modelMethanator_L4

Information

1. Purpose of model

This model represents a discretized fixed bed methanator with reaction kinetics with constant effectiveness factors.

2. Level of detail, physical effects considered, and physical insight

The reactor is discretized and in each volume mass, impulse and energy balances as well as heat transfer between tube wall and synthesis gas in the tubes and reaction rate equations are solved. These equations are taken from Schlereth [1] except that the pressure loss is assumed to be constant and the effective reaction rates are calculated using constant effectiveness factors. Also the mass balances are stationary so changes in density are neglected.

3. Limits of validity

The model is valid if the changes of the effectiveness factors and the pressure loss are negligible.

4. Interfaces

gasPortIn: ideal gas inlet

gasPortOut: ideal gas outlet

heat: heat port

5. Nomenclature

(no elements)

6. Governing Equations

The used equations are described in [1] except for the changes described in 2. The pressure calculation for each volume can be done either using the pressure in the middle or at the end of the volume.

7. Remarks for Usage

The nominal value for the reactor's power can either be defines by the nominal mass flows or the respective nominal enthalpy flows of the mass flows. The scaling factors are always adjusted for an input of H2 and CH4 with a molar ratio of 4:1. Therefore the parameter "ScalingOfReactor" needs to and the corresponding nominal value needs to be set. Consider that scaling by the nominal mass flow of methane may leed to inaccuracies since the product of the reactor depends on the operating temperature and pressure.

ScalingOfReactor=1: The reactor is scaled by the nominal methane mass flow m_flow_Methane.

ScalingOfReactor=2: The reactor is scaled by the nominal hydrogen mass flow m_flow_Hydrogen.

ScalingOfReactor=3: The reactor is scaled by the nominal enthalpy flow of methane (H_flow_methane) defined by the product of methane mass flow and NCV of methane.

ScalingOfReactor=4: The reactor is scaled by the nominal enthalpy flow of hydrogen (H_flow_hydrogen) defined by the product of hydrogen mass flow and NCV of hydrogen.

8. Validation

The results of the model were compared to results from Schlereth (Figure 6.10) [1] and the outlet variables fit the results very well.

9. References

[1] David, Schlereth (2015): Kinetic and Reactor Modeling for the Methanation of Carbon Dioxide. Ph. D. Thesis. Technische Universitaet Muenchen, Muenchen.

10. Version History

Model created by Tom Lindemann (tom.lindemann@tuhh.de) in Mar 2016

Revised by Lisa Andresen (andresen@tuhh.de) in May 2016

Model modified by Carsten Bode (c.bode@tuhh.de) in Jul 2016

Model modified by Oliver Schülting (oliver.schuelting@tuhh.de) in Feb 2018

Parameters

Connectors

Components

Contents

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