Forced convection drying of bulk solids uses a mixed hot and cold gas feed, and is suitable for drying of powdered coal, ores , and granular plastics

摘要

Damp bulk material is dried by contacting with a temperature controlled mixture of a heated gas and a secondary gas. The exhaust gas temperature and/ or volumetric flow rate is controlled for deviation from a predetermined tolerance band around the dew-point value. The secondary gas may be air, nitrogen or exhaust combustion gas. Independent claims are also included for: (a) a dryer for damp material which uses a drying gas produced by mixing a hot gas from a heater with a secondary gas in a gas mixer; (b) a device controls the inlet drying gas temperature as measured from a sensor, by modulating the secondary gas flow rate. The dew-point temperature of the dryer exhaust gas is measured via sensors, and after addition of a safety margin, the outlet temperature for the heater is adjusted by modulating feeds of fuel gas and air. The heater may be a steam or hot water heat exchanger.