Processing. .693 fluid reactions

Thermal study is based on experiments which aim at cooling the process fluid. The process fluid temperature can, for instance, easily vary from 20 to 60 °C. Process fluid can be water at room temperature or heated with thermostat, whereas UF is water at 15 °C. Experiments with water are necessary since they allow the study of thermal performances of the reactor regardless of any other phenomenon (reaction, mass transfer, etc.). As a consequence, thermal study is an important preliminary step before performing chemical reactions. For each experiment, the operating protocol is as follows ... 

In the case of an instantaneous exothermic reaction, we can assume that aU the reaction heat is generated at the first part of the reactor. Considering a position where the process fluid temperature has not yet reached the corresponding utility... 

As the whole reaction occurs at the begirming of the reactor, the process fluid inlet temperature has been modified with the adiabatic increase of temperature ... 

As indicated in Section 9.2, a fluid-fluid reaction may be considered from one of two points of view depending on its involvement in a separation process or in a reaction... 

From a separation-process point of view, a fluid-fluid reaction is intended to enhance separation (e.g., preparation of feed for a subsequent process step, product purification, or effluent control for environmental protection). Examples include the use of ethanolamines for the removal of H2S and C02 (reactions (A) and (B) in Section 9.2), the removal of SO, by an aqueous stream of a hydroxide, and absorption of 02 by blood or desorption of C02 from blood. A solid catalyst may be involved as a third phase, as in hydrodesulfurization in a trickle-bed reactor. 

From a reaction-process point of view, a fluid-fluid reaction is used for the formation of a desired product or set of products. In addition to the three examples given in Section... 

The types of reactors used for fluid-fluid reactions may be divided into two main types (1) tower or column reactors, and (2) tank reactors. We consider some general features of these in this section and in Section 24.3. In Sections 24.4 and 24.5, we treat some process design aspects more quantitatively. 

ABSTRACT Atmospheric carbon dioxide is trapped within magnesium carbonate minerals during mining and processing of ultramafic-hosted ore. The extent of mineral-fluid reaction is consistent with laboratory experiments on the rates of mineral dissolution. Incorporation of new serpentine dissolution kinetic rate laws into geochemical models for carbon storage in ultramafic-hosted aquifers may therefore improve predictions of the rates of carbon mineralization in the subsurface. 

Figure 9-5 Sketches of shrinking or growing films and particles, with arrows going dtiier forward or backw d as the process progresses, Reaction is assmned to occiu only at the interface of tile solid with tiie fluid.

Corrosion in metallic components occurs when pure metals and their alloys form stable compounds with the process fluid by chemical reaction or electrochemical processes resulting in surface wastage. Appreciable corrosion can be permitted for tanks and piping if anticipated and allowed for in design thickness, but essentially no corrosion can be permitted in fine mesh wire screens, orifice plates and other items in which small changes in dimensions are critical. Rates of corrosion can be heavily affected by temperature changes and whilst a material of construction may be suitable at one temperature, it may not be appropriate for use at a higher temperature with the same process fluid. 

It is desirable to list the sequence of space and point steps which together constitute global adsorption. This is not a new concept and such descriptions have frequently been presented (I, 14), particularly for fluid reactions on porous catalyst particles. The first space process, axial dispersion, is not a part of the. sequence, but it does affect the observed kinetics, and is logically considered as a space process. Its significance depends upon the reciprocal of the axial Peclet number, EJ(2R)v. The sequential steps are ... 

A limited set of phenylenediamine color developers are used. Kodak s CD-3, CD-4, and CD-6 (26-28) are the principle color developers used today [31], They are directly incorporated into the alkaline processing fluid. The methyl group in the 2-position is important for preventing side reactions and enhancing the formation of the desired dye. The phenylenediamine undergoes a two-electron oxidation to quinonediimine, which then reacts with the color couplers to form the desired chromophores [32],... 

In many tubular reactors cooling or heating occurs as the process fluid flows through the reactor. This produces a major difference between an adiabatic and a nonadiabatic tubular reactor. In an adiabatic reactor, with an exothermic irreversible reaction, the maximum steady-state temperature occurs at the end of the reactor. In a cooled reactor, the maximum steady-state temperature usually occurs at some axial position part way down the reactor. Thus the temperature does not change monotonically with length. 

The uranyl ion luminesces in fluid solutions at room temperature2 201 202 thus providing a tool for the study of bimolecular excited state processes. In several cases, however, this study is complicated by the fact that the uranyl ion forms complexes with a variety of chemical species, so that it is often difficult to distinguish between intramolecular photochemical processes involving uranyl ion-ligand complexes and intermolecular photochemical processes involving reaction between an electronically excited UO + species and the substrate2,201,202 ... 

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