A Technology of Multiple Smelting Furnaces per Termite Mound: Iron Production in Chongwe, Lusaka, Zambia

With exception of Maluma (1979) and Musambachime (2016, 2017), there have been no archaeometallurgical publications on the technology and culture of iron production in Zambia. This paper presents archaeological and archaeometallurgical evidence of a technology of iron production in Chongwe in terms of spatial organization, the process of metal production (either a three-stage process involving smelting in relatively tall furnaces, refining in miniature (vintengwe) furnaces, and smithing on a hearth or a two-stage process involving smelting and smithing), furnace air supply mechanisms, liquid slag handling techniques, variation in the geochemistry of ore and clay, and the nature of the final smelting products. Archaeological field data collection techniques included ethnoarchaeological interviews, (furnace) excavation, surface collections, and surface walkover surveys, while laboratory analytical techniques included optical microscopy (OM), scanning electron microscopy (SEM), and x-ray fluorescence (XRF). New field evidence indicates that iron production in Chongwe in the previous two centuries was secluded from respective pre-modern settlements for socio-cultural and technical reasons. There are no settlement remains in and around Chongwe smelting sites. Also, most of the archaeological data in Chongwe are supportive of the two-stage process that did not involve iron refining in vintengwe furnaces. There were no iron refining sites in Chongwe. Archaeological evidence also strongly points to the use of natural air supply mechanism for the smelting furnaces because proximal ends of tuyères inter alia were not trumpeted. All smelting sites were systematically located on termite mounds. There were three to four smelting furnaces located on the western side of a termite mound. The presence of tuyère mould slags and thin and elongated slag microstructures strongly indicates that liquid slag was tapped outside the furnace apparently through tuyères and was left to cool quickly. Presence of primary wüstite and iron particles in the slags strongly suggests the production of iron as the final smelting product in Chongwe. The results are compared with the archaeology, chemistry, and mineralogy of iron production from other parts of sub-Saharan Africa, particularly in the Lake Tanganyika-Nyasa Corridor. The presence of three to four smelting furnaces per termite mound makes iron production in Chongwe a unique technology in the Corridor.

Quality Engineering with Taguchi Loss Function Method and Improvement of Work Method in Anode Changing

One of the companies engaged in aluminum smelting product ion has problems, namely the occurrence of high variations in the removal of new anodes to the old anodes which are influenced by the operator's working method because of unnecessary movements and movements beyond the Anode Changing mechanism set by the company has become a habit of the operator itself, so the time needed to replace the anode is getting longer. This problem causes the company to suffer losses due t o the product ion process that runs not in accordance with established procedures. So, the company needs to calculate the losses incurred due to variations in anode replacement and see how the operator's working method when changing the anode that causes these variations and also has an influence on the anode replacement cycle time. The method used for this problem is Taguchi Loss Function which is used to calculate the losses suffered by the company and improve work methods using the Modular Arrangement of Predermined Time Standards (MODAPTS) method to calculate the processing time. The results obtained using this method are losses experienced by the company in Block 1 amounting to Rp 19,733,263, while the total losses in Block 2 amount to Rp 35,919,435. While for the operator's working method, the operator's work movements are analyzed which are not in accordance with the economic principles of the movement . Comparison of the standard time of actual and proposed work methods is 774.847 seconds and 648.2 seconds with a time difference of 126,647 seconds faster and there are no movements that should not be done so that the operator can use the time to adjust the anode height as well as possible according to the standards determined by the company.

Laboratory testing results of kinetics and processing technology of the polymetallic sulphide concentrate Blagojev Kamen – Serbia

This work presents the laboratory testing results of kinetics the oxidation process and sample processing of the sulphide polymetallic concentrate Blagojev Kamen. The aim of investigation is recovery of these types of raw material, present in large quantities in the peripheral parts of already used primary mineral deposits of copper, because of their high economic potential due to the content of a large number of metals and especially precious metals. Characterization of this raw material is based on the chemical analyses, XRD results, DTA analysis, etc. For these investigations, the sulphide concentrate with the following content was used in %: Cu – 2.3; Fe – 19.8; S – 27.19; Zn – 9.13; As – 0.167; Pb – 15.63; SiO2 – 17.93; CaO – 0.97; Al2O3 – 1.43; Ag – 480 g/t; Au – 659 g/t. Kinetic investigations of oxidation processes were carried out under the isothermal conditions within the temperature range of 400 to 625 oC. The Sharp's model was used for determination the kinetics parameters, and determined values of activation energy are 67 kJ/mole for the first period, and 47 kJ/mole for the second period. Pyrometallurgical treatment of this type of polymetallic concentrate, in the laboratory conditions, was carried out using the oxidative roasting and, then the reduction smelting was done in the Taman's furnace. Gold from 90.5 to 97.95% and silver from 77.28 to 93.37% are moved into the raw lead (smelting product). Gold from 1.1 to 3.92% and silver from 4.35 to 8.42% are moved into the polymetallic copper matte. Gold from 0.58 to 1.6% and silver from 2.45 to 6.82% are moved into the slag.