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Similarity rules for rotary kiln scale-up
Published in Y. Kishino, Powders and Grains 2001, 2020
Y.L. Ding, H.P. Kuo, A.S. Burbidge, J.P.K. Seville
Solids processing such as iron oxide reduction, limestone calcination and even waste incineration often utilises of rotary kilns. However, scale-up methodology for such devices is still largely empirical and no general method has been established. One of the most difficult issues in the establishment of the scaling rules lies in the complexity of the modes of solids motion. Six modes of bed movement have been observed (Rutgers 1965, Henein et al. 1983). With increasing rotational speed, these are slipping, slumping, rolling, cascading, cataracting, and centrifuging modes. Although the Froude number and kiln fill percentage have been proposed to describe the transitions between these modes (Henein et al. 1983), it is expected that other factors such as the rheological properties of the particles and the physical properties of the kiln wall also have some influence.
Ceramics
Published in William Bolton, R.A. Higgins, Materials for Engineers and Technicians, 2020
A number of different types of cement exist, but possibly the best known and certainly the most widely used is Portland cement, so named in 1824 by its developer Joseph Aspdin since it resembles Portland stone (a white limestone from the Isle of Portland). The principal ingredients are ordinary limestone – or even dredged sea shells – and clay-bearing materials comprising suitable clays or shales. The raw materials are pulverised separately and then mixed in the correct chemical proportions before being fed as a paste into a long rotary kiln where the mixture is calcined at 1500°C. The resultant ‘clinker’ is then ground along with a small amount of gypsum (calcium sulphate) to produce the fine greenish-grey powder – the well-known Portland cement – a typical composition of which is given in Table 21.4.
General Types of Contaminated Site Restoration Methods and Technologies
Published in Kofi Asante-Duah, Management of Contaminated Site Problems, 2019
The rotary kiln is a refractory-lined, slightly inclined, rotating cylinder that serves as a combustion chamber, and operates at temperatures up to 980°C (1,800°F). Typically, commercial incinerator designs consist of rotary kilns, equipped with an afterburner, a quench, and an air pollution control system.
A mathematical model of a twin-shaft parallel flow regenerative lime kiln
Published in Mineral Processing and Extractive Metallurgy, 2023
Sujit A. Jagnade, Saurabh K. Nayak, Jose M. Korath, Nurni N. Viswanathan, Prakash B. Abhale
Many researchers have investigated the kinetics of different limestones to improve the energy efficiency, productivity, and the product quality in various types of lime kilns (Borgwardt 1985; Ar and Doğu 2001; Feng and Lombardo 2002). Thus, the design of kilns and their operation has evolved from primitive batch kilns to sophisticated continuous kilns in the last 50 years. Several types of kilns are use used such as annular shaft with recuperator, short rotary kiln with preheater, long rotary kiln without preheater, high-performance shaft, mixed feed type, twin shaft parallel flow regenerative (PFR) kiln, etc. Various industries use these kilns based on the raw material available, product quality required (reactivity and degree of calcination), types of fuel available, and energy consumption. A comparative study has been carried out by Piringer (2017) wherein he compared the advantages of modern shaft kilns with other kilns and explained the functioning principles of each type of kiln.
Thermal imaging as a tool for process modelling: application to a flight rotary kiln
Published in Quantitative InfraRed Thermography Journal, 2020
The rotary kiln is widely used for the thermal treatment of granular materials, including drying, gasification, heating, pyrolysis, sintering, calcination, roasting and cooling, within various industries. Slightly inclined, a hollow cylindrical apparatus rotates around its central axis. The dimensions can reach 230 m long by up to a 7-m inner diameter. The temperature range of these processes extends from 100 to 2000°C, with the kilns capable of being heated either directly (from the inside) or indirectly (from the outside). The carbon footprint of these facilities is to be considered as non-negligible, as is the case encountered in the cement production sector where wall heat losses can account for 61% of the total energy losses [1]. To limit energy consumption from the temperature controller, two technological limitations must be overcome first, namely the rotational motion of the drum and the extensive temperature range encountered in such systems.
Modeling operational cement rotary kiln variables with explainable artificial intelligence methods – a “conscious lab” development
Published in Particulate Science and Technology, 2023
Rasoul Fatahi, Hamid Nasiri, Arman Homafar, Rasoul Khosravi, Hossein Siavoshi, Saeed Chehreh Chelgani
For exploring the relationships between kiln feed rate, and ID fan speed, and other operating variables, a dataset was collected from one of the pre-heater and rotary kiln (Clinker Baking unit) circuits (line 1) in the Ilam cement plant (Figure 1). The Ilam plant has two lines for cement production (5,300 t/d). The clinker baking circuit includes a pre-heater unit, five air cyclones, and one calcinator) up to 900 °C for calcination (and rotary kiln (62 m length,4.2 m diameter) with 2,000 t/d capacity (made by O&K Company from Germany). The maximum kiln’s rotation speed is 3 rpm. The plant has approximately a fixed one-year period for the overhaul. The pre-heater and rotary kiln key operating parameters are summarized in Table 1. Variables were monitored hourly and were taken into account. In general, over 3,000 records from 2020 to 2021 were prepared and used for the modeling. In the plant, before the introduction in the rotary kiln, the raw meal is pre-heated through a suspension pre-heater. The pre-heated material is up in the air with the combustion exhaust gas from the kiln. In the suspension pre-heater, composed of five cyclones stages, the heat transfer rate increases, which enhances the heat exchange efficiency combustion from the kiln, which flows through the cyclones from the bottom upwards. Raw meal, finely milled, is mixed with the exhaust gas upstream. A rotary kiln is a steel cylinder that rotates around its axis. The kiln is horizontally sloped at about 2.5–4.5%, letting the processed mixture move along with it. The kiln fuel is introduced through a burner placed at the end of the kiln. After its entry into the furnace, Raw meal is subjected to calcination, solid-phase reactions, and clinkering.