Chemical reactor

Sketch of a stirred tank

The chemical reactor is the part of a plant, run in the chemical processes and are carried out in the chemical reactions.

Designs

Chemical reactors are available in two main formations,

  • The stirred tank and
  • The flow tube, a flow reactor.

Modes

Both types of reactors can be operated in the (discontinuous) set or batch operation and the continuous process. In block mode, a stirred tank is filled with reactants and as completely as possible after the last reaction, the products be removed from the stirred tank. In continuous operation, the starting materials a stirred vessel or draft tube are continuously fed and the product continuously removed.

Interpretation

The design of a chemical reactor is the task of chemical reaction engineering. For the device-related and economic calculation, the following factors are needed to optimize the response.

  • For the course of the overall reaction and essential processes reaction mechanism, kinetics and heat balance should be known.
  • For the reactor size are values ​​for mass transport as flow regime, mixing, and to material data for viscosity and thermal coefficients necessary.
  • From the heat balance and the reaction sequence to statements on the cooling or heating arise.
  • Special hazards arising from the substances involved ( corrosivity, reactivity of intermediate or by-products, potential thermal runaway ) and the reaction conditions (extreme temperatures, pressure vessel ) result must be known.
  • Finally, it must be clarified how the reactants added and the products are removed (cleaning, recycling, subsequent reactions ).

Idealized reactors are first, that interpretation usually considered. This refers to models of the desired reaction vessel, allowing on the basis of the mathematical modeling simplifications.

For the design of chemical reactors models are used ( process simulation ) in a first step, mainly software-based. In a second step, the mathematical models can be optimized by the reactors are built up on a laboratory scale, and possibly also on a technical scale. Finally, the plant will be built by scale-up in production size.

Special designs

  • In the manufacture of polymers, the shape is affected by the often extremely high viscosities of the reaction mixtures.
  • Catalytic processes require the needed large contact areas with solid catalytic materials to create.
  • For biotechnological processes are due to the temperature sensitivity of biological materials special designs required.

Various reactors in chemical manufacturing

In chemical production, a distinction is made between different reactors. The best known in the chemistry of the stirred tank ( also called stirred tank ). In stirred tanks chemical reactions are carried out in liquid phase. The reaction time is relatively long. The processed amounts are different depending on Rührbehältergröße and residence time. Reactors are large steel box, equipped with a stirrer and heating mantle. By stub baffles project into the container. They prevent the entire contents of the container rotates along with the stirrer and mix the reactants. Other ports in the lid ensure the supply of the reactants and are used for inserting measuring instruments. At the bottom of the stirred tank is the drain connection that is opened and closed by a valve plate. In the stirred tank batch reactions are carried out, which run at ambient conditions or moderately elevated pressure and temperature to about 250 ° C.

Exist, depending on the operational requirements, the stirred tank made ​​of carbon or alloy steel or are plated, enameled (glass- coated) or rubberized. For particularly aggressive media (eg HF and HCl) linings perfluoroalkoxylalkane (PFA ) can be used that are resistant depending on the medium and design up to a temperature of 250 ° C.

In addition, there are still high-pressure, high-temperature, pipe, loop and fluidized bed reactors.

Product (chemistry) Chemical kinetics Bioreactor
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