Two-stage static dryer for converting organic waste to solid fuel
First Claim
1. A method for drying organic waste material consisting of both high-temperature and low-temperature drying, said high temperature drying method consisting of:
- (a) hot-air convective drying with heated air having a temperature between 150°
F. (66°
C.) and 350°
F. (177°
C.);
(b) short residence time of solid organic material between 30-300 seconds;
(c) ratio of volumetric airflow-to-solid organic material between 25-75 scfm (standard ft3 )/lbmass (1.6-4.7 standard m3/kg).(d) air velocity of 300-600 ft/min (1.5-3.0 m/s) moving upward counter-currently to the downward flow of moist pellets
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Abstract
An energy-efficient method and apparatus for drying pelletized, moist organic material is described. The method consists of a rapid, high temperature static drying process in a shallow bed, followed by traditional vertical static drying in a deep bed. Hot exhaust gas from the shallow-bed, hot-temperature static dryer is then recirculated to provide thermal energy to the deep-bed, warn-temperature static dryer. This invention can be used to convert wet, organic waste materials such as animal and poultry waste, municipal wastewater sludge, urban post-consumer food waste, or manufactured food byproducts and residuals into solid fuel.
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Citations
7 Claims
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1. A method for drying organic waste material consisting of both high-temperature and low-temperature drying, said high temperature drying method consisting of:
-
(a) hot-air convective drying with heated air having a temperature between 150°
F. (66°
C.) and 350°
F. (177°
C.);(b) short residence time of solid organic material between 30-300 seconds; (c) ratio of volumetric airflow-to-solid organic material between 25-75 scfm (standard ft3 )/lbmass (1.6-4.7 standard m3/kg). (d) air velocity of 300-600 ft/min (1.5-3.0 m/s) moving upward counter-currently to the downward flow of moist pellets - View Dependent Claims (2, 3)
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4. A two-stage, vertical static dryer apparatus consisting of:
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(a) an upper hot-temperature stage with wet solid organic material entering at the top inlet, hot air entering the bottom below an inverted diffusion cone to distribute hot air across the horizontal cross section of the upper hot-temperature unit, and an exhaust gas outlet at the top of the hot-temperature upper stage; (b) a lower warm-temperature stage with moist, partially-dried solid material that has developed a dry, crusted exterior in the upper hot-temperature stage entering at the top inlet of the lower warm-temperature stage, warm air entering the bottom below an inverted diffusion cone to distribute warm air across the horizontal cross section of the lower warm-temperature unit, and an exhaust gas outlet at the top of the warm-temperature lower stage; (c) a hot exhaust gas recirculation duct that routes hot exhaust gas from the upper hot-temperature dryer to a mixing venturi inlet to mix hot exhaust gas with ambient air upstream of the inlet to the lower warm-temperature stage. - View Dependent Claims (5, 6, 7)
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Specification