Mathematical modeling of an in-line low-NOx calciner

• Published in: Chemical engineering science 2002-03, Vol.57 (5), p.805-820
• Main Authors: ILIUTA, I, DAM-JOHANSEN, K, JENSEN, L. S
• Format: Article
• Language: English
• Subjects: Air pollution caused by fuel industries; Applied sciences; Atmospheric pollution; Buildings. Public works; Cement concrete constituents; Cements; Combustion and energy production; Combustion regulation; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Materials; Pollution; Pollution reduction; Prevention and purification methods; Safety, energy, plant environment
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/S0009-2509(01)00420-1

The reduction of the NO(subx) content in in-line calciner kiln systems can be made by optimizing the primary firing in the rotary kiln and the secondary firing in the calciner. Because calciner optimization offers greater opportunities the mathematical modelling of this reactor is very important. A heterogeneous, dynamic mathematical model for an in-line low-NO(subx) calciner based on non-isothermal diffusion-reaction models for char combustion and limestone calcination has been developed. In particular, the importance of the rate at which preheated combustion air was mixed into the main flow was studied. Results indicate that the external heat and mass transfer to the char particles is not limiting. Internal diffusion of O2, CO, NO and CO2 is important especially in the reducing zone and the first part of the oxidizing zone and the internal heat transport limitation is significant for the endothermic limestone calcination. The rate at which preheated combustion air is mixed into the main flow directly influences the coal combustion rate, and thereby through the rate of heat release from combustion, it also influences the calcination rate and the temperature profile. The mixing rate influences the CO concentration and the overall degree of fuel-N to NO conversion. (Original abstract - amended)