Dryer with thermal recovery for combine harvester

A grain dryer to be associated with a combine harvester provided with an endothermic engine, comprising:

• a first feed screw comprising a first pipe having a first grain inlet at a first end and a first grain outlet at a second end which is distal from the first grain inlet, the first pipe comprising a first outer surface and a first inner surface and defining a first inner cavity having a circular geometry and a first diameter, the first pipe further comprises a first air inlet port providing ingress into the first inner cavity, a first air outlet port providing egress from the first inner cavity;
• a second feed screw comprising a second pipe having a second grain inlet at a third end and a second grain outlet at the fourth end which is distal from the second grain inlet, a second outer surface and a second inner surface and defining a second inner cavity having a circular geometry and a second diameter, the second pipe further comprises a second air inlet providing ingress into the second inner cavity and a second air outlet port providing egress from the second inner cavity;
• a first rotatable helicoid disposed along a first central axis in the first inner cavity of the first pipe, wherein the first rotatable helicoid comprising a first outer diameter close to the first diameter of the first pipe and wherein the first rotatable helicoid rotates in a direction to transfer grain disposed in the interior of the first pipe from the first grain inlet to the first grain outlet;
• a second rotatable helicoid disposed along a second central axis in the second inner cavity of the second pipe, wherein the second rotatable helicoid comprising a second outer diameter close to the first diameter of the first pipe and wherein the second rotatable helicoid rotates in a direction to transfer grain disposed in the interior of the second pipe from the second grain inlet to the second grain outlet;
• a first heat exchanger comprising a first heat exchanger air inlet port and a first heat exchanger air outlet port, the first heat exchanger further comprising an exhaust fume inlet port and an exhaust fume outlet port, wherein the exhaust fume inlet port is in communication with exhaust fumes leaving an endothermic engine of a combine harvester, wherein further the first heat exchanger air outlet port is in communication with the first air inlet port of the first feed screw;
• a second heat exchanger comprising a second heat exchanger air inlet port and a second heat exchanger air outlet port, the second heat exchanger further comprising an engine cooling liquid inlet port and an engine cooling liquid outlet port, wherein the engine cooling liquid inlet port and the engine cooling liquid outlet port are both in communication with a cooling liquid circuit used to cool the endothermic engine of the combine harvester, wherein further the second heat exchanger air outlet port is in communication with the second air inlet port of the second feed screw;
• fan means comprising a fan and an external air inlet port, the fan means further comprising a first output port and a second output port, wherein the first output port is in communication with the first heat exchanger air inlet port and wherein the second output port is in communication with the second heat exchanger air inlet port;
• one or more grain humidity sensors that measure the humidity values of the grains disposed in one or more points of the first inner cavity and of the second inner cavity;
• wherein the first feed screw has the first air inlet port at the first end and the first air outlet port at the second end and wherein further grain passes through the second feed screw after having passed through the first feed screw.