Title:
WASTE OIL COMBUSTION APPARATUS
Kind Code:
A1


Abstract:
A waste oil combustion apparatus can use various kinds of waste oils and burn the same efficiently, and permits effective utilization of the thermal energy resulting from the combustion thereof. The apparatus includes a bottomed cylindrical combustion furnace, a waste oil supply unit for supplying waste oil into the furnace, an auxiliary-fuel supply unit for supplying auxiliary fuel for burning the waste oil in the furnace, an ignition burner for heating the furnace inside and the waste oil and auxiliary fuel to ignite the fuels, an air supply unit for supplying air to the furnace, and a controller for controlling each of the igniting burner, waste oil supply unit, auxiliary-fuel supply unit and air supply unit to act at a predetermined time and operate for a predetermined time. The waste oil is spirally swirled inside the furnace under the action of air from the air supply unit.



Inventors:
Fujita, Syuichiro (Ehime, JP)
Application Number:
12/127703
Publication Date:
01/01/2009
Filing Date:
05/27/2008
Assignee:
Fujita Manufacturing Co., Ltd (Ehime, JP)
Primary Class:
Other Classes:
110/238, 431/9
International Classes:
F23G7/05; F23C5/32; F23K5/10; F23N1/02
View Patent Images:



Primary Examiner:
LAUX, DAVID J
Attorney, Agent or Firm:
MAYER & WILLIAMS PC (Morristown, NJ, US)
Claims:
What is claimed is:

1. A waste oil combustion apparatus comprising: a bottomed cylindrical combustion furnace; a waste oil supplying means for supplying a waste oil into the combustion furnace; an auxiliary-fuel supplying means for supplying an auxiliary fuel for burning the waste oil in the combustion furnace; an ignition means for heating the combustion furnace inside and the waste oil and auxiliary fuel to ignite the fuels; an air supplying means for supplying air to the combustion furnace; and a controller for controlling each of the igniting means, waste oil supplying means, auxiliary-fuel supplying means and air supplying means to act at a predetermined time and operate for a predetermined time, the waste oil supplying means supplying the waste oil in such a manner that the latter is spirally swirled inside the combustion furnace under the action of air supplied from the air supplying means.

2. The waste oil combustion apparatus according to claim 1, wherein the waste oil supply means and air supplying means supply the waste oil and air, respectively, from near an open end of the combustion furnace in such a manner that the waste oil and air are spirally swirled down along the inner surface of the combustion furnace toward the bottom of the combustion furnace.

3. The waste oil combustion apparatus according to claim 1, wherein the waste oil supplying means further includes a pressure regulator for supplying the waste oil into the combustion furnace under a predetermined pressure, and a heater that uses the heat of combustion from the combustion furnace to heat the waste oil.

4. The waste oil combustion apparatus according to claim 2, wherein the waste oil supplying means further includes a pressure regulator for supplying the waste oil into the combustion furnace under a predetermined pressure, and a heater that uses the heat of combustion from the combustion furnace to heat the waste oil.

Description:

CROSS REFERENCE TO RELATED APPLICATION

The present invention contains subject matter related to Japanese Patent Application JP 2007-52837 filed in the Japanese Patent Office on Mar. 2, 2007, the entire contents of which being incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a combustion apparatus using waste oils such as discarded lubricant, engine oil or the like as main fuel.

Recently, the regulations on the industrial wastes have been tightened more and more. Large costs have been required for disposal of the waste oils including discarded animal oils such as beef tallow, vegetable oils such as soy-beam oil or mineral oils such as lubricant, insulation oil, engine oil, etc. Under these circumstances, it has been proposed to utilize such waste oils as fuel for combustion apparatuses such as a boiler, burner, etc.

However, used soy-beam oil, which is a vegetable oil, for example, has a high ignition point and is not easy to burn since it contains impurities in volume. To solve this problem, a combustion apparatus using waste oils as auxiliary fuel has been proposed in Japanese Published Unexamined Patent Application No. H08-334220 (Patent Document 1). In such combustion apparatuses using waste oils as fuel, impurities contained in the oil cause carbon sludge to adhere to the inner wall of the combustion furnace or chamber, which leads to hard work for removing the carbon sludge.

The combustion apparatus disclosed in Patent Document 1 uses kerosene as main fuel and waste oil as auxiliary fuel. However, this apparatus should be able to burn waste oils more efficiently.

SUMMARY OF THE INVENTION

It is therefore desirable to overcome the above-mentioned drawbacks of the related art by providing a combustion apparatus using various waste oils each as main fuel and capable of efficiently burning the waste oil and utilizing the resultant heat energy effectively.

According to an embodiment of the present invention, there is provided a waste oil combustion apparatus including a bottomed cylindrical combustion furnace, a waste oil supplying means for supplying a waste oil into the combustion furnace, an auxiliary-fuel supplying means for supplying an auxiliary fuel for burning the waste oil in the combustion furnace, an ignition means for heating the combustion furnace inside and the waste oil and auxiliary fuel to ignite the fuels, an air supplying means for supplying air to the combustion furnace, and a controller for controlling each of the ignition means, waste oil supplying means, auxiliary-fuel supplying means and air supplying means to act at a predetermined time and operate for a predetermined time. The waste oil supplying means supplies the waste oil in such a manner that the latter is spirally swirled inside the combustion furnace under the action of air supplied from the air supplying means.

The combustion apparatus according to an embodiment of the present invention uses waste oils each as main fuel and is capable of burning the waste oils having been discarded as wastes in the past, which contributes to deployment of resources. According to the embodiment of the present invention, the waste oil supplying means supplies the waste oil in such a manner that the latter is spirally swirled inside the combustion furnace under the action of air supplied from the air supplying means, whereby the waste oil can be burned with an improved efficiency.

The foregoing and other features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal-sectional view of a waste oil combustion apparatus according to an embodiment of the present invention;

FIG. 2 is a perspective view, enlarged in scale, of a substantial part of the apparatus shown in FIG. 1;

FIG. 3 explains the flow of fuel and air from the fuel supply pipe in the intake pipe of the apparatus shown in FIG. 1, in which FIG. 3A is a cross-sectional view of the combustion furnace and FIG. 3B is a longitudinal-sectional view of the combustion furnace;

FIG. 4 is a sectional view of the intake pipe;

FIG. 5 shows a flow of operations made in the waste oil combustion apparatus shown in FIG. 1;

FIG. 6 is a perspective view of a rotary kiln connected to the waste oil combustion apparatus;

FIG. 7 is a schematic sectional view taken along the axis of rotation of the rotary kiln shown in FIG. 6, connected to the waste oil combustion apparatus;

FIG. 8 is a schematic sectional view taken perpendicularly to the axis of rotation of the rotary kiln connected to the waste oil combustion apparatus; and

FIG. 9 schematically illustrates an inner casing of the rotary kiln connected to the waste oil combustion apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of the present invention will be described in detail below concerning the embodiment thereof with reference to the accompanying drawings.

As shown in FIG. 1, the waste oil combustion apparatus, generally indicated with a reference numeral 1, includes an annular combustion cylinder 2, a combustion furnace 3 provided inside the combustion cylinder 2, an ignition burner 4 that heats the inside of the combustion furnace 3 to ignite the fuel and the like, a waste oil supply unit 5 to supply waste oil as main fuel into the combustion furnace 3, a kerosene supply unit 6 to supply kerosene as auxiliary fuel into the combustion furnace 3, an air supply unit 7 to supply air into the combustion cylinder 2, a duct 8 to supply heat resulted from the combustion of the waste oil in the combustion furnace 3 to a heat exchanger or the like connected to the waste oil combustion apparatus 1 for effective utilization of the heat, and a controller 10 to control the operation of the entire apparatus.

The combustion cylinder 2 is made of a heat resistant steel plate or the like. It includes a cylindrical annular portion 2a, a top plate 2b that closes the upper end of the annular portion 2a, and supporting members 2c provided near the lower end of the annular portion 2a to support the combustion furnace 3. In the combustion cylinder 2, the lower end of the annular portion 2a serves as a burning port. The duct 8 is connected to that lower end to supply the heat of combustion in the combustion furnace 3 inside the combustion cylinder 2 to the downstream.

As shown in FIG. 2, the annular portion 2a of the combustion cylinder 2 is of a double structure being hollow to have an inner space 11 formed therein and to which water is supplied. The annular portion 2a has a water inlet 12 provided on the peripheral surface near the lower end of the annular portion 2a at which the latter is connected to the duct 8, and the water inlet 12 communicates with the inner space 11. The annular portion 2a has a water outlet 13 provided on the peripheral surface near the upper end at which a top plate 2b is provided, and the water outlet 13 communicates with the inner space 11. Also, the annular portion 2a is connected at the water inlet 12 thereof to a water supply unit 14. Water supplied from the water supply unit 14 is charged into the inner space II through the water inlet 12, and it goes out of the inner space 11 through the water outlet 13. In the annular portion 2a, the water thus filled in the inner space 11 will serve as a coolant that cools the waste oil combustion apparatus 1. The water supply unit 14 is of a well-known type, for example, a pump.

The top plate 2b provided at the upper end of the annular portion 2a is a disc-shaped member that closes the upper end of the annular portion 2a. It has an air inlet 15 connected to a blower 16 and through which air is supplied into the combustion cylinder 2. The air inlet 15 is formed circular to blow air to between the combustion cylinder 3 and the annular portion 2a surrounding the former.

The supporting members 2c support the combustion furnace 3 formed like a footman. More specifically, each of the supporting members 2c is formed from a bar-shaped member extending from near the lower end of the annular portion 2a of the combustion cylinder 2 toward the inside of the annular portion 2a. The supporting member 2c is a little bent at the free end thereof toward the upper end of the annular portion 2a. Also, the supporting member 2c is longitudinally hollow (as indicated with a reference numeral 2d) from one end thereof to the other, allowing air to pass through. The supporting member 2c is connected at one end thereto to an air blower 9 which is an air source. The air blower 9 is to supply air to the combustion furnace 3. It blows air to the bottom of the combustion furnace 3 through the inner space 2d in the connected supporting member 2c to cool the combustion furnace 3.

The combustion furnace 3 is made of a heat resistant steel plate or the like to have the form of a bottomed cylinder. It is placed inside the combustion cylinder 2. The combustion furnace 3 has formed therein near an open end 3a thereof an insertion hole 18 in which there is inserted a supply pipe assembly 17 through which waste oil, kerosene and air are supplied from the waste oil supply unit 5, kerosene supply unit 6 and air supply unit 7, respectively, to the combustion furnace 3. The combustion furnace 3 has a bottom 3b on which there will be received the mist, not completely burned, of the fuels including the waste oil sprayed from the supply pipe assembly 17. The fuels, including the waste oil on the bottom 3b of the combustion furnace 3, are heated in the combustion furnace 3 for vaporization and burning.

The ignition burner 4 is connected to the supply pipe assembly 17. It uses kerosene, for example. The ignition burner 4 heats the inside of the combustion furnace 3 to ignite waste oil so that the waste oil combustion apparatus 1 can start combustion or other operation with only the waste oil. It should be noted that the ignition burner 4 is not limited to the above-mentioned type using kerosene but may be of a type using gas or the like.

The waste oil supply unit 5 includes a first waste oil tank 19 in which waste oil is stored, a second waste oil tank 20 to which the waste oil is supplied from the first waste oil tank 19, a heater 21 provided inside the second waste oil tank 20 to heat the waste oil in the second waste oil tank 20, a waste oil supply pipe 22 through which the waste oil is supplied from the second waste oil tank 20 into the combustion furnace 3, a waste oil pressure regulator 23 provided in the waste oil supply pipe 22 to regulate the pressure of the waste oil supplied from the second waste oil tank 20, and a waste oil supply/stop valve 24 to supply or stop the waste oil to the combustion furnace 3.

The first waste oil tank 19 stores waste oil as main fuel for use with the waste oil combustion apparatus 1. The second waste oil tank 20 is supplied with the waste oil from the first waste oil tank 19. Using a liquid level adjuster (not shown) including a float and needle, the second waste oil tank 20 stores the waste oil supplied from the first waste oil tank 19 under a constant pressure. Inside the second waste oil tank 20, there is provided a heater 21 that heats the waste oil in the tank to lower the viscosity of the waste oil. The heater 21 is of a well-known type, and its operation is controlled by the controller 10. Water is supplied to the inner space 11 of the combustion cylinder 2 and given the heat of combustion in the combustion furnace 3. The water thus heated is circulated through the water outlet 13 to the second waste oil tank 20 in which it further heats the waste oil being heated by the heater 21. At this time, the controller 10 makes a selection between the heat exchange by the discharged hot water from the combustion cylinder 2 and the operation of the heater 21 in response to the operational status of the combustion furnace 3.

Note that for a lower viscosity of the waste oil in the second waste oil tank 20, the latter may not be arranged to be supplied with the hot water from the combustion cylinder 2 as described above but may be provided in a position where it itself can be given the radiant heat from the combustion furnace 3.

The waste oil supply pipe 22 is connected to a fuel supply tube 29 (shown in FIG. 4), which will further be described later, in the supply pipe assembly 17 to supply the waste oil from the second waste oil tank 20 to the combustion furnace 3. The waste oil pressure regulator 23 is provided in the waste oil supply pipe 22 to regulate the pressure of the waste oil being supplied from the second waste oil tank 20 to the supply pipe assembly 17. The waste oil pressure regulator 23 is controlled by the controller 10 to regulate the pressure of the waste oil being supplied. The waste oil supply/stop valve 24 is provided in the waste oil supply pipe 22 and downstream of the waste oil pressure regulator 23 to adjust the supply of the waste oil from the second waste oil tank 20. Similarly to the waste oil pressure regulator 23, the waste oil supply/stop valve 24 is operated (opened or closed) under the control of the controller 10.

Note that the waste oil pressure regulator 23 and waste oil supply/stop valve 24 may not be arranged separately from each other as above but they may be of an integral structure capable of adjusting the supply of the waste oil through the waste oil supply pipe 22 and regulating the pressure of the waste oil in the waste oil supply pipe 22.

The kerosene supply unit 6 includes a kerosene tank 25 in which kerosene as auxiliary fuel is stored, a kerosene supply pipe 26 to supply kerosene from the kerosene tank 25 into the combustion furnace 3, a kerosene pressure regulator 27 provided in the kerosene supply pipe 26 to regulate the pressure of the kerosene supplied from the kerosene tank 25, and a kerosene supply/stop valve 28 to supply or stop the kerosene to the combustion furnace 3.

The kerosene tank 25 stores kerosene as auxiliary fuel for the waste oil combustion apparatus 1. The kerosene supply pipe 26 is connected to the fuel supply tube 29, which will further be described later, in the supply pipe assembly 17 to supply the kerosene from the kerosene tank 25 to the combustion furnace 3. The kerosene pressure regulator 27 is provided in the kerosene supply pipe 26 to regulate the pressure of the kerosene being supplied from the kerosene tank 25 to the supply pipe assembly 17. The kerosene pressure regulator 27 is controlled by the controller 10 to regulate the pressure of the kerosene being supplied. The kerosene supply/stop valve 28 is provided in the kerosene supply pipe 26 and downstream of the kerosene pressure regulator 27 to adjust the supply of the kerosene from the kerosene tank 25. Similarly to the kerosene pressure regulator 27, the kerosene supply/stop valve 28 is operated (opened or closed) under the control of the controller 10.

Note that the kerosene pressure regulator 27 and kerosene supply/stop valve 28 may not be arranged separately from each other as above but they may be of an integral structure capable of adjusting the supply of the kerosene through the kerosene supply pipe 26 and regulating the pressure of the kerosene in the kerosene supply pipe 26.

As shown in FIGS. 3 and 4, the supply pipe assembly 17 includes a fuel supply pipe 29 to which the waste oil supply pipe 22 and kerosene supply pipe 26 are connected, an air supply pipe 30 having the fuel supply pipe 29 provided therein and which is supplied with air from the air supply unit 7, and a heat shielding plate 31 provided to cover a portion, near the free end, of the air supply pipe 30. The supply pipe assembly 17 is inserted in the insertion hole 18 provided near the open end of the combustion furnace 3 as shown in FIG. 3 to supply fuel (waste oil and kerosene) and air into the combustion furnace 3.

The insertion hole 18 is to have the supply pipe assembly 17 inserted through it as above. It is formed so that the supply pipe assembly 17 is held tangentially to the inner circumference of the combustion furnace 3 as shown in FIG. 3A (cross-sectional view) and obliquely from above toward the bottom 3b of the combustion furnace 3 as will be seen in FIG. 3B (longitudinal-sectional view). This geometry is intended to swirl the fuel and air supplied from the supply pipe assembly 17 for efficient burning.

The fuel supply pipe 29 is connected to the waste oil supply pipe 22 and kerosene supply tube 26 to supply waste oil and kerosene into the combustion furnace 3. It is connected at one end thereof to the waste oil supply pipe 22 and kerosene supply pipe 26 to supply waste oil and kerosene as fuels into the combustion furnace 3, and projected at the other end thereof into the combustion furnace 3.

The air supply pipe 30 is larger in inside diameter than the fuel supply pipe 29 and is laid coaxially with the latter. The air supply pipe 30 is connected at one end thereof to the air supply unit 7 and projected at the other end into the combustion furnace 3. The air supply pipe 30 supplies air from the air supply unit 7 into the combustion furnace 3. Also, the end, projected into the combustion furnace 3, of the air supply pipe 30, is deeper in the combustion furnace 3 than the corresponding end of the fuel supply pipe 29. The free end, projected into the combustion furnace 3, of the air supply pipe 30, is somewhat reduced in inside diameter (as indicated with a reference numeral 30a). The smaller-diameter end 30a forms a Venturi tube that elevates the flow rate of supplied air to atomize waste oil etc. supplied from the fuel supply pipe 29 for spraying into the combustion furnace 3.

The heat shielding plate 31 covers the near free-end portion of the air supply pipe 30 to shield heat from the combustion furnace 3 in order to prevent the air supply pipe 30 from being overheated. The heat shielding plate 31 has an ignition hole 32 through which flame is taken in from the ignition burner 4.

The ignition hole 32 is provided in such a position near the end portion, inside the combustion furnace 3, of the heat shielding plate 31 that fuel from the fuel supply pipe 29 can be ignited by the flame from the ignition burner 4.

The air supply unit 7 is a blower connected to the air supply pipe 30 to supply combustion air into the combustion furnace 3 and to atomize waste oil from the fuel supply pipe 29 for spraying into the combustion furnace 3.

The duct 8 is to supply the heat of combustion developed in the combustion furnace 3 to a drying equipment which is located downstream of the waste oil combustion apparatus 1. The duct 8 is annular and generally equal in diameter to the combustion cylinder 2. It is bent for one and other ends thereof to form an angle of about 90 degrees between them. As shown, the duct 8 is of a double structure being hollow to have an inner space 33 formed therein as in the combustion cylinder 2 and to which water is supplied.

The duct 8 is connected at one end thereof to the bottom of the combustion cylinder 2 and at the other end to a rotary kiln 41 which will be described in detail later. Further, the duct 8 has a water inlet 34 provided at the peripheral surface thereof near the end at which it is connected to the rotary kiln 41 and which communicates with the inner space 33, and a water outlet 35 provided at the peripheral surface thereof near the end at which it is connected to the combustion cylinder 2 and which communicates with the inner space 33. The duct 8 is connected at the water inlet 34 thereof to a water supply unit 36 so that water is taken into the inner space 33 and discharged from the water outlet 35. The water thus filled in the inner space 33 of the duct 8 serves as a coolant to cool the waste oil combustion apparatus 1. The water supply unit 36 is of a well-known type, for example, a pump.

Note that the water supply unit 36 that supplies water to the inner space 33 of the duct 8 may not be provided separately from the water supply unit 14 that supplies water to the inner space 11 of the combustion cylinder 2 as above but a single water supply unit may be used to supply water to the inner spaces 33 and 11.

The controller 10 is to control the operation of the entire waste oil combustion apparatus 1. More specifically, the controller 10 controls the supply rate and pressure of water oil from the waste oil supply unit 5, those of kerosene from the kerosene supply unit 6, and supply rate etc. of air from the air supply unit 7. The controller 10 includes a CPU (central processing unit), a memory and a timer, which are connected to each other via a bus or the like. The memory in the controller 10 has stored therein an operation timing program for each unit. The timer in the controller 10 counts a start time of each operation. CPU in the controller 10 counts a time count supplied from the timer, and controls the operation of each unit according to a corresponding program evoked from the memory. The controller 10 is connected to the ignition burner 4, waste oil supply unit 5, kerosene supply unit 6, air supply unit 7, air blower 9, water supply units 14 and 36, blower 16, etc. and controls outputs from these units.

Next, the operation for combustion of waste oil in the waste oil combustion apparatus 1 constructed as having been explained above will be explained with reference to FIG. 5. As shown, in step S1, the user turns on the power supply to -the waste oil combustion apparatus 1. In step S2, the controller 10 puts, into operation, the ignition burner 4, waste oil supply unit 5, kerosene supply unit 6, air supply unit 7 and blower 16. Then, waste oil, kerosene and air supplied to the combustion furnace 3 are burned while being swirled down spirally along the inner surface of the combustion furnace 3 toward the bottom 3b and then swirled up from the bottom 3b toward the open end of the combustion furnace 3 as shown in FIG 3.

In step S3 the controller 10 determines whether a predetermined time, for example, five minutes, has elapsed after each unit is put into operation in step S2. If the controller 10 has decided in step S3 that the predetermined time has not elapsed, it will repeat the operation in step S3. In case the controller 10 has decided that the predetermined time has elapsed, it will go to step S4. Each unit is operated for the predetermined time in step S3 in order to heat the inside the combustion furnace 3 by the ignition burner 4 to produce an atmosphere for easy combustion of the waste oil.

Next, in step S4, the controller 10 controls the kerosene supply unit 6 to stop the supply of kerosene and the ignition burner 4, to stop the operation. At this time, the controller 10 controls the waste oil supply unit 5 and air supply unit 7 to keep operating.

Thus, in the waste oil combustion apparatus 1, waste oil and air are supplied from the waste oil supply unit 5 and air supply unit 7, respectively, into the combustion furnace 3 so that only the waste oil will be burned as fuel. At this time, the waste oil, kerosene and air supplied from the supply pipe assembly 17 into the combustion furnace 3 of the waste oil combustion apparatus 1 are swirled down along the inner surface of the combustion furnace 3 toward the bottom 3b of the furnace 3 and then swirled up from the bottom 3b, which will assure efficient and stable combustion of the waste oil. Also, since the waste oil combustion apparatus 1 is so arranged that after elapse of the predetermined time, supply of the kerosene is stopped for combustion of the waste oil alone. Thus, it is possible to limit the consumption of the kerosene. Further in the waste oil combustion apparatus 1, the blower 16 blows air into the space between the combustion cylinder 2 and combustion furnace 3 from the upper end toward lower end of the combustion cylinder 2 to guide the heat of combustion and flame in the combustion furnace 3 into the duct 8 (as indicated with a reference symbol A in FIG. 1).

In the waste oil combustion apparatus 1, with the fuels and air being supplied into the combustion furnace 3 from the supply pipe assembly 17 provided at a predetermined angle in relation to the combustion furnace 3, the waste oil can be burned more efficiently and positively. Also, since during operation of the waste oil combustion apparatus 1, namely, during combustion of the waste oil, the combustion furnace 3, combustion cylinder 2, duct 8, etc. are cooled while the air blower 9 and water supply units 14 and 36 are in operation, the durability of the entire apparatus is much improved. Further, since the controller 10 of the waste oil combustion apparatus 1 can lower the viscosity of the waste oil by controlling the operation of the heater 21 of the waste oil supply unit 5, it is possible to assure efficient and positive combustion of the waste oil.

Moreover in the waste oil combustion apparatus 1, since it is possible to burn the waste oil efficiently and stably, the heat of combustion can be utilized for various purposes.

For one of such purposes, the rotary kiln 41 may be connected to the downstream of the waste oil combustion apparatus 1 having been explained above, namely, to the end of the duct 8 to build a drying system for metal chips resulted from machining. This drying system can effectively utilize waste oil to dry the metal chips for recycling.

The rotary kiln connected to the waste oil combustion apparatus 1 will be explained below with reference to the accompanying drawings. In the rotary kiln 41, metal chips 44 resulted from machining, fed from on a belt conveyor 42 into a feeding hopper 43, are guided by means of a spiral conveyor 45 into a rotary kiln body 51, and then heated with hot air introduced into an outer casing 56 of the rotary kiln body 51 from an end of the latter opposite to the feeding hopper 43 of the rotary kiln body 51, as shown in FIG. 6. The rotary kiln 41 includes a support base 52, a rotary kiln body 51 supported on the support base 52 by means of support rollers 53 provided on the support base 52, and a motor 54 to rotate the rotary kiln body 51.

The support base 52 is made of a heat resistant steel plate or the like. The plurality of support rollers 53, motor 54, etc. are fixed in place on the top of the support base 52. It supports the rotary kiln body 51 on contact with the support rollers 53.

The support rollers 53 on the support base 52 are to support the rotary kiln body 51 rotatably. For example, four support rollers 53 may be provided on the support base 52.

The rotary kiln body 51 rotatably supported on the support rollers 53 is of a double structure including the outer casing 56 and an inner casing 55 provided in the outer casing 56 as shown in FIGS. 6 to 8.

The inner casing 55 of the rotary kiln body 51 is made of heat resistant steel or the like to be generally cylindrical. At one end 55a of the inner casing 55, there is provided the spiral conveyor 45 into which metal chips 44 to be dried are put. The inner casing 55 is supplied at the other end 55b thereof with the heat of combustion from the waste oil combustion apparatus 1. Also, the inner casing 55 has provided on the inner surface 55c thereof a plurality of first feed vanes 57 that move the metal chips 44 fed from the spiral conveyor 45 in a direction from the one end 55a to the other end 55b as shown in FIGS. 7 to 9.

The first feed vanes 57 are provided intermittently on the inner surface 55c of the inner casing 55 to project inwardly of the latter and depict a virtual spiral extending from the one end 55a toward the other end 55b. The first feed vanes 57 are fixed obliquely in a direction in which rotation of the inner casing 55 converts circumferential motion into axial motion The inner casing 55 is rotated along with the outer casing 56, so that the first feed vanes 57 move the metal chips 44 put in the inner casing 55 in a direction from the one end 55a to the other end 55b while shaking them The first feed vanes 57 are intermittently disposed in order to forward the heat of combustion supplied from the waste oil combustion apparatus 1 in a direction toward the one end 55a of the inner casing 55.

The outer casing 56 having the inner casing 55 provided therein made of a heat resistant steel plate or the like to be generally cylindrical. The outer casing 56 is large enough in diameter to house the inner casing 55, and provided concentrically with the inner casing 55. One end 56a of the outer casing 56 is opposite to the one end 56a. As shown in FIG. 2, the outer casing 56 has provided on the inner surface 56c thereof a plurality of second feed vanes 58 that take in the heat of combustion from the waste oil combustion apparatus 1 and move, to the other end 56b of the outer casing 56, the metal chips 44 which are to be passed from the other end 55b of the inner casing 55 to the other end 56b of the outer casing 56.

The second feed vanes 58 are provided intermittently on the inner surface 56c of the outer casing 56 to project inwardly of the latter and depict a virtual spiral extending from the one end 56a toward the other end 56b. The second feed vanes 58 are fixed obliquely in a direction in which rotation of the outer casing 56 converts circumferential motion into axial motion The second feed vanes 58 are directed crosswise in relation to the first feed vanes 57. The outer casing 56 is rotated along with the inner casing 55 to move, by the second feed vanes 58, the metal chips 44 transferred from the inner casing 55 in a direction from the other end 56b to the one end 56a while shaking them. Similarly to the first feed vanes 57, the second feed vanes 58 are intermittently disposed in order to forward the heat of combustion supplied from the waste oil combustion apparatus 1 in a direction toward the one end 56a of the outer casing 56. The outer casing 56 further has provided on the outer surface 56d thereof rings 59 which are received on the support rollers 53, and a transmission member 61 that transmits the driving force from the motor 54 to the rotary kiln body 51 through a change belt 60.

The rings 59 are positioned on the outer surface 56d of the outer casing 56 for engagement on the support rollers 53. The transmission member 61 is annular to extend over the outer surface 56d of the outer casing 56, and positioned to face the motor 54. It is a kind of rack, for example, which is in mesh with the chain belt 60.

The rotary kiln body 51, having the double structure including the inner and outer casings 55 and 56 as above, is coupled by a coupling member 62 to each other to be concentric with each other. The coupling member 62 is to couple the inner and outer casings 55 and 56 securely to each other at the one end 55a, for example, of the inner casing 55, whereby rotation of the outer casing 56 by the motor 54 leads to similar rotation of the inner casing 55. In the rotary kiln body 51, since the direction of the first feed vanes 57 spirally provided in the inner casing 55 is different from that of the second feed vanes 58 also spirally provided in the outer casing 56, the metal chips 44 in the inner casing 55 and those in the outer casing 56 can be moved in different directions with the inner and outer casings 55 and 56 being rotated in the same direction

Note that the coupling member 62 may not be provided in a limited place such as the one end 55a of the inner casing 55 but may take any form or may be provided in more than one place so long as it can securely couple the inner and outer casings 55 and 56 to each other so that they are concentric with each other.

The spiral conveyor 45 to feed the to-be-dried metal chips 44 to the one end 55a of the inner casing 55 is generally cylindrical. It has provided therein a vane 63 that moves the supplied metal chips 44. The spiral conveyor 45 has connected thereto a motor 64 that rotates the vane 63. The spiral conveyor 45 has the feeding hopper 43 installed at one end 45a thereof, and is inserted at the other end 45b thereof in the one end 55a of the inner casing 55. The vane 63 of the spiral conveyor 45 extends spirally to move the metal chips 44 from the one end 45a toward the other end 45b.

Note that the spiral conveyor 45 may not be constructed as above but may be of any structure so long as it can move the metal chips 44 into the inner casing 55.

The feeding hopper 43 installed to the spiral conveyor 45 is to feed the metal chips 44 to the spiral conveyor 45. The feeding hopper 43 has, for example, a vibrator etc. (not shown) and feeds a predetermined amount of the metal chips 44 to the spiral conveyor 45 under the effect of vibration given by the vibrator.

The rotary kiln 41 further has a blower 65 for cooling the surface of the rotary kiln body 51, that is, the outer surface 56d of the outer casing 56, and a blower 66 for cooling the metal ships 44 already dried and going to be discharged from the rotary kiln body 51 at the one end 56a of the outer casing 56 while forwarding the heat of combustion from the waste oil combustion apparatus 1 into the rotary kiln body 51. The rotary kiln 41 also has provided at the one end 56a of the outer casing 56 a duct 67 which guides air from the blower 66.

In the rotary kiln 41 constructed as above, the motor 54 is driven to rotate the rotary kiln body 51 and take in the heat of combustion from the waste oil combustion apparatus 1 into the rotary kiln body 51 from the other end 56b of the outer casing 56. In this condition, the metal chips 44 are fed by the spiral conveyor 45 from the one end 55a of the inner casing 55, and shaken and moved by the first feed vanes 57 from the one end 55a to the other end 55b while being heated. At the other end 55b of the inner casing 55, the metal chips 44 take a position near the waste oil combustion apparatus 1 which is a heat source, and thus dried and transferred to the other end 56b of the outer casing 56. Further, the metal chips 44 are shaken and moved by the second feed vanes 58 from the other end 56b to one end 56a of the outer casing 56. That is, they are moved away from the waste oil combustion apparatus 1 which is the heat source, while gradually releasing the heat. Finally, the metal chips 44 thus heated and dried are discharged from the one end 56a of the outer casing 56.

In the above rotary kiln 41, since the metal chips 44 are dried in both forward and backward ways, the rotary kiln body 51 can be designed shorter in whole length. Therefore, the rotary kiln 41 can be formed smaller. The reduction in whole length of the rotary kiln body 51 of the rotary kiln 41 permits to have the waste oil combustion apparatus 1 operate with a lower output. Further, in the rotary kiln 41, since the first and second feed vanes 57 and 58 are provided intermittently to depict a virtual spiral, arrival of the heat of combustion from the waste oil combustion apparatus 1 at the one ends 55a and 56a of the inner and outer casings 55 and 56, respectively, can be controlled appropriately to prevent the temperature from being sharply elevated in a position near the other end 55b.

Moreover, since the inner and outer casings 55 and 56 of the rotary kiln 41 are coupled to each other by the coupling member 62, they can be rotated by a single motor 54, which contributes to power saving.

Also, a drying apparatus including the waste oil combustion apparatus 1 and rotary kiln 41 connected to each can use waste oil as main fuel to dry the metal chips 44. Namely, the embodiment of the present invention permits more effective use of resources and space saving.

Note that the first and second feed vanes 57 and 58 are not limited to the aforementioned ones but the feed vanes may be designed to have a variable tilt angle, height, etc. in the axial direction for moving the metal chips axially at a variable speed corresponding to the uniform rotation of the rotary kiln body 51. More specifically, the first feed vanes 57 are designed to have an increased height and tilt angle at the one end 55a for moving the metal chips 44 toward the other end 55b at an increased speed, while having a decreased height and tilt angle at the other end 55b for having the metal chips 44 stay for a longer time to be long exposed to the heat of combustion from the waste oil combustion apparatus 1.

It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.