Nnpc Mfstp for Rp Lubes Ppp Rev 1 (2)(1)

REFINING PROCESS LUBES

NNPC MFSTP POWER POINT PRESENTATION

LUBES BASE OILS, WAX AND ASPHALT REFINING

o INTRODUCTION

o CLASSIFICATION OF LUBRICANTS

• LIQUID - OILS

• SEMI SOLIDS – GREASES AND THEIR PROPERTIES

o CLASSIFICATION OF LUBE OILS

CONTENT

• CLASSIFICATION

FUNCTIONS

PROPERTIES

COMPOSITION

• NAPHTHENIC

• PARAFFINIC

ADDITIVES

WAXES, THEIR PROPERTIES AND USES

CRUDE SELECTION FOR BASE OILS PRODUCTION

CONTENT

PROCESSING SCHEMES

FEFD STOCK MANUFACTURE

• HIGH VACCUM DISTILLATION UNIT (HVDU)

• PROPANE DEASPHALTING UNIT (PDU)

VISCOSITY INDEX AND COLOR IMPROVEMENT

• FURFURAL EXTRACTION UNIT (FEU)

POUR POINT IMPROVEMENT

• MEK/TOLUENE DEWAXING UNIT (MDU

CONTENT

PRODUCTION OF WAXES

• MEK/TOLUENE DEOILING UNIT (MDOU)

• WAX HYDROFINISHING

• GRADES OF WAXES

PRODUCTION OF ASPHALT

• ASPHALT BLOWING UNIT (ABU)

• GRADES OF ASPHALT : LIQUIDS AND SOLIDS

CONTENT

LUBES BASE OILS AND WAXES REFINING INTRODUCTION TO LUBRICATION

Controls friction and wear. Introduces a friction reducing film between moving

surfaces. May be a Fluid, Solid or Polymer

CLASSIFICATION OF LUBRICANTS Fluids - Oils an gases Solids - Graphite Semi Solid - Greases: Greases are used where liquid lubricants can not

provide required protection.

Easier to apply. Requires little maintenance.

Properties of Greases: Stays in place. Provides sealing action. Provides extra film thickness.

Components: Base Oils. Thickners. Additives.

CLASSIFICATION OF LUBE OILS:• Classification based on sources: Petroleum Lubes. Biological: Animal and Plant Lubes. Synthetic Lubes. Compounded Lubes.

• Petro Lubes most extensively used and classified as: Industrial Lubes: Spindle, Turbine, Machine,

Gear, Compressor Oils, etc. For internal combustion Engines:o Land – Petrol and Diesel Engine Oils.o Marine – Cylinder and System Oils.

o Hydraulic Oil – ATF. Metal Processing – Cutting, Grinding, Rolling and

Pressing Oils. Preservation/Antirust Lubes.• Functions: Antifriction. Coolant. Sealant . Stress dispersion (Load carrying capacity). Rust prevention. Dust prevention. Cleaning / Detergency.

Insulation (Transformer Oil).• Properties; the following properties are required for

proper functioning: viscosity during service should be constant. High flash point. Low pour point. Non-corrosive. Oxidation stability. Satisfactory and stable colour. Low cracking tendency.

• Composition: Naphthenic: o Nil or very low wax content. o Low VI of 25 – 70.o More oxidation stable. Parafinic:o High wax content.o High VI of 75 -105. o Less oxidation stability.

• Additives: Materials are usually chemical compounds added to a base stock to change / improve properties, characteristics and performance.

Low temperature detergents. High temperature detergents. Antioxidants. VI improver. Pour point depressants. Anti-foamers. Emulsifiers. Load carrying improvers for mild and extreme

pressure conditions.

CRUDE SELECTION FOR BASE OILS PRODUCTION

Scale of Operation:• 1 – 2% of total petroleum products consumed.• Refinery output is only 2 -4% of Crude throughput.• Production therefore is concentrated at selected

Refineries to benefit from “Scale of Operation”• Approximate boiling ranges of paraffinic base oil

are:

OILS APPROXIMATE BOILING RANGES (oC)

Light Spindle Oil (LSPO) 100N 370 – 410

Heavy Spindle Oil (HSPO) 150N 410 – 450

Ligh Machine Oil (LMO) 250N 440 – 490

Medium Machine Oil (MMO) 500N 485 – 525

Bright Stock (BS) >525

• For Naphthenic type on the same viscosity level, the boiling ranges are about 20oC less.

Crude oil Composition:• General composition already discussed in Slides

13 – 15 and 18 – 21.• Based on Lube oil production: Paraffinic Crudes give high VI products. Naphthenic Crudes give low VI products.• All finished base oils whatever be the viscosity, VI

and pour point already exist in the Crude Oil.• However, not all crude oils contain high boiling

fractions present in sufficient or desired quantity to be obtained by Refining treatments.

• Hence only selected Crudes are used placing some constraint on the Refinery for the sake of these special products amounting to only 2 - 4% of Crude input.

Processing Schemes (Slide 100) : • High Vacuum Distillation Unit (HVDU) Atmospheric Residue/Long Residue (AR/LRS),

BP 350/3700C, is the starting point. AR is distilled under vacuum (60 – 88mmHg abs

at the column top and 120 – 150mmHg abs at Flash Zone).

Vacuum Gas Oil (VGO) is the topmost stream and is an FCCU feed.

Three or Four lube oil distillates (Waxy distillates) of increasing viscosity LSPO, HSPO, LMO and MMO are withdrawn at selected points down the column.

Waxy distillates are steam stripped in separate strippers to improve separation.

Waxy distillates heavier than spindle oil solidify at room temperature due to high wax content.

Black Vacuum or Short Residue still containing highest viscosity oil (BS) is the column bottom product.

• Propane Deasphalting Unit (PDU) Raw very viscous lube oil (BS) is dissolved o ut of

the Vacuum Residue by counter current washing

with liquid propane in a Rotating Disc Contactor(RDC). RDC temperature gradient: 70-75oC at the top and

39-40oC at the bottom. Base pressure is about 32kg/cm2.

Heavier feed (SG about 0.98) enters from the top and lighter liquid propane (SG 0.47 at 40oC) from the bottom.

Liquid propane dissolves the oil and the Deasphalted oil (DAO) leaves at the tower top (10% wt. Oil, 90% wt. liquid propane).

Propane asphalt (PA) leaving the base contains about 23% wt liquid propane.

The amount of propane used is between 5vols and 10vols/volume of feed stock.

Both streams go to different evaporators and strippers for propane recovery.

Propane vapour from both recovery sections is compressed, cooled and recycled to the RDC.

The DAO is solid at room temperature due to its high wax content.

• Furfural Extraction Unit (FEU) The waxy distillates for HVDU and the DAO from

PDU contain complex polynuclear aromatics. Hence have poor oxidation stability and poor VI.

These undesirable aromatics present in raw lube oils are removed in a counter current Liquid – Liquid extraction process using Phenol or Furfural (most widely used as the solvent).

The solvent preferentially dissolves the aromatics. Operation is carried out in an RDC similar to that

of PDU . The heavier Furfural enters from the top and the

oil from the base of the RDC. Operation is batch wise or block operation, each

feed processed separately.

The extraction temperature at the top and bottom of the RDC and Furfural to oil ratio are adjusted to suit each feed to obtain the required VI.

Typically; Top temperature is about 30-110oC. Bottom temperature ia about 90oC. Ratio: Furfural to oil is 1 vol to 4

vols. More viscous oils require heavier treatments. Stream leaving the top contains 15 – 20% of

Furfural and 85 – 80% waxy Raffinate. The extract stream leaving the bottom contains

80-90% Furfural and 20-10% Extract.

Both streams go through independent solvent recovery and steam stripping to remove all Furfural which is condensed, dried and recycled to the RDC.

By removing 20 – 50% of aromatic extract from the feed, the wax originally present has being concentrated by a corresponding amount.

The oil product is called Waxy Raffinate.

• Solvent MEK/TOLUENE Dewaxing Unit (MDU) Due to the high wax content of the waxy

Raffinates, their pour points are so high that they congeal easily at ambient temperatures.

The wax can not easily be removed by direct filtration because of the high viscosity of the oils.

To separate the wax from oil, solvent extraction followed by chilling then filtration is used.

Most commonly used solvent is a blend of Methylethylketone (MEK) and Toluene – the most moden dewaxing process.

Toluene dissolves the oil and wax, MEK is anti-wax, precipitating the wax and not dissolving appreciable amount of oil.

The solvent mix ratio is 52/48% MEK/Toluene. The waxy raffinate is mixed with solvent (primary

dilution solvent) and heated to a temperature of 25oC to ensure that the wax dissolves completely. The charge mix is then cooled to the filtration temperature, normally around -20oC, with the addition of further amounts of solvent.

The charge mix is chilled in scraped-surface double pipe heat exchangers and chillers.

Heat exchange is with cold filtration and the chilling medium is usually evaporating propane liquefied by cooling and compression.

The chilled mixture goes to the rotary filters where filtration takes place under vacuum in continuous operation.

In the filters, the crystallized wax is separated from the oil in the form of a thin cake which is continuously removed from the drum by blowing back with inert gas.

The size of the wax crystals that form as the feed is cooled influences, in an important way, filtration and washing of the crystallized wax.

Washing is with solvent to recover the oil that remains trapped between the wax crystals.

The total quantity of solvent (usually 3 – 5 vols./vol. of oil) added to the charge oil is governed by its viscosity and the filtration temperature. It is best to use the minmum quantity of solvent to reduce operating cost.

The higher the solvent ratio, the lower the charge oil viscosity and the larger the wax crystals. Large crystals result in good filtration rates but the filter cake will be loose with a high pore volume and consequently, a poor washing efficiency. Small

crystals generally produce tightly packed cakes with lower filration rates but improved washing efficiency.

The dilution solvent can be a added to the oil feed in different ways and in this way the crystal size of the separating wax can be influenced.

The latest development in this field is the mutiple dilution system, in which the solvent is added to the oil charge in increments before and during chilling.

The incremental solvent addition ensures that the bond between the wax crystals is dissolved and thus, no large aggregates are formed. The individual crystals so obtained give an improved filtration rate and owing to the smaller pore volume, the cake will have improved washability characteristics.

It is important that the temperature of the secondary solvent added should be equal to that of the charge mix stream at the point of injection. If the dilution solvent is too cold, “shock chilling” may occur forming fine crystals. Higher temperature partially melts the wax crystals.

The filtrate cake is transferred by conveyors to the wax boots, from where it is pumped to the slack wax recovery section after steam heating.

The filtrate from the outlet of the filters first exchanges heat with the incoming feed mix and then goes to the dewaxed oil recovery system.

In both recovery sections the bulk of the solvent is removed by applying a double-effect evaporation system, additional heat being supplied by hot-oil heaters. From the second (high-pressure) flash column the oil or slack wax is transferred to a steam stripper, where the final traces of solvent are removed.

The solvent recovered from all these sources is returned for further use in the dewaxing process as moist or dry solvent, depending upon the source from which it is recovered.

Any solvent losses are made good by the addition of fresh solvent.

The quantity of wax removed is typically 20 - 25% weight on waxy feed.

Conditions are adjusted to obtain product oil desired pour point usually -10 to -20oC.

Operation is batch wise for each grade.

Three grades of Slack waxes are produced :A grade from 100N and 150N waxy Raffinates.B grade from 250N waxy Raffinates.C grade from 500N waxy raffinates.

BS slack wax is FCC feed component. The Table in the next slide gives typical feed

and product properties:

• Waxes and Their Properties : Solid or semi solid materials made up of a mixture

of HCs obtained or derived from petroleum fractions.

Mostly linear paraffin molecules. Congealing/melting point of between 100oF (38oC)

and 200oF (93oC). Maximum oil content is 50% wt for Raw wax and

0.5% to 1.0% wt maximum for commercial waxes. Uses:o Candle manufacture.o Cosmetics and Pharmaceutical formulations.

o Textile industry.o Paper waterproofing, etc.

• Solvent MEK/TOLUENE Deoiling Unit (MDOU) Slack waxes produced as by-products of refined

lube oils in the MEK Dewaxing Unit (MDU) still contain some oil components as well as undesired low melting point waxes.

The melting/congealing point is always determined because it has direct effect on many characteristics of waxes and their commercial applications. The melting/congealing point is therefore, the main property used for classifying waxes into different grades.

MDOU is designed to produce commercial paraffin waxes by deoiling lube oil slack waxes produced in MDU. The oil product is called Foots Oil.

In order to obtain waxes with the desired melting point and penetration, it is necessary to remove the oil components and the low melting point waxes; in this way the melting point of the deoiled wax will increase and its penetration will decrease meeting the required specification of commercial waxes.

The process used to remove the undersirable oil components from the slack waxes is called deoiling.

The slack waxes are deoiled by using a solvent mixture (MEK and Toluene).

The process used to reduce the oil content in slack waxes (deoiling) is very similar to that of dewaxing which has already been discussed under MDU.

The feedstock is deoiled with a solvent mixture (MEK and Toluene). The principle of the process is that the feed is mixed with the solvent and chilled to a certain temperature and the wax which is crystallized at this temperature is separated from the oil by filtration through a rotary vacuum filter.

Everything regarding choice of the solvent is equally valid. In this particular case, use is made of a MEK/Toluene mixture, the composition of which varies from 60/40 (normal) to 70/30.

Methyl Ethyl Ketone is the agent which precipitates the waxes, i.e. given that waxes are barely soluble in it, as the temperature falls they separate in the form of crystals of a size suitable

for the subsequent filtration. However, as its solvency versus oil is also limited, a large quantity of oil would also separate with the waxes. The purpose of using toluene with the MEK is to

keep the oil in solution, at the same time reducing its viscosity at low temperatures to aid separation during filtration. Toluene on its own would tend to dissolve even large quantities of waxes, but the presence of MEK prevents this.

The purpose of washing the wax cake is to remove the oil and the soft wax that remain blocked between the wax crystals; it is thus obvious that

large crystals withhold large quantities of unwanted compounds which worsen the properties of the finished wax (e.g. the melting point falls and penetration increases).

In the multiple dilution system, the solvent is added to the feed in incremental amounts before and during chilling.

For a particular slack wax feed the filtration temperature governs the melting point, penetration and yield of deoiled wax. When the filtration temperature is increased, the wax melting point is increased, the penetration is reduced and the wax yield is reduced.

The opposite is the case when filtration temperature is decreased.

Feed and product Hard Wax are shown in the Table in the next slide.

GRADES

PROPERTIES A B C

Slack Wax

Hard Wax

Slack Wax

Hard Wax

Slack Wax

Hard Wax

Flash Point (oC) 195 195 220 220 225 225

Congealing Point (oC)

48 48 – 54 54 59 -62 60 66 – 70

Max. Oil Content (%weight)

15 0.5 20 0.5 25 1.0

WAX HYDROFINISHING UNIT (WHU) A hydrotreating unit at 250-400oC, 50-110kg/sq.cm. Catalyst is Ni/W on alumina support. Reduces mainly Aromatic compounds by de-

aromatization (Hydrogenation of aromatics). Reduces also amount of O, N and S compounds. Hydrocracking and Isomerization are minimised to

avoid off-spec (oil content and congealing point) wax.

Batch operation to produce grades A, B and C white commercial waxes.

ASPHALT BLOWING UNIT (ABU) Asphalt is an amorphous dark brown to black,

odorous, cement-like, combustible mixture of fused polynuclear aromatics with cross-linkages made of methylene, ether and thioether bonds.

Obtained from petroleum processes and insoluble in most pure hydrocarbons.

Raw asphalt has poor charateristic; high penetration, very low softening point and other qualities.

Asphalt together with Resins (materials of similar composition but of linear polymers and hydrocarbons soluble) make up 5 – 15% of Crude Oil.

The oil fraction in asphalt is a mixture of oils similar to very heavy lube oils.

Resins are solids and semi solids. The solid fraction is called Asphaltene which is

responsible for the consistency of asphalt: the more the asphaltene content the higher the viscosity and softening point but the lower the penetrattion.

Hence properties of asphalt vary over a wide range depending on the properties and the nature of the various constituents.

Sources of Raw Asphalt:• Distillation: HVDU.• Air Blowing: ABU.

• Precipitation or Solvent Extraction: PDU. Distillation and Precipitation remove relatively fluid

oils and waxes without chemical conversion Air blowing produces changes in asphalt by

chemical reaction thereby improving on the penetration and softening point specifications.

Therefore, blown asphalt is harder and brittle. Crude Oil composition is vital in refining for asphalt

because asphalt yield is practically set by Crude Oil composition while the quality is subject to processing.• API gravity and carbon residue values can give a

rough index of the amount of asphalt in Crude Oil.

Air blowing feed is a blend of FEU extracts (250N, 500N and BS), PAS and Vacuum Residue -1 and -2 in a ratio which depends on the desired product asphalt quality.

Kinds of Products:• Solid grade: 80/100 Penetration.

60/70 Penetration.50/60 Penetration.

• Liquid (Cut back) grade: Medium curing (MC). Rapid curing (RC).

Solid grades are usually produced by air blowing although 80/100 grade can also be produced by direct blend of PAS and Vacuum Residue - 2.

Liquid or Cut back grade is produced by blending a petroleum solvent with asphalt:

• Volatile solvent like naphtha gives Rapid Curing (RC) grade which hardens very quickly due to the solvent which evaporates easily.

Medium Curing (MC) grade uses less volatile solvent like kerosene to blend and hence hardens less quickly.

RC and MC grade is each divided into 6 sub grades numbered 0, 1, 2, 3, 4 and 5 depending on the amount of solvent used in blending.

The 0 sub grade has the greatest amount of solvent and is most fluid, the 5 sub grade has the least amount.

The same sub grade in each class has the same fluidity i.e. RCO and MCO have the same fluidity but differ only in the length of time required for the solvent to evaporate.

Solid Grade Product Quality: Solid Grade Product Quality:

Softening Point is determined using Ring and Ball tester and is the temperature at which the ball placed on a ring of heated asphalt falls through the ring and it varies from 45oC for 80/100 to 58oC for 50/60 grade.

Penetration is a measure of hardness and is the distance a needle under a standard load will penetrate the asphalt in 5 seconds at a specified temperature, usually 77oF (25oC), measured in 1/10mm unit. The expression “50/60 Pen asphalt” refers to an asphalt with a hardness of between 50 and 60.

Flash Point varies from 225oC for 80/100 to greater 250oC for 50/60.

Fundamentals of ABU The unit comprises of four (4) Sections: the

Oxidizer, the Hot Oil System, Oil Scrubbing System (to recover cracked oil) and Fume Incinerator to burn foul smelling spent gases.

Air blowing is an oxidation reaction carried out in the oxidizer column.

The main reaction is dehydrogenation by the oxygen in the blowing air and generation of water from reaction with hydrogen from the dehydrogenated hydrocarbon in a Condensation polymerization reaction.

Air blowing increases the asphaltene content at the expense of resins and oils leading to higher softening point and lower penetration.

The reaction is exothermic and temperature rises as the air rate increases. Temperature control is therefore vital and usually kept at 300oC maximum.

Product properties depend on reaction temperature, air rate and feed characteristics. Hence operated at appropriate conditions to produce products with desired properties.

Flow through the oxidizer is counter current:

Asphalt from the top and air blowing from the bottom.

Asphalt product stream is withdrawn from the bottom and cracked oil vapour and gases from the top. The oil is scrubbed to recover it as FCCU feed. The scrubbed overhead vapour is burnt in the Incinerator.

Asphalt Blending: Only cut back and 80/100 grades are blended. In-line blending is carried out based on laboratory

bench result to determine components ratio and regular tests for softening point, penetration and flash point are carried out as control measures.

SSCHEMATIC PROCESSCHEMATIC PROCESS F FLOWLOW D DIAGRAMIAGRAM OFOF L LUBESUBES PPLANTLANT

AsphaltAsphalt

Base Base OilsOils

WaxesWaxes

PropaneDe-asphalting

VDU-2VDU-2VDU-2VDU-2

Asphalt Blowing

MEK-DeoilingMEK-Deoiling

WAXHydro-

Treating

WAXHydro-

Treating

FUELSFUELSPLANTPLANTFUELSFUELSPLANTPLANT

CDU-2CDU-2CDU-2CDU-2

Naphtha

Kero

Gas oil

ATM Residue-2

Sh

ort

Re

sid

ue-

2Waxy Distillates

100N150N150N500NBright Stock

GRADES A,B & C

GRADES50/6060/7080/100

Lubricating Oil Complex: KRPCCapacity is 50,000bpsd-Paraffin-Base foreign Crude

CRUDE AND PRODUCT HANDLING FACILITIES

KRPC receives both local and foreign crude from Warri through a 606 km pipeline.

Four crude tanks each are available for Local and Foreign crudes.

Each set of crude tanks has a capacity of 327,600 barrels or 6.5 days feedstock for Fuels Plant at 60,000 Barrels Per Stream Day(BPSD).

A total of 166 tanks are available to handle crude, intermediate and finished products.

Product evacuation is by Road, Rail and Pipeline.

Capacity to load 192 trucks of 33,000 litres each daily.

57

STORAGE VESSELS – CRUDE OIL TANKS

CRUDE OIL TANKINTERMEDIATE PRODUCT STORAGE TANK

58

SEPARATION VESSELS

Distillation Columns:Vacuum distillationAtmospheric distillationPressure Distillation

Vacuum Column Atmospheric Column

TANKAGE

TANK TYPES

Low Pressure : Cone Roof

High Pressure: Floating Roof

Spheres

Spheroids

Hemispheroids

Gas Holder

Safety: Flame Arrestor/Breather Valve

60

Sizing or Capacity (how long and for what service?)

Is it hot or very cold service (temperature sensitive) –

lagging required?

It must have nozzles for inlet and outlet plus side streams

and sensors

It must breathe – very important for self protection (over

pressure and underpressure can both be experienced)

It must be accessible

It must be supported

Labels

Drains and Utility Connections

FEATURES ASSOCIATED WITH VESSELS OPERATION

61

A TYPICAL DRUM

A HORIZONTAL DRUM

A VERTICAL DRUM

62

AS OPERATOR YOU MUST:

Know the service of the vessels you operate – what does it handle.

Understand the conditions inside each vessel.Know the accessories and the linkages.Understand the location – does it pose any

threats? Is it near heaters?Are associated auxiliaries well Located? Can

they be seen and serviced.Where the vessel drains to.How much material the vessel holds.How to prepare the vessel for entry.Grasp the associated risks with the vessel.

Asphalt Asphalt is used for road pavement and as roofing materials, it must be inert to most chemicals and weather conditions.

Lubricants Special refining processes produce lubricating oil base stocks. Additives, such as demulsifiers, antioxidants and viscosity improvers, are blended into the base stocks to provide the characteristics required for motor engine oils, industrial greases and other lubricants.