Refining of used Lube Oil

Refining of Used Lube Oil

Published On 22/06/2018

By Dr. Yashpal Singh

The Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016 defines a Hazardous waste as any waste which by reason of characteristics such as physical, chemical, biological, reactive, toxic, flammable, explosive or corrosive, causes danger or is likely to cause danger to health or environment, whether alone or in contact with other wastes or substances. An inclusive list has also been provided in the schedule to the notification no GSR 395(E) dated 04-04-2016.

Industrial operations using mineral or synthetic oil as lubricants in hydraulic systems or other applications have been included as ‘Processes’ generating Hazardous wastes at S.NO. 5 of schedule 1 to the notification and used or spent oil, wastes or residues containing oil and waste cutting oils defined as Hazardous wastes. Apart from prevention, minimization and safe disposal, reuse, recycle and recovery are some steps that the occupier has to follow in the management and handling of hazardous wastes. Provisions also exist for the establishment of Common treatment, storage and disposal facilities for hazardous and other wastes in the state. {See also Hazardous and other wastes (Management and handling rules) 2016, www.wealthywaste.com /laws and procedures}.

Waste mineral oils unfit for their original intended use are also included under class A 3020 (Basel No.) and is included as a waste under Annexure VIII of the Basel convention, as a waste applicable for import and export with prior informed consent. This cannot be allowed to be imported without permission from the MoEF and CC, Government of India and the Directorate General of Foreign Trade License if applicable. Annexure VIII of the convention provides a list of wastes regarded as Hazardous under the Basel Convention.

The Basel Convention which had included provisions on the movement and disposal of Hazardous Wastes was adopted on 22^nd March, 1989. The convention entered into force in 1992. The convention covers ‘Hazardous and Other Wastes” (Household and incinerator ash). As per the convention, Hazardous wastes must not be exported to Antarctica, to a state which is not party to the convention or to a party having banned the import of hazardous wastes. The regulatory system of the Basel convention, as also adopted by India, mandates that before an export takes place, the authorities of the State of export will notify the authorities of the State of import or transit providing them with details on the intended movement. Used Lube oil is included in this and therefore import or export will have to follow the principle and provisions of informed consent.

Lubricant oils may contain about 90% base oil, generally petroleum fractions also referred to as mineral oils with the remaining fraction being composed of additives like anti oxidants, metal deactivators, anti-foaming agents, Viscosity improvers, de-emulsifying and emulsifying agents etc. After a certain period of useful life, lubricating oils lose their properties and cannot be used further because of accumulation of contaminants and chemical changes. The base oil however retains its properties.

True recycling, also known as re-refining, means separating the ‘Lube Oil’ or base oil from all impurities which have accumulated on use.  Filtering used oil to remove solids or drying used oil so that it burns better is not recycling.

While re-refining of used oil is a viable proposition yet a major portion finds its way into the environment and presents problems of surface and ground water pollution and land contamination. Unless controlled, it can also impair the working of effluent treatment plants.

Refining of used lube oil is a highly sustainable option which reduces dependence on virgin lube oil which has a huge energy and carbon foot print (almost 3 times more energy consumption as compared to re-refining). It also has the advantages of reducing oil imports, preventing ground water and land contamination, reducing costs of effluent treatment. By refining the used lube oil, the burning of used lube oil is also regulated and the consequential severe air pollution problems are avoided. The improper disposal of used spent oil may create severe environmental problems. If discharged on land it penetrates the soil and poisons plants and animals. A five liter can of spent oil ( generally after a car servicing) reaching a water body  has been claimed to spread over 5000 sq. meter of water surface and kill all life forms by preventing  oxygenation.

A number of options currently exist for the disposal of used oils.

1. Laundering which involves the process of heating, filtration, dewatering under vacuum, adding additives and then sending back to the user for reutilization. Hydraulic and cutting oils or oils of known source and contamination can be reused.
2. Segregating used industrial oils and reusing them after centrifugation or filtration.
3. Burning Waste oil without any pretreatment in cement plants or using as an economical heating source (in some places in Europe) by burning in small space heaters like garages etc. It can also be burnt in chemical/Hazardous waste incinerator. Air Pollution is a problem here, however in the case of reuse by burning in cement plants, air pollution is minimized by the wastes being incorporated in the product and the gases being cleaned in the kiln itself.
4. Waste oil is sometimes usefully burnt after mild reprocessing. Here, water and sediments are settled after mixing used oil with a demulsifier. Settling is facilitated by heating the tank to 70⁰ to 80⁰ If necessary the clear oil is decanted and passed through a series of filters. The waste water and sediments are appropriately disposed after treatment.

The processed oil may also be blended in to fuel oil. The processed oil may also be used for drying limestone and other rocks for road building purpose. It has also been used in certain power plants as a start up fuel.

1. Waste oil is often also burnt after severe reprocessing which may involve removal of water through flash columns, removal of light fractions and oil by distillation and the production of reusable residues (in road building)
2. And the re-refining of used lubricating oil back to virgin base oil substitute.

A number of re-refining technologies are available which are based on the principles of

1. Vacuum distillation, Wiped Film Evaporation and Hydrofinishing, where the oil is pretreated for the removal of corrosive components and components that may cause fouling of equipment.

This pretreated oil is distilled for the removal/ separation of water and light hydro carbons. Water is treated and sent to waste water treatment facility. The light hydro carbons are used as fuel or sold as a byproduct.

Dehydrated oil, thereafter, is subjected to vacuum distillation in a thin film evaporator for the separation of diesel which can be used in plant or sold. Heavy materials such as residues, metals, additives, degradation products are separated and can be used for producing roof and road bitumen.

The distillate from the vacuum distillation is hydro purified at high temperature and pressure in the presence of a catalytic bed to remove impurities like Nitrogen, Sulphur, Chlorine and oxygenated organic components. The used catalyst is disposed off site.

The obtained products can be reused as motor, industrial and Hydraulic oils.

This technology is available under the name of MOHAWK and is one of the most advanced technologies with proven industrial applications.

1. Another technology by the name of REVIVOIL, again proven and widely used, is based on the principle of thermal De-asphalting and hydro-finishing.

The used spent oil is filtered and preheated, with mixing of additives for fouling reduction. The mixture is heated to 140⁰C and sent to a pre-flash column. Water and light hydro carbons are separated as a mixture at the top of the column. This mixture is then condensed to give water and light hydrocarbons. Water is sent to the treatment plant and the light hydrocarbons can be used as fuel or sold.

The dehydrated oil from the pre-flash unit as above, is heated to 350⁰C and fractionated in a Thermal Deasphalting unit under vacuum (15 TORR). Diesel is separated from the Top of the column and asphalt fraction is separated from the bottom. Oil is simultaneously fractionated into three different lubricant cuts with different viscosity grades. The cuts are stripped in stripping columns and cooled down. These oil cuts may be further finished by contact with hydrogen over a catalyst bed to remove metals, metal oils, organic acids, sulphur and nitrogen containing compounds.

The yield of base oil fractions has also been practiced to increase by subjecting the heavy asphaltic residue from the Thermal Deasphalting unit to Propane De-asphalting. This allows increase of base oil yield from 72% to 79% and propane can be stripped off and recycled.

The Central Pollution Control Board has published guidelines for the recycling of Hazardous waste. The guidelines prescribe the following Environmentally sound technologies for used oil.

1. Vacuum distillation with clay treatment
2. Vacuum distillation with hydrotreating
3. Thin film distillation

There are a number of other technologies in various stages of development and practice. They are generally known by the names of “Atomic vacuum distillation, Blowdec, Cyclon, Dunwell WFF, Garap, Interline, Relube, Meinker, Prop, Acid/clay purification/RTI/ Snamprogetti, Solulub and Vaxon”

The re-refining and reuse of used oil is a highly sustainable option and needs to be practiced. There is a huge gap which needs to be fitted.