There are hundreds of commercial crankcase oils marketed today. Obviously, engine manufacturers or users cannot completely evaluate the numerous commercial oils. The performance of a lubricant, ...
API 614 BROCHURE INFO.Full description
Rotating equipmentFull description
PG6581B lube oil system
Refining-Petrochemicals-Chemicals-Engineering ———
LUBE B ASE OIL MANUFACTURING MA NUFACTURING PROCESSES PROCESSES
1
1-
LUBRICANTS Lubricants are made of finished base oils blended with one another and with additives. There are several types of lubricants: -
engine oils industrial oils metal working fluids medicinal white oils greases
The main purpose of a lubricant is to reduce friction: the reduction of friction is accomplished by maintaining a film of lubricant between surfaces that are moving with respect to each other, thereby preventing the surfaces from coming into contact and subsequently causing damage. Besides the reduction of friction, lubricating oils also perform a large number of other functions: removal of heat, prevention of rust and corrosion, dispersion, sealing. These functions are provided by the base oil, and are enhanced by the use of additives in amounts ranging from 1 to 25% or more. The main market for additives is the engine oils. The purpose of these additives is to: -
protect metal surfaces extend the range of lubricant applicability extend lubricant file
The Society of Automotive Engineer , USA has established that twelve viscosity grades are suitable
2
3-
COMPOSITION AND CLASSIFICATION OF MINERAL BASE OILS a - Compos ition (Figure 3) The major types of hydrocarbons present in crude oils are linear paraffins (n-paraffins), branched paraffins (iso-paraffins), cycloparaffins (naphtenes) and aromatics. Mineral base oils consist of two types: the naphtenic and the paraffinic base oils depending on the dominant hydrocarbons type present. The paraffinic base oils are the preferred stocks used for engine oils. The proportion of the various base oils components determines the characteristics of the base oils. Viscosity increases with the length of the carbon atom chain. Most favored crude are paraffinic crude which give good yields of high VI stocks. For certain applications, naphthenic crudes are selected because they yield stocks with little wax and naturally low pour points. b - Classificatio n ATIEL, the Technical Association of the European Lubricants Industry defines 5 base oil groups, of
which 3 are mineral base oils. This classification allows to establish guidelines for interchanging base oils in lubricants. Base oil
Satuates %
Sulfur %
Viscosity Index
3
b - Solvent extrac tion (figure 9) The vacuum distillates and the deasphalted oil (DAO) contain aromatic and naphtenic hydrocarbons which must be removed to increase the viscosity index. The process consists of separately treating each distillate and the DAO with a solvent (furfural, n-methyl-pyrrolidone). The solvent is mixed with the liquid feedstock and dissolves the components to be extracted. The mixture settles in two phases: an extract phase rich in aromatics and a raffinate phase rich in paraffins. Distillates DAO
Solvent Dewaxing
Raffinate (rich in paraffins) Extract (rich in aromatics)
C 8 9 3 2 D C P D
Deep hydrotreating (figure 7) is sometimes used instead of solvent extraction. This process converts aromatics into naphthenes, breaks naphthene rings and isomerizes the linear paraffins. As a result low VI materials are converted to higher VI materials, but the deep hydrotreating markedly reduces the viscosity of the base oil. c - Solvent d ewaxing (figure 10) Solvent dewaxing is used to reduce the n-paraffins content of the base oils in order to improve their low temperature properties and thus preventing wax crystals forming within the normal working temperature range of the lubricant. Each raffinate is diluted and chilled with a mixture of methylethylketone (MEK) and toluene. Wax crystallizes and is removed from the oil by filtration to produce a lube base oil in the – 9 to – 20°C pour point range according to specifications. The slack
4
RECOMMENDED PROPERTIES OF LUBE BASE OILS
• Base oils are blended with additives to yield commercial finished lubricants.
about 20% vol. additives Automotive lubricant
about 80% vol. blended lube base oils
B 2 3 0 B U L D
• RECOMMENDED PROPERTIES FOR BASE OILS - (automotive base oil case)
VISCOSITY
5
6
STRUCTURE TO PROPERTY RELATION FOR HYDROCARB ONS PRESENT IN LUBE OIL CUTS
HYDROCARBON FAMILIES
MAIN PROPERTIES TYPICAL STRUCTURE
DESIRABLE
DETRIMENTAL •
• HIGH VI
LINEAR PARAFFINS
• GOOD OXIDATION STABILITY •
MEDIUM TO
HIGH
VISCOSITY INDEX
BRANCHED
• MEDIUM TO GOOD
HIGH POUR POINT
STANDARD BASE OIL MANUFACTURING PROCESSES 7
Vacuum system Lube base oils
VI Pour point
Distillate 1
Very high VI
High VI
Medium to low VI
High Pour Point
Acceptable Pour Point
Low Pour Point
nP
iP and P with few rings
N-A
LUBE OIL VACUUM DISTILLATION
3
2
VI Pour point
Distillate 2
Very high VI
High VI
Medium to low VI
High Pour Point
Acceptable Pour Point
Low Pour Point
PARAFFINIC BASE OIL MANUFACTURING SCHEME — Block flow diagram —
