Aspen Plus models

The optimization of empirical correlations developed from the ASPEN-PLUS model yielded operating conditions which reduced the steam-to-slurry ratio by 33%, increased throughput by 20% while maintaining the solvent residual at the desired level. While very successful in this industrial application the approach is not without shortcomings. The main disadvantage is the inherent assumption that the data are normally distributed, which may or may not be valid. However, previous experience had shown the efficacy of the assumption in other similar situations. 

Index Entries Acid pretreatment carbonic acid ASPEN-Plus model alcohol fuels biomass. 

The equipment requirements were determined from the ASPEN-Plus model. The quantity and size of each piece of equipment was determined on the basis of the mass flow rate through the equipment. From the thickness calculations, it was found that three reactors were optimal to accommodate a mass flow rate of 83,333 dry kg/h. It was also found that the solids concentration of the pretreated material made it necessary to use more than one Pneumapress filter. 

Table 3 also includes the total power requirements for the pretreatment section of the NREL model (3). The cooling duty and the heating duty of different process units were also determined by the ASPEN-Plus model. These data were used to calculate the total cooling and heating duties for the carbonic acid pretreatment and finally the total energy cost of the pretreatment process. These results are summarized in Tables 4 and 5. 

The assistance of G. Colson (VUB) in the ASPEN PLUS modeling is gratefully acknowledged. This work is performed in the framework of the EC project JOR3-CT97-0184 and VLIET bis 970385. 

Unit Operation Aspen Plus Models UniSim Design Models... 

First, the chapter lists the possible unit operations in the Aspen Plus Model Library, because the process is a connected set of the units. Then an example process is illustrated that makes ammonia from nitrogen and hydrogen. You will be able to get both the mass balances and the energy balances for the process. With this information you can determine the size of most of the equipment needed, and hence its cost. You can also determine the operating cost for heating, cooling, compression, and other tasks. The process involves a... 

Aspen Tech. Aspen plus model of bioethanol from corn model. Burlington, MA Aspen Technology Inc. 2008. Available from http //www.aspentech.com. 

Aspen Plus modelling, continued, (a) Setting temperature estimates for the strippers (b) Writing the FORTRAN calculator block to determine the amount of makeup feeds (c) Defining the variables used in the calculator bloc (d) Defining a tear stream to control the initial guesses for the solvent flow rate, and thus the solvent loop size. 

Aspen Technology, Inc. Aspen plus model of the CO2 capture process by DEPG, corporate white paper. 2008. 

Table 6.3 Approach temperatures for Shell gasifier Aspen Plus model obtained according to data from Rich et at. [24].

Table 6.18 Approach temperatures for high-temperature Winkler (HTW) gasifier Aspen Plus model.

Aspen Technology, Inc. Aspen Plus, Aspen Custom Modeler, Dynaplus, Split, Advent, Adsim. Cambridge, MA (1998). 

The Aspen Properties implementation of the NRLT-SAC method is available as a template. aprbkp file to license holders of Aspen Properties or Aspen Plus release 12.1 or above, by contacting Aspen s support centre or regional sales offices. The template is distributed with an Excel interface to simplify the data regression process and is suitable for non-expert users of Aspen Properties. Numerous Excel templates are available for data analysis and design calculations, based on the NRTL-SAC model. 

To study different operating conditions in the pilot plant, a steady-state process simulator was used. Process simulators solve material- and energy-balance, but they do not generally integrate the equations of motion. The commercially-available program, Aspen Plus Tm, was used in this example. Other steady-state process simulators could be used as well. To describe the C02-solvent system, the predictive PSRK model [11,12], which was found suitable to treat this mixture, was applied. To obtain more reliable information, a model with parameters regressed from experimental data is required. 

As a consequence, corporations operating PUREX plants have been using sophisticated process simulation codes, including the PAREX code in France (45-47), SpeedUp (Aspen Plus) in the UK (48), and SIMPSEX code in India (49-51). Argonne Model for Universal Solvent Extraction (AMUSE) code in the United States was contrived not only for PUREX, but for UREX+ processes (52), which will be mentioned later. In Japan, similar efforts have also been made (53-55). 

The example CO2 capture process, shown in Figure 8 as an Aspen Plus EO model representation, is part of an ammonia plant. Designed to scrub CO2 from ammonia synthesis gas, it includes an absorber and two solution regeneration columns, one stripping the rich, C02 laden solution leaving the absorber to semilean concentration of absorbed CO2, and the other cleaning the solution even further to lean solution... 

Figure 8 Aspen Plus EO model for an MDEA/PZ C02 capture unit.

S 2] With the steady-state process simulator Aspen Plus , thermodynamic models for the sulfur-iodine cycle given in [132] are combined with chemistry models which describe the dissociation and precipitation reactions. 

The steps in setting up the Aspen Plus simulation are outlined below. The rigorous RCSTR model is used, which requires specifying reactions and kinetic parameters. An alternative, which is useful in some systems with reversible reactions, is the RGIBBS reactor module. Kinetic parameters are not required. Chemical equilibrium compositions are calculated for given feed and reactor temperature and pressure. If the forward and reverse reactions are known to be fast, so that the reactor effluent is at equilibrium conditions, the RGIBBS reactor provides a simple way to model a reactor. In Chapter 3 we will illustrate how this type of reactor can incorporate some approximate dynamics for developing control systems. 

Effect Of Number Of Lumps If the number of plotting points in Aspen Plus is set at 10 (the default), the resulting exit temperature from the reactors under steady-state conditions in Aspen Dynamics is 578 K. Remember that it should be 583 K from the rigorous integration of the ordinary differential equations describing the steady-state tubular reactor that are used in Aspen Plus. Changing the number of points to 20 produces an exit temperature of 580 K. Changing the number of points to 50 produces an exit temperature of 582 K, which is very close to the correct value. Therefore a 50-lump model should be used. 

Steady State from Dynamic Model The simulation is run out to a steady-state condition with the adjustable temperatures set to the same values as used in the steady-state Aspen Plus. These temperatures are the exit temperature from the first reactor (277°C) and the exit temperature from the heater HX3 (150°C). The power to the recycle... 

Several authors have already developed methodologies for the simulation of hybrid distillation-pervaporation processes. Short-cut methods were developed by Moganti et al. [95] and Stephan et al. [96]. Due to simplifications such as the use of constant relative volatility, one-phase sidestreams, perfect mixing on feed and permeate sides of the membrane, and simple membrane transport models, the results obtained should only be considered qualitative in nature. Verhoef et al. [97] used a quantitative approach for simulation, based on simplified calculations in Aspen Plus/Excel VBA. Hommerich and Rautenbach [98] describe the design and optimization of combined pervaporation-distillation processes, incorporating a user-written routine for pervaporation into the Aspen Plus simulation software. This is an improvement over most approaches with respect to accuracy, although the membrane model itself is still quite... 

Modeling of Carbonic Acid Pretreatment Process Using ASPEN-Plus ... 

---