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Gas-Solid Noncatalytic Reactions
Published in James J. Carberry, Arvind Varma, Chemical Reaction and Reactor Engineering, 2020
L. K. Doraiswamy, B. D. Kulkarni
The foremost consideration in the analysis and design of these systems is the mode of contact. The number of reactor types (or modes of contact) is very large in the chemical industry. Even for the same operation, for example, calcination of lime, different types of reactors (e.g., rotary kiln, flat hearth, fluidized bed, moving bed) are used. A similar situation prevails in many other gas-solid reactions involving calcination, decomposition, roasting, and so on. The fixed-, fluidized-, and moving-bed techniques appear to be most commonly employed and have received greater attention from both the theoretical and practical points of view. The other modes of contact, less commonly employed, include horizontal moving bed, pneumatic conveyor, rotating cylinder, and flat hearth furnace. Although a priori selection of the mode of contact is difficult, a choice will have to be made at as early a stage as possible—certainly before any significant effort is put into the detailed design.
Phosphate Fertilizer Recycling and Recovery from Phosphate Mine and Mining Waste
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
Hossain Md Anawar, Golam Ahmed, Vladimir Strezov
Open-pit phosphate mining, rather than subsurface mining, is the most common method. Different separation processes are used to separate phosphate from other minerals. The chemical quality and grade of phosphate feedstocks can be improved by removing impurities such as toxic, radioactive and rare-earth elements. Selective mining to bypass the difficult-to-process portions and the lack of instantaneous information on deposits causes recovery loss. Application of laser based analytical tools for phosphate mining and beneficiation can reduce phosphate loss significantly in the mining process. The phosphate ores are calcined for their purification. However, this process has several drawbacks: the high capital cost of calcination plants, the energy extensive nature of the operation, the low reactivity of products and gypsum filtration rate. Froth flotation is used widely for upgrading raw phosphate. Significant improvement in recovery of coarse phosphate flotation was achieved using cavitation-generated nanobubble. The conventional phosphate flotation process is the “Crago” flotation technique that involves a cationic–anionic sequence of operations. The modified technique called reverse Crago (amine-fatty acid) flotation is more efficient and has many more economic benefits than the traditional Crago flotation technique.
Elastomer-Based Composite Materials Comprising Calcined Kaolin
Published in Nikolay Dishovsky, Mihail Mihaylov, Elastomer-Based Composite Materials, 2018
Nikolay Dishovsky, Mihail Mihaylov
The investigations in Section 10.3.10 were performed on kaolin calcined under factory conditions of Kaolin Ltd., Bulgaria. The calcination was carried out in a rotating furnace in a non-stop regime which had the following parameters: length—60 m; diameter—3 m; slope—3.5°; rotation speed— 0.64-1.23 min−1. Calcination temperature was in the optimal temperature range established experimentally—500°C.
Comparative characteristics assessment of calcined and uncalcined agro-based waste ash with GGBS and its application in an alkali-activated binder system
Published in Cogent Engineering, 2023
S Blesson, A U Rao, R P Bhandary, P P Shetty, Blessen Skariah Thomas
The properties of the binder system prepared using agricultural and industrial waste ashes vary depending on whether the waste ashes are calcined or uncalcined (Tantri et al., (2022). Calcination is an a thermal treatment process used to remove volatile matter from materials such as ceramics, metals, and minerals. During this process, the material is heated to a high temperature, causing the bond between the binder and the material to break down (Alla & Asadi, 2022). Under 700°C regulated burning (calcination) of agro-based waste products, the ash’s silica content is converted into amorphous silica, which can then be utilized as a pozzolanic material (Singh et al., 2000). Aluminosilicates fail to react with water or do so extremely slowly. However, if these materials have significant amorphous content, they will hydrolyze and condense in an alkaline environment, creating new inorganic polymers with a load-bearing capacity (Habert, 2014).
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
For industrial applications, natural kaolin clay is heated to temperatures above 900°C. The purpose of this thermal treatment, also known as calcination, is to modify the chemical and physical properties and to enhance the value of the raw material. During the calcination, kaolinite [Al2Si2O5(OH)4], which is the main constituent in kaolin, is transformed first into metakaolinite [Al2Si2O7] and further into mullite [Al2SiO8]. The industrial interest on calcined kaolin depends on the chemical and physical properties of the intermediate phases produced at various calcination stages. For example, the highly disordered and reactive metakaolinite is used as a pozzolanic additive in the cement industry. For other uses, such as in the pharmaceutical industry, the calcination time is increased to reduce the metakaolinite chemical reactivity and enhance the whiteness, yet keeping low abrasiveness (Thomas et al. 2009). The high-temperature mullite phase is whiter than metakaolinite, but highly abrasive, which is detrimental for the targeted markets. In order to ensure the production of calcined kaolin with optimum properties, the quality control strategies should involve techniques that enable a quick turnaround for timely operational feedback. It is then required that such techniques can be used in an on-line production environment and generate (near) real-time data. However, the study of calcined kaolin in the industry has focused mostly on product development rather than in the monitoring and control of the calcination process.
Red Mud: Fundamentals and New Avenues for Utilization
Published in Mineral Processing and Extractive Metallurgy Review, 2021
The solid product from precipitation is fed into the calciner to drive off moisture and yield solid alumina (Al2O3). Calcination of alumina is performed using rotary kilns, fluidized bed calciners, or other similar technologies. The chemical reaction of calcining aluminum hydroxide can be seen in Equation 8 (Hind, Suresh and Grocott 1999).