Petrol Blending Paper

7/22/2019 Petrol Blending Paper

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Petrol Blending


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Petrol Blending- Greenergybackground paper 2

Greenergysells around 7 million litres of petrol per day to

supermarkets and other petrol retailers. All of this petrol is

manufactured in-house from a range of different petrol blend

components.

By blending its own petrol, Greenergyis able to maintain both cost

and quality control over its supply chain. Cost savings can bepassed on to the customer through lower pricing. Quality control

procedures enable the production of special grades such as Tesco

99 Octane petrol. They also ensure that every day grades of fuel

such as premium 95 octane petrol are produced efficiently with no

quality wastage. The efficiency of this process and the absence of

any waste (known to blenders as giveaway) bring whole of life

environmental benefits.

Through the process of blending Greenergyhas also managed to

stay at the forefront of biofuel developments in the UK.

Introduction


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1 Principles of petrol blending

The principle of petrol blending is to take a variety of raw materials, called components, of differing quality and price

and combine them to make a target petrol quality, called the specification.

The aim of blending is to ensure that the total cost of the components, the tankage, the laboratory work and other

infrastructure costs is less than the cost of buying pre made petrol on the open market. Blending is a significant

source of profit for Greenergy.

Blending has a specific language and terminology. There is a glossary of commonly used terms at the end of this

background paper.

Figure 1:The princples of blending

$ (sum of components) + $ (infrastructure) < $ (finished product)

20% low cost component

25% lower cost component

55% expensive and superquality component

100% finished product atmarket price and quality

Calculate

Mix

Test


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2 Key qualities of petrol

A measure of the ability of a petrol to resist detonation

(knocking or pinking). There are two measures of octane:

RONResearch Octane Number, a historic test method. In a

real world engine, RON is measurement of the anti knock

performance of petrol under part throttle.

MONMotor Octane Number, a modern, more severe test. In

a real world engine, MON is a measurement of the anti knock

performance of petrol under full throttle.

Reid Vapour Pressure, expressed in kPa. In the real world,

RVP determines whether the fuel is too volatile or not volatile

enough to start. The limits for RVP are different for winter and

summer specifications.

Expressed in volume % evaporated at specified degrees C.

In practice a smooth curve is required for easy burning.

Expressed in weight %. The sulphur content of a petrol

affects ifs emissions, the catalytic converter and the efficiency

of a car.

All expressed in volume %. All affect cleanliness and harmful

emissions.

Expressed in weight %. Oxygen has a positive effect on

emissions and also affects car tuning settings and economy.

Octane:

-

-

RVP:

Distillation:

Sulphur:

Benzene,olefinsand aromatics:

Oxygen:

We blend petrol to meet many quality specifications. Some of the most importantthe key measures of quality are:

Petrol quality in the UK changes four times per year in line with the weather. Summer petrol needs to be low volatility

so that it does not gas up the engine in hot weather. Winter petrol needs to be high volatility so that the fuel can be

gassy enough to start up on the coldest winter day. Spring and autumn specifications are mid way between the

winter and summer specifications.


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Table 1:Specification for winter petrol

Table 2:Specification for summer petrol


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3 Petrol blending components sources

Petrol blending components can be sourced from oil refineries, chemical plants, gas plants and increasingly the

agricultural supply chain.

Petrol is not naturally found in crude oil. Instead a low octane component called naphtha is found, but naphtha is

only around 60 octane and therefore unsuitable for running in a car engine.

The majority of naphtha distilled from oil refineries is catalytically upgraded to a high octane petrol component called

reformate.

Approximately 40% of crude oil is an unwanted heavy fuel oil that cannot be sold in its existing form. This fuel oil is

therefore chemically cracked into a gasoline component called cat cracked spirit and when this is combined with

reformate and other components, petrol is made.

Due to changing product specifications, individual production unit capacities, market demands for fuel oil etc, most

oil refineries are not in technical or commercial component balance and have to buy or sell components to deal with

surpluses or cover deficits. Greenergytrades in these component markets.

Butane

Naphtha

Isomerate

Reformate

Alkylate, MTBE orpolymerate

Cat CrackedSpirit (CCS)

Crude oilDistillation

Isomerisation

Reforming

Alky, MTBE orPolymerate

Fuel oil cracking(FCC or HC)

ButaneButaneButane

Fuel oil

L Naphtha

H Naphtha

Chemical Butane

Figure 2:Refinery component sources


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Butane

MTBE

(main source)

Synthetic alcohol

Pyrolysis gasoline(Pygas), MTBE,

Isopentane and otherpure chemicals

Bioethanol / ETBE

Crude oilproduction

MTBE

Alcohol

Plastic and

chemicals

Food andagriculture

Figure 3:Non refinery component sources

Natural Gas production


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4 Petrol blending component qualities

There are hundreds of petrol components traded in Europe, and dozens within each

category of components. For example, reformates alone can vary from 97 octane to

108 octane depending on which refinery they come from.

The following tables summarises the benefits and disbenefits of the main generic

types of components.

4.1. Reformate

Reformate is expensive, but has excellent octane and low RVP. The limiting blending

factor is its high level of aromatics.

4.2. Butane

Butane is attractive because it is clean and low cost. It is very volatile.


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4.3. Alkylate

Alkylate is clean and versatile but also expensive, which minimises its use. Where it

is used; it is added to meet aromatic limits. It is sometimes referred to as blenders

friend accountants foe.

4.4. Isomerate

Insomerate is clean and often low in price, but volatile and not often available.

4.5. Cat Cracked Spirit (CCS, LCCS)

CCS, is high in sulphur but low in cost. It can be a key to the profitability of the blend.


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4.6. MTBE

MTBE is an oxygenate and a useful blending component.

4.7. Bioethanol

Bioethanol is very often required by regulation. It is high cost but often taxsubsidised, which makes it an attractive component.


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5 Bioethanol blending

Bioethanol is becoming an important part of the overall petrol component pool. Governments

around the world are encouraging its use as it is part renewable and hence a good tool in the

quest to reduce carbon emissions.

All petrol produced by Greenergycontains up to 5% bioethanol. Most of the bioethanol we

use is made in Brazil from sugar cane as this form of bioethanol results in greater

greenhouse gas emission savings than bioethanol produced from other crops.

Bioethanol is a very interesting blend component as in general it has excellent blending

.properties; very high octane, sulphur free, zero aromatics etc. The only down side is that it ishigh RVP, and slightly more complex to calculate its blend characteristics.

On a free market, quality adjusted, basis the cost of bioethanol compared to petrol is higher

than a blender would normally be prepared to pay.

To encourage its use, and to compensate for its cost, governments around the world have de-

taxed bioethanol compared to petrol. In the UK for instance Greenergypays 20 pence per

litre less duty on bioethanol than for petrol. This is a direct subsidy the cover the extra cost of

making and using bioethanol.


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6 The practicalities of blending

Figure 4 summarises the blending process at a typical Greenergyblending location.

Petrol components are imported by ship into specialised blending tanks. Typical ship sizes are 8 to 20 million litres.

These blending tanks are able to mix the components together rapidly. The blends are tested in the laboratory for all

petrol qualities. If a blend is not perfect (either giveaway or off-grade) it is reblended and retested until quality targets

are met.

Once the quality of the blend meets the quality targets, it is pumped out from the blend tankage into specialised road

delivery tanks which are then connected to truck loading racks.

Trucks arrive 24 hours per day to collect the petrol and deliver it to customers in typical loads of 25,000 to 35,000

litres per load. All petrol made by Greenergyincludes performance additives. The additives, such as detergents that

help keep the engine clean, lubricity enhancers or combustion improvers, are injected directly into the petrol as it is

loaded onto a customers truck. In this way individual customers can have their own preferred additive formulations

added to the fuel they buy.

Depending on their size individual blends take between 24 and 48 hours to prepare and pump over to the delivery

tanks. A typical blend size for Greenergyis 15 million litres split over two tanks. This is a continuous process; whereas one blend is being pumped out to delivery tanks, another blend is being made up.

Any bioethanol brought into the terminal has to be denatured so that it is no longer potable. This denaturing involves

adding a bitter chemical called Bitrex and methanol. Only denatured bioethanol can be used in blends.


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Blended productroad delivery

tankage

Refinery,blend tankage

Bio-ethanoldenaturing

Truck

Racks

Ship Jetty

Figure 4:Blending terminal schematic

Finished producttransfers

Sales

Productimports

Butaneimports

Blendcomponentimports

Bioethanolimports

Blending


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Glossary of blending terminology

General blending terms:

Component(s): The petrol raw materials that make up the blend.

Bounds: The minimum or maximum amount of any component that can be added to blend. Limitations may be due

to market availability, size of tank and the amount of tanks etc. Bounds are an inputlimitation to the blending

process.

Constraints: Product specifications or other factors that the final product must meet. These are normally set by the

technical requirements of the product such as minimum octane or maximum volatility. Constraints are outputlimitations.

Target function: The driving force of the blending process comprises any numerical factor that the blender seeks to

maximise (e.g. profits), minimise (e.g. costs), or achieve (e.g. a target level of production or a minimum/maximum

specification point). There can only be one target function, which is normally maximum gross margin.

LP (Linear Program): A computer program that takes into account all the components, bounds and constraints to

create the optimum target function. Greenergyhas its own LP which it developed in-house to optimise its petrol

blending.

Solution: The combination ofcomponentsthat achieves thetarget functionwhilst meeting the boundsand

constraints. This is normally determined by using an LP.

Terms related to actual blending solutions:

Tight: When petrol is blended up to a specification limit that costs money to achieve, it is said to be tight. Typical

specification limits are octane, volatility and chemical composition. Because it costs more to make 96 octane petrol

than 95 for example, Greenergys target for standard grade petrol is for the octane to be tight at 95 octane.

Giveaway: When petrol is not blended up to a specification limit and when this costs money, it is said to be in

giveaway.

Slack: When petrol is not up to a specification limit but the limit does not cost any money, it is said to be slack. For

instance the maximum level of olefins permitted in petrol is 18%, but the components that Greenergybuys are

seldom above 12% on average so Greenergyis normally slack on olefins. This is a positive outcome as olefins are

reactive and can create pollution.

On-grade: When a petrol meets a specification it is on-grade.

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