Millisecond catalytic wall reactors: I. Radiant burner

Abstract

Short-contact-time reactors ha®e potential for high throughput in reactors much smaller than their traditional counterparts. While they operate adiabatically, heat can be exchanged at short contact time by integrating heat exchange into the reactor. Hot effluent of exothermic reaction systems can be redirected o®er feed gases to recuperate a portion of the sensible heat. Placing catalyst directly on reactor walls eliminates the resistance to heat transfer in the thermal boundary layer so that heat released by combustion can be effecti®ely coupled to an emitter, such as in a radiant burner. A radiant heater was constructed, operated, and simulated incorporating short contact time, energy recuperation, and a catalytic wall. This burner operated stably for many hours at a firing rate from ; 50 to ) 160 kWrm 2 at a radiant temperature of 950 to 1,150 K at a radiant efficiency of ; 60% with a residence time in the reacting zone of ; 10 ms. This reactor was modeled using 2-D Na®ier-Stokes equations including detailed models for chemistry and heat transport. Temperature and compositions predicted agreed well with experimental measurements.

Enhanced Methane Conversion to Olefins and Aromatics by H-Donor Molecules under Nonoxidative Condition

“…In this study, we explore a catalyst-coated quartz reactor, with a catalytic layer containing iron (denoted as Fe-reactor) coated on the inner wall (Figure S5), because this type of reactor was reported previously to be beneficial for development of homogeneous gas-phase reaction and reducing mass and heat transfer limitation. , The use of a catalyst-coated reactor has been successfully highlighted in several catalytic reactions. ,,− Recently, embedding the Fe/SiO 2 into the wall of quartz tube was used as the reactor for methane conversion, and a conversion of 11.3% was obtained with a C 2 selectivity of 30.3% at 1273 K and 20 mL/min . We also analyzed the radial mass transport and the external mass transport by referring to the dimensionless criteria, i.e., Péclet number (Pe’) and Carberry number (Ca), respectively (see SI for details).…”

Short Contact Time Catalytic Partial Oxidation (SCT-CPO) for Synthesis Gas Processes and Olefins Production

“…Since the very early academic and patent publications of years 1992–1994, − the long “travail” leading to the industrial technology development progressed through extensive laboratory scale experiments − and theoretical investigations − that after few years continued in parallel with experiments performed under high pressure conditions − the bench scale and subsequently at the pilot scale plants. − …”

“…Early works on SCT-CPO − were mainly focused on the investigation of the catalyst properties and on reaction kinetic issues, but later on ,, the similarities between the SCT-CPO phenomena and those produced in fuel rich combustion in porous media − clearly appeared. Some of these similarities are the following: − (i) the temperature of the catalytic bed (the porous medium) raises steeply at the reaction ignition section and is stabilized at relatively constant values in the axial and radial directions, (ii) large local temperature differences originate between the gas and the solid phases due to heat and mass transfer limitations, (iii) some local surface temperature values rise higher than the adiabatic equilibrium temperatures, and (iv) the catalytic processes (surface combustion processes) occur at residence times that are 2–3 orders of magnitude lower than those of the other catalytic reactions and with a rate faster than those of the free flame reactions.…”

Studies on a heat-recirculating microemitter for a micro thermophotovoltaic system

“…Although the micro thermoelectric power systems could much improve the difficulties of fabrication and assembly, there are still technological challenges: complicated structure for homogeneous gasphase combustion and a maintenance problem due to easily poisoned catalyst surface for catalytic combustion. Schmidt and co-workers developed radiant micro burners applying the heat-recirculation concept and catalytic combustion for reforming various fuels [7,8].…”