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CFD Simulations

Download PDF Presentation CFD Simulations

CFD (Computational Fluid Dynamics) is the spatially (and temporally) resolved simulation of flow and heat transfer processes. CFD enables the 3D visualisation of laminar or turbulent reactive flows in combustion, gasification as well as pyrolysis reactors, which may also be multi-phase systems. CFD simulations thus constitute an excellent tool for process analysis as well for the design and optimisation of plants.

BIOS has a considerable number of CFD models in use which are especially designed for the development and optimization of biomass combustion, gasification and pyrolysis plants.  These models also undergo continuous further development. They cover, for instance, grate, fixed bed and entrained flow combustion, gasification and pyrolysis models, models for the turbulent reactive gas flow in combustion, gasification and pyrolysis reactors, a detailed NOx formation model, an aerosol formation model, an ash deposit formation model as well as a tar conversion model).

BIOS is a competent partner for the CFD supported development and optimization of biomass combustion, gasification and pyrolysis plants. Special applications such as the evaluation and optimisation of pressurised air cleaning systems or the design and optimisation of mixing chambers complete the offered services.

Advantages of CFD-based plant design

  • Improved basic understanding of the processes taking place in combustion, gasification or pyrolysis reactors
  • Reduction of development time and costs for test runs
  • Increased reliability in technology / plant development
  • Increased plant availabilities and operating hours
  • Increased fuel flexibility
  • Reduced material wear
  • Increased plant efficiency
  • Reduced emissions
  • Compact reactor design

Fields of activity

BIOS performs CFD simulations for the following plants and technologies:

  • CFD-based development and optimisation of biomass combustion plants and boilers
  • Development and optimisation of biomass fixed bed gasifiers and gas burners
  • CFD-based development of biomass fixed-bed pyrolysis and torrefaction plants as well as of pyrolysis gas and pyrolysis oil burners
  • Design and optimisation of heat exchangers and condensing units
  • Application of the combustion models for waste incineration plants
  • Calculation of heat and pressure losses in pipe networks (e.g. district heating)
  • Simulation of cyclones (particle precipitation, erosion tendencies, cyclone combustion chambers)
  • Simulation of electrostatic precipitators
  • Flow simulations in and around boiler houses and industrial plants
  • Evaluation and optimisation of pressurised air cleaning systems
  • Design and optimisation of (pre-)mixing chambers (e.g. pre-mixing of recirculated flue gas and combustion air, quench systems)
  • Simulation of heat storage tanks (stratified storage tanks, solid matter storage tanks, latent heat storage systems)
  • Simulation of melting reactors for industrial applications
  • Modelling of NOx and SOx formation and reduction under consideration of detailed kinetic models
  • Modelling of aerosol (fine dust) formation as well as of deposit formation
  • High-temperature equilibrium calculations
  • Modelling of tar conversion in biomass gasification and pyrolysis reactors

Industry sectors

BIOS performs CFD simulations for the following clients / customers:

  • Producers of
    • small, medium and large-scale fixed bed and grate furnaces
    • wood log fired boilers and stoves
    • pellet fired boilers and stoves
    • pulverised fuel furnaces
    • cyclone combustion chambers
    • fixed bed pyrolysis and torrefaction reactors
    • fixed bed gasifiers
    • flue gas cleaning plants
    • district heating pipes
    • heat exchangers and condensers
    • electrostatic precipitators
    • heat storage tanks
  • Operators of biomass furnace and boiler plants as well as of biomass gasifiers and pyrolysis and torrefaction reactors such as
    • Municipalities and local authorities
    • Utilities and municipal energy suppliers
    • Heat supply companies
    • Sawmills and the wood industry
    • Other commercial and industrial companies

The CFD simulations are carried out for new plants (development or planning projects) as well as for existing plants (optimisations, reconstructions).

Project phases

BIOS performs CFD simulations in the following project phases (individual changes depending on the project requirements and scope are possible):

working field cdf simulations en

Scope of CFD simulation services

BIOS offers the following CFD simulation work in the different project phases:

Actual state analysis

  • CFD simulations to evaluate a basic plant concept
  • Evaluation of the CFD simulations and identification of strengths and weaknesses
  • Preparation of a catalogue of measures to optimise the basic concept

Stepwise optimisation (sensitivity analysis)

  • CFD aided sensitivity analyses for the optimisation of the basic concept according to measures from the actual state analyses
  • The scope of the sensitivity analyses comprises both geometric (e.g. different nozzle geometries) and operational measures (e.g. different air staging concepts)
  • Optimisation goals can be:
    • emission reduction (e.g. CO, NOx, PM)
    • efficiency optimisation
    • reactor volume reduction
    • minimisation of erosion and slagging effects
    • increase of fuel flexibility
    • increase of product gas quality
    • optimisation of pyrolysis conditions for biochar production

Definition of a pre-optimised concept

  • Based on the results of the sensitivity analyses a pre-optimised concept is compiled and discussed with the client.

Performance of test runs at a realised pre-optimised testing plant

  • BIOS offers accompanying test runs and measurements at testing plants.
  • Such test runs evaluate the performance of the technology / plant under real-life conditions and can either be performed at the testing facilities of BIOS or of the client.

CFD simulations based on selected test runs

  • Comparison of measurement and simulation results to evaluate the plant concept.
  • CFD simulations based on selected test runs allow an efficient weak point analyses under consideration of practical experiences.

CFD based further development and optimisation of the technology / plant

  • CFD-based formulation of an optimised concept and detailed discussion with the client to ensure a proper implementation of the proposed measures.


  • Performance of up- and downscales based on similarity approaches and subsequent evaluation based on CFD simulations.

Simulation-aided plant monitoring

  • A simulation-aided plant monitoring of systems in operation supports an efficient weak point analysis and thus contributes to a targeted optimisation of plant operation

Simulation tools

BIOS performs simulation work usually using the CFD software ANSYS Fluent. In-house developed models are implemented in Fluent using so-called User Defined Functions (UDFs) in order to enable detailed simulations of biomass conversion reactors.

Moreover, BIOS develops OpenFOAM modules for many relevant applications, which are also applied for CFD simulations.

BIOS additionally provides with the software package OpenBioPD (Open-Source-Software based Bioenergy Plant Design) customised CFD simulation tools for clients based on OpenFOAM. OpenBioPD is thus of interest for clients which intend to perform CFD simulations by themselves.