BENZENE-TOLUENE Distillation Packing Column

Contents

Introduction

Task

1. Process calculation

2. Defining Geometric Dimensions

3. Hydraulic calculation

4. Thermal calculation

5. Thermal insulation calculation

6. Structural and mechanical calculation

Conclusion

Literature

Introduction

Rectification is the mass exchange process of separating liquid homogeneous mixtures of volatile components by multiple sequential evaporation and condensation processes.

For the practical implementation of such a process, it is necessary that the vapor and liquid phases must be in a non-equilibrium state before contacting each other. Since the pressure for the phases remains the same constant, the phase temperatures must therefore be different. Upon contact between phases, heat exchange occurs: the steam temperature is higher than the liquid temperature, therefore, the steam condenses and gives its heat to the liquid, which in turn evaporates. As a result of this heat and mass exchange, the generated steam is enriched with a low boiling component, and the liquid with a high boiling component. Since the system tends to equilibrium, the temperatures of the resulting vapors and liquid are equalized.

Such repeated contact of vapors and liquid is carried out in practice in distillation columns, the volume of which is filled with contact devices for forming the contact surface of phases. as a rule, distillation columns operate on the basis of countercurrent in general throughout the apparatus, while in each separate section of the formation of the phase contact surface, the phase interaction schemes can be of a wide variety. To ensure non-equilibrium states of steam and liquid, heat is supplied to the lower part of the column (cube), and heat is removed in the upper part of the column (reflux). Diagram of continuous rectification plant for separation of binary mixture is given in Figure 1.

The initial mixture, with the content of low boiling component Xf in the amount of F, is supplied to the feed tray (evaporation space) with temperature tf. On the feed tray, a flash process (OI) occurs, resulting in a vapour phase enriched in LC and a liquid phase enriched in HC. The liquid phase flows down from the feed tray and enters the bottom of the column, where intensive evaporation occurs. The generated steam is fed down the column and moves towards the flowing liquid. Heat and mass exchange between steam and liquid occurs all the way, since the steam supplied to each tray has a temperature higher than the liquid supplied to this tray from above. As a result of mass exchange at the outlet of the column, the distillate vapor contains mainly a low boiling component, and the liquid in the bottom of the column contains mainly a high boiling component.

Distillate effluent from column is subjected to reflux process with further separation of flow into product (P) with content of HC Xr and liquid phase, reflux in amount of (F) with content of HC Xf. Reflux is supplied to the column reflux from above. The high NC content of the reflux stream predisposes that at the top of the column (from the feed tray upwards) the vapor phase is mainly strengthened by the low boiling component. For this reason, the top of the column is called reinforcing or concentration. The lower part of the column (from the feed tray down) is called the exhaustive or stripping part, since it is in this part that the main distillation of LC from liquid to steam occurs. In the most general case reflux of the column with reflux can be carried out according to various versions [1.6].

However, in order to simplify the calculations, the following irrigation option is proposed in these guidelines: distillate steam of the composition YG enters the reflux condenser, where its complete condensation occurs and then the resulting condensate is divided into two streams: hot reflux is supplied for irrigation, and the remaining part of condensate, passing through the refrigerator, is removed from the unit and supplied in the form of finished product P with content of NC chr to the reflux tank. The feed mixture in an amount of F with an LC content of Xf may be fed to the feed tray in the column at various states and temperatures. Most often, the initial mixture is preheated in a heat exchanger to boiling point and supplied in the form of a boiling liquid.