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Metal–Crucible Interactions
Published in Nagaiyar Krishnamurthy, Metal–Crucible Interactions, 2023
Over thousands of years of metalmaking, certain devices have evolved, in one form or another, as the key features of the smelting furnace. One is the tuyere, a pipe through which air can be forced into the smouldering coke, then the bellows or blower, an implement for forcing air into the tuyere, and the hearth, a place where the burning fuel can be contained over or against the tuyere opening. Traditionally, hearths have been built of mud-brick, fired brick, stone, or later, refractories of every description.
Sludge Disposal
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
T.F. Brown, Wayne F. Echelberger, Louis C. Glide, Béla G. Lipták, Joseph G. Rabosky, Frank P. Sebastian, John R. Snell, Michael S. Switzenbaum
Since its initial use in 1934, the multiple-hearth incineration system has become the most widely used means of ultimate sewage sludge disposal, with more than 200 installations in the United States accounting for a capacity of over 50,000 wet tons of sludge per day. Multiple-hearth process development has kept pace with the increasing concern over air pollution, odor control, and resource reuse. New developments include the use of multiple-purpose furnaces for sludge incineration and chemical reclamation.
Pyrometallurgy
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
Endako Practice:7 The Endako roasting plant, which is a part of a mine-mill complex located at Endako, British Columbia, and is owned by Canex-Placer Ltd., comprises two Nichols-Herreshoff furnaces. The first one has 10 hearths of 4.9 m diameter while the second has 12 hearths of 5.5 m diameter. The plant flowchart is shown in Figure 7. The plant intake is in the form of what is called concentrate pulp, with 3 to 9% solids. The pulp is thickened and leached with hydrochloric acid to reduce calcium levels from 0.4 to 0.04%. The leached concentrate is further washed and filtered down to 26% water and then dried to about 2.6% moisture in a 4-hearth Nichols-Herreshoff type dryer. The concentrate initially contains 2 to 3% of oil from flotation reagents. In the dryer, about half of it is vaporized and/or burnt. The two roasters have a combined production of about 18 to 19 t/d of contained molybdenum. The roasting temperature is controlled in both the roasters by adjusting the air input into each hearth. The maximum allowable temperature in the hottest hearths is near about 700°C to avoid sintering of the bed and excessive volatilization of molybdenum trioxide. Bed and gas temperature profiles7 for the two roaster units are shown in Figure 8. Normally, 15 to 20% of the feed goes into the off gases, which are cleaned in electrostatic precipitators. Off gases, after cooling, are scrubbed in two packed towers with reclaimed water from the concentrator tailing pond. The effluent from the scrubber returns to the mill tailing box where the dissolved sulfur dioxide is neutralized with an excess of calcite from the ore. Specifications3 of technical grade molybdenum trioxide produced by Endako are given in Table 3.
Emission reduction and fuel-saving potentials in jaggery industry via cleaner combustion
Published in International Journal of Ambient Energy, 2022
S. K. Tyagi, N. Tyagi, H. Himanshu, S. Kamboj, K. K. Agarwal, U. Sharma, V. V. Tyagi
Although the jaggery industry is a very old industry in India, yet the scientific interventions have been very slow in this industry due to a number of constraints including lack of policy support. The traditional jaggery production involves an open-hearth furnace leading to (a) heat transfer losses, (b) incomplete combustion of fuel, (c) poor thermal efficiency, (d) higher consumption of fuel and (e) huge emission of hazardous pollutants. The pollutants released from the furnace through a short chimney are very harmful to human health and the environment (Shiralkar et al. 2014; Smith et al. 2014). The traditional furnace design also varies from place to place and country to country; however, the overall heat utilisation efficiency is very poor and needs the scientific inputs for further improvements (Anwar 2014, 2010; Arya, Jaiswal, and Kumar 2013; Sardeshpande, Shendage, and Pillai 2010; Shiralkar et al. 2014; Singh, Bangali, and Singh 2008). In the traditional plant, furnaces are generally earthen-pit, while the size and shape depend on the number of pans starting from single to two to three pans and most recently as four-pan systems being used in a particular plant. It is obvious that the thermal performance and production capacity enhance with varying from single pan to multiple pans, but all types of plants are still under operation in India due to a number of reasons (Kamboj et al. 2021).
Blast Furnace Flue Dust as a Potential Carbon Additive in Hematite Ore Pellet
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Ammasi Ayyandurai, Jagannath Pal
From the above, it is envisaged that BFD has been used in sinter mix in form of micropellets. However, good quality micropellet making is a very difficult task. When BFD has been used as a carbon source (reducing agent) in self-reduced briquettes for either mini blast furnace or rotary hearth furnace, it reduces the cold strength of briquettes. Moreover, BFD contains high alkali and Zn which restricts its use in huge proportion in blast furnaces directly in any form, therefore, it has been used as a coolant in BOF in form of briquettes. However, there is no study on the use of BFD as a C source in hematite ore pellet. Hematite ore pellets require only a small amount of carbon for in-situ heat generation and enhancing diffusion bonding during induration. Therefore, a small amount of BFD is required as a C source, whose alkali and Zn input will be very minor. Alkali and zinc oxides may also evaporate during the induration of the pellet at high temperatures. Therefore, BFD may be used as a carbon source in the hematite ore pellet. This study aims at optimizing the process parameters for utilizing BFD in hematite ore pellet as a carbon source. The properties of BFD-added pellets and coke-added pellets have been compared and alkalis and Zn in pellet have been analyzed and discussed in this study.
Toward an on-line characterization of kaolin calcination process using short-wave infrared spectroscopy
Published in Mineral Processing and Extractive Metallurgy Review, 2018
A. Guatame-García, M. Buxton, F. Deon, C. Lievens, C. Hecker
The present study raises the possibility of using SWIR spectroscopy as a technique for the monitoring and control of calcined kaolin process. The results presented in this work, offer the criteria needed to refine the Kx and 1900D parameters and transform them into a tool capable of quantifying the amount of soluble Al2O3. For this, specific Kx and 1900D thresholds that comply with the optimum soluble Al2O3 values must be determined. Besides, the conditions for the implementation of an on-line analysis system should also be considered. In a kaolin processing plant, the calcination is performed in a Multiple Hearth Furnace, in which the temperature increases from hearth to hearth. The on-line spectral analysis would ideally be implemented by taking measurements of the feed for the calciner and at every hearth to track the evolution of the kaolin transformation sequence and establish the optimum point for the desired product.