IMPINGING STREAMS

In both stages, turbulent flow of the impinging streams is very desirable. The spent acid of the second stage, upon separation of the TNT, is fortified with aq nitric acid and is reused as the nitrating acid for the first stage... 

Features of liquid-continuous impinging streams and their influences on kinetics... 

A. Tamir, Impinging Stream Reactors—Fundamentals and application, Elsevier, Amsterdam, 1994. 

H. Sun, Y. Wu, J. Zhang and C. Xu, Pressure fluctuation in the submerged circulative impinging stream reactor, a paper To be pubhshed. 

Y. Wu, Y. Zhou, X. He and C. Bao, Crystal-growth rate of di-sodium phosphate in impinging stream crystallizer, a paper to be published. 

Example 5-8 Turbine Blade. Consider a fluid stream impinging on a turbine blade that is moving with a velocity Vs. We would like to know what the velocity of the impinging stream should be in order to transfer the maximum amount of energy to the blade. The system is the fluid in contact with the blade, which is moving at velocity Vs. The impinging stream velocity is V, and the stream leaves the blade at velocity Va. Since V0 = Vro + Vs and V = Vri + Vs, the system velocity cancels out of the momentum equation ... 

Gaddis E S, Vogelpohl A (1992) The Impinging-stream reactor A high performance loop reactor for mass transfer controlled chemical reactions, Chemical Engineering Science 47 2877-2882. 

A. Tamir, Process and phenomena in impinging-stream reactors, Chem. Eng. Prog. 86 (9) (1989) 53-61. 

The efforts to search for approaches to raising relative velocity between phases has led to the development and/or application of impinging stream contactors, and also some other devices. 

There is yet another method which also enhances transfer very efficiently, in which a stream is induced to impact a fixed wall surface, i.e., the impinging jet (IJ). Obviously, the flow configuration and the action of stream impingement of IJ are totally different from the impinging streams, although it uses also the term impinging ... 

Figure 1 Basic configuration and principles of impinging streams.

Elperin and Tamir considered that, in impinging streams with gas as the continuous phase, transfer between phases is enhanced by the factors below ... 

In the impinging streams of gas-liquid systems, high relative velocity between phases and collision between droplets favor surface renewing of droplets, resulting in reduced liquid film resistance and thus increased overall mass transfer coefficient. 

Impinging streams were first suggested for enhancing transfer between gas and solid phases however, the results of a large number of investigations have shown that, as well as this effect, the method of impinging streams has many other functions valuable for application of course, at the same time, it also has some disadvantages, unbeneficial to application [9]. 

Figure 1 represents the basic principles of gas-solid impinging streams, and also its essential structure as originally designed. On the basis of the essential structure, various devices can be constructed by extending the idea of impinging streams. Two extension schemes of IS have been proposed extension of the flow configuration and extension of the phase conditions of the substance systems involved, as described below. 

Starting with the elements necessarily included, the concept of impinging streams can be extended to include various flow configurations. Tamir el al. [5] investigated a number of impinging stream contactors with different flow configurations and the... 

Figure 2 Impinging stream contactors of various configurations [51. (a) Coaxial-horizontal two impinging streams (b) Horizontal three impinging streams (c) Coaxial-vertical two impinging streams (d) Curvilinear two impinging streams (e) Curvilinear four impinging streams (f) Four impinging streams. A—air P-—particles W water.

In addition to those shown in Fig. 2, there are many other different structures. Different impinging stream devices may have different flow configurations, although all of them contain the same essential elements (1) the streams flow in opposite directions and impinge against each other, and (2) each stream contains at least one continuous phase. 

Obviously, one of the necessary conditions to carry out impinging streams is that both the opposed streams in impingement must have, at least, one continuous phase. In the impinging streams shown in Fig. 1 the continuous phase is a gas although a liquid can of course also be the continuous phase. If a liquid is used, the dispersed phase should be a solid or another unmixable liquid. Otherwise, the employment of impinging streams would have less sense. 

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