From Coal to Natural Gas: Its Impact on Kiln Production, Clinker Quality, and Emissions

PROJECT TITLE :

From Coal to Natural Gas: Its Impact on Kiln Production, Clinker Quality, and Emissions

ABSTRACT:

In the North American energy market, natural gas (NG) prices have been gradually decreasing during the past several years, primarily because of advances in shale gas extraction techniques. The availability of cheaper NG, whereas seen as an attractive short-term fuel switching choice, is viewed with caution by most cement plants due to long-term procurement considerations. Conjointly, because of traditionally higher NG costs, cement plants have invested heavily into solid fuels, together with storage, grinding, handling, and dosing systems-often achieving high thermal substitution rates (TSRs) of solid alternative fuels and raw materials (AFRs). So, a wealth of knowledge has been acquired on firing solid fuels, as well as some of the a lot of tough ones, e.g., higher sulfur petcoke and larger size AFRs, where operational issues like build-ups, emissions, and production losses are and are being minimized. Switching to gas firing, however, requires readaptation of combustion and method tips for a fuel that, though in principal, is easier to burn, however has relatively lower radiative heat transfer and sharper burning characteristics than coal. As such, the plants, which have switched to NG firing, have observed inconsistent trends in production, energy, and emission performance, mainly due to the lack of sufficient data on combustion/method interactions of the 2 fuel types needed for cost-effective optimization. An NG flame ignites earlier, releases intense heat however lacks dissipation of heat as compared with a solid fuel flame, thereby requires plant specific adjustments. This paper presents actual results of NG firing trials at selected cement plants along with mineral interactive computational fluid dynamics (MI-CFD) predictions, after validation from the plant knowledge, on four kiln and four calciners. Recommendations are created to improve and optimize NG firing by taking into issues of the combustion and mineral interactions.

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