COMPARATIVE ANALYSIS OF THE EFFICIENCY OF OIL AND GAS CONDENSATE MIXTURE DISTILLATION IN PACKED VALVE AND VALVE COLUMNS

ABSTRACT

The aim of this work is to conduct a comparative analysis of the efficiency of distillation of an oil and gas condensate mixture (30% oil + 70% gas condensate) in packed valve and valve columns. Distillation was carried out under various temperature regimes to determine the optimal conditions for separating light and heavy fractions. The study found that the packed valve column provides more efficient separation of light fractions at lower temperatures, which helps reduce energy consumption for distillation. Conversely, the valve column ensures a more uniform separation of the mixture components, which is preferable when precise control of the product composition is required. Analysis of the fractional composition of the mixture showed that light fractions begin to be released in the packed valve column at temperatures between 52-180°C, and the density and viscosity of the fractions depend on the distillation temperature.

АННОТАЦИЯ

Цель данной работы – провести сравнительный анализ эффективности перегонки нефтегазоконденсатной смеси (30% нефти + 70% газоконденсата) в насадочно-клапанной и клапанной колоннах. Перегонка проводилась при различных температурных режимах, чтобы определить оптимальные условия для выделения легких и тяжелых фракций. В ходе исследования установлено, что насадочно-клапанная колонна обеспечивает более эффективное выделение легких фракций при более низких температурах, что позволяет сократить энергозатраты на перегонку. Клапанная колонна, напротив, обеспечивает более равномерное разделение компонентов смеси, что предпочтительно при необходимости контроля состава продукта. Анализ фракционного состава смеси показал, что в насадочно-клапанной колонне легкие фракции начинают выделяться уже при температуре 52-180°C, а плотность и вязкость фракций зависят от температуры перегонки.

Keywords: oil and gas condensate mixture, packed valve column, valve column, distillation, fractions, physicochemical properties.

Ключевые слова: нефтегазоконденсатная смесь, насадочно-клапанная колонна, клапанная колонна, перегонка, фракции, физико-химические свойства.

Introduction. The efficiency of crude oil primary processing units (atmospheric distillation units, ADUs) is one of the key factors for enhancing the profitability of a refinery. This is due to the high energy consumption of the distillation process itself and the large throughput of feedstock in ADUs, making them the largest energy consumers at refineries [1].

Packed columns are widely used for mass transfer processes between gas and liquid in various areas of chemical and petrochemical technology [1-3]. The type of packing contact device determines the intensity of mass transfer and the overall efficiency of the apparatus [4-6]. Numerous studies have been devoted to improving the design of packing elements, with the goal of increasing the contact surface area of the phases [7], enhancing the mass transfer efficiency of the packing [8-10], and improving hydrodynamic characteristics [11-13].

The distillation of oil and gas condensate mixtures (OGCM) in different columns is an important step in the refining industry. Comparing the efficiency of packed valve and valve columns helps determine optimal conditions for fraction separation and improving the quality of the final product. Studies have shown [1, 2] that packed columns offer several advantages over tray columns, including lower hydraulic resistance per unit of transfer height and the ability to operate under high gas and liquid loads.

Unlike tray columns, in which gas velocity is limited by increased liquid entrainment between trays and low overflow capacity, packed columns can operate at atmospheric pressure at gas velocities of up to 3.5 m/s. This allows a significant reduction in column diameter and an increase in their throughput. Additionally, packed columns have a simpler design and are highly resistant to fouling, reducing the risk of blockages and ensuring reliable operation [3, 4].

Valve columns, in turn, are characterized by more uniform separation of mixture components and stable control of product composition. However, their capacity and efficiency decrease at high gas-liquid flow rates [5]. Thus, the choice of the optimal column type for distillation of oil and gas condensate mixtures depends on the specific goals and conditions of the process.

Figure 1. Comparative design of column elements: valve tray and 20x30 spiral-prismatic packing

Figure 1 shows a comparative design of elements of two types of columns used in the study. On the left, a valve tray is depicted, which is typically used to evenly distribute liquid and gas flow throughout the column, ensuring stable separation. On the right, a spiral-prismatic packing of size 20x30 mm is shown, designed to increase the contact surface between phases, significantly enhancing mass transfer efficiency and improving the separation of components during the distillation process.

Today, the development of new efficient packing for packed columns has enhanced their competitiveness and effectiveness in oil refining. This study aims to conduct a comparative analysis of the efficiency of distilling an oil and gas condensate mixture (OGCM) in packed valve and valve columns to determine the optimal conditions for the separation of light and heavy fractions.

The temperature range of the experiments was from 20 to 350°C. In each experiment, the yield of light fractions from the oil and gas condensate mixture was recorded, as well as the temperature at which component separation occurred. Standard methods for measuring boiling temperatures and determining fraction yields were used to monitor the distillation process. The equipment used ensured high precision in maintaining the set temperature conditions, while measuring instruments allowed for a detailed analysis of the composition of the obtained fractions.

Methods and Materials. The study involved an oil and gas condensate mixture composed of 70% gas condensate and 30% oil, sourced from the Kokdumalak field. The experiments were conducted at the Institute of General and Inorganic Chemistry of the Academy of Sciences of the Republic of Uzbekistan. In the "Processes and Apparatus of Chemical Technology" laboratory, an experimental setup was designed and installed, intended for the rectification of multicomponent mixtures under atmospheric and excess pressure conditions (Fig. 2).

The purpose of the experiment was to study the rectification process and investigate the physicochemical properties of the distillates obtained from the OGCM (30% oil and 70% gas condensate) [15].

An experimental setup was developed for processing hydrocarbon feedstock (Fig. 3), which includes an evaporative still (1), equipped with a gas burner (5) for heating the feedstock. The setup consists of three sections, including a packed section (6), connected by flanged joints (9). It also includes a condenser (3), a distillate receiver (4), and a control system with a manometer, thermometer, and regulating valves to ensure precise control of temperature regimes and pressures during the distillation process.

The experimental setup for processing hydrocarbon feedstock consists of a column with a diameter of 100 mm and a total height of 1380 mm, including a distillation pot with a capacity of 22 liters. During the study, two experiments were conducted: one using a valve column and the other with a packed-valve column. A mixture of oil and gas condensate (30% oil and 70% gas condensate) with a volume of 13.75 liters (10 kg) was heated in the column at temperatures ranging from 20 to 360°C, causing the lighter components of the mixture to evaporate according to their boiling points.

The evaporating components passed through the valve sections of the column, where the vapor interacted with the condensing liquid flowing down to the lower plates through feed pipes. The hydrocarbon vapors were then cooled in the condenser and collected in a measuring receiver. Temperature and pressure were monitored at all stages using manometers and thermometers to ensure precise process control.

1 - Column pot (boiler); 2 - Valve section of the column; 3 - Condenser (cooler); 4 - Distillate collector; 5 - Gas burner; 6 - Packing section of the column; 7 - Valve tray; 8 - Feed pipe; 9 - Flanged connections; 10, 14 - Pressure gauge; 11, 15 - Thermometer; 12 - Inlet pipe for cold water; 13 - Outlet pipe for water; 16, 18 - Valve.

Figure 2. Setup for studying the rectification process of multicomponent hydrocarbon mixtures

In the second experiment, the upper section of the column was replaced with a packed section, which increased the contact surface between the vapor and the liquid, improving the heat and mass transfer processes. As a result of the distillation of the oil and gas condensate mixture in both types of columns, parameters such as temperature and mass fraction of the output fractions were recorded. The results of the experiment were plotted to compare the efficiency of the valve column and the packed-valve column. Special attention was given to the degree of fraction separation and the quality of the obtained products.

The main parameters measured during the study included the initial boiling temperature, the degree of separation of light and heavy fractions, and the fractional composition. Standard analytical methods in accordance with ISO 12185 and GOST 33-2000 were used to determine the density and viscosity of the fractions.

The water content in the oil-gas condensate mixture and distillates was determined by the Dean and Stark method in accordance with GOST 2477-65. Mechanical impurities were identified using a Soxhlet extraction apparatus following GOST 6370-2018.

The cloud point, freezing point, and the limit temperature of oil and gas condensate mixture were determined using the OPLCM "CRYSTAL" setup according to ISO 9001 standards.

The sulfur content in gasoline fuel was measured using the Spectroscan S equipment following the methods of GOST R 51947-2002 and ASTM D 4294-98. To ensure the reliability of the analysis, deviation determination methods in accordance with GOST were used. The mean of two parallel measurements was employed as the calibration standard. This average was calculated considering accuracy and adherence to the established confidence level of 95%, in accordance with state standard requirements.

Results and Discussion. In this study, the main physicochemical properties and the composition of hydrocarbons of the oil and gas condensate mixture (30% oil and 70% gas condensate), as well as gasoline fractions obtained from the Kukdumalak field, were determined.

The fractional composition of the mixture was determined using an experimental setup, in accordance with ASTM 2892 and ASTM 5236 methodologies, with the construction of a true boiling point (TBP) curve. Figure 3 shows the atmospheric distillation graph of oil up to 350 °C.

Valve Column (Curve 1): In the valve column, a higher initial temperature for the onset of fraction distillation is observed, with a gradual temperature increase up to 350 °C. This indicates that the evaporation of light components occurs gradually, allowing for a stable separation of heavy and light fractions.

Figure 3. Results of experiments on the study of the fractional composition of the oil and gas condensate mixture (30% oil and 70% gas condensate), carried out using the packed-valve column (2) and valve column (1)

Packed-Valve Column (Curve 2): The onset of distillation in the packed-valve column occurs at a lower temperature compared to the valve column. The curve demonstrates a sharp rise in temperature after achieving 60% of the fraction yield, indicating a more active evaporation of light components. The packed-valve column shows higher efficiency in separating light fractions at lower temperatures, which enables energy savings. On the other hand, the valve column ensures a more uniform distribution, which may be preferable when strict control over the final product composition is required.

Based on the analysis, it can be concluded that the packed-valve column is more suitable for the rapid and energy-efficient separation of light components. Subsequently, a study was conducted on the physicochemical characteristics of distillate fractions obtained from the oil and gas condensate mixture (30% oil and 70% gas condensate) during distillation in the packed-valve column [15]. The results of the measurements of the physicochemical properties of the mixture are presented in Table 1.

Table 1.

Primary Properties of the Oil and Gas Condensate Mixture (30% Oil, 70% Gas Condensate) from Kukdumlok Field.

Table 1 was identified as the most promising for further processing due to its relatively low density (760 kg/m³) and kinematic viscosity (1.415 mm²/s at 20°C), indicating high fluidity and lightness. Additionally, the low water content (0.075%) and minimal mechanical impurities (0.037%) reflect its high purity. These properties make Sample 1 the most favorable candidate for further processing among all analyzed samples.

The oil and gas condensate mixture from the Kukdumlok field falls under the naphthenic-paraffinic group of hydrocarbons. According to the national standard ЎзДСт 3031:2015, this mixture is classified as 2.0.1.0, indicating its hydrocarbon profile. The analyses revealed that the mixture contains significant quantities of gasoline and kerosene fractions, classifying it as light oil. The density of the mixture ranges from 760 to 770.8 kg/m³, with viscosity between 1.415 and 1.448 mm²/s at 20°C.

The pour point of the mixture is between 17 and 19°C, which, combined with low levels of water and mechanical impurities, confirms its high quality. The paraffinic components have a pour point within 45–48°C. The fractional composition of the mixture indicates a broad temperature range, with a distillation yield of up to 87.7% for fractions boiling between 70 and 350°C. The mixture is also characterized by minimal resin content (2.7–4.9%) and asphaltenes (0.35–0.59%) (Table 1). To conduct a more in-depth analysis of distillates, physicochemical parameters of gasoline and oil distillates obtained from Well No. 1 were examined. The results of the gasoline properties are presented in Table 2 and Figure 4.

Figure 4. Dependence of Yield and Density of Gasoline Fraction on Temperature

Figure 4 illustrates the relationship between the density of the gasoline fraction at 20°C and the yield of fractions as a function of distillation temperature from an oil and gas condensate mixture (30% oil + 70% gas condensate) from the Kukdumlok field, obtained using a packed valve column.

Blue Line (Left Y-Axis, Fraction Yield, %):

• The blue line demonstrates the change in the yield of fractions as the distillation temperature increases. Initially, at a temperature of 52°C, the yield is about 4%. As the temperature rises to 180°C, the yield of light hydrocarbons also increases, reaching 72.25%. This trend indicates an effective separation of light hydrocarbons in the packed valve column, resulting in a higher yield of gasoline fractions.

Orange Line (Right Y-Axis, Density at 20°C, kg/m³):

• The orange line shows the variation in density with increasing temperature. The initial density at 52°C is 684 kg/m³, which reflects the predominance of light hydrocarbons. As the temperature increases, the density rises, reaching 754 kg/m³ at 180°C. This indicates a gradual transition to heavier hydrocarbons, which is characteristic of gasoline fractions.

Table 2.

Physicochemical Properties of the Gasoline Fraction (200–180°C) of the Oil and Gas Condensate Mixture (30% Oil + 70% Gas Condensate) from the Kukdumlok Field.

The physicochemical characteristics of the gasoline fraction from the oil and gas condensate mixture obtained from the Kukdumlok field are presented in Table 2. These data include temperature indicators of the fractional composition as well as sulfur content, reflecting the properties of the raw material and its suitability for further processing.

The sulfur content in the gasoline fraction is 1.55% by mass, which remains constant across the entire temperature range from 52°C to 180°C. This indicates the necessity for further purification to remove unwanted sulfur compounds, as elevated sulfur levels can negatively impact the fuel's operational properties and increase its corrosive activity.

The temperature data for the fractional composition also illustrate how different components of the mixture evaporate at various points during distillation. For each temperature, initial boiling point, as well as temperatures at which 10%, 50%, and 90% of the fraction evaporate, are provided. For instance, at a distillation temperature of 80°C, the initial boiling point is 43°C, with 10% of the fraction evaporating at 67°C, 50% at 72°C, and 90% at 76°C. This data shows a transition from lighter hydrocarbons to heavier components, which begin evaporating at higher temperatures.

As the temperature increases, the complete evaporation of heavier hydrocarbon components becomes evident, as seen at temperatures ranging from 120°C to 180°C. The boiling points for initial, 10%, 50%, and 90% evaporation also increase, indicating the complexity of the hydrocarbon structure and the gradual transition to heavier fractions.

Overall, the data from Table 2 indicate that the gasoline fraction of the oil and gas condensate mixture has a wide temperature range for evaporation and stable sulfur content, suggesting the need for additional processing to improve fuel quality and enhance operational characteristics.

The results of the study showed that the packed valve column provides more active extraction of light fractions at relatively low distillation temperatures. The initial boiling point in this column was lower compared to the valve column. The temperature profile indicated a sharper increase after reaching 60% of fraction yield, indicating efficient separation of light fractions.

The valve column is characterized by a smoother increase in temperature up to 350°C. This distillation profile contributes to a more stable separation of heavy and light fractions, allowing for the production of a product with the desired fractional composition.

A comparative analysis of the efficiency of the packed valve and valve columns demonstrated that the former method enables more active extraction of light fractions at lower distillation temperatures, contributing to the production of high-quality products.

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