Aspen Simulations

The adiabatic reactor is 20 m in length and 1 m in diameter. It is packed with 15,708 kg of catalyst with a heat capacity of 500 J kg-1 K-1. The process gas and the solid catalyst are assumed to be at the same temperature. The reactor inlet temperature is specified to be 

7 0idet pressure i Calculated Iron geomeby it correlation 

Hetran/Aerotran/IA Hetran/Aerotran Bro Geometry HotHcurves Cold Hcurves User Subroutines 

C Ptai e epecBte varies f1 . Power lew expression f Exchanger geometry 

The amount of bypassing Fby is determined by blending the 475 K stream coming from the FEHE with the 310 K bypass stream to achieve the 400 K reactor inlet temperature. The bypass flowrate is 0.0119 kmol/s, and the flow through the heat exchanger is 

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The referenced Siemens Westinghouse pnblication presented the cycle concept and overall performance valnes. Neither specific stream information nor assnmptions were presented. The stream data and assumptions presented here were developed by Parsons. The stream data were developed using an ASPEN simulation which yielded performance numbers in general agreement with the publication. 

Conclusions for Aspen Simulation of Different Types of Tubular Reactors... 

Luyben, W L. (2006) Distillation Design and Control Using Aspen Simulation (Wiley). 

With the methanol plants, the ASPEN steady state simulation was used to investigate the performance of the units with changing feedgas composition (H/C ratio and gas calorific valve) prior to startup. Since Synfuels processing fee for turning natural gas into gasoline is set by the yield obtained, the ASPEN simulator provides an important basis for fee determination under gas upset conditions. 

Distillation Synthesis). Add Aspen Plus library (that is. Aspen Simulation Workbook - V8.4) to VBA (Excel - VBA - Tools - References). Note that the user needs to install Aspen Plus on his/her computer before adding Aspen Plus library. In Aspen Plus, Variable Explorer is used to identify the VBA syntax for all variables in process streams or units (Aspen Plus - Tools - Variable Explorer)... 

In the operation of these systems, we usually want to condense as much as possible, so as to minimize compression costs of dealing with the vapor product. Therefore, the flow rate of cooling water should be maximized. This section demonstrates a realistic way to model a partial-condenser distillation system with both vapor and liquid distillate streams using Aspen simulation. 

Figure 8.19 shows the flowsheet. The column has 36 stages (Stage 1 is the reflux drum and Stage 36 is the base). Feed is introduced on Stage 17. The reflux-drum pressure is set at 25 psia and the reflux-drum temperature is 120 F. A tray pressure drop of 0.1 psi per stage is assumed. NRTL physical properties are used in the Aspen simulations. 

The total feed of 2300 lb mol/h of a binary mixture of 80 mol% methanol and 20 mol% water is split between the two columns to exactly balance the heat duties in high-pressure column condenser (QChp) and the low-pressure reboiler (QRlp)- Both columns produce 99.9 mol% methanol distillate streams and 99.9 mol% water bottoms streams. The required reflux ratios are 1.1 and 1.5 in the low- and high-pressure columns, respectively. Column diameters are 6.5 and 5.2 ft in the low- and high-pressure columns, respectively. Temperature profiles are given in Figure 8.27. The NRTL physical properties are used in the Aspen simulations. 

The distillation column smdied is based on a system that presents challenging design problems because of the severe nonlinearity of the phase equUibrium. The ternary system is water, acetic acid, and formic acid. The physical property package UNIQ-HOC is used in the Aspen simulations, which accounts for the dimerization of acetic acid in the vapor phase. 

In this chapter, we discuss both the steady-state design and the dynamic control of divided-wall columns. Aspen simulation tools are used. The industrially important ternary separation of benzene, toluene, and o-xylene (BTX) is used as anumerical example. The normal boiling points of these three components are 353, 385, and 419 K, respectively, so the separation is a fairly easy one with relative volatilities aa/ax/ax of about 1. I2.2I. The feed conditions are a flow rate of 3600 kmol/h, a composition of 30/30/40 mol% B/T/X, and a temperature of 358 K. Chao-Seader physical properties are used in the Aspen simulations. Product purities are 99mol%. All simulations use rigorous distillation column models in Aspen Plus. 

The standard basic RadFrac model in Aspen simulations does not accurately predict the rapid pressure changes during emergency situations because the default heat-exchanger models do not account for heat-exchanger dynamics (condenser and reboiler). Simulations can be developed that include external heat exchangers whose dynamics can be incorporated with the model of the column vessel. 

Distillation Design and Control Using Aspen Simulation... 

DISTILLATION DESIGN AND CONTROL USING ASPEN SIMULATION... 

Distillation design and control using Aspen simulation / William L Luyben. - 2nd ed. 

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