battling corrosion in refineries with in-line process ... · pdf filebattling corrosion in...

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Battling Corrosion in Refinerieswith In-Line Process AnalyticsIt is estimated that the global costs of refinery corrosion are in the order

of 15 billion USD annually. Even though the problem may never be fully

solved, advances in process analytics with a new generation of intelligent

pH sensors offers huge cost savings.

Complex problemThe main difficulty in combating refinery

corrosion is that the problem has not one

single source, but many. In addition, some

of the corrodents involved might interact

and increase or inhibit each other’s cor-

rosivity. Physical process conditions also

play a role; so temperature, flow, etc. have

to be taken into account, as does the refin-

ery infrastructure itself. Given the number

of variables then, it becomes clear that

corrosion is a complex issue.

SulfurBecause it provides a lower feedstock cost,

sour crude is preferred by refineries. In

sour crude sulfur is present in the form of

mercaptans, H2S, sulfide salts, elemental

sulfur and so on. Many of these species are

reactive and cause sulfide stress cracking

and sulfuric acid corrosion throughout

the refining process.

AcidityBesides sulfur, crude contains many spe-

cies that are quantified by the total acid

number (TAN) of the oil. Typically found

are naphthenic acids, which are organic,

but also mineral acids (H2S, HCN, CO2,

etc.) can be present, all of which can

contribute significantly to equipment

corrosion. Even materials suitable for sour

service do not escape damage under such

an onslaught of aggressive compounds.

Again, because of cost considerations, a

trend towards a preference for crudes with

a higher TAN is noticeable.

Petrochemical Perspectives in Liquid Process Analytics

INGOLD Leading Process Analytics

Automated cleaning and calibration system EasyClean 400

2 METTLER TOLEDO Petrochemicals News 5

Publisher / Production Mettler-Toledo AG

Process Analytics

Im Hackacker 15

CH-8902 Urdorf

Switzerland

IllustrationsMettler-Toledo AG

Viorel_dudau, Harper3d, Reflekcija,

Imdan | Dreamstime.com

Subject to technical changes.

© Mettler-Toledo AG 12/09

Printed in Switzerland.

DesaltingDesalting of the crude is the first step in

refining that has a direct effect on corro-

sion and fouling. By mixing and washing

the crude with water, salts and solids

transfer to the water phase which settles

out in a tank. An electrostatic field is in-

duced to speed up the separation of oil and

water. In this way, inorganic salts that

could cause fouling or hydrolyze and form

corrosive acids, are largely removed. Often,

chemicals are added in the form of demul-

sifiers to break the oil / water emulsion.

Other chemicals such as caustic soda are

also introduced to neutralize acidic com-

ponents. Uncontrolled feeding of caustic

can, however, have a detrimental effect

and result in a significant quantity of

contaminants ending up in downstream

processes, which may have serious conse-

quences.

DistillingEven with an efficient desalting operation,

an abundance of corrodents can still ap-

pear during downstream processing. A

good example of this is the sour water

corrosion that occurs in the crude distiller.

During the process lots of acid gases are

formed of which hydrogen sulfide is noto-

rious. Steam, which is injected into the

crude tower to improve fractionation,

condenses in the upper part of the unit.

The hydrogen sulfide dissolves in the

condensate and forms a weak acid which

is known to cause stress corrosion crack-

ing in the top section of the tower and in

the overhead condenser. This may lead to

frequent retubing of the condenser and in

severe cases to replacement of the entire

crude tower top.

In-line analysisAll the problems mentioned above, and the

costs associated with them, can be signifi-

cantly reduced by reacting to the

measurements obtained from accurate

in-line analysis of pH values.

In respect of desalting, constant in-line

monitoring of pH in the desalter water ef-

fluent allows for efficient dosing of caustic

or acid which can result in significant

cost savings. The stability of the oil /

water emulsion depends partly on pH.

Maintaining the pH of the mixture within

a certain range helps the demulsifier

chemicals in breaking the emulsion by

interacting directly with the water droplets.

The speed and quality of the separation

process can thus be improved which leads

to less water carry-over, which in turn can

result in a significant reduction in down-

stream corrosion and fouling.

Even though corrosion in the disitiller is

well known to refinery operators, effective

counter measures are not always in place.

Typically, corrosion inhibitors and lots of

neutralizers such as caustic soda or am-

monia are injected with the aim of

increasing the pH of the sour water.

Although this is an obvious response to the

problem, the cure can be worse than the

disease. The presence of various acid

gases and ammonia can result in solid

salts depositing including ammonium

bisulfide, one of the main causes of alka-

line sour water corrosion. pH levels higher

Transmitter M700

METTLER TOLEDO Petrochemicals News 5 3

Automated cleaning and calibra-tionDespite innovative design, even the best pH

electrode needs frequent maintenance. Of

any process instrument, the pH electrode

probably has the widest rangeability and

an extraordinary sensitivity that covers it.

Depending on the process application,

after a certain time in operation a calibra-

tion is required to make sure the instrument

will maintain its reliability and accuracy.

When very sour crudes are refined, or

when the overhead hydrocarbon / water

separation is not optimal, sensor mainte-

nance may be required to an extent where

it becomes problematic and the value of

the measurement is no longer considered

an asset. In such applications the imple-

mentation of an automated cleaning and

calibration system is the answer.

Proven to be of great value in numerous

“dirty” applications is METTLER

TOLEDO’s EasyClean 400 system. Fully

certified for use in hazardous areas, this

unit enables the most difficult pH mea-

surement tasks. When necessary,

EasyClean 400 pneumatically retracts

the electrode and gives it a thorough

cleaning followed by a two-point calibra-

tion, without any human intervention.

The standalone unit carries cleaning and

buffer solutions on board and requires no

more than instrument air and water sup-

plies to carry out its tasks. An extra valve

is available in case an additional cleaning

liquid is needed.

than 7.6 dramatically increase ammonium

bisulfide corrosion and by overdosing

caustic that level is easily achieved. Proper

neutralizer dosing through pH measure-

ment of the overhead condenser boot water

will not only reduce corrosion but also

reduce chemical consumption.

Most pH electrodes are not specifically

designed for refinery applications and

hence suffer from poor performance in the

presence of high sulfide levels and the

substantial hydrocarbon load. METTLER

TOLEDO’s understanding of the conditions

in petroleum refineries has led to the de-

velopment of pH electrodes specifically

designed to cope with high temperatures,

extremes of pH value and solid contami-

nants.

Xerolyt ExtraThe most common cause of sensor failure

in refineries is poisoning and fouling of

the reference electrode system. This results

in drift of the pH measurement. Oily sub-

stances and solids may coat or clog the

diaphragm of the reference junction which

obviously has a negative impact on sensor

performance as well.

METTLER TOLEDO’s InPro 4260 i pH

electrode features Xerolyt Extra solid

polymer electrolyte. The InPro 4260 i has

an open junction, which is in fact a hole

that brings the solid electrolyte in to direct

contact with the process medium. Contrary

to the miniscule capillaries of any other

type of diaphragm in conventional pH

electrodes, the diameter of the open junc-

tion is extremely large and much less

susceptible to clogging or fouling. Another

significant difference is in the choice of

polymer electrolyte. Xerolyt Extra has

been designed specifically for service in

hydrocarbon environments and provides a

strong and lasting barrier against sulfide

poisoning.

www.mt.com/pro-pH

Intelligent Sensor ManagementIn the end, all pH electrodes will show

signs of aging and performance will start

to fall below the reliability required.

METTLER TOLEDO pH electrodes with

Intelligent Sensor Management (ISM)

communicate their remaining operating

life through a digital signal that also

carries measurement values, temperature

and enhanced sensor diagnostics. Based

on actual process conditions and history,

the Dynamic Lifetime Indicator will pre-

dict when sensor replacement is due. This

is one of many interesting features of the

ISM platform that truly enables predictive

maintenance.

Lower costs and more uptimeAdvances in sensor technology and intel-

ligent automation of the measurement

system enable pH measurement in the

most challenging refinery sour water en-

vironments. When the correct equipment

is chosen, in-line pH measurement and

management facilities have proven to be

of great value in reducing plant-wide cor-

rosion and the consumption of chemicals

such as pH control reagents and corrosion

inhibitors. This not only results in signifi-

cant cost savings but also in increased

earnings through longer process uptime.

If you want to reduce the cost of corrosion

at your facility, go to:

www.mt.com/ISMpH electrode InPro 4260 i


Self-

clea

ning

pH

Sys

tem

Overcoming technical problemsHowever, there was concern that the solids

concentration in the primary clarifier was

substantially higher than in the secondary

clarifier, and whether increased mainte-

nance demands would offset any potential

benefit in chemical savings. The local

METTLER TOLEDO sales representative

acknowledged that the conditions in the

primary clarifier were likely too extreme

for unassisted pH operation, therefore re-

quiring some type of automated cleaning

system.

The selected measuring systemSince the sensor is mounted directly in the

open basin, the proposed system included

an EasyClean 100. The sprayhead

mounted on the end of an InDip housing

directs bursts of air at the head of the

electrode at programmed intervals. The

strong turbulence generated by the air jets

prevents solids and films from accumulat-

ing at the electrode surface. The timing

interval is controlled using the rinse relay

contact of the pH 2100 e 4-wire transmit-

ter, and has been set for operation every

eight hours. Completing the system, the

InPro 3250 pH electrode was selected for

its internal pressurized reference electro-

lyte, further helping to keep the reference

junction clean.

Dramatic Reductionin Maintenance and Chemical CostsThe expense of regular maintenance plus chemicals for wastewater pH

control was troubling a large US refinery. They asked METTLER TOLEDO

for a cost saving solution. The installed system has reduced both

expenses substantially.

Major US refinerOur customer is a leading international

integrated energy company and is one of

the largest refiners in the United States.

One of their refineries processes over

200,000 barrels of oil per day producing

gasoline, fuel oils and a variety of petro-

chemicals.

Challenging wastewater treatmentMany refinery operations consume large

amounts of water, resulting in millions of

gallons per day of wastewater requiring

treatment. Accepting waste from unit op-

erations throughout the refinery presents

a challenge for pH measurement as the

water contains oils, residual sulfide and

ammonia compounds, and the pH level of

effluent from different locations can be

radically different.

New pH measuring concept requestedA competitor’s pH electrode was being used

in an existing application in a secondary

clarifier following biological treatment.

Solids and film build-up on the sensor

required weekly manual cleaning. The

treatment plant operator indicated that

the ideal location for pH control would be

in the upstream primary clarifier.

Catching pH excursions earlier in the

process would provide more stable read-

ings downstream and minimize chemical

costs resulting from overdosing of lime

used for pH control.

Selecting the right sys-tem can greatly reduce your maintenance re-quirement

METTLER TOLEDO realizes that you want to keep maintenance time to a minimum while ensur-ing your pH measurement point is always operating optimally. We offer a range of pH elec-trodes, transmitters, housings and cleaning systems for use in the Petrochemical industry. Our sales representatives will en-sure you have the right systems for your processes.

Discover more at:

Best Practice

www.mt.com/pro-pH

Transmitter pH 2100 e


InPro 3250 pH electrode The InPro 3250 family is a pre-pressurized,

liquid-filled, low-maintenance pH and

temperature sensor for in-line measure-

ments in demanding applications. Its

durable design is well suited for harsh

chemical process conditions. These rug-

ged electrodes lead the industry for fast

and precise measurements. They are

available with an expanded selection of

different pH-sensitive glass membranes.

BenefitsOperational results have more than met

expectations. Electrode maintenance has

been dramatically reduced from once ev-

ery week to less than once per month, even

though the system is now located in a

much dirtier installation. The accuracy of

the real-time pH measurement has also

led to substantial savings on chemical

costs.

EasyClean cleaning systemThe EasyClean 100 system is designed to

provide completely automatic sensor rins-

ing. It can be used with a stationary

InDip housing with a sprayhead for open

tank and basin applications. The

EasyClean 150 can use either water rins-

ing or compressed air to create turbulence

to prevent stubborn build-up.

pH electrode InPro 3250

www.mt.com/pro-pHwww.mt.com/EasyClean

pH 2100 e transmitterThe pH 2100 e transmitter is a proven high

performance transmitter that can be used

in the simplest or most demanding of

applications. Available in either 4-wire or

2-wire versions, this enhanced pH trans-

mitter line offers superior performance,

advanced sensor and transmitter diagnos-

tics and leading edge functionality.

To reduce maintenance and chemical

costs in your refinery, go to:

Schema of a typical automated loop

Sprayhead for InDip housing ensures a proper cleaning

Power in Power in

Transmitter EasyClean 100


O 2 G

as M

easu

rem

ent

This technology, with a proven industrial

track record due to its simplicity and rug-

gedness, is ideally suited for the in-situ

measurement of gaseous oxygen.

METTLER TOLEDO offers a comprehen-

sive range of amperometric systems with

sensors for wide application coverage, re-

tractable housings for sensor extraction

without process interruption, and trans-

mitters for signal conversion and

connection to process control systems

using HART®, FOUNDATION fieldbus™

or PROFIBUS®. Naturally, the complete

measurement system is available with

ATEX Zone 0 / FM Class 1 Div 1 approval if

required.

Amperometric sensors can be maintained

in two minutes, with minimum impact

on your running process. All that is re-

quired is to replace the membrane body

and fill it with fresh electrolyte solution.

Subsequent calibration can be performed

on site using air as a calibration gas.

Measure Oxygen Where it Really MattersDirectly in Your ProcessPerformance of gaseous oxygen measurement is now redefined with

METTLER TOLEDO’s amperometric systems. They not only allow reliable

and stable measurement, they are inexpensive to maintain and, what’s

more, do not require any gas sampling system.

Unwanted oxygenOxygen levels in industrial processes are

heavily controlled to contain the risk of

explosion of flammable liquids and dusts,

as well as to protect products against oxi-

dation. Not only is oxygen monitoring a

critical issue in transport systems, storage

tanks or centrifuges, it can also nega-

tively affect the yield of a chemical

reaction in a vessel.

Many solutions – which is best?When selecting a vendor for a measure-

ment system, technologies and solutions

abound, but in many cases a trade-off

exists between sufficient performance and

reliability, and reasonable maintenance

effort and system availability. In order to

function correctly, paramagnetic systems

need to protect the measurement cell from

heat, moisture and / or corrosive gases.

However, the more instruments there are

between the process and the sensor, the

longer the response time will be and the

higher the probability of system failure.

Amperometric: simple and reliableLooking at the field of dissolved oxygen

measurement however, membrane-based

amperometric sensors using the Clark

principle offer an alternative. For decades

they have demonstrated optimum perfor-

mance in a wide range of applications

ranging from fermentation processes in

breweries, in biopharmaceutical indus-

tries or in chemical process applications.

www.mt.com/o2-gas

Intelligent sensors for smart processesAll amperometric sensors from METTLER

TOLEDO are available in digital versions

equipped with Intelligent Sensor

Management (ISM) technology. With the

Plug and Measure feature, pre-calibrated

sensors can be immediately used in the

process, minimizing the time necessary

for maintenance and without the need for

specialist know-how. Additionally, ISM

sensors have built-in self-diagnostic

abilities in order to detect early signs of

failure such as low electrolyte levels, and

alert users before measurement quality or

process availability is impacted.

If you want to save costs on O2 measure-

ment at your facility, go to:

www.mt.com/ISM

F O2

Paramagnetic system

N2 in

METTLER TOLEDO solution

The sample path through a The METTLER TOLEDO solution paramagentic system is long and slow. measures directly in the vessel – immediately.


Cabl

eles

s So

lutio

n

tion. It is also the perfect answer for

remote monitoring tasks.

The W100 supports ISM sensors for pH, DO

as well as 4-E conductivity, which are

compatible with the advanced transmitter

line M400 or the value transmitter line

M300.

Additional benefits of the cableless solu-

tion include the long battery lifetime of up

to 6 months, and the communication

range of up to 150 meters.

Discover more at:

Tricky Sensor Installation Point?Go Cableless!Proper wiring between sensor and transmitter can be very costly, especially

in locations with limited access or where moving parts can be a hazard.

The cableless solution W100 gives you the option to solve expensive and

challenging installation conditions at a very reasonable cost.

No more cablesWith the W100, METTLER TOLEDO offers

an innovative solution for cost-intensive

measurement point installations. Based

on reliable and industry-proven wireless

technology (according to IEEE802.15.4),

the W100 replaces the cable between

METTLER TOLEDO Intelligent Sensor

Management (ISM) sensors and the

transmitter, and provides bi-directional

digital data transfer with full calibration

and diagnostics functionality.

Real-time monitoring of the measurement

value as well as auto-recognition of the

sensor is ensured. Additionally, the W100

convinces with its very simple one button

operation, which is also the basis for the

easy pairing between transmitter and

sensor. Thanks to the LED display, the

state of the W100 can be recognized at a

glance. Installation at existing ISM mea-

suring points is simple as there is no need

to change any transmitter settings.

For many applicationsSince there is no cable to be laid, the sys-

tem offers great advantages in applications

where high installation costs due to

physical barriers or contamination risks,

exist. Also, in applications where the

measuring point is needed only temporar-

ily, where the installation of the sensor

has to be changed several times, or where

the sensor is mounted on a moving part,

the W100 is a highly cost-efficient solu-

Stay one step ahead of maintenance with ISM

A METTLER TOLEDO ISM mea-suring system with the W100 will not just save on installation costs; ISM also reduces the maintenance and calibration effort to a mimimum. This con-siderably improves process reliability, productivity and sys-tem availability.

Find out how ISM can help you, at:

Best Practice

www.mt.com/ISM

www.mt.com/W100


Com

preh

ensi

ve W

ebsi

te The Information you Want is at www.mt.com/pro

The METTLER TOLEDO Process Analytics web-site contains a vast amount of up-to-date information on all our products and services.

Content is localized for your country and tailored to suit your selections.

Simple layout allows you to quickly find the infor-mation and features you are looking for.

n Learn about our most recent product develop- ments

n Register for free webinars

n Request further information on products and services

n Obtain a quote quickly and easily

n Download our latest white papers

n Read case studies relevant to your industry

n Access buffer and electrolyte solution certificates

n and more...

A typical Product page: with Features

and Benefits and quick access to rele-

vant application information,

related products and downloads


The Information you Want is at www.mt.com/pro

Search by Product or by Application n Read the latest product news

n Access our Newsletter archive

n Find out when our next Trade

Show or Exhibition is in your

area

n Register for free webinars

presented by our industry

experts

n Download our White PapersApplication pages help guide you to the

products that are right for your processes


Plug and Measure

Inte

lligen

t Sen

sor M

anag

emen

t Intelligent Sensor Management Reduces Life Cycle Costs and Improves Process Safety

Intelligent Sensor Management (ISM)ISM reduces the installation, maintenance and calibration effort for METTLER TOLEDO’s digital sensors to a minimum. This considerably im-proves process reliability, productivity and system availability.

Reliable installationDigital communication between sensor and transmitter means signal is always reliable and unaffected by moisture.

Intelligence – starts in the headISM sensors are equipped with integrated elec-tronics in the sensor head that store all relevant sensor parameters and includes algorithms for enhanced sensor diagnostics.

Predictive maintenanceIntelligent diagnostics information is calculated and displayed on the sensor’s transmitter and tells you if the sensor needs maintenance or replacement – no more downtimes due to sen-sor failure!

System integrationKey ISM parameters can be fully integrated in a process control system via PROFIBUS® PA or FOUNDATION Fieldbus™.

■ Sensors are immediately recognized when connected to the transmitter – eliminating difficult configuration procedures.

■ Operational availability of measurement point within seconds.

■ Wireless module available for transmission from sen-sor to transmitter – no need for costly cable installation.

■ Sensors can be pre-calibrated in the lab and stored for later use, saving time and increasing operational avail-ability.

METTLER TOLEDO’s ISM product range includes…

… a wide range of sensors for … advanced single- and multi-channel transmitters … software applications ■ pH ■ 4-wire ■ iSense Asset Suite ■ dissolved and gaseous O2 ■ 2-wire ■ pH data logger ■ conductivity ■ wireless module ■ turbidity


Intelligent Sensor Management Reduces Life Cycle Costs and Improves Process Safety

Diagnostics Maximum Performance

■ Any sensor maintenance requirement is recognized at an early stage, reducing downtimes and minimizing plant operation costs.

■ Dynamic Lifetime Indicator estimates in real time the remaining lifetime of the sensor.

■ CIP / SIP cycles counted automatically.

■ Sensor spider diagram for fast troubleshooting.

■ iSense Asset Suite software offers you a unique means of optimizing the performance of ISM sensors for en-hanced reliability and process safety.

■ Key Performance Table enables you to evaluate the condition of an ISM sensor at a glance, without the need of a transmitter.

■ Documentation of every calibration as well as the entire sensor history – documentation requirements to regu-latory standards are easily met.

METTLER TOLEDO’s ISM product range includes…

… a wide range of sensors for … advanced single- and multi-channel transmitters … software applications ■ pH ■ 4-wire ■ iSense Asset Suite ■ dissolved and gaseous O2 ■ 2-wire ■ pH data logger ■ conductivity ■ wireless module ■ turbidity

Intelligence starts in the head

www.mt.com / ISM

Visit for more informationwww.mt.com/pro

Trouble-free Conductivity Measurementa Completely New SolutionReduce your operating costs right from measurement point in-stallation down to configuration and maintenance. This is all possible with the advanced M400 transmitter line from METTLER TOLEDO. It offers conductivity measurement based on ISM sen-sors as a new feature thus providing the benefits of ISM technology for petrochemical applications. Conductivity sen-sors with Intelligent Sensor Management (ISM) technology carry their own calibration data for easy commissioning. They can monitor themselves and provide real-time information for up-to-date sensor diagnostics. With ISM, installation costs are significantly reduced.

www.mt.com/ISM

Get in-line with METTLER TOLEDO

Mettler-Toledo Ingold, Inc. 36 Middlesex TurnpikeBedford, MA 01730, USATel +1 781 301 8800Fax +1 781 271 0681Toll Free: 1 800 352 8763Email: [email protected]

battling corrosion in refineries with in-line process ... · pdf filebattling corrosion in...

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