# US 11,994,342 B2 · Hybrid kiln for drying wood, biochar and agriculture products

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- Number: US 11,994,342 B2
- Document ID: US11994342B2
- Status: Granted
- Kind: B2
- Application number: 17/277,826
- Filed: 2019-12-19
- Published: 2022-04-14
- Granted: 2024-05-28
- Earliest claimed: 2018-12-19
- Assignees: The George Washington University; Mississippi State University
- Applicants: The George Washington University
- Inventors: Richard Clive Millar; Thomas A. Mazzuchi; Todd Mlsna
- Web page: https://patentgrep.com/patent/US11994342B2

## CPC

- F26B 3/283: {in combination with convection}
- F26B 3/04: the gas or vapour circulating over or surrounding the materials or objects to be dried (F26B3/14 takes precedence)
- F26B 3/28: by radiation, e.g. from the sun
- F26B 9/06: in stationary drums or chambers
- F26B 21/25: partly outside the drying enclosure
- F26B 21/30: Controlling, e.g. regulating, parameters of gas supply
- F26B 21/33: Humidity
- F26B 21/50: Ducting arrangements from the source of air or other gases to the materials or objects being dried
- F26B 23/10: using tubes or passages containing heated fluids {, e.g. acting as radiative elements; Closed-loop systems (for combustion gases F26B3/305)}
- F26B 2210/16: Wood, e.g. lumber, timber
- F26B: DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM (drying devices for combines A01D41/133; racks for drying fruit or vegetables A01F25/12; drying foodstuffs A23; drying hair A45D20/00; body-drying implements A47K10/00; drying household articles A47L; drying gases or vapours B01D; chemical or physical processes for dewatering or like separating liquids from solids B01D43/00; centrifugal apparatus B04; drying ceramics C04B33/30; drying yarns or fabrics in association with some other form of treatment D06C; drying frames for laundry without heating or positive air circulation, domestic laundry-or spin-driers, wringing or hot pressing laundry D06F; furnaces, kilns, ovens F27)

## Abstract

A hybrid kiln system and method for drying material, such as lumber, logs, and timber. A solar air heater uses solar radiation to heat air. The heated air is pushed into a kiln using one or more solar air heater fans. A dehumidifier is also provided to dehumidify and heat the air within the kiln. A method for determining when the solar air heater fans and the dehumidifier should be activated is also provided, and is based upon the temperature difference between the solar air heater's interior and exterior, as well as the relative humidity within the kiln.

## Claims

### Claim 1

A kiln comprising:
a kiln body forming an enclosure with a kiln interior;
a solar heater outside of said kiln body to generate heated air;
a plenum coupled to said solar heater and said kiln body to provide the heated air to the kiln interior;
one or more circulation fans inside said kiln interior to circulate air inside said kiln interior;
a dehumidifier to remove air from said kiln interior, dehumidify the removed air, and introduce dehumidified air into said kiln interior; and
a moisture detection apparatus having a moisture detector to determine a drying rate inside the kiln interior, said moisture detection apparatus comprising:
a first water reservoir;
a second water reservoir;
a first inlet tube coupled to an output of said dehumidifier;
a second inlet tube coupled to said first water reservoir;
a third inlet tube coupled to said first and/or second water reservoir;
a first inlet valve coupled to said first inlet tube, said second inlet tube and said third inlet tube to direct water from the output of said dehumidifier to said first and/or said second water reservoir;
a first outlet tube coupled to said first water reservoir and an exterior of said kiln body;
a first outlet valve to direct water from said first water reservoir to the exterior of said kiln body;
a second outlet tube coupled to said second water reservoir and the exterior of said kiln body;
a second outlet valve to direct water from said second water reservoir to the exterior of said kiln body; and
a controller operating the first inlet valve, first outlet valve, and second outlet valve.

### Claim 2 (depends on 1)

The kiln of claim 1, wherein the enclosure is airtight.

### Claim 3 (depends on 1)

The kiln of claim 1, further comprising one or more baffles inside said kiln interior to direct air flow within the kiln interior.

### Claim 4 (depends on 1)

The kiln of claim 1, wherein said dehumidifier is inside said kiln interior.

### Claim 5 (depends on 1)

The kiln of claim 1, wherein said dehumidifier is outside said kiln body and coupled to said kiln body.

### Claim 6 (depends on 1)

The kiln of claim 1, further comprising a heater fan to draw into said kiln interior from said plenum.

### Claim 7 (depends on 1)

The kiln of claim 1, further comprising a backup heater, said controller operating said backup heater when said solar heater is unable to provide sufficient heated air.

### Claim 8 (depends on 7)

The kiln of claim 7, wherein said backup heater has a power source.

### Claim 9 (depends on 8)

The kiln of claim 8, wherein said power source is electric, gas, coal, wood, or pellets.

### Claim 10 (depends on 1)

The kiln of claim 1, wherein:
the first inlet tube is further coupled to said first water reservoir and an output of said dehumidifier;
the first inlet valve is further coupled to said first inlet tube to direct water from the output of said dehumidifier to the first water reservoir;
the second inlet tube is further coupled to said second water reservoir and the output of said dehumidifier; and
a second inlet valve coupled to said second inlet tube to direct water from the output of said dehumidifier to the second water reservoir.

### Claim 11 (depends on 10)

The kiln of claim 10, wherein:
the first outlet tube is coupled to said first water reservoir and a kiln output;
the first outlet valve is coupled to said first outlet tube to direct water from said first water reservoir to said kiln output;
the second outlet tube is coupled to said second water reservoir and the kiln output; and
the second outlet valve is coupled to said second outlet tube to direct water from said second water reservoir to said kiln output.

### Claim 12 (depends on 11)

The kiln of claim 11, said moisture detection apparatus further comprising:
a first water sensor positioned in said first water reservoir to detect a first water level and generate a first water level output;
a second water sensor positioned in said second water reservoir to detect a second water level and generate a second water level output; and
a controller receiving the first water level output and the second water level output and determine the drying rate inside the kiln interior based on the received first and second water level outputs.

### Claim 13 (depends on 1)

The kiln of claim 1, said moisture detector comprising a water sensor detecting an amount of water removed by said dehumidifier and a controller to determine the drying rate inside the kiln interior based on the detected amount of removed water.

### Claim 14 (depends on 13)

The kiln of claim 13, wherein said water sensor is positioned in said water reservoir to detect a water level in said water reservoir.

### Claim 15 (depends on 1)

The kiln of claim 1, further comprising a vent located in the kiln body to vent excess air from said kiln interior.

### Claim 16 (depends on 15)

The kiln of claim 15, further comprising a damper positioned at said vent to prevent external air from entering said kiln interior through said vent.

### Claim 17

A kiln comprising:
a kiln body forming an enclosure with a kiln interior;
a solar heater outside of said kiln body to generate heated air;
a plenum coupled to said solar heater and said kiln body to provide the heated air to the kiln interior;
one or more circulation fans inside said kiln interior to circulate air inside said kiln interior;
a dehumidifier to remove air from said kiln interior, dehumidify the removed air, and introduce dehumidified air into said kiln interior; and
a moisture detection apparatus having a moisture detector to determine a drying rate inside the kiln interior, said moisture detection apparatus comprising:
one or more water reservoirs;
one or more inlet tubes coupled to said one or more water reservoirs and an output of said dehumidifier;
one or more inlet valves coupled to said one or more inlet tubes to direct water from the output of said dehumidifier to said one or more water reservoirs via one or more inlet tubes;
one or more outlet tubes coupled to said one or more reservoirs and an exterior of said kiln body;
one or more outlet valves coupled to said one or more outlet tubes and to said one or more reservoirs to direct water from said one or more reservoirs to the exterior of said kiln body;
one or more sensors positioned in said one or more water reservoirs to detect a water level;
a controller coupled to said one or more inlet valves, said one or more outlet valves and said one or more sensors, and operating the one or more inlet valves and the one or more outlet valves based on the detected water level.

### Claim 18 (depends on 6)

The kiln of claim 6, said controller further operating said one or more circulation fans, said heater fan, a backup heater, and said dehumidifier based on the drying rate or the detected water level.