MIXED FLOW GRAIN DRYER WITH VACUUM COOL HEAT RECOVERY SYSTEM

Abstract

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.

Claims

1. A grain dryer, comprising: a wet holding section in communication with a mixed-flow heating section; a tempering transition section in communication with the mixed-flow heating section; a crossflow vacuum-cooling section in communication with the tempering transition section; an unloading section in communication with the cooling section; and a negatively pressurized plenum within the cooling section, between the tempering transition section and the unloading section.

2. The dryer of claim 1 further compromising a positively pressurized plenum within the heating section.

3. The dryer of claim 1 wherein the cooling columns have perforated inner and outer walls.

4. The dryer of claim 1 further comprising a discharge port in communication with only one discharge conveyor.

5. The dryer of claim 1 having a grain distribution baffle within the tempering transition section.

6. A method of drying grain with a mixed-flow dryer, comprising the steps of: creating a negative pressure within a cooling plenum to draw outside air through a cooling column and into the cooling plenum; heating the air further by passing it through a heater, in communication with a heating plenum; heating and drying grain within a heating section through paths in a heating column in communication with the heating plenum; and discharging heated air through duct openings on an outer wall of the heating column.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a side sectional view of a mixed flow grain dryer.

[0011] FIG. 2 is a perspective sectional view of a mixed flow grain dryer.

[0012] FIG. 3 is a perspective view of a mixed flow grain dryer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Referring to the figures, a mixed flow dryer 10 has a wet hold section 12 that acts as a holding bin for grain flowing through an inlet port 13 of the dryer 10. The wet hold section 12 is in communication with and distributes grain to a heating section 14 having a pair of separated heating columns 16. 18. The heating columns 16 and 18 each have an outer wall 20 and an inner wall 22 that preferably are thirty inches apart. Both the outer 20 and inner 22 walls have a plurality of alternating rows of ducts 26 that provide equal length air paths from the inner wall 22 to the outer wall 20. Preferably, the ducts 26 are triangular in shape.

[0014] At the bottom of and in communication with the heating columns 16 and 18, is a tempering transition section 30. The tempering transition section 30 has a solid inner 32 and outer 34 wall that prevents air from passing through the transition section 30. Within the transition section 30 is a grain distribution baffle 35 positioned below heating columns 16 and 18 to equalize the grain flow distribution in both the heating section 14 and cooling section 36.

[0015] The transition section 30 is in communication with a cooling section 36 having a pair of cooling columns 38 and 40. Preferably, the cooling columns 38 and 40 have perforated inner 42 and outer 43 walls that are narrower than the heating columns 16 and 18 and in one example are fourteen inches wide.

[0016] Between the cooling column 38 and 40, the transition section 30, and below the heating columns 16 and 18 is a plenum 44. On the end of the dryer 10, fan 46 creates a negative pressure within the plenum 44 compared to the outside air. In communication with the plenum is a heater 48. Perforated screens/walls are used in the vacuum cooling chamber/section 36 to minimize the introduction of particulate matter into the recovered air stream. Use of perforated screens prevent issues arising from passing materials through the fan 46 and heater unit 48, and keep the drying plenum clean and free from debris. This allows for passing recirculated air through the heating unit 48.

[0017] In operation, grain enters the dryer 10 through inlet port 13 and into the wet hold section 12. From the wet hold section 12, grain flows into heating columns 16 and 18 of heating section 14 to the tempering transition section 30.

[0018] Within the tempering transition section 30, the grain engages baffle 35 and is directed to columns 38 and 40 of the cooling section 36. From the cooling section 36, grain flows to an unloading section 50. In communication with the unloading section 50 is a single discharge conveyor 52 such as an auger, drag conveyor, belt conveyor or the like. This is novel compared to present two-column, mixed-flow dryers that have at a minimum of two separate conveyors.

[0019] Outside or ambient air flows through perforated outer wall 43 to the perforated inner wall 42 of cooling columns 38 and 40 and into the plenum 44 due to the negative pressure created by fan 46. As the ambient air flows through the grain within cooling columns 38 and 40, the air is heated while it cools the grain. The heated air received within the plenum 44 from cooling columns 38 and 40 is pulled into fan 46 and then further heated by heater 48, before entering plenum 54. Because the air entering the plenum 44 from cooling section 36 is already heated, less energy is needed to heat the air to appropriate drying temperature within the plenum 54.

[0020] The heated air then flows to the heating section 14. From the heating section 14, air flows through inner duct openings 53 towards the air paths in columns 16 and 18 to heat and dry the grain in the heating section 14 before heated air is exhausted through outer duct openings 26 on outer walls 20 of columns 16 and 18.

[0021] Thus, a grain dryer having a vacuum-cool heat recovery system has been disclosed that is more energy efficient and at the very least meets all of the stated objectives.