Bubble overlap in multipoint gas-injection systems
- PDF / 1,650,785 Bytes
- 10 Pages / 597.28 x 785 pts Page_size
- 91 Downloads / 226 Views
I.
INTRODUCTION
G A S injection into molten baths has been in practice for over a century in both ferrous and nonferrous industries, in one form or another, to carry out smelting, converting, fluxing, refining, slag fuming, and mixing operations. The metallurgical reactors (furnaces, converters, ladles, etc.) used to carry out these operations vary widely from plant to plant; they differ in shape, size, and gas-injection arrangements. More often, the steel industry employs cylindrical or pear-shaped vessels for high-intensity gas injection, whereas the nonferous industry, which operates under much lower gas flow rates per tuyere, commonly uses barrel or rectangular-shaped reactors. Depending upon the reactor size and shape and the availability of gas supply pressure, a single or multiple tuyere/lance arrangement has been adopted for submerged gas injection. Since most of the nonferrous reactors have low aspect ratio (bath depth to horizontal cross-sectional area) and the gas supply is from low pressure blowers, multituyere gas injection systems are generally used. Many examples of multituyere systemst~l can be cited. The Pierce-Smith converter for copper and nickel matte converting, a zinc fumer for lead blast furnace slag cleaning, and a tin fumer for tin slag cleaning are a few familiar examples of well-established processes using multituyere injection. A typical example of a Pierce-Smith converter with a multituyere bank is shown in Figure 1. New processes ~5] for continuous, direct, and bath smelting, such as the Noranda, QSL, and Mitsubishi processes, also incorporate multituyere injection for gas and solid injection. Furnace design aspects and selected operating parameters of a few selected copper convertersf6,71 and zinc fumers[41 are reported in Table I. From a close examination, it can be seen that all furnaces differ widely in their basic operating indices as well as in their bath size, depth, number of tuyeres, and gas flow rate per tuyere. The radius and length of the converters vary from 3.04 • 6.08 m to 3.96 • 10.68 m, and the number of tuyeres per furnace varies from 27 to 54. There does not appear to be any clear design and operational criteria to determine the spacing between the
tuyeres for a given tuyere diameter and gas flow through the tuyeres. The primary aim of a multituyere gas-injection process is to provide a high gas/melt interracial area by distributing gas uniformly across the melt. Therefore, number, location, diameter, and spacing between tuyeres become critical to achieving high gas/melt contact at a given gas flow rate. During the past 2 decades, a significant amount of work has been reported by a number of research groups around the world to advance the understanding of gas discharge phenomena from single-point injection, covering aspects of bubble formation at the injection point and breakup of these large envelopes away from the injection point in the form of a plume. However, all this understanding is limited to a single tuyere/lance injection system and only limited work is
Data Loading...
