Dynamic model toolbox for a continuous Dual Vessel Hydraulic EMCC digester, using Matlab® v6.1.

© IETek, February 2002.

Contact : Ferhan Kayihan, (253) 925-2179, fkayihan@ietek.net, http://ietek.net.


1.  Fundamental dynamic plug flow model of dual vessel hydraulic EMCC digester. Complex unit operation with moving packed bed of polydispersed porous chips reacting with diffused entrapped liquor while moving through co-current and counter-current liquor streams. High dimensional nonlinear realistic dynamic model with great potential to be used as a reference toolbox for a range of systems R&D work.

2.  Chip movement through the vessels as individual discrete plugs (about 1000 plugs in the vessels at any given time). Each chip plug carries its own physical properties and reaction parameters. The model is naturally suited for specie swing (transition) management and control.

3.  Five different chip dimensions represent chip size variability with interchip density (composition) gradients as part of the model.

4.  Dynamic chip column compaction, one of the main sources of nonlinear behavior.

5.  Cinematic numerical approach to facilitate the solution of ~130,000 ODEs at a speed approximately 200 times faster than real time on a 1.7GHz PC; e.g., 5 minutes of real time in about 1.5 seconds including update of animation graphics.

6.  Rich animated GUI for user interactions and process visualization.

7.  Although the toolbox code represents hypothetical design and operating conditions, recently IETek has successfully customized the model to simulate an operating commercial unit.



The demonstration software retains most but not all of the capabilities available in the full version of the software. In particular, the demo program is a compiled executable code with no user m-file accessible input/output information. All of the user interactions with the Demo code are through a GUI. The Demo software highlights the essential features of the model and hopefully provides sufficient information to a potential user to assess the value of the model for academic research and development. Demo code consists of the following components: (1) rundvhemcc2002, the executable compiled code (~2.1 megs); (2) FigureMenuBar and FigureToolBar, two Matlab figure files to provide figure generating support to the executable code (~100 kb combined); and (3) Data01, Matlab data file (mat) containing the initial states for the model (~10 megs). Although the demo code is in compiled form, the user still needs a valid Matlab license to run the model. Under special arrangements IETek may provide a true standalone version of the demo and the full code that would not require the presence of Matlab software. Contact IETek (fkayihan@ietek.net) to receive a free 30-day examination copy of the demo code. Recommended environment for the code are: (a) ability to receive ~10 meg through e-mail, (b) Matlab v6.1, (c) 252+ meg ram, and (d) XGA (1024x768) or better display.


1.  Install all 4 files into a project folder as a Matlab application. Make sure that Matlab path has access to this folder. If the same folder has other Matlab applications, then place the two figure files in a subfolder called Bin to make sure that they do not interfere with other m-file applications. Create a backup copy of the data file Data01 under a different name so that you can always recover the original version. The code always expects the data file to be under the default name Data01.

2.  Start the model by typing !rundvhemcc2002 at the Matlab prompt >> in the Command Window. The ! mark identifies the code as compiled rather than the usual m-file.

3.  Use the START button on the GUI to initiate a simulation session. Use the manual interaction “triangles” to move process inputs up or down. Explore other options of interacting with the model as instructed on the GUI. Experiment with the two different choices for level control (through OPTIONS button) and run through a demo of specie swing from softwood to hardwood. Note that some trend graphs have multiple display options and each dynamic trend or profile can be captured as a snapshot Matlab figure with a time stamp. Try saving the states of a simulation (after a PAUSE or at the end) and then restarting from that condition again. Note that saving the present states as Data01 will overwrite the previous data file, and that the default starting file name is Data01. Take advantage of the Data02 file name that is offered as a safe intermediate storage location.

4.  Chip level controls and specie swing (transition) feedforward control policies are very rudimentary and provided for the sole purpose of exercising/displaying model capabilities.

5.  Contact IETek for questions, suggestions and bug reports, and to purchase the full code.



In the full version of the software the user has complete m-file access to model inputs and outputs at every time increment (5min) with the option of providing custom control and process management policies. Initially the model starts operating from nominal conditions as provided, but then can be taken to any other operating state desired by the user. The model has the capability of “warm” starting from any feasible operating state. This makes it possible for the user to either terminate the model at any time and save the current results as the initial conditions for a subsequent run, or pause the model to make manual changes in the user input m-file (e.g. change controller tuning) before continuing with the run. GUI provides animated visualization of the process conditions, live manual input/interaction capabilities and graphical snapshot capturing of operating status. User starts the code execution through an open m-file called rundvhemcc2002 which has defined option parameters selecting the way the user wants to the model. For example, GUI may or may not be activated and the specific m-file name for user decisions (Options.InputFileName) can be specified for single or multiple applications. Within Options.InputFileName (default inputspecifications_dvhemcc02 is provided) the user has complete freedom to update decisions on process control and feed (chip and liquor) properties. Alternatively, part or all of the process input decisions can be made “live” from the animated GUI as demonstrated by the Demo Code. For convenience, a separate file called outputprocessing_dvhemcc02 is preserved for processing model outputs at each time increment. All pertinent model variables and profiles are updated and available to the user as a snapshot at current time as well as 24 hr history files at 5 minute frequency. The specifics of the variable names and array sizes are defined in a user m-file called inputoutputdefs_dvhemcc02. All other model computations and GUI management tasks are done behind the curtain through pre-parsed Matlab p-files. The model works for a fixed geometry hypothetical EMCC dual vessel design with a wide range of operating capability. Both softwood and hardwood chip chemical and physical properties are made available and nominal operating starting data files for each specie are provided with the code. The full version of the code is licensed to an organization, specific to one Matlab license (Matlab license number required at the time of order), with a one-time fee of US$1,000 for internal R&D use only. IETek will provide 12-month upgrade and bug fix service free of charge. Other license arrangements and custom modification/development options can be provided on a case-by-case basis. Please contact IETek if you have questions or would like to place an order.



Modeling and numerical procedures are based on the traditional fundamental conservation laws combined with best-known data and information pertaining to the process. Every effort is made to provide error free coding of the model, though it is entirely possible that some bugs may still be hiding undetected in the details of the software. Please notify IETek of any software bug discovered. A few words of caution here: (a) the model represents a nonlinear process and you may easily perceive an unexpected dynamic behavior as a possible bug, but the chances are there is a physical/chemical reason for it; (b) this is a plug flow reactor model with discretised numerical approximations, therefore almost no dynamic response is smooth as it is usually with CSTR models, thus sharp local variations are natural in this model. Therefore, plan for smooth and judicious control actions as it is actually practiced with the real process. Some operating restrictions are imposed on model parameters and flowrates in an attempt to secure the computational integrity of the model. Specific limits are enumerated in the user m-file "inputspecifications_dvhemcc01" (available in full licensed version, not available as part of the 30-day free Demo version).



Although every effort is made to provide an error-free dynamic model the code presented here is not guaranteed to be error free or an absolute representation of any real digester. The user assumes all responsibilities for conclusions and designs reached as a result of exercising this model. IETek will not be liable to the user for any special, consequential, direct or indirect damages, including any lost profits, lost data or lost staff time arising from the use or inability to use the model code.



 For additional simulation results see the Advanced Digester Model section.










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