Process for Refining of Used Lubricating Oil

 Dehydration

Used oil from tankers and drums is unloaded in used oil unloading pit fitted with course filtration screen to remove large suspended matter. The used oil is then pumped to either of the used oil storage tanks by used oil pit pump.

The used oil from either of these tanks is then pumped by dehydrator feed pump to dehydrator via fine duplex filter. The oil in the dehydrator is circulated by dehydrator circulation pump through dehydrator circulation heater which provides heat required for dehydration. Hot oil from the hot oil unit is circulated to dehydrator circulation heater for heating the circulating oil.

A part of the dehydrated oil from dehydrator circulation pump passes through dehydrated oil cooler where it gets cooled before going to dehydrated oil storage tank . The dehydrated oil from dehydrated storage tank is sent to total evaporation and fractional condensation section.

The water vapors along with some vaporized gas oil from dehydrator is condensed by dehydrator condenser. The condensate passes to oil separator. The separated gas oil is used as fuel in the hot oil unit and water is drained. This water can be reused as raw water.

Total Vaporization & Fractional Condensation

The dehydrated oil along with additive is pumped at a controlled rate to the vaporizer by feed pump. The oil vaporizes during its passage through vaporizer. The heating is accomplished by burning gas oil in the vaporizer, which is generated in the plant. The heating is done by convection alone by re-circulating flue gases over the tubes by flue gas circulation blower in the convection section of the vaporizer.

The vaporized oil along with bitumen, carbon and other non vaporizing matter enters the separator where the vapors disengage from the non vaporized bituminous type residue material which is directly pumped into barrels by bitumen pump to be disposed of for blending with bitumen. The level in the separator is controlled.

The vapors from the separator enter the direct contact heavy base oil condenser, where the vapors partially condense and the temperature of condensation is controlled by refluxing the condensed heavy base oil. The viscosity of the condensed heavy base oil is thus controlled.

The heat of condensation in the heavy base oil condenser is utilized to generate steam in the steam drum by circulating hot water through heavy base oil circulation cooler by hot water circulation pump. The steam generated is used in booster ejector.

Part of the condensed heavy base oil is pumped through a level controller to the heavy base oil cooler as recovered heavy base oil. Cooling water is used in heavy

base oil cooler.

The non-condensable along with uncondensed oil vapors enter light base oil condenser. The temperature and level control on this condenser is similar to that of heavy base oil condenser, except that the condensing temperature is set at a lower value to allow the condensation of light base oil. The viscosity of the light base oil is thus controlled. The heat of condensation of light base oil is utilized to preheat feed through light base oil circulation cooler.

Part of the condensed light base oil is pumped through a level controller to the light base oil cooler as recovered light base oil. Cooling water is used in light base oil cooler. The non-condensable along with remaining oil vapors enter gas oil condenser. The temperature and level control on this condenser is similar to that of light base oil condenser except that the condensing temperature is set at a lower value to allow the condensation of maximum gas oil and allow only non-condensable to go to vacuum system.

Part of the condensed gas oil is pumped through a level controller on the gas oil circulation cooler as recovered gas oil. Cooling water is used in gas oil circulation cooler.

The entire operation is carried out under vacuum which is maintained by a combination of booster ejector, inter cooler and a two stage vacuum pump in the system. Steam required for booster ejector, is produced in the plant itself.

Bleaching & Filtration

The recovered base oil is transferred into base oil bleaching vessels batch wise from recovered base oil tank by base oil transfer pump The temperature is raised to about 1000C to 1200C and calculated amount of bleaching earth is added to the bleaching vessel under constant agitation and circulation by base oil circulation/ filtration pump .

The bleaching earth reacts to remove the color. While bleaching is going on in one of the vessels the other is feeding the base oil and bleaching earth slurry to base oil filter press through its circulation/ filtration pump. The clear filtered and bleached oil is collected in bleached base oil tanks, While one filter press is in operation the other is under cleaning.

Also the recovered spindle oil is transferred into spindle oil bleaching vessels batch wise from recovered spindle oil tank by spindle oil transfer pump. The temperature is raised to about 1000C to 1200C and calculated amount of bleaching earth is added to the bleaching vessel under constant agitation and circulation by spindle oil circulation/ filtration pump. The bleaching earth reacts to remove the color.

After bleaching the spindle oil and bleaching earth slurry is fed to spindle oil filter press through its circulation/ filtration pump. The clear filtered and bleached oil is collected in bleached spindle oil tank. The filter press is in operation for 16 hrs. a day is idle for 8 hrs for cleaning.

Typical Recovery of Process

PRODUCTTYPICAL FEED COMPOSITION

%WT.

RECOVERY RATE %

WT.

YIELD%

PRODUCTION KGS/HR.

PRODUCTION TPA

DRIED USED OIL

100.0 - - - - 2000.0 15000

HEAVY LUBE BASE OIL

79.0 72.0 91.0 1440.0 10800

LIGHT LUBE BASE OIL

12.8 12.6 98.5 252.0 1890

GAS OIL /LIGHT ENDS

5.4 5.2 96.3 104.0 780

ASPHALT 2.8 10.0 - - 200.0 1500

LOSSES - - 0.2 - - 4.0 30

Other used oil Recycling / reprocessing  technologies

Acid - Clay Process            

Acid Activated Clay Process.

Vacuum Distillation   a) Thin/Wiped Film Evaporator.    b) Pipe Furnace VaporizerSolvent Extraction Process

 Acid - Clay Process

Features:» Acid-Clay Process for used oil recycling/reprocessing is Old and popular. This is a      Proven technology worked for many years worldwide. Can be     set-up for  very small capacity. » Low Capital investment. Makes it most cost effective for small and tiny scale plants. » Non sophisticated, Very simple process. Simple to operate, No advanced instruments, No skilled operators required.

Drawbacks:» Causes Environmental pollution due to generation of acid sludge and acid gas emission. Disposal of acid sludge is a problem.» Causes corrosion of equipment’s reducing its life.» Gives Lower yield. Due to loss of oil in sludge as well as clay since higher dosage of clay is required.» As most of the government has adopted stringent pollution control regulations, this process is on its  way out.

 Acid Activated Clay Process :-

Features» No acid is required. » It is simple process

» Suitable for small capacity plant.

Drawbacks:» Very high clay consumption, low yield, inconsistent quality. » Disposal of large quantity of spent clay is a environmental problem.» Suitable only for very small capacity plants. » Process is dependent on a particular type of clay which may not be available from all the sources.

 Vacuum Distillation

Thin/Wiped Film Evaporator

Features:» Suitable for high capacity plants. » Thin film evaporator is capable of Operating at high vacuum and normally used for high value and heat     sensitive products. » Does not cause pollution.» Sophisticated Equipments & Process » Produces good quality Base Oils.

Drawbacks:» Operates at high temperature & very high Vacuum. Require special /expensive thermic    fluids & heating     system. High cost of heating fluid and High operational costs.» Requires high capital investment.» Plant has to be of a higher capacity to make it economically viable.» Require highly skilled & Operational maintenance Staff. As it has very sophisticated equipment. » Higher Fuel Cost. » Due to multiple stage of distillation involving heating & cooling.

Pipe Furnace Vaporizer

Features:» Simple pipe furnace, convection heating at low heat flux by re-circulating flue gases. » No moving part on process side. » No prior removal of gas oil is required. » Simple instrumentation.

Solvent Extraction Process

Features:

» In this process propane is used as solvent to remove bitumen, additives, metals and tar etc. » Solvent is recyclable. » Does not cause pollution. » Produce Good quality Base Oils.

Drawbacks:» Has to operate at higher pressure ( 10 atm. ) at ambient temperature ( 27oC ) require high pressure sealing systems. (making system expensive and complicated) » Involves operational solvent losses and highly skilled operating and maintenance    personnel and system is required. » Economical only for high capacity plants. » Propane being very hazardous, Fire & explosion hazard is associated with this process.

Almost all types of waste oil have the potential to be recycled safely, saving a precious non-renewable source and at the same time minimizing environmental pollution but most of used oil is handled improperly. The results are some are emptied in to sewers for going directly into water waste, adversely affecting water treatment plants, some are dumped directly on to the ground to kill weeds or is poured on to dirty roads or is dumped in deserts, where it can contaminate surface and ground water.

Lubricating oil is an important resource and a petroleum base product. The high price of oil and objective of saving valuable foreign exchange has resulted in efforts for regeneration of used lube oil. Regeneration of used lubricating oils is based on the fact that, “Petroleum lubricating oil are almost durable”.

Lubricating oils are impaired temporarily only because of accumulation during use or handling of contaminants coming from extraneous impurities and products of oil deterioration, which can be separated from the used oil by re-refining or re-conditioning. The treated oil, then, becomes almost equivalent to fresh or virgin oil.

In India, re-recycling waste oil industry is mainly an un-organized but some public service units (PSU) do re-recycling but most of the market demand is furnished by the small scale industrial units (SSI’s) but due to the use of Acid Clay Process they have been shut down or can refurnish till they adopt new certified process.

Environmentally Sound Technologies (EST)Re-refiners and re-cyclers now have to use only environmentally sound technologies (EST) while re-cycling and refining waste oil. In case of oil re-refiners using acid clay process or modified acid clay process have been advised to switch over to Environmentally Sound Technologies only or close down.

The following processes have been approved as Environmentally Sound Processes,1. Vacuum distillation with clay treatment. (We use this treatment) 2. Thin Film evaporation process.3. Vacuum distillation with hydro treating.