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A novel process scheme for energy production from coal with in situ sulfur capture, known as the coal-direct chemical looping process with sulfur removal (CDCL-SR), is proposed in this study. The proposed process utilizes multimetal oxide comprising the oxides of copper and calcium supported on inert SiC as the oxygen carrier to combust coal and simultaneously produce separate streams of CO2 and SO2, thus eliminating the need for downstream processing units. The computational software ASPEN Plus has been utilized to carry out detailed reactor simulations along with a thorough thermodynamic analysis of the process. The reactor modeling results indicate that the moving bed reducer can effectively convert all the carbon present in coal into CO2 while capturing sulfur in the form of calcium sulfide in the reduced oxygen carrier. The reduced oxygen carrier can in turn be oxidized using steam to produce pure SO2 stream that can be readily utilized. Process simulation results indicate that the proposed CDCL-SR process has thermal and exergy efficiencies of 86 and 51%, respectively, significantly higher than both the conventional pulverized coal Rankine cycle and Fe-based CDCL processes.

We present a novel low-temperature chemical looping combustion scheme for simultaneous natural gas conversion into a sequestration-ready CO2 stream and NO x purification. The scheme employs nickel oxide (NiO) supported on ZrO2 as the oxygen carrier. In the process, CH4 reduces the oxidized carrier to Ni/ZrO2 in a co-current moving bed reactor, which is then oxidized back to NiO/ZrO2 by the NO x -laden flue gas in a fluidized bed reactor, completing the oxygen carrier loop. Thermodynamic studies demonstrate that the presence of CO2 does not significantly affect NO x purification performance at different flue gas flow rates. The operating temperatures of the reactors are selected based on NO x -temperature programmed oxidation (TPO) and CH4-temperature programmed reduction (TPR) experiments. Results show that the process can optimally operate at temperatures close to the combustion plants’ flue gas temperature of 400–500 °C, reducing the need for hot utilities. The study conducts comprehensive isothermal and autothermal analyses of the process to evaluate the effects of temperature and carrier flow rate on CH4 conversion, CO2 selectivity, carbon deposition, and NO x conversion. For the autothermal analysis, the CH4 reactor operates adiabatically, while the NO x reactor operates isothermally. Comparative studies with the conventional NO x selective catalytic reduction (SCR) process indicate an exergy efficiency and effective thermal efficiency (ETE) improvement of 9 and 18 percentage points, respectively. The findings suggest that this low-temperature chemical looping process is a promising solution for flue gas NO x treatment, utilizing cheaper natural gas as the reductant and eliminating environmental concerns, such as ammonia or urea slippage. Overall, this study contributes to the development of more efficient and sustainable methods for reducing NO x emissions.

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