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FAQ: Solids Modeling in Aspen Plus

Frequently Asked Questions

Claus Reimers, Product Management, Aspen Technology, Inc. Dave Tremblay, Product Management, Aspen Technology, Inc. Ajay Lakshmanan, Product Management, Aspen Technology, Inc.Jennifer Dyment, Product Marketing, Aspen Technology, Inc.


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ContentsIntroduction...........................................................................................................................................................................................................1

Frequently Asked Questions Solids Modeling ..........................................................................................................................................1

Frequently Asked Questions Properties ....................................................................................................................................................4

Frequently Asked Questions Solid-Liquid and Gas-Solid Separation.................................................................................................5

Frequently Asked Questions Drying ...........................................................................................................................................................7

Frequently Asked Questions Formulation (Crystallization, Granulation, Agglomeration etc.)...................................................9

Frequently Asked Questions Particle Size Distribution Manipulation (Crushers, Classification, Compacting) ...................10

Frequently Asked Questions Circulating Fluidized Bed ........................................................................................................................11

Frequently Asked Questions Pneumatic Conveying.............................................................................................................................14

Additional Resources .......................................................................................................................................................................................16



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IntroductionAs contrasted to fluids, which are generally described by concentrated properties such as vapor fraction, composition,

temperature, and pressure, granular solids are described by distributed properties such as particle size distribution (PSD).

This adds an extra level of complexity to the description of the material and therefore the solids section of a production

process is often neglected or over simplified. Whether particles are being formed (e.g. crystallization, spray drying),

reduced in size (e.g. crushing/grinding), enlarged (e.g. granulation, agglomeration), have participated in reactions (e.g.

fluidized bed reactor, fixed bed reactor) or separated from a fluid stream (e.g. cyclones, filters, centrifuges), ignoring or

poorly modeling the solids processing steps may lead to lost opportunities, including cost reductions and quality

improvements.

With the introduction of aspenONE V8 in December 2012, Aspen Plus process simulation software provides the

capability to describe granular solids in detail and provides a comprehensive model library for the equipment associated

with solids processing steps. Aspen Technology continues to advance the solids modeling capability in Aspen Plus with

improvements in subsequent releases, such as activated economics and additional models. This document lists questions

that were submitted to AspenTech regarding the new solids capabilities in Aspen Plus, along with the answers to the

questions.

The intent of this document is to give you insight when exploring the solids modeling capabilities in Aspen Plus. Should

any other questions arise while reading this document, do not hesitate to contact AspenTechs Customer Support staff

[email protected] or visit the Aspen Support Center.

General Questions about Solids Modeling

1) Can we simulate a process that contains both a solid and a liquid section?Yes, Aspen Plus allows you to simulate processes with fluids and solids in one simulation environment. This ensures that

you use consistent physical properties for the fluid and the liquid section of those processes. Furthermore, you can use

integrated tools like Activated EDR or economics and use the computer-aided optimization features of Aspen Plus.

2) When optimizing, how does the software account for changes in size distributionthat may result from the process change?Aspen Plus contains a comprehensive model library for fluid and solid unit operations. The models, such as the screen and

crusher model, are rigorously predicting PSD as a function of operating conditions (such as power in the crusher).

3) Whose correlations are used in these models? Do you identify the referencessince there are many correlations in the literature that give different predictions?Each model provides a range of correlations that you can apply. We have made our best judgments to set defaults. All the

sources are fully documented in the help system and the PDF documentation files.

4) Can we simulate Solid Dynamics in Aspen Plus?We have not yet extended our solids models into Dynamics, however, there are some tricks you can use in Aspen Plus to

simulate batch equipment. We have published an example showing how to simulate a batch dryer batch dryer. This and

other examples can be found in aspenONE Exchange and on the Aspen Support Center.


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5) Is it mandatory to define PSD for characterizing solid stream?No, not in general. It depends on the units you want to simulate and on the answers the simulation should give you. In

simple cases, it may not be necessary to define a PSD or it might be sufficient to define a PSD with just one class.

6) Is Solids Modeling available in Aspen HYSYS?No, solids modeling is only available in Aspen Plus V8.0 and higher, as we are focused on chemicals. However, we

recognize there are many potential applications for this technology in the energy sector, for example handling oil sands.

Your best option is to use Aspen Plus to simulate the solids handling portion of these processes. There are ways to link

Aspen Plus to Aspen HYSYS (using Aspen Simulation Workbook) if you wanted to simulate downstream with Aspen

HYSYS.

7) Is there a comparison between simulation results and plant data?Aspen Plus includes a data regression feature that you can use to adjust model parameters to match measured plant data.

There is also a feature called Plant Data View which you can use to overlay plant data (from IP.21 tags) on top of a

process flow diagram to make it easy to compare model predictions to plant data.

8) What are the model convergence options?This question is a bit open-ended, so it is hard to give a precise answer. A handful of the new solids models require

iterative solutions. We have exposed and documented convergence parameters for these models.

9) Previous versions of Aspen Plus are limited on the entropy calculations. Does thisnew version allow for more accurate entropy calculations?Aspen Plus has a very flexible physical property system that allows you to change reference states and the calculation

routes and models (equations) used to calculate various properties. This includes the ability to plug in your own user

models or tabular data.

10) Do you need a separate license to use Solids Modeling in Aspen Plus?You dont need a special license. Aspen Plus V8 includes these new models without any additional costs.

11) Do you have an example of modeling energy from waste in the gasification process?We have a biomass gasifier model within Aspen Plus.

12) If a PSD changes due to reactions removing mass from solids, how would youmodel this?In version 8.4, the fluidized bed model allows consideration for chemical reactions. As part of this functionality, it is

possible to have changes of the PSD due to reactions. In addition to this, Aspen Plus allows you to track moisture

components in the solid sub stream. You can use this feature to account for loss of volatiles from the solid phase during

drying. For reactions, you can use user kinetics to calculate rates of change of solid components. You would also need to

send rates of change of PSD elements, which are weight fractions of the total solids. Another option is to use a shortcut

model to set PSD in the outlet stream or you can use an Aspen Custom Molder block inside Aspen Plus.



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13) Can we input our own models for unit operations?You have two options: (1) Using a user 2 or 3 model will allow you to write a model in a programming language such as

FORTRAN or C++ or (2) You can plug in an Aspen Custom Modeler block into Aspen Plus.

14) Is there comprehensive costing for Solids Modeling?Aspen Process Economic Analyzer includes several simple models for solids handling operations. In V8.2, we updated the

costing for the new unit operations introduced in V8.0 and with Activated Economics, it's easy to consider the costs

associated with different design configurations. However, in V8.0 the mapping of data from new unit operations is still

imperfect, so you may need to enter some additional data inside the Economic Analyzer.

15) With regards to handling non-conventional solids and gasifier models, whatimprovements have been made in Aspen Plus V8.0?The V8 improvements are focused on PSD characterization and unit operation modelsfor example better crusher and

mill models or a model for a fludizied bed reactor. We have not made significant changes in handling of non-conventional

components.

16) Can we work with batch processes?In Aspen Plus V8, the built-in solids models are steady-state models. There are ways to simulate a batch process using a

steady-state model by use of the so called clock-method. There is a batch dryer example that is available on the Aspen

Technology website and on aspenONE Exchange.

17) Are there plans to extend solids modeling to polymer processes, especially topolymer degassing and conveying?You could simulate degassing (drying) of solid polymer pellets, today. You would need to use an RSTOIC model to move

polymer from MIXED to CISOLID substream after a reactor and then specify PSD and initial moisture (solvent)

concentration in solids. For many polymer pelletizers, your PSD may be nearly uniform.

18) In Aspen Plus, it was possible to implement particle density distributions. Is thisstill possible in the version integrated with Aspen Plus?Aspen Plus V8 does not model particle size dependent properties, including density.

19) Is there a centralized database for custom models which are supported by Aspenusers? Where can I find this database? There is list of 17+ demos on the Aspen Plus Solids Modeling webpage that is available to all users. These demos include

Aspen Plus models and instructional slide-show guides. The models are also available on the Aspen Support Center and

on aspenONE Exchange. Users can add custom models to aspenONE Exchange for other users to see.


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20) A clay-like solid would behave much differently than a solid salt. How do youdescribe these property differences so that crushers and compactors will give goodresults?The stickiness of particles is very difficult to describe. Our models have fitting parameters that can be adjusted to match

plant performance. For example, the screen model allows you to adjust the separation curve (by changing the value for the

parameter offset fines) to consider that fine particles might stick to coarser ones and therefore go to the coarse outlet of

the screen. In addition to this, you could also use Aspen Custom modeler to write your own model and use it in Aspen Plus.

Properties Questions

1) What is the recommended thermodynamic package when feed streams are insolid phase (coal, TiO2, other metal oxides) and in gas phase (chlorine, oxygen)?Most of our thermodynamic option sets allow for solids. The models use special routes for calculating enthalpy and

density of non-conventional components, such as coal. For conventional solids, you may need to enter DHSFORM (solid

heat of formation). The databases in Aspen Plus are a bit sparse for solids heat of formation data. Components like TiO2

are treated as conventional solids.

2) Is there a difference on physical properties in version V8.0 and V8.2?We update the physical property databases with each major release. Version 8.2 includes the new database PURE28

based on the DIPPR January 2012 public database. This includes 7 new components and updates for other components

and one additional component to the solids database. A new surface tension model (Onsager-Samara) was also added.

3) Can moisture modeling apply to hydrocarbon liquids?We can identify any conventional components as moisture components in Aspen Plus. This can include multiple

solvents or hydrocarbons.

4) Are the physical properties of solid substances, such as FeO etc. updated?Aspen Plus has property models for conventional inert solids (like iron oxide) and non-conventional solids (such as coal or

biomass). We update our databases quarterly as new data become available from NIST. In V8.0, we also introduced a

number of new prop-set properties to characterize particle size distributions, for example D10...D90, number, area, and

volumeaverage diameter, mean diameter (D50), volume specific surface area, Sauter diameter, etc. In V8.2, we have

further extended this list of new prop-set properties.

5) How does Aspen Plus V8 handle properties of standard chemicals and solids instreams?Aspen Plus handles vapor-liquid-solid phase equilibrium for soluble solids (salts) using the Chemistry feature. Non-

soluble solids are addressed using property methods for solidsfor example heat capacity of a solid is from CPSDIP

(DIPPR heat capacity equation for solids). Aspen Plus has very rich and rigorous property methods for solids.



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6) Is there a tutorial on how to create conventional and non-conventional solids?The new computerbased training module for solids includes this information. You can get to it from the Get Started

ribbon tab, by clicking the "Training" link.

7) Can the models handle multidimensional PSDs?Aspen Plus V8 can handle different particle types. Each particle type is described by its composition and particle size

distribution. Furthermore, it is possible to consider different moisture components for the different particle types.

8) Are the solids property models implemented in Aspen Properties?Several solids properties are included in Aspen Properties.

Solid-Liquid and Gas-Solid Separation Questions

1) Can I use solids modeling for continuous thickeners/clarifiers?The current model library doesn't contain any specific model for thickeners/clarifyiers. As a workaround, you could use a

SEP block to separate solids and liquid without having any classification effect. Another workaround could be to use the

classifier block. This would allow you to specify the classification (based on particle size or particle settling velocity) and

the outlet moisture of the sludge.

2) How does the gas-solid cyclone module work? Is it a simple splitter or does itcalculate separation efficiency & pressure drop based on a geometry input? Does thecyclone module allow specification of a targeted efficiency and calculate geometry?We have rigorous cyclone models that predict the separation based on particle size, density (settling velocity of the

particles), and geometry of the cyclone. You can specify geometry to rate existing equipment, or set a target separation or

maximum allowed pressure drop and automatically size the cyclones.

3) Can the cyclone models handle liquid-solid systems?We have rigorous hydro-cyclone models that predict the separation based on particle size, density (settling velocity of the

particles), and geometry of the cyclone. Similar to the gas cyclone model, you can specify geometry to rate existing

equipment, or set a target separation or maximum allowed pressure drop and automatically size the cyclones.

4) Can washing be modeled in a centrifuge?Aspen Plus V8 has a solids wash model in Aspen Plus. You could try using that in combination with the centrifuge.

5) Can the cyclone models handle high solid streams? e.g. 50 wt. % solid.Yes. Beside the separation in the inner vortex, the modelaccording to Muschelknautzconsiders strand separation once

the inlet loading is above the critical loading. The models also have tuning parameters so you can tweak the model to fit

real plant performance.


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6) How can I model a pressure filter to separate solids from slurry?The filter model can simulate a wide range of industrial filters including, for example, rotary filters. You would apply the

appropriate model that best matches your actual equipment.

7) Any advice to simulate nanoparticles separation from water?It may be best to use Aspen Custom Modeler since nanoparticles need special treatment.

8) Is information available regarding the models used for separations, esp.centrifuges and hydrocyclones?The models are fully documented through the online help inside the software. This includes the underlying references so

you can go back to original sources. We also have a detailed computer-based training module for solids modeling.

9) Does the belt filter allow washing of the filter cake?Yes, the belt filter allows washing of the filter cake. The model allows the user to define a fraction of the belt area used for

washing. The washing can be done in multiple stages and it can be done in co-current or counter-current mode. The figure

below shows what the different modes look like.

Counter-current with 3 stages wash inlet

Stage 1 Stage 2 Stage 3

Stage 1 Stage 2 Stage 3

Counter-current with 3 stages

wash inlet

cake inlet

cake inlet



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10) Does the filtration zone in the belt filter also consider deliquoring of the filtercake?In the simulation mode, the user defines the fraction of the belt area that is used for filtration, washing (if considered), and

deliquoring. The model determines the area needed for filtration and if this area is smaller than the user-defined area for

filtration, the model will consider the remaining area as area for deliquioring of the filter cake. The same is valid for the

washing section of the filter.

Drying Questions

1) What are the geometrical characteristics of the convective dryer model? The convective dryer model allows you to consider co-current, counter-current, or cross flow of gas and solids. In the case

of cross flow, the solids can be in plug flow (e.g. belt dryer) or ideally mixed (e.g. fluidized bed dryer). This allows you to

use the model to simulate many types of equipment (e.g. flash dryer, belt dryer, fluidized bed dryer, mill dryer, etc.). We

have published different examples that show you how to model and optimize different dryer types. The examples are

available via aspenONE Exchange or by going to the Aspen Support Center.

2) Does Aspen Plus handle rotary dryers?At a conceptual level, you can model all types of dryers. If you want a very high fidelity model that accounts for heat

transfer from the rotating disks, then your best option is to use Aspen Custom Modeler (ACM), which lets you write your

own equation. As an example, we have developed rigorous models of BEPEX rotating dryers for polyester pellets using

ACM. Such a model could be plugged back into Aspen Plus.

3) Can Aspen Plus model a shell-heated rotary kiln dryer with counter-current airflow, including fine particle entrainment out of the dryer?We dont have a detailed shell-heated rotary kiln dryer. You could use the shortcut dryer, along with a classifier and a

heat exchanger to model a rotary kiln dryer with counter-current air flow, including particle entrainment. The convective

dryer model in Aspen Plus can be used to model dryers that are heated by a drying agent (indirect heating).

4) Are these conveying models appropriate for modeling flash drying or is anotherdrying model more appropriate?The conveying model itself cannot model the dryer in a flash dryer, only the pressure drop. We have published a flash

dryer example that shows how a convective dryer and a pipe model can be used to describe a flash dryer. The example is

available via aspenONE Exchange or the Aspen Support Center.

5) What type of solids can be modeled using these new drying models in V8? Canwe use coal or non-conventional solids?Yes, you can model conventional and non-conventional solids.


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6) Does Aspen Plus have a database of drying curves?No, Aspen Plus does not contain a database of drying curves, but if you have measured data or you know the outlet

moisture for a specific application, you can back calculate the curves.

7) What is the impact of increased air rate on the equipment volume?The dryer model itself has no design, but it does have a rating mode. This means if you increase the drying agent flow rate,

you will see a reduced solids moisture content and (depending on the drying period) an increased solids temperature at

the dryers outlet.

8) Is it possible to model pressure drops of the dryers?The dryer model itself does not calculate the pressure drop, but there are ways to consider the pressure drop. With a flash

dryer, you may use a combination of dryer and pipe to account for the pressure drop. We have published an example that

shows how to model that kind of dryer and at the same time consider the pressure drop. The model is available via

aspenONE Exchange or the Aspen Support Center. Another way is to use a calculator block to calculate the pressure drop

of the dryer and then set the determined outlet pressure in the outlet streams of the dryer by use of a valve.

9) Can flash, ring, or spray dryers, for example, be modeled with upward rather thanlateral flow?You can model a ring or a flash dryer by using a combination of drying and pipe blocks. We have published an example for

a flash dryer. The example is available via aspenONE Exchange or the Aspen Support Center. In this example we have

upward flow.

10) How do I use a drying kinetics model based on partial derivatives?The current version of the convective drying model does not allow you to include user defined drying kinetics. The drying

kinetic is described by a model for the mass and heat transfer (e.g. user defines the Sherwood number) and a

corresponding normalized drying curve. You can use your model to calibrate the build in model or implement your drying

kinetic model in the form of a user block. For doing this you have two options: (1) A user 2 or user 3 model allows you to

write a model in a programming language such as FORTRAN or C++ or (2) You can import an Aspen Custom Modeler

block into Aspen Plus.

11) Can we add customized solubility models to account for loss of raw materialsdissolved within exiting solids?The drying model lets you specify a limiting solubility (the point beyond which you cannot further remove volatiles

dissolved in the solids). You could use a calculator block to adjust that parameter (for example to introduce temperature

dependency).



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12) If one has the reaction kinetics, is it possible to model a calciner involvingchemical reactions and drying, simultaneously?The current dryer model does not allow you to consider chemical reactions inside the dryer. What you can do is use the

dryer model to dry the surface moisture and afterwards a reactor (e.g. RGIBBS, RCSTR, fluidized bed (v8.4)) to model the

calcination.

13) Is it possible to model a fluidized bed dryer with two zones and also with a topfeed?We use the hierarchy feature in Aspen Plus to model complex equipment with multiple zones or stages. We have just

published an example for multistage dryer units as an example, which can be found via the aspenONE Exchange or the

Aspen Support Center.

Formulation Questions

1) How can I check possible solids entrainment in a vent stream that is leaving froma crystallizer?Aspen Plus V8 includes a classifier model which can predict entrainment based on terminal velocity (a function of particle

size). You can put the classifier block downstream of the crystallizer block to represent equipment behavior.

2) Is there a model for melt crystallization, for example, Paraxylene. Aspen Plus includes a rigorous MSPR crystallizer model.

3) How can the melting of solid material be displayed within Aspen Plus models?The crystallizer model can also simulate dissolving of solids. Another option is to use a reactor model like RSTOIC to move

material from CISOLID to MIXED (for example TA(s) >TA(l) can be treated as a reaction). You can specify conversion

or use kinetics.

4) Is it possible to model a batch crystallizer?Aspen Plus V8 does not have a model of batch crystallizer. There are some tricks to use Aspen Plus to simulate batch

equipment. We have published an example showing how to simulate a batch dryer as an example. The example is

available via aspenONE Exchange or the Aspen Support Center. If that does not work for you, you could use Process

Tools, Aspen Batch Modeler, or Aspen Custom Modeler.

5) What is the difference of the crystallizer between Aspen Plus V7 and V8.0?A difference includes the additional options to specify outlet PSD using a distribution function.

6) Is it possible to use Ammonium Nitrate to granulate?Yes, as along as long as you have the necessary property data (heat capacity, density, PSD etc.).


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7) Is it possible to model pressure drops of the granulators?The granulator itself does not calculate the pressure drop. A workaround could be to use a calculator block to calculate

the pressure drop of the granulator and then set the determined outlet pressure in the outlet streams of the granulator by

use of a valve.

8) Are there models for screw type granulators?Yes, you can model screw type granulators. The granulator block allows you to model granulation (growth of particles due

to deposition of solid material on primary particles) and agglomeration (aggregation of two or more primary particles).

For both growth mechanisms, the granulator block allows you to consider drum, fluidized bed, or plate type equipment.

9) Is there any chance of specifying the properties of the binder in the models?No, this is not possible. The binder properties (e.g. density, viscosity, etc.) are defined by the material that enters the

binder port of the agglomerator. If you want to change properties you have to do this in the properties environment.

10) Can the current models be modified for a high shear granulation process and ifso, what parameters can be changed?The current implementation of the granulator/agglomerator allows you to model high shear granulators/agglomerators.

The block allows you to model pure granulation (growth of particles due to deposition of solid material on primary

particles) or pure agglomeration (aggregation of two or more primary particles). Depending on the selected growth

mechanism, different parameters can be changed. In case of pure granulation you can define cumulative mass in the

vessel, and if you assume the material to be ideally mixed or in plug flow. In addition to this, you can define if the growth

rate is surface, volume, or diameter proportional. There is also a factor that allows you to adjust the determined growth

rate to fit the model to measured data.

In case of agglomeration, you have to define the cumulative mass in the vessel and the type of size/dependent kernel (e.g.

constant, sum, product, EKE, etc.) you want to use. In addition to this, you can either define the value of the pre-kernel or

you can use the flux number approach to determine its value.

Particle Size Distribution Manipulation Questions

1) How can I check possible solids entrainment in a vent stream that is leaving froma crystallizer?Aspen Plus V8 includes a classifier model which can predict entrainment based on terminal velocity (a function of particle

size). You can put the classifier block downstream of the crystallizer block to represent equipment behavior.

2) Can you model velocity dependent particle size distribution in tanks and silos?You could try to use the classifier model that models solid-liquid separation based on terminal velocity.



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3) What determines the effect of the Grinder Power on the PSD? Is this estimatedby Aspen Plus or set by the user?The crusher model includes methods to calculate the influence of crusher power on the PSD. The correlations in the

model can be tuned to match equipment performance, and there are also parameters (e.g. Bond Index, Hardgrove Index)

related to hardness of different materials.

Fluidized Bed Questions

1) Is the FBR model available in Aspen Plus V7.3?The fluidized bed model is available in V8.2 and higher only. In version 8.4, the fluidized bed model also allows to consider

chemical reactions within the fluidized bed, so that you can simulate fluidized bed reactors. Furthermore, the model allows

you to consider the influence of the reaction on the particle size of the bed material.

2) A heat exchanger can be incorporated into the fluidized bed for heating/coolingpurposes. Can I use a liquid inlet to a fluidized bed for evaporative cooling?If you add a liquid stream along with solids in the solids feed stream, the system will correctly account for evaporative cooling.

3) Is it possible to simulate a fluidized bed reactor?The fluidized bed model in version 8.2 allows you to include equilibrium reactions via Chemistrythis allows you to model

(for example) fast vapor phase reactions involving a fluidized catalyst. The fluidized bed model in version 8.4 allows, in

addition to this, to consider kinetic controlled reactions. The model also considers the impact of the chemical reactions

(by changing volume of the gas phase or by changing the particle size of the particles in the bed) on the fluid-mechanics.

We have published an example showing how to simulate a fluidized bed reactor. The example is available via aspenONE

Exchange or the Aspen Support Center.

4) Is three-phase fluidized bed (slurry Bed) modeling going to be considered in thesimulation in the future? We dont have immediate plans for slurry (solid/liquid/vapor) fluidized beds, but we have not ruled it out indefinitely.

5) Can the model calculate the bubble size, dense bed height, and solid voidageacross the bed for the fluidized bed? How reliable are these calculations if there is any?The fluidized bed model calculates all these attributes. It displays the bed density and other factors as a function of axial

position (elevation) in the bed. We cant really comment on the accuracywe use published equations.

6) Is it possible to connect a CSTR model containing the reaction and its kinetics toa Fluidized bed reactor in a series to get the results of the fluidization?For version 8.2, this might be a good way to calculate the reaction heat (in the CSTR) and pass that (or the calculated

temperature) to the fluidized bed model to simulate the hydrodynamics. The fluidized bed model in version 8.4 allows you

to consider chemical reactions within the vessel, so that this workaround is no longer necessary. The model also considers


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the impact of the chemical reactions (by changing volume of the gas phase or by changing the particle size of the particles

in the bed) on the fluid-mechanics. We have published an example showing how to simulate a fluidized bed reactor,


7) Can Aspen Custom Modeler be used to accomplish fluidized bed unit operationswith the reaction kinetics-based processes?Aspen Custom Modeler allows you to write your own conservation equations, as well as equations for heat transfer and

fluidization. The stream ports are already defined to include streams with particle size distributions. The models you

develop in ACM can be plugged back into Aspen Plus. With version V8.4, we enhanced the fluidized bed model to

consider chemical reactions. We have published an example showing how to simulate a fluidized bed reactor, available via

aspenONE Exchange or the Aspen Support Center.

8) Can we specify a cylinder at lower portion and a partial sphere on the top, like agas phase reactor?The fluidized bed model allows you to define diameter (which can be apparent diameter) as a function of vertical position.

This allows you to address multi-diameter geometry. We dont have a direct option for spherical head.

9) Can we model the biomass as an input to the fluidized bed?Biomass is treated as a non-conventional solid component in Aspen Plus. We have special thermodynamic models for

non-conventionals that use atomic analysis (e.g., %C, H, O...). The analysis is defined through component attributes

ULTANAL, PROXANAL, etc. To date, we usually use RGIBBS to model the gasifies because it accounts for the properties

correctly.

10) In Aspen Plus, we can use the sensitivity analysis to improve the model, but canwe use a sensitivity analysis to specify the best particle size to put in a fluidized bedfor the specific case of the biomass?

The PSD and other solid properties are

accessible for variable accessing (DEFINE and

VARY keywords). This means you can use

sensitivity, calculator, data-fit, and other tools

in Aspen Plus to fit/study/optimize the model.

A good way to change the PSD of a feed

stream might be to use the granulator block

and choose the specify outlet PSD option, as

shown in the screenshot below. Then select

the option to define the outlet PSD by use of a

distribution function. If you then choose, for

example, RRSB as a distribution function, you

can define the PSD by d63 and the dispersion

n, therefore you you only have to deal with two

parameters that need to be changed.



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11) Is your Fluidized bed model able to simulate particle attrition inside the bed? Ifnot, can you suggest a way to simulate it indirectly?The current version of the fluidized bed does not consider breakage or attrition of the particles. A workaround to consider

attrition could be to split a fraction of the solids outlet stream, use a crusher to change the PSD (tabular data, since

attrition cannot be modeled with the current crusher models) of that stream, and recycle it back to the vessel. The split

factor can be determined by use of a calculator block that evaluates a correlation for the description of the attrition rate.

12) Could I use the FB reactor model for simulating Spouted Bed reactors?The current implementation is developed with bubbling and circulating fluidized beds in mind. For the fluid-mechanics of

the bottom zone, we use a model according to Werther and Wein. For the freeboard, we use a model according to Kunii

and Levenspiel. All the sources are fully documented in the help system and the PDF documentation files. Please review

the equations and decide on your own if this model is applicable to your specific application.

13) Is it possible model clogging in a heat exchanger or other equipment located aftera fluidized bed?The rigorous shell & tube exchanger model has an option to specify the number of plugged tubes, but this is not predicted.

14) Is it possible to use it for gas phase polymer production?We have not yet extended the model to work with polymerization reaction kinetics. Today, most of our customers use a

CSTR to simulate UNIPOL type reactors. Longer term, we see benefits to use the more rigorous fluidized bed reactor model.

15) Is there a way to account for size change within the bed either due to attrition orchemical reaction?The current version of the fluidized bed does not allow for particle size change within the vessel due to attrition or

breakage. In version 8.4, it is possible to consider for particle size change within the vessel due to chemical reactions.

16) Does a bubbling fluidized bed include turbulent regime?The current implementation is developed with having bubbling and circulating fluidized beds in mind. For the fluid-

mechanics of the bottom zone, we use a model according to Werther and Wein. All the sources are fully documented in

the help system and the PDF documentation files. Please review the equations and decide on your own if this model is

applicable to your specific application.

17) Will the fluidized bed model handle all regimes from bubbling bed, circulatingfluidized bed, through transport reactors?The current model is based on a one-dimensional model for the fluid-mechanics of a fluidized bed. For the fluid-

mechanics of the bottom zone, we use a model according to Werther and Wein. The model allows a bubbling, as well as a

circulating fluidized bed.


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18) Is there any way to estimate the number of holes on a perforated plate for thefluidized bed?A rule of thumb is that the minimum pressure drop of the gas distributor should be at least 30% of the bed pressure drop

to have an even gas distribution. The current version of the fluidized bed model allows considering either bubble caps or

perforated plates as gas distributors. The pressure drop for these distributors is determined based on the distributor

geometry and the current fluidization gas flow rate. In order to estimate the number of holes in a perforated plate you can

set an initial guess for the number of holes in the perforated plate and then run the simulation. As a result of this

calculation you will get the distributor and the bed pressure drop. If the distributor pressure drop is too low (



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6) How is pressure drop, due to fittings such as elbows and diverter valves, handled?It is handled with equivalent lengths.

7) If I mix two solid streams and send them through a conveyer, can I model thesolid-solid heat exchanger? In the current implementation of the model, this is not possible. The model assumes that the inlet stream is at

thermodynamic equilibrium. If the different sub-streams at the inlet have different temperatures, the model will perform

an isenthalpic/isobaric flash calculation and the stream will have the mixture temperature.

8) Can Aspen perform step pipe calculations if we specify a total pipe length?No, the model calculates the pressure drop for a given geometry and given operating conditions.

9) Does Aspen Plus have built-in pipe friction factors for shotpeened as well assmooth bore conveying pipe?No, there are no built-in friction factors for the conveying models.

10) Does pneumatic conveying include vertical downward pipe orientation?Yes, you can define pipe length and pipe rise or angle.

11) Are these conveying models appropriate for modeling flash drying or is anotherdrying model more appropriate?The conveying model itself cannot model the dryer in a flash dryer, but the pressure drop can. We have published a flash

dryer example that shows how a convective dryer and a pipe model can be used to describe a flash dryer. The example is


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About AspenTech

AspenTech is a leading supplier of software that optimizes process manufacturingfor energy, chemicals,

engineering and construction, and other industries that manufacture and produce products from a

chemical process. With integrated aspenONE solutions, process manufacturers can implement best

practices for optimizing their engineering, manufacturing, and supply chain operations. As a result,

AspenTech customers are better able to increase capacity, improve margins, reduce costs, and become

more energy efficient. To see how the worlds leading process manufacturers rely on AspenTech to

achieve their operational excellence goals, visit www.aspentech.com.

Additional ResourcesPublic Website:

http://www.aspentech.com/products/solids-aspen-plus.aspx

http://www.aspentech.com/products/aspen-plus.aspx

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http://www.aspentech.com/products/aspen-online-training

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