Two-stage static dryer for converting organic waste to solid fuel
First Claim
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1. A method for drying organic waste material comprising the steps of:
- (a) hot-air convection drying, with wet solid organic material entering through the top inlet of the hot-air temperature unit and hot air entering through the bottom inlet of the hot-air temperature drying unit, said hot-air temperature drying unit further comprising the following operating conditions;
i) hot-air convective drying with heated air having a temperature between 150°
F. (66°
C.) and 350°
F. (177°
C.);
ii) short residence time of solid organic material between 30-300 seconds;
iii) ratio of volumetric airflow-to-solid organic material between 25-75 scf (standard ft3)/lbmass (1.6-4.7 standard m3/kg);
iv) air velocity of 300-600 ft/min (1.5-3.0 m/s) moving upward counter-currently to the downward flow of moist wet solid organic material;
(b) warm-air convection drying, with moist, partially dried solid organic material produced in the hot-air temperature drying unit entering at the top inlet to the warm-air temperature drying unit and warm air entering through the bottom inlet of the warm-air temperature drying unit, said warm-air temperature drying unit further comprising the following operating conditions;
i) warm-air convective drying with warm from a mixture of cooler ambient air and hotter air from the hot-air temperature unit exhaust gas, said mixture having a temperature between 90°
F. (32°
C.) and 150°
F. (66°
C.);
ii) long residence time of solid organic material between 2-12 hr (7,200-43,200 s);
iv) ratio of volumetric airflow-to-solid organic material between 40-100 scf (standard ft3)/lbmass (2.5-6.3 standard m3/kg);
iv) air velocity of 60-300 ft/min (0.3-1.5 m/s) moving upward counter-currently to the downward flow of partially dried solid organic material(c) gas recirculation of hot-air temperature unit exhaust gas that is mixed with ambient air to make warm inlet air for the warm-air temperature unit gas supply, said mixing of hot-air temperature unit exhaust gas with ambient air acting as means of increasing the thermal efficiency of the dryer.
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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.
223 Citations
4 Claims
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1. A method for drying organic waste material comprising the steps of:
-
(a) hot-air convection drying, with wet solid organic material entering through the top inlet of the hot-air temperature unit and hot air entering through the bottom inlet of the hot-air temperature drying unit, said hot-air temperature drying unit further comprising the following operating conditions; i) hot-air convective drying with heated air having a temperature between 150°
F. (66°
C.) and 350°
F. (177°
C.);ii) short residence time of solid organic material between 30-300 seconds; iii) ratio of volumetric airflow-to-solid organic material between 25-75 scf (standard ft3)/lbmass (1.6-4.7 standard m3/kg); iv) air velocity of 300-600 ft/min (1.5-3.0 m/s) moving upward counter-currently to the downward flow of moist wet solid organic material; (b) warm-air convection drying, with moist, partially dried solid organic material produced in the hot-air temperature drying unit entering at the top inlet to the warm-air temperature drying unit and warm air entering through the bottom inlet of the warm-air temperature drying unit, said warm-air temperature drying unit further comprising the following operating conditions; i) warm-air convective drying with warm from a mixture of cooler ambient air and hotter air from the hot-air temperature unit exhaust gas, said mixture having a temperature between 90°
F. (32°
C.) and 150°
F. (66°
C.);ii) long residence time of solid organic material between 2-12 hr (7,200-43,200 s); iv) ratio of volumetric airflow-to-solid organic material between 40-100 scf (standard ft3)/lbmass (2.5-6.3 standard m3/kg); iv) air velocity of 60-300 ft/min (0.3-1.5 m/s) moving upward counter-currently to the downward flow of partially dried solid organic material (c) gas recirculation of hot-air temperature unit exhaust gas that is mixed with ambient air to make warm inlet air for the warm-air temperature unit gas supply, said mixing of hot-air temperature unit exhaust gas with ambient air acting as means of increasing the thermal efficiency of the dryer. - View Dependent Claims (2, 3, 4)
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Specification