Chemical and process industry

CFD modelisation for the chemical and process industry

The use of Computational Fluid Dynamics (CFD) has become increasingly widespread in the chemical industry. The physical phenomena and types of flows involved in chemical processes are often complex. For example, one can encounter multiphase flows, involving chemical reactions as well as mass and heat transfer.

CFD simulation is an indispensable tool for optimizing chemical processes. It helps to reduce development costs, improve equipment performance, optimize heat and mass transfer, and increase safety while reducing and controlling environmental impacts. By integrating CFD into the design of reactors, equipment and plants, chemical industries can considerably improve their efficiency.

Some examples of CFD simulation applications in chemistry and processes are given here.

Reactor design and optimization

• Fluidized-bed reactors: Fluidized-bed reactors allow solid particles to be suspended in an ascending fluid flow. CFD simulation can be used to model solid and gas phase distribution, mixing, void fraction and interfacial areas, and thus quantify heat and mass transfer.
• Stirred-tank reactors: In a stirred-tank reactor, the reactants are introduced into the tank and mixed by an agitator. This can be a continuous or batch process. CFD models will help to simulate fluid behavior (velocity fields, turbulence, residence time, reaction advancement, shear stresses, heat exchange with the heating system – double jacket, internal coil, etc.), in order to characterize and optimize operating conditions.
• Tubular reactors: in tubular reactors, the reactants circulate in a long pipe, which can be heated by a coaxial tube, or a furnace for instance. Simulation can be used to determine mixing, velocity, rate of advance and heat transfer. It is also possible to simulate the impact on the process of geometry, static mixers or a variable temperature profile.

Mixing and heat transfer optimization

• Mixers and agitators: Fluid Mechanics simulation is used to model mixers in order to maximize their efficiency, minimize energy consumption and ensure homogeneous distribution of reactants and/or products.
• Heat exchangers: characterization and optimization of heat transfers is also possible, thus improving the energy efficiency of equipment.

Modeling multiphase phenomena

• Multiphase flows: In many chemical processes, multiphase flows are present (liquid-gas, liquid-solid, etc.). CFD can model these complex flows, as in fluidized bed reactors or phase separators.
• Bubble-column reactors: CFD simulation can be used to study bubble distribution, coalescence and phase separation, as well as mass and heat transfer efficiency in bubble reactors.
• Cyclones and separators: Cyclones can be used to separate particles from gases. Their operation can be simulated and improved by CFD simulation, for example by analyzing the impact of geometric parameters in detail, and then optimizing them.
• Combustion systems: Burners and incinerators are ubiquitous in chemical processes for a variety of applications. CFD simulation can be used to model them, integrating, for example, combustion phenomena, pollutant generation, radiative heat transfer, etc.

Risk analysis and safety

• Atmospheric dispersion of pollutants: one of the main applications is the simulation of atmospheric dispersion of hazardous and/or polluting chemical species. By modeling these incidental and accidental scenarios under a wide range of meteorological conditions, it is possible to assess the risks for populations and the safety distances, as well as to propose optimized sensor networks to guarantee safe and early detection of any such phenomenon.
• Simulation of explosions and leaks: In the event of gas or hazardous chemical leaks, CFD can simulate the dispersion of gases in the atmosphere to assess risks and improve the design of safety systems.
• Fire simulation: Fires in chemical production units can be modeled to better understand fire propagation and improve prevention, warning and suppression systems.