Summary
Calciner is key equipment in Cement Production where raw material, CaCO3 is calcined at high temperature to form CaO. It is then fused with FeO, SiO2, and Al2O3 in the kiln to produce clinker. The efficiency of Calciner can be measured in terms of extent of combustion, degree of calcination of raw meal, and meeting emission norms of gaseous pollutants like NOx and SOx. The Cement industry is taking concrete steps in reducing emissions in particular. All the issues as mentioned above depend on air-fuel , hot gases-raw meal mixing, raw meal , coal residence time, and efficient heat transfer. Due to high temperatures and dusty environment in the Calciner, it is very difficult to measure local temperatures, oxygen profile etc inside the Calciner. Measurements are available at the exit of calciner in terms of NOx, SOx, Oxygen, Temperature, calcination quality and unburnt coal.
Computational Fluid Dynamics becomes a tool of choice to analyse gas-solid mixing, heat transfer and subsequent combustion, calcination and NOx formation. As the physics in the Calciner and its design is complex, It was important that we validate coal combustion model, gas-solid heterogeneous reactions (Calcination) and NOx formation. We did a detailed comparison of CFD results of coal combustion with laboratory data of IFRF Furnace, Netherlands. The detailed study included effect of mesh, turbulence model, coal combustion models and model parameters and compared with literature data. This exhaustive study gave a strong insight of combustion modeling, best practices, tricks of convergence etc. Most importantly, i gained confidence.
After the above validation study, In steps, we developed a complete Calciner model to include air-fuel -raw meal flow and mixing, coal combustion, calcination and finally NOx formation. The Calciner simulation with calcination reaction and combustion involves a lot of complexity. One of the toughest challenge was to model raw meal injection and its dispersion in Calciner. Another challenge was to model the calcination reactions. In the beginning, I modelled every physics separately in simplified, small pipe and then integrated everything in the Calciner.
While modeling detailed physics is important, equally important is to analyse the results and link them with the process issues and ofcourse, finally suggest solutions. We could analyse effect of injection location of raw meal on extent of mixing, calcination, and NOx formation.
This detailed model of the Calciner can now be applied to address multiple problem statements. To list a few
1. Replace coal with alternate fuel
2. Optimize Calciner performance in terms of fuel efficiency, raw meal calcination
3. Increase Calciner throughput
4. Reduce NOx and analyse various NOx reduction methodologies
5. Evaluate different designs and newer concepts to improve the Calciner design.
Key Issues
Calciner performance is key for cement production. Typical issues faced during the operations involve
- Inefficient fuel combustion leading to higher fuel consumption
- Incomplete Calcination leading to more load on the kiln
- High NOx: Emissions out of regulation Norms
- Reduce Coal consumption and increase the consumption of alternative fuel
Deliverable
The key deliveries for my projects
- Validated Coal combustion Model with literature
- Developed Calciner Model including Coal Combustion, Calcination and Pollutant formation.
- Suggested strategies to reduce NOx .
About the Author
Shital Mone is a Mechanical Engineer with specialization in Heat and Power. He has expertise on Coal combustion modeling in ANSYS Fluent, Gas-Solid Multiphase flows using Euler-Lagrange approach, NOx Modeling, Heat Transfer. He looks forward for a rewarding career in the field of CFD Modeling and interested in modeling combustion flows.
shitalmone@gmail.com