Model Based Flowsheet Studies on Cement Clinker Production Processes

Clinker is the main constituent of cement, produced in the pyroprocessing section of the cement plant. This comprises some high temperature and carbon intensive processes, which are responsible for the vast majority of the CO2 emissions associated with cement production. This paper presents first-principles mathematical models for the simulation of the pyroprocess section; more specifically the preheating cyclones, the calciner and the rotary kiln. The models incorporate material and energy balances, the major heat and mass transport phenomena, reaction kinetics and thermodynamic property estimation models. These mathematical formulations are implemented in the gPROMS® Advanced Process Modelling Environment and the resulting index-1 DAE (Differential Algebraic Equation) system can be numerically solved for various reactor geometries and operating conditions. The process models developed for each unit are then used to build a cement pyroprocess flowsheet model. The flowsheet model is validated against published data, demonstrating the ability to predict accurately operating temperatures, degree of calcination, gas and solid compositions, fuel consumption and overall CO2 emissions. The substitution of conventional coal with more sustainable fuels is also investigated, to evaluate the potential for avoiding CO2 emissions by replacing part of the fossil-based coal fuel (used as a reference case). Trade-offs between different process KPIs (f.e. calcination efficiency, specific CO2 emissions per tonne of clinker) are identified and evaluated for each fuel utilization scenario