IMPROVING THE SEPARATOR DESIGN FOR MISCELLA DISTILLATION SYSTEMS IN OIL AND FAT PLANTS USING SPIRAL CONTACT ELEMENTS

ABSTRACT

The article explores methods to improve the efficiency of the extraction solvent (petrol) recovery process in oil and fat processing plants. Based on laboratory analysis using a Soxhlet apparatus, it was found that the oil content in recycled solvent and the solvent residue in the aqueous condensate range from 1.0% to 1.3%. These figures indicate the low separation efficiency of current distillation units in isolating solvent vapors from the liquid phase. To address this inefficiency, the study proposes a structural modernization of the separator by installing specialized spiral contact plates. The research demonstrates that the improved design optimizes flow hydrodynamics and prevents oil droplet entrainment into the solvent vapor stream. Implementing this technical solution reduces solvent losses by 1.0–1.5%, improves the solvating properties of the recycled petrol, and significantly enhances the plant's overall economic performance.

АННОТАЦИЯ

В статье рассматриваются методы повышения эффективности процесса рекуперации экстракционного растворителя (бензина) на масложировых предприятиях. На основании лабораторных исследований, проведенных с использованием аппарата Сокслета, установлено, что содержание масла в возвратном бензине и остаточное содержание растворителя в водном конденсате составляют 1,0–1,3%. Данные показатели свидетельствуют о низкой эффективности существующих сепарационных узлов в составе дистилляционных установок. Для решения данной проблемы предложено усовершенствование внутренней конструкции сепаратора путем интеграции специальных спиралевидных пластин (тарелок). Согласно результатам исследования, внедрение новой конструкции оптимизирует гидродинамику потока и предотвращает унос мелкодисперсных капель масла с парами растворителя. Это позволяет снизить технологические потери на 1,0–1,5%, повысить качество оборотного растворителя и увеличить экономическую эффективность производства.

Keywords: miscella distillation, solvent recovery, separator, spiral coil, hydrodynamics, loss reduction.

Ключевые слова: дистилляция мисцеллы, рекуперация растворителя, сепаратор, спиралевидная насадка, гидродинамика, минимизация потерь.

Introduction.

Solvent-based extraction is used to obtain vegetable oils. From an economic and environmental standpoint, the regeneration of these solvents determines the plant's overall efficiency. The benzene vapours generated during the distillation process are separated from the liquid phase (oil and water droplets) in separators before entering the condenser [1]. However, the separators currently in use cannot retain micron-sized droplets. As a result, droplets become entrained in the vapour stream. Figure 1 shows the process flow diagram for the primary distillation process.

Figure 1. Process flow diagram of the primary distillation process

During the distillation process, a large amount of solvent vapor is generated during the miscella boiling process, which carries the miscella, in the form of a thin film coating the inner surface of the steam-heated pipes, upwards at high speed. At this stage, the petrol vapours entering the separator became mixed with oil droplets, making separation difficult. This problem not only increases petrol waste but also reduces the heat-exchange efficiency of the condenser and leads to equipment corrosion. Based on the above, the purpose of this study is to provide a theoretical and experimental substantiation of the optimal technological regimes for a spiral separator. The primary focus is placed on determining the influence of the design features of tray elements on the phase separation efficiency coefficient and establishing the dependence of the critical vapor velocity on the physicochemical properties of the miscella.

Materials and Methods.

For the experiment, water samples from the reused benzene and condensate of the extraction workshop at the “Ideal Oil-Trade” oil plant were collected. They were analyzed in the laboratory of the Department of Food Technology at Namangan State University. Water samples from the reused benzine and the condensate were weighed at 100 g each and analyzed three times. To determine the benzine and oil content in the samples, a Soxhlet apparatus was used for the evaporation process. The experiment was repeated at three different temperature regimes (140 °C, 160 °C, 180 °C). The amount of oil recovered and the total system losses can be seen in the following figure 2 and table.

Figure 2. Soxhlet apparatus setup

Table 1.

Oil recovered and the total system losses

According to the results of the recycled petrol sample, as the temperature rises, less oil is observed to separate from the residual petrol. We can attribute this to the reaction rate and the high temperature. The higher the temperature, the faster the process proceeds, but because of the rapid evaporation rate, the oil in the mixture also vapourised along with the petrol. Therefore, the greatest amount of oil was released at 140 °C.

Table 2.

Values

Table 2 shows that during the analysis of the water leaving the condenser, a small amount of petrol and oil was found to have been mixed in. The solvent vapours directed to the condenser contain a small amount of oil, and the oil content in the petrol vapor can be reduced by improving the design of the separator. These figures confirm that a significant amount of oil remains in the petrol vapours leaving the distillatory.

Proposed Technical Solution and spiral installation mechanism.

The more oil remaining in the reworked petrol is removed, the lower its power output in subsequent stages and the poorer its ability to absorb oil from the sludge. By also separating the benzene present in the water discharged from the condenser, benzene consumption is reduced. The condenser water contains a small amount of benzene, while the benzene contains oil. To solve the problem, it is proposed to install a newly designed spiral inside the separator unit during the miscella vapourisation process. Practical work is underway in this regard. The proposed device allows the oil that is entering the vapor stream to be reclaimed by controlling the flow path of the petrol vapours. Spiral installation mechanism Inside the separator, as the vapor flow moves along the spiral towards the top, the flow direction changes abruptly. Liquid droplets, under the influence of inertia, strike the spiral surface, condense and run downwards. In this process, petrol vapours and oil are separated more effectively. The internal structure of the improved separator unit is shown in Figure 3.

Figure 3. Schematic of the improved separator unit

Hydrodynamic calculations. To increase the efficiency of the separator, the critical velocity (() of the vapour is calculated using the following formula:

where: – density of the liquid;  – vapour density; K – a coefficient dependent on the spiral design.

The value of the coefficient K in this study was determined based on empirical data specifically for spiral separation devices. In particular, for the optimized spiral design-which ensures a 98% droplet separation efficiency-the K value was refined experimentally, taking into account the geometric characteristics of the tray elements [1, 9].

Results and discussion

Comparative analysis between the separators currently used in vegetable oil production at oil mills and the proposed disc separator:

The installation of the spiral also helps to partially separate the water vapor in the steam, thereby improving the dielectric properties of the petrol and increasing its solvency in the subsequent extraction cycle [10]. This prevents benzene from mixing with the water leaving the condenser and also reduces benzene consumption. In this study, the efficiency coefficient K was adopted based on the standard operating parameters for spiral-type separators processing high-viscosity fluids like vegetable oil miscellas. Although the K value is influenced by multiple geometric variables, a constant value (or range) was utilized to evaluate the overall hydrodynamic stability of the system. Future empirical studies are planned to further calibrate this coefficient for various spiral tray configurations.

Conclusion

Studies have shown that the current distillation system in oil extraction plants incurs high losses. The 1.5% losses identified by Soxhlet apparatus are effectively addressed by fitting the separator unit with a newly designed spiral. The proposed disc separator significantly reduces petrol wastage. By bringing the quality of the reworked petrol up to international standards, the capacity of the misella to absorb oil increases. This significantly boosts the plant’s annual economic profit.

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