<報文>黒鉱系銅精鉱の溶錬産出物に関する研究(第3報) : 自溶炉ボイラ煙灰の組織について

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It is well known that the results of the matte smelting by a flash furnace are greatly affected by the operation of the waste heat boiler which is often disturbed by the formation of accretion of dust. The dust from the flash smelting furnace may be classified as follows (the chemical compositions of each type of the dusts are shown in Table 1) : i) Dense and hard accretion formed on the connecting portion between the furnace uptake and boiler radiation section ; ii) Black or greyish-black accretion formed on the wall in the radiation section ; iii) Red-brown brittle lumpy dust adhering to the surface of water tube installed in the radiation section and superheater at a temperature below 500℃ ; iv) Reddish powder dust collected by the cyclone ; v) White-red fine powder dust collected by the cottrell. Fig.2 illustrates the mechanism of the formation of black or greyish dust accretion, (ii) above, on the water tube of the partition wall in the radiation section. The lumpy dust formed at a relatively low texnperature, (iii) above, is similar to the cyclone or cottrell dust, (iv) or (v) above, in their composition, i.e., copper, lead and zinc are mainly of sulfate, whereas most part of iron is hematite. Photo.1 illustrates the microscopicstructure of the accretion of i) above. Principal crystallite is magnetite connected with high silica glassy material, and a considerable amount of white metal is coexisted with such magnetite to form the accretion. Judging from the small lead content, fusible material seems to drop after acting as the binder. Photo.2 shows the microscopicstructure of relatively brittle black accretion, (ii) above, which is consisted of Cu_2S-PbS eutectic and small-sized magnetite crystallites connected loosely with lead silicate glass. Photo.3 illustrates the similar but hard accretion formed at a high temperature. Because of the oxidation of PbS, sulfide phase consists mainly of copper sulfide. The compositions determined by the EPMA analysis carried out on the magnetite and silicate glass are shown in Table 2. Complicated changes are observed when such black accretion is oxidized in the atmosphere of the radiation section. Metallic copper, cuprous oxide, copper ferrite and magnetite are connected mutually by the glassy material containing lead (see Photos. 4 and 5). Compositions of each of the phases are shown in Table 3. In the brittle accretion oxidized at a low temperature, existence of basic sulfate of lead is also confirmed (see Photo. 4). Because of the high volatility, the low melting point and sticky character of lead containing phases such as PbO-SiO_2,PbO-PbSO_4 and PbS-Cu_2S, lead content in the copper concentrates give rise to a large influence upon the character of the boiler dust produced during the flash smelting. In order to avoid the boiler trouble in the smelting of lead containing concentrate, it seems to be critical that the design, engineering and operation of the boiler must be suitable to maintain the temperature of radiation section of boiler at fairly low level.
1974-03-28

<報文>黒鉱系銅精鉱の溶錬産出物に関する研究(第3報) : 自溶炉ボイラ煙灰の組織について

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