On reduced modeling of mass transport in wavy falling films

In many industrial units such as packing columns, falling film reactors, etc., the liquid phase is designed as a falling film. It is well known that the mass and heat transfer in laminar wavy film flows is significantly enhanced compared to flat films. The kinetic phenomena underlying the increase in mass and heat transfer are, however, still not fully understood. For an efficient design of falling film units, computational models that account for these enhanced transport mechanisms are of key importance. In this article, we present a reduced modeling approach based on a long‐wave approximation to the fluid dynamics of the film. Furthermore, we introduce a new two‐dimensional (2D) high‐resolution laser‐induced luminescence measurement technique. Both in the numerical simulation results and in the high‐resolution 2D‐concentration measurements obtained in the experiments we observe similar patterns of high concentrations locally, especially in the areas close to the wave hump. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2265–2276, 2018     

Simultaneous measurement of local film thickness and temperature distribution in wavy liquid films using a luminescence technique

Heat transfer in falling liquid film systems is enhanced by waviness. Comprehension of the underlying kinetic phenomena requires experimental data of the temperature field with high spatiotemporal resolution. Therefore a non-invasive measuring method based on luminescence indicators is developed. It is used to determine the temperature distribution and the local film thickness simultaneously. First results are presented for the temperature distribution measurement in a laminar-wavy water film with a liquid side Reynolds number of 126 flowing down a heated plane with an inclination angle of 2°. The measured temperature distributions are used to calculate the local heat transfer coefficient and the convective heat flux perpendicular to the wall for different points in the development of a solitary wave.     

Thermodynamics and kinetics of coal gasification in a liquid iron bath

The thermodynamics and kinetics of the Molten-Iron-Pure-Gas (MIP) process used for coal gasification have been analyzed. In the MIP process, oxygen, fine-grained coal, and fluxes are injected into a liquid iron bath to produce a high temperature gas consisting of CO and H₂ plus a liquid basic slag. The sulfur is transferred from the coal to this slag. Computer calculations bearing in mind test conditions were used to determine equilibrium conditions as well as mass and energy balances; these indicated that the MIP process is technically feasible. The kinetics of the gasification process have been investigated by analyzing and assessing the basic reactions for a bottom-blowing MIP reactor. A comparison of all relevant reactions reveals that the dissolution of carbon in iron is the rate-determining step of the process. The bath turbulence induced by the injected gas and by the product gas results in intense mixing and dispersion of the reactants and their intermediate products. These phenomena create extremely large mass-transfer surfaces and extend the retention time of the reactants in the liquid iron bath. This results in high conversion rates relative to the volume of the MIP reactor.     

Smelting reduction of iron ore

On the basis of MIP development several process concepts for primary ironmaking technology were investigated. In the smelting reduction process described the reduction of iron ore occurs in three stages: in the first step the ore is preheated and prereduced in a cyclon-heat exchanger system. In the second step it is melted. The final reduction of the partially reduced and melted ore to metallic iron takes place in the MIP reactor.