Catalyst Temperature Profile Research Articles

Dynamic mathematical modeling of a novel dual-type industrial ethylene oxide (EO) reactor

In this paper, the dynamic behavior of a novel dual-type industrial ethylene oxide reactor has been proposed with taking catalyst deactivation into account. The configuration of two catalyst beds instead of one single catalyst bed is developed for conversion of ethylene to ethylene oxide. In the first reactor which is an industrial fixed-bed water-cooled reactor, the feed gas is partly converted to ethylene oxide. This reactor functions at very high yield and at a higher than normal operating temperature. In the second converter, the reaction heat is used to preheat the feed gas to the first reactor and a milder temperature profile is observed. The potential possibilities of a two-stage catalyst bed system are analyzed using a 1D heterogeneous dynamic model to obtain necessary comparative estimates. A differential evolution (DE) algorithm is applied as an effective and robust method to optimize the reactors length ratio. The results obtained from the simulation demonstrate that there is a desirable catalyst temperature profile along the dual-type reactor (DR) compared with the conventional single-type reactor (SR). In this way, the catalysts are exposed to less extreme temperatures and thus, diminishing the catalyst deactivation via sintering. Results from this study provided beneficial information about the effects of reactors configuration on catalyst lifetime and ethylene oxide production rate simultaneously.

Methane autothermal reforming in a reverse flow reactor on Rh/Al2O3 catalyst

Autothermal reforming of methane was investigated in a Reverse Flow Reactor with commercial Rh/Al2O3 catalyst in pellets. The process was carried out in a catalytic fixed bed reactor and switching of feed flow direction was obtained through four electrovalves synchronized in pair. Temperature profile of the catalyst bed was measured by fast IR thermography and product composition was measured with a continuous gas analyzer.Reactor performance and catalyst temperature profile are presented as a function of feed direction switching period, water to methane inlet ratio and total inlet flow rate. Results are compared to steady state operation.

Investigation of catalyst particle hydrodynamic and heat transfer in three phase flow circulating fluidized bed

Vaporization of gas oil droplets has significant effects on the gas–solid flow hydrodynamic and heat transfer characteristic. A three dimensional CFD model of the riser section of a CFB have been developed considering three phase flow hydrodynamic, heat transfer and evaporation of the feed droplets. Several experiments were performed in order to obtain the data needed to evaluate the model using a pilot scale CFB unit. The Eulerian approach was used to model both gas and catalyst particle phases comprising of continuity, momentum, heat transfer and species equations as well as an equation for solid phase granular temperature. The flow field and evaporating liquid droplet characteristics were modeled using the Lagrangian approach. The catalyst particle velocity and volume fraction were measured using a fiber optic probe. The comparison between model predictions of catalyst particle velocity and volume fraction with the experimental data indicated that they were in good agreements and the Syamlal-O'Brien was the most accurate drag equation. The CFD model was capable of predicting the main characteristic of the complex gas–solids flow hydrodynamic and heat transfer, including the cluster formation of the catalyst particles near the reactor wall. In addition, the simulation results showed droplet vaporization caused reduction of catalyst particle residence time. Moreover, the higher ratios of the feed to catalyst flow rates led to the lower values of the catalyst temperature profile minimum.

Temperature profile in a reverse flow reactor for catalytic partial oxidation of methane by fast IR imaging

AbstractCatalytic partial oxidation of methane with air was investigated in a reverse flow reactor with commercial Rh/Al2O3 catalyst in pellets. Temperature profile of the catalyst bed was measured by fast IR thermography and product composition was measured with a continuous gas analyzer. The effect of internal heat recovery on reactor performance and catalyst thermal stress is presented and compared with steady state operation. Feed direction switching time, total flow rate, and methane to oxygen ratio were investigated as process operating parameters. Data of catalyst bed temperature evolution during the flow cycle are presented and discussed. Comparison of dynamic heat integration with external feed preheating in terms of product composition and catalyst temperature profile is also presented. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Reactor temperature profile during autothermal methane reforming on Rh/Al 2O 3 catalyst by IR imaging

Catalytic autothermal reforming of methane was studied over a commercial rhodium catalyst as a function of feed flow rate, feed composition and oven temperature. The process is carried out in a catalytic fixed bed reactor inserted in a tubular oven. Temperature profile of the catalyst bed was measured by IR thermography and product composition was measured with a continuous gas analyzer. The effect of water addition at fixed flow rate on catalyst temperature profile was investigated in two ways. In one case, upon water addition, an equivalent amount of nitrogen was removed from the feed in order to keep oxygen and methane concentrations constant. With this protocol nitrogen to oxygen ratio varies as a function of amount of water in the feed. In the other case, upon water addition, nitrogen, oxygen and methane were all reduced to keep total flow rate constant, thus keeping both oxygen to methane and nitrogen to oxygen ratios constant. The effect of water addition on product composition was investigated as a function of reactor thermal level, regulated by acting on oven temperature.

Effect of water addition and stoichiometry variations on temperature profiles in an autothermal methane reforming reactor with Ni catalyst

Catalytic autothermal reforming of methane was studied over a commercial nickel catalyst as a function of feed flow rate, feed composition and oven temperature. Temperature profile of the catalyst bed was measured by IR thermography and product composition was measured with a continuous gas analyzer.The effect of water addition on product composition and catalyst temperature profile was investigated in two different ways: by keeping oven temperature constant and by adjusting oven temperature in order to achieve the same maximum temperature in the catalyst bed.Temperature distribution in the catalyst was measured and, for each operating condition, the fraction of catalyst above a limiting value for deactivation and below a limiting value for coke formation was quantified. These information were coupled with data of methane conversion and hydrogen production, to identify a region of favourable reactor operating conditions, in the plane AIR/CH4–H2O/CH4.

Simulation of a driving cycle in laboratory: an approach for testing catalysts suitable for automotive exhaust NO x abatement under lean conditions

Catalyst testing for the removal of NO x under lean conditions suffers from a lack of detailed information regarding catalytic activity if reaction conditions are permanently varied due to application of a driving cycle. To overcome this fact, a new laboratory reactor system has been developed which allows the simulation of an inlet catalyst temperature profile of the MVEuro2 driving cycle in the laboratory. The new reactor offers a non ambiguous and inexpensive method for testing catalysts under controlled dynamic conditions.

Some Problems in Developing a Catalytic Combustor Using Methanol Mixture.

Experimental studies have been carried out to investigate some problems in the development and practical use of a catalytic combustor using a methanol mixture. For the suppression of undesirable exhaust emission, the possibility of using a catalyst with a higher amount of noble metal than the usual level as a component of the entire catalyst layer is examined. The combustion characteristics of the catalytic combustor with water-containing methanol and with aged catalysts are also investigated. From the results, it was found that undesirable exhaust emission during the startup period was suppressed by use of the higher noble metal loaded catalyst as a component of the catalysts. Formaldehyde emission was increased as the contained water was increased in the range of zero to 15wt%. The reaction region moved downward with the use of the aged catalyst, and the catalyst temperature profile was decreased. This indicates that the emission characteristic on unburned species is degraded.

Magnetic determination of axial catalyst temperature profiles

AbstractA magnetic thermometric method is used to determine cross‐sectional average axial catalyst temperature profiles for superparamagnetic neckel catalyst beds during ethane hydrogenolysis, an exothermic reaction. Each solid temperature profile is determined from an axial profile of cross‐sectional average magnetization and is represented by a polynomial. In turn, each magnetization profile is determined from voltage data obtained as the bed is moved through an AC permeameter. A Fredholm equation of the first kind, “regularized” using a minimum variance constraint, is inverted to determine the magnetization profile.The determination of the axial temperature profile for a reactor operating at 11.0% conversion is detailed. It provides a good test of the method used. Some limitations of the method are highlighted by attempts to analyze data from a reactor operating at complete conversion. The potential for model parameter estimation is discussed.

Catalyst temperature profiles under poisoned conditions

Catalyst temperature profiles under poisoned conditions