valveless column switching to reducemaintenance

Parallel chromatography for fastanalysis, system simplification andincrease of reliability

Complete networking capabilities andpowerful processing software.

MAXUM II Claus Analyzerfor tail gas analysis

Process gas chromatography has gener-

ally proven to be a reliable and costeffective method to solve the demand-ing task of Claus tail gas analysis.Especially MAXUM II, because of its dou-ble oven concept and outstanding mod-ularized design, can be designed a veryefficient Claus gas analyzer.

The two separately heatable ovens withairless mass heating (fig. 4) are used toclearly separate the functionalitiesrequired for the analysis task:

The right oven contains the analysissystem including the separating col-umns, circuit and detectors,

The left oven contains sample condi-tioning, calibration media dosing andthe dosing valve. To prevent fromblockages by solid or plastic sulfur thesample line is purged with nitrogen orair.

Heated sampling and dosing

Sulfur becomes solid or semiliquidwhen the sample temperaturedrops below 135 C or rises above150 C. Therefore the sample tem-perature must be kept at 145 Ccontinuously from the samplingpoint to the analyzer.

Steam heated sampling lines (tube-in-tube technology, Fig. 5) and sample

conditioning components mounted in ahigh temperature environment (leftoven) meet this requirement .

User Benefits Proven technology with high reliabil-

ity, long term stability

Reliable operation through backpurgeto clean analyzer and sample lines incase of temperature drop or powerfailure and during maintenance

Easy operation, remote operation

Low maintenance efforts

No UV-lamp, long-time stability,

no expensive spare parts regularlyneeded

High accuracy through use of chro-matographic separation (no interfer-ences by sulfur, COS, CS2)

High reliability because of compre-hensive self diagnosis

Extended analysis to other compo-nents possible such as N2, CO2, COS,H2O

Network with other GCs on plant

Very cost efficient

Fig. 3: MAXUM ed. II Claus analyzer

Fig. 4: MAXUM ed. II Claus analyzer, open

(covered by S film)

Fig. 5: Tube-in-Tube technology (left) and isolated sampling lines (right)


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Siemens Process Analytics at a glanceProducts

Siemens Process AnalyticsSiemens Process Analytics is a leadingprovider of process analyzers and pro-cess analysis systems. We offer our glo-bal customers the best solutions fortheir applications based on innovativeanalysis technologies, customized sys-tem engineering, sound knowledge ofcustomer applications and professionalsupport. And with Totally IntegratedAutomation (TIA). Siemens ProcessAnalytics is your qualified partner forefficient solutions that integrate pro-

cess analysers into automations sys-tems in the process industry.

From demanding analysis tasks in thechemical, oil & gas and petrochemicalindustry to combustion control inpower plants to emission monitoring atwaste incineration plants, the highlyaccurate and reliable Siemens gas chro-matographs and continuous analyserswill always do the job.

Siemens process Analytics offers a wideand innovative portfolio designed tomeet all user requirements for compre-hensive products and solutions.

Our ProductsThe product line of Siemens ProcessAnalytics comprises extractive and in-situ continuous gas analyzers (fig. 6 to9), process gas chromatographs (fig. 10to 13), sampling systems and auxiliaryequipment. Analyzers and chromato-graphs are available in different ver-sions for rack or field mounting, explo-sion protection, corrosion resistant etc.

A flexible networking concept allowsinterfacing to DCS and maintenancestations via 4 to 20 mA, PROFIBUS,

Modbus, OPC or industrial ethernet.

Fig. 6: Series 6 gas analyzer (rack design)

Fig. 7: Product scope Siemens Continuous Gas Analyzers

Extractive Continuous Gas Analyzers (CGA)

ULTRAMAT 23 The ULTRAMAT 23 is a cost-effective multicomponent analyser for themeasurement of up to 3 infrared sensitive gases (NDIR principle) plusoxygen (electrochemical cell). The ULTRAMAT 23 is suitable for a widerange of standard applications. Calibration using ambient air eliminatesthe need of expensive calibration gases.

CALOMAT 6/62 The CALOMAT 6 uses the thermal conductivity detection (TCD) methodto measure the concentration of certain process gases, preferably hydro-gen.The CALOMAT 62 applies the TCD method as well and is speciallydesigned for use in application with corrosive gases such as chlorine.

OXYMAT 6/61/64 The OXYMAT 6 uses the paramagnetic measuring method and can beused in applications for process control, emission monitoring and qualityassurance. Due to its ultrafast response, the OXYMAT 6 is perfect formonitoring safety-relevant plants. The corrosion-proof design allowsanalysis in the presence of highly corrosive gases.

The OXYMAT 61 is a low-cost oxygen analyser for standard applications.The OXYMAT 64 is a gas analyzer based on ZrO2technology to measuresmallest oxygen concentrations in pure gas applications.

ULTRAMAT 6 The ULTRAMAT 6 uses the NDIR measuring principle and can be used inall applications from emission monitoring to process control even in thepresence of highly corrosive gases.ULTRAMAT 6 is able to measure up to 4 infrared sensitive components ina single unit.

ULTRAMAT 6 /OXYMAT 6

Both analyzer benches can be combined in one housing to form a multi-component device for measuring up to two IR components and oxygen.

FIDAMAT 6 The FIDAMAT 6 measures the total hydrocarbon content in air or even inhigh-boiling gas mixtures. It covers nearly all requirements, from tracehydrocarbon detection in pure gases to measurement of high hydrocar-bon concentrations, even in the presence of corrosive gases.

In-situ Continuous Gas Analyzer (CGA)

LDS 6 LDS 6 is a high-performance in-situ process gas analyser. The measure-ment (through the sensor) occurs directly in the process stream,no extractive sample line is required. The central unit is separated fromthe sensor by using fiber optics. Measurements are carried out in real-time. This enables a pro-active control of dynamic processes and allowsfast, cost-saving corrections.

Fig. 8: Series 6 gas analyzer (field design) Fig. 9: LDS 6 in-situ laser gas analyzer


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Siemens Process Analytics at a glanceProducts (continued) and Solutions

Fig. 10: MAXUM edition II Process GC

Fig. 11: MicroSAM Process GC

Fig. 12: SITRANS CV Natural Gas Analyzer

Our solutionsAnalytical solutions are always drivenby the customers requirements. Weoffer an integrated design covering all

steps from sampling point and samplepreparation up to complete analysercabinets or for installation in analysershelters (fig. 14). This includes also sig-nal processing and communications tothe control room and process controlsystem.

We rely on many years of world-wideexperience in process automation andengineering and a collection of special-

ized knowledge in key industries andindustrial sectors. We provide Siemensquality from a single source with a func-tion warranty for the entire system.

Read more in "Our Services.

Fig. 14: Analyzer house (shelter)

Process Gas Chromatographs (Process GC)

MAXUM edition II MAXUM edition II is very well suited to be used in rough industrial envi-ronments and performs a wide range of duties in the chemical and pet-rochemical industries and refineries.

MAXUM II features e. g. a flexible, energy saving single or dual oven con-cept, valveless sampling and column switching, and parallel chromatog-raphy using multiple single trains as well as a wide range of detectorssuch as TCD, FID, FPD, PDHID, PDECD and PDPID.

MicroSAM MicroSAM is a very compact explosion-proof micro process chromato-graph. Using silicon-based micromechanical components it combinesminiaturization with increased performance at the same time.

MicroSAM is easy to use and its rugged and small design allows mount-ing right at the sampling point. MicroSAM features drastically reducedcycle times, provides valveless sample injection and column switchingand saves installation, maintenance, and service costs.

SITRANS CV SITRANS CV is a micro process gas chromatograph especially designedfor reliable, exact and fast analysis of natural gas. The rugged and com-pact design makes SITRANS CV suitable for extreme areas of use, e.g. off-shore exploration or direct mounting on a pipeline.

The special software "CV Control" meets the requirements of the naturalgas market, e.g. custody transfer.

Fig. 13: Product scope Siemens Process Gas Chromatographs


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Siemens Process Analytics at a glanceSolutions (continued) and Services

Our solutions ...

Analyzer networking fordata communication

Engineering and manufacturing of pro-cess analytical solutions increasinglycomprises "networking". It is getting astandard requirement in the processindustry to connect analyzers andanalyzer systems to a communicationnetwork to provide for continuous anddirect data transfer from and to theanalysers.The two objectives are (fig. 16):

To integrate the analyzer andanalyzer systems seamless into thePCS / DCS system of the plantand

To allow direct access to the analyzersor systems from a maintenancestation to ensure correct and reliableoperation including preventive orpredictive maintenance (fig.15).

Siemens Process Analytics provides net-working solutions to meet the demandsof both objectives.

Our ServicesSiemens Process Analytics is your com-petent and reliable partner world widefor Service, Support and Consulting.

Our rescources for that are

ExpertiseAs a manufacturer of a broad variety

of analyzers, we are very much expe-rienced in engineering and manufac-turing of analytical systems andanalyzer houses.We are familiar with communicationnetworks, well trained in service andmaintenance and familiar with manyindustrial pro cesses and industries.Thus, Siemens Process Analytics ownsa unique blend of overall analyticalexpertise and experience.

Global presenceWith our strategically located centersof competence in Germany, USA,Singapore, Dubai and Shanghai, weare globally present and acquaintedwith all respective local and regionalrequirements, codes and standards.All centers are networked together.

Fig. 16: Networking for DCS integration and maintenance support

Fig. 17: Portfolio of services

Fig. 15: Communication technologies


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Siemens Process Analytics at a glanceServices, continued

Our Services ...

Service portfolio

Our wide portfolio of services is seg-mented into Consulting, Support andService (fig. 17 to 18). It comprisesreally all measures, actions and advisesthat may be required by our clientsthroughout the entire lifecycle of theirplant. It ranges from site survey toinstallation check, from instruction ofplant personnel to spare part stock man-agement and from FEED for ProcessAnalytics (see below) to internet-basedservice Hotline.

Our service and support portfolio(including third-party equipment) com-prises for example:

Installation check

Functionality tests

Site acceptance test

Instruction of plant personnel on site

Preventive maintenance

On site repair

Remote fault clearance

Spare part stock evaluation

Spare part management

Professional training center

Process optimisation

Internet-based hotline

FEED for Process Analytics

Technical consullting

FEED for Process Analytics

Front End Engineering and Design(FEED) is part of the planning and engi-neering phase of a plant construction ormodification project and is done afterconceptual business planning and prior

to detail design. During the FEED phase,best opportunities exist for costs andtime savings for the project, as duringthis phase most of the entire costs aredefined and changes have least impactto the project. Siemens Process Analyt-ics holds a unique blend of expertise inanalytical technologies, applicationsand in providing complete analyticalsolutions to many industries.

Based on its expertise in analytical tech-nology, application and engineering ,Siemens Process Analytics offer a widescope of FEED services focused on anal-ysing principles, sampling technologies,application solutions as well as commu-nication system and given standards (allrelated to analytics) to support our cli-ents in maximizing performance andefficiency of their projects.

Whether you are plant operators orbelong to an EPC Contractor you willbenefit in various ways from FEED forProcess Analytics by Siemens:

Analytics and industry know howavailable, right from the beginningof the project

Superior analyzer system perfor-mance with high availability

Established studies, that lead to

realistic investment decisions Fast and clear design of the analyzer

system specifications, drawings anddocumentation

Little project management andcoordination effort, due to oneresponsible contact person andless time involvement

Additional expertise on demand,without having the costs, the effortand the risks of building up the capac-ities

Lowest possible Total Costs of Owner-ship (TCO) along the lifecycle regard-

ing investment costs, consumptions,utilities supply and maintenance.

Fig. 18: Portfolio of services provided by Siemens Process Analytics


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Case Study

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Siemens Process Analytics - Answers for industry

If you have any questions, please contact your local sales representative or any of the contact addresses below:

Siemens AGA&D SC PA, Process Analyticsstliche Rheinbrckenstr. 5076187 KarlsruheGermany

Phone:+49 721 595 3829Fax: +49 721 595 6375E-mail:[email protected]/prozessanalytics

Siemens Ltd., ChinaA&D SC, Process Analytics7F, China Marine TowerNo.1 Pu Dong AvenueShanghai, 200120P.R.China

Phone:+86 21 3889 3602Fax: +86 21 3889 3264E-mail: [email protected]

Siemens Energy & Automation Inc.7101 Hollister RoadHouston, TX 77040USA

Phone:+1 713 939 7400Fax: +1 713 939 9050E-mail: [email protected]

www.siemens.com/processanalytics

Siemens LLCA&D 2B.PO Box 2154,Dubai, U.A.E.

Phone:+971 4 366 0159Fax: +971 4 3660019E-mail: [email protected]/processanalytics

Siemens Pte. LimitedA&D SC PS/PA CoC60 MacPherson RoadSingapore 348615

Phone:+65 6490 8728Fax: +65 6490 8729E-mail: [email protected]

www.siemens.com/processanalytics

process analytics in claus

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