I. Statement of the Design Project

In recent environmental legislations, lower sulfur specifications are required in both gasoline

and diesel fuels. In a refinery in the Delaware Valley, it was anticipated that the new diesel

specification will require an order of magnitude lower of sulfur than currently obtained, which

means that from 0.05 wt% sulfur the new requirement will be 0.005 wt% sulfur content in

diesel. In order to achieve these low sulfur level, a new catalytic hydrodesulfurization (HDS)

system is to be designed. This type of reactor has been in use in the industry for a long time but

never for such a severe service.

This unit will require just two feeds: a liquid feed blend from the refinery, and hydrogen. Since

the refinery does not have a reforming unit (common hydrogen source within a refinery) or a

hydrogen plant, the necessary hydrogen would have to be bought from a third party.

Processing Conditions

In designing the HDS unit, the percent hydrodesulfurization (%HDS) is determined by

Equation 1.

%HDS=[1−(wt %S )product

(wt %S )feed ]×100 % (1)

The following table shows the conditions of the proposed operation that will be based from

processing data available from an older HDS unit.

Table 1. Conditions of the HDS operation (Quale, 2000)BASE

OPERATIONPROPOSED

OPERATIONFeed Sulfur, wt % 1.9 1.9Target Product Sulfur, wt % 0.05 0.005

Reactor ConditionsFeed Rate, TBPD 35 35

Space Velocity (SV), hr-1 1 ?H2 Circulation, scf/bb 800 1,000 (min.)H2 Partial Pressure, psi 630 800 (min.)Start of Cycle Temperature (SOC), °F 632 ?Aging rate (AR), °F/mo 4.7 ?

Page 1 of 35

The circulation and pressure values for the proposed operation are given as minimums to

achieve the necessary product specifications. Increasing these values will improve the catalyst

life, but result in higher capital and operating costs.

For our particular feedstock, the R&D department has done substantial pilot plant work on this

new process and has determined correlations which will assist in designing the HDS reactor.

These correlations are presented in Equations 2 and 3 which were based on the processing data

from an older HDS unit and a reference catalyst. These equations will be used to calculate the

unknown reactor condition values of the proposed operation (Quale, 2000). The terms denoted

with “0” are the baseline data from Table 1 and the values for the constants (A-F) are given in

Table 2. The SOC temperature is given by

T soc=T0+ A ∙ ln( SVSV 0 )+B ∙ ln [ ( S feed

S product−1)

( S feed

Sproduct−1)0

]−C ∙ ln [ PH 2

(PH 2)0]−D ∙ ln [ H 2∘.

( H2 ∘. )0 ] (2)

where Tsoc and T0 are in °F and the aging rate is given by

AR=AR0×[ PH 2

(PH2 )0 ]E

×exp [F ∙( 1T 0

− 1T soc )] (3)

where Tsoc and T0 are in °R.

Table 2. Constants used for the correlations of the reaction conditions

Constant Value

A 45

B 44

C 20

D 30

E 1.7

F 18,000

Page 2 of 35

II. Diesel Fuel

Diesel fuels are distillates with a boiling range of about 149 to 371°C and comes in several

different grades, depending upon its intended use. Diesel fuel is not a single substance but a

blend of various petroleum-derived components, including paraffins, isoparaffins, napthenes,

olefins and aromatic hydrocarbons, each with their own physical and chemical properties.

Diesel fuel must satisfy a wide range of engine types, differing operating conditions and duty

cycles, as well as variations in fuel system technology, engine temperatures and fuel system

pressures. It must also be suitable for a variety of climates (Reynolds, 2007). The properties of

each grade of diesel fuel must be balanced to provide satisfactory performance over an

extremely wide range of circumstances. In some respects, the prevailing quality standards

represent certain compromises so that all the performance requirements may be satisfied. By

controlling specifications and properties, it is possible to satisfy the requirements of millions of

compression ignition engines with a single grade of diesel fuel.

Diesel fuel produces power in an engine when it is atomized and mixed with air in the

combustion chamber (UFA Co-operative Limited, 2009). Pressure caused by the piston rising

in the cylinder causes a rapid temperature increase.  When fuel is injected, the fuel/air mixture

ignites and the energy of the diesel fuel is released forcing the piston downwards and turning

the crankshaft. Diesel fuel in general are used in diesel engines and its fuel ignition takes place

without spark, as a result of compression of the inlet mixture and then injection of fuel.

DIESEL FUEL QUALITY AND PROPERTIES

A. Cetane Number

Cetane Number is a measure of the ignition quality/delay of a diesel fuel and affects

combustion roughness. It is often confused with the octane number of the fuel. Octane is

a measure of a spark ignition engine fuel’s (gasoline) ability to resist engine knock (pre-

ignition from compression). Diesel cetane ratings work in the opposite direction.  Cetane

number is measured in a single cylinder test engine with a variable compression ratio. 

Page 3 of 35

The reference fuels used are mixtures of cetane, which has a very short ignition delay,

and alphamethyl naphthalene which has a long ignition delay.  The percentage of cetane

in the reference fuel is defined as the cetane number of the test fuel. The higher the cetane

rating, the more easily it ignites or the shorter the interval between the time the fuel is

injected and the time it begins to burn.

Cetane number requirements of an engine will vary depending on engine size, speed and

load variations, starting conditions and atmospheric conditions. Since a diesel engine

ignites the fuel without a spark, proper cetane levels are very important. The air/fuel

mixture is ignited by the combination of compression and heating of the air due to

compression. The fuel is injected into the cylinder at the precise time ignition is desired

to optimize performance, economy and emissions. The importance of cetane number is

very evident as low cetane number usually causes an ignition delay in the engine.  This

delay causes starting difficulties and engine knock.  Ignition delay also causes poor fuel

economy, a loss of power and sometimes engine damage.  A low cetane number fuel can

also cause white smoke and odor at start-up on colder days.  White exhaust smoke is

made up of fuel vapors and aldehydes created by incomplete engine combustion.  Ignition

delay during cold weather is often the cause.  There is not enough heat in the combustion

chamber to ignite the fuel, therefore, the fuel does not burn completely. Typical diesel

fuels have cetane numbers in the low to mid 40's.  These are generally satisfactory for

high speed engines while low and medium speed engines may use fuels with lower cetane

number.

B. Volatility

The power and economy of diesel engines are comparatively insensitive to fuel volatility,

unlike spark-ignition engines. There is some indirect impact in that less volatile fuels

have higher heating values (energy content). Conversely fuels with higher front-end

volatility tend to improve starting and warm-up performance and reduce smoke. A

properly designed fuel has the optimum proportion of low boiling components for easy

cold starting and fast warm-up and heavier components which provide power and fuel

economy when the engine reaches operating temperature.  Either too high or too low

Page 4 of 35

volatility may promote smoking, carbon deposits and oil dilution due to the effect on fuel

injection and vaporization in the combustion chamber.  

The fuel volatility requirements also depend on engine design and size, nature of speed

and load variations, and starting and atmospheric conditions.  As an example, more

volatile fuels may provide better performance for fluctuating loads and speeds such as

those experienced by trucks and buses however, better fuel economy is generally

obtained from the heavier types of fuel because of their higher energy content. ASTM D

975 only sets a minimum/maximum range for the temperature at which 90 percent of the

fuel will evaporate. This is referred to as T90, and the range for No. 2 grades of diesel fuel

is 282ºC to 338ºC. This limits the level of high boiling point components that could

lead to increased engine deposits.

C. Viscosity

Viscosity is a measure of a liquid's resistance to flow.  High viscosity means the fuel is

thick and does not flow easily. The viscosity of diesel fuel is an important property

which impacts the performance of fuel injection systems. Some injection pumps can

experience excessive wear and power loss due to injector or pump leakage if viscosity is

too low. If fuel viscosity is too high, it may cause too much pump resistance, filter

damage and adversely affect fuel spray patterns.

The viscosity of the fuel affects atomization and fuel delivery rate.  The viscosity of

diesel fuel is normally specified at 40°C.  Fuels with viscosities over 5.5 centistokes at

40°C are limited to use in slow speed engines, and may require pre-heating for injection. 

For some engines, it is advantageous to specify a minimum viscosity because of power

loss due to injection pump and injector leakage. Maximum viscosity, on the other hand, is

limited by considerations involved in engine design and size, fuel temperature and the

characteristics of the injection system.

D. Fuel Lubricity

Some processes used to desulfurize diesel fuel, if severe enough, can also reduce the

natural lubricating qualities of the diesel fuel. Since engines require the diesel fuel to act

as a lubricant for their injection systems, diesel fuel must have sufficient lubricity to give

Page 5 of 35

adequate protection against excessive injection system wear. Diesel fuel lubricity is a

very important property, since the diesel fuel injection system relies on the fuel to

lubricate moving parts. As with low-viscosity fuels, if lubricating properties are

inadequate, it will lead to increased wear on injectors and pumps.

E. Cold Weather Characteristics

At extreme weather conditions, diesel fuels are blended seasonally and adjusted to

provide ultimate power and performance and minimize cold weather problems which are

inherent to diesel fuel.  As diesel fuel is cooled it will reach the "cloud point".  This is the

temperature at which paraffin wax falls out of solution and starts to form wax crystals in

the fuel. As the fuel is cooled further, it will eventually reach its' "pour point".  This is the

temperature at which fuel will no longer flow or the point at which fuel gels or turns

solid. Another key property of diesel fuel is the "Cold Filter Plug Point" (CFPP).  This is

the temperature where fuel can no longer flow freely through a fuel filter, approximately

halfway between the cloud point and the pour point. How critical these factors become in

winter operation depends on the design of the fuel system with regard to fuel line bore,

freedom from bends, size and location of filters and degree of warm fuel recirculation as

well as the amount and kind of wax crystals. Additives are being used successfully to

improve fuel fluidity at low temperatures.  These additives, known as wax crystal

modifiers, can result in satisfactory fuel flow on average of 9°C to -27°C. 

F. Flash Point

Flash point is determined by heating the fuel in a small enclosed chamber until the vapors

ignite when a small flame is passed over the surface of the liquid.  The temperature of the

fuel at this point is the flash point. The flash point of a diesel fuel has no relation to its

performance in an engine nor to its auto ignition qualities. It does provide a useful check

on suspected contaminants such as gasoline, since as little as 0.5% of gasoline present

can lower the flash point of the fuel very markedly. Shipping, storage and handling

regulations are predicated on minimum flash point of 40◦C. 

G. Sulfur Content

Page 6 of 35

Engine wear and deposits can vary due to the sulfur content of the fuel. Today the greater

concern is the impact that sulfur could have on emission control devices. As such sulfur

limits are now set by the U.S. Environmental Protection Agency (EPA), and those limits

have been incorporated into ASTM D 975. For No. 2 grade low sulfur diesel, the limit is

a maximum of 0.05 percent mass (500 ppm) and, for ultra-low sulfur diesel, it is 15 parts

per million (ppm) maximum.

H. Carbon Residue

Carbon residue gives a measure of the carbon depositing tendencies of a diesel fuel after

evaporation and pyrolysis under prescribed conditions. While not directly correlating

with engines deposits, this property is considered a guide.

I. Ash

Ash forming material may be present in diesel fuel in two forms: (1) abrasive solids and

(2) soluble metallic soaps. Abrasive Solids contribute to injector, fuel pump, piston and

ring wear, and also engine deposits. Soluble metallic soaps have little effect on wear but

may contribute to engine deposits.

J. Acidity

Diesel fuel acidity if not controlled, can cause poor fuel stability, cause corrosion of mild

steel, and it could cause deposit formation in some types of fuel injection equipment.

K. Thermal Stability

Heat transfer is a design function of diesel fuels in many modern diesel engines. Only a

portion of the fuel that is circulated and pressurized by the fuel injection system is

actually combusted. The remainder of the fuel is recycled back to the fuel tank. The bulk

fuel temperature can be well above ambient levels. Inadequate high-temperature stability

of a diesel fuel can result in the formation of insoluble degradation products that can then

cause filter plugging.

In colder temperatures, the recycling of heated fuel back to a colder fuel tank, can cause

condensation problems that could lead to increase in free moisture in the fuel. This

Page 7 of 35

problem could possibly lead to filter plugging and necessitate a higher frequency of fuel

separator filter maintenance and/or drains.

USES OF DIESEL FUEL

Diesel fuel keeps the world economy moving. From consumer goods moved around the world, to

the generation of electric power, to increased efficiency on farms, diesel fuel plays a vital role in

strengthening the global economy and the standard of living. The major uses of diesel fuel are:

• On-road transportation • Farming

• Rail transportation • Marine shipping

• Electric power generation • Military transportation

• Off-road uses (e.g., mining, construction, and logging)

In the United States, on-road transportation, primarily trucks, accounted for nearly 60 percent of

the diesel fuel consumed in 2004. Because diesel fuel is used to move goods from manufacturer

to consumer, its sales are linked to the strength of the economy. Figure 1 shows the percentage

sales of diesel in the U.S.in different sectors.

Figure 1. Diesel Fuel Sales in the U.S. (U.S. Department of Energy, Energy Information

Administration, 2004)

MARKET FOR DIESEL AND ULTRA-LOW SULFUR DIESEL

Page 8 of 35

U.S. refiners produced historically high volumes of distillate fuels and by fine-tuning their

production mix, refineries consistently set record levels of distillate production, topping 5 million

barrels per day (bbl/d) for the weeks ending December 2 and December 16, 2011. In 2011,

weekly distillate production was above the five-year historical range 25 times, and ranked second

highest an additional 19 times. Figure 2 presents the weekly production rate of diesel in America

from the Weekly Petroleum Status Report of U.S. Energy Information Administration.

0 50 100 150 200 250 3000

1

2

3

4

5

6

2006 2007 2008 2009 2010 2011

weeks from 2006 - 20101

mill

ion

barr

els p

er d

ay

Figure 2. Diesel Fuel Weekly Production Rate from 2006 to 2011 (U.S. Energy Information Administration, 2012)

Figure 3 presents the weekly prices of ultra-low sulfur diesel from January 2, 2012, to November

9, 2015 in the East Coast where the state of Delaware is located. These data were reported by the

U.S. Energy Information Administration on their website.

Page 9 of 35

0 50 100 150 2000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

2012 2013 2014 2015Weeks from Jan 02, 2012 - Nov 09 ,2015

East

Coas

t ULS

D (0-

15 p

pm) R

etail

Price

s, Do

llars

pe

r Gall

on

Figure 3. Diesel weekly price in the U.S. East Coast from 2012 to 2015 (U.S. Department of Energy,

2015)

III. Objectives

The main objective of this project is to propose the best design process for the production of

ultra-low sulfur diesel fuel (0.005wt% S). This process takes place in a reactor unit which

contains the supported catalyst for the reaction. For this reason, the reactor unit was chosen as

one of the two equipments that will be designed for this project. After passing through the

reactor unit, the products are separated through the downstream processes. The second

equipment to be designed is a separator equipment that will be used for the downstream

processes.

The project will include the material and energy balances for the whole process and the design

of the reactor and separator units. It will not include the design of the heat exchanger units of

the system, equipment auxiliaries and process control instrumentations. It will also not include

the treatment of the by-products produced.

MAJOR OBJECTIVES

Page 10 of 35

1. Design a reactor that can produce ultra-low sulfur diesel fuel with sulfur content of 0.005

wt%

2. Ensure safe and reliable operations during the production of ULSD.

3. Design a separator that can separate the ULSD from the by-products of the reaction such

as H2S.

4. Establish a material balance at steady-state operation where the total feed mass flow rate

is equal to the total product mass flow rate.

MINOR OBJECTIVES

1. Consider the capital and operating cost for the best possible system that would fit the

product specification

2. Specify process control and instrumentation of the reactor and separation equipment.

3. Provide accurate and detailed utility summary.

IV. Environment, Sustainability, and Safety

ULTRA-LOW SULFUR DIESEL

Ultra-low-sulfur diesel (ULSD) is diesel fuel with substantially lowered sulfur content. As of

2006, almost all of the petroleum-based diesel fuel available in Europe and North America is

of a ULSD type. There is not a single standard set of specifications and as the government

mandated standard becomes progressively stricter so does the definition.

As of 2006, almost all of the petroleum-based diesel fuel available in UK, Europe and North

America is of ultra-low sulfur diesel (ULSD) type. The move to lower sulfur content is

expected to allow the application of newer emissions control technologies that should

substantially lower emissions of particulate matter from diesel engines. This change

occurred first in the European Union and is now happening in North America. New emissions

standards, dependent on the cleaner fuel, have been in effect for automobiles in the United

States since model year 2007. ULSD fuel was proposed by the U.S. Environmental Protection

Agency (EPA) as a new standard for the sulfur content in on-road diesel fuel sold in the United

States since October 15 2006, except for rural Alaska which transferred in 2010. This new

regulation applies to all diesel fuel, diesel fuel additives and distillate fuels blended with diesel

Page 11 of 35

for on-road use, such as kerosene, however, it does not yet apply to railroad locomotives,

marine, or off road uses (American Petroleum Institute, 2015).

ULSD has a lower energy content due to the heavy processing required to remove large

amounts of sulfur from oil, leading to (1 to 2%) lower fuel economy and using it requires more

costly oil. According to EPA estimates, with the implementation of the new fuel standards for

diesel, nitrogen oxide emissions will be reduced by 2.6 million tons each year and soot or

particulate matter will be reduced by 110,000 tons a year (Omidvarbona, Kumar, & Kim,

2014). Sulfur is not a lubricant in of itself, but it can combine with the nickel content in many

metal alloys to form a low melting point eutectic alloy that can increase lubricity. The process

used to reduce the sulfur also reduces the fuel's lubricating properties. The refining process that

removes the sulfur also reduces the aromatic content and density of the fuel, resulting in a

minor decrease in the energy content, by about 1%.  This decrease in energy content may result

in slightly reduced peak power and fuel economy. The transition to ULSD is not without

substantial costs. The US Government has estimated that pump prices for diesel fuel will

increase between $.05 and $.25 per gallon as a result of the transition. And, according to the

American Petroleum Institute (2015), the domestic refining industry has invested over $8

Billion to comply with the new regulations.

ISSUES ON DIESEL FUEL

A. Diesel Engine Smoke

Diesel engine smoke is caused by incomplete combustion.

White smoke is caused by tiny droplets of unburned fuel resulting from engine misfiring

and low temperature.  This smoke should disappear as the engine warms up.

Black smoke could be caused by a faulty injector, insufficient air and overloading and/or

over fueling the engine.

Blue gray smoke is the result of burning lubricating oil and is an indication the engine is

in poor mechanical condition

B. Diesel Fuel Contamination

One of the more common contaminants in fuel is water.  Water gets into diesel fuel

storage and vehicle tanks in several ways including condensation during transportation,

Page 12 of 35

by leakage through faulty pipes or vents and by careless handling.  Water can cause

injector nozzle and pump corrosion, bacteria and fungi growth and fuel filter plugging

with materials resulting from corrosion or microbial growth.  Both vehicle and storage

tanks should be checked frequently for water and drained or pumped as necessary.  In

extreme cases, biocides may be required to control bacterial growth.

In cold winters, ice formation in fuel containing water creates severe fuel line and filter

plugging problems.  Regularly removing the water is the most effective means of

preventing this problem; however, small quantities of a water dispersing diesel fuel

treatment may be used to help prevent line and filter freeze-ups. Most new diesel engines

require almost daily draining of water separators to avoid excessive or critical moisture

build-up.

Dirt is another common contaminant of fuel and may cause poor performance and

extreme wear in fuel pumps.  Fuel tank caps, dispensing nozzles and hoses should be kept

clean to eliminate potential sources of contamination.

C. Diesel Fuel Color

There is no relationship between natural diesel fuel color and such desirable diesel fuel

qualities as BTU/gallon, viscosity, cloud point, cetane number or distillation range. 

Diesel fuel color varies with the crude source, refinery methods and the use of dyes. 

However, if the fuel color darkens during storage, this could indicate oxidation and/or

other sources which can cause operating problems.

D. Blending Lubricating Oil into Diesel Fuel

It was a common practice to blend lubricating oil into diesel fuel to provide added

lubricity for fuel pumps and injectors.  This practice may adversely affect fuel quality

features and could lead to fuel system and piston deposits, increased exhaust emission,

and fuel filter plugging.  This practice may also result in the diesel fuel being out of

compliance with federal regulations or other specifications. Today’s seasonal blends of

ultra-low sulfur diesel fuel are monitored at the refinery level to ensure adequate

lubricity.

Page 13 of 35

Water and sediment contamination is by far the most probable cause of fuel system

failure

WHY DIESEL FUEL IS REGULATED

The amount of sulfur in diesel fuel is directly linked to the amount of pollutants produced when

the fuel is burned in an engine. Higher levels of sulfur increase pollutants. When diesel fuel is

burned in engines, the emissions that result contributes to air pollution that has serious human

health and environmental effects.

Pollutants from diesel exhaust includes:

Soot or particulate matter (PM);

Oxides of nitrogen (NOx) which contributes to the production of ground-level ozone

(smog) and acid rain; 

Hydrocarbons (HC);

Carbon monoxide (CO); and

Other hazardous air pollutants (HAPs) and air toxics.

This air pollutants can cause heart and lung disease and a range of other health effects.  It can

also damage plants, animals, crops, and water resources.

ULSD LEGISLATIONS

It has been critical to the successful development of diesel fuel and diesel-powered vehicles to

have consensus among refiners, vehicle and engine manufacturers, and other interested parties on

the characteristics of diesel fuel necessary for satisfactory performance and reliable operation. In

the United States, this consensus is reached under the auspices of ASTM International (formerly

American Society for Testing and Materials. The name was changed to ASTM International to

reflect the fact that many of the specifications are used in other parts of the world.) The European

Union has also developed specifications for diesel fuels. These specifications are used

Page 14 of 35

extensively in Asia and the Pacific basin countries, with modifications to fit local supply, crudes,

and regulations (Chevron Corporation, 2007).

The required properties of diesel fuel as stated by ASTM D 975 are listed in the Table 3. It sets

the limits (requirements) for the values of its properties. Seven grades of diesel fuel are defined

by the specification where the fuel grades S15, S500, and S5000 refer to the maximum sulfur

content allowed in the fuel expressed in ppm by weight (e.g., S15 refers to diesel fuel with a

maximum sulfur content of 15 ppm). Specification D 975 also contains the standard test methods

used to measure the values of the properties.

Table 3. ASTM D 975 Requirements for Diesel Fuel Oils (Chevron Corporation, 2007)

Property Test Method

S15, S500, S5000 No. 1-D

S15, S500, S5000 No. 2-D

No. 4-D

Flash Point, °C (°F), min D 93 38 (100) 52 (125) 55 (130)Water and Sediment, % volume, max D 2709 0.05 0.05 -

D 1796 0.5Distillation Temperature, °C (°F), D 8690% Volume Recovered:

min 282 (540)max 288 (550) 338 (640)

OrSimulated Distillation, °C (°F) D 2887(Does not apply to No. 1-D S5000 or No. 2-D S15)90% Volume Recovered:

min 304 (572) 300 (572)max 356 (673)

Kinematic Viscosity, mm2/sec at 40°C (104°F): D 445

min 1.3 1.9 5.5max 2.4 4.1 24

Ash, % mass, max D 482 0.01 0.01 0.10Sulfur, ppm (µg/g), max D 5453 15 15 -

% mass, max D 2622 0.05 0.05 -% mass, max D 129 0.5 0.5 2.0

Copper Strip Corrosion Rating, max D 130 No. 3 No. 3 -

After 3 hours at 50°C (122°F)Cetane Number, min D 613 40 40 30

Page 15 of 35

One of the following must be met:(1) Cetane Index, min D 967-80 40 40 -(2) Aromaticity, % volume, max D 1319 35 35 -Cloud Point, °C (°F), max D 2500 Varies Varies -Ramsbottom Carbon Residue, max(% mass on 10% Distillation Residue)

D 524 0.15 0.35 -

Lubricity, 60°C, WSD, microns, max D 6079 520 520 -

Diesel fuel specifications in the European Union are similar, but not identical, to those in the

U.S. For example, the minimum cetane number in Europe is higher and there is a density range

requirement. The EN 590 had been introduced along with the European emission standards. With

each of its revisions the EN 590 had been adapted to lower the sulfur content of diesel fuel –

since 2007 this is called ultra-low sulfur diesel and is presented in the Table 4.

Table 4. EN 590 Diesel Fuel Requirements and Test Methods (Chevron Corporation, 2007)Diesel Specification Parameter Units Limits Test MethodCetane Number 51.0 min EN ISO 5165Cetane Index 46.0 min EN ISO 4264

Density at 15°C kg/m3 820 min to 845 max

EN ISO 3675EN ISO 12185

Polycyclic Aromatic Hydrocarbons % (m/m) 11 max EN 12916

Sulfur Content mg/kg 50.0 max10.0 max

EN ISO 20846EN ISO 20847EN ISO 20884

Flash Point °C >55 EN ISO 2719Carbon Residue (on 10% Dist. Residue) % (m/m) 0.30 max EN ISO 10370

Ash Content % (m/m) 0.01 max EN ISO 6245Water Content mg/kg 200 max EN ISO 12937Total Contamination mg/kg 24 max EN 12662Copper Strip Corrosion (3 Hours at 50°C) class 1 EN ISO 2160

Oxidation Stability g/m3 25 max EN ISO 12205

Lubricity, WSD at 60°C µm 460 max EN ISO 12156-1

Viscosity at 40°C mm2/sec 2.00 min to 4.50 max EN ISO 3104

Distillation EN ISO 3405Vol. Recovered at:250°C % (V/V) <65

Page 16 of 35

350 °C % (V/V) 85 min95% Point °C 360 maxFatty Acid Methyl Ester (FAME) Content % V/V 5 max EN 14078

V. Design Data

A. Desired Production Rate

The feed rate, as stated in the problem in Table 1, is 35 thousand barrels per day (TBPD). From

the mass balances (which will be shown in Task 2), the production rate was determined to be

1,820,085.41 tons ULSD/year. With a density of 845 kg/m3 (European Standard EN 590:2009),

the volumetric production rate is about 2,153,947,231 L/year of ULSD.

B. Desired Product Purity

The ultra-low sulfur diesel to be produced has a sulfur content of 0.005 wt%.

C. Reaction Conditions and Kinetic Data

As stated previously, in designing the HDS unit, the percent hydrodesulfurization (%HDS) is

determined by Equation 4. From the sulfur content of the diesel feed (1.9 wt. %) and of the

desired product (0.005 wt%), the %HDS was found to be 99.737%.

%HDS=[1−(wt %S )product

(wt %S )feed ]×100 % (4)

The reactor conditions of the proposed operation that will be based from processing data

available from an older HDS unit is shown in Table 1.

The diesel blend contains various sulfur compounds as presented in Table 5. The reaction of

these compounds with hydrogen is exothermic and forms H2S which is separated from the

diesel product by the downstream processes.

Page 17 of 35

Table 5. Sulfur compounds of diesel fuel (Axens IFP Group Technologies, 2010)Sulfur compound Structure

Mercaptans RSH

Disulfides RSSR’

Sulfides RSR’

Thiophenic

Benzothiophenic

Dibenzothiophenic

Benzonaphtothiophenic

Benzodibenzothiophenic

In HDS, the most refractive sulfur compounds in the diesel blend are the alkyl-substituted

dibenzothiophenes (DBT) in which the substituents are in the 4 and 6 positions. Consequently,

these least reactive sulfur compounds determine the overall desulfurization rate in producing

ULSD (Knudsen, Cooper, & Topsoe, 1999). The desulfurization reaction of DBT is used as the

Page 18 of 35

representative for all the desulfurization reactions for the rest of the discussion as this is the

rate limiting step.

There are two pathways for hydrodesulfurization reaction: direct sulfur extraction pathway

(hydrogenolysis) and the pre-hydrogenation pathway. Figure 4 shows the hydrodesulfurization

of dibenzothiophene.

Figure 4. Hydrodesulfurization of dibenzothiophene (Knudsen, Cooper, & Topsoe, 1999)

Direct sulfur pathway or hydrogenolysis, involves adsorption of the sulfur compound on the

catalyst surface through the sulfur atom followed by a C-S bond scission. It has a relatively low

hydrogen partial pressure dependency. On the other hand, the hydrogenation pathway involves

saturation of one aromatic ring of DBT through hydrogenation followed by the extraction of

the sulfur atom. This pathway is equilibrium limited which results in low activation energy for

HDS. It also exhibits a high hydrogen partial pressure dependency.

The DBT hydrodesulfurization reaction as shown in Figure 5 is a gaseous reaction where 2

moles of product is produced from 3 moles of reactant.

Figure 5. Hydrodesulfurization reaction of dibenzothiophene

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A change in density is expected because of the change in the number of moles during reaction.

However, since the components that actually react in the reactor comprises only about 1.9 wt%

of the feed it can be assumed that the expansion factor is equal to zero.

Kinetic studies have usually indicated that simple first-order kinetics with respect to sulfur are

the predominant mechanism by which sulfur is removed from the organic material as hydrogen

sulfide (Ancheyta & Speight, 2007). The rate of reaction then can be described by Equation 5.

−r=k CS (5)

For first order reaction with plug flow regime, the performance equation is given by Equation 6

where k’ is the rate constant (hr-1gcatalyst-1), and Xs is the %HDS (Levenspiel, 1999).

k ' τ '=(1+εs ) ln( 11−X s )−ε s X s (6)

Over various types of catalysts used (i.e. Mo/Al2O3, CoMo/Al2O3, or NiMo/Al2O3), it appears

that there is no fundamental difference in the reaction pathway or the mechanism (i.e.

Mo/Al2O3, CoMo/Al2O3, or NiMo/Al2O3) (Topsoe, Clausen, & Massoth, 1996). Also, under

typical HDS conditions, dibenzothiophenes are much more stable than thiophenes and

benzothiophenes and so deep HDS of the high dibenzothiophene content distillates will require

more active catalyst than that of the distillates containing predominantly thiophenes and

benzothiophenes. (Furimsky, 1997). For this reason, rate constant, k, of alkyldibenzothiophene

is used.

D. Correlations

The relevant correlations to be used for the forthcoming calculations is the start-of-cycle

temperature as shown in Equation 2 and the aging rate as shown in Equation 3. The constants

used to determine the start-of-cycle temperature (Tsoc) are listed in Table 2.

E. Equilibrium Data for Flash Vaporization

In a conventional hydrodesulfurization plant, after the products leave the reactor, the gas-liquid

mixture goes to a gas-liquid separator equipment. These are pressure vessels designed to divide

a combined liquid–gas system into individual components that are relatively free of each other

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for subsequent disposition or processing. To separate the liquid and gas components, the H2S-

diesel mixture undergoes flash evaporation.

Hydrogen Sulfide

Equation 7 presents the Antoine Equation parameters for the hydrogen sulfide component

log10 ( P )=A− BT +C (7)

where P is the vapor pressure in bar, T is the temperature in K and the constants are listed in

Table 6.

Table 6. Antoine Constants for H2S (Stull, 1947)

Temperature (K) A B C

138.8-212.8 4.43681 829.439 -25.412

212.8-349.5 4.52887 958.587 -0.539

Diesel

There are various components in the diesel fuel, majority of which are hydrocarbons. The

average chemical formula for common diesel fuel is dodecane (C12H23), ranging

approximately from C10H20 to C15H28 Invalid source specified.. Thus, the equilibrium data as

Antoine parameters are based from dodecane as shown in Table 7.

Table 7. Antoine Parameters for Dodecane Invalid source specified.

Temperature

(K)

Pressure

(Pa)C1 C2 C3 C4 C5

263.57 - 6580.615 –

1.822x106137.47 -11,976 -16.698 8.090x10-6 2

These constants are used for Equation 8 to determine the vapor pressure, Ps.

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Ps=exp(C 1+ C 2T

+C 3 ln T+C 4T C 5) (8)

F. Raw Materials

Diesel Blend

The primary feed of the HDS system is the diesel blend with the composition presented

in Table 8 in the properties section.

Table 8. List of Properties of the Feed Blend Invalid source specified.

Cetane Number 30 – 40Density @ 15°C (kg/m3) 913.9

Sulfur, wt% 1.9Total Nitrogen, ppmw 200

Boiling range (°C) 232-350

The availability of the diesel blend is convenient since it is produced by the company which

is then directly fed to the HDS system to reduce its sulfur content.

Hydrogen

Hydrogen reacts with the sulfur compounds of the diesel blend and thus decreases the sulfur

content of the blend. Since the refinery does not have a hydrogen plant, it is necessary to buy

hydrogen from a third party. There will be three companies that will supply the hydrogen

needed for the HDS process. Table 9 presents the composition of the hydrogen supplied by

the three suppliers.

Table 9. Composition of Hydrogen from Different Suppliers

Main Supplier Secondary Supplier Third Supplier

Company Name Linde Industrial GasesSEFIC (Shanghai Eternal

Faith Industry Co., LTD)

Huixian Tianli Machinery

Co., Ltd

Plant Location Blue Bell, PA, USA Shanghai, China Henan, China

Hydrogen Purity 99.9% vol 99.99% vol 99.99% vol

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Price $6-15 per kg $5-24 per kg $0.35-6.42 per kg

Websitehttp://www.linde-

gas.com/en/index.htmlhttp://www.sefic.com.cn/ http://m.hxtljx.en.alibaba.com/

The primary supplier, Linde Industrial Gases, is conveniently located in Blue Bell which is 109

miles (via I-95 N route) or 121 miles (via DE-1 N route) from Delaware as shown in Figure 6.

The Linde Group is a world leading supplier of industrial, process and specialty gases. Their

products can be found nearly in every industry in more than 100 countries.

Figure 6. Location of Linde Industrial Gases from Delaware (Google Maps)

To ensure availability of hydrogen feed should there be any conflicts with the primary supplier, back-up suppliers are also available which are located in Shanghai, China and Henan, China.

Catalyst

The catalysts used in hydrodesulfurization (HDS) consist of a metal hydrogenation component

on an amorphous, porous support material. The hydrogenation component comprises a

transitional metal usually selected from Groups VIA and VIIIA. Some of the most common

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catalysts for hydrodesulfurization are the NiMo and CoMo catalysts. Hydroprocessing catalysts

are widely available since they are essential for effective and optimal hydrodesulfurization of the

diesel feed. Some of the companies that sell hydroprocessing catalysts are the Haldor Topsoe

(Denmark), Axens (France), Johnson Matthey (United Kingdom), Criterion (USA), Süd-Chemie

(Germany), Albemarle (USA), Grace Davison (United Kingdom) and ExxonMobil Chemical

(USA).

Catalyst Support

The main role of a support in catalysis is to disperse the active phase in order to increase the

specific activity of the catalyst and also makes the catalytic nanoparticles stable and obtain

optimal performance. Some of the most common supports for catalysts are alumina,

silica, titania, zirconia and carbon.

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VI. Input-Process-Output Diagram

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Supported CatalystSupported Catalyst

Hot waterFlue Gas

Fuel Cooling Water

Ultra-Low Sulfur Diesel

Off Gas

HYDRODESULFURIZATIONDiesel Fuel Blend Feed

Hydrogen Feed

VII. Functional Block Flow Diagram

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Ultra-Low

Sulfur Diesel

Off Gas

Diesel Blend

HydrogenSeparationConversion

Feed

Pre-Treatment

VIII. Battery Limits and Basic Assumptions

A. Battery Limits

An industrial process of catalytic hydrodesulfurization of diesel involves the pretreatment of

the feedstock, the catalytic hydrogenation of compounds and the downstream processes. This

proposed equipment design is mainly focused on the catalytic reactor and the gas-liquid

separator after the reactor. It will include the selection of the materials of construction,

sizing/design of reactor and separator units and the power requirements.

The inside battery limit refers to the processes, units and services included while the outside

battery limit refers to those units, processes and services not included for the design of the

catalytic reactor and the gas-liquid separator.

Table 10. Inside and Outside Battery Limits

Inside Battery Limits Outside Battery Limits

Perform an overall and component material and

energy balances for the whole processProduce Diesel Blend

Conduct chemical engineering design on reactor

and gas-liquid separator Recover hydrogen

Conduct mechanical design on reactor and gas-

liquid separator

Construction of reactor and separator

units

Specify equipment auxiliaries (pumps, pipings,

valves)

Design of heat exchanger to utilize the

heat of the products after the reaction

step

Design of piping and instrumentation

Page 27 of 35

MATERIALS ENTERING AND LEAVING THE BATTERY LIMITS

The first equipment in the battery limit is the reactor, in which gasified fuel blend and hydrogen

enters in it. The desulfurization reaction of the fuel blend takes place with the help of a catalyst.

The amount of catalyst that will be used is part on the chemical engineering design of the reactor.

After the reaction, the heat of the product stream is utilized to preheat the reactant. After it

passed the heat exchanger some of the products are already liquid. The product stream will then

be feed into a gas-liquid separator. The gas-liquid separator is used to separate the hydrogen

sulfide which will comprise the gas phase from the fuel blend which comprises the liquid phase.

The further treatment of the hydrogen sulfide and the fuel blend are already outside of our

battery limits.

Table 11. Definition of Incoming and Outgoing Streams

Stream Definition

Incoming Streams

Diesel fuel blend feed

The diesel blend is provided by the

company’s petroleum refinery. The diesel

blend contain several hydrocarbons

(biphenyl, pentane, n-dodecane, pyridine,

etc.). The most dominant component in the

diesel fuel is the n-dodecane.

Hydrogen Feed

The hydrogen feed is 100% pure which is

used to react with the sulfur compounds in

the diesel fuel

Catalyst

The catalyst may be homogeneous or

heterogeneous. It acts as an active site for

the reaction.

FuelFuel is a utility used to operate fired heaters

for the feed pre-treatment process

Cooling Water Cooling Water is a utility used in heat

exchangers to cool down the products from

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high temperatures

Table 11 continued

Outgoing Streams

Off Gas The off gas consist of gas components that

is vent off after the whole process.

Specifically, it consists of the following

components:

Unreacted Hydrogen - An excess of

hydrogen is fed to ensure conversion of

sulfur compounds to Hydrogen Sulfide.

Thus, unreacted hydrogen is included in the

off gas stream

Impurities in Hydrogen Feed - The

hydrogen feed has a purity of 99.99 vol%.

The 0.01 vol% consists of the impurities,

namely, O2, N2, CO, CO2, CH4 and H2O.

These components are assumed to be inert

and are vented off in the off gas stream

Hydrogen Sulfide - The by-product in the

hydrodesulfurization reaction which

contains the sulfur from the diesel fuel

Ammonia - The by-product in the

hydrodenitrogenation reaction. Aside from

hydrodesulfurization, this reaction also

occurs

Hydrocarbons – These consist of small

traces of n-Dodecane, Dibenzothiophene,

Biphenyl, Pyridine and Pentane. The n-

Dodecane is the major component found in

the diesel feed, dibenzothiophene is the

dominant sulfur compound present in the

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diesel feed, and Pyridine is the dominant

nitrogen compound

Table 11 continued

in the diesel feed while Biphenyl and

Pentane are products of the

hydrodesulfurization and

hydrodenitrogenation reactions,

respectively.

Ultra-Low Sulfur DieselThe desired product to be obtained

containing 0.005 wt% sulfur.

Catalyst

When the catalyst degenerates with time, it

would eventually be replaced. The catalyst

life could be determine through its aging

rate.

Flue GasFlue gas is considered as a waste product

from the fuel

Hot Water

The cooling water from the heat exchangers

becomes hot water after heat transfer occurs

between the cooling water and the hot

product streams.

Given in the problem statement, the Delaware Refining Company produces 35,000 barrels of

diesel fuel blend per day that is needed to meet the product specification of the sulfur content of

the diesel which is 0.005 wt % sulfur.

B. Basic Assumptions

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The following are the assumptions to be considered in the subsequent material and energy and

design calculations:

1. The process is operating in steady state condition.

2. The sulfur compounds in the diesel feed can be represented by dibenzothiophene, which is

the rate-limiting reactant.

3. The hydrocarbons in the diesel feed can be represented by n-dodecane.

4. All gas components follow the ideal gas behavior.

5. The impurities in the hydrogen feed which consist of 0.01 vol% are inert compounds that

will not contribute to the reaction and would just be vented off in the off gas stream.

C. Overall Process Operational Mode and Stream Hours

The typical plant operational modes are the batch and continuous operation. For the batch

process, the diesel blend and hydrogen mixture is fed one batch at a time and the products are

also taken one at a time. This type of operational mode is suitable for slow reactions and those

that have a flexible production rate. It has a relatively simple and low capital costs and easy to

clean and maintain. However, this is only suitable for a plant capacity of less than 4,500 tons

per year (Coulson & Richardson, 2005; Douglas, 1988; Towler, 2013). Since the production rate of

this project is 2,153,947,231 L/year which is about 13,550 thousand barrels/yeat (1 barrel =

159 L), the suitable process operational mode for this project is the continuous mode operation.

The feed is continuously fed to the reactor and the products are continuously taken. It is more

energy efficient and can be automated.

Petrochemical plants conduct shutdown regularly for maintenance. During maintenance

shutdown, the production is halted, the materials are removed from the site, all cleaning of the

permitted equipment and storage equipment is completed and equipment are inactivated. For

this project, the duration of maintenance shutdown operation is 1 month (around 30 days)

yearly. This is in comparison of the shutdown operation of Petron which is 2-3 months. Since

our refinery plant has a much lower plant capacity, it is decided that a month of shutdown will

suffice. Hence, the stream hours that would meet the yearly rate of production is 8040 hours

per year (335 days per year).

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C. Plant Location

The Delaware Refining Company is located at 4550 Wrangle Hill Rd, Delaware City, DE 19706,

United States.

Figure 7. Delaware Refining Company Location (Google Earth)

IX. Economic Margin

The economic feasibility of the design project can be determined by considering the costs of the raw

materials that are to be used (diesel blend, hydrogen, and supported catalyst) and the price of the

main product (ultra-low sulfur diesel). Since the diesel blend comes from the plant’s refinery, there is

no need to consider its cost as it will not be bought. The hydrogen and supported catalyst are to be

bought from suppliers near the state of Delaware and the prices of the said raw materials are taken

from the reports of Linde Industrial Gases and PenWell Corporation. The annual consumption are

estimates based from the supply and demand data around the U.S. East Coast.

Page 32 of 35

Table 12. Summary of Main Raw Material and Product Costs

Main Raw Material Annual Consumption (ton/year)

Unit Price ($/ton) Annual Value ($/year)

Hydrogen 38,160c 400a 15, 264, 000

Supported Catalyst 29.35b 15432.34b 452, 939.2

TOTAL 15, 716, 939.2

Main Product Annual Consumption (ton/year)

Unit Price ($/ton) Annual Value ($/year)

Ultra-Low Sulfur Diesel 1, 700, 000c 900c 1, 530, 000, 000TOTAL 1, 530, 000, 000

aLinde Industrial Gases, http://www.linde-gas.com/en/index.htmlbPenWell Corporation. (2005). Catalyst prices, demand on the rise. Oil & Gas Journal.

http://www.ogj.com/articles/print/volume-103/issue-39/special-report/catalyst-prices-demand-on-the-rise.htmlcU.S. Department of Energy. (2015, November 9). Petroleum and Other Liquids. Retrieved from U.S. Energy Information

Administration: Independent Statistics & Analysis: http://www.eia.gov/petroleum/

The economic feasibility of the project is determined by considering the economic margin which

is given in Equation 8.𝐸𝑐𝑜𝑛𝑜𝑚𝑖𝑐 𝑀𝑎𝑟𝑔𝑖𝑛 = 𝐶𝑜𝑠𝑡 𝑜𝑓 𝑀𝑎𝑖𝑛 𝑃𝑟𝑜𝑑𝑢𝑐𝑡 − 𝐶𝑜𝑠𝑡 𝑜𝑓 𝑀𝑎𝑖𝑛 𝑅𝑎𝑤 𝑀𝑎𝑡𝑒𝑟𝑖𝑎𝑙 (8)𝐸𝑐𝑜𝑛𝑜𝑚𝑖𝑐 𝑀𝑎𝑟𝑔𝑖𝑛= $ 1, 530, 000, 000 − $ 15, 716, 939.2𝑬𝒄𝒐𝒏𝒐𝒎𝒊𝒄 𝑴𝒂𝒓𝒈𝒊𝒏 = $ 1,514,283,060.8

It is implied from the obtained economic margin above that the product that will be produced by

this design project has a greater economic value than the raw materials that are to be bought.

This would mean that the operation would be profitable and thus making this design project

feasible for construction and operation.

Page 33 of 35

X. References

American Petroleum Institute. (2015). Ultra Low Sulfur Diesel. Retrieved from Oil & Natural Gas Overview: http://www.api.org/oil-and-natural-gas-overview/fuels-and-refining/diesel/ulsd

Ancheyta, J., & Speight, J. G. (2007). Hydroprocessing of Heavy Oils and Residua. Florida, USA: CRC Press.

Axens IFP Group Technologies. (2010). Hydro-Treating/Hydro-Processing. Industry-Academia Workshop on "Refining & Petrochemicals". Petroleum Federation of India NIT Jalandhar & Lovraj Kumar Memorial Trust.

Chevron Corporation. (2007). Diesel Fuels Technical Review.

Furimsky, E. (1997). Selection of catalysts and reactors for hydroprocessing. Applied Catalysis, 177-206.

Kabe, T., Akamatsu, K., Ishihara, A., Otsuki, S., Godo, M., Zhang, Q., & Qian, W. (1997). Deep Hydridesulfurization of Light Gas Oil. 1. Kinetics and Mechanisms of Dibenzothiophene Hydrodesulfurization. Ind. Eng. Chem. Res., 5146-5152.

Kim, J. H., Ma, X., & Song, C. (2004). Kinetics of Two Pathways for4, 6-Dimethyldibenzothiophene Hydrodesulfurization over NiMo, CoMo Sulfide, and Nickel Phosphide Catalysts. Energy & Fuels, 353-364.

Knudsen, Cooper, & Topsoe. (1999). Catalyst and process technologies for ultra low sulfur diesel.

Levenspiel, O. (1999). Chemical Reaction Engineering. New York, USA: John Wiley & Sons, Inc.

Omidvarbona, H., Kumar, A., & Kim, D.-S. (2014). Characterization of particulate matter emitted from transit buses fueled with B20 in idle modes. Journal of Environmental Chemical Engineering, 2335-2342.

Quale, M. J. (2000, January). Mobil Technology Company.

Reynolds, R. (2007). Changes in Diesel Fuel - The Service Technician's Guide to Compression Ignition Fuel Quality.

Page 34 of 35

Sakanishi, K., Ma, X., & Mochida, I. (1994). Hydrodesulfurization Reactivities of Various Sulfur Compounds in Diesel Fuel. Catalysis Today, 218-222.

Topsoe, H., Clausen, B. S., & Massoth, F. E. (1996). Hydrotreating Catalysis. In J. e. Anderson, Calysis. Berlin Heidelberg: Springer-Verlag.

U.S. Department of Energy. (2015, November 9). U.S. Energy Information Administration: Independent Statistics & Analysis. Retrieved from Gasoline and Fuel Update: http://www.eia.gov/petroleum/gasdiesel/

U.S. Energy Information Administration. (2013). Retrieved from Distillate Fuel Oil Consumption Estimates, 2013: http://www.eia.gov/state/seds/data.cfm?incfile=/state/seds/sep_fuel/html/fuel_use_df.html&sid=US

UFA Co-operative Limited. (2009). Diesel fuel characteristics and resources. Retrieved from Petroleum: http://www.ufa.com/petroleum/resources/fuel/diesel_fuel_resources.html

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