RE-REFINING OF USED LUBRICATING OIL Presented By - Manoj Praharaj Bhatnagar Roll no. 03 Avadhut Palekar Roll no. 52 Pravin Panaskar Roll no. 53 SEMESTER VII DEPARTMENT OF CHEMICAL ENGINEERING BHARATI VIDYAPEETH COLLEGE OF ENGINEERING,
Definition: Lubricating oils are viscous liquids used for lubricating moving part of engines and machines. Ex. engine oils, gear oils, hydraulic oils, turbine oils, grease etc.Functions: Used to reduce friction between moving surfaces. Remove heat from working parts in machinery. Remove wear debris created by moving surfaces. Provide a protective layering on the metal surfaces to avoid corrosion. Removing contaminants from the engine.Production & Demand: Worldwide production of lubricating oil is estimated at 4.3x107 m3/year (11.2x1010 gal/year). Of these volumes, automotive lubricants and industrial/process lubricants each represent approximately one-half. The current lube oil demand in India is of the order of 10 lakh tonnes per year. Out of this, almost 60% accounts for automotive and the rest of 40% for industrial lubricants. In India, entire lube oil production is based upon imported Base oil as Indian crude is predominantly waxy, hence, not suitable for lubricating Base oil production.
Lubricants today are classified into two major groups: automotive lubricants and industrial lubricants. Industrial lubricants can be sub-divided into industrial oils and industrial specialties; i.e., greases, metalworking lubricants, and solid lubricant films. The industrial lubricants category includes the following types: hydraulic, quenching, cutting, metalworking, electrical, and process oils. Lubricating oils from petroleum consists essentially of complex mixtures of hydrocarbon molecules. They are mostly composed of isoalkanes having slightly longer branches and the monocycloalkanes and monoaromatics which have several short branches on the ring. These hydrocarbon molecules generally range from low viscosity oils having molecular weights as low as 250, up to very viscous lubricants with molecular weight as high as 1000.
Detergents They hold acid-neutralising compounds in solution in the oil. They are alkaline and react with the strong acids which form during the combustion of fuel and can cause corrosion. Neutral detergents are also used to impart anti-wear and extreme pressure properties to an oil. Ex. Phenaltes, Sulphonates, Naphthenates. Dispersants Dispersants keep soot and combustion products in suspension in the body of the oil charge and therefore prevent deposition as sludge or lacquer. Ex. PBI (Polyisobutylene) Succinimides. Antioxidants Antioxidants inhibit the processes of decomposition that occur naturally in lubricants as they oxidise in the presence of air. These oxidation processes give rise to formation of sludge resulting in an increase in acidity and viscosity.
Anti-Foam Additives They are substances that prevent foaming. Air entrapment in lubricating oil can cause oil starvation due to the presence of air bubbles at the contacting surfaces. Ex. Silicone Polymers (very low concentrations) Pour Point Depressants Mineral oils contain paraffin waxes that start crystallising at low temperatures. This rapidly increases the viscosity of the oil and leads to faster crystallisation as the temperature lowers. Pour point depressants prevent this rapid viscosity increase. Ex. Polymethylacrylate Polymer Thickeners These additives are used if the viscosity characteristic of an oil at different temperatures needs to be altered. Ex. Didodecyl hydrogen phosphate Corrosion Protection Included to protect vulnerable metal surfaces from atmospheric corrosion. especially when machinery is idle or during overhaul. Ex. Sulphates, Thiourea type chemicals
Used lube oil is defined as the petroleum-derived or synthetic oil which remains after applications in lubrication, cutting purposes etc. After a certain period of useful life, the lubricating oil loses its properties and cannot be used as such in machinery. Build up of temperature degrade the lubricating oils, thus leading to reduction in properties such as: viscosity, specific gravity, etc. Dirt and metal parts worn out from the surfaces are also deposited into the lubricating oils. With increased time of usage, the lubricating oil loses its lubricating properties as a result of over-reduction of desired properties, and thus must be replaced with a fresh one. The Hydrocarbon Composition of Used Lube Oil The hydrocarbon composition of new or used automotive lubricating oil sludge consists primarily of saturated compounds such as linear and branched chain, paraffins, which have at least twice as many naphthenes. Aromatics generally comprise about 10 to 15 weight percent of the hydrocarbon base material. Composition of used oil consists of four major groups, which have average values of 76.7% saturates, 13.2% monoaromatics, 3.7% diaromatics and 6.5% polyaromatic-polar material.
The automotive lubricating oil loses its effectiveness during operation due to the presence of certain types ofcontaminants. These contaminants can be divided into: Extraneous Contaminants Extraneous contaminants are introduced from the surrounding air and by metallic particles from the engine. Contaminants from the air are dust, dirt, and moisture. Air itself may be considered as a contaminant since it might cause foaming of the oil. The contaminants from the engine are: Metallic particles resulting from wear of the engine, Carbonaceous particles due to incomplete fuel combustion, Metallic oxides present as corrosion products of metals, Water from leakage of the cooling system, Water as a product of fuel combustion and Fuel or fuel additives or their byproducts, which might enter the crankcase of engines. Halogenated compounds, originated from solvents and glycols, resulting from anti-freezing compounds, used in engine cooling systems. Products of Oil Deterioration Many products are formed during oil deterioration. Some of these important products are: Sludge: A mixture of oil, water, dust, dirt, and carbon particles that results from the incomplete combustion of the fuels. Sludge may deposit on various parts of the engine or remain in colloidal dispersion in the oil. Lacquer: A hard or gummy substance that deposits on engine parts as a result of subjecting sludge in the oil to high temperature operation. Oil-soluble products: The result of oil oxidation products that remain in the oil and cannot be filtered out and deposit on the engine parts. The quantity and distribution of engine deposits vary widely depending on the conditions at which the engine is operated. At low crankcase temperatures, carbonaceous deposits originate mainly from incomplete combustion products of the fuel and not from the lubricating oil. While, at high temperature, the increase in lacquer and sludge deposits may be caused by the lubricating oil.
Used oils themselves are not toxic. Contaminants such as additives, degradation products, para chloro benzene (PCB) and poly nuclear aromatics (PNA) make them so hazardous. They have high potential to cause damage to the environment by virtue of their persistent nature and potential to spread over large surface areas on land and water. Films of oil prevent light and air from reaching to life forms of all types on land and water. As per the data, one litre of oil can render one million
Oil, in any form, is potentially harmful to the environment. Post- studies of oil spills indicate that it takes up to twenty years for an aquatic environment to return to a healthy condition. Once it has been used by industry or the DIYer, it has even more potential for environmental damage. In aquatic community oil residue tends to settle on the bottom, coating the substrate and whatever organisms live there. When poured on the ground, oil can rapidly migrate through the soil. In both instances bacteria, plants, invertebrates and vertebrates experience physiological stress. Oil film on water can reduce the penetration of light into the water and, consequently, reduce the rate of photosynthesis. When photosynthesis is reduced, oxygen production is also reduced. The oil film may also inhibit the movement of oxygen from the air through the surface of the water. The reduction of dissolved oxygen in the water stresses animals living in the water.
Generally speaking, there are 3 categories for waste oil disposal: 1- Reuse , including re-refining 2- Thermal cracking 3- Incineration / Use as a fuel The first one , is the best one and is the subject of this study . The second one – although produces acceptable (cracked) products , but is not as good as re-refining. The third one produces a lot of ash, which contains heavy metals and pollutes the environment. In disposing used oil, many people use it as a dust cure; that is, for dust prevention. This method of disposal is in many ways unsatisfactory as the lead-bearing dust and run-off, constitute air and water pollution. Another method by which used oil is being disposed is by incineration. This method represents another poor use of such a valuable product, and the attendant emission of probably carcinogenous products, contribute to environmental pollution.
Recycling of used lubricants is now attracting more attention because of thefear of dwindling of world oil reserves and more as a result of the environmentconcern which it posses.The following three distinctive reasons explain the interest in the re-cycling ofwaste lubricating oils: The need to conserve crude reserves. Minimizing unemployment through the building/construction of used lubricating oil recycling plant. The elimination of environment pollution source of used lubricant.Recycling efforts can no doubt minimize non-discriminatory disposal of wasteoils into landfills and surface waters other benefits include: Reduce dependence on Base oil imports saving foreign exchange. Prevent ground water contamination and pollution of surface waters. Preserve natural resources such as coal and crude oil. Reduce sewage treatment costs. Reduce future remedial costs for landfills and disposal sites. Reduce safety risks and hazards associated with extensive stockpiling. Eliminate improper burning of waste oil as fuel, which generates toxic fumes and air pollution.
The re-refining of used oils to lube base oils started in 1935. The principal reasons why re-refining was unable to find acceptance were: - high process costs - and therefore high selling prices compared to relatively low virgin oil prices, - Inadequate removal of carcinogenic polycyclic aromatics. By mid-1960s there were more than 150 small companies re-refining over three hundred million gallons of used oil annually employing the "acid/clay" re-refining process, wherein large amounts of sulfuric acid and clay were used to treat the used oil. The technology produced acceptable, although sub-standard, base oil. It also created substantial hazardous waste by-products, including acid tar and oil saturated clay. In late 1970s, alternative processes were developed to treat the used oil in a more environmentally friendly manner. The first of the "next-generation" technologies was the Phillips Re-Refined Oil Process (PROP). This technology was developed during the energy crisis of the 1970s That process was capable of producing low quality base oils; however, there were still several environmental concerns that arose due to the need to dispose of large quantities of heavy metal laden precipitate and filter media
Physical MethodMechanical Filtration: Mechanical Filtration is widely used methodof re-cycling. Here contaminants are separated mechanically or byabsorption or adsorption by passing through materials of controlledporosity.Vacuums Dehydration: It is a well-known oil-recycling method.Water and oil, for all practical purpose, are immiscible liquids. If notagitated, water introduced into lubricating oil separates readily bygravity.Centrifugal Separation: It is efficiently used in some commercial oilpurifying equipment to separate solids and free water from the oil.The method involves whirling the dirty oil to separate it into layer ofinsoluble contaminants, water and clean oil.Magnetic Separation: Several types of magnetic filters are usedprincipally for the removable of ferrous metal contaminants fromlow viscosity oils and water-soluble oil coolants.
Physio-Chemical MethodThese methods have been developed for those oils, which are heavilycontaminated and re-refining is not possible only by physical methods.Re-refining of the used oils has been practiced over the past fifty years.Among the first commercial approached for this, the ACID/CLAYrefining had been widely adopted in the past. With the ever-increasingawareness towards the cleaner environment, following new ECOfriendly process producing higher yields of re-refining oils have beendeveloped which totally eliminates ACID SLUDGE.Step 1 - DehydrationThe oil is boiled in a closed container to remove the water that has beenmixed into it.Step 2 - Diesel strippingThe dehydrated oil is then fed continuously into a vacuum distillationplant for fractionation. Lighter oils boil off first and are removed,followed by the lubricating oil itself. Other heavier components do notboil in the conditions used.Step 3 - Lube oil distillation and condensationA liquid extraction process then removes any aromatic componentsfrom the oil.By this stage, the oil is identical to refined virgin oil. It is then tested,appropriate
This is the core process for lube oil re-refining. In India, the general practice is to refine waste oil in a batch process. The de-watered oil is heated in a kettle under vacuum. As the temperature in the kettle rises, various cuts are liberated and rise as vapours, to be condensed in a condenser. The condenser, along with the heating kettle, is maintained under vacuum by a vacuum pumping system. The condensed products are available as different products corresponding to various kettle temperatures as mentioned below. Finally, the process ends when the residual material in the kettle does not vapourise, even at a temperature of around 320°Celcius. At this point, the heating in the
Sulfuric Acid Refining (Meinken Process) The sulfuric acid refining process was mostly developed by Meinken. Compared to older acid based methods, various process stages reduce the amount of acidic sludge and used bleaching clay generated as well as increasing the lube oil yield. Due to the acidic sludge problem, acid refining has largely been replaced by other methods. It is a process based on chemical pretreatment. Before the used oil flows into the waste oil storage tanks, it passes through the filters to remove solid impurities. The dewatered oil is treated with sulfuric acid (96%) and the acid refined oil is vacuum distilled to separate lube base oil from the low boiling spindle oil and gas oil. A block flow diagram of re-refining process is shown below. Clay is added to reduce viscosity of oil during acid treatment. However, the sulfuric acid treatment and clay addition produce waste streams like acid tar and spent clay resulting in a problem of waste disposal. In spite of the disposal problem associated with Meinken process, the Meinken technology appears to be very popular. At present, there are about 60 such refiners around the world using the same system.
The principle of this processing step, developed by the Institut Francais du Petrole (IFP), also known as the Selectopropane Process, is the use of propane to extract selectively all base oil components from waste oil. In this process, water-free waste oil from atmospheric distillation is put in an extraction column with liquid propane at 75-95°C. Dirt and insoluble sludge settle out. After extraction, the oil-containing propane is removed from the extractor. Snamprogetti (Italy) has further developed the IFP process by including a propane extraction step before and after vacuum distillation, and by adding a hydrofinishing step which changes the technology to a four-stage process, without clay treatment. The IFP vacuum/distillation and propane/deasphalting plus hydrogenation technology includes: 1. atmospheric distillation to remove water and light ends; 2. vacuum distillation to recover light and medium base oil cuts; 3. hydrofinishing of the vacuum distillates to produce finished base oils; 4. propane deasphalting of the vacuum residue to recover the bright stock fraction; and hydrogenation of the brightstock fraction.The hydrogenation reactor for bright stock includes two catalytic beds. The firstone ensures demetallisation, and the second hydrofinishing of the bright stock. Inthe first stage of the Snamprogetti technology, the light hydrocarbons and water areremoved by atmospheric distillation. In the second stage, all the impurities pickedup by the engine oil, including the additives and partly degraded polymers, areremoved by extraction with propane. In the next stage, the extracted oil isfractionated by vacuum distillation. The vacuum residue is then submitted to asecond extraction stage in which metal content and resinous/asphaltic componentsare further reduced. The base oil cuts from the vacuum residue (bright stock) are
The Mohawk Process (subsequently CEP – Mohawk) using high pressure hydrogenating was introduced in the USA at the end of the 1980s. The first stage of the process removes water from the feedstock. The second stage of the process is thin-film vacuum distillation , at this step light hydrocarbons are removed resulting in a marketable fuel by-product. The third stage, evaporation, vaporizes the base oil, separating it from the additives, leaving behind a by-product called residue. This residue is used in asphalt industry. This is followed by hydrogenation of the distillate at 6900 kPa over a standard catalyst. Special steps realized catalyst life of 8 to 12 months, which was essential for the economy of the process. The Mohawk process features continuous operation, low maintenance, longer catalyst life span, reduced corrosion, and proven technology. A marked reduction in the amount of water which must be treated as effluent as well as the cheaper
The KTI (Kinetics Technology International) process combines vacuum distillation and hydrofinishing to remove most of the contamination and additives. The key to the process is the thin-film vacuum distillation to minimize thermal stress through mild temperatures not exceeding 250 ◦C. The hydrofinisher then removes sulfur, nitrogen and oxygen. The yield of finished base oils is high (82% on a dry waste oil basis). The KTI waste lube oil re-refining process involves a series of proprietary engineering technologies that affords high economic returns without resulting in environmental loads. The main features of the KTI process include: 1. high recovery yield up to 95% of the contained lube oil; 2. excellent product quality; 3. flexible operation with wide turndown capability; 4. no requirement for discharging chemicals or treating agents; 5. absence of non-commercial by-products; and 6. reliable, inexpensive treatment of waste water contained in the wasted lube oil.
The PROP technology was developed by Phillips PetroleumCompany. The key elements of the process are the chemicaldemetallization (mixing an aqueous solution of diammoniumphosphate with eated base oils) and a hydrogenation process. Abed of clay is used to adsorb the remaining traces of contaminantsto avoid poisoning of the Ni/Mo catalyst.
The Safety Kleen process uses atmospheric flashing for removing water and solvents, a vacuum fuel stripper, vacuum distillation with two thin-film evaporators, and a hydrotreater with fixed bed Ni/Mo catalysts.When using high severity the hydrotreater can reduce the content of polynuclear aromatics; it also removes higher boiling chlorinated paraffins.In 1998 the Safety Kleen process was used in the largest waste oil re- refinery in the world (East Chicago, Indiana, USA, plant capacity 250 000 t/a).The Safety Kleen process is, based on a combination of wiped-film vacuum distillation and fixed-bed catalytic hydrotreatment.The process begins by removing the water and light solvents using an atmospheric flash drum.The vacuum column/fuel stripper removes most of the fuel and heavier solvents.The vacuum distillation unit performs the combined functions of separating the lubricating oil from the heavy ends and generating multiple product streams.Chemically non-pretreated waste oil tends to foul heated surfaces over time, so thin-film evaporators are used.The lubricating oil cuts are then hydrotreated over fixed beds of nickel-molybdenum catalyst. The hydrotreating is performed in
The best results with regard to the technical and environmental quality ofthe re-refined oil and the elimination of PAH are provided by a combinationof thin film distillation followed by selective solvent extraction. In thisprocess, the distillate from vacuum thin-film distillation towers equipmentat the re-refinery are finally treated in a lube refinery solvent extractionplant followed by hydrofinishing. After this extraction process, the PAHcontent is lower than that of virgin solvent neutrals.
This innovative re-refining technology has evolved from existing commercial petroleum refinery technology, and involves treating the entire waste oil in a heated hydrogen-rich atmosphere, whereby the yield of recyclable high-quality products is increased by up to 30%, while at the same time eliminating the coproduction of hazardous distillate fractions. Halogenated and oxygenated compounds are destroyed in such treatment, and high-quality, re-usable lighter distillate hydrocarbons are produced, along with purified base oils. The waste oil is mixed with hot hydrogen gas, and then injected into a recirculating heated hydrogen gas stream directly upstream of a metal/solid separator. The hydrocarbon mixture, along with the aqueous contamination, leaves the separator with the heated hydrogen gas, and goes directly to a fixed bed catalytic reactor. The flash drum separates the base oil product from the lighter components prior to condensing the aqueous phase, thus keeping the base oil product dry. Light oil is recovered and fractionated to produce naphtha range products and diesel fuel. The base oil product is stabilised to remove light gases before directing the material to a product fractionator, where light and heavy base oils are produced.
Vaxon (Enpotec fabrication facilities in Denmark) uses three or four vacuum cyclone evaporators and finishing treatment with chemicals for re-refining of lubricating oils. The key step in the ENTRA technology is the special vacuum evaporation in a vacuum linear tubular reactor (single tube). After continuous evaporation by means of rapidly increasing temperature, vapor condensation is performed by fractional condensation. Complete dechlorination can be achieved with metallic sodium. Clay polishing is used as a finishing process. The thermal deasphalting (TDA) process has been developed by Agip Petroli/Viscolube using the technology of PIQSA Ulibarri in Spain. The process is based on chemical treatment to facilitate subsequent deasphalting. The Viscolube technology, also known as thermal deasphalting (TDA)7, is an improvement of a deasphalting process which has been operated for over 15 years by Viscolube Italiana SpA as a 40,000 t/y capacity plant, using propane deasphalting, followed by vacuum distillation and clay finishing. In Resource technology re-refining technology, the used oil is dewatered, heated, and then flashed in an atmospheric distillation column to remove remaining emulsified water and fuel fractions. The dehydrated oil is then heated and transferred to a vacuum flash
Physical and Chemical Tests of Used Lubricating OilStandard chemical and physical tests were used to evaluate the nature and theextent of the contaminants in the used automotive oils. These tests involve thefollowing measurements: Viscosity: viscosity testing can indicate the presence of contamination in used lubricating oil. The oxidation and polymerization products that were dissolved and suspended in the oil cause the increase of oil viscosity. While a decrease in the viscosity of lubricating oil indicates the fuel contamination. Pour Point: pour point is the lowest temperature at which the oil will flow. Low pour point indicates good lubricating oil. Flash Point: flash point is the lowest temperature at which the vapors in air will burn momentarily if ignited by flame or spark. A decrease in flash point indicates contamination by dilution of lubricating oils with unburned fuel. Increasing of flash point indicates evaporation of the light components from the lubricating oil. Acidity or Neutralization Number: this is a measure of the amount of alkali required to neutralize one gram of the oil. An increase in acid number is due to oxidation of lubricating oil. Ash Content: the remaining solid ash, when the oil is completely burned, is a measure of oil purity. Carbon Content: this evaluates the solid residue obtained when the oil is heated to complete vaporization and it refers to the amount of deposit formed. Water Content: this test is done by distillation and indicates the amount of water emulsified in the oil. Fuel Contaminants: this test indicates the amount of fuel diluting in the lubricating oil during automotive operation
Foreign exchange equivalent to 1,500 crores of rupees is spent every year towards procurement of lube base stocks. After a certain period of useful life, the lubricating oil loses its properties and cannot be used as such in machinery. From the total volume of lubricating oils consumed in India, five hundred thousand tonnes of used oil can be collected and recycled to obtain approximately 3.5 lakh tonnes of base oil. The statistics reveal that one barrel of lube base stock is obtained by refining around 30-35 barrels of crude oil. On the other hand, re-refining 30-35 barrels of used lube oils will yield 20-22 barrels of lube base oil. This will result in a forex saving of more than 500 crores of rupees every year. Used oil, a valuable resource, is wasted if improperly disposed off. Used oil can be re-refined and used over and over again after blending with suitable additives and with no compromise on quality. It will effectively conserve valuable oil reserves and will lessen the import burden as our country is totally dependent on lube base oil imports.
Used oil is a pollutant, and, by re-refining, the pollution is reduced. Hence, it should get the status of eco-friendly technology and get grants and incentives from the Ministry of Environment. The quality of thoroughly re-refined oil is comparable with nascent base oils. Hence, it should be Evaluation awarded import-substitute status. While making fresh lubricating oils, blending with 5 - 10% of re- refined base oils should be done for viscosity correction. All such blended oils should be stamped with eco-label/green label to make the public aware about the concept of re-refining. The eco-conscious customers would buy the product with green label. Since re-refining leads to oil conservation, the concept of re- refining should be strongly supported by the Petroleum Conservation Research Association.
Kirk-Othmer’s Encyclopedia of Chemical Technology, vol. 15, vol. 21. Ullmanns Encyclopedia of Industrial Chemistry, Vols. 23. Design Aspects of Used Lubricating Oil Re-Refining by Firas Awaja and Dumitru Pavel MODERN RECOVERY METHODS IN USED OIL RE-REFINING by H. Bridjanian*, M. Sattarin, Research Institute of Petroleum Industry , Tehran Re-refining of Used Lube Oils, An Intelligent and Eco-friendly Option by Mithilesh Kumar Jha, Indian Chem. Engr., Section B, Vol. 47, No. 3, July – September 2005 Techno-economic evaluation of waste lube oil rerefining Muhammad Farhat Ali*, Faizur Rahman’, Abdullah J. Hamdan King Fahd University of Petroleum d Minerals, Saudi Arabia Int. J. Production Economics 42 (1995) 263-273 EVALUATION OF OIL REFINING AND RECYCLING TECHNOLOGIES , US -ASIA ENVIRONMENTAL PARTNERSHIP Major Pathways for Used Oil Disposal and Recycling, by Czeslaw Kajdas, Warsaw University of Technology, Poland