Dried biosolids, or digested wastewater sludge, has the potential to be converted from an expense to a resource of renewable energy. The equilibrium moisture content (EMC) for biosolids was determined experimentally in the range of 10--84% relative humidity and between 30AdC and 60AdC. The measured EMC values were fitted to several well known models, and to a new model that accounts for mixing and swelling contributions to water activity. The parameters of the new model have a direct physical interpretation, and the model allows for prediction of moisture partitioning between a 'free' phase and 'bound' phase. The rate of drying was measured as a function of temperature and gas velocity in a 3-inch fluidized bed. The drying rate increased with temperature and was independent of gas velocity. In all cases, the drying rate was continuously decreasing; no period of constant rate was observed. This indicates that the dominant resistance to drying was internal diffusion. An integrated process was designed for conversion of sludge to electric power. From economic analysis for a publicly owned mid-sized plant, a total capital investment of $5 million is required to produce 0.7 MW. The discounted cash flow rate of return on the investment is 10.2%, for a 10-year long project.The rate of drying was measured as a function of temperature and gas velocity in a 3-inch fluidized bed. The drying rate increased with temperature and was independent of gas velocity.
|Title||:||Techno-economic Analysis of Biosolids Equilibrium Moisture and Drying for Energy Utilization|
|Publisher||:||ProQuest - 2008|