Carbon capture from a cement plant

Dear can1043 !

Without the concept of and chemical reactions underlying your proposal, it is not entirely clear. If you can provide, please concept and chemical reactions with the calculation of enthalpy and Gibbs energy. In addition, a calculation of the balance of energy and mass of the material.

With The Best Regards !

Dr. Michail A. Miheenkov

Dear Dr Miheenkov (Silastman),

I can explain the concept better.I solved mass and energy balances in a commercially available process simulator called UniSim. I did it for both reference cement plant and the proposed configuration.

In the proposed design, limestone and clay are fed into two different preheaters. The flue gases heat them up to ~750 C. Only partially calcined limestone is fed to a calciner at 930 C in which I assumed full calcination. The calciner is coupled with a circulating fluidized bed combustor which operates at 1050 C. There is no combustion in the calciner but in the combustor. Solids from the combustor (97 wt% CaO) are circulated back to the calciner and provide heat required in this reactor. The only reaction occurring in this CFB system is the calcination reaction.

The CaO leaving the calciner is mixed with preheater clay and sent to the kiln. All the clinkerization reactions, the formation of alite, belite, aluminate and ferrite, are completed in the kiln. This is the concept which provides up to 56% CO2 avoidance from a cement plant with same amount of total thermal energy requirement with the reference cement plant.

I was asking, first of all, the comments of experts. I did mass and energy balances already and may publish them if we feel that it works. What is not clear for me the clinker chemistry. In the reference cement plant, I normally assume that partial belite formation occurs in the last stage of the preheater and calciner but in the proposed design the limestone and clay are mixed after the calciner. Will it affect the clinker composition significantly? Thanks.

Regards

From the basics of Thermodynamics the reaction of formation of belit in  mixture is  happens when the temperature at which it is possible (Gibbs energy is negative). If the mixture is heat up to that temperature in the kiln, the belit and other minerals of  cement clinker also emerge in the kiln. More fundamentally, the amount of heat required to remove CO2 from pure CaCO3 more than in mixed with clay. Also it is not clear what reduced CO2 emissions. Regardless, you burn pure CaCO3 or burn it mix with clay, at equal quantity CaCO3 , the same quantity CO2 will be allocated.

.