Hot air dryer Direct

convectionconductionrotary

GRELBEX direct rotary kilns allow for the industrial calcination and chemical reaction of all types of powdered solids by bringing them into contact with hot gases. They are designed to guarantee reliable operation, low maintenance, maximum efficiency, and high industrial availability. These criteria make our kilns a wise choice for drying powdered solids. OPERATION Rotary kilns consist of a cylinder (a "drum" or "shell") that rotates slowly and steadily on two supports (bands). This cylinder is driven by an electric or hydraulic motor, by the action of a pinion on a toothed wheel, or by a chain. The wet product is introduced from one side or the other of the shell (depending on whether it operates in a co-current or counter-current configuration). At the inlet of this cylinder is a generator that distributes a uniform flow of hot air at a temperature defined by the process. As the shell rotates, the product slowly advances and comes into contact with the hot air (which flows in either a co-current or counter-current flow). As it is agitated, the product absorbs energy and either calcines or reacts. These kilns are suitable for varying throughputs (from a few hundred kg to several tens of tons per hour), high processing temperatures (from 300 to over 1400°C), and can process solids with varying particle sizes. It is also important to optimize this equipment. Numerous options exist for partially recovering energy from the calcining airflow after the process (partial recycling, condensation, cooling, separation, etc.). APPLICATIONS Construction materials industry • Production of quicklime (CaO) from limestone (CaCO₃). • Calcination of clays, dolomite, magnesia, or bauxite. • Heat treatment of refractory or ceramic materials. • Production of metal oxides (Fe₂O₃, Al₂O₃, TiO₂, ZnO, etc.). Advantage: high thermal efficiency, robustness, and large capacity. Mining Industry • Calcination of metal concentrates (nickel, copper, manganese, etc.). • Roasting of sulfide ores (e.g., ZnS → ZnO + SO₂). • Regeneration of metal dust or recycled oxides. • Production of ferroalloys or pretreatment before melting. Advantage: possibility of using solid, liquid, or gaseous fuels and operating in a controlled atmosphere. Chemical Industry • Thermal decomposition of carbonates, sulfates, or hydroxides. • Drying and calcination of solid chemicals (alum, gypsum, phosphates, etc.). • Regeneration of spent catalysts or active supports. • Production of pigments or chemical oxides at high temperatures. Advantage: temperature flexibility (200 to 1600 °C) and the ability to combine chemical reactions and heat transfer. Energy recovery and the environment • Incineration of hazardous industrial waste (solids, sludge, liquids). • Pyrolysis or gasification of household waste, sludge, tires, and biomass. • Carbonization of biomass to produce biochar or activated carbon. • Thermal activation of activated carbon (with steam or CO₂). • Thermal desorption of contaminated soils (hydrocarbons, heavy metals). • Regeneration of foundry sands or activated carbon. Advantage: robustness and the possibility of recovering combustion gases for energy recovery.