Analysis of Waste Lubrication Regeneration Process by Solvent Refining MethodFason
Waste lubricating oil regeneration process
Over the years, both developed and developing countries have accumulated rich experience in waste oil recycling. At present, the main processes for recycling waste oil into applicable base oils are: 1. acid white clay process; 2. vacuum distillation-solvent Refining process; 3. solvent extraction-flocculation process; 4. molecular distillation process; 5. hydrogenation process; 6. membrane separation process.
According to the difference between waste oil treatment processes at home and abroad, the regeneration process of waste lubricating oil can be classified into three categories.
The first type is an acid-based process, mainly acid white clay. It is based on the Meinken process. Although it can remove most of the impurities such as naphthenes, basic nitrides and colloids, the process produces a large amount of acid gases. Acid slag and white earth slag cause environmental pollution, equipment corrosion, and endanger human health. The process has now been phased out.
The second type is an acid-free process, including solvent refining, solvent extraction-flocculation, thin film evaporation, molecular distillation, and membrane separation processes.
The thin film evaporation process has the advantages of large heat transfer coefficient, high vacuum and simple purification conditions, but the yield is low, and the basic indexes such as acid value and color cannot meet the requirements of the standard base oil.
Membrane separation technology uses a selectively permeable membrane to separate lubricating oil and impurities under the influence of external forces such as concentration difference, pressure difference, and potential difference. However, because the waste lubricating oil has a large viscosity, a large amount of impurities, and a complicated composition, the requirements for the membrane material are harsh and industrialization is difficult.
Molecular distillation technology, also known as short-path distillation, is a new separation technique that uses a mean free path difference of various materials to separate materials under high vacuum conditions. However, there are limitations in molecular distillation; there are some technical problems in the provision of vacuum equipment and heat transfer materials; the high vacuum design makes the technology have high design requirements and equipment investment.
The third type is a hydrogenation process, including a thin film evaporation-hydrogenation process, a solvent extraction-hydrogenation process, and the like.
Since the additive in the waste lubricating oil contains a phosphorus compound and a heavy metal compound, the pretreatment cannot be completely removed, and deposition on the surface of the catalyst during hydrogenation causes poisoning, and industrialization is difficult to carry out.
Solvent-based waste oil regeneration is the use of organic solvents for the difference in solubility of base oil components in waste oil with additives, oxidation products, sludge and other impurities, separating impurities, obtaining reclaimed oil, low energy consumption and less pollution.
The early research direction mainly focused on the weight percentage of asphaltene colloids after refining. As the quality of oil demand increased, the indicators of refined base oil became the focus of attention. Solvent-based waste oil regeneration is one of the cheapest and most effective methods in the current waste lubricant regeneration process.
Vacuum distillation-solvent refining process
The process utilizes the difference of the boiling points of different distillates when the waste lubricating oil is distilled, and the fraction is cut by vacuum distillation, and the obtained distillate oil is refined by solvent to remove non-ideal components such as colloid and acid oxide to reach the standard of the base oil. The solvent in the extract is recovered and reused. Commonly used solvents such as furfural, N-methylpyrrolidone (NMP), and the like.
1. Compound solvent technology based on furfural solvent
As a traditional and mature solvent refining technology, furfural refining technology has been widely used in the field of waste oil recycling. Solvent furfural has good adaptability to oil products, low price and easy availability of raw materials. The disadvantage of furfural refining is that the solubility of furfural solvent is small, the ratio of solvent to oil is large, and the energy consumption of solvent recovery is increased. Furfural is easily cracked and condensed at temperatures above 230 ° C, and its thermal stability is poor. Therefore, the use of light hydrocarbons and furfural solvent can not only increase the selectivity of the solvent, but also reduce the production energy consumption, thereby improving the entire waste lubricating oil regeneration process.
The Songjing experimental group of Daqing Petrochemical Company compared the conditions of the epichlorohydrin-furfural complex solvent and the furfural single solvent to the lubricating oil fraction. The complex solvent of furfural and epichlorohydrin in a volume ratio of 1:1 was low. The viscosity index of the reclaimed oil refined at a single solvent purification temperature of 25 ° C was increased by 4 to 6, and the yield was increased by 1% to 3%.
Baoding Petroleum Branch Yang Shuhua and so on compared the purification process of furfural single solvent and the use of furfural-monic alcohol compound solvent to refine waste oil. The color, yield and viscosity-temperature performance of oil refined by compound solvent are higher than single furfural solvent.
Professor Guo Daguang from Liaoning University of Petroleum and Chemical Technology used solvent treatment of waste lubricating oil with furfural and different compounding solvents. The solvent includes N,N-dimethylformamide (DMF), n-butanol, isopropanol and the like. For example, the ratio of furfural to DMF is 0. 5%。 The yield of the product was 88.5%. The yield of the product was 88.5%. 5%。 The total yield of the oil is 72. 5%. The total yield of the oil is 72. 5%. The molar ratio of the oil is 1. 5:1, the total yield of the oil is 72. 5%.
In addition, by using the surfactant sodium dodecylbenzenesulfonate or a polyether as a co-solvent, the formation of a water-in-oil molecular film due to an emulsifier in the waste lubricating oil can be prevented, thereby improving the yield of the refined oil. The results showed that the reaction temperature and the ratio of the agent to oil were better than those of the furfural single solvent. The selected compound solvent has the following characteristics: 1. The boiling point and heat capacity of the solvent are lower than that of furfural, which can reduce the recovery temperature of the solvent and reduce the energy consumption; 2 the density of the solvent is less than the phase separation and reverse flow of the furfural in the purification process of furfural; The solvent has a strong selective solubility for non-ideal components of the lubricating oil and lowers the refining temperature.
2. Compound solvent technology based on N-methylpyrrolidone (NMP) solvent
NMP refining technology plays an important role in the field of waste oil recycling. NMP has good selectivity and solubility for unsaturated hydrocarbons, aromatic hydrocarbons and sulfides. It has good chemical stability and thermal stability relative to furfural and phenol, and has low volatility and low toxicity. However, due to its corrosive solvent recovery equipment, it is expensive, and the disadvantages of large energy consumption and long time required for distillation and refining process limit its use.
In order to improve the selectivity of NMP solvent refining, NMP and related auxiliary agents are usually used to form a compounding solvent. The main additives added are: water and ethanolamine. Jelena Lukic et al. refined the waste oil with NMP and water as a co-solvent. The results showed that the determination of the process parameters and the chemical composition of the refined oil affected the electrical properties and oxidation properties of the re-refined oil. The optimum process parameters are a mild extraction temperature, 1% water and a ratio of NMP to low solvent to oil of 0.5.
Li Zhidong studied the effect of the addition of an auxiliary ethanolamine on the refining effect of waste oil in NMP. It was found that NMP plays an important role in improving the quality of waste oil and removing organic acids from waste oil.
Solvent extraction-flocculation process
Since the hydrocarbons in the waste lubricating oil are different from the polar oxides, additives, and colloidal asphaltenes, the solvent is dissolved to remove the ideal components, and the refined oil is re-refined or the pre-preparation process is provided for the re-refining stage. .
Since the heteroatom compound in the waste oil and the asphaltene colloid are dispersed in a highly dispersed colloidal state by electrostatic interaction, it is necessary to select not only a suitable solvent as an extractant but also a flocculant to break the stability of the impurity particles. Promotes better flocculation.
The choice of extractant is based on the Hildebrand solubility theory of the solvent. It should have two characteristics: 1 it can be miscible with the base oil contained in the waste oil; 2 can selectively dissolve impurities. In addition, the impurity particles usually have a high molecular weight, and the solubility of the heavy solvent is close to the solubility parameter of the impurity particles, and the solubility is better. The low molecular weight solvent suppresses the dissolution of the impurity particles. Low molecular liquid hydrocarbons act as extractants to not only dissolve the base oil fraction, but also dissolve macromolecules and other additives.
Solvent triols have low solubility in base oils, and pentacarbons have good solubility not only for base oils but also for impurities. Tetracarbon alcohols are often used as effective extraction solvents. A ketone solvent of less than four carbon atoms, such as acetone, is almost immiscible with the base oil at room temperature. The ketone of five carbon atoms has good solubility for base oils and impurities. Furthermore, whether the polarity of the solvent and the polarity of the naphthenes in the lubricating oil are similar is also a factor in solvent selection.
The dispersant in the waste oil can stabilize the presence of the impurity particles, and the extractant can avoid the formation of a stable dispersion system by compounding with the flocculant. Alves dos Reis proposes that when the flocculation occurs, some polymer compounds and the impurity particles co-flocculate. When the difference in solubility between the flocculant and the polymer compound is large, the yield is the highest, and co-extraction of impurities such as polyisobutylene which is generally used as a viscosity index improver in a lubricating oil is avoided. The substances having flocculation are: monoethanolamine, divinylamide, polyacrylamide, and substances having a specific amide group.
M Alves dos Reis et al. used flocculation regeneration experiments of waste oil with n-butanol and methyl ethyl ketone as extractants, respectively. It was found that the alcohol polar solvent of four carbon atoms can not only extract the base oil in the waste oil, but also flocculate some of the additives and oxidation products. At the same time, the effect of methyl ethyl ketone extraction waste oil was also explored. The experimental results show that n-butanol is better than butanone in removing waste oil precipitates, which is increased by more than 20%.
The BERC process developed by the US Energy Center uses an alcohol-ketone mixed organic solvent (n-butanol: isopropanol: methyl ethyl ketone = 2:1:1) and a waste lubricating oil ratio of about 3:1 to extract and centrifuge the waste lubricating oil. After the white earth is replenished, the lubricating base oil can be obtained.
Li Ruili used butanone and isopropanol to prepare a solvent with a mass ratio of 3:1. After adsorption and purification by white clay, the regenerated oil reached the HIV400 base oil standard and the yield was 96%. Saeed M Al-Zahrani and others used a variety of solvents (n-butanol, propanol, fluorotrichloromethane, trifluorotrichloroethane, methyl ethyl ketone, etc.) to regenerate the waste oil by solvent extraction-white soil adsorption process. The optimum agent-to-oil ratio can be used to reflect the extraction capacity of the base oil by the Hildebrand and Peng-Robinson formulas associated with the dissolution parameters.
Reis et al. studied the regeneration of waste oil by using n-hexane and KOH containing isopropanol as a compound solvent (waste oil: n-hexane:isopropanol = 0.25:0.2:0.55, 3 g/L of isopropanol solution), and the results showed Industrial applications are very effective and can effectively remove sludge from waste oil.
The Ancaelena-Eliza STERPU group uses an alcohol-ketone mixed solvent (isopropyl alcohol: n-butanol: butanone = 1:2:1). The ratio of the oil is 4:1. The color, odor and solubility of the oil are all available. improve. Yang Xin, Department of Military Oil Application and Management Engineering, Logistics Engineering College, used four carbon alcohol polar solvent as extractant and polyacrylamide as flocculant to carry out waste lubricating oil regeneration experiment. When the extraction solvent was isobutanol, the purification time was 15 min, and the refining temperature was used. Under the condition of 25 ° C (room temperature), mass ratio of agent oil 5, and dosage of flocculant 1.0%, the yield of regenerated oil of the process is 82.1%, the viscosity temperature index is above 130, the lightning exceeds 200 ° C, and the acid value is 0.01 mg KOH. /g, the residual carbon is reduced to less than 0.01%.
Waste oil regeneration has made positive contributions to environmental protection and resource reuse. With the increasingly strict environmental protection requirements and the continuous advancement of waste oil regeneration technology research, the traditional acid clay regeneration process has been gradually eliminated, replaced by molecular distillation, super Critical extraction, membrane separation, and hydrofinishing technologies are receiving increasing attention, and it is difficult to systematically industrialize due to technical and financial problems.
The solvent regeneration of waste oil technology is easy to scale industrialization due to its simple process, low energy consumption and low pollution. The development direction of solvent-based waste oil regeneration is: 1 to improve the solubility of solvent or compound solvent to non-ideal components, reduce the ratio of solvent to oil, easy to recycle solvent, environmentally friendly and non-toxic; 2 as a pretreatment technology for hydrofining. In order to realize the industrialization and scale development of waste oil regeneration. Provide sustainable development theories and processes for small and medium-sized waste oil recycling companies.