Lead blast furnace slags

BeU, R C, Turner, G H and Peters, E, 1955. Fuming of zinc from lead blast furnace slags, J of Metals, March, p472. 

Itoh, U, Yamakita, T and Yoneoka, Y, 1980. The recovery of PW zinc from lead blast furnace slags by electro-thermic process at Chigirishima smelter of Toho Zinc Co Ltd, in Proceedings Australia/Japan Extractive Metallurgy Symposium, pp 313-319 (The Australasian Institute of Mining and Metallurgy Melbourne). 

Where lower antimony slags are processed and recovery is not a critical issue, then more typical lead blast furnace slags can be used. Where feed has a significant sulfur content, iron can be added to capture the sulfur as a matte, and in this case relatively high iron slags can be produced with Fe0 Si02 ratios above 2.0 and Ca0 Si02 ratios below 0.5. 

Zinc Zinc is processed very similarly to copper and lead. The zinc is bound in the ore as ZnS, sphalerite. Zinc is also obtained as an impurity from lead smelting, in which it is recovered from the blast furnace slag. 

At some plants the blast furnace dust is recycled as feedstock to the sinter plant. At plants without sintering operations, blast furnace dust is sometimes mixed with other byproduct residues, briquetted, and recycled back to the blast furnace. In other plants, the dust is landfilled or stockpiled.1 Several techniques are available for removing the zinc and lead. The majority of blast furnace sludge is land disposed as solid waste or stockpiled. Because of the similarity between wastewater sludges generated by sinter plants and blast furnaces, these streams are commingled and cotreated.1 The blast furnace slag is cooled and processed to be reused for various applications such as onsite in-land reclamation and landfill construction. 

As mentioned above, approximately 7% of the total sulfur present in lead ore is emitted as S02. The remainder is captured by the blast furnace slag. The blast furnace slag is composed primarily of iron and silicon oxides, as well as aluminum and calcium oxides. Other metals may also be present in smaller amounts, including antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, lead, manganese, mercury, molybdenum, silver, and zinc. This blast furnace slag is either recycled back into the process or disposed of in piles on site. About 50 to 60% of the recovery furnace output is slag and residual lead, which are both returned to the blast furnace. The remainder of this dross furnace output is sold to copper smelters for recovery of the copper and other precious metals. 

Sugar Beet Pulp" Calcium Carbonate Blast Furnace Slag" Lead b Concentrate Sandb Zinc Concentrate Ammonium Sulphate" Fine Salt" Crystals Chemicals"... 

Sugar Beet Pulp Calcium Carbonate Blast Furnace Slag Lead Concentrate Sand Zina Concentrate ° Ammonium Sulphate Fine Salt Crystals Chemicals ... 

Utilization of different blended cements leads to the highest reduction of the CO2 emissions during the cement production. This is realised by replacement of a portion of clinker in cement by granulated materials. Blast-furnace slag, fly ash with accelerators were used as additive materials. Practical decrease of the CO2 emissions from both fuel and raw material can reach a reduction by 50% or even more [5]. 

In non-carbonated and chloride-free concrete, the concentration of hydroxyl ions (OH ) varies from 0.1 M to 0.9 M, due to the presence of both NaOH and KOH (the latter is predominant, especially in Portland cement). Other ions, e. g. Ca and S04 , are present only in very low concentrations. Addition of blast furnace slag or fly ash to Portland cement results in a moderate reduction of ionic concentration, and thus in pH. From hydroxyl ion concentrations in Table 2.1, values of pH of 13.4-13.9 can be calculated for Portland cement, and pH values of 13.0-13.5 for blended cements. Addition of condensed silica fume in higher percentages may lead to a decrease in the pH to values to below 13 [4, 10]. 

CO2 (molecular weight 44) that can react with a concrete produced with 300 kg/m Portland cement that we can suppose is composed by 64% of CaO (molecular weight 56) is 300 X 0.64 X 44/56 150 kg/m. In the case of blast furnace slag cement with 70 % of GGBS, the percentage of CaO is only 44%. For other blended cements, the quantity of CaO is somewhere between these two values [3]. For blended cement, hydration of pozzolanic materials or GGBS also leads to a lower Ca(OH)2 content in the hardened cement paste which may increase the carbonation... 

None of the furnaces operated with oxygen enriched blast air. Because of the stronger adjusted reduction potential, the lead concentration in the final slag, which is equal to or less than 1.5%, is lower compared to that of blast furnace slags. 

The production laboratory at the Herculaneum smelter performs quality analytical work for all the processes. The laboratory equipment includes a spark emission spectrophotometer, inductively coupled plasma atomic emission spectrometer, wavelength dispersive X-ray fluorescence spectrometer, sulfur analysis equipment, and wet chemistry equipment. The laboratory conducts the analysis for all process materials, including sinter, blast furnace slag, lead bullion, all finished lead products, and environmental samples. 

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