Takeo Sakano

The behaviour of phosphorus and heavy metals in sewage sludge ashes

The effect of the combustion atmosphere and the additives (CaO and HCl) on the behaviour of phosphorus and heavy metals during sewage sludge combustion was investigated. The results demonstrated that the reduction combustion promoted the vapourisation of phosphorus and heavy metals during sewage sludge combustion. Moreover, the concentrations of phosphorus and heavy metals in the bottom ash decreased with increasing HCl ratio, and the addition of CaO can stabilise heavy metals and phosphorus. It was also observed that phosphorus and heavy metals increased with increasing CaO ratio. Lastly, the difference of the TG-DTA curves with and without additives is discussed.

Simulating the transformation of heavy metals during coal or sewage sludge combustion

A mathematical model (FPM) is presented to predict the transformation of heavy metals in the downstream of combustor or incinerator. The model accounts for the transformation of heavy metals through the combined effect of condensation,_nucleation, coagulation, external force and thermophoresis force. The calculation of heavy metals is embodied in the post-processor appended to Fluent soft. Before the simulation, velocity, temperature, PbCl2 concentration and other initial parameters are obtained by experiment. In addition, the transformation of PbCl2 is also experimentally studied. The comparison of experimental and predicted results indicate that the fine particle model (FPM) is valid for predicting the transformation of heavy metals in the downstream of incinerator or combustor.

Investigation of a direct melting dehydrated sewage sludge pilot plant

A direct melting dehydrated sewage sludge furnace was tested to obtain the basic operating parameters. Observation of particles (fly ash and deposited particulates) inside the pilot plant was performed to determine the particle properties. The results showed that dehydrated sewage sludge could be directly melted at a temperature of 1400?C with stable combustion. With regard to the fly ash, the majority of the particle size distribution was observed to be in the range 0.1?1 ?m, and amongst heavy metals, the highest concentration in the ash was for zinc. For the deposited particle fraction, most were observed to be in the size range 2?20 ?m and the main inherent chemical compound was associated with metal phosphate. Moreover, at different temperatures inside each chamber, the compositions and chemical compounds were found to change. To estimate the amount of deposited particles, the deposition flux was calculated by various deposition mechanisms, and it was found that diffusion was the dominant deposition mechanism, followed by thermophoresis and gravity, respectively.