A grain dryer has an upper plenum in communication with a pair of heating columns. Each heating column has an inner boundary and an outer boundary being formed with a plurality of angled containment baffles configured to funnel grain down the heating column while allowing heated air to be drawn from the upper plenum through the grain. At least one fan takes a suction from the ductwork to draw heated air from the upper plenum through the heating column such that grain is exposed to heated air. The orientation of the containment baffles forming the inner boundary directs the flow of the heated air in a downward direction through an inner portion of a grain column between the inner boundary and the outer boundary, and the orientation of the containment baffles forming the outer boundary directs the heated air in an upwards direction in an outer portion of the grain column.

A grain dryer has pair of heating columns in communication with an upper plenum, and a pair of cooling columns in communication with a lower plenum. A heater is located between the lower plenum and the upper plenum, wherein air is heated by the heater as air in the lower plenum is pulled through the heater and into the upper plenum. As the grain flows into the cooling column, it is exposed to cooling air being pulled through the cooling column into the lower plenum. A cooling air bypass system having a plurality of bypass tubes brings bypass air into the lower plenum from outside the grain dryer without having the bypass air come into contact with the grain being cooled in the cooling section. The cooling air bypass system includes a grill with an adjustable damper to adjust the amount of bypass air that flows into the lower plenum.

A grain dryer has pair of heating columns in communication with an upper plenum, and a pair of cooling columns in communication with a lower plenum. A heater is located between the lower plenum and the upper plenum, wherein air is heated by the heater as air in the lower plenum is pulled through the heater and into the upper plenum. As the grain flows into the cooling column, it is exposed to cooling air being pulled through the cooling column into the lower plenum. Ductwork adjacent each heating column includes vertical sections arranged along a length of the grain dryer. Each vertical section has a fan located adjacent the uppermost horizontal level of the heating column. Each fan takes a suction from the ductwork to draw heated air from the upper plenum through the heating column.

A grain dryer having a mixed-flow heating section, a tempering transition section, and a vacuum-cooled crossflow cooling section. A fan positioned on the end of the dryer creates a negative pressure in the cooling plenum that pulls air through the grain, warming the air while cooling the grain. This warmed air is pulled through the fan and then passed through a heater to bring it to appropriate drying temperature. This air is then pushed into a heating plenum, where it passes through a mixed-flow grain column, drying the grain, and then exhausted to ambient air.

An improved mixed flow grain dryer is presented having a grain column with upper, middle and lower drying sections. The system includes a set of plenums and ducts configured to move air through the middle and lower drying sections at one or more lower temperatures, recover the air moved through the middle and lower drying sections, and move the recovered air through the upper drying section at a higher temperature. The system is configured to move grain through the upper drying section, then through the middle drying section, then through the lower drying section, while also: moving air of one or more lower temperatures through lower drying section and middle drying section, combining air moved through lower drying section and middle drying section, and moving the combined air through the upper drying section at a higher temperature.

A sawn wood drying system, which allows to take advantage of the heat contained in the dry wood that leaves the system to preheat the wet and cold wood that enters the system, the system comprising: a heating chamber, a drying chamber and a cooling chamber, sequentially arranged, and a transport path that allows the transfer of sawn wood through these three chambers; a first air circulation system, which provides a first high temperature air flow inside the drying chamber; and a second air circulation system that provides a second air flow, independent of the first air flow, which allows the heating chamber to be in fluid communication with the cooling chamber by means of external chambers or ducts connecting both chambers.

A grain dryer has a heated drying section with an upper plenum and a cooling section. A heater is positioned between the lower plenum and the upper plenum, wherein air is heated by the heater as air in the lower plenum is pulled through the heater and into the upper plenum. A fan takes a suction from a ductwork on the heated drying section to draw a vacuum in the upper and lower plenums. Grain enters the dryer and flows into the drying section where the grain is exposed to heated air being pulled from the upper plenum into the ductwork. Grain flows from the drying section into the cooling section where the grain is exposed to cooling air being pulled through outer walls of the cooling section into the lower plenum. Grain flows from the cooling section into the unloading section.

Described is a method and apparatus for drying organic material using the energy contained in the organic material to be dried to drive the drying process. The organic material could be sewage sludge, food scraps, manure, wood, bagasse etc. The latent heat of evaporation is recovered through the use of a heat pump mechanism. This allows for the retention of a majority of the heat within the system, allowing optimal drying conditions to be maintained throughout the drying process.

A grain dryer unload system is presented that facilitates operation of a discharge system independent of a metering system. A motor connects to an axle that connects to the discharge system, which may be a drag chain, a belt or an auger. The axle also connects to a metering system. A clutch mechanism is connected to an end of the axle and is positioned between the discharge system and the metering system. When the clutch mechanism is in an engaged position, the motor simultaneously operates the metering system and the discharge system. However, when the clutch mechanism is in a disengaged position, the motor operates the discharge system while the metering system does not operate. This arrangement facilitates easier cleaning of the grain dryer without introducing the fines into the grain or a connected grain storage device.

A grain dryer has a heated drying section with an upper plenum and a cooling section. A heater is positioned between the lower plenum and the upper plenum, wherein air is heated by the heater as air in the lower plenum is pulled through the heater and into the upper plenum. A fan takes a suction from a ductwork on the heated drying section to draw a vacuum in the upper and lower plenums. Grain enters the dryer and flows into the drying section where the grain is exposed to heated air being pulled from the upper plenum into the ductwork. Grain flows from the drying section into the cooling section where the grain is exposed to cooling air being pulled through outer walls of the cooling section into the lower plenum. Grain flows from the cooling section into the unloading section.