Computational Fluid Dynamics, CFD
During the past 20 years the numerical simulation of heat transfer and turbulent flow phenomena in combustion systems has developed rapidly concurrently with the development of new and more powerful computers.
These mathematical models were originally used only within professional R & D environments such as universities. Among experts these programs are designated CFD codes/programs.
Following this development, commercial CFD programs have been developed for use in project planning, optimizing and diagnostic tests of plants. The CFD programs are advanced calculation tools for computations of 3-dimensional turbulent flow with heat and mass transfer.
- Temperature distribution
- Heat transfer - radiation, convection and conduction
- Gas velocity, flow distribution (velocity vector components)
- Pressure distribution and turbulence
- Combustion, concentrations
- Particle trajectories
We use the CFD programs for a series of combustion processes:
- Calculation of wall temperature and load in furnace and boiler room: shows the effect of water-cooled / refractory lined surfaces in the furnace and which parts are under the greatest stress. Study of the impact of comprehensive construction changes and the thermal conditions at the plant will be possible.
- Design and optimisation of flue gas recycling (FGR), which at the same time makes it possible to reduce excess air and control flue gas temperature in the furnace. This will result in a lower flue gas loss and consequently higher total efficiency and lower NOx emissions.
- Evaluate placement, number and design of nozzles for introduction of secondary combustion air and recycled flue gas for control of the furnace temperature.
- Design of post combustion chamber, e.g. for grates with under-stoichiometric combustion or chemical incineration plants.
- Analysis and documentation of dioxin requirements. Exact determination of residence times in limited temperature zones.
- Design of nozzles for injection of ammonia/urea and additives into the DeNOx system.
- Calculation of temperature and pressure loss in flue gas and air duct.
- Diagnostic tests of plants with process and combustion technical problems, e.g. plants with inadequate flow conditions, poor mixing, insufficient combustion - carbon monoxide problems, thermally strained surfaces and corrosion problems.
- The EU emission requirement calls for very low emissions of CO and TOC. To obtain this correct design of furnace and air injection is vital.
