Research on the Thermal Reaction Mechanism of Iron/Calcium‐Based Oxygen Carriers With Graphite and Coal Char

ABSTRACT In order to clarify the thermal reaction mechanism between iron/calcium (Fe 2 O 3 /CaO)‐based oxygen carriers and coal char, the gas escape from the reaction process was resolved by TG‐MS coupling, and the equivalent characteristic spectrum analysis (ECSA) method was used to determine the specific reactions occurring. Under Ar atmosphere, Fe 2 O 3 starts to be reduced by graphite at 560°C, producing CO 2 , and at 1040°C, CO is produced from the reaction between graphite and CO 2 . When CaO is added to Fe 2 O 3 , CaO absorbs the CO 2 produced, affecting the path of the reaction. The reaction to produce CO 2 also occurs first in the two iron/calcium‐based oxygen carrier conditions of sintered and pelletized ore, and CO production also occurs at high temperatures. In the case of air atmosphere combustion, only O 2 is consumed, and CO 2 is produced, no CO is formed. Graphite combustion consumes oxygen at a maximum value of 0.0393 mmol/min, and the addition of sintered ore reduces the maximum value of oxygen consumption to 0.0294 mmol/min, a decrease of about 25%, reflecting the oxygen buffering effect of oxygen carriers. Because the reaction of the coal char condition was concentrated at 300°C–700°C, this temperature interval, the addition of pelletized ore to coal char reduced the area of O 2 consumption from 3.36 to 3.01, indicating that the oxygen carrier provided additional oxygen in the reaction and reduced the oxygen consumption. The addition of iron/calcium oxygen carriers also reduces the reaction activation energy and makes the thermal reaction easier.