Petroleum includes all liquid hydrocarbons (H-C) naturally found on earth. It also contains a small amount of sulfur (S), nitrogen (N), oxygen (O) and various minerals in its composition. In the commercial sense, “petroleum”; can be defined as liquid deposits characterized as crude oil (C2-C15); as gas accumulations called natural gas (<C4) and solid deposits called asphalt, wax or bitumen (C16-C60) according to its composition. There is asphalt, bitumen and wax as solids in crude oil. The petroleum refining industry has a history of more than 100 years and various modern processes have been developed over time for the refining of crude oil with the developing technology.
Base oil is obtained by refining a series of distillates obtained by vacuum distillation to remove unsaturated hydrocarbons by separating refused substances, such as paraffin, sulfur and nitrogen components in crude oil. Base oils are evaluated in two types, according to their source and method of production, as mineral (petroleum-based, natural) and synthetic oils. Base oils obtained from the refining of crude oil are mineral-based oils. Mineral-based oils contain various types of hydrocarbons with carbon numbers 14-40+ and, divided into three main groups as aliphatic, aromatic and mixed (aliphatic and aromatic) in terms of chemical structure.
Synthetic oils are developed in research laboratories. In the chemical sense, synthetic describes a compound that does not occur naturally and is obtained by one or more chemical reactions. Synthetic oils are petrochemical products which are obtained from natural gas, refinery gases, coal derivatives and shale extracts. Synthetic base oils can be grouped into six groups: polyalphaolefins (PAO), dibasic acid esters, polyol ethers, alkylated aromatics, polyalkylene glycols and phosphate esters. Viscosities of all but polyglycol fluids are in the viscosity ranges of slightly high viscosity index neutral mineral oils. Their viscosity indexes and flash points are higher. Pour points are significantly lower. These properties increase the value of synthetic base fluids in conditions requiring high and low temperature operation.
Additives and Treat Rates
Mineral, synthetic and biodegradable oils with high performance and advanced protection properties required by developing technologies are obtained by blending synthetic or mineral-based base oils with special additives and advanced techniques. Depending on the place of use and the desired performance, various additives are added to base oils in amounts up to 25%. The amount of additives in industrial oils is lower than in engine oils and their conditions of usage are more comfortable than engine oils.
Engine oils are oils with a much more advanced technology, containing a high percentage (20-25%) of additives, and having a high-performance consumer demand. Additives are components added to base oils to improve performance features such as regulating viscosity and reducing friction, preventing wear, forming film, cleaning etc. and to reduce undesirable effects such as oxidation, rust, corrosion, precipitation and similar in engines. Lubricants can be evaluated in 3 main groups: engine oils, industrial oils and oils used for special purposes.
Waste Oils
Waste oils are formed when the chemical structure of the base oil and the additives added to the base oil to give various properties to the lubricant change during use. It occurs as a result of the oil going out of its original use due to the contamination by different substances as well as wear and corrosion of metal equipment that oil comes into contact with, exposure to polluting chemicals caused by improper storage. Depending on usage conditions, there are harmful and even hazardous substances and pollutants in a waste oil.
Used engine oils may contain up to 1% sulfur, metals from additives and build up in the oil through wear, as well as some light hydrocarbons from fuel and partial cracking, and also water produced by the combustion of fuel. Because of the polymerization that will occur during the usage of the oil and the incomplete combustion of the fuel that used, pollutants with carcinogenic effects such as polyaromatic hydrocarbons (PAH), solvents as a result of chemical reactions and polychlorinated biphenyls (PCBs) are found in used oils. Chlorine used in lubricating oils is an important pollutant parameter, especially due to the possibility of dioxin/furan formation during combustion. Chlorine in waste oils is mainly caused by transformer oils, contamination with chlorinated solvents and additives added to lubricants. On the other hand, waste oil may contain contaminants such as antifreeze, brake fluid, dye, vegetable oils and solvents.
The amount of used waste oil depends on the lubricating oil consumption, the more oil is used, and the greater the amount of recyclable waste oil is released. The usage areas of oils are similar in all developed countries of the world. Almost 50% is used in industry and 50% is used in the transportation sector. Today, oil consumption reported as 40 million tons (+3%) which was 23.8 million tons worldwide in 1980.
Recycling of Waste Oil
In order to determine the amount of waste oil and obtain correct data, “MODEL” study was implemented on waste oils within the R&D project carried out by TUBITAK Marmara Research Center (MAM), since it is assumed that the data on the current amount of waste lubricants in Tükiye cannot be recorded accurately and regularly. In the lubricant flow diagram created for this study, stages of lubricant formation are shown starting from the base oil stage until waste oil generation and its disposal or recycling.
Within the scope of this study, which is the first kind in its field, lubricants are divided into two groups as “engine oils” and “industrial oils”. The field study (sampling) has been done, where engine oils are classified as road, air, marine and railway and other automotive oils, industrial oils are divided into hydraulic, gear, turbine, metalworking, heat treatment, greases and other industrial oils. The distribution of the consumed oil amounts according to the product types and the model results obtained from the recollectability studies were compared with the desk research data.
In the sampling studies, groupings were made using statistical methods and according to these methods the number of samples and sample distribution were determined. 3 main groups were created considering the transportation statistics of Turkish Statistical Institute (TURKSTAT) for land vehicles waste engine oil sampling studies. Sampling study was carried out from cars in the 1st group, from the buses in the 2nd group and from the tractors in the 3rd group. Sample cluster formation studies were carried out and appropriate amount of samples were taken by using these values obtained. The ratio of the oil that can be recycled was determined by proportioning the total crankcase volume of the sampled car and the amount of waste lubricant coming out of that vehicle.
Afterwards, the results were extended by linear regression method by using the ratio of each element in the sample cluster. The results show that the average waste lubricant rate that can be obtained from automobiles in Türkiye is 76%, while the rate from buses varies between 79-90% with the average rate in Türkiye as 83%. With similar methods, the rate of waste lubricant extracted from tractors did not show a big change in 10-year periods and was determined as 73-80% with the average rate found to be as 76%.
Recoverable Waste Oil Potential of Türkiye
Due to the number and diversity of producers, determining the amount of waste oil formation is quite difficult. It is quite appropriate to use waste generation factors for this type of waste generation. “%” sign is used worldwide as the reference unit for waste oils. “Material Flow Analysis (MFA)” used in factor determination studies has been adapted for waste oils, however its limits vary in terms of aim, scope, system definition, consistency and comparable data. Aim, scope and content differences and deficiencies in definition, methodology and terminology are the biggest problems in comparing factor studies.
As a result of samples measurements made in field studies and bilateral meetings, field results of % waste production factors (WPF) were obtained. Accordingly, it was concluded that approximately 50% of the consumed lubricants can be collected as waste and used in recycling processes (Table 1). With this study, it has been determined that 76-83% of engine oils in Türkiye are recoverable. According to the results obtained, the situation in Türkiye and the literature data showed similarities, in some cases results were obtained which are specific to Türkiye.
What to do about waste oils, disposal or re-refining of them is very important in terms of environmental protection, efficiency and economy. Waste oils (used oils) defined within the scope of hazardous waste, have a large usage potential contrary to the “waste” definition. This recovery potential of waste oils should be evaluated in accordance with the principles of oil reclaiming, recycling and energy recovery in the context of “Waste Management Hierarchy” specified in the Waste Directive (2008/EC, 19.11.2008) published by the European Union.
