STUDY OF SEPARATION OF SOLVENT FROM PYROCONDENSATE FOR DISSOLVING HYDROCARBONS IN OIL SLUDGE

ABSTRACT

This article investigates the possibility of using the 53–85 °C boiling fraction of pyrocondensate, separated through fractional distillation, as a solvent for extracting hydrocarbons from oil sludge – a major waste product in the oil industry. The physical and chemical properties of the separated fraction, including density, viscosity, boiling point, and vapor pressure, were analyzed and found to be comparable to benzene. The study confirms the potential of this fraction as an effective, environmentally safe, and economically viable solvent for industrial applications.

АННОТАЦИЯ

В данной статье исследована возможность использования фракции пироконденсата с температурой кипения 53–85 °C, выделенной методом фракционной дистилляции, в качестве растворителя для извлечения углеводородов из нефтяных шламов – одного из основных отходов нефтяной промышленности. Проанализированы физико-химические свойства выделенной фракции, включая плотность, вязкость, температуру кипения и давление паров, которые оказались близкими к свойствам бензола. Результаты подтверждают потенциал данной фракции как эффективного, экологически безопасного и экономически целесообразного растворителя для промышленного применения.

Keywords: pyrocondensate, fractional distillation, solvent, oil sludge, hydrocarbons, extraction.

Ключевые слова: пироконденсат, фракционная перегонка, растворитель, нефтешлам, углеводороды, экстракция.

Introduction. Oil sludge is considered one of the most critical environmental issues among the waste products generated by the oil industry. These sludges contain various hydrocarbons, water, sediments, and other harmful components that can cause serious environmental consequences if released into the surroundings [1-3]. Therefore, the recovery of hydrocarbons from oil sludge through recycling processes is a pressing issue. In this context, the use of efficient and economically viable solvents is one of the key factors in ensuring the effectiveness of the technological process.

This study explores the potential use of a pyrocondensate fraction as a solvent for dissolving hydrocarbons present in oil sludge. Specifically, a light fraction boiling up to 85 °C was isolated and its solvent properties were evaluated to assess the efficiency of the extraction process. Research in this area contributes to improving the efficiency of oil industry waste processing, promoting the recovery of hydrocarbons as a secondary raw material, and reducing environmental impact.

Materials and methods. Pyrocondensate is a complex mixture formed as a result of the pyrolysis of oil, gas, or hydrocarbon-based waste. In its liquid state, it contains a variety of saturated, unsaturated, and aromatic hydrocarbons. Among pyrolysis products, pyrocondensate holds particular significance due to its potential use as a raw material in various industrial applications. However, to utilize it efficiently, it is essential to isolate valuable fractions and extract solvent components from its composition. Pyrocondensate primarily consists of the following key components: light fractions (C₅–C₉), including pentane, hexane, benzene, toluene, and others; heavy fractions (C₁₀₊), such as naphthenes and aromatic hydrocarbons; and solvents including both aromatic (benzene, toluene, xylene) and aliphatic (n-hexane, cyclohexane) compounds [4; 5].

The fractional composition of pyrolysis distillate was determined in the laboratory by distillation in accordance with the interstate standard GOST 2177-99 (ISO 3405-88). During this process, fractions with different boiling ranges are sequentially distilled at gradually increasing temperatures. Each distillate fraction boils within a specific temperature interval, having an initial boiling point (T_ib) and a final boiling point (T_fb) determined by its chemical composition. The distillation procedure was carried out three times, and the average values were recorded.

Results and discussion. The separation of solvents from pyrocondensate is a crucial stage in the industrial processing of pyrolysis products. Fractional distillation is one of the most effective and widely applicable methods for this purpose. By extracting solvent components, the value of pyrocondensate increases, making it a useful raw material for petrochemical and polymer production.

According to the data in Table 1, the average density of pyrocondensate at standard temperature (20 °C) is ρ₍₂₀₎ = 842 kg/m³, and its kinematic viscosity coefficient is ν₍₂₀₎ = 0.779 mm²/s.

Table 1.

Key results of pyrocondensate distillation experiments

The initial boiling point–i.e., the temperature at which the first drop of liquid condenses–was the same in all experiments and equaled 53 °C for the pyrocondensate. The distillation of the distillate samples (within the range of 53–182 °C) yielded fractions throughout the experiments. According to the results of each trial, the fractional yield was 97%, while the loss values varied between 1% and 1.2%.

The graph in Figure 1 shows the fractional composition curve of the pyrocondensate, constructed based on the average experimental data.

Figure 3.1. Fractional composition curve of the pyrocondensate

As a result of the experiments, it was found that 30–85% of the pyrocondensate consists of extractable solvents, mainly benzene, toluene, and xylenes.

In the oil industry, sludge contains a significant amount of hydrocarbons, and recovering these compounds is of great economic and environmental importance. To maximize hydrocarbon extraction, the physical and chemical properties of the solvent used–particularly its boiling point–play a crucial role. Ideally, the solvent should have a low boiling point, as this reduces the likelihood of hydrocarbon evaporation, ensuring a greater proportion remains dissolved in the solvent phase.

For this purpose, the composition of pyrocondensate was studied as a potential solvent. Based on its fractional composition, the fraction distilled in the boiling range from the initial boiling point up to 85 °C was selected. The choice of this fraction was primarily guided by the physicochemical properties of benzene, particularly its boiling point of 80.1 °C. According to available data [6-8], benzene effectively dissolves hydrocarbons found in oil, suggesting that this particular fraction of pyrocondensate may exhibit similar solvent properties.

According to the analysis of the experimental data presented in Table 1 and Figure 1, the fraction of pyrocondensate distilled in the boiling range from the initial boiling point up to 85 °C constitutes approximately 50% of the total volume. This indicates that the selected fraction represents a significant portion of the pyrocondensate and highlights its high potential and value as an effective solvent.

This fraction was selected as the primary solvent for the extraction of oil sludge. To enhance the efficiency of the extraction process and determine its optimal parameters, the key physicochemical properties of the selected fraction were thoroughly analyzed. Specifically, parameters such as density, viscosity, boiling point, vapor pressure, and other important thermodynamic indicators were determined. The obtained results are systematically presented in Table 2.

Table 2.

Physicochemical properties of the pyrocondensate fraction distilled in the boiling range up to 85 °C

Table 2 compares the physicochemical properties of benzene with those of the pyrocondensate fraction distilled in the boiling range up to 85 °C. As shown in the table, this pyrocondensate fraction exhibits solvent characteristics similar to those of benzene and can therefore be considered a potential solvent for the extraction of oil sludge.

From the above table, it is evident that the pyrocondensate fraction within the 53–85 °C range possesses physical and chemical properties similar to those of benzene. The low boiling point and high vapor pressure of this fraction enable effective dissolution of hydrocarbons during the extraction process.

Conclusion. The conducted studies on the fractional composition of pyrocondensate and the separation of low-boiling solvents allowed for identifying an effective solvent applicable in the oil industry. Fractional distillation yielded a fraction boiling within the 53–85 °C range, whose physicochemical properties were found to be close to those of benzene. In particular, its low density, high vapor pressure, and good solubility demonstrated the suitability of this fraction as a solvent for dissolving hydrocarbons.

The analyses showed that fractions boiling up to 85 °C constitute approximately 50% of the pyrocondensate composition, which increases the feasibility of industrial-scale application of this fraction. Based on the results, it was proven that this fraction can be used as the primary solvent for efficient extraction of hydrocarbons from oil sludge. This approach is significant for reducing environmental impact, improving the efficiency of oil waste processing, and obtaining an economically beneficial solvent.

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