VTT BALAS – Conceptual process design to optimise resource efficiency

Process design and analysis is always based on the management of mass and energy balances. VTT BALAS simulation tool is the most effective way to calculate and optimize complex processes, energy and material streams. With VTT BALAS you can reduce costs by optimizing the use of chemicals, energy and water in your processes.

VTT BALAS is a steady-state simulation package for chemical processes with emphasis on pulp and paper, food processing and biochemical processes. The software has been developed at VTT over the last 20 years and many paper mills, engineering companies and equipment manufacturers currently use it.

Hours can be saved by using BALAS simulation models linked with Excel to create comprehensive equipment lists and dimensioning information.

Esa Pietilä, Specialist, Valmet Technologies

Efficient and easy-to-use process simulation

VTT BALAS has an extensive selection of unit operation modules. These unit operation modules enable the user to model the whole process including raw material handling and processing, reactors, heat recovery, utilities and wastewater treatment. A selection of ready-made model processes are also supplied with the software. Furthermore, the mathematical solvers of VTT BALAS solve balances for complex process flowsheets efficiently.

BALAS simulation models help us select the most cost efficient processes.

Jenni Vainio, Quality and Environment Manager, Oy Essity Finland Ab

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process chart exmaple industrial

How to calculate complex industry processes easily?

VTT BALAS simulation models are created and maintained through an intuitive user interface. The model is built up in MS Visio by dragging and dropping unit operations from libraries, drawing streams connecting units, and entering input data using dialog windows. MS Excel can be used to further process the balances into usable metrics.


Top reasons to use modelling and simulation

There are several benefits of using process modelling and simulation in industrial decision-making processes. Changes to complex systems can be calculated in a matter of seconds. Simulation results can guide an industrial process to significantly increase its efficiency by reducing excessive material and energy consumption. Alternative choices can be safely tested before making an investment. Covering the whole lifecycle of a factory from the R&D phase to factory optimisation can support data-driven decision making.

Explore how to improve the speed and flexibility in R&D and factory optimisation using process modelling and simulation from our Process modelling and simulation guide. 

man in safety gear fixing complex industrial equipment

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:

  • TMP
  • DIP
  • Paper mill including paper machine (uncoated), debarking plant, effluent treatment plant, water preparation plant, CHP power plant
  • Detailed paper drying
  • Bioethanol production
  • CO2 separation

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.


Calculation modes

Steady-state simulation

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.

Parameter estimation

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)

vtt balas excel based view

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.

Energy studies

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)

vtt balas comparison graph

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)

vtt balas Simulation model for process design decision making

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)

vtt balas Analysis of COD and TSS

Redesign of an existing paper machine

Process simulation is an effective tool for studying the conversion of an existing process into a new one. VTT BALAS was used to study the conversion of an existing paper machine from water-laid technology to foam-laid technology. The simulation results revealed the changes in process volume flows and consistencies, the necessary process configuration changes and possible bottlenecks in the existing process.

Figure 5. Process simulation reveals the changes in process volume flows between considered scenarios (Ref. 5)

Tilavuusvirtakuvaaja Balas

Process simulation as input for techno-economic assessment (TEA)

Techno-economic assessment (TEA) using process simulation and cost modelling plays an important role in assessment of process concepts and in steering development work. VTT BALAS was used to study the implications of certain crucial process parameters on the techno-economics of a NMMO-Lyocell textile fibre production process.

Figure 6. Process simulation coupled with cost modelling indicates the effects of process changes on the production cost breakdown for considered scenarios (Ref. 6)

Lyocell_TEA Balas


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. http://www.ebc-symposium.org/uploads/mycms-files/documents/2016/presentations/L14%20Hytonen.pdf

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. https://cris.vtt.fi/en/publications/carbon-mass-balance-in-sugarcane-biorefineries-in-brazil-for-eval

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

5. Sorsamäki, L., Hytönen, E., Koponen, A., ” Process Simulation-based Evaluation of Design and Operational Implications of Water-laid Paper Machine Conversion to Foam Technology”, BioResources , 2021, 16(3), 5148-5186. https://www.vttresearch.com/sites/default/files/2024-04/Process%20Simulation-based%20Evaluation%20of%20Design%20and%20Operational%20Implications%20of%20Water-laid%20Paper%20Machine%20Conversion%20to%20Foam%20Technology.pdf

6. Hytönen, E., Sorsamäki, L., Kolehmainen, E., Sturm, M., von Weymarn N., “Lyocell Fibre Production Using NMMO – A Simulation-based Techno-Economic analysis”, BioResources, 2023, 18(3), 6384-6411. https://www.vttresearch.com/sites/default/files/2024-04/Lyocell%20Fibre%20Production%20Using%20NMMO%20%E2%80%93%20A%20Simulation-based%20Techno-Economic%20analysis.pdf

Contact us for details

Lotta Sorsamäki
Lotta Sorsamäki
Senior Scientist
Karri Penttilä
Karri Penttilä
Senior Scientist