Cement kiln

Cement kilns are mechanical, industrial furnace used for the pyroprocessing stage of manufacture of portland and other types of hydraulic cement. The kilns use high heat to cook calcium carbonate with silica-bearing minerals to create the more reactive mixture of calcium silicates, called clinker, which is ground into a fine powder that is the main component of cements and concretes.

Kilns are relatively distributed technologies all over the world: over a billion tonnes of cement are made per year, and cement kiln capacity defines the capacity of the cement plants. The kilns is an integrated part of the cement plant, connected by a number of ancillary pieces of equipment, used to engineer an ideal flow of cement to the rest of the system. Improvement to kiln systems and ancillary equipment, such as heat recovery, can improve the efficiency kilns and reduce the cost of overall operation of a cement plan.

Emissions from cement kilns are a major source of greenhouse gas emissions, accounting for around 2.5% of non-natural carbon emissions worldwide. The emissions come from two sources: the fuel and the waste CO2 created from heating the silicate rocks. Conventional cement kilns burn fossil fuels or alternative fuels like tire waste, agricultural waste or other wastes, as a form of waste valorization. Because of the need to reduce emissions to mitigate climate change, multiple companies are investing in alternative fuel sources, including investigations of hydrogen or electricity based heating. Other mitigation approaches, include capturing carbon dioxide from the process at the exhaust stage of the kiln, and reducing use of clinker in final mix of concretes.

Kilns also produce other toxic emissions, such as particulates, sulfur dioxide, nitrogen dioxide and other industrial emissions. If not mitigated correctly at the emissions pipe, surrounding communities can have increases in air pollution.