Wireless temperature sensing and control system for metal kiln and method of using the same

#Not applicable.

#This invention relates principally to a metal furnace or kiln, and more particularly to a temperature sensing and control system for rotary aluminum delacquering kilns using wireless thermocouples or comparable temperature sensing devices.

#It has for some time been a standard practice to recycle scrap metals, and in particular scrap aluminum. Various furnace and kiln systems exist that are designed to recycle and recover aluminum from various sources of scrap, such as used beverage cans (“UBC”), siding, windows and door frames, etc. One of the first steps in these processes is to use a rotary kiln to remove the paints, oils, and other surface materials on the scrap aluminum (i.e. “feed material”). This is commonly known in the industry as “delacquering.” Delacquering is typically performed in an atmosphere with reduced oxygen levels and temperatures in excess of 900 degrees Fahrenheit. The temperature at which the paints and oils and other surface materials are released from the aluminum scrap in the form of unburned volatile gases is known as the “volatilization point.” One such typical aluminum recycling system utilizes a rotary kiln to delacquer the aluminum. Many of these systems utilize a recirculating heat apparatus comprising a burner with a blower to direct heat into the kiln, and a recovery device that collects exhaust heat from the kiln and recirculates the recovered heat into the heat flow for the kiln.

#The illustrative embodiments of the present invention are shown in the following drawings which form a part of the specification:

#FIG. 1 is a schematic of an aluminum rotary kiln delacquring system incorporating one embodiment of the present invention;

#Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

#In referring to the drawings, a schematic embodiment of the novel wireless temperature sensing and control system for metal kiln 10 of the present invention is shown generally in FIG. 1, where the present invention is depicted by way of example as integrated into a representative mass flow delacquering system X with a rotary aluminum kiln 12 having a delacquering zone 13 within the kiln 12. As can be seen, a set of four independent high temperature thermocouples 14, 16, 18 and 20, are positioned along the length of the kiln 12. In practice, the thermocouples 14, 16, 18 and 20 are positioned with at least the temperature sensing portion of the thermocouple exposed to the delacquering zone 13 within the rotary kiln 12. All of the thermocouples 14, 16, 18 and 20 are configured to detect temperature readings in the kiln 12, including temperature readings in excess of the melting point of aluminum, and are further configured to transmit the temperature readings they sense inside of the kiln 12 via radio signals to a receiving device or receiver 22 that is external of the kiln 12. Alternately, the thermocouples 14, 16, 18 and 20 could be operatively connected to a wireless transmitter (not shown) that would transmit the temperature readings to the receiving device or receiver 22.

#Aluminum feed material 26, which is ready for the delaquering process, is supplied to the kiln 12 through a feed material control chute 11, which regulates the rate at which the feed material is supplied to the kiln 12. The material then travels through the kiln 12 as the kiln 12 rotates about its central axis, and the material 26 is then discharged through a discharge chute 15, which regulates the rate at which feed material is discharged from the kiln 12. In order to reach and maintain temperatures sufficient to delacquer aluminum feed material 26 in the depicted system X, the kiln 12 receives heated air from a burner 30 and a burner bypass pipe 32. The burner 30 receives ambient temperature air, at a temperature of approximately 70 degrees F., from a combustion blower 34 and recirculated gases, at a temperature of approximately 500 degrees F., from a variable speed recirculation blower 36 which in turn receives the recirculated heated gases that have passed through the kiln 12. Combustion gases are controllably supplied to the burner 30 through a mass flow controller 31. The combustion blower 34 also drives the ambient temperature air into an afterburner 35 attached to the burner 30. Oxygen can be controllably injected as desired directly into the afterburner 35 through a mass flow controller 37. A thermocouple 39 positioned near the exit for the afterburner 35 takes temperature readings of the gases as they exit the afterburner. The thermocouple 39 connects to the combustion gas mass flow controller 31 and a mass flow controller 41, positioned between the combustion blower 34 and the burner 30, such that the mass flow controllers 31 and 41 regulate the flow of combustion gases and air, respectively, in response to the temperature readings from the thermocouple 39, so as to automatically control the burner operation to control the temperature of the gases supplied through a supply pipe 114.