Thermal Runaway Conditions of a Partially Diluted Catalytic Reactor

Quina, Margarida J.; Ferreira, Rosa Cristina Moutinho

doi:10.1021/ie9807295

Cited by 31 publications

(13 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4) reflects this influence. These results can also be compared with the axial profiles we obtained in a previous study with a heterogeneous model, HT, for a random packing with two catalytic zones [11] and also with some data obtained in an industrial reactor packed with the conventional hollow cylinders. It can be observed that it is possible to select λ values that will be favourable to the process.…”

Section: Computer Resultsmentioning

confidence: 61%

Structured catalysts for partial oxidations

Campos

Quinta‐Ferreira

2001

Catalysis Today

View full text Add to dashboard Cite

The objective of the present work is centred on the analysis of the behaviour of fixed-bed reactors packed with structured catalysts when a partial oxidation takes place. The fluid flow within an element, formed by the intersection of two adjacent corrugated plates, was mathematically modelled and numerical simulations were performed in order to study possible optimising of the catalyst structure. A simple model, involving the continuous stirred tank approach, was used to simulate the performance of the catalyst in an industrial reactor. The profiles of temperature, concentration, velocity and pressure along the reactor were obtained through the global mass balance, partial molar balances, conservation of moment, energy balance and mechanical energy balance. These equations were applied to an exothermic reactional system, the selective oxidation of methanol to formaldehyde, in order to evaluate the possibility of application of these catalysts in industry. Various parameters specific to the catalyst and the reactional system were tested in order to achieve a better understanding of the behaviour of these structured packing. The comparison with the heterogeneous model predictions for a random packing and with industrial values pointed out that the choice of parameters is fundamental to the performance of the catalyst. The adjustments to the parameters allows for significant improvements in some of the more troublesome aspects of the reactional system. Lowering the hot-spot, reducing the progress of the secondary reaction and reducing the pressure drop are the main enhancements that these structured catalysts can offer.

show abstract

Section: Computer Resultsmentioning

confidence: 61%

Structured catalysts for partial oxidations

Campos

Quinta‐Ferreira

2001

Catalysis Today

View full text Add to dashboard Cite

show abstract

“…In a previous work (Quina & Quinta Ferreira, 1999a) we have shown that for certain inlet operating conditions (C +M , ¹ M ) the hot-spot temperature can follow a runaway process. This is the case for C +M "3.4 mol/m and ¹ M "530 K. Therefore, we have changed the inlet methanol concentration from 2.4 to 3.4 mol/m for a "xed feed temperature of 530 K, in order to determine the dynamic behavior of the system.…”

Section: Transient Response To Step and Ramp Changes In Inlet Variablmentioning

confidence: 92%

Start-up and wrong-way behavior in a tubular reactor: dilution effect of the catalytic bed

Quina

Quinta‐Ferreira

2000

Chemical Engineering Science

View full text Add to dashboard Cite

The start-up and the wrong-way behavior of a "xed-bed reactor were analyzed through one-dimensional heterogeneous and pseudo-homogeneous models. The simulation work was based on the methanol oxidation to formaldehyde, which takes place in a "xed-bed reactor with two distinct zones. In the "rst part of the reactor, the catalyst was diluted with inert, and in the second zone the catalyst is pure. This activity pro"le leads to new features on the start-up and wrong-way behavior of the system when compared with a uniform catalytic bed. For a partially diluted bed, when the inlet temperature is increased (decreased), the "nal steady state can show a hot spot lower (higher) than the initial one. This behavior is not observed in a one-zone bed, where the "nal steady-state maximum temperature is always higher (lower) than the initial one if the inlet temperature is submitted to a positive (negative) change. During the dynamic period, the transient pro"les are closer to the initial steady states in the case of the two-zone bed, pointing out that the catalyst dilution in the upstream section of the reactor can decrease the system sensitivity in both steady state and dynamic period. The di!erences between the predictions obtained through the pseudo-homogeneous and the heterogeneous models can be more signi"cant on the transient responses than on the steady state situations and the wall temperature is the most important parameter on the reactor dynamic response. Moreover, signi"cant wrong-way behavior can occur for step changes and ramp variations in feed and wall temperatures.

show abstract

“…This z-MV criterion (referring the state sensitivity functions varying with the reactor length z) has been reported as being robust to complex kinetic models, indicating less conservative predictions of runaway boundaries than most geometrical or explicit methods. 5,27 The runaway boundary of the control variable u c (ϕ j ) corresponds in the MV method to the Max |S(T max ; u)|. Thus, by taking u = T 0 , the resulting [S(T max ; T 0 ) vs. T 0 ] plots for various ϕ j operating parameter values, allow establishing the runaway boundaries in every parametric plane [T 0 vs. ϕ j ], as represented in Fig.…”

Section: )mentioning

confidence: 99%

Derivation of Pareto Optimal Operating Policies Based on Safety Indices for a Catalytic Multi-tubular Reactor Used for Nitrobenzene Hydrogenation

Maria

Khwayyir

Dinculescu

2016

Chem.Biochem.Eng.Q.

View full text Add to dashboard Cite

When highly exothermic/hazardous reactions are conducted in the presence of parametric uncertainty, derivation of optimal operating policies for a chemical reactor has to simultaneously consider several objectives of sustainability. The paper uses an original methodology to generate the Pareto optimal solutions when reactor productivity and safety objectives (expressed in probabilistic terms) are simultaneously considered using the process and reactor model in a simple way, in the presence of technological constraints, uncertainty in safety boundaries, and random fluctuations in control variables. An example is provided for the industrial fixed-bed tubular reactor used for the catalytic hydrogenation of nitrobenzene to aniline in vapour-phase.

show abstract

Thermal Runaway Conditions of a Partially Diluted Catalytic Reactor

Cited by 31 publications

References 37 publications

Structured catalysts for partial oxidations

Structured catalysts for partial oxidations

Start-up and wrong-way behavior in a tubular reactor: dilution effect of the catalytic bed

Derivation of Pareto Optimal Operating Policies Based on Safety Indices for a Catalytic Multi-tubular Reactor Used for Nitrobenzene Hydrogenation

Contact Info

Product

Resources

About