Reactive column

Note 7. To determine if the column is performing satisfactorily a standard sample, wood or a / -0-4 dimer, should be subjected perioidically to thioacidolysis and the results compared to those reported in the literature. Abnormally low yields are frequently indicative of an incompletely deactivated or reactivated column. It is specially important to perform this test when replacing an old column with a new one. 

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. 

The distilled HI (HI, I2, and H2O) vapor flows through a bed of catalysts at the top half of the reactive column, and HI within the vapor stream is decomposed into H2 and I2 gases at around 300°C. A condenser at the top of the reactive column condenses any unreacted HI, I2, and H2O and the liquid is reflux back down the column. 

Consequently, the HI at the bottom of the reactive column is I2 rich and is fed back to Section 1 as I2 supply for the Bunsen reaction. H2 is bled off the column top as a compressed gas for storage or use. The environment of HIx and high temperature and pressure required in the heat exchanger in the reactive distillation process make it potentially one of the most corrosive environments within the S-I cycle. 

When the conventional reactive distillation is combined with a water/alcohol separation, there are two extrema a small reactive column and high amount of energy or a large reactive column and a low amount of energy. 

By combining the node balance and a reactive column model as described in Section 8.3.1, an SMBR model can be created. Each section consists of one or more columns. The affiliation of the single columns and the boundary conditions are changed periodically. The flowsheet of the SMBR process is similar to that for the TMBR process given in Fig. 8.7. Please note that the origin of the axis system is located in the feed port. Internal flow rates are related to the external streams by balances of the inlet-and outlet nodes. A mass balance for each node is also necessary to calculate the concentration at the inlet and outlet of each single section. 

FIGURE 12.22 Computed composition profiles in an MTBE reactive column. Composition of the diluent, n-butane, may be obtained by difference. (H. E. Subawalla, 1997. Ph.D. dissertation, Univ. of Texas at Austin.)... 

For stability investigation, the reaction was continuously carried out in a reactive distillation reactor. The catalyst (0.71-1.0mm grain) was filled in the reactive column. Before reaction, N2 was introduced into the reactor and compressed to desired pressure. The products of both tower top and bottom were taken out each 12h for analysis. 15g catalysts were used for the distillation reaction with LHSV of 0.03h at 160 C and 0.6MPa. 

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