VTT BALAS – A steady state simulation package for chemical processes
VTT BALAS operates under all newest Windows operating systems utilising commonly known applications for model development and processing of results: Microsoft Visio for flowsheet development and Excel for result data processing. Separate application for simulation model and model run parameterisation is also used. Typical applications of VTT BALAS are:
- Calculation of mass and energy balances
- Analysis of heat integration and heat recovery
- "What if" analysis
- Process optimization
- Development of unit operation modules
Unit operations and model libraries
VTT BALAS has an extensive selection of unit operation modules. These unit operation modules enable the user to model the whole paper mill including mechanical pulping, heat recovery, utilities and wastewater treatment. A selection of ready-made model processes, which are listed below, are supplied with the software:
These model processes have been parameterised using typical industrial values. These processes can be copied to any process model. Using these processes as a basis for modelling one’s own processes can speed up the modelling task considerably.
- Paper mill including paper machine (uncoated), debarking plant, effluent treatment plant, water preparation plant, CHP power plant
- Detailed paper drying
- Bioethanol production
- CO2 separation
Process behaviour with pre-defined model parameters can be calculated using simulation mode. Two optional solvers are available for simulation calculations.
Design (rating) calculation mode is used when unit model parameters are not known or pre-defined but should be based on known output values, e.g. mill measurements. In design mode, any number of output values (e.g. temperatures) are fixed to their known value and an equivalent number of parameters (e.g. heat transfer area) are set free for solver to identify simultaneously with the rest of the process.
VTT BALAS has a solver for non-linear optimisation problems. For these problems an objective function (the function to be minimised or maximised), equality (design) and inequality constraints, and free variables (design parameters) can be defined. Typical application of this feature is parameter optimisation.
A solver has been added to handle exclusively parameter estimation problems. In this mode, sets of measured data (e.g. contaminant concentrations) in various parts of the process can be supplied. The free variables and constraints are given in similar fashion as in optimisation mode. The solver manipulates the variables to obtain the best possible fit between the measured data and simulated values using a least-square type of algorithm. A typical application of this feature is to estimate sources and sinks for dissolved and colloidal substances in processes.
VTT BALAS is equipped with a link to Microsoft Excel. This link allows the user to access and manipulate all model parameters and stream data and run the models within Excel. Excel tools can then be used for visualisation and analysis of calculated data (Figure 1).
Figure 1. Visualisation of process performance using Excel -based energy dashboard (Ref. 1)
Selected recent applications of VTT BALAS
Mass and energy balances
Several processes have been modelled using VTT BALAS. Typically the models are so-called total site models, which include all the major processes and their inter-connections. With such model, process integration studies can be carried out to estimate impacts of different seasonal or operational scenarios on e.g. energy, water or carbon balances.
Numerous energy studies have been conducted with the help of VTT BALAS software. These studies have ranged from typical energy saving studies to integration of new, efficient technology into an existing process (Figure 2).
Figure 2. Comparison of different drying technology options (Ref. 3)
Modelling process modifications
Utilising link between VTT BALAS and Microsoft Excel, running superstructure-type models can be managed and for example different process modification scenarios assessed. Further automation in result processing within Excel enable dashboards (see example in Figure 1) to support the process design and design decision making. Figure 3 presents one example of a beverage production process with multiple process modification alternatives linked with the energy dashboard.
Figure 3. Simulation model for process design decision making (Ref. 1)
Water use reduction studies
These types of problems arise when we are considering re-using slightly contaminated process water in other parts of the process in order to reduce the fresh water demand. The main objective is to allocate process water in such a way that the intake of fresh water is reduced as much as possible without exceeding contaminant concentrations in critical parts of the process. Figure 4 illustrates modelling of COD and TSS for water network configuration change analyses using VTT BALAS.
Figure 4. Analysis of COD and TSS using VTT BALAS (Ref. 4)
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1. Hytönen E., Sorsamäki L., Nappa M., ”A generic modelling and simulation platform for assessing novel malting and brewing technologies”, EBC Symposium, Wrocław, Poland, 2016
2. de Souza Noel Simas Barbosa L., Hytönen E., Vainikka P., "Carbon mass balance in sugarcane biorefineries in Brazil for evaluating carbon capture and utilization opportunities", Biomass and Bioenergy, 2017, 105C: 351-363
3. Hytönen E. and Puumalainen T., ”Simulation-Based Analysis of the Influence of Impingement Drying on the Energy Concept of a Paper Mill Integrate”, Proceedings of the 15th International Drying Symposium (IDS 2006), Budapest, Hungary, 20-23 August 2006
4. H2020-SPIRE-2016, Grant no 723577, D3.2 Selected scenario simulation for process and cooling water reuse in the P&P industry, March 31st, 2019, http://www.spotview.eu/docs/filesProject/6/48365817-0B94-BA9C-C2C097648B571681.2-VTT-final.pdf