KING ABDULAZIZ UNIVERSITYFaculty of Engineering

Department of Chemical and Materials Engineering

Summer Training CHE 360

Final Report

Company: Saudi Aramco Lubricating Oil Refining Company

( LUBEREF )

Supervisor: Dr.Hisham Ba Meflih

Student’s Name: Suahib Baik

Student’s ID: 0857447

Date of Submission: Thursday 14/8/2014

1- Introduction:

Saudi Aramco Lubricating Oil Refining Company (Luberef) is one of the world’s leading suppliers of High Quality Base Oil to all major oil companies operating in the kingdom and for other international oil companies in different regions such as GCC countries, Middle East and East Africa.

1.1. Luberef History:

Saudi Aramco Lubricating Oil Refining Company (LUBEREF) is a limited liability company established in 1978 under the rules and regulations of the Kingdom of Saudi Arabia.

Primarily Luberef was established as joint venture between Saudi Arabian Oil Company (Saudi Aramco) with 70% share and ExxonMobil with 30% share.

At end of 2007, Jadwa Industrial Investment Company acquired ExxonMobil's 30% interest in the Saudi Aramco Lubricating Oil Refining Company (Luberef) to become the sole partner to Saudi Aramco in Luberef.

1.2. Luberef Location:

Headquarter and Jeddah Refinery are both located in the city of Jeddah on the west coast of Saudi Arabia at the Saudi Aramco Industrial Complex south of Jeddah, 10 minutes from down town and 35 minutes from the airport.

Yanbu Refinery is located in Yanbu Royal Commission City on the west coast of Saudi Arabia, 350 KM north of Jeddah.

1.3. Luberef Production:

Luberef owns and operates two Base Oil Refineries in the Kingdom of Saudi Arabia. The first refinery was established in Jeddah since 1978 and the second one in Yanbu Industrial City started in 1997.

The total base oil production capacity from both refineries is 550,000 metric tons/year. Jeddah refinery is designed at 270,000 MT and Yanbu refinery is designed at 280,000 MT.

The two plants produce high quality Base Oil grades suitable for industrial and agricultural use.

Luberef produces diverse grades of Base Oil of the highest quality to meet industry demand both regionally and internationally.

Luberef Produces 4 Base Oil Grades:

100 SN 2 %

150 SN 18 – 20 %

500 SN 55 – 60 %

BSS 22 – 25 %

Luberef also produces by-Products:

Extract

Wax

Asphalt / Fuel Oil

VGO

1.3.1. Specifications:

Table 1.1: Base Oil Product Specifications - Luberef Jeddah

TEST Units 100 SN 150 SN 500 SN 150 BSFlash Point COC - Min

°C 199 210 227 282

Flash Point PMCC- Min

°C 182+ 200+ 210+ 232+

Furfural Content - Max

PPM 5 5 5 5

Pour Point - Max °C -18 -12 -6 -6Viscosity @ 40 °C Cst 18.5/23.0 28/31 91/101 -Viscosity @ 100 °C Cst - - - 31/33Viscosity Index - Min

- 100 101 97 95

Sulfur Content - Max

WT% 1 1 1.3 1.6

Ash- Max WT % 0.01 0.01 0.01 0.01

1.4. Luberef Marketing:

Luberef is the sole supplier of Base Oil to all major oil companies operating in the Kingdom. These include Fuchs, Mobil, Shell, Petrolube and other customers.

Export of Base Oil to international market started in 1998 from both Jeddah and Yanbu refineries. Luberef markets its products into different regions in more than 15 countries such as GCC Countries, Middle East and East Africa

2. Safety

2.1. Luberef Policy Philosophy:LUBEREF Co. considers the safety and health of its personnel, customers and the protection of its assets and environment in our day to day operations to be of primary importance. Luberef will comply with all applicable EHS (Environmental and occupational health and safety) laws and regulations established by the Kingdom of Saudi Arabia, and recognized petroleum industry safety practices.

2.2. Fire Alarm System:The Company’s, non-coded, enunciator type Fire Alarm System, is to be used to alert the Emergency Response personnel of a fire. Manual pull stations are located in strategic areas of the plant (e.g., the Process Units, the Laboratory, the Truck Loading Rack, and all normally occupied buildings). In non-strategic areas where there are no pull boxes, emergencies can be reported to the Control Room by telephone or by using the hand-held radio. In addition to the Fire Alarm System, each room of the normally occupied buildings has been equipped with a smoke detector.

2.3. Personal Protective Equipment (PPE):

2.3.1. Protective Clothing:

Only approved Protective Clothing can be worn in the Refinery. Approved Protective Clothing is a long-sleeved coverall outfit or pant/shirt (long-sleeved) combination, which is made of 100% cotton material (Note: Cotton/Polyester blend material is not acceptable). Protective Clothing that provides the wearer additional levels of protection, such as Nome or Probing, are not mandatory unless specified in a particular job description. Protective Clothing, which does not meet the above criteria, will not be permitted to be used in the Refinery.

2.3.2. Safety Hard Hat:

Only approved, non-conductive safety hard-hats shall be used in the Refinery. Approved, non-conductive safety hard-hats are those hard-hats, which do not consist of any metal parts and are certified by the manufacturer to meet the requirements of American National Standard Institute (ANSI) Standard. Hard-hats must not be defaced, cleaned with any solvent-like substance, or have holes drilled into it as this will adversely affect the protective characteristics of the safety hard-hat. In addition, a safety hard-hat must be replaced if a crack or break develops.

2.3.3. Eye and Face Protection:

Employee personnel shall wear safety glasses (i.e., those which meet the requirements of ANSI or an equivalent industrial standard) in all process and Tanks areas, including when in transit to or from job site.

The exception to this is when working:

1. Inside control room, cafeteria/mosque/locker room building, offices, Warehouse.

2. Traveling inside an enclosed vehicle.

Contact lenses are not to be worn inside the Company, except when required for medical reasons. Approved impact/chemical resistant goggles and face shields, welding goggles/hoods shall be worn when required by the work being carried out. If in doubt as to the correct eye protection to be worn, check with your supervisor or LUBEREF Safety Section. Eye/face protection is mandatory when in process and Maintenance work areas at all times.

2.3.4. Chemical Splash/Impact Resistant Goggles:

Using a Chemical Splash/Impact Resistant Face-Shield will minimize injury to the eyes, face and neck when working around areas containing acids, caustics and certain solvents if the activity represents a severe exposure to the individual.

2.3.5. Hand Protection:

Injuries to the hand represent approximately one quarter of all reported injuries. The majority of these are cuts and scrapes which can be prevented through regular use of substantial work gloves.

Some types of gloves:

1. General Purpose Leather Work Gloves or Insulated Gloves.

2. General Purpose Rubber or Rubberized Fabric Work Gloves.

3. Chemical Handling Gloves or Welding Gloves with Gauntlet.

2.3.6. Hearing Protection:

Employer personnel inside all operating units of the Company are required to wear hearing protection which offers at least 25-30 dBA of extra protection. Areas which require protection are well marked with signs that state.

2.3.7. Safety Shoe:

Employer personnel shall wear approved steel toed safety shoes or boots when in all areas past the Company’s Plant Gate. Approved safety shoes or boots are those which have been certified by the manufacturer to meet the requirements of ANSI (or an equivalent industrial standard) and have a minimum coefficient of friction rating of 0.60. Open toed shoes, sandals, or tennis/sport shoes are not permitted.

2.4. Work Permit System: The basic purpose of permit system in LUBEREF is to prevent injuries to

personnel.

Protect property from damage.

Avoid fire.

Ensure that all work is carried out in safest possible manner.

Permit specifies the conditions and procedure for safe execution.

There are three types of work permit with specific colors used In Luberef:

1. Cold Work.2. Hot Work.

3. Confined Space Entry.

2.4.1. Cold Work Permit:

The “Cold Work” also covers cold work activities. Cold Work activities are those which will not produce sufficient energy to ignite flammable atmospheres or flash the material (e.g., working with hand operated tools, removing sand, painting, etc.).

2.4.2. Hot Work Permit:

Hot work is any activity which could provide a source of ignition should combustible materials or flammable vapor-air mixtures be present. Hot work includes, but is not limited to, the operation of gas torches, non-explosion proof electric tools with arcing contacts, non-explosion proof electrical lighting, grinders and sandblasting equipment. Pneumatically operated equipment is excluded unless the specific activity can produce a source of ignition (e.g., grinding wheel on pneumatic grinder, etc.). The purpose of the “Hot Work Permit” is to establish a uniform procedure to ensure all equipment has been made safe for employees who are required to work it.

2.4.3. Confined Space Entry Permit:

A confined space is any space with restricted access which could hamper the ability of personnel to enter or leave and/or contain entrapped asphyxiating, flammable, or toxic materials. Confined spaces are not normally entered by or accessible to plant personnel in the course of their routine duties and are sufficiently surrounded by confined surfaces so as to permit the accumulation of flammable or toxic vapors, or oxygen deficient atmospheres. Examples of confined spaces normally include, but may not limited to, storage tanks, tank trucks, process vessels, pits, sewers, ducts, large pipes, furnaces, exchanger shell, and trenches 4 feet (1.23 meters) or deeper. A confined space or similar enclosure shall not be entered until appropriate tests are conducted and the proper permits have been issued and signed (e.g., a “Confined Space Entry Permit”, et. al.).

2.5. Housekeeping:

To minimize slipping, tripping, falling, and fire hazards, each employer is expected to practice good housekeeping during the job at all times and must have clean up their work area before they leave. Such As:

1. Spills must be cleaned up immediately.

2. Debris must be picked up and disposed of properly.

3. Electrical cords, hoses, ropes and wires must be rolled up, properly stored, and/or ……properly disposed of.

4. Valve wrenches and tools must be properly and safely stored (each employee is ……………responsible for cleaning up after himself).

5. The job-site must be left clean and free of debris and hazards at the end of the work ……………period

3. THEORY AND PROCESS OPERATION

3.1. Introduction:

3.1.1. Characteristics of Lube Crude:

In order to understand the lube refining operation, it is necessary to understand something of the make-up of the crude oil we start with. Our crude oil is made up of a broad spectrum of hydrocarbons whose boiling points range from room temperature to over 538°C.

Table 3. 1: Crude Oil Temperatures

93 °C 93 - 204°C 204 - 343°C 343 - 593 °CGAS GASOLINE DIESEL ATMOS. RESID

The material in the crude with boiling points up to 343°C is removed in atmospheric distillation towers of a regular refinery to make fuel gases, gasoline and diesel oil. The remaining unvaporized atmospheric resid, which has boiling points ranging from 343°C to 538°C, is the charge stock for our lube refinery.

This lube feedstock is made up of:

1. Paraffins.

2. Naphthenes.

3. Aromatics.

4. Resins.

5. Asphaltines.

Where:

1. Paraffins make up about one-half of the crude at 371°C but this amount decreases

at higher boiling points.

2. Naphthenes, on the other hand, remain fairly constant throughout the range of

boiling points.

3. Aromatics, which effect on oil's temperature and stability, increase with boiling

point.

4. Resins at the highest boiling points have high molecular weights and high

Figure 3. 1: lube feedstock

343 593 °C

amounts of carbon (C50 - C60) as well as sulfur, nitrogen and oxygen.

5. Asphaltines also at the highest boiling points have even higher molecular weights

and besides sulfur, nitrogen and oxygen carry the majority of the trace metals

found in the crude oil.

3.1.2. Lube Oil Base Stocks:

When we refine lube crude we are essentially trying to separate out two classes of lube base stock - the naphthenes and the paraffins. The other components in the 343°C to 538°C range are not as desirable for lubricating stock. Aromatics are more unstable and the resins and asphaltines are too viscous and contaminated with metals and sulfur.

These naphthenic and paraffinic components are varying in three critical areas: viscosity index, flash point and pour point.

3.1.2.1. Viscosity Index (VI):

Viscosity is a measurement of a material's resistance to flow. It is usually measured in Saybolt Universal Seconds (SUS for short). Of course liquids thin out, or decrease in viscosity, as their temperatures go up. In a lubricant, however, the amount of thinning is critical because this can affect its ability to lubricate successfully. As a result, it is important to know just how fast a lubricant thins out, decreases in viscosity, as temperature goes up. Viscosity index is a way to measure this rate of thinning.

Naphthenic stocks have a relatively low VI, indicating that there is a rapid decrease in viscosity as temperature goes up. Paraffinic stocks are ideal for lubricating automobile engines.

3.1.2.2. Flash Point:

Flash point is the temperature at which a lube stock will vaporize and ignite. This is obviously an important consideration when selecting a stock for high temperature uses. The flash point can be controlled in the distillation tower as we will see later.

3.1.2.3. Pour Point:

A stack's pour point is the lowest temperature at which it will flow and this is one excellent characteristic of naphthenic stocks. Natural paraffinic stocks do not flow below about 15°C and while even processed paraffinic stocks have pour points usually no lower than -18°C natural naphthenic stocks will pour at temperatures as low as -29°C.

Because of their natural low pour point, naphthenes are used in a variety of low temperature applications including refrigeration oils and insulating oils for transformers that operate in very cold climates -52°C.

Table 3. 2: The Properties of Naphthenes and Paraffins

Naphthenes ParaffinsSpecific gravity 0.905 0.887Pour point -29°C (natural) 15°C (natural)

-7°C (processed)Flash point 224°C 246°CViscosity at 37°C 557 SUS 500 SUSViscosity at 98°C 59.1 SUS 63.1 SUSViscosity index 57 100

3.1.3. Lube Refining Process:

Lube refining consists of four basic processes:

1. Vacuum distillation.

2. Propane deasphalting.

3. Furfural extraction.

4. MEK dewaxing.

No chemical reaction occurs in the processes. They are essentially separation steps using either distillation or solubility. The original distillates can be reconstituted simply by recombining the products from the various processes. The fifth process, hydrofinishing, is an optional step and does involve some very subtle chemical changes. It is used to enhance the color and other characteristics of premium lubricants. Using the first four of these processes we can divide up the crude and isolate various characteristics.

3.2. Vacuum Distillation Unit:

3.2.1. Theory:

Vacuum distillation is the first step in lube refining that separates our feedstock into four boiling fractions each of which has a different viscosity and different mix of Paraffins, Naphthenes, Aromatics, Resins and Asphaltines (see figure 3.2). Because the resulting viscosity and mixture grouping cannot be adjusted later in the other refining steps, this vacuum distillation separation must be as exact as possible.

The lightest group out of the vacuum distillation step is the vacuum tower overhead. This material has a boiling range up to approximately 370°C. It is sent back to the fuels refinery to be made into light products.

The second group, light neutral distillate, has a boiling range between approximately 371°C and 454°C. Light neutral distillate is used to make low viscosity oils.

The third group, heavy neutral distillate, with a boiling range from 454°C to 538°C is used to make high viscosity oils.

The fourth group, vacuum resid, won't boil even in a vacuum and will result in a lube base called (bright stock). This vacuum resid contains most of the resins and metals in the crude and all of the asphaltines.

Except for the vacuum resid's resins and asphaltines, the three groups of distilled fractions are similar in make-up (see figure 3.3).

A typical vacuum distillation unit is a metal tower 21 to 24 meters in height that’s run from 1/15 to 1/20 atmospheric pressure. Unvaporized material from an atmospheric

Figure 3. 2: Vacuum Unit Boiling Fractions

343 370 454 538 593 °C

Figure 3. 3: The Three Groups of Distilled Fractions

371 454 454 538 538 593 °C

distillation column is the charge stock for this unit. This atmospheric resid is heated to about 399°C and mixed with steam to help further vaporize the high boiling point hydrocarbons. This liquid-vapor mixture is then introduced into the flash zone near the bottom of the vacuum tower. Some of the resid vaporizes and moves up the column where it condenses on trays according to boiling points.

A special area of packing called the wash zone is located just above the flash zone. This packing section is kept wet at all times. Its purpose is to knock down any entrained material (liquid droplets that are sometimes carried upward with the rising vapors).

The wash zone treatment within the vacuum distillation tower include: vacuum tower overhead, 343 to 371°C boiling range, which is sent back to the fuels refinery; light neutral distillate, a light oil with an average viscosity at 210°F of 44 SUS; heavy neutral distillate, more viscous with an average viscosity of 60 SUS at 210°C. Both the light and the heavy neutral distillates go to storage for further processing. The last fraction is the vacuum resid at the bottom of the column which will be stored and treated in the propane deasphalting unit.

There is another process unit connected with vacuum distillation. This unit is called a stripping column. As the various distillates come away from the vacuum tower, steam stripping removes any low boiling dissolved materials which have condensed at the wrong levels. These materials are sent back to the vacuum tower to be revaporized and condensed on the correct tray (see figure 3.5). The steam stripped lube distillates are then water cooled and stored until further processing.

It is critical that the vacuum distillation tower be run to cut each distillate at the proper boiling point because there is no opportunity for correction later on. The effects of an incorrect cut are significant. For example, if too much low molecular weight/low viscosity oil is left in a distillate fraction the resulting lube will have too low a flash point for some application. On the other hand, too much high molecular weight oil, called a high viscosity tail, can result in too high a wax content and requires additional MEK dewaxing. This additional dewaxing, in turn, slows down the processing of all the other distillates which are time-sequenced through the MEK dewaxing unit. To make matters worse, the presence of a high viscosity tail negatively affects the demulsibility, the ability of oil to separate from water in the lube.

3.2.2. Process:

Process description:

Vacuum tower is used to separate the reduce crude to different distilled products based on different boiling point temperatures.

Reduce Crude (feed):

Reduce crude is the main feed to the vacuum tower which will come from ARAMCO company and stored in a tank. Unfortunately, the reduce crude contains a little amount of water that may damage the pipes and the trays inside the tower and that’s happen because the water molecules will expand by increasing the temperature. To avoid this problem, we need to drain out the water every day from the tank.

Heating the Reduce Crude:

The reduce crude must be heated before it goes to the vacuum tower. So, it will be heated gradually using 8 heat exchangers until the temperature reach to 283°C. After that, the reduce crude will enter a vacuum tower preheater to heat it up to 331°C. Finally, the reduce crude will enter vacuum tower heater to raise its temperature to 400°C and then will enter the vacuum distillation tower. In the vacuum tower heater, a velocity steam will enter with the reduce crude that passing above burners to increase the velocity of the reduce crude that will prevent the formation of cock.

Stripping Column:

It is a column that consist of trays to separate the distillate that comes out from the vacuum tower using steam by evaporating the light materials which will comes out from the top of the column backing to the vacuum tower and the heavy oil will be sucked by a pump from the bottom of the column.

Ejectors:

Figure 3.5: Reduce Crude

Figure 3. 6: Heat Exchanger

Figure 3. 7: Stripping Column

It is the main and important part of the vacuum distillation tower that makes the tower in vacuum state which means 0 barg pressure. The ejector is a pipe having a narrow part and with the help of medium pressure steam the reduce crude will rise and separate through the vacuum tower because of the vacuum.

Pump Around:

We have three pumps around that are distributed along the vacuum distillation tower. These pumps help in controlling the temperature through the tower by cooling some of the flow rate from accumulating trays in the vacuum tower and return it back.

Vacuum Distillation Tower:

Reduce crude is enter to the tower from the bottom with temperature of 399°C and also medium pressure steam is entering the tower to help vaporize the reduce crude. There are three ejectors on the top of the tower that make the tower vacuum with pressure of 0 barg which mean it will help to evaporate the reduce crude to make different distilled grades through the tower.

We will explain the process inside the tower from the bottom to the top where the bottom has the highest viscosity and the top has the lowest.

A. Vacuum Tower Bottom (VTB) stream:

It is the heaviest oil product (Asphalt) that comes out from the bottom of the tower with temperature of 361°C and with very high viscosity. It will be sucked by a pump and will pass through heat exchanger to cool it down. Part of this stream will go back to the tower in order to control the viscosity of the VTB using control valve. The other part will be divided into three streams:

1. Goes to PDA unit as a feed after mixing with offer flash stream.2. Asphalt as a byproduct which will be sent to ARAMCO.

3. Fuel Oil Blend (FOB) will be sent to ARAMCO as a fuel.

B. Over Flash stream:

Figure 3. 9: Vacuum Distillation Tower

Figure 3. 8: Ejector

The temperature of the over flash stream is 370°C and this stream will goes directly to stripping column by gravity where the heavy part will go to the bottom and the light part to the top backing to the vacuum tower. The bottom part will be sucked by pump and cooled down using two heat exchangers. Then, part of the stream will go to the PDA unit and the other part will go to ARAMCO as Fuel Oil Blend (FOB).

C. 500 distillate:

A 500 distillate has a temperature of 307°C and this stream will be divided into two streams. The first stream is called 500H (heavy) which will go directly to stripping column. The second stream is called 500L (light) which is consist of 500H and mixed with amounts of 100 or 150 distillate to reduce the viscosity and then will go to stripping column different from the previous one. Both streams will comes out from their stripping columns using pumps and cooled down using heat exchangers and then mixed together to give the required viscosity. Finally, the mixed stream will be sent to storage tank waiting for next process.

D. 100 and 150 distillate:

The product will be 100 and 150 distillate. The temperature of the 100 distillate is 249°C while the temperature of the 150 distillate is 259°C. The viscosity of 100 is less than the 150 distillate. The 100 distillate that comes out from the tower does not have the required viscosity so it should be mixed with the 150 distillate. The stream that enters to the stripping column either 150 distillate or mix between 100 and 150 distillate to give the 100 distillate product. In the stripping column the light materials will come back to the vacuum tower from the top of the column while the heaviest part will be sucked by a pump from the bottom of the column and cooled down using heat exchanger and then will be sent to storage tank waiting for next process.

E. Vacuum Gas Oil (VGO):

The VGO temperature is 101°C and this stream consist of liquid and gas. The stream will goes to drum where the gas will return to the vacuum tower. The liquid materials will be sucked by a pump from the bottom of the drum and part of the stream will return back to the vacuum tower in order to control the temperature in the tower. The other part will be cooled by heat exchanger then this stream will be separated into two other streams. One of them will be cooled by another heat exchanger and going back to the vacuum tower to control the temperature while the other one will be stored in VGO storage tank and will be sent to ARAMCO.

F. Vacuum Tower Overhead:

The temperature of the light materials is 61°C and it is the top and last product from the vacuum tower. It is in vapor state that will be sucked by three ejectors one by one with the help of medium pressure steam. The first ejector will vacuum the light materials and will be cooled using heat exchanger where the condensed liquid will go to drum while the gas will be sucked by second ejector and the same process will be done for the second and the third ejectors. The outlets of theses ejectors will be collected in one drum and these outlets contain hydrocarbons and water. The gas that not condensed in the heat exchangers will be brought out through the vent. The drum is divided into three parts; the water will be settled in the first part where the hydrocarbons will move to the second part. In the second part, the hydrocarbons will contain a little amount of water so the water will be settled and the hydrocarbons will move to the last part. The water from the first and second part will be sucked by pump and cooled down by heat exchanger and then entering the water stripper in order to separate the liquid water from the hydrocarbon gas. In the last part, the hydrocarbons are almost clear and sucked by pump to send to the tank. The little amount of the water will be settled in the tank and drained off where the hydrocarbons will be sent to ARAMCO.

3.2.3. The quality of the vacuum unit:

A. Reduce crude:

The reduce crude must be free of water so the water should be drained out

frequently.

Distillation curve is used to indicate the quality of the reduce crude at specific

temperatures based on standard curve.

For example, 5% of the reduce crude is evaporated at 100°C for standard. If 10% of the reduce crude evaporated at the same temperature (100°C) that’s mean my crude is light and not qualified. The following curve (Figure 3. 10) just for explain the point.

Figure 3. 10: Temperature VS Percent of Evaporation Curve

B. Distillate Viscosity:

For 100 distillate, the viscosity should be between 23 to 26cs at 40°C.

For 150 distillate, the viscosity should be between 34.5 to 35.5cs at 40°C.

For 500 distillate, the viscosity should be between 12.7 to 13cs at 100°C.

For over flash, the viscosity should be between 64 to 66cs at 100°C.

Distillate viscosity is affected by three parameters:

i. Stripping steam in the stripping column :

As the stripping steam increase, the viscosity will increase.

ii. Temperature of pump around:

As the temperature of the pump around increase, the viscosity will

increase.

iii. Flow rate of pump around:

As the flow rate of the pump around increase, the viscosity will decrease.

iv. Flow rate of the stripping column:

As the flow rate of the exit stream increase, the viscosity will increase.

3.3. Propane Deasphalting Unit:

3.3.1. Theory:

Propane deasphalting is a process for treating the vacuum resid with propane. Since propane is a solvent for paraffins, naphthenes and aromatics, it is used to physically separate them from the resins and asphaltines in the resid. Once the separation is complete, the propane is removed from the paraffins/naphthenes/aromatics stream and reused. The paraffins/naphthenes/aromatics product is called P.D. (propane deasphalted) raffinate and goes to storage to wait for further processing. Graphically the propane

538 593 °C

deasphalting process resembles drawing a horizontal line through the vacuum resid fraction (see figure 3.13).

As you can see, some resins remain in the desirable stock above the line and some aromatics are lost below the line. This happens because this, like every other separation process in the refinery, is not 100% efficient.

At this point we have three fractions each essentially made up of paraffins, naphthenes and aromatics. Each of these fractions is now blocked through the remaining steps in the lube refinery one at a time. In other words, the furfural extraction unit and the MEK dewaxing unit process only one fraction from storage at a time. Once enough of one fraction is processed, the unit is purged and another fraction is processed.

Propane deasphalting is based upon separation by chemical type. Because propane is a solvent for the non-resinous, non-asphaltic part (the paraffins, naphthenes and aromatics) of the vacuum resid charge stock it can be used to separate these from the resins and asphaltenes.

When propane is mixed with vacuum resid, the resulting liquid settles into two separate phases. On the top is the bulk of the propane in which is dissolved the non-resinous, non-asphalted oil. This phase can be drawn off and the propane removed for reuse. The result is propane deasphalted or P.D. Raffinate which is also called deasphalted oil.

The second phase containing all the resins and asphaltines and some dissolved propane is called P.D. Tar. It can be used for the manufacture of asphalt after removal of the propane (see figure 3.15).

In actual practice in the refinery, vacuum resid is introduced at the middle of the deasphalting column and multiple volumes of propane (five to seven times the resid) are introduced at the bottom.

Figure 3. 14: Propane Mix

Figure 3. 15: Propane Cut Line

538 593 °C

The tower is run at between 49°C and 85°C. In order to keep the propane in a liquid state at these temperatures the unit is pressurized to between 400 and 500 Psi.

A counter flow is created in the tower because the lower density propane rises as the heavy resid (which is denser than propane) sinks. This mixes the vacuum resid and the propane. The desirable fractions (paraffins, naphthenes and aromatics) dissolve in the propane while the resins and asphaltines settle to the bottom of the column. These two phases are immiscible liquids (like oil and water) which will not stay mixed.

The propane deasphalted raffinate at the top of the extractor column is removed and pumped through an oil stripper unit. The propane is stripped out, purified, and recycled. After tripping, the P.D. Raffinate is stored for further processing. At the bottom of the extractor column, the P. D. Tar (containing the resins and asphaltines) is pumped away from the column through the asphalt stripper unit to strip, purify and recycle any

dissolved propane and then the P.D. Tar is stored.

3.3.2. Process:

Process description:

Propane Deashpalting Unit is used to separate the Deasphalted Oil (DAO) from Asphalt.

Extraction tower:

Part of stream that comes out from Vacuum Tower Bottom (VTB) and part of over flash stream are mixed together and enter at the top of the extraction tower. The solvent which is propane will entre from the bottom and a medium pressure steam is used to heat up number of coils in order to help in vaporization.

In this process we have two products:

A. DAO Mix:

DAO mix is the product stream that comes out from the top of the extraction tower where 90% of the propane will comes out with the DAO mix which means that the propane is the solvent and the DAO is the solute. In order to separate DAO from propane, we will use evaporator with low pressure steam. So, part of the propane in the product will be evaporated and the rest will enter another evaporator with medium pressure steam for the same reason and then they will be mixed together. Note that, the propane streams have high pressure, it is about 28 bar. After these two processes, the DAO stream still has small amount of propane. So, it enters to stripping tower with medium pressure steam. DAO is sucked from the bottom part of the stripping tower using a pump and then cooled using a heat exchanger for storage where the propane will be evaporated at the top of the stripping tower and then it will pass through a fan to condensate. After condensation, this stream will enter to suction drum in order to separate propane from water where the water will be drained and the propane will enter to a compressor to increase its pressure. Finally, the propane stream will mix with the other propane mixture stream and then will pass through fan for more condensation and then send it to propane storage tank.

B. Tar Mix:

Tar mix is the product stream that comes out from the bottom of the extraction tower where 10% of the propane will comes out with the Tar mix. This stream will pass through five heat exchangers to heat it up and then will enter to a flash drum to separate propane from Tar. Propane will be separated from the top of the drum and cooled down using heat exchanger. After that, fan will be used to condensate the propane and then will be sent into the propane storage tank. Tar stream which is separated from the bottom of the flash

drum will be sent to stripping tower in order to evaporate the rest of the propane using a medium pressure steam. From the bottom of the stripping tower, the tar will be sucked using a pump and then cooled using a heat exchanger. After cooling, this stream will be separated into three streams which are asphalt, FOB and flash oil but note that the FOB stream will pass through another heat exchanger for more cooling before it goes to its storage. On the other hand, the propane will be evaporated from the top of the stripping tower and then it will pass through fan to condensate. After condensation, this stream will enter to suction drum in order to separate propane from water where the water will be drained and the propane will enter to a compressor to increase its pressure. Finally, the propane stream will mix with the other propane mixture stream and then will pass through fan for more condensation and then send it to propane storage tank.

3.3.3. Quantity and quality of DAO mix and Tar mix:

There are two parameters that may affect the quantity:

1. Temperature:

The selectivity of the propane to dissolve in the DAO will decrease as the temperature increase. As a result of that, the quantity, yield and viscosity of the DAO mix will decrease. On the other hand, the quantity, yield and viscosity of the tar mix will increase.

2. Treat Ratio:

Treat ratio is (propane flow / feed flow) and this indicate that if the propane flow increase the treat ratio also will increase. So, more propane will dissolve in the DAO. As a result of that, the quantity, yield and viscosity of the DAO mix will increase while the quantity, yield and viscosity of the tar mix will decrease.

Flash Point of DAO:

The flash point of the DAO is 230°C or above. Note that, the flash point will be less than 230°C in case that the DAO stream still has propane which means there is a problem in recycling propane. So, we need to check three parts consequently in the PDA unit in order to solve this problem:

1. Steam coils in stripping tower.

2. Stripping steam in stripping tower.

3. Propane flow comes out from heat exchanger.

Figure 3. 17: Propane Deasphalting Unit

Figure 3. 17: Propane Deasphalting Unit

Figure 3. 17: Propane Deasphalting Unit

Figure 3. 17: Propane Deasphalting Unit

3.3. Furfural Extraction Unit:

3.4.1. Theory:

Furfural extraction removes the aromatics from each of the three fractions. Furfural is a chemical that is denser than oil and in the formaldehyde family. It is a solvent for aromatics and, when mixed with the fraction, tends to carry the aromatics to the bottom (see figure 3.21).

Now that the three fraction are free of asphaltenes, resins and most aromatics, the final general step is to separate the paraffinic component in each fraction from the naphthenic components. It is worth nothing that in both propane deasphalting and furfural extraction we are setting the bottom boundaries for the product. With MEK dewaxing we will set the top boundaries for each of the three fractions.

The furfural extraction unit uses the chemical, furfural, to dissolve the aromatics out of each distillate stream as it is processed. The furfural, which is a solvent for aromatics, is heavier than oil and has a chemical makeup similar to formaldehyde although more complex.

Figure 3. 22: Furfural Extraction Cut Lines

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Figure 3. 21: Furfural

Furfural is produced by fermenting agricultural wastes (oat hulls, corn husk, sugar can, etc.) and is a light colored liquid with a strong sweet almond-like smell. It can also be synthesized.

When furfural is mixed with a distillate, it dissolves predominantly aromatics out of the distillate and, being heavier than the oil, settles to the bottom of the vessel carrying the aromatics rich stream with it.

Graphically this furfural separation of aromatics looks like figure 3. 24:

No separation is perfect so some of the aromatics remaining in the furfural raffinate and some of the desirable Naphthenes are lost.

In a lube refinery this same reaction is carried out in metal columns 2.1 to 3.7 meters in diameter and from 12 to 30 meters in height. The oil is introduced at the middle of the column and the furfural near the top. The denser furfural moves downward through the oil and the resulting counter flow mixes the two liquids allowing the furfural to draw out the aromatic part of the distillate and settle with it to the bottom through packed ceramic beds.

A second and more recent type of furfural extraction unit is the Rotating Disc Contactor or RDC for short. An RDC unit is composed of a metal column with doughnut shaped rings (stators) welded to the inside of the wall. Discs or rotors are positioned along a long metal shaft located in the center of the column. A motor rotates the shaft and the discs

Figure 3. 23: Furfural Mix

Figure 3. 24: Furfural Cut Line

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and this rotation causes the oil and furfural to be flung outward from the discs towards the wall.

The liquids land on the stator plates and flow back to the shaft. This mixing of the furfural and oil combined with the flow of the lighter oil upward and the heavier furfural downwards provides more contact between the two.

The extract (furfural and aromatics) settles to the bottom of the tower through the packing and is drawn off. The furfural is removed from the extract and returned to the process. The raffinate (plus some furfural) is drawn off the top of the tower. The furfural is removed in a stripping tower and returned to the process. Both the extract and raffinate are stored for further processing.

Whether we use a packed ped or an RDC unit to separate the aromatics from the oil, the raffinate and the aromatics are next sent to a solvent recovery unit that strips the furfural out and recycles it.

The solvent-free raffinate is stored prior to being sent to the next refining step, MEK dewaxing. The second product, solvent-free extract, is used for various applications including carbon black and rubber extender oils.

Figure 3. 26: Rotating Disc Contactor

Figure 3. 25: Furfural Extraction Tower

3.4.2. Process:

Process Description:

Furfural extraction unit is used to separate the aromatic materials from the distillate.

Extraction System:

One grade of the distillate (100, 150, 500 or DAO) will enter to the extraction tower one at the time. First it will pass through heat exchanger to heat it up and then will enter from the bottom of the tower. Because the furfural solvent has higher density than the oil, it will enter from the top of the extraction tower in order to dissolve the aromatic from the distillate.

In this process we have two products:

Figure 3. 27: Typical Furfural Extraction Unit

1. Raffinate Mix:

Raffinate mix (100, 150, 500 or DAO) is the product stream that will comes out from the top of the extraction tower where a 10% of the furfural will comes out with the raffinate mix. Then, the raffinate mix stream will pass through two heat exchangers to heat it up and for more heating this stream will enter a heater so its temperature will be 200°C. After heating, it will enter a flash drum to separate raffinate from furfural. Furfural will be sucked from the top of the drum because of vacuum and cooled down using a fan to enter a dry drum.

On the other hand, the raffinate will comes out from the bottom of the flash drum and entering a stripping tower to evaporate the remaining furfural in the raffinate. By using stripping steam, the remaining furfural will be evaporated from the top of the stripper and then enter a wet drum while the raffinate will be sucked from the bottom of the stripper by a pump and then it will be cooled down using two heat exchangers to store it in raffinate tank.

2. Extract Mix:

Extract mix will be sucked by a pump from the bottom of the extraction tower where a 90% of the furfural will comes out with the extract mix. Because of the high amount of the furfural present, it will be separated using two separation systems.

The first system contains Low Pressure Flash Drum and High Pressure Flash Drum where the second system contains a Flash Drum and Stripping Tower. Extract mix stream has a high temperature so it will be cooled down using five heat exchangers. The stream will enter a low pressure (LP) flash drum in order to separate a little amount of the furfural from the extract.

Furfural will be brought out from the top of the LP flash drum and passing through heat exchanger to heat it up in order to be sent to the furfural tower. From the bottom of the LP flash drum the extract will be sucked by a pump and heat it up using heat exchanger and heater. After heating, the stream will enter a high pressure (HP) flash drum to separate the most of the furfural from the extract. The furfural will be brought out from the top of the HP flash drum and passing through two heat exchangers to heat it up in order to be sent to the furfural tower.

On the other hand, the extract will comes out from the bottom of the HP flash drum and enter to flash drum in order to evaporate a little amount of the remaining furfural from the

extract. The furfural will be brought out from the top of the flash drum to send it to the dry drum passing through fan to cool it. On the other hand, the extract will comes out from the bottom of the flash drum and entering a stripping tower to evaporate the remaining furfural in the raffinate. By using stripping steam, the remaining furfural will be evaporated from the top of the stripper and then enter a wet drum while the extract will be sucked from the bottom of the stripper by a pump and then it will be cooled down using heat exchanger to store it in extract tank.

Furfural System:

There are four streams that enter the furfural tower:

1- Stream that comes out from the Low Pressure Flash Drum.

2- Stream that comes out from the High Pressure Flash Drum.

3- Stream that comes out from Dry Drum.

4- Stream that comes out from Wet Drum.

For the Wet Drum, the furfural is mixed with water because of the steam in the stripping tower. So, we need to recover the furfural. The mixed furfural and water stream will be sucked from the Wet Drum using a pump to send it to the Settler 1 in order to settle the furfural and send it to the furfural tower by a pump while the water and a little amount of furfural will go to another settler which is settler 2.

In settler 2 the settled water will be sucked out using a pump and pass through heat exchanger to heat it up in order to introduce it to water stripping tower. By the help of the steam in the water stripping tower, the remaining furfural will be stripped out from the top of the tower and mixed with the top stream of the furfural tower to condensate theme by a fan where it finally goes to the settler 1 to separate the water from the furfural and the process goes on in a cycle. However, the water will be drained out from the bottom of the water stripping tower.

Finally, the recovered furfural is sucked from the bottom of the furfural tower by a pump to send it to the extraction tower as a feed. Note that, the recovered furfural stream will be divided into three streams where two of the streams will pass through fans to cool it while the third one has a control valve to manipulate the furfural’s feed temperature.

3.4.3. Quantity and quality of DAO mix and Tar mix:

There are two parameters that may affect the quantity:

1. Temperature:

The selectivity of the furfural to dissolve in the extract will increase as the temperature increase. As a result of that, the quantity, yield and viscosity of the extract mix will increase. On the other hand, the quantity, yield and viscosity of the raffinate mix will decrease.

2. Treat Ratio:

Treat ratio is (furfural flow / feed flow) and this indicate that if the furfural flow increase the treat ratio also will increase. So, more furfural will dissolve in the extract. As a result of that, the quantity, yield and viscosity of the extract mix will increase while the quantity, yield and viscosity of the raffinate mix will decrease.

The quantity of the furfural in the Raffinate Tank should not exceed 5 ppm.

The quantity of the furfural in the Extract tank should not exceed 70 ppm.

The temperature of the stream that enters the High Pressure Flash Drum should

not exceed 229°C. If the stream has this temperature or higher then we need to

check consequently on the presence of oxygen.

Figure 3. 28: Furfural extraction Unit

3.5. MEK Dewaxing Unit:

3.5.1. Theory:

MEK dewaxing is used to remove the paraffins from the naphthenics. MEK stands for Methyl Ethyl Ketone and is a solvent for naphhhenic components in each fraction. Graphically the process looks Figure 3.29.

The last major separation process in the lube refinery is Methyl Ethyl Ketone dewaxing. Methyl Ethyl Ketone (MEK) is a solvent for the naphthenic part and a portion of the paraffinic part of the distillate. It leaves behind the most waxy (straight line molecule) paraffins in the form of solid crystals that can be filtered out.

As you can see from the position of the cut line, a considerable part of the paraffin component remains in the naphthenics. These paraffins are of the more highly branched variety and make acceptable lube bases. The part that is removed, the so-called slack wax, is further refined and MEK stripped for use in crayons, food packing and candles.

In the MEK unit the waxy oil is first heated to dissolve any wax crystals that might have formed during storage. Then this heated distillate is mixed with a combination of toluene and methyl ethyl ketone and cooled to 11°C below the lube's desired pour point. For example, -18°C for a -7°C pour point oil - a difficult temperature to achieve in a refinery.

Figure 3. 29: MEK Dewaxing Cut Lines

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Figure 3. 30: MEK Cut Line

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The actual separation filtering is done in a large vat using a rotary vacuum filter (Figure 3. 31 (a)). The filter is a stainless steel drum 30 feet (9.2 meters) long and 10 feet (3.1 meters) in diameter whose outside is covered with a double layer of filter cloth. The mixture of solvent and dissolved oil is sucked through the cloth filter by a vacuum in the lower segments of the slowly rotating.

Once inside the drum, the liquid (naphthenics and some paraffins) is continuously drawn off through a complex system of pipes and valves leaving the waxy crystals outside on the filter (Figure 3. 31 (b)). As the drum rotates, the wax emerges from the vat and gets a sprayed solvent wash to help remove any remaining oil.

When the drum has rotated about half way around, a blast of gas from inside the drum disengages the wax cake from the filter cloth (Figure 3. 31 (c)).

As the drum continues to rotate, a large blade guides the wax away from the drum (Figure 3. 31 (d)).

Once the MEK solvent is stripped from the three dewaxed oil fractions their refining is essentially complete. These base stocks are now ready for blending, mixing with additives, packaging and sale.

3.5.2. Process:

Figure 3. 31 (b): Rotary Vacuum Filter

Figure 3. 31 (c): Rotary Vacuum Filter

Figure 3. 31 (d): Rotary Vacuum Filter

Figure 3. 31 (a): Rotary Vacuum Filter

Process Description:

The MEK unit is used to remove the wax from the base oil 100, 150, 500 or BSS using Methyl Ethyl Ketone as a solvent.

Process flow:

The feed should be heated by heat exchanger using low pressure steam in order to make the size of the crystals (wax) in the base oil homogenous. Then, the waxy oil will be cooled down using two heat exchangers in order to start to introduce the oil to the MEK solvent. The MEK solvent will be injected with the stream that comes out from the heat exchanger to enter two double pipe heat exchangers in order to cool it more and to start the separation of the wax from the oil gradually.

In order to increase the separation of the wax from the oil, we need to decrease the temperature as possible above the freezing point. So, we will introduce the oil into three chillers. After reaching the required temperature, the oil will be collected in a drum waiting to be filtered. The oil stream will be divided into four streams where each stream will enter individual filter. The wax will be collected from the cloth of the filter in a drum and sucked by a pump and heated by a heat exchanger in order to be stored in a wax tank while the oil will be sucked by a pump from inside the filter and collected in oil drum.

The oil will be heated by two heat exchangers to enter to flash drum 1 in order to separate the oil from the MEK solvent. The separated MEK solvent will be cooled down and send it to a solvent drum while the oil will be sucked by a pump and heated to enter to the flash drum 2. The remaining solvent will be separated and sent to the solvent drum while the oil will be sent to evaporator to heat it up for more separation.

The same process will be done in a third flash drum and the oil will be introduced to a stripper to completely remove the solvent by a steam while the oil finally will be sent to a dehydrator to remove the water from the oil and cooled down to store in tanks to be ready for sale

Figure 3. 32: MEK Dewaxing Unit

4. Conclusion

I have learned a lot during this time I spent training at this company. I have experienced the life of an engineer and gained great knowledge.

I can summary my main benefits in these points:

I took a view of how the future job may be like.

I learn how the work environment differs from the study and the collage life.

I learned to always consider safety ahead of me in each step.

I learned that great achievements require great efforts.

It was a great experience. I would totally recommend this company for my friends to train at. It’s a great company and great people working inside from the security guards to managers of sections. I hope I will have a chance on working in this company one day.

References

Luberef Design Manual for Vacuum Distillation Unit, Mobile, 1976.

Luberef Design Manual for Propane Deasphalting Unit, Mobile, 1976.

Luberef Design Manual for Furfural Extraction Unit, Mobile, 1976.

Luberef Design Manual for MEK Dewaxing Unit, Mobile, 1976.

Luberef Process Flow Diagrams, 1976.

Luberef Website (http://www.luberef.com/Pages/Default.aspx)