GENERAL FEATURES:

In the preparation of soybeans for oil extraction the bean needs to be heated and conditioned to the correct temperature and moisture. Also, the hull (outer shell) needs to be removed from the bean to increase the protein content of the meal. The Crown Jet Dryer is designed to heat the hull quickly causing the hull to shrink, loosening the hull from the bean for easy removal in additional processing equipment.

The basic principle of operation is as follows: The beans enter the jet dryer through an inlet hopper or rotary feeder at a temperature of approximately 1400 F (600 C). The beans are conveyed through the dryer with a wire belt that allows air to pass through the belt and the bed of beans. Recycled air is used via a forced air fan traveling through the jet dryer a cyclone and air heater making the process more efficient and a better control over the conditioning of the beans. In order to evenly heat and prepare the bean for hull removal it is necessary to mix or stir the bed of beans while it is conveyed through the dryer before being discharged. The beans are discharged at a temperature of 1700 F to 1950 F (770 C to 900 C).

COMPONENT DESCRIPTION:

The Jet Dryer consists of an inlet hopper or rotary feeder, main dryer assembly, discharge spout, dust hopper, air hood and external air jet manifolds with dampers.

The inlet hopper has flange connections for the inlet and outlet, access doors, and internal adjustable distribution plates.

The main dryer assembly consists of the main support structure or weldment, belt support rollers, bed stirring rods, adjustable wear liner, inlet diverter plate, wire belt conveyor, drive cage, idler roll and the drive assembly. There are flanged inlets and outlets for the recycled air connections. The internal air manifolds for stirring the bed are welded internally to the main support structure.

The bean discharge spout has bolted flange connections and an access door for inspection and sampling.

The dust hopper is bolted to the bottom of the main dryer assembly and includes access door(s) for inspection and cleanout. Its discharge is flanged to allow the attachment of the fines clean out conveyor and or fines rotary valve. The air hood is bolted to the top of the main dryer assembly and has a flanged outlet for the recycled outlet air. It includes a large access door and several smaller inspection doors.

Finally, the external air jet manifolds and dampers are bolted to the side of the main dryer assembly and distribute air to the internal manifolds.

All components of the jet dryer must be insulated to prevent heat loss, condensation and potential injury to personnel. Note: When insulating, consider access to all bolted flanges and adjustment fasteners. Insulation and labor are not included in Crown Iron Works' scope of supply.

FUNCTIONAL DESCRIPTION:

The beans are fed into the jet dryer through the inlet hopper or rotary feeder depending upon the number of jet dryers in the dehulling process. The inlet hopper or rotary feeder distributes the beans across the full width of the jet dryer.

The beans are conveyed through the dryer to the discharge spout by a moving belt. The belt speed is approximately five to fifteen feet per minute depending on the size of the dryer and residence time needed. As the beans are conveyed through the jet dryer air is recycled through the bed of beans, which is typically 4" to 6" (10 cm to 15 cm) deep. The main recycled air uses high volume low velocity air in order to maintain controlled fluidized bed of beans. This fluidized bed of beans however does need to be stirred or mixed in order to evenly heat, dry and condition the bean. The mixing of the beans is done with air rather than by a mechanical means. A portion of this main recycled air is diverted via a auxiliary jet nozzle fan which blows the air up through the bed of beans using high velocity air jets. The air jets are controlled by the dampers on the external air manifolds of the jet dryer and the nozzle fan damper. This also partially fluidize the bed of beans and provide the necessary mixing along with the internal static bed stirring rods that extend down into the bed of beans.

In the final conveying inside of the jet dryer before the beans are discharged there is a temperature transmitter. It is important to monitor the discharge temperature of the beans exiting the jet dryer in order for the remaining dehulling process to work properly.

The energy used for drying and heating of the beans is taken from recycled air, which passes through steam-heated air coils. By maintaining the proper humidity and temperature in the air being recycled will determine the amount of heating and drying that will occur. This is controlled by using the three control dampers found in each air loop, the recirculation, fresh air inlet and exhaust air dampers.

Retention time is a very important factor in determining the amount of drying that occurs in the jet dryer and is controlled by the speed of the drive cage, which drives the wire belt. The drive cage speed is controlled by a variable frequency driven motor.

The fines and dust that fall through the wire belt are conveyed out of the dust hopper via the fines clean-out conveyor and or fines rotary valve and reintroduced into the process down stream.