Sorption enhanced coal gasification for hydrogen production using a synthesized CaOMgO-molecular sieve sorbent

This study tends to investigate sorption enhanced hydrogen production process using MgO-molecular sieve modified CaO-based sorbents in a horizontal fixed bed reactor. The synthesized sorbents were prepared using a wet mixing method for enhancing H2 yields and concentration as well as capturing CO2. The sorbents were characterized by means of X-ray diffraction (XRD), nitrogen adsorption and desorption isotherms test, and scanning electron microscopy (SEM)/energy dispersive spectrometer (EDS). The ash content of coal and the calcined mixture were analyzed by the method of energy dispersive X-ray fluorescence (EDXRF). The CaOMgO-molecular sieve sorbents were investigated during 20 adsorption and calcination cycles using thermogravimetric analyzer (TGA). The effects of different kinds of CaO-based sorbents, the molar ratio of Ca/C, and diverse coal species on gas yields and concentration were investigated. The experimental results verified that the presence of modified sorbents in the steam coal gasification process enhanced the concentration of hydrogen to more than 80%, with lower concentration of CO2 emission. The highest hydrogen concentration were obtained using the modified CaOMgO-5A molecular sieve at the condition that the temperature is 650 °C, the N2 flow rate is 0.5 L/min, and the water injection rate is 0.3 L/min.