The high-concentration and pumpable pig manure slurry: Preparation, optimization, and evaluation for continuous supercritical water gasification

The preparation of pumpable slurry with high solid content has emerged as one of the obstacles in the continuous supercritical water gasification of pig manure. This study aims to address this challenge by employing K₂CO₃ and thermal treatments. Initially, evaluating the effect of parameters on the pumpability, stability, and viscosity of the slurry and optimizing the pulping conditions were carried out. The findings indicate that a 40 wt% slurry can be obtained at a K₂CO₃ ratio of 0.10, a pulping temperature of 160 °C, a reaction time of 30 min, and a premixing temperature of 80 °C. For a 50 wt% slurry, the corresponding conditions increased to 0.20, 180 °C, and 90 min, separately. Then, an insight into pulping mechanism reveals that the viscosity and stability of slurry are determined by the particle size and surface functional groups. The functional groups such as -C=O and -OH on the particle surface are matched with the organic components in the slurry, which is beneficial for reducing the viscosity of the slurry and improving its stability. Finally, a 40 wt% concentration slurry is successfully pumped. At a temperature of 620 °C and a preheating water ratio of 4, gasification efficiency reaches 74.43 %.