Refinery Products Blending

Refinery Products Blending

Tri TRUONG HUU Tel: 0932 445 199 Mail: [email protected]

Vung Tau, 2015

About Instructor  Current job position: Lecturer - Researcher, Chemical Engineering - Oil and Gas University of Science and Technology - The university of Da Nang

 Studies:  2011-2012: Postdoctorant, LMSPC - University of Strasbourg - France;  2008-2011: Doctor of Philosophy in Chemical Engineening - University of Strasbourg - France;  2000-2001: Master of science in Petroleum Products and Motor, IFP - France;  1997: Engineer in Chemistry of Oil Refining and Petrochemistry, Hanoi University of Technology.

EMERGENCY EVACUATION INSTRUCTION Whenever you hear the building alarm or are informed of a general building emergency:  Leave the building immediately, in an orderly fashion;  Do not use elevators;  Follow quickest evacuation route from where you are;  If the designated assembly point/area is unsafe or blocked due to the emergency, proceed to the alternate assembly point;  Report to your Work Area Rep at the assembly point to be checked off as having evacuated safely;  Specific safety requirements for TODAY. Today: NO testing of fire alarm systems

COURSE OUTLINE

 Total duration: 1 day;  Lecture: 1 day;

OUTLINE 1. Energy and environmental issues; 2. Classification of fuels; 3. Product specifications (TCVN system); 4. Product blending system; 5. Fuel additives; 6. Petroleum Products blending; 7. Blending calculation and learner programming.

COURSE OBJECTIVES When you complete this module you will be able:  To grasp main characteristics of petroleum products and their significance in regard to needs of end-users;  To grasp main specifications of petroleum products (TCVN);  To grasp the general calculation in a refinery;  To grasp the blending calculation and the product blending system.

COURSE ASSESSMENT Lecture:  The multiple-choice (knowledge based questions) section of the test is scored based on the number of questions you answered correctly;  Multi-choice test :

questions

 Passing grade: 80%;  No additional points are subtracted for questions answered incorrectly;  Even if you are uncertain about the answer to a question, it is better to guess than not to respond at all.

INTRODUCTION

Introduction 

The world’s primary energy consumption (this value varies depend on source).

Source : BP 2014

Introduction 

Petroleum is one of the most important fuels derived fossil energy sources;



Petroleum-based fuels have been used to power automotive vehicles and industrial production for well over 100 years;



A large part of energy consumption is in form of engine fuels;



Fuels for internal combustion engines produced from primarily sources are composed of combustionable molecules;

Introduction 

Different gas, liquid, and solid products are usable as engine fuels.



These fuels are classified: 

Crude oil based: Gasoline, diesel fuels, and any other gas and liquid products;



Non-crude oil based: Natural gas based fuels (compressed natural gas (CNG))



Biofuels: methanol, ethanol, any other alcohols and different mixtures of them; biodiesel; biogas oil (mixtures of iso- and nparaffins from natural tryglicerides).

Introduction Environmental issues

Soot

C6H6

PM

Sulfur compounds + Oxyen → SOx → acids

Introduction European emission standards for light commercial vehicles ≤1305 kg, g/km

For Diesel

For Gasoline

Introduction European emission standards

Introduction 

The path toward zero emissions…

Introduction 

The progression toward zero emissions …

Introduction 

The path toward zero emissions…

Introduction 

EU gasoline specifications

Introduction 

EU gasoline specifications

Introduction 

European Gasoline specifications trends

Introduction

World context: High Low Low

RON,

sulfur content,

benzene content,

Limited

aromatics content,

Limited

olefins content,

No

lead

Introduction

World context: High octane gasoline requirement: RON = ... 90 → 92 → 95 → 98 →

???

Why we need High octane gasoline ?

Introduction  New

gasoline specifications require:



Maintaining a high octane number;



Meeting reduced sulfur content;



Meeting reduced Aromatics and Benzene specifications;



Meeting reduced Olefines specifications.

I n t r o d u c t i o n

Introduction

Typicaly gasoline pool


composition in USA

composition in EU

(before 2000)

(before 2000)

Introduction 

The mechanism of the development of vehicles and fuels

Introduction 

Over the years, fuel specifications have evolved considerably to meet the changing demands of engine manufacturers and consumers;



Both engines and fuels have been improved due to environmental and energy efficiency considerations;



New processes have been developed to convert maximum refinery streams into useful fuels of acceptable quality at reasonable refinery margins.

Classification of fuels

Classification of fuels 

The fuel industry categorizes the different types of fuels as follows: 

Gasoline: A volatile mixture of liquid hydrocarbons generally containing small amount of additives suitable for use as a fuel in a spark - ignition internal combustion engine;



Unleaded gasoline: Any gasoline to which no lead have been intentionally added and which contains not more than 0.013 gram lead per liter (0.05 g lead/US gal);



E85 (E5) fuel: A blend of ethanol and hydrocarbons in gasoline with 75–85% (<5%) of ethanol. E85 (E5) fuel ethanol must meet the most recent standard of a region or country;



Racing gasoline: A special automotive gasoline that is typically of lower volatility, has a narrower boiling range, a higher antiknock index, and is free of significant amounts of oxygenates. It is designed for use in racing vehicles, which have high compression engines;



Liquified Petroleum gases: (LPG) Gas phase hydrocarbons, mainly C3 and in low quantity C4. Their quality is determined by the country or regional standards.



Compressed natural gas (CNG): Predominantly methane compressed at high pressures suitable as fuel in internal combustion engine;



Aviation turbine fuel A refined middle distillate suitable for use as a fuel in an aviation gas turbine engine;



Diesel fuel A middle distillate from crude oil commonly used in internal combustion engines where ignition occurs by pressure and not by electric spark.



Low or ultra-low sulfur diesel (ULSD): Diesel fuel with less than 50 and 10 mg/kg respectively;



Biodiesel: A fuel based on mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats. Biodiesel containing diesel gas oil is a blend of mono-alkyl esters of long chain fatty acids and diesel gas oil from petroleum. A term B100 is used to describe neat biodiesel used for heating, which does not contain any mineral oil based diesel fuel.

Product Specifications Product

ASTM

Description

Specs

Standard Specification for Automotive Spark Ignition

Gasoline

D4814

Jet

D1655

Standard Specification for Aviation Turbine Fuels

Kerosene

D3699

Standard Specification for Kerosene

Diesel

D975

Standard Specification for Diesel Fuel Oils

Fuel Oil

D396

Standard Specification for Fuel Oils

Engine Fuel

NSRP’s Specification of LPG

NSRP’s Specification of Gasoline

NSRP’s Specification of Gasoline

NSRP’s Specification of Kerosene

NSRP’s Specification of Diesel fuel

NSRP’s Specification of Diesel fuel

NSRP’s Specification of Jet A1



Aviation Gasoline:BS EN 589:2004

NSRP’s Specification of Fuel Oil

NSRP’s Specification of Paraxylene

NSRP’s Specification of Benzene

Product blending system

Purpose of blending 

The process units produce various product components and base stocks, which must be combined or blended, sometimes with suitable additives, to manufacture finished products;



These finished products are generally grouped into the broad categories: 

LPG;



Gasoline;



Kerosene, Jet fuel;



Diesel;



Fuel oil, and so forth.


Increased operating flexibility and profits result when refinery operations produce basic intermediate streams that can be blended to produce a variety of on specification finished products;



The objective of product blending is to allocate the available blending components in such a way as to meet product demands and specifications at the least cost and to produce incremental products which maximize overall profit.




Blending methods normally employed include: 

Batch blending;



Partial in-line blending;



Continuous in line blending.

Petroleum products are shipped in bulk using: 

Pipelines;



Marine tankers;



Occasionally road or rail facilities.

Batch blending 

In batch blending, the componemts of a product are added together in a tank, one by one or in partial combination;



The materials are mixed until a homologenous product is obtained.

Batch blending

Additives are added and mixed thoroughtly After laboratory analysis

Batch blending Jet Mixer

Batch blending 

Batch blending is most adaptable to use in small refineries, in which a limited variety of blends are to be produced.



In a refinery, the cost of extra blending tanks, pumps, and related equipment may not be as large as the cost of instrumentation and equipment needed for in-line blending; and for this reason, many large refineries continue to use the batch blending system because of its ease and flexibility of its operation.

Partial in-line blending 

Partial in-line blending is accomplished by adding together product components simultaneously in a pipeline at approximately the desired ratio without necessarily obtaining a finished specification product;



Final adjustments and additions are required, based on laboratory tests, to obtain the specification product;



In this case, the mixing is required only for final adjustment;



Additives are added as a batch into the blending header during the final stages of the blend or final adjustment stage.


The required components are pumped simultaneously from each base stock tank through the appropriate flow controller into a blending header, so an individual pump is required for each component.



The capacity of the pump must be established to permit simultaneous pumping and delivery of one day's blend to product tanks within a reasonable time (about 6 hours);



The quantity of each component of a blend must be proportioned by the use of a flow meter and control valve.

Partial in-line blending


Flow controllers are set to a predetermined rate and flow is recorded;



Flow meters used for partial in-line blending need not be extremely accurate (accuracy ranges of 5%)



Mixers are required in final storage tanks for correction of blends by addition of components.


Partial in-line blending is suitable for moderate-sized refineries, where the cost of blend tanks would be excessive and blending time must be minimized.



Blending time is substantially reduced because of the following: 

Simultaneous pumping of components instead of consecutive pumping, as is the case in batch blending;



Reduction of overall mixing time;



Elimination of multiple gauging operations.

Continuous in-line blending 

In this way, all components of a product and all additives are blended in a pipeline simultaneously, with such accuracy that, at any given moment, the finished specification product may be obtained directly from the line;



The accuracy and safeguards included in the system, so no provision is necessary for reblending or correction of blends;



Various methods of controlling individual flow rates with interlock provisions have been used to ensure delivery of only the specified material.

Continuous in-line blending


An individual pump is required for each component, the quantity of each component of a blend must be accurately delivered;



The recording flow meters and flow control valves used to proportion components are similar to those used for partial in-line blending, but a greater degree of accuracy is necessary (An accuracy of 0.25% or better is expected);



To ensure continued accuracy of the blends under varying operating conditions, the blending equipment is designed to provide for adjustment of individual component flow in proportion to total flow.


Two types of blending controls are used to adjust component flows to desired rates: a mechanical system or an electronic system;



To ensure the accuracy of the blend, it is necessary to calibrate meters frequently. One method of meter calibration is to remove the meter from the system and replace it with a calibrated space meter;



Continuous in-line blending is best for large refineries that make several grades of products.


Advantages: 1. Reduced blending time. 2. Minimum finished product storage, since components are stored and blended as required. 3. Increased blending accuracy with minimum "give away" on quality. 4. Reduction in loss through weathering of the finished product. 5. Minimum operating personne.


Disadvantages: 1. When products are transferred directly to a pipeline or bulk transport, a complete blender is required for each product, which must be loaded simultaneously. For example, if a tanker is to be loaded with two grades of gasoline simultaneously, two blenders are necessary; otherwise, the advantage of reduced product tankage cannot be realized. 2. There is extreme difficulty in correcting errors, if they occur (the only possible errors are human errors). 3. High initial investment and high maintenance cost of instruments.

Fuel additives

Fuel additives 

Additive is a chemical compound (substance) which is used in small dosages in order to add or improve properties of virgin fuels.





Conventionally, chemical compounds added in: 

High concentrations (>1%) → called blending components;



Lower concentrations ( <1%) → called additives.

In modern automotive fuels, a combination of several chemical additives is used in order for the fuel to meet the desired performance level;



Sometimes ‘allways’ the additive is even used to realize better margins by diverting a value- added product to other applications.

Fuel additives 

There are six reasons for using additives in fuels: 

To improve handling properties and stability of the fuel;



To improve combustion properties of the fuel;



To reduce emissions from fuel combustion;



To provide engine protection and cleanliness;



To establish or enhance the brand image of the fuel;



To increase in the economic use of the fuel.

Fuel additives 

Motor engine gasoline additives and their functions:

Fuel additives 

Motor engine gasoline additives and their functions:

Fuel additives 

Additives for Gasoline Distribution Systems 

Antioxidants



Metal deactivators



Antistatic agents



Corrosion inhibitors



Sediment reduction agents



Dyes



Dehazers

Fuel additives 

Additives for gasoline vehicle system 

Antiknock additive (was tetra ethyl lead, which is now phased out)



Anti-valve seat recession additive (also phased out due to metallurgy change in the engines)



Carburetor detergents (gradually being phased out due to the introduction of injectors)



Deposit control additives



Deposit modifiers



Friction modifiers



Lubricity improvers

Fuel additives 

Additives of diesel fuels and their functions :

Fuel additives 

Additives of diesel fuels and their functions :

Fuel additives 

Additives for Diesel Distribution System 

Antifoam agents



Antistatic agents



Biocides



Corrosion inhibitors



Sediment reduction agents



Dyes



Demulsifiers



Flow improvers/wax crystal modifiers/wax dispersants Metal deactivators



Markers to check origin



Stabilizers

Fuel additives 

Additives for Diesel Vehicle System 

Cetane improvers



Combustion improvers



Deposit control additives



Injector detergents



Lubricity improvers



Friction modifiers

Fuel additives 

Additives for gasoline and diesel distribution systems are used in refineries to meet minimum fuel specifications at the optimum cost without compromising on the yield of the products;



Fuel quality standards have undergone a ratcheting-up gradation with progressive improvements in engine design and more stringent environmental regulations;



These changes in fuel quality have involved: 

Reductions in: S, Ar, benzene, PHA, olefins, and lead;



Improvements in ON, CN, oxidation stability, and storage stability.

Gasoline blending

Gasoline blengding 

The purpose of blending is not only to ensure the specification techniques but also the specification environments;



During the blending of gasolines not only the physical and chemical properties of each blending component has to be considered but also those contributions that may be harmful material emissions; 

Quality of combustion (structure each substance)?



Volatile organic compounds (RVP, Distillation cure)?



The formation of toxic compounds the exhaust gas (Ar, Olefin, S...)?

Gasoline blengding


The blending stocks for gasoline: • • • • •

Cat.Naphtha (FCC naphta); Reformate (CR); Alkylate; Isomerate; Full range Naphtha;

• Naphta obtained from others process: hydrocracking, Visbreaking, Delayed coke ... • Butane; • Oxygenate gasoline: MTBE, ETBE, ethnol... • « Additives »

Typicaly gasoline pool composition in USA

Gasoline blengding



composition in USA

composition in EU

(before 2000)

(before 2000)


The main source of the benzene content (ca. 80%) is the reformate, but the benzene content of the C5-C6 fraction of the coker process, as well as of LCN, LSR, and

hydrocracking

gasolines, is also significant; 

The quantity of reformate and LCN determines definitely the other aromatic content (ca. 65%);



The olefin content depends definitely on the used quantity of LCN (ca. 90%).


The olefin content depends definitely on the used quantity of LCN (ca. 90%);



In many refineries, the polymer naphthas and naphthas from variants of thermal cracking processes have different effects on the olefin content.



The sulfur content is determined by the fraction of HCN.


The main sources of the volatile organic compounds (VOC) in gasolines are n-butane (ca.25%), ethanol (ca.12%), alkylate (ca. 8%), reformate (ca.15%), HCN (ca.5%), LCN (ca. 23%), and coking C5-C6 fraction (ca.1%).



The reformate and cat.naphthas favor the formation of nitrogen oxides (reformate ca.21%; HCN: ca.40%; LCN: ca.30%; n-butane: ca.5%; isomerate: ca. 4%; coking C5-C6 fraction: ca. 2%).


The formation of toxic materials and their emission quantities depend on mainly the proportions used of reformate and the cat.naphthas (reformate ca. 60%; HCN ca.14%; LCN ca.16%; nbutane: ca.5%; isomerate: ca. 2%; coking C5-C6 fraction: ca.1%; alkylate: ca. 2%).

Knocking phenomenon 

Knocking (also called knock, detonation) in spark-ignition internal combustion engines occurs when combustion of the fuel/air mixture in the cylinder starts off correctly in response to ignition by the spark plug, but one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front;



“When unburned fuel/air mixture beyond the boundary of the flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur”.

Knocking phenomenon 

Detonation is characterized by an instantaneous, explosive ignition of at least one pocket of fuel/air mixture outside of the flame front;



A local shockwave is created around each pocket and the cylinder pressure may rise sharply beyond its design limits.

Normal combustion

Engine knock

Engine knock 

Engine knock is a soud that is made when the fuel igintes too early inthe compression stoke;



Severe knock causes severe engine damage, such as: •

Decreased thermal efficiency of engine;

•

Increased the toxic compounds in the exhaust gas;

•

Possibility of mechanical damage to the engine.

Octane number (ON) 

Octane number is defined as the percentage of iso-octane in a blend of iso-octane (2,2,4-trimethylpentane) and n-heptane, which will give the same engine performance as could be achieved by the actual fuel sample.



An engine runs with 100% pure iso-octane, the power rating is 100% (knock free) and is defined as 100 octane number;



An engine is run with 100% n-heptane, a straight chain hydrocarbon, there will be tremendous knocking in the engine and the octane number is taken as zero;

Octane number (ON)


The ON of the gasoline sample, therefore, falls within 0 – 100;



The ON of a hydrocarbon is a function of its chemical composition: Isoparaffins and aromatics have high octane numbers while n-paraffins and olefins have low octane numbers; Aromatic > olefin branched > iso-parafin > naphten branched > olefin ‘normal’ > naphten > n-parafin.


Octane number is a parameter defined to characterize antiknock characteristic of a fuel (gasoline) for spark ignition internal combustion engines;



Octane number is a measure of fuel's ability to resist autoignition during compression and prior to ignition;



Higher octane number fuels have better engine performance.


Octane values is measured in a standard engine, developed by Cooperative Fuel Research (CFR) engine.

RON

MON


RON correlates with low speed, mild driving conditions;



MON relates to high speed, high severity conditions;



Most gasolines have higher RON than MON, this difference is called fuel sensitivity: S = RON – MON;



For fuels of same RON, high S gasoline has lower MON;



Antiknock Index = (RON + MON)/2.



RdON



RONR100 (ΔRON)


Gasoline Blend Stock Properties


Blending octane and RVP of ethers and alcohols

Volatility of engine gasolines 

The volatility characteristic of engine gasolines has a fundamental influence on the performance of (4 stock) sparkignition engines.



Volatility is characterized generally by the gasoline’s Reid vapor pressure and distillation curve. The vapor-liquid ratio is often considered as well.

Vapor Pressure 

Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system;



The equilibrium vapor pressure is an

indication

of

a

liquid's

evaporation rate. It relates to the tendency of particles to escape from the liquid (or a solid); 

A substance with a high vapor pressure at normal temperatures is often referred to as voliatile.

Reid Vapor Pressure 

In reality, vapor pressure is usually measured in a bomb Reid, result obtained called vapor pressure Reid (RVP);



RVP is defined as the absolute vapour pressure exerted by a liquid at 100 °F (37.8 °C) as determined by the test method ASTM-D323;

4V V

Reid Vapor Pressure 

RVP should be concerned: • Warm-up vehicle; • Vapor lock; • Evaporation losses.



The RVPs for gasoline are generally between ‘350 and 1000 mbar’, depend on seasons and country.

Distillation curve 

Gasoline is a mixture of more than 400 volatile and flammable liquid HC ranging from 4 to 12 carbon atoms/molecule, the boiling range falls in the range 30 - 215°C;



In the laboratory, Gasoline is distilled at atmospheric pressure according to the standard ASTM method of distillation (ASTM D86);



A sample of 100 mL is placed in a standard distilling flask and the vapour is condensed through a condenser, liquid is collected in a graduated cylinder.


Initinal Boiling Point (IBP): The temperature at which the first drop of distillate appears after commencement of distillation in the standard ASTM laboratory apparatus;



Final Boiling Point (FBP): The maximum temperature observed on the distillation thermometer when a standard ASTM distillation is carried out;



After the IBP, distillation is continued and the temperature of the vapour

and

the

cumulative

volume

percent

collected

are

simultaneously reported (5 percent: T5, 10 percent: T10, 15 percent: T15, 20 percent : T20 and etc...); 

A distillation curve plots temperature versus the amount of distillate collected or inverse.

Distillation curve Typical results for an ASTM D86 distillation of a gasoline

FBP

IBP

Losses

Residue

Distillation curve

Distillation curve

Distillation curve

Gasoline volatility should be arranged according to weather conditions particularly ambient Temperature


IBP, T10 should be concerned: • Start up at cold temperatures; • Vapor lock; • Evaporation losses.



T50 should be concerned the acceleration.



T90, FBP should be concerned: • Oil dilution; • Power; • Spark plug fouling; • Pollution.

Jet Fuel blending

Jet Fuel blending 

The key product properties of Jet fuel are: 

Freezing point



Smoke point



Sulfur content



Flash point

Plant layout of a refinery

Jet Fuel blending Smoke point 

The smoke point is determined as the height of the flame (in millimetres) produced by this oil in the wick of a stove or a lamp without forming any smoke;



The smoke point for an oil varies widely depending on origin and refinement;



The greater the smoke point, the better the burning quality;



Smoke point is related to the hydrocarbon type composition of such fuels, a high smoke point indicates a fuel of low smoke producing tendency.


Smoke point 1. Tetrahydronaphtalen C10H12 2. Mezitilen (C6H3(CH3)3) 3. Aromatics extracted from kerosene fraction 4. Kerosen fraction “without” aromatics 5. Cetene, C16H32 6. Cetane, C16H34

1→2→ 3→4 →5→6

Jet Fuel blending Smoke point 

Higher amount of aromatics in a fuel causes a smoky characteristic for the flame and energy loss due to thermal radiation;



Pure isooctane has a reference smoke point of 42.8 mm, whereas 60 vol % isooctane and 40 vol % toluene have a reference smoke point of 14.7 mm;

Jet Fuel blending Sulfur content 

Sulfur content is of great importance when the oil to be burned produces sulfur oxides that contaminate the suraoundings;



Hydrogen sulfide and mercaptans cause objectionable odors, and both are corrosive;



Their presence can be detected by the Doctor test (ASTM D-484, ASTM D-4952, IP 30);



The total sulfur content of burning oil should be low, less than 0.25% by weight (ASTM D-1266, IP 107).

Jet Fuel blending Flash point 

The flash point is the lowest temperature at which a liquid gives off enough vapor to ignite when an ignition source is present;



The flash point of a petroleum product is the lowest temperature at which it can vaporize to form an ignitable mixture in air; at the flash point, the vapor may cease to burn when the source of ignition is removed;



For safety considerations, the flash point of kerosene is in excess of 38°C, to prevent the inclusion of highly inflammable volatile fractions in kerosene distillates.


During flight, the temperature of the fuel in the aircraft tank decreases lead to form solid hydrocarbon crystals, which restrict the flow of fuel in the fuel system of the aircraft (clog filters);



Freezing point is the temperature at which the hydrocarbon crystals formed during cooling disappear when the fuel is reheated.



Test method ASTM D2386: Freezing point of Jet A1 should be around -50oC

Diesel blending

Diesel blending 

Diesel blending is simpler than gasoline blending because the limitations are fewer.



The key product properties are: 

Cetane number;



Sulfur content (in some countries);



Specific gravity;



Aromatics (PHA?).

Diesel blending : Sulfur content 

Total sulfur content varies considerably in petroleum products. Control of sulfur content is particularly important for petroleum products that are to be burned in engine, heating applicances or lamps.



Sulphur in diesel fuel can cause combustion chamber deposits, exhaust system corrosion, and wear on pistons, rings and cylinders;



Sulfur is measured on the basis of both quantity and potential corrosivity;



The measurement of potential corrosivity can be determined by means of a copper strip procedure.


Sulfur content Experimental result : • [S]=0,06% wt → PM, soot : 2,1%*. • [S]=0,85%wt → PM, soot :5,8% *. • [S]=2,9% wt → PM, soot : 12,2% *. * deposited on piston and segment


Sulfur content

Diesel blending : Cetane number 

Cetane number (CN) is a measure of the ignition delay of a diesel fuel, the shorter of the ignition delay, the higher is its cetane number and inverse;



The cetane number of a diesel fuel is defined as the percentage of cetane, arbitrarily given a cetane number of 100 (short ignition delay), in a blend with alphamethyl-naphthaline given a cetane number of 0 (long ignition delay), which is equivalent in ignition quality to that of the test fuel. C11H10 C16H34

CN = 100

CN = 0


The importance of cetane number is very evident.



As low CN usually causes an ignition delay in the engine, this delay causes starting difficulties and engine knock; • Poor fuel economy; • Loss of power; • Sometimes engine damage • White smoke and odor at start-up on colder days.



As low CN, combustion is violent, noisier, and less efficient with a high level of exhaust emissions;



White exhaust smoke is made up of fuel vapors and aldehydes created by incomplete engine combustion.


As high CN tend to: • Reduce combustion noise; • Increase engine efficiency; • Increase power output; • Start easier, especially at low temperatures; • Reduce exhaust smoke; • Reduce exhaust odor.



To assure acceptable cold weather performance, CN required: 45 – 55



CN of diesel fuels can be improved by adding additives such as 2-ethyl-hexyl nitrate or other types of alkyl nitrates.


The calculated cetane index is a useful tool for estimating the ASTM cetane number where a test engine is not available for its determination or where the quantity of the sample is too small for use in a test engine;



There are two test method for approximate cetane number were also developed.



ASTM D 976 CI = 454.74 – 1641.416ρ + 777.74ρ2 – 0.554(T50) + 97.083(log T50)2

• ρ : Density at 15oC, g/mL; • T50: Mid-boiling temperature, oC.

Diesel blending : Cetane number CI = 454.74 – 1641.416ρ + 777.74ρ2 – 0.554(T50) + 97.083(log T50)2


ASTM D 976 CI = 45.2 + 0.0892T10N + (0.131 + 0.901B)T50N + (0.523 – 0.420B)T90N + 0.00049(T210N – T290N) + 107B + 60B2



Where: • ρ : Density at 15oC, g/mL; • T10N= T10-215, oC; • T50N= T50-260, oC; • T90N= T90-310, oC; • B = e(-3.5DN)- 1; • DN = ρ – 0.85.



The calculated cetane index is particularly applicable to straight run fuels, catalytically cracked stocks, and their blends.


CI can also measure from different parameters of the fuel, is termed its diesel index (DI) or aniline point (PA) (ASTM D-611, IP 2) CI = PA – 15.5; with PA : aniline point °C or CI = 0.72 DI + 10; where

DI 

API.PA ( F ) 100

Diesel blending : Specific gravity 

SG is defined as the ratio of the weight of a given volume of oil to the weight of the same volume of water at a given temperature;



SG is of limited usefulness as a direct measure of diesel fuel quality;



SG is related to heat content and affects the volumetric fuel consumption of an engine; • Minimum SG: this limit is necessary to obtain sufficient maximum power for engine (flow controlled by regulating volume); • Maximum SG: this value is necessary to avoid smoke formation at full load.

Diesel blending 

CI versus density of component produced by different technologies.

Diesel blending 

The sulphur and aromatic content range of different gasoil streams.

Diesel blending



Management control

of

fuel blending

and motor

Diesel blending



Blend Optimization and

Supervisory

System (BOSS)

Diesel blending 

The main components of the blending technology package are the following: 

Interface for monthly linear programmed refinery models for middle period recipes



Timing system for optimalizing future products and blending orders



Online multivariate control and optimalization system for feedback from control equipment to enable inline certification and transport of products.

Diesel blending 

The controlled blending of fuels assures consistent profits for the refineries, and the application of suitably admixtured products having favorable hydrocarbon compositions means numerous advantages for the users as well: 

Smooth performance of vehicles;



More efficient fuel use;



Lower

maintenance

maintenance cost.

needs,

longer

engine

life,

lower

Diesel blending 

Smooth performance of vehicles 

Easy cold start



Smooth idle



Good combustion



Optimal track behavior (no vibration, engine stop, etc.)



Excellent acceleration



Low noise pollution.

Diesel blending 

More efficient fuel use: 

Reduction of fuel consumption



Reduction of exhaust gas



Emission exhaust gas with more preferable composition.

BLENDING CALCULATION

Blending calculation 

The main purpose of product blending is to find the best way of mixing different intermediate products available from the refinery and some additives in order to adjust the product specifications;



Product qualities are predicted through correlations that depend on the quantities and the properties of the blended components;



The final quality of the finished products is always checked by laboratory tests before market distribution. 

Gasolines are tested for ON, RVP and Distillation curve;



Jet fuel is tested for Freezing point and smoke point;



Gas oils are tested for DI, pour point and viscosity.


The desired property blend of the blended product may be determined using the following mixing blend rule:



Pi is the value of the property of component i



qi is : •

Mass;

•

Volume;

•

Molar flow rate.


Additive properties:    



Specific gravity; Boiling point; Sulphur content; Etc...

Properties are not additives:       

RON Viscosity; Flash temperature; Pour point; Aniline point; RVP; Cloud point.


Reid Vapor Pressure is not an additive property. Therefore, RVP blending indices are used.

xvi is the volume fraction of component i.


Flash Point is not an additive property. Therefore, flash point blending indices are used.

where :  xvi is the volume fraction of component i;  BIFPi is the flash point index of component i.  FPi is the flash point temperature of component i, in K; The best value of x is 0.06.


Another relation to estimate the flash point blending index is based on the flash point experimental data.

where :  FPi is the flash point temperature of component i, in oF;  The flash point blending index is blended based on wt% of components.


The pour point is the lowest temperature at which oil can be stored and still capable of flowing or pouring, when it is cooled without stirring under standard cooling conditions.



Pour point is not an additive property. Therefore, flash point blending indices are used.

where :  xvi is the volume fraction of component i;  PPi is the pour point of component i, in oR.


Cloud point is the lowest temperature at which oil becomes cloudy and the first particles of wax crystals are observed as the oil is cooled gradually under standard conditions.



Cloud point is not an additive property. Therefore, flash point blending indices are used.

where :  xvi is the volume fraction of component i;  BICPi is the cloud point blending index of component i;  CPi is the cloud point temperature of component i, in K; The value of x is 0.05.


Cloud point is the lowest temperature at which oil becomes cloudy and the first particles of wax crystals are observed as the oil is cooled gradually under standard conditions.



Cloud point is not an additive property. Therefore, flash point blending indices are used.

where :  xvi is the volume fraction of component i;  BICPi is the cloud point blending index of component i;  CPi is the cloud point temperature of component i, in K; The value of x is 0.05.


Aniline point is not an additive property. Therefore, aniline point blending indices are used.

where :  xvi is the volume fraction of component i;  BIAPi is the aniline point index of component i;  APi is the aniline point of component i, in oC.


Specific gravity is an additive property and can be blended linearly on a volume basis.



The specific gravity of a blend is estimated using the mixing rule:

where :  xvi is the volume fraction of component i.


The smoke point is the maximum flame height in millimetre at which the oil burns without smoking when tested at standard specified conditions.

where :  SPBlend is the blend smoke point in mm;  APBlend is the aniline point;  SGBlend is the specific gravity of the blend. 

API is not an additive property, and it does not blend linearly. Therefore, API is converted to specific gravity, which can be blended linearly.


Viscosity is not an additive property; therefore, viscosity blending indices are used to determine the viscosity of the blended products.



A number of correlations and tables are available for evaluating the viscosity indices.

where :  xvi is the volume fraction of component i;  BIvisi is the viscosity index of component i.


Octane number: If the octane number of a blend is calculated by the linear addition of an octane number for each component, the following equation can be obtained.



Where: xvi is the volume fraction of component i, and ONi is the octane number of component i.



Many alternative methods have been proposed for estimating the octane number of gasoline blends since the simple mixing rule needs minor corrections.


Octane number: The following octane index correlations depend on the octane number range as follows.


Octane number: The octane number index for a blend can be determined using the following equation:



Where: xvi is the volume fraction of component i, and BIONi is the octane number index of component i that can be determined from above equations.

Products blending at BSR 

Characteristics of components used to blend


Blending schematic


Blending schematic

Products blending 

Blending schematic

Products blending at BSR


Results of products blending






Blending schematic


Blending schematic






Blending schematic

Linear Programming

What is “Linear Programming” 

Terminology 

Objective Function – function z to be maximized;



Feasible Vector – set of values x1, x2,…,xN

that satisfies all

constraints; 

Optimal Feasible Vector – feasible vector that maximizes

the

objective function. 

Solutions 

Will tend to be in the “corners” of where the constraints meet



May not have a solution because of incompatible constraints or area unbounded towards the optimum.


LP is the most widely applied method for optimising many diverse applications, including refineries and chemical plants;



The application of LP has been successfully applied for selecting the best set of variables when a large number of interrelated choices exist;



A typical example is in a large oil refinery in which the stream flow rates are very large, and a small improvement per unit of product is multiplied by a very large number.


This is done to obtain a significant increase in profit for the refinery;



Optimisation means the action of finding the best solution within the given constraints and flexibilities;



LP is a mathematical technique for finding the maximum value of some equation subject to stated linear constraints;



Refinery optimisation using an LP model has been proven to bring economic gains higher than unit-specific simulation models or advance process control techniques;



Once all the data is configured, the model is updated with the variable data.


The required variable data includes the following: Crude oil or any other raw material prices with minimum and maximum availability:



Selling prices with minimum and maximum demands for the refinery products;



Available process unit capacities;



Available inventory stocks with minimum and maximum storage limits;



Quality specifications, etc, …


Word “programming” used here in the sense of “planning”



For N independent variables (that can be zero or positive) maximize



Subject to M additional constraints (all bn positive)

Thank you for your attention

Refinery Products Blending

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