Heat transfer-a review of 1986 literature

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Mathematical modeling of catalytic fixed bed reactors

Idealized mathematical models for multitubular packed-bed reactors, based upon simplifying assumptions concerning symmetry, regularity, and homogeneity of the packing and the intertubular space, are commonly used for analysis and design. In reality, substantial deviations from these assumptions occur and give rise to maldistributions, both for the flow of reactants through a packed tube and for the flow of a heat-transfer medium through the intertubular space. These maldistributions and methods of how to deal with them in reactor design and simulation are reviewed in this paper.The following areas are covered:  (i) porosity and flow patterns inside tubes, (ii) heat and mass transfer inside tubes, (iii) flow distribution over individual tubes, and (iv) distribution of coolant flow over the intertubular space.

Operational and Structural Nonidealities in Modeling and Design of Multitubular Catalytic Reactors

This paper presents a method mathematical modelling of cocurrent multitubular fixed-bed reactors. The method is adapted to the most widespread type of industrial reactor design, i.e. the system fitted with disk-and-doughnut baffles. The proposed model makes it possible to estimate the influence of non-uniformity of the heat carrier flow on the reactor characteristics, taking into account the coolant streams by-passing via the tube-to-baffle clearances. Based on the model, the effect of the operating parameters as well as of some more important geometrical parameters of the reactor on an exemplary highly exothermic process of partial benzene oxidation to maleic anhydride is discussed.

Advances in modelling and design of multitubular fixed‐ bed reactors

This paper presents results of investigations of a multitubular reactor with internal heat recuperation. The multitubular reactor with both the tube-side and the shell-side spaces packed with catalyst pellets or, alternatively, with an inert material and catalyst, enables one to heat up a relatively cold inlet reaction medium by internal heat recovery. The reaction heat transferred to the inlet reaction gas allows the gas temperature to be raised above the so-called “ignition” temperature. Considerably higher conversion than that in conventional solid-bed reactors is achieved owing to the temperature profile being much closer to the optimal one (decreasing when the gas approaches the outlet of the reactor), while in the conventional reactors there is a monotonic rise in temperature along the reactor pass. The results obtained were similar to those occurring in the reverse flow reactors of Matros, but without the necessity of inconvenient switching of the gas flow, and with none of its drawbacks. Comparing the types of reactors discussed, the idea of internal heat regeneration of Matros' reactor was replaced by internal heat recuperation. During laboratory experiments of SO 2 oxidation, for inlet concentrations of 2.3–3.3 % and inlet gas temperatures between 150 and 250 °C, a stable conversion of 95–98% was achieved. Later in the paper the pilot plant investigations are described. The construction of the reactor improves autothermal conditions of the reaction for low reactant concentrations. It seems to be advantageous not only for low-concentration SO 2 oxidation but for catalytic oxidation of toxic organic compounds or for any other reaction where problems with autothermal operation can occur.

Studies of multitubular reactors with internal heat recovery. Experiments with SO2 oxidation

A mathematical model of the liquid heat carrier flow in the intertubular space of parallel-flow multitubular reactors is presented. The model was verified experimentally by measurements carried out in a model multitubular apparatus of rectangular cross-section. If the design of the distributing plates in industrial reactors is based on this model, uniform heat transfer conditions may be achieved throughout the intertubular space. The uniformity of the coolant flow distribution can be quantified by a velocity uniformity index (VUI) introduced in this paper.

Zbigniew Leszczynski

Papers

Hydraulic design of multitubular reactors with a heat carrier flowing in parallel to the tubes