Gasification is a promising technology to utilize solid wastes. Co-gasification of high-ash sewage sludge and straw were studied in a fluidized bed using oxygen-enriched air. Several factors influencing co-gasification performance were investigated, including the blending ratio of straw (BR, 0–100 %), the oxygen percentage of enriched air (OP, 30.2–50 %) and the bed material type (high alumina bauxite, calcined dolomite and olivine). The results indicated that the proper increase in BR led to higher syngas yield and an increase in OP caused an increase in combustible gas components, both showing improvements for waste gasification. Correspondingly, the maximum cold gas efficiency was obtained at BR of 50 % and OP of 44.7 %, respectively. Additionally, calcined dolomite exhibited the maximum advantage in the reduction of heavy polycyclic aromatic hydrocarbons (PAHs), promoting the production of H ₂ and CO. The addition of high alumina bauxite was favored for improving syngas yield and gasification efficiency.

In order to reduce the dependence of accuracy on the number of grids in the Ausas cavitation algorithm, a modified Ausas algorithm was presented. By modifying the mass-conservative Reynolds equation with the concept of linear complementarity problems (LCPs), the coupling of film thickness h and density ratio θ disappeared. The modified equation achieved a new discrete scheme that ensured a complete second-order-accurate central difference scheme for the full film region, avoiding a hybrid-order-accurate discrete scheme. A journal-bearing case was studied to show the degree of accuracy improvement and the calculation time compared to a standard LCP solver. The results showed that the modified Ausas algorithm made the asymptotic and convergent behavior with the increase of nodes disappear and allowed for the use of coarse meshes to obtain sufficient accuracy. The calculation time of the modified Ausas algorithm is shorter than that of the LCP solver (Lemke’s pivoting algorithm) for middle- and large-scale problems.

In this study, the combustion behavior, synergistic effect and ash characteristics during the co-combustion of bituminous coal and wheat straw were fully analyzed by thermogravimetric analyzer, ash melting point analyzer, X-ray diffraction, and SEM. Thermogravimetry analysis showed that wheat straw was easier to be ignited, showing higher devolatilization activity and lower thermopositive temperature. Co-combustion displayed volatiles and char combustion stage and showed lower combustion rate compared to mono-combustion. For the wheat straw blending ratio ? 50%, significant positive synergistic effect was observed during the volatiles combustion stage while negative synergistic effect was found during the char combustion stage. With wheat straw blending, the co-combustion ash fusion temperature first increased and then decreased. The mineral components of co-combustion ash gradually changed from high ash melting point compounds to complex calcium silicate hydrate. The morphology of co-combustion ash turned from hard flake structure to loose porous structure, showing partial melting in the biomass derived pores. Small addition of wheat straw during co-combustion would be beneficial to enhance the ash fusion temperature and optimize combustion performance.