Simulation of a Multistage Distillation Process in a Rotary Disc Device

Abstract

The final stage of the miscella distillation process is the stage that affects the course of the next technological stages and in many respects predetermines the quality of the product.Improvement of this process is especially important in connection with the use of fundamentally new equipment for its implementation, further increase in the efficiency of the process due to the release in this process of a new secondary product - fatty acids.

The final distillation processes for cottonseed oil miscellas and the equipment used in industrial practice for their implementation have their limitations. Further improvements in the traditional way of technological equipment may not yield the expected results in practice. Achieving significant technological results in this area requires a new approach to the distillation of cottonseed oil miscellas and further development of the theoretical and practical basis of the process, the organization of the process in new, highly efficient methods, and the development and introduction of new types of intensive equipment.

Based on mathematical modeling of the distillation process and computer study of models, methods have been determined for creating compact devices with rational design and technological parameters, reducing the consumption of structural materials used in the manufacture of distillers, saving energy resources.

In order to reduce the boiling point of the miscella during the process, taking into account the insolubility of the components of the mixture in water, high-temperature water vapor is added to its composition in an open manner as an additional component. In the final stage of the distillation process, the driving component is separated according to the equilibrium state between the liquid and vapor phases.

It is known that the boiling point of a mixture depends directly on the proportions of the components in it. The boiling point of hexane is below the С₁₀ boiling point of capric acid. Therefore, as the proportion of capric acid in the mixture increases, so does its boiling point.

Taking into account the technological mode of the final distillation process, the total pressure in the system was initially taken equal to Р=10 kPa, and then its value was increased to 20, 30, 40 kPa.A t-х-у diagram was constructed, representing the equilibrium concentrations of a mixture of free fatty acids at various temperatures and pressures that dissolve certain values of the saturated vapor pressure of the components. As the temperature of the mixture in the process increases and the pressure in the apparatus decreases, the proportion of free fatty acids in the vapor phase increases.

One of the main accelerating factors is the multiple atomizations of the liquid phase during the stripping of cottonseed oil miscellas in an open water vapor environment. When the miscellas are scattered by means of fast-rotating discs, a new dispersed phase consisting of very fine droplets is formed. The smaller the diameter of the liquid droplets formed at this time, the greater their total surface area. As a result, the value of the contact surface between the liquid and vapor phases increases, and the processes of heat and metabolism between them accelerate. Multiple re-scattering of miscellas in the apparatus results in multiple renewals of the liquid phase.

The distillation process in the apparatus was carried out in six stages. Researches on a computer model of the process studied each stage of the device - the change in the concentration of the solvent in the liquid and vapor phase overtime on each plate, as well as the change in the concentration of free fatty acids in the vapor phase.

In a multi-stage distillation process, the concentration of the lightly volatile component in the liquid phase decreases over time, from the first stage to the next.At this time, the concentration of the light volatile component in the vapor phase gradually increases.