A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 2 3 2 0 As new materials are developed and introduced across the industrial landscape, the number of related high-temperature processes is experiencing parallel growth. Traditionally, drying ovens and rotary kilns are often used for high temperatures. However, the dynamic processes found in horizontal contact dryers can offer significant advantages in terms of product quality, energy efficiency, and emissions. Two examples include the production of high-performance silicon carbide and recycling of rare earth materials. When it comes to the processing of minerals, the recycling of lamps, batteries, or photovoltaic cells, or the pyrolysis of biomass, the right high-temperature processes are critical to ensuring reliable results. In addition, these processes must meet stringent quality standards in terms of product and throughput, produce minimal emissions, and maximize energy and resource use. Thermophysical and thermochemical processes such as combustion, calcination, thermal cracking, gasification, and even smelting are typically carried out in industrial plants featuring kilns, rotary kilns, or drying ovens. However, these processes require significant energy use and product quality can sometimes be compromised due to the uneven nature of the treatment regimen. The dynamic process of contact drying, on the other hand, makes it possible to treat bulk materials, filter cakes, or sludge more efficiently and evenly. In addition, contact drying equipment can easily be integrated into various production setups and plant floor layouts. CONTACT DRYING DETAILS During contact drying, the relevant raw material is separated into a solid anda liquid condensate. Inone example of this type of equipment, temperatures up to 1200°F can be achieved by the reactors and high-temperature dryers from BHS-Sonthofen, Germany. The machines are manufactured based on careful calculations using the finite element method and made of high- temperature steel to withstand consistently high loads. In conventional high-temperature ovens, the product is not agitated, leading to uneven drying. As a result, the process cannot be precisely controlled. In high-temperature processes, however, the temperature of each particle plays a key role. If the temperature deviates at all, the product must be discarded. By contrast, the continuous homogenization that takes place in a contact dryer means that the time and required product temperature are always precisely controlled, resulting in higher product quality and lower scrap. The special feature of the dynamic process in contact dryers is the continuous mixing that occurs for the full duration of the process. In other words, by combining the steps of heating and mixing, a fully homogeneous product TECHNICAL SPOTLIGHT FEATURES ANDBENEFITSOF HORIZONTAL CONTACT DRYING The dynamic, high-temperature process of horizontal contact drying makes it possible to treat bulk materials more efficiently and evenly than traditional drying ovens and rotary kilns. Horizontal dryer used to calcinate minerals. All images courtesy of BHS-Sonthofen.
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