reducing carbon emissions with antifoulants

7/29/2019 Reducing Carbon Emissions With Antifoulants

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Reducing carbon emissions withantifoulants

The UN Kyoto Protocol set the

rst binding targets for reduc-ing greenhouse gas emissions

in 1997. Although the US and Chinadeclined to participate, 37 industr-ialised countries and the European

Union now regulate carbon emis-sions, and the trend seems clear.The EU Energy Pact targets a 20%reduction in CO

2emissions by 2020,

and a carbon pricing scheme takeseffect in Australia in 2013.

These are challenging times forreneries. Sulphur levels must bereduced in nished fuels to meetincreasingly strict specicationsdriven by new emission controltechnologies in motor vehicles.

Meanwhile, crude feedstocks arebecoming heavier, higher in sulphurand more difcult (and energyintensive) to process.

Reneries are signicant sourcesof carbon emissions, much of it inthe form of CO

2from burning fuels

to distill, crack and hydrotreat theirfeedstocks. In spite of the caps andfees imposed on carbon, demandfor renery products continues togrow, increasing renery energyuse and emissions. Heavier, sourercrude feedstock adds to theproblem.

The costs are substantial: energycosts for a typical renery are 50-60% of total operating costs,excluding feedstocks.1 Efciency,always a high priority in reneryoperations, has never been moreimportant or more difcult toattain.

Since crude cost is the single mostimportant determinant of a ren-

erys protability,2 price differentialson challenging crudes have consid-erable appeal, even though unit

Carbon emission regulations make renery operation more costly, but appropriate

antifoulant treatment and monitoring can reduce these costs substantially

INDIA NAGI-HANSPAL, MAHESH SUBRAMANIYAM, PARAG SHAH and JAMES NOLAND

Dorf Ketal Chemicals

designs often limit feedstock exi-bility and heavy crudes can lead tofouling problems both of whichincrease carbon emissions that must

be factored into the renery operat-ing cost model.

Consider the current approximateprices of Murban crude (0.6 wt%asphaltenes) and Maya (10.0 wt%

asphaltenes). Since Maya is $ 13.61/bbl cheaper than Murban, a reneryprocessing 100 000 b/d can save upto $ 1 361 000/day in feedstockcosts alone. As the small sample ofcrudes in Figure 1 shows, Maya is

just one of many common high-asphaltene crudes.

Processing these heavy, high-

www.eptq.com PTQ Q1 2013 89

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90 PTQ Q1 2013 www.eptq.com

sulphur crudes consumes more

energy and increases greenhouse

gas emissions (see Figure 2).

Calculations of actual costs can be

quite complex, in part because

different fuels are often used at vari-

ous stages within the renery. Fueloil and fuel gas are common choices

in renery furnaces, and their energycontent and emissions differ.

Although it typically takes less ren-ery fuel oil to heat the feedstock to

the target temperature than would

be the case with renery fuel gas(renery fuel oil has a caloric valueof 8740 kcal/ m3 compared to 10 000

kcal/ m3 for fuel gas), fuel oil carbon

emissions are usually higher per

unit of fuel consumed.

Renery feedstock is anotherimportant consideration. Crude

production may generate enoughCO

2emissions to make a given feed-

stock more costly overall. Oil shale

production, for example, has been

shown to contribute more heavily to

carbon emissions than the extraction

of other hydrocarbons.

These issues are increasingly

important because of the way

carbon emissions regulations work.

The Western Climate Initiative in

selected Canadian provinces and

California is running a cap-and-trade scheme. In Europe, the EU

Energy Pact contains key targets for

the year 2020, in particular a 20%

reduction in CO2

emissions (from

1990 levels) that is designed to

ensure that at least 20% of total

energy consumption comes from

renewable sources.

Emission Trading SchemeTo meet the new targets, many

countries will adopt Kyoto mecha-

nisms such as the Emission TradingScheme (ETS), through which coun-

tries can buy carbon credits known

as emission reduction units. These

can be bought from clean develop-

ment mechanism projects or carbon

emission reductions from joint

implementation projects.

European Union cap-and-trade

regulations are the largest such ETS

to date. Companies there are

granted emissions allowances that

they can buy, sell or trade witheach other, but at the end of the

year each company must have

enough emissions allowances to

cover their total emissions.

The EU ETS regulates 46% of the

EUs CO2

emissions by capping the

amount of CO2

that can be emitted

from factories and plants. Once

Phase III (2013-2020) of the scheme

is under way, more restrictive

controls on emissions can be

expected, along with more efforts to

reduce carbon credit consumption.

Support for these schemes is not

unanimous. Canada withdrew from

the Kyoto Protocol in December

2011 to avoid heavy nes for failureto meet emissions targets. China,

one of the worlds largest emitters of

greenhouse gases, has not signed the

Kyoto Protocol, but even there plans

are already under way to launch a

few pilot cap-and-trade markets and

to establish a fully operationalcarbon market by 2015.

In spite of these regional differ-

ences, it is clear to renersworldwide that carbon costs are

becoming signicant variables in therenery cost equation, and many areactively seeking opportunities to

reduce emissions by increasing ef-ciency. Their rst targets are thesystems that consume fuel for

instance, furnaces and preheaters

where efciency depends onfeedstock, fuel source and combus-tion efciency.

Efciency gained from feedstockchanges must be weighed against

the prot potential from lower-priced crudes. Changing fuel types

can entail a signicant investmentand can have a substantial impact

on operations. Combustion improv-

ers are a lower-cost option that may

help in some cases.

Carbon capture and storage (CCS)

is another alternative. As the nameimplies, CCS limits the amount of

CO2

released into the atmosphere

by capturing CO2and storing it in

geological formations underground.

This, too, is capital intensive. CCS

is the way of the future despite its

economic implications.

AntifoulantsAntifoulants offer another way to

improve efciency, a proven

approach that entails little or nocapital investment. Antifoulants can

also improve gross margins by

enhancing renery feedstock exibil-ity, and costs are usually very low

in comparison to the alternatives.

Uncontrolled fouling decreases

heat transfer efciency and through-put, increasing fuel consumption

and carbon emissions. Feedstock

exibility is impaired and, if leftuntreated, fouling reduces through-

put and can force units ofine forcleaning or repair.

Fouling is of two general types:

inorganic and organic. The former is

usually caused by elevated levels of

metals in renery feedstocks, typi-cally occurs between 150 and 360C,

and tends to increase the potential

for costly and dangerous corrosion.

Crudes produced from deep oceanic

locations often exhibit inorganic

fouling due to contaminants such as

salts, lterable solids, basic sedi-ments and corrosion products.

Organic fouling generally occurs

above 250C in cracked streams,

often as a result of high asphaltene

content or incompatible blends of

asphaltenic and parafnic crudes.Whether the fouling is inorganic or

organic, success with antifoulants

depends on careful monitoring. Key

parameters include heat transfer

rates, heat exchanger duties,

approach enthalpies, feedstockcomposition, CO2

emissions and

fuel combustion efciency.Selection of antifoulant is also

important, especially with todays

increasingly sour feedstocks.

Sulphidation is common with these

crudes, leading to iron sulphide-

promoted fouling. In most cases,

antifoulants must therefore be effec-

tive on asphaltenes and iron

sulphide.

Antifoulants work by stabilising

asphaltenes that would otherwisebecome destabilised when heated.

This prevents deposition of polynu-

clear aromatics that, upon further

heating, can form coke. Left

unchecked, fouling reduces heat

transfer from the heating media to

the cold stream and increases the

furnace loading needed to achieve

the required coil outlet temperature.

Figures 3 and 4 illustrate antifou-

lant functionality by comparing

untreated feedstock with treatedsamples. Asphaltenes that agglom-

erate and settle out in minutes


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without antifoulant treatment

remained stabilised for an hour or

more in the test.

Experience indicates that antifou-

lants can increase furnace inlet

temperature by 5 to 15C in fouled

systems. It is possible to do even

better with periodic cleaning. Theway the antifoulant is applied has

considerable influence on the

92 PTQ Q1 2013 www.eptq.com

results, and choosing the correct

injection point is especially impor-

tant. A suction pump upstream of

the main fouling exchangers is

ideal.

Case study

The following case study illustratesthe potential benefits of antifoulantson fuel cost and CO

2emissions.

Refinery X was running at an aver-age throughput of >300 000 b/ d.

The average coil outlet temperature

(COT) when the feedstock wastreated with antifoulants met the

refinery standard required toproduce target yields of down-

stream finished products. Withoutantifoulant, the target COT was

often impossible to achieve, and

considerably more energy was

required (see Figure 5).Antifoulant treatment signifi-

cantly reduced the fuel consumption

required to maintain target COT,

lowering specific fuel costs bynearly 4% (see Figure 6). This savedthe refinery approximately 41 000per month on fuel alone.

At an average carbon credit value

of 16 per ton of CO2, refinery

carbon cost savings would total

59 000, raising the overall finan-cial impact of antifoulant treatment

to approximately 100 000 permonth (see Figure 7).

ConclusionCarbon emission regulations makerefinery operation more costly, butappropriate antifoulant treatment

and monitoring have been shown

to reduce these costs substantially.

Antifoulants also allow refiners toenhance gross refining margins byexploiting lower-cost feedstocks.

They reduce the fuel consumption

required to maintain coil outlettemperatures for target throughput

rates. As a whole, antifoulants

are an environmentally friendlychoice with attractive economic

benefits.

Without additive With additive

Figure 3 Asphaltene dispersion studies with and without antifoulant

Agglomeratedasphaltenes

Dispersedasphaltenes

11:41 am 3:50 pm

Figure 4 Testing under a microscope: agglomerated and dispersed asphaltenes

1.90

1.92

1.88

1.86

1.84

1.82

1.80

No antifoulant With antifoulant

Throughput,

/m3

1.78

Figure 5 Specific fuel cost with and without antifoulant


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References

1Based on a natural gas price of about $6/MM

Btu for a typical 100 KBPSD refinery that emits

1.2-1.5 MM t/yr of CO2.

2 Stockle M, Carter D, Jones L, OptimisingRefinery CO2

Emissions, Foster Wheeler

Technical Paper www.fwc.com/publications/

tech_papers/files/ERTC%20CO2%20paper%2

0Nov07.pdf

3 Brandt A R, Unnasch S, Energy intensity and

greenhouse gas emissions from California

thermal enhanced oil recovery, Energy & Fuels

2010: Keesom W, Unnasch S, Moretta J, Life cycle

assessment comparison of North American

and imported crudes. Technical report, Jacobs

Consultancy and Life Cycle Associates for

Alberta Energy Resources Institute, 2009.

India Nagi-Hanspal is Lead Refinery Engineer,

Technical Services with Dorf Ketal Chemicals,

Mumbai, India. She holds a MEng degree in

chemical engineering from Imperial College

London. Email: [email protected]

Mahesh Subramaniyam is Director of Research

& Development with Dorf Ketal Chemicals. He

7.96

7.98

7.94

7.92

7.90

7.88

7.86

No antifoulant With antifoulant

Specificfuelconsumption,

kg/m3

7.84

Figure 6 Specific fuel consumption with and without antifoulant

41,000 infuel savings

59,000 incarbon credits

Figure 7 Financial benefit of antifoulanttreatment

holds a PhD in chemistry from Indian Institute

of Technology, Mumbai.

Email: [email protected]

Parag Shahworks in Global Refinery Technical

Services with Dorf Ketal Chemicals in software

development for desalter adequacy testing and

monitoring fouling in preheat exchanger trains.He holds a BEng in chemical engineering from

Mumbai University.


James Noland is Senior Director of the Process

Chemicals Division of Dorf Ketal USA, LLC. He

holds a BEng in chemical engineering from

Mississippi State University, USA.

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reducing carbon emissions with antifoulants

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