Patent Application
20080182213
1. Field of the Invention
This invention relates to the field of waste oil burning systems. More specifically, the present invention comprises a waste oil burning system having a preheated atomizing air feed.
2. Description of the Related Art
Combustion is one of the preferred methods of disposing of waste oils such as used engine oils, cooking oils, cutting oils, gear oils, hydraulic oils, and other difficult to burn liquids, such as glycerin and antifreeze. Waste oils do not burn cleanly or efficiently if the oil is not properly atomized. To improve efficiency, many facilities that burn waste oil preheat the oil. Preheating the oil lowers the viscosity of the oil so that it may be more readily atomized when mixed with air (such as when sprayed through an atomizing nozzle).
There are many disadvantages to preheating waste oils, however. First, the energy to preheat waste oils can be costly. Also, even the most controlled preheating processes can cause acceleration of chemical reactions within the waste oils which result in formation of deposits on heating surfaces. The fouling of the heating surfaces results in heating inefficiencies, requiring the preheater to be regularly cleaned and maintained. Furthermore, some of the deposits may break free of the heating surface only to foul other parts of the burner, including the nozzle and combustion chamber.
Accordingly, it would be desirable to have a waste oil burning system which is not costly to operate and avoids the problems associated with the preheating of waste oils.
The present invention comprises a waste oil burning system having a burner and a heat exchanger for preheating atomizing air before the atomizing air is supplied to the nozzle. The burner includes a fuel conduit for supplying waste oil to the burner and an air supply line for supplying atomizing air to the burner. The burner has a nozzle which atomizes the waste oil by mixing the waste oil with the air from the air supply line. The nozzle sprays the atomized waste oil into a combustion zone where the atomized waste oil is burned. An air-to-liquid type heat exchanger is positioned in the combustion zone, so that energy produced from the combustion of the waste oil preheats the air supplied through the air supply line before the air is mixed with the waste oil.
The present invention, waste oil burning system 38 is illustrated in
Air compressor 28 is provided to provide a continuous supply of atomizing air to burner 16 through air supply line 26. Air supply line 26 transports the atomizing air through combustion zone 24 where energy produced during the combustion of the waste oils preheats the atomizing air. A heat exchanger for preheating the air is positioned in combustion zone 24 and fluidly connected to air supply line 26. Heat exchangers of various designs may be employed for such a purpose. In the preferred embodiment, the heat exchanger includes a conduit or manifold which is heated by the energy produced during the combustion of the waste oils. As the atomizing air passes through the heat exchanger, the air is heated.
During start-up, a starter fuel feed is mixed with the waste oil feed for a period of time until the heat exchanger reaches the designed operating temperature. Storage vessel 18 is provided to maintain a supply of starter fuel sufficient to facilitate the combustion of the waste oil while the heat exchanger is brought to operational temperature. Fuel pump 20 supplies burner 16 with a continuous feed of starter fuel during start-up through fuel supply line 22.
As illustrated in
Nozzle 32 has fuel conduit 30 which transports waste oil through nozzle 32. The waste oil mixes with the atomizing air as it exits fuel conduit 30. Nozzle 32 sprays the waste oil and air mixture into combustion zone 24 where the waste oil combusts. Waste oil supply line 14 and fuel supply line 22 both feed into fuel conduit 30. As mentioned previously, fuel supply line 22 supplies starter fuel during start-up. Once heat exchanger 34 reaches operational temperature, only waste oil is combusted.
In the preferred embodiment, air supply line 26 feeds air to burner 16, then through combustion zone 24, then back to burner 16 where the air is discharged from air supply line 26 into nozzle 32. Those that are skilled in the art will know that the various materials and designs may be used for heat exchanger 34. In addition, the dimensions of heat exchanger 34 and the distance of heat exchanger 34 from flame 36 may all be adjusted so that the atomizing air enters nozzle 32 at the appropriate temperature. In the preferred embodiment, the atomizing air is heated to a temperature of at least 200 degrees Fahrenheit prior to entering nozzle 32. As illustrated in
Through experimentation it has been determined that waste oils having a flow rate of approximately 2.5 gallons per hour may be cleanly and efficiently combusted when mixed with atomizing air having a flow rate of 0.3 cubic feet per minute at a pressure of 7 psi and a temperature of 250 degrees Fahrenheit. In the referenced experiment, an external mix aspiration nozzle was used to mix the waste oil with the atomizing air. The waste oil was not preheated prior to being mixed with the atomizing air.
For start-up, a combustion enhancer was mixed with the waste oil for improved atomization and ignition. Also, atomizing air was provided at a flow rate of 0.8 cubic feet per minute until the atomizing air reached a temperature of 250 degrees Fahrenheit.
A control system for controlling the starter fuel and waste oil is illustrated in
During start-up, switch 50 may be adjusted to the “timed” mode so that fuel solenoid 44 opens and starter fuel is supplied for a period of time. Switch 50 is electronically connected with timer 52. Timer 52 is preferably adjustable so that the timing period may be changed as necessary. The period of time which fuel solenoid 44 is in the opened position may be experimentally determined to meet the requirements of the particular heat exchanger and flow rate of waste oil that is to be combusted. By the time fuel solenoid 44 closes, the atomizing air is hot enough to keep the burning process going without the aid of the starter fuel.
Switch 46 controls fuel solenoid 42. Fuel solenoid 42 controls the flow of starter fuel through a second fuel line. Switch 46 is electronically connected to timer 48. The second fuel line may be opened when larger amounts of starter fuel are needed. If the waste oil is very poor, either switch 46 or switch 50, or the two combined, may be turned to “continuous” mode so that a constant supply of starter fuel is provided throughout the burn time. It is also possible to turn off the supply of waste oil completely and burn only starter fuel until the desired operating temperature is attained.
The feed of starter fuel to burner 16 may also be controlled with a solenoid integrated with a temperature sensor and controller. A temperature sensor may be positioned in the air supply line downstream of heat exchanger 34. The temperature sensor may be configured to sense the temperature of the air before the air is mixed with the waste oil. When the temperature is less than 200 degrees Fahrenheit, the controller may open the solenoid to supply starter fuel to burner 16. When the temperature sensor observes an air temperature of at least 200 degrees Fahrenheit, the controller may close the solenoid in the starter fuel supply line, cutting off the starter fuel feed to the nozzle. It should be noted that the temperature sensor and controller may use a different set point than 200 degrees Fahrenheit.
In addition, multiple set points may be used to control the flow rate of starter fuel. This may be accomplished by using a solenoid that may be opened to various increments. For example, the solenoid may be set to a partially open position when the air reaches 200 degrees Fahrenheit. The solenoid may then be moved to a completely closed position when the air reaches 250 degrees Fahrenheit. Obviously, even more set points on solenoid positions may be incorporated to minimize the use of starter fuel.
The preceding description contains significant detail regarding the novel aspects of the present invention. It should not be construed, however, as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. As an example, combustion zone 24 may be an enclosed fire box or it may be completely external to burner 16. Thus, the scope of the invention should be fixed by the following claims, rather than by the examples given.
