DEVELOPMENT OF A METHOD FOR THE ENVIRONMENTALLY FRIENDLY TREATING OF OIL SLUDGE WASTE WITH A MIXTURE OF Fe2(SO4)3 И Al2(SO4)3 SOLUTIONS

ABSTRACT

To address the environmental issue caused by pollution from oil sludge, which contains various inorganic and organic toxicants during storage in landfills and transportation, and processing, we conducted a study on the environmentally effective purification of oil sludge samples collected at the Heydar Aliyev Oil Refinery. The study used a mixture of 5% solutions of Fe2(SO4)3 and Al2(SO4)3 salts in a 1:1 ratio to purify the oil sludge. Based on the results, it was possible to achieve a purification rate of up to 99,98%, which is significant for economic and environmental reasons in the oil refining industry.

АННОТАЦИЯ

Чтобы решить экологическую проблему, вызванную загрязнением нефтешламом, который содержит различные неорганические и органические токсиканты при хранении на свалках, транспортировке и переработке, мы провели исследование по экологически эффективной очистке образцов нефтешлама, собранных на нефтеперерабатывающем заводе имени Гейдара Алиева. В ходе исследования для очистки нефтешлама использовали смесь 5%-ных растворов солей Fe2(SO4)3 и Al2(SO4)3 в соотношении 1:1. Основываясь на полученных результатах, удалось достичь степени очистки до 99,98%, что важно по экономическим и экологическим соображениям в нефтеперерабатывающей промышленности.

Keywords: oil sludge, ecological, effective, coagulant, economic, ecotoxicant.

Ключевые слова: нефтешлам, экологический, эффективный, коагулянт, экономический, экотоксикант.

Introduction

The OSM (oil sludge mixture) formed during various technological processes of the oil refining industry (ORI) is very different from the oil sludge formed in the oil production industry due to its complex composition and properties. That is why, as noted in the literature [1-11, 15], despite the separation of OSM  from OPM (oil products mixture) in the ORI through various methods and stages, deep purification of this waste (up to ~100%) has not been fully achieved with a maximum removal rate of only 75-85%.

In this case, there ares significant financial costs associated with the use of large amounts of energy. Additionally, environmental pollution occurs during the various stages of cleaning, transporting, storing, processing, and disposing of oil sludge produced in the oil refining and production industries.

Despite the fact that OSM has been purified from OPM to approximately 80-90% using known methods such as with a modern Alfa-Laval unit, there are still some volatile inorganic and organic compounds in the purified OSM that have ecotoxic properties. These compounds directly contribute to the pollution of water, soil, and the atmosphere. Over time, they have a negative impact on the environment and all parts of the biosphere.

As is known, in scientific research, the results of studies on a particular topic are often reviewed. Based on our studies related to our research, we have found that the issue of completely removing OPM from OSM has not been solved. To address this, a study was conducted to investigate environmentally friendly methods for purifying OSM samples collected from the Heydar Aliyev Refinery using a mixture of 5% solutions of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts in a 1:1 ratio.

The concentrations of volatile eco-toxicants in OSM collected at the inlet of the Alfa-Laval unit operated by Ekol Engineering Services CJSC for the purification of OSM from OPM at the Heydar Aliyev Refinery were also determined using the Drager device in air. During the measurements, several eco-toxicant compounds were found to be emitted from OSM into the atmosphere: C_xH_y, PAHs, H₂S, SO₂, PH₃, NH₃, HCN, H₂SO₄, NaOH, aldehydes, organic acids, and others. It should be noted that the deep cleaning of OPM from OSM leads to the loss of unrecoverable oil and OPM, which has a negative impact on the environment, including soil, groundwater, air, water, plants, animals, and humans during the transportation, storage, and use of OSM that is not thoroughly purified of OPM (up to 100%). Therefore, research into the effective purification of OSM from OPM has been identified as a significant environmental challenge.

Materials and methods

The composition of the OSM samples collected from the Heydar Aliyev Refinery was initially determined using known methods. Untreated industrial wastewater (IW) generated in the plant was added to these samples filled into the separating funnels at a ratio of 1:5 and mixed. The amount of OPM in the used IW was determined using an extraction method. The continuation of the experiment was conducted according to the methods that we had previously developed and described in the literature [12-14]. In the experimental part of the research, we conducted the following activities.

A mixture containing 50 grams of OSM and 250 grams of IW was placed in a separatory funnel. 10 milliliters of the initial gasoline fraction was then added. The entire mixture was stirred intermittently for one hour at room temperature. A 5% solution of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts (referred to as component K) in a 1:1 ratio was added to the mixture in different volumes in the separatory funnel and the mixture was stirred for two hours.

Experiments were conducted depending on the amount of component K used as a coagulant. After each experiment, the separated organic, aqueous, and solid phases were collected in pre-weighed glass containers and their quantities were measured. During the experiment, we found that when OPM is purified from the composition of OSM using the coagulation method, the mixture must be extracted first to prevent the formation of a coarse (continuous) dispersed system in the final mixture. Since the initial gasoline fraction, used as an extractant, contains a mixture of iso-C₅H₁₂ and iso-C₆H₁₄ and their normal forms as well as other organic compounds with solvent properties, it can be considered a more effective extractant compared to the known petroleum ether or the i-C₅H₁₂/n-C₆H₁₄ mixture. At the same time, it should be noted that the initial gasoline fraction is cheaper than petroleum ether and i-C₅H₁₂ and n-C₆H₁₄ compounds.

Thus, a method for the purification of up to 99,98% of OPM from the composition of an OSM sample, determined by our team under optimal conditions, was developed. The initial gasoline fraction was used as the extractant, and a mixture of 5% solutions of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts (component K), prepared in a 1:1 ratio, was used as a coagulant.

Based on the results obtained, it can be concluded that the use of component K as a coagulant has a higher effectiveness than the removal of OPM from OSM when these salts are used separately as coagulants.

The results of our previous research into the purification of OSM samples from OPM using 5% solutions of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts, individually, are presented in Tables 1 and 2.

Table 1.

The results of the research into the purification of OSM samples from OPM using a 5% solution of Fe₂(SO₄)₃ salt

Table 2.

 The results of the research into the purification of OSM samples from OPM using a 5% solution of Al₂(SO₄)₃ salt

Results and discussion

The results of the research are presented in Table 3.

Table 3.

The results of purification of OSM samples from OPM using a mixture of a 5% solution of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts

Based on the information provided and the results of the study, we can offer the following explanations.

As is known, salts formed from strong acids and weak bases undergo hydrolysis due to the exchange of ions with water. The acidic environment of the resulting solution has a pH of less than 7. Therefore, a mixture of solutions of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts undergoes hydrolysis in water. As a result of the hydrolysis of both salts:

Fe₂(SO₄)₃ + 6H₂O → 2Fe(OH)₃ + 3H₂SO₄

Al₂(SO₄)₃ + 6H₂O → 2Al(OH)₃ + 3H₂SO₄

In the mixture of OSM and IW the H₂SO₄ acid presents in solution reacts with various carbonates and other compounds found in wastewater:

MgCO₃ + H₂SO₄ = MgSO₄ + H₂O + CO₂

CaCO₃ + H₂SO₄ = CaSO₄ + H₂O + CO₂

When a mixture of solutions containing Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts was used in the cleaning process for OSM, both salts underwent hydrolysis and interaction with each other. This had a positive impact on increasing the coagulation strength of the solution. Thus, the fact that each salt is a coagulant substance in its own right and hydrolyzes to a similar extent causes synergistic enhancement of coagulation efficiency, as a result of the positive influence they have oneach other. In general, there has been a lot of information about the coagulation process in technical literature.

During the study, when the initial gasoline fraction was used as an extractant and each of the Fe₂(SO₄)₃ and Al₂(SO₄)₃ compounds were used separately as coagulants, the graphs of the coagulation efficiency depending on the volume of the extractant and these compounds are shown in Figures 1 and 2. When the initial gasoline fraction is used as an extractant, the efficiency of removing OPM from the OSM sample is obtained in the range of 65-78%.

Figure 1. The dependence of the efficiency of the purification of OPM from OSM on the volume of the initial gasoline fraction used as an extractant – ε, and the dependence on the volume of a 5% solution of Fe₂(SO₄)₃ compound as a coagulant – K₁

Figure 2. The dependence of the efficiency of the purification of OPM from OSM on the volume of the initial gasoline fraction used as an extractant – ε, and the dependence on the volume of a 5% solution of Al₂(SO₄)₃ compound as a coagulant – K₂

Figure 3. The dependence of the efficiency of the purification of OPM from OSM on the volume of the initial gasoline fraction used as an extractant – ε, and the dependence on the volume of a mixture of a 5% solution of Fe₂(SO₄)₃ and Al₂(SO₄)₃ compounds in a 1:1 ratio – K

As can be seen in the graph in Figure 3, the efficiency of the purification (coagulation) process of OPM from OSM can be explained based on the volume of the K component. Therefore, similar to other coagulants, when a certain amount (or concentration) of K component is used, the efficiency of the coagulation process decreases.

The explanation of this phenomenon can be found in scientific literature [12-14].

Based on the results of the research, the new method developed can guarantee the purification of OPM from OSM formed in ORI by 99,98%.

When this method is used, it is possible to achieve results that are of great economic and environmental significance. For example, it is possible to recycle hundreds of tons of OPM using 5% solutions of cheap Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts in a 1:1 ratio, as well as the initial gasoline fraction. At the same time, it is also possible to use a mechanical mixture containing up to 0,05% OPM in road construction and brick and expanded clay production.

Therefore, the prevention of atmospheric, groundwater and soil pollution caused by OSM through the 99,98% purification of OPM from OSM can be considered a scientifically sound approach.

Conclusion

In this research, we studied the purification of OSM using Fe₂(SO₄)₃ and Al₂(SO₄)₃ coagulants. We used technical gasoline (a primary gasoline fraction) as an extractant and 5% solutions of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts as a coagulant to conduct the experiment. Based on the results, we established the dependence of the coagulation process (or the efficiency of cleaning of OPM from OSM on the concentration of the coagulant. The efficiency of this process using a 5% solution of Fe₂(SO₄)₃ and Al₂(SO₄)₃ salts as a coagulant was found to be 99,98%.

References:

1. Bahonina E.I. Sovremennye tehnologii pererabotki i utilizacii uqlevodorodsoderzhashih othodov // Bashkirskiy himicheskij zhurnal. 2015, tom 22, №1, s. 20-29.
2. FONTS I., GEA G., AZUARA M., ÁBREGO J., ARAUZO J. Sewage sludge pyrolysis for liquid production: A review. Renew. Sust. Energ. Rev. 16, 2012.
3. Gron V.A., Korostovenko V.V., Shahray S.Q., Kaplichenko N.M., Galayko A.V. Problema obrazovanija, pererabotki i utilizacii nefteshlamov // Uspehi sovremennogo jestestvoznanija. 2013, № 9, s. 159-162.
4. Jankovoj D.S. Novaja tehnologija utilizacii nefteshlamov // Ekologija proizvodstva. 2014, №9, s. 47-51.
5. LIN B., HUANG Q., CHI Y. Co-pyrolysis of oily sludge and rice husk for improving pyrolysis oil quality. Fuel Process. Technol. 177, 2018.
6. LI J., SONG X., HU G., THRING R. Ultrasonic desorption of petroleum hydrocarbons from crude oil contaminated soils. J. Environ. Sci. Health A. 8, 2013.
7. Ling CC, Isa MH. Bioremediation of oily sludge contaminated soil by co-composting with sewage sludge. J Sci Ind Res. 2006;65:364–369.
8. Mazlova E.A., Mesherjakov S.V. Problema utilizacii nefteshlamov i sposoby ih pererabotki. Uchebnoe posobie. M.: Noosfera, 2001, 52 s.
9. Mihaylova T.V. Problemy pererabotki nefteshlamov [Elektronnyj resurs] / T.V. Mihaylova, S.V. Leont’yeva // Promyshlennaja ekologija. 2008.
10. Mater L, Sperb RM, Madureira L, Rosin A, Correa A, Radetski CM. Proposal of a sequential treatment methodology for the safe reuse of oily sludge-contaminated soil. J Hazard Mater B. 2006;136:967–971.
11. NA S, PARK Y, HWANG A, HA J, KIM Y, KHIM J. Effect of ultrasound on surfactant-aided soil washing. JPN. J. Appl. Phys. 46, 2007.
12. Osmanova T.M. Pererabotka smesi nefteshlamov novym razrabotannym himicheskim metodom i jejo pervonachalnie rezul’taty // Jestestvennye i tehnicheskie nauki. Moskva: Sputnik+, 2020, № 3, s. 20-22.
13. Osmanova T.M. Ekologicheski effektivnaja ochistka obrazujushejsja v neftepererabatyvajushej promyshlennosti nefteshlamovoj smesi himicheskim metodom // Jestestvennye i tehnicheskie nauki. Moskva: Sputnik+, 2022, № 4, s. 36-40.
14. Tahmina Osmanova, Sevinj Hajiyeva, Giyas Bayramov. Study of cleaning up of petroleum waste mixture shaped in oil recycling industry with FeCl₃ // Proceedings of Azerbaijan high technical educational institutions. Tallinn: IRETC. MTÜ, 2024, volume 43 (05), ISSUE 08-02 2024, p. 121-128.
15. XIAO W., YAO X., ZHANG F. Recycling of oily sludge as a roadbed material utilizing phosphogypsum-based cementitious materials. Advances in Civil Engineering. 2019. https://doi.org/10.1155/2019/6280715