Study on hydrogen production of sewage sludge/corncob using chemical looping with Cu-Fe as oxygen carrier

Sewage sludge contains a very high ash content, which makes it unsuitable for chemical looping hydrogen generation (CLHG). The features of CLHG were investigated in a fixed bed reactor using sewage sludge (S) and corncob (B) as fuel. The wet impregnation method was adopted to prepare the CuO-Fe2O3 oxygen carrier (OC). It was found that when S and B were mixed at a ratio of 2:1, the H-2 production could be increased from 0.8 to 12 mL. When the C/O ratio of S/B and S/C-b (corncob char) to OC was equal, OC had a higher reduction depth when the carbon in the fuel was primarily fixed carbon. The reaction of O-2 released from CuFe2O4 with corncob char promoted the ring-opening dehydrogenation of aromatic carbon, and the reaction rate between fuel and OC was increased. X-ray diffraction and Brunauer-Emmett-Teller analysis showed that the accumulation of mineral components in sewage sludge ash on the surface of OC was found to perform a catalytic function in the oxidation reaction. Due to the consumption of Cu in the cyclic reaction, the OC activity was weakened. The adsorption properties of C molecules on CuFe2O4(100) perfect surface and oxygen-deficient surface were studied using DFT (density functional theory). It revealed that on the CuFe2O4(100) perfect surface, some lattice O reacted with C molecules to directly generate CO or C(O) structure, which required very low energy. The effect of C molecules on metal adsorption sites was mainly reflected in their promotion of the activation of O ions nearby. For the oxygen-deficient surface, the adsorption of C molecules on metal sites was enhanced, and the inner O ions migrated to the surface to fill the oxygen holes.