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.

Automated summary

The characteristics of chemical looping hydrogen generation using sewage sludge and corncob as fuel were investigated. The reduction depth and catalytic reaction mechanism of CuO-Fe2O3 oxygen carrier were analyzed. The adsorption properties of C molecules on CuFe2O4 surface were simulated using DFT.