Fluid dynamics in channel reactors stirred by submerged gas injection
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I.
INTRODUCTION
THE productivity of metallurgical processes involving gasliquid and liquid-liquid systems can be increased by changing from a batch process to a continuously operated process. In recent years, attempts have been made to develop continuous processes. Some of the examples of such processes are (a) the Noranda process Ill for continuous smelting and converting of copper and (b) the Q-S oxygen process t2'31 for production of copper in a single furnace. The Noranda process was intended to replace old reverberatory smelting and converting processes by a single cylindrical reactor. Powdered concentrate and flux injected at one end reacted in the oxygen-enriched air blown through tuyeres to give matte, slag, and sulfur dioxide. The slag and matte moved concurrently with velocities of the order of 1 mm per second through the reactor. The matte was blown toward the middle of the reactor to produce copper which settled and tapped therefrom. The slag was tapped from the discharge end, after being treated with reducing gases to reduce as much dissolved copper oxide as possible to metal. The copper loss in the slag was 10 to 12 pct due to the large extent of longitudinal mixing in the reactor. The Noranda process could not be successfully employed for production of copper due to large copper loss in the slag. At present, it is used for continuous matte production. Many converting or refining processes are usually carried out in more than one batch reactor, in which the product of one reactor is transferred to the next and different reactions take place in each reactor. If this complete process is to take place in one long reactor, then these individual steps are to be conducted successively as material passes through the reactor. Most of these processes have been studied in separate pieces of equipment and the chemistry and kinetics of these individual steps (reactions) are well understood now. The major question now is whether these steps could be joined together in one vessel; in other words, would longitudinal mixing be sufficiently low to allow these more or less distinctive, chemical operations to be conducted simultaneously in a long reactor as the material flows from one end to another. Therefore, in the design of any continuous Y. SAHAI is Associate Professor, Department of Metallurgical Engineering, The Ohio State University, 116 West 19th Avenue, Columbus, OH 43210. Manuscript submitted September 9, 1986. METALLURGICALTRANSACTIONS B
reactor where two or more chemically distinct operations are to take place simultaneously, it is important to know: (a) The length of the reactor required for individual operations to take place to the desired extent. (b) The length(s) of the "buffer zone(s)" required between two successive operations to avoid backmixing of the products of the later operation with the contents of the previous operation. These important aspects have, however, not been studied adequately and it is clear that further progress in the development of continuous processes must await a more detai
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