Search results
Results from the WOW.Com Content Network
The rotary kiln was invented in 1873 by Frederick Ransome. [1] He filed several patents in 1885-1887, but his experiments with the idea were not a commercial success. Nevertheless, his designs provided the basis for successful kilns in the US from 1891, subsequently emulated worldwide.
The Waelz process is a method of recovering zinc and other relatively low boiling point metals from metallurgical waste (typically electric arc furnace flue dust) and other recycled materials using a rotary kiln (waelz kiln). The zinc enriched product is referred to as waelz oxide, and the reduced zinc by product as waelz slag.
Reduction is performed in a rotary kiln with pseudobrookite (Fe 2 O 3.TiO 2), coal, and sulfur, then heated to a temperature greater than 1200 °C. [11] The iron oxide in the mineral grains is reduced to metallic iron to produce reduced ilmenite: Fe 2 O 3 ·TiO 2 + 3 CO → 2 Fe + TiO 2 + 3 CO 2
The rotary kiln's maximum temperature ranges between 1,230 and 1,260 °C, which significantly exceeds the 1,000 to 1,050 °C threshold for iron oxide reduction. The main objective is to achieve a paste-like consistency of the ore gangue. [21] The reduced iron agglomerates into 3 to 8 mm metal nodules called Luppen.
It is therefore usual to simultaneously dry and grind the materials in the rawmill. A hot-air furnace may be used to supply this heat, but usually hot waste gases from the kiln are used. For this reason, the rawmill is usually placed close to the kiln preheater. Types of dry rawmill include ball mills, roller mills and hammer mills.
A trommel screen, also known as a rotary screen, is a mechanical screening machine used to separate materials, mainly in the mineral and solid-waste processing industries. [1] It consists of a perforated cylindrical drum that is normally elevated at an angle at the feed end. [ 2 ]
PAHs (according to EPA 610) in the exhaust gas of rotary kilns usually appear at a distribution dominated by naphthalene, which accounts for a share of more than 90% by mass. The rotary kiln systems of the cement industry destroy virtually completely the PAHs input via fuels. Emissions are generated from organic constituents in the raw material.
The multiple hearth furnaces consist of several circular hearths or kilns superimposed on each other. Material is fed from the top and is moved by the action of rotating "rabble arms", and the revolving mechanical rabbles attached to the arms move over the surface of each hearth to continuously shift the ore.