Method of heating a grain dryer and apparatus therefor

A stove for burning corn (maize) including a heat exchanger having an input chamber in which corn is burned, and an output chamber where heat from the burning corn is absorbed in air, which is directed to a conventional grain drying machine for drying the grain therein. Unique arrangements are made for optimizing the quantity of air admitted to the input chamber for combustion, and for making the flow of combustion air uniform across the entire mass of burning corn. An auger is included for feeding corn to the input chamber either from a separate supply vessel, or, in cases where corn is the grain to be dried, from the grain dryer itself.

This invention relates to a novel method of heating a grain dryer, and to 
improved, novel apparatus therefor. 
Heretofore, heat sources for grain dryers have commonly been propane or 
petroleum burners, or other conventional sources. Also, U.S. Pat. No. 
4,509,273, to Roisen teaches burning field waste, particularly corn cobs, 
stalks, and the like. 
Propane and other conventional fuels are currently relatively expensive, 
and burning field waste as taught by Roisen entails a great deal of 
inconvenience and expense such that few farmers are willing to undertake 
it. 
BRIEF DESCRIPTION 
Briefly, according to the invention, heat for drying grain is generated by 
burning maize, usually called corn in America, and a specially designed 
burner has been developed to ensure even burning of the corn even though 
it may contain fines, broken pieces, and other contaminating matter that 
would interfere with its satisfactory burning in a corn fired stove of 
previously known kind. 
Corn is found to be a significantly less expensive fuel than propane, or 
any of the other conventional fuels, especially in view of the currently 
depressed price of the grain. Moreover, with the apparatus of the 
invention, operation is very simple and convenient. When corn is the grain 
being dried, fuel for heating may be taken directly from the grain dryer, 
and when some other grain is to be dried it is a simple matter to provide 
a separate container for the corn. Further, ventilation for providing 
combustion air is, in most case, taken care of by the fan that is included 
as an essential part of most grain drying machines, so that the apparatus 
need only include adequate flow controls and the like. The only direct 
power requirement is the need to drive a conveyor machine or some sort to 
move the fuel corn from its container to the fire pot, and this is only a 
small requirement. 
The apparatus of the invention is designed to optimize the volume and 
uniformity of flow of combustion air to the burning corn and also to 
distribute the fuel corn uniformly over the fire grate. Burning corn 
requires a relatively large amount of air, and it has been found to be 
important that no part of the corn in the fire grate be blocked off from 
the combustion air, else pockets of unburned corn may develop making for 
unevenness of heat flow. In particular, a firepot having perforated bottom 
and side walls is mounted as the combustion chamber within a secondary 
chamber, or duct, that feeds heated air directly to the grain dryer. The 
effluent from the corn fire is smokeless and is fed directly into the 
stream of heated air that flows into the grain dryer. The fuel corn is 
delivered by an auger from its source, which may be the grain dryer 
itself, through an inlet at the top of the combustion chamber to a 
dispersing deflector which acts to disperse the corn evenly over the fire 
grate. The air flow driven by the fan of the grain dryer is downwardly in 
the region where the fuel corn falls from the auger into the firebox so 
there is no tendency for the corn to ignite before it reaches the grate.

Referring now to the drawings, the burner of the invention is shown as used 
for feeding hot, grain-drying air to a grain dryer 10 of any desired kind. 
The actual dryer used in the development of the invention was made my the 
Matthews Company, of Crystal Lake, Ill., Model MC-250E. 
The secondary chamber 12 of the burner was constituted by a conventional 
fuel oil tank of 275 gallon capacity turned on its side with its right 
hand end, as viewed in FIG. 1, cut out, and provision made for mounting 
certain other parts as described hereinafter. The open right hand end of 
the chamber 12 is positioned to confront the open inlet fairing 14 of the 
dryer 10 so that the fan (not shown) of the dryer 10 provides a relatively 
strong suction to draw air through the burner. 
A deflector 15 is fixed inside the chamber 12 at its front end to divert 
heated air away from the blower fan motor (not shown) of the dryer 10. The 
position of the deflector 15 depends on the construction of the dryer and 
the position of the motor that drives its blower fan. In some cases where 
the blower motor is adequately protected otherwise the deflector may not 
be needed. 
The combustion chamber 16 of the burner extends vertically through the 
secondary chamber 12 and is made of a standard 55 gallon drum with its 
bottom removed and substituted by the bottom 18 of a 30 gallon drum. 
As seen in FIG. 3, a central hole 19 about six inches in diameter is cut in 
the lid 21 of the drum that constitutes the combustion chamber 16 for 
admitting fuel corn to the chamber. 
As best seen in FIG. 4, an effluent opening 20 is cut in the front wall of 
the chamber 16 near its upper end and opening into the secondary chamber 
so that suction from the dryer 10 is applied throughout the entire 
interior of the combustion chamber. In practice, by trial and error it was 
found that an opening about 18" wide by 5" high, placed in the front wall 
near the top of the chamber 16 provided near optimum result. 
The bottom 18 of the combustion chamber is the fire grate. It includes not 
only the bottom of the 30 gallon drum but also a part 19 of its sidewall. 
It is perforated over its entire area, including the sidewall portion 19, 
as best seen in FIGS. 2 and 6, to allow adequate amounts of air to be 
admitted to the fire pot, and to maintain a uniformity of flow across its 
entire horizontal section. In addition, a perforated cone 22 is mounted at 
the center of the grate 18 for admitting combustion air right at the 
center of the burning mass of corn, and a circular deflector 24 is mounted 
atop the cone 22 for dispersing the corn as it falls into the fire pot. It 
was found that the optimum hole size for the perforations is about 5/32 
inch diameter. The amount of combustion air flowing into the fire pot may 
be further controlled by a damper 26 which is adjustably suspended beneath 
the chamber 16. Raising the damper 26 reduces the amount of air admitted. 
A feed auger 30, driven by a motor 32 is mounted above the heat exchanger 
12 for delivering corn at a controllable rate to the input chamber 16. 
When the grain being dried is corn the auger is mounted to take the corn 
directly from the dryer 10. The dryer shown is of the kind wherein the 
corn moves downwardly through a drying chamber, losing moisture as it 
descends. The input end of the auger 30 is inserted into the drying 
chamber at the point where the moisture content of the corn is about 20%. 
In cases where grain other than corn is to be dried a separate container 
must be supplied for holding the fuel corn. 
A pair of air flow control doors 50 (FIGS. 2 and 5) are provided at the 
rear of the secondary, or output chamber of the burner for adjusting the 
amount or air drawn into it by-passing the input chamber 16, and a level 
adjusting rod 40, along with any other desired support means, is arranged 
as desired for maintaining the attitude of the burner. 
It was also found that field corn with about 20% moisture, the content of 
the corn taken from the dryer, yields about 385,000 BTU's per bushel when 
burned in the burner shown. Corn with 20% moisture is currently available 
at about $74 per ton, which is considerably cheaper than fully dried corn. 
Even fully dried corn is substantially less expensive than propane, the 
usual fuel, and using corn with relatively high moisture provides 
additional savings. Moreover, relative to propane, the combustion product 
from burning corn contains significantly less water and is thus better 
able to contribute to the drying process than is propane, assuming that in 
both cases the combustion product is fed into the dryer along with a 
portion of the ambient air. 
The equipment of the invention is also relatively simple and inexpensive, 
versatile and very easy and convenient to use. In addition, it is neat and 
clean, and produces very little residue.