Aspen main fractionator

Figure 4.89 Aspen HYSYS configuration for the main fractionator.

Figure 4.89 shows the unit and stream configuration for the main fractionator in Aspen HYSYS. To build the main fractionator, we follow the same procedure as a cmde distillation tower described in Chapter 2 ... 

The standard inside-out algorithm can solve the main fractionator with ease when we follow the procedure mentioned above. However, flat distillation cuts or very tight specifications may not allow the standard method to converge robustly. We suggest the following changes to improve convergence behavior in Aspen HYSYS ... 

Woods contain a number of acyl (mainly acetyl) groups, and it is probable that these are associated with the xylan components of the hemicellulose fraction. Evidence for the original esterification of aspen-wood xylan comes from the observation that the isolated xylan (obtained by alkaline extraction) is readily cleaved by periodate, whereas only a small proportion of the D-xylose residues in the wood itself are oxidized under similar conditions.66 Hemicelluloses still containing acyl groups may be extracted from wood holocelluloses by means of dimethyl sulfoxide, and further quantities... 

Several of the commercial simulation programs offer preconfigured complex column rigorous models for petroleum fractionation. These models include charge heaters, several side strippers, and one or two pump-around loops. These fractionation column models can be used to model refinery distillation operations such as crude oil distillation, vacuum distillation of atmospheric residue oil, fluidized catalytic cracking (FCC) process main columns, and hydrocracker or coker main columns. Aspen Plus also has a shortcut fractionation model, SCFrac, which can be used to configure fractionation columns in the same way that shortcut distillation models are used to initialize multicomponent rigorous distillation models. 

The relevant models for the reactive distillation column and peripherals have been developed and implemented into the simulation environment ASPEN Custom Modeler . Simulations of the heterogeneously catalysed synthesis of TAME have included 11 components. The species and the boiling points at the operating pressure of 4 bar are listed in Table 1. The key components of the inert fractions of the feed have been used to represent the hydrocarbon fractions (see Table 1). VLE is described by UNIQUAC model, with the Redlich-Kwong equation of state. In simulations, four reactions are considered the main reactions (l)-(3) and the formation of dimethyl ether (7). 

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