4 research outputs found
Electrified calciner concept for CO2 capture in pyro-processing of a dry process cement plant
No full textAround two-thirds of the CO2 emission from the cement industry comes from calcite decomposition (CaCO3 → CaO + CO2), and most of this reaction happens in the calciner. So, it is possible to reduce the CO2 emission significantly by electrifying the calciner. This possibility is studied in this work through a process simulation model using Aspen Plus. The model is first calibrated with experimental results for a cement calciner heated by coal firing. The validated model is then electrified with three scenarios of gas recycling. Electrifying an existing calciner will require high gas recycling, while some alternative designs require no gas recycling. The results indicate that this method could reduce the CO2 emissions by as much as 78%. The total energy (including fans, calciner and kiln) required in the coal-fired calciner system is around 138 MW. The energy in the electrified system may vary between 154 MW for high gas recycling and 137 MW for no gas recycling. The net excess energy in the electrified calciner per captured CO2 unit varies between 0.6 MJ/kgCO2 for high gas recycling and -0.04 MJ/kgCO2 for no gas recycling.publishedVersio
Novel design of a rotary calciner internally heated with electrical axial heaters: Experiments and modelling
No full textAs the share of renewable energy increases, green electricity may help reduce the carbon footprint in the lime industry. Electrifying the calciner can produce relatively pure CO2 from the calcination process (CaCO3 → CaO + CO2), which may be utilized or stored. All the previous literature studied electrically heated rotary calciner with external heating. This work presents a novel design of an electrical rotary calciner through which internal heating is possible. The design can utilize existing kiln drums made from relatively inexpensive refractory and steel materials. The designed calciner operated smoothly for around four days, and the concept was technically feasible. The outer wall temperature and calcination degree was measured during the condition of a pseudo-steady state in the calciner. A model was developed and implemented in OpenModelica, which was validated by comparing it against measured variables. The modelling results revealed that the current setup had low thermal efficiency, as the heat loss amounted to around 60%, and the average heat transfer coefficient was around 101 W/(m²K). A step-by-step procedure with the help of the model was discussed to improve heat efficiency and reduce heat loss by up to 11% by improving thermal insulation and increasing the residence time of particles. With the improved thermal efficiency, energy intensity and electricity cost per unit CO2 were reduced from 35 to 7 MJ/kg-CO2 and 4.9 to 1 NOK/kg-CO2, respectively. So, improving thermal efficiency can improve both the environmental and economic aspect of the process.publishedVersio
CPFD simulation of an electrically heated fluidized bed calciner with binary particles
No full textElectrifying a calciner with clean energy can cut fuel emissions and produce a stream of relatively pure CO2 from the calcination reaction (CaCO3 → CaO + CO2), which can be utilized or stored. A fluidized bed calciner offers a high heat transfer coefficient and requires low gas flow rates for operation. The design of such a reactor is studied in this work. It is not possible to fluidize raw meal directly, so a binary mixture of coarse lime particles and fine raw meal is used. The commercial Barracuda CPFD software is applied. The model was first validated against experimental results and then used to find an optimized design. The results indicate that the suggested pilot-scale fluidized bed calciner can operate between 10 and 16 t/h of raw meal feeding with a calcination degree above 90% and with negligible coarse particle entrainment. The calciner needs 0.05–0.09 kg-CO2/kg-raw-meal for the operation, so the required gas recycling is low. Overall the calciner operation is smooth, and such a design could be used for electrification combined with CCUS.publishedVersio
