Furnace Including Localized Incineration of Effluents

The invention relates generally to furnaces, and more particularly to the incineration of undesired effluents given off by products processed within the furnace.

The thermal processing of product within a furnace, such as the curing of epoxies or cements, can result in outgassing of undesired effluents or volatiles from the product into the atmosphere within the furnace. The effluents produced by the thermal processing of the product must themselves be processed before being released to the atmosphere. One manner of processing the undesired effluents is to incinerate them, while another manner of processing the undesired effluents is to condense and collect them. Either way of processing the unwanted effluents requires a large amount of energy since the effluents must be brought to a very high temperature for incineration or brought to a very low temperature for condensation and collection. Additionally, incineration of undesired effluents is generally done in separate combustion chambers or afterburners. However, this manner requires the addition of a separate housing for the combustion chamber or afterburner, the delivery of the effluents from the furnace to the combustion chamber or afterburner via a conduit of some type, and the provision of additional energy required by the combustion chamber or afterburner for incineration.

The present invention relates to a furnace for thermally processing products which give off undesired effluents or volatiles. The furnace includes a heating source which is used for thermal processing the products and for the incineration of undesired effluents which result from thermal processing of the products within the furnace. The heating source comprises a hot wire disposed within an apertured tube, which is at a temperature above the ignition point of the undesired effluents. As the effluents pass into the tube through the apertures, they are incinerated, thereby producing an exhaust that is generally pollution free. The heat required to incinerate the undesired effluents is also used to provide heat to the furnace for the thermal processing of product, thereby using the normal furnace power to provide a second function of incineration within the system.

The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a partially broken away schematic illustration of a furnace including a heating source for incineration of undesired effluents according to the invention;

FIG. 2 is a cross-sectional schematic illustration of the furnace of FIG. 1 further including an external afterburner; and

FIG. 3 is a partially broken away schematic illustration of a heating source according to the invention.

FIG. 1 shows a convection furnace 100 according to the present invention for thermally processing product 70 which may give off undesirable effluents or volatiles. Typically, the furnace 100 includes a support source 90, which frequently comprises a conveyor assembly, for transporting product 70 through the furnace chamber 101, and a heating source 60 for thermally processing the product 70. A recirculating device such as a fan or blower assembly 54 is provided to recirculate the furnace atmosphere through the heating source. A vent 40 is provided to exhaust the furnace atmosphere outside the furnace housing 10. A control-valve 45 controls the venting of the furnace atmosphere outside the furnace 100. The high-temperature heating source 60 serves to incinerate the undesired effluents produced by the thermal processing of the product 70 and also provides normal furnace requirements.

More specifically, the support assembly 90 is used to transport product from a furnace inlet 20 into heat transfer proximity with the heating source 60 for a predetermined period of time, then to a furnace exit 30. The transport assembly can be a conveyor such as rollers, a conveyor belt or chain, a walking beam or any other known device for transporting product within a furnace.

In an alternate embodiment the support assembly may be stationary within the housing and the product 70 to be thermally processed placed into the furnace through a furnace opening such as furnace inlet 20. Such placement can be by means external to the furnace or can be manual. After the thermal processing and incineration of undesired effluents has taken place, the product 70 is removed from the furnace via furnace inlet 20.

A fan assembly 54, or other gas moving device, provides air flow across the elements of the heater, resulting in a flow of heated air exiting first heating source 60 directed toward the product 70. As the product 70 is heated by the heating source 60, the product gives off undesired effluents. The heating source 60 may comprise any suitable number and configuration of heaters and heater units.

The heating source 60 provides heat at a temperature above the ignition point of the undesired effluents which are present within furnace atmosphere 100 as a result of the thermal processing of product 70. The heating source 60 can be an open flame, hot wire or other type of heating source. In a preferred embodiment, the heating source 60 comprises a thin wire 62 disposed in a tube 64 having apertures 65 arranged along the length of the tube 64 (FIG. 3). The heating source 60 is located within the furnace cavity in a position perpendicular to a portion of the gas circulation flow path in the furnace. In this manner a portion of the circulating gas passes around the tube 64 and some of the gas enters the tube 64 through the apertures 65 and comes into heat transfer proximity with the hot wire 62. The heating source 60 provides heat at, for example, approximately 700.degree. C., which is above the ignition temperature of most hydrocarbons. The incineration of the hydrocarbons results in carbon monoxide and water.

Heating source 60 provides heat at a temperature above the ignition point of the effluents that are in the atmosphere of the furnace cavity 101. As a result of heating source 60 providing heat at a temperature above the ignition point of the effluents, the undesired effluents are incinerated thereby removing them or greatly reducing the presence of them. Consequently, the exhaust produced is generally pollution free, with all or substantially all of the undesired effluents removed therefrom. The after product of this incineration can then be more safely vented into the atmosphere through vent 40 and/or more easily processed. Alternately, heating source 60 can have its own vent 160 which includes control-valve 162, for exhaust of the incineration byproducts outside the furnace housing 10. The thermally processed product 70 can then be removed from furnace 100 via outlet 30.

For example, the products 70 being thermally processed may be automotive brake shoes. An epoxy is used to secure brake pads onto the automotive brake shoes. In this instance the epoxy requires curing at 300.degree. C. in order to securely attach the brake pads onto the brake shoes. During the curing of the epoxy, undesired volatiles or effluents, in this instance hydrocarbons, driven from the epoxy and into the atmosphere of the furnace 100. Environmental concerns and regulations require that the amount of hydrocarbons released into the atmosphere be below a certain level. In order to safely vent the atmosphere outside the furnace, the undesired effluents must be either reduced or removed.

The heating source 60 is constantly enabled and is regulated by a controlling device 130 so that heating source 60 is employed for normal furnace power. The controlling device 130 may also be in communication with a sensor 140 which detects the presence and amounts of effluents, as would be known in the art. The controlling device 130 activates the heating source 60 when the heat is called for. The sensor 140 may also be used to control a secondary incinerator (not shown) or to slow the support assembly in order to get the hydrocarbon levels reduced.

In some instances the atmosphere within the furnace housing 10 has an amount of effluents which can be reduced but not completely eliminated by the heating source 60. To address this instance, the embodiment of FIG. 2 is employed wherein an afterburner 110 is physically located outside the furnace 100, and is coupled to the furnace 100 by conduit 120. The exhaust resulting from the incineration within the furnace 100 is then vented to the afterburner 110 through vent 40 via control-valve 45 and conduit 120 for complete incineration or further reduction of the remaining effluents. In such an embodiment as this, the workload of the afterburner 110 is reduced since the heating source 60 of furnace 100 has removed a percentage of the effluents from the furnace atmosphere.

Having described preferred embodiments of the invention it will now become apparent to those of ordinary skill in the art that other embodiments incorporating these concepts may be used. Accordingly, it is submitted that the invention should not be limited to the described embodiments but rather should be limited only by the spirit and scope of the appended claims.