Clean Technologies and Environmental Policy https://doi.org/10.1007/s10098-020-01893-0 ORIGINAL PAPER Recycling of used lubricating oil by solvent extraction: experimental results, Aspen Plus simulation and feasibility study Nancy Zgheib¹D. Hosni Takache¹ Received: 30 September 2019 / Accepted: 27 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020 Check for updates Abstract This study investigates the recycling of used lubricating oil (ULO) by solvent extraction using a ternary solvent consist- ing of 2-propanol, 1-butanol and methyl ethyl ketone (MEK) followed by a vacuum distillation unit. In order to select the best combination of solvents for the liquid–liquid extraction process, many parameters were first evaluated on a laboratory scale such as the effect of the solvent composition, the solvent-to-oil ratio and the temperature. The oil recovery efficiency and the physicochemical properties of the oil obtained from the extraction process were measured, and the results showed that a ternary system consisting of 50% 1-butanol/25% isopropanol/25% MEK is the best mixture for effectively reducing the contaminants in ULO with a good sludge separation prior to the fractionation. Also, a solvent-to-oil ratio of 3:1 and a temperature of 25 °C are the optimal parameters for the extraction when the aforementioned solvent mixture is used. The whole re-refining process including the vacuum distillation unit was then simulated for a plant capacity of 2125 kg/h using Aspen Plus™. Four pseudo-components (saturate, monoaromatic, diaromatic and polyaromatic) together with the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) were used to describe the liquid-liquid equilibrium (LLE) in the system solvent/lubricating oils during the extraction phase. The calculated yields on the extraction unit performed for different solvent composition, solvent-to-oil ratio and temperature showed a good agreement with the experimental data performed at the laboratory scale which verifies the right choice of the solvent mixture. The investiga- tion of the amount and composition of oil loss inside the sludge obtained from the simulation showed that the contaminant reduction and the oil recovery depend on the percentage of 1-butanol in the solvent mixture. Also, the results confirmed that the amount of MEK and 2-propanol in the solvent mixture should not exceed 25% and the best results were obtained when 1-butanol was used as a base solvent with an amount of 50%. Finally, to check the feasibility of the process, the investment payback time and the return on investment of the re-refining process were evaluated. Based on the economic study results, the production process was found to be highly profitable with a return on investment equal to 55% and a payout period of 1.9 years in the worst-case scenario where the price of lubricating oil is 2.5 $/L. ☑ Nancy Zgheib 1 nancyzgheib@usek.edu.lb Department of Chemical and Petroleum Engineering, School of Engineering, Holy Spirit University of Kaslik (USEK), Jounieh, Lebanon Published online: 14 July 2020 Springer Graphic abstract ULO Re-Refining of ULO Transport ✓ Experimental Study Dehydration ✓ Process Simulation ✓ Sensitivity Analysis Feasibility Study Solvent Extraction Solvent Recycling Fractionation N. Zgheib, H. Takache Recycled Lubricating oil . . . Keywords Recycling · Used lubricating oil · Solvent extraction Aspen plus simulation · Feasibility study Introduction Used motor oil is a hazardous material and harmful for the environment and for the human health because of the pres- ence of pollutants, for instance heavy metals, polychlo- rinated biphenyls and polycyclic aromatic hydrocarbons (Kanokkantapong et al. 2009). In the absence of an appro- priate treatment, used motor oil is normally discarded in the ground and into waterways including sewers making it an environmental hazard (Hamad et al. 2005). At the same time, ULOS are considered as valuable resources since the recycling of such materials will reduce the imports of oil products and will have a positive impact on the environ- ment as well (Totten and Bruce 2006). Numerous studies have reported the recycling of lube oil; however, there has been very little research reported on the re-refining of used lubricating oil (Boadu et al. 2019). ULO can be recycled and used as an alternative fuel in a variety of engine con- figurations and furnaces or as an important component in road paving asphalt. The most preferred option by experts in terms of energy requirements, cost and environment is the re-refining process (Jafari and Hassanpour 2015). Springer . Re-refining is a process that removes all contaminants for the purpose of reusing the base oil as lube oil. The conventional methods of contaminants removal that have been used on an industrial scale either require the use of toxic materials such as sulfuric acid or implies high cost technologies such as vacuum distillation. The acid pro- cess followed by clay treatment is the oldest one. This process is capable of producing high-quality base oil with the lowest cost but have the highest environmental risk. Membrane technology is another method for recycling the used motor oils where hollow fiber membranes such as polyethersulfone, polyvinylidene fluoride and polyacry- lonitrile are used (Cao et al. 2009). Solvent extraction has been employed as an alternate method to treat the used oil and the solvent chosen should have maximum solubility for the base oil and minimum for additives and impuri- ties. Vacuum distillation is also used to separate asphalts, additives and breakdown products from the base oil. This process operates at high temperature above 300 °C and proved to be impractical because of coking and fouling of processing equipment. The extraction process using liq- uid-liquid solvent performed prior to distillation of the Recycling of used lubricating oil by solvent extraction: experimental results, Aspen Plus... used lubricating oil is an alternative solution to the sepa- ration of asphalts and additives by vacuum distillation. Many studies have been conducted on the re-refining of used oil using solvent extraction (Whisman et al. 1978; Dos Reis and Jeronimo 1988; Alves dos Reis and Jeronimo 1990; Martins 1997; Elbashir et al. 2002; Hamad et al. 2005; Daham et al. 2017). Supercritical fluids propane and ethane are used as extracting solvents for recycling used motor oils but give low yield 72–80% (Rincón et al. 2003). According to Reis et al. (Dos Reis and Jeronimo 1988; Alves dos Reis and Jeronimo 1990), ketones and alcohols are the most effi- cient solvents for extraction since they are miscible with the base oil on the one hand and flocculate some of the additives and carbonaceous compounds by applying an antisolvent effect on the other hand. The capability to segregate sludge is closely related to the difference between the solubility of the solvent and the polyisobutylene, a viscosity improver additive. Whisman et al. (1978) showed that a ternary sys- tem consisting of 25% 2-propanol, 25% butanone and 50% 1-butanol is reasonably effective to reduce contaminants in the oil with a good sludge separation. They indicated that 2-propanol rich systems produce high ash reduction but poorly separated sludge, while butanone-rich systems lead to a good sludge separation, but re-dissolve the contaminants. To adjust the ash reduction and oil recovery properties, an equal percentage of 2-propanol and butanone was employed and 1-butanol was chosen as a base solvent. Few studies have reported the simulation of an extraction process using vacuum distillates as main feed (Coto et al. 2006a, b; Espada et al. 2008), and only one study (Botas et al. 2017) has reported the simulation and design of the re-refining process of ULO using propane as a solvent for the extraction process. In fact, the simulation of the extrac- tion process of such systems is complex due to the huge number of components present in the lubricating oil. To be able to properly reproduce the equilibrium properties dur- ing the extraction operation, an appropriate thermodynamic model must be used. Also, the number, the composition and the properties of each component that are taken into con- sideration to describe the system should be well defined. The approach usually used to describe the components pre- sent in petroleum product is based on distillation curves. This method is not suitable for extraction processes since the chemical structure of the oil and the solvents used has a much bigger effect than the boiling temperatures. In order to estimate the LLE of the systems furfural/lubricating, Coto et al. (2006a, b) used a model based on a correlation of pseudo-component properties (specific gravity, density, refractive index and sulfur content) and NRTL parameters with the oil average boiling temperature. This method has proved to be highly effective for any lubricating oil cut and needs only the average boiling point and three physical prop- erties as experimental data. In this study, three mixtures of composite solvents con- taining 2-propanol, 1-butanol and MEK were first investi- gated on a laboratory scale to treat the used oil. The choice of the solvent and the ratio of the ternary system were based on a literature investigation (Whisman et al. 1978; Dos Reis and Jeronimo 1988; Alves dos Reis and Jeronimo 1990). The objective of this investigation is to select the best combina- tion of solvents as well as the optimal operating conditions for the extraction unit. In fact, solvent selection is critical for the development of an economical extraction system and the optimal solvent selection is based on laboratory effort before starting the design or the selection of the extraction unit. For this purpose, the effect of the solvent type and composi- tion, the solvent-to-oil ratio and the temperature on the oil recovery efficiency and the physicochemical properties of the oil obtained from the extraction process will be studied. Then, the whole re-refining process will be simulated with Aspen plus™, and the yields of the extraction unit obtained by varying the solvent type and composition as well as the solvent-to-oil ratio and the temperature will be compared to the experimental results. The detailed composition of the oil in the sludge obtained from the simulation will be inves- tigated in order to study the effect of the solvent type and concentration on the contaminant reduction and the oil loss. Finally, a profit and loss analysis of the recycling process will be performed to explore if the application of the process at industrial scale could be recommended. Experimental section Materials Virgin lubricating oil was purchased from the local mar- ket. The used lubricating oil samples were collected from Mercedes-Benz lube change center in Lebanon. The sam- ple used in this study is a mixture of used oil coming from automobiles operating with different engine conditions. The sample was stored in a suitable tank away from light and at room temperature. Solvents used for extraction were 2-pro- panol, 1-butanol and MEK. The solvents purchased from Sigma-Aldrich were of analytical grade with 99.5% purity. Solvent extraction process The oil was first filtered and then dehydrated using a rotary evaporator. This operation was carried out to remove water and some light hydrocarbons. The dehydrated used oil was collected and then used for the next step of solvent extrac- tion. Three different compositions of a ternary system con- taining 2-propanol, 1-butanol and MEK were used in this study, and the composition of the three mixtures is reported in Table 1. Springer N. Zgheib, H. Takache Table 1 Composition (vol%) of the solvent mixtures used in the extraction process Mixture composition 2-propanol 1-butanol (%) MEK (%) (%) Mixture A 25 50 Mixture B 25 40 Mixture C 40 35 25 535 25 5355 The used oil was weighed (mo) and mixed for 20 min with the composite solvent mixture using an electrical stirrer at 500 rpm. The solvent-to-oil ratios employed in this study were 2:1, 3:1 and 4:1, and the extraction temperatures used were 25, 40 and 60 °C. The mixture was then left unshaken for a period of 24 h to allow extraction-flocculation. Then, solvent-oil solution was separated from the sludge by decan- tation and the solvent mixture was recovered. This proce- dure was repeated in all experiments for three times. The oil recovered was weighed (mp), and the percentage of lubricat- ing oil extracted was calculated using Eq. (1). %R = 100 × mp то (1) where % R is the percentage of lubricating oil extracted, то is the mass of the ULO, and mp is the mass of the oil obtained after the separation of the solvent in the extract. Analysis of samples The ULO was tested for ASTM D-1160 method. The recy- cled oil obtained from the extraction was analyzed for differ- ent physical properties such as: Flash points by ASTM D56, pour point by ASTM D97-02, viscosity index by ASTM D445-18, density (specific gravity) by ASTM 1298, ash con- tent by ASTM 482-13 and sulfur content by ASTM D4294. Kinematic viscosity The kinematic viscosity is the measure of the resistive flow of a fluid under the influence of gravity. A fixed volume of oil was charged into the capillary of a calibrated viscometer which has a flow time above 200 s. The diameter of the capillary was chosen by considering the expected viscosity. The viscometer was placed into a constant temperature bath maintained at the temperature on which the viscosity is to be determined. A chronometer was used to determine the time the oil takes to progress between two points highlighted inside the capillary. The viscosity is determined by multiply- ing the efflux time by the viscometer constant. Pour point The pour point of petroleum products is the lowest temper- ature at which the oil will flow under cooling prescribed conditions of test. A specific amount of oil was placed in a test jar which is closed with a cork engulfing a thermom- eter. The oil was heated in a bath at 48 °C, then cooled at intervals of 3 °C and tilted to determine the flow charac- teristics. The pour point is reached when the fuel no longer moves upon holding the specimen horizontally for 5 s. Flash point The flash point is the lowest temperature at which vapors of the material will ignite under the application of an igni- tion source. The test cup was filled with oil to the required volume, and both the test cup and the specimen were main- tained at a temperature that is at least 23 ±5 °C below the flash point expected. The temperature of the specimen was increased, and the ignition source is applied to the vapor area in the cup. The sample is considered to have reached the flash point when a large flame occurs and instantane- ously propagates over the whole surface of the specimen. Ash content This method consists of measuring the amount of ash- forming material in the oil which provides an idea about the quality of the product and the adequacy for any application since the ash represents the impurities and unwanted components. The sample was placed in a suit- able vessel and was burned until only ash was left behind. The evaporating crucible was heated at 775 °C, cooled to room temperature and weighed. The mass of the ash was then calculated as a percentage of the original sample. Sulfur content This test measures the sulfur content in petroleum prod- ucts. The sample was placed in the beam emitted from an X-ray source, and the resulting fluorescent X-rays were measured and the sulfur concentration in mass% was deter- mined by comparing the accumulated count with counts from previously prepared calibration samples. Vacuum distillation of used lubricating oil ASTMD 1160-13 standard method was used to determine at reduced pressures the range of boiling points for used motor oil. The sample of ULO was vacuum distilled at Springer Recycling of used lubricating oil by solvent extraction: experimental results, Aspen Plus... about 65 mm mercury and over a temperature range of 272-400 °C. Experimental results Oil recovery is an important parameter to be considered, and it represents the economy of the process since it accounts for the oil yield obtained from the extraction process. The ash reduction is also a vital parameter in the extraction process since it accounts for the reduction of the concentration of the contaminants in the oil such as dirt, iron oxide, wear metals and corrosion products as well as the concentration of ash- producing additives. The sulfur reduction also accounts for the removal of sulfur compounds and additives. The recov- ered oil obtained from the extraction experiments performed with mixtures A, B and C using a solvent-to-oil ratio of 3:1 was tested for oil recovery, ash reduction % by means of ASTM 482-13 and sulfur reduction % by means of ASTM D4294. The results obtained for different compositions of the ternary solvents used are shown in Table 2. As it is shown in Table 2, the optimum solvent mixture that produces maximum oil recovery (96%) with maximum ash reduction (28%) and an acceptable sulfur reduction (16.7%) was achieved with solvent mixture B. These results indicate that mixture B is capable of reducing contaminants in the oil with a good contaminant separation. The high per- cent oil recovery obtained for mixture B is in good agree- ment with Whisman et al. (1978) who reported that using higher percentage of MEK than 25% produces good sludge separation and thus high oil recovery since MEK has a lower solubility parameters value than the two alcohols. However, increasing the amount of 2-propanol does not decrease the ash forming material as reported in the literature. This differ- ence might be associated with the nature of the base oil and to the fact that these days ash-less materials are used in the additive package instead of ash forming materials. The solvent-to-oil ratio investigation was conducted on mixture B. The investigated solvent-to-oil ratios were 2:1; 3:1 and 4:1, and the extraction temperature used was 25 °C. The oil recovery results in relation to solvent-to-oil ratio are shown in Fig. 1. It can be seen that the best condition after which a further increase in the solvent oil ratio bring no Table 2 Oil recovery %, ash reduction % and sulfur reduction % val- ues obtained from the solvent composition experiments performed at the laboratory scale Oil recovery (%) 100 90 80 70 60 50 40 30 20 10 0 2 3 Solvent to oil ratio 4 Fig. 1 Percentage of oil recovery for optimum solvent-to-oil ratio experiments performed on mixture B using an extraction temperature of 25 °C change in the percent oil recovery values is above a solvent- to-oil ratio equal to 3:1. This can be attributed to the fact that increasing the solvent-to-oil ratio improves the solubility of the oil in the solvent resulting in decreasing the oil loss in the sludge and increasing the oil recovery values. Solvent- to-oil ratios higher than 3:1 are not considered economically feasible by industry, and the experimental results showed no improvement in terms of oil recovery. Thus, a solvent-to-oil ratio of 3:1 will be considered to be the optimum ratio in this work. To study the effect of the temperature on the extraction- flocculation process, the extraction was performed on mix- ture B at three different temperatures (25, 40 and 60 °C) using a solvent-to-oil ratio of 3:1. The oil recovery results in relation to the extraction temperature are shown in Fig. 2. No significant change in percent oil loss was shown with increasing the extraction temperature. Thus, the extraction process at a temperature higher than 25 °C does not lead to a higher yield of oil recovery. Oil recovery (%) 100 90 80 70 60 50 40 30 20 Mixtures Oil recovery (%) Ash reduction Sulfur 10 (%) reduction 0 (%) 25 40 60 Temperature (°C) Mixture A 90 27 20 Mixture B 96 28 16.7 Mixture C 84 20 14.3 Fig. 2 Percentage of oil recovery for optimum extraction temperature experiments performed on mixture B using a solvent/feed ratio of 3:1 Springer

Solved: Clean Technologies and Environmental Policy https://doi.org/10.1007/s

Home
questions and answers
clean technologies and environmental policy https doi org 10 1007 s100

Question

Clean Technologies and Environmental Policy https://doi.org/10.1007/s10098-020-01893-0 ORIGINAL PAPER Recycling of used lubricating oil by solvent extraction: experimental results, Aspen Plus simulation and feasibility study Nancy Zgheib¹D. Hosni Takache¹ Received: 30 September 2019 / Accepted: 27 June 2020 © Springer