
Agenda

Summary…Eight SRU-TGTU analyzer tags with detailed discussion of:

Acid Gas Feed Forward (Total HC, BTEX, H2S, NH3,CO2, H2O)

Tail gas (H2S, SO2)

After acid gas is introduced when can the analyzer be put in control ?

Control signal, over range, best practices

TGTU (H2, H2S, COS, CS2)

Quench or Absorber where to place the H2

Absorber outlet; H2S/COS/CS2 ranges

Sulfur Pit Gas Analyzer (H2S, SO2)

What constitutes abnormal operation conditions

O2 (start up) Analyzer (O2, CO)

2


3

SRU-TGTU Analyzer Tags


Acid Gas Analyzer

Feed Forward Control

New Analysis & Control Schemes

possibilities


Field Data / HC Process Upset

H2S swings from 83 to 87%

THC =0.2%

THC = 2.5%

12 fold > in THC

from 0.2 to 2.5%

lasting ~3 minutes


Acid Gas Analyzer

Real time analysis of acid gas using a UV-IR Analyzer

IR is to quantify the Total HC (as methane equivalent)

UV to quantify the H2S

CO2, H2O as required (ABC+)

BTEX to know when to co-fire for higher reaction furnace temperatures


Feed Forward Analysis

Actual Control Response to Hydro-Carbons (Courtesy of Jacobs Comprimo)

7


Acid Gas Analysis - Benefits

Improved control, fewer upsets, mitigation of upsets

Demonstrated improvement of ~0.5% recovery efficiency (ER)but…

More to the point it is the loss of 5% ER for 1 hour that is the benefit

Prevention of SO2 breakthrough to the TGTU

Can (should) be used for mass balance recovery efficiency calculation

The objective is to place the analyzer in cascade control

THC/BTEX Speciation is the new focus especially in ME

8


The Heated Acid Gas (HAG) Probe

Membrane for liquid ingress, no water removal, no pump

Maintained at process temp, spent sample returned back to process,

Integral process isolation valves, safety is the paramount feature

To be “ready”…Install the HAG at

Turnaround


Tail Gas Analyzer

Feed Back Control

Air Demand vs Ratio

Start Up and Shutdowns

When to put the analyzer on line

Tail Gas Analyzer

Top of the Pipe Analyzer

880 NSL

Sample Line Analyzer

900 ADA

Insulated steam

jacketed nozzle

Weather cover

for ASR

probe and jacket


Ratio vs Excess H2S vs Air Demand

Ratio is the non linear expression of 2 H2S / SO2

Excess H2S is the linear expression of

[H2S] - 2[SO2] = -1%…0…+1% H2S

Air Demand uses a scaling factor

AD{[H2S] - 2[SO2]} = -5%...0...+5% AIR

REMINDER


Controlling “Off Ratio”

To favor the TGTU with H2S

The tail gas analyzer simply measures [H2S] and [SO2]

And calculates a control algorithm….

A dumb analyzer we ask to do a smart thing

Running “Off ratio”

Typically 4:1 or 5:1 but this is just a notional value…

Perhaps better to express it as -1% air demand (~+0.2% xs H2S)

Let’s not be slave to 2:1

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Tail Gas: Process Upset & Over-Range Event


“After start up when is the

analyser put into control

mode ?” Catalyst preference for H2S over

SO2 can skew true air control.

Sulphur Experts recommends

control mode after 8 hours.

15

Putting the Analyzer in Control After Start-up

“Do you consider tail gas

analysers to be reliable ?” Thankfully yes was common

response

Responses capture the evolution

of the tail gas products.

Time for a 3rd generation.


SRU Start-up O2 /CO Measurement

• For start-ups and shut-downs

Requires excess O2 to near

stochiometric conditions of 0.1% xs air

Tunable Diode Laser (TDL) process O2

analyzer

Can monitor CO also

• A fixed (permanent) system or portable

16


TGTU Analyzer

Where to install ?

COS/CS2 analysis on top of Absorber

SO2 breakthrough analysis


Analytical Measurements on a TGTU

H2 is the critical parameter ( so please no GC - ESD analyzer)

H2S can be measured at the Quench outlet or Absorber outlet

[H2S] at Quench outlet is a measure of SRU recovery efficiency

[H2S] at Absorber outlet is a measure of absorber efficiency

COS & CS2 are secondary measurements

[COS] is indication of CoMo catalyst activity (first to breakthrough)

[CS2] is also indication of catalyst activity and contribution to emissions

SO2 can be measured at the quench inlet or outlet (not common)

pH is measured in the quench water (not addressed here)


Where to install TGTU analyzer

Installed Base of ~175 Analyzers

~140 have sample point at top of Absorber (H2/H2S)

25 of these also measure COS

8 of these also measure COS + CS2

~30 have sample point at Quench outlet (H2/H2S only)

~5 have sample point at Quench inlet (SO2 breakthrough)

Finding right balance between Analyzer complexity

and Benefit of measurement for Operations

19


SO2 0 – 100

ppm


TGTU (COS & H2S) Steady State & Upset

21

COS

H2S

H2S

COS


Sulfur at Absorber Outlet After SO2 Upset


Sulphur Pit Analyzer

The neglected one…


Sulfur Pit: Solubility of H2S in Sulfur

• Produced sulfur has 200-350 ppm

of dissolved H2S

• Spontaneous degassing and

concentration in the gas phase can

increase to explosive levels (3.5%)

• Pit gas analyzer requires same

sample integrity as tail gas

analyzer ( Sulphur Vapor )

• H2S is measured to warn of LEL,

SO2 is measured to warn sulfur fire


H2S / SO2 values

S-Tank sweep gas


Sulphur Pit High H2S & SO2 Values

(Just prior to an incident)

26

H2S

SO2 CFD modeling confirms

H2S can exist ~16x

The mean value


SRU Emission Analyzer

Mass Emission

TGTU bypass situation


Emission Analyzers

“The Color of Plumes” (courtesy of S-Experts)

White: Steam plume caused by water condensation (cold, Canada)

Bluish white: SO3 plume usually caused by high SO2 emissions

Ask analyzer techs to watch for “green slime” (chromium from 316SS + S-acid)

Orange: NOx plume

Brown: Unburned hydrocarbon / soot plume

Green: Burning H2S plume

Dual Range of SO2 if TGTU can be bypassed (Habshan 5)

Mass Emission if straight Claus SRU (no TGTU)

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Major Problems Faced

&

Solutions


What are the common problems that Operations

have with Analyzers ? • Frequent choking problems !!!

• Sampling system failure

• Temperature Impacts??

– Is it controlled at each locations with respect to sulfur dewpoint?

30

No heating/

Jacketing


Common problems …

• Frequent downtime due to maintenance issues

– Lack of SRU Analyzer trainings

– Not much experience on SRU process

– Frequent shifting/changing of site engineers

• High H2S exposure…. SAFETY : People and Environment

• Unpredicted behavior of Analyzer & readings

ex. Unit 52 at Gasco Habshan

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GASCO Habshan DCS

Tail Gas Trends


Remedies…

• Regular control visits on SRU analyzers by expert

->if problem persist more than 2 times call Manufacturer

• Sites have “generalist” analyzer tech not SRU experts (Do you have?)

• Need SRU Process Trained Analyzer Service Engineers

• Need experienced hands on CBA & other SRU process

• Your Service Staff requires periodically training and evaluation by OEM…

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Solutions for Ametek SRU analyzers in Middle East

• AIMS is our local partner having Focussed SRU experience …

• Big service team with extensive knowledge on all SRU process

analyzers

• First in kind analyzer successfully commissioned for

H2S in Lean Amine & BTEX Analyzer at GASCO Habshan

• AIMS involved with all EPC and System Integrators for

Commissioning and Start Up on AMETEK for Middle East

• Target is 100% uptime of our Analyzers at all sites in GCC

AIMS is our Sulphur Police squad, call them if problems !

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Q&A

35

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Date post:	13-Feb-2021
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2nd Annual Middle East Sulphur Plant Operations Network...

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