4. Conclusions
Computations are performed using grids with varying nodal densities to
determine the optimum node spacing and density that would give the
desired accuracy and minimize computation time. The final grid density
is determined when the centerline profiles of temperature and species
concentration do not show obvious difference. The second-order upwind
scheme is used to discretize the mathematical model, and the
semi-implicit method for pressure-linked equations algorithm is employed
to solve for the pressure and velocity fields. The simulation
convergence is judged upon the residuals of all governing equations.
Particular emphasis is placed upon the effect of various factors on the
thermochemical steam reforming processes in heat integrated reactors.
The major conclusions are summarized as follows:
- Steam reforming produces hydrogen and carbon monoxide when heat is
added to a catalytic reactor containing steam and hydrocarbons.
- Alternating channel parallel plate designs can be applied to thermally
coupling endothermic steam reforming with combustion in neighboring
channels.
- Balancing the heat requirements of an endothermic reaction with heat
generated by an exothermic reaction flowing parallel to and on the
opposite side of a separating plate is extraordinarily difficult since
the endothermic reaction is likely to have a very different dependence
upon concentration and temperature than the endothermic reaction.
- A convenient way to supply heat is to couple the endothermic reaction
with an exothermic combustion reaction in the heat exchange channels.
- The process gas is raised in temperature and this energy can be
utilized by the reforming process.
- The catalyst coating thickness depends upon the process proceeding
within the catalyst matrix.
- The arrangement leads to improved heat transfer and therefore chemical
conversion.
- Heterogeneous combustion aids in spreading the heat generation along
the length of the channel and helps prevent hotspot formation.