Distillation column flow-sheet

The most volatile product (myristic acid) is a small fraction of the feed, whereas the least volatile product (oleic—stearic acids) is most of the feed, and the palmitic—oleic acid split has a good relative volatility. The palmitic—oleic acid split therefore is selected by heuristic (4) for the third column. This would also be the separation suggested by heuristic (5). After splitting myristic and palmitic acid, the final distillation sequence is pictured in Figure 1. Detailed simulations of the separation flow sheet confirm that the capital cost of this design is about 7% less than the straightforward direct sequence. 

General Properties of Computerized Physical Property System. Flow-sheeting calculations tend to have voracious appetites for physical property estimations. To model a distillation column one may request estimates for chemical potential (or fugacity) and for enthalpies 10,000 or more times. Depending on the complexity of the property methods used, these calculations could represent 80% or more of the computer time requited to do a simulation. The design of the physical property estimation system must therefore be done with extreme care. 

Many industrial separations require a series of columns that are connected in specific ways. Some distillation programs can model such a system as a hypothetical single column with arbitrary cross-flows and connections and then carry out the distillation calculations for the modeled hypothetical column. Alternatively, such a system can be modeled as a process flow sheet using a process simulator. 

They simulate the steady-state operation of the process and can be used to draw-up the process flow sheet, and to size individual items of equipment, such as distillation columns. 

A batch distillation column with a diameter of 100 mm and a reactive packing height of 2 m (MULTIPAK I ) in the bottom section and an additional meter of conventional packing (ROMBOPAK 6M ) in the top section was used. The flow sheet of the column is shown in Figure 22. 

With this assumption, and using a modified Neumann model for HI/I2/H20 mixtures description, CEA (Leybros, 2009) devised a flow sheet for the iodine section which decomposes almost all incoming HI and therefore returns relatively pure products (the iodine return flow contains only 4 molar% water and less than. 3 molar% HI) to the Bunsen section, an important feature for the counter-current reactor. Secondary helium heat is provided to the boiler of the column (235 kj/mol), whereas all other heat needs are fulfilled through internal heat recovery, with the help of a heat pump which transfers heat from the products of the distillation column to its feed. Mainly because of the presence of this heat pump, the iodine section uses 60 kj/mol of electric power on top of the helium heat. 

The HI decomposition section flow sheets for both CEA and GA are heavily focused on efficient heat recovery. The basic principle for decomposition is the same for each. Reactive distillation of the HIX feed results in the production of hydrogen. The operating pressures in the distillation columns typically... 

Uncondcnsed vapour from the first tower is led to the bottom part of the second column which is scrubbed with the condensate obtained from the heating steam which condenses in the distillation equipment. The remaining vapour then leaves the second column and is led to a barometric condenser of standard design connected to a vacuum pump, which maintains a reduced pressure of 110 to 140 mm Hg in the whole distillation equipment and 40 to 60 mm Hg in the condensation. The distillation yield reaches 90 to 92 per cent. A flow sheet is shown in Fig. 140. 

Reactive distillation is in theory a simpler process than extractive distillation, but it has yet to be demonstrated experimentally. There are two key differences between reactive and extractive distillation. First, unlike the extractive process, the HI, azeotrope is not broken, so the composition in both the liquid and vapor phases is the same. Second, the reactive process must be conducted under pressure. Figure 4.7 shows a schematic of the reactive distillation flow sheet, and the processing conditions are listed in table 4.4. In this process, azeotropic HI, is distilled inside a pressurized reactive column and the HI gas within the HI vapor stream is decomposed catalytically, resulting in a gas mixture of HI, Ij, H2, and H2O. To accomplish this, the HI feed from Section I is first heated to 262°C from 120°C and is then fed into the reactive column. At the bottom of the column, the HI is brought to a boil at around 310°C, and this boiling HI vapor results in an equilibrium vapor pressure of 750 psi inside the distillation column. 

For the study of the process, a set of partial differential model equations for a flat sheet pervaporation membrane with an integrated heat exchanger (see fig.2) has been developed. The temperature dependence of the permeability coefficient is defined like an Arrhenius function [S. Sommer, 2003] and our new developed model of the pervaporation process is based on the model proposed by [Wijmans and Baker, 1993] (see equation 1). With this model the effect of the heat integration can be studied under different operating conditions and module geometry and material using a turbulent flow in the feed. The model has been developed in gPROMS and coupled with the model of the distillation column described by [J.-U Repke, 2006], for the study of the whole hybrid system pervaporation distillation. 

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