Background Art The terms of"waste oil"used in this specification means not"industrial waste oil" generally used but waste cooking oil used in and discharged from houses restaurants, food processing companies and the likes, or waste oil such as animal oil which has a relatively high viscosity compared with industrial oil.

As the eating habits of the Korean are westernized, the consumption of fried foods such as potato chips, French fries, fried chickens and the likes is increased and the generation of waste oil is also increased. The waste oil (waste oil generated by plants, fats and the likes) has a BOD demand amount of about a million ppm, and it is higher than that of beanpaste pot stew (Korean Food) of about 35,000ppm and is over two hundred thousand times ppm compared with BOD demand amount of 5ppm for life of fishes. Thus, the waste oil is the principal of the river contamination. To prevent the river contamination, methods for reproducing the waste oil into fuel for

diesel engines or boilers have been proposed.

For the method for reproducing the waste oil as fuel, Korean Patent Publication No.

1999-16815 (published on March 15,1999) entitled"device for supplying car fuel using waste oil and method for manufacturing fuel"has been disclosed. The method for manufacturing fuel comprises the steps of performing esterification by dissolving waste oil refined by a filter into organic solvent and by adding alcohol including water; removing a water layer of a lower part by stationing solution obtained by the esterification for a predetermined period and by dividing into an upper part of an organic layer and the lower part of the water layer; removing the water layer of the lower part by dissolving residual water-soluble material in water by injecting water to the upper part of the organic layer, rinsing it several times and dividing again into the organic layer and the water layer; and obtaining mono ester capable of being used for car fuel by putting the obtained organic layer into a refining device and separating hexane through a difference of boiling point.

By removing water-soluble material from the waste oil of high viscosity through the esterification to improve the property of fuel into a state close to diesel oil, it is possible to reduce cost for waste oil disposal, to provide an import substitution effect by using fuel obtained from the waste oil, and to prevent environmental pollution by reducing toxic substances such as sooty smoke.

However, the conventional method for reproducing fuel using waste oil has a disadvantage that excessive waste water occurs by adding much water to melt water- soluble material, which remains in the organic layer of the upper part divided from the solution obtained by the esterification, into water.

In addition, the conventional method has another disadvantage that water cost is increased and additional water purifying facilities are needed.

Furthermore, if the water-soluble material remaining in the organic layer is divided again by injecting water, and the water layer is removed and the organic layer is directly used for fuel, equipments are corroded by organic solvent and water remaining in the organic layer. Thus, the process and a device for obtaining mono ester, which can be used for car fuel, by putting the collected organic layer into the refining device and dividing hexane through a difference of boiling point are complex and an expensive equipments must be installed.

Moreover, Korean Patent Publication No. 1999-70659 (published on September 15, 1999) entitled"method and device for reproducing waste oil into fuel"discloses a method and a device for reproducing waste oil into diesel fuel by applying ions formed by functional ceramic to molecules of waste oil to activate the molecules and increase minus potential of the molecules. However, it is only that viscosity of waste oil is lowered suitable for the diesel engine. Furthermore, because the lowered viscosity of waste oil is filtered by a general filter, environmental pollution due to imperfection combustion may occur and the engine may be damaged.

Additionally, Korean Patent Publication No. 1999-79052 (published on November 5, 1999) entitled"method and device for reproduction process of waste oil. In the prior art, the reproduction processing method includes the steps of : performing esterification by removing foreign matters using a filter and adding alkaline material as methanol and catalyst; removing glass alkali and dregs through natural precipitation and separating methyl-ester and glycerin by adding water; heating at a predetermined temperature to evaporate water; and making fuel through a refining process. However, foreign matters still remain because waste oil of high viscosity is filtered by the general filter, and it takes a long processing period of time because the separation of methyl-ester and glycerin and the refining process depend on natural

phenomenon.

Disclosure of Invention To solve the above problems in the conventional method for reproducing fuel using waste oil such as waste cooking oil and animal fat, it is an object of the present invention to provide a method for reproducing waste oil capable of lowering viscosity to be suitable as fuel for diesel engines and boilers, and capable of making fuel particles fine to improve fuel efficiency and to be harmless to environments.

That is, the present invention is to use waste oil into the diesel engine by a process including the steps of dividing waste oil by methyl-esterification through chemical treatment, adding a counteragent into an organic layer of an upper part and neutralizing, removing neutralized salt to reuse waste oil as phosphoric manure, and finally emulsifying by adding impact energy of ultrasonic wave to increase molecular motion and make reaction speed fast.

Moreover, it is another object of the present invention to provide a device of reproduction of waste oil, which can simplify a manufacturing process by increasing chemical and mechanical reaction speed of waste oil by chemically processing waste oil and directly applying ultrasonic wave, reduce a manufacturing cost and reduce environmental pollution by removing occurrence of waste water.

Brief Description of the Drawings Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawing in which: FIG. 1 is a vertical sectional view of a waste oil reproducing device according to a

preferred embodiment of the present invention; FIG. 2 is a vertical sectional view of a waste oil reproducing device according to another preferred embodiment of the present invention; FIGS. 3a and 3b are partially enlarged sectional views respectively showing an installation state of an oscillator for generation of ultrasonic wave of the waste oil reproducing device according to the present invention; FIG. 4 is a vertical sectional view of a centrifugal separator in the waste oil reproducing device according to the present invention; and FIGS. 5a, 5b and 5c are perspective views of rotating discs in the centrifugal separator of FIG. 4.

Best Mode for Carrying Out the Invention The present invention will now be described in detail in connection with preferred embodiments with reference to the accompanying drawings. For reference, like reference characters designate corresponding parts throughout several views.

A method for reproducing waste oil will be described hereinafter.

First, in a refining step, waste oil containing water, fatty acid, aldehyde, oxidized products and food scraps is collected and dregs and residues such as food scraps are removed through a filter. The waste oil, from which dregs and residues are removed, is maintained in the temperature of 50 to 80 C. At that time, an absorbent is added into the waste oil, and molecular motion is increased by ultrasonic wave and a mixing device to enlarge a contact area. Furthermore, to increase an absorbed level of foreign matters, the mixture is stirred for 20-40 minutes while ultrasonic impact energy of 15 KHz-100 KHz is applied. In the stirring step, the absorbent absorbs water, fatty acid, oxidized products, polymers and the likes, which prevent the methyl-esterification

reaction, through a physical cohesion. The absorbent cohered with the foreign matters is removed through a centrifugal separator and a filter of a high function. There are magnesium silicate, silica gel, silicic acid or aluminum used as the absorbent. The most effective absorbent is magnesium silicate. The waste oil refining step is a basic step for obtaining excellent regenerated fuel.

The step of performing methyl-esterification for using in diesel engines or boilers includes the steps of adding potassium hydroxide-methanol solution, which is made by melting potassium hydroxide into methanol, into the refined waste oil, and stirring in the temperature of 50-80'C for 30-65minutes for easiness of the reaction while applying ultrasonic impact energy. In the above step, fatty acids of triglyceride of high viscosity, which are the chief ingredients of the waste oil, are cut and discharged, and at the same time, methyl group is chemically cohered to fatty acid to be changed into methyl-ester. At this time, molecular weight is reduced to 1/3 and viscosity is also reduced to 1/10, thereby reducing boiling point and burning point.

The changed fatty acid methyl-ester has the number of C molecules similar to that of diesel oil, which is fuel of the diesel engines.

Continuously, the step for dividing the methyl-esterified reaction solution is to obtain light methyl-ester oil layer by passing the methyl-esterified reaction solution through a high-performance centrifugal separator. The oil layer contains fatty acid methyl- ester of 95% and methanol of 5%. By removing heavy glycerin and various compounds, only the methyl-ester oil layer used as fuel for the diesel engines or the boilers is obtained.

Since the methyl-ester oil layer contains a very small amount of methanol and potassium hydroxide, in a conventional method, residual potassium hydroxide is neutralized by evaporating methanol by reducing pressure and adding thin acid

solution. To remove water, neutralized compound and various oxidized substances existing by the acid solution used at the time of neutralization reaction, it is required to supply and dry a great deal of water for dividing water layer. Thus, there occur excessive costs and lots of waste water causing installation of clarifying facilities.

Furthermore, if the divided oil layer is directly used as fuel, organic solvent corrodes components and methanol is divided, and thereby the engine is stopped. Therefore, in the present invention, 3N phosphoric acid (H3 P04) is added into water of 5% by weight and mixed with methyl-ester oil without evaporating methanol. After that, when magnesium silicate is put into and mixed into methyl-ester oil, the mixture completely absorbs neutralized salt and oxidized products and the absorbent is simply removed by a high-performance (RPM 7500) centrifugal separator.

Finally, when bubble impact energy of ultrasonic wave generated from an oscillator is applied to the neutralized methyl-ester oil layer so that fuel is emulsified with oil through cavitation and fine emulsifying reaction, a small amount of water, methanol and methyl-ester, which are the neutralized oil layer, are emulsified, and then fatty acid methyl-ester, which is car fuel without phase separation, is obtained.

Meanwhile, in the step obtaining fatty acid methyl-ester by applying ultrasonic impact energy to the fatty layer, the methyl-esterification and the reaction period of time can be reduced perfectly by stirring using an impeller.

Next, a device for reproducing waste oil will be described.

As shown in FIG. 1, reference numeral 1 designates a first processing tank for adsorbing reaction prevention material using a magnet silicate, 2 designates a second processing tank for neutralization, methyl-esterification and emulsification, 3 designates an oscillator, 4 designates an impeller, 5 designates a motor, 6 and 17 designate three-way valves, and 7 designates a filter part.

The first processing tank 1 includes the filter part 7 connected through a tube to an upper end of a stirring space 12 divided by a bottom plate 14 of a body 11, an inlet 13 connected to the other upper end of the stirring space of the body 11 for supplying an absorbent or an additive, and a cover 15 coupled with an upper portion of the body 11 for sealing an upper portion of the stirring space 12. The motor 5 rotating the stirring impeller 4 disposed at the bottom plate 14 of the upper stirring space 12 of the body 11 is mounted on a lower space of the bottom plate 14. A heating pipe 9 for maintaining temperature is disposed on the stirring space 12 of the body 11. A circulation pump for removing foreign matters by recirculating solution inside the stirring space 12 through the centrifugal separator 16 and the filter part 7 is mounted on the bottom plate 14 of the stirring space 12.

An example of the centrifugal separator 16 is illustrated in FIG. 4. As shown in FIG. 4, a rotary shaft 62, which is connected with a power source (not shown), is rotatably mounted on the center of a sealed cylindrical body 61, and a shown in FIGS.

5a, 5b and 5c, a plurality of rotating discs 65a, 65b an 65c, each of which has a guide hole 63 and a through hole 64, are connected to the rotary shaft 62. The body 61 includes an inlet connected to an upper end thereof and outlets 67 and 68 connected to a lower end thereof for discharging oil and dregs, thereby separating oil and dregs through centrifugal force. Especially, the outlet 68 for discharging light oil is located in vicinity of the rotary shaft 62 within the body 61, namely, extends to a position where centrifugal force is applied smallest.

Furthermore, an oscillating part 31 of the oscillator 3 is fixed to the outer bottom of a bottom plate 14 of the first processing tank 1 to be contacted by supporting means.

The oscillator 3 is connected to an ultrasonic oscillating part 32 for controlling output sound and generates ultrasonic wave of 15 KHz-100 KHz to the solution filling a

reaction space 12 of the second processing tank 1, so that the molecular motion of solution is increased to enlarge the contact area and increase the adsorption level of foreign matters.

The second processing tank 2 includes a reaction space 22 formed at the upper portion divided by a bottom plate 24 of a body 21 for storing methyl-ester solution, which is oil to be regenerated as fuel for the diesel engines or the boilers after being processed in the first processing tank 1, a heating pipe 91 disposed on the reaction space 22 of the body 21 for maintaining temperature, a cover 25 coupled to the upper portion of the body 21 for sealing the reaction space 22, and a discharge pipe 26 connected to a lower side of the reaction space 22 of the body 21 for discharging emulsified fatty acid methyl-ester, which is fuel for the diesel engines and the boilers.

Furthermore, an oscillating part 31 of the oscillator 3 is fixed to the outer bottom of the bottom plate 24 of the second processing tank 2 to be contacted by general supporting means. The oscillator 3 is connected to an ultrasonic oscillating part 32 for controlling output sound and generates ultrasonic wave to the solution filling the reaction space 22 of the second processing tank 2, so that a small amount of water is emulsified to oil.

Additionally, the three-way valve 6 is connected between the first and second processing tanks 1 and 2, so that the phase-separated solution by the high- performance centrifugal separator 16 in the first processing tank 1 is discharged outside and the light oil layer is supplied to the second processing tank 2.

Meanwhile, it is preferable that the first and second processing tanks 1 and 2 and other components are made of material, which is not corroded by chemical agents.

Each pipe and inlet 13, which are connected to the first and second processing tanks 1 and 2, have general valves for opening and shutting respectively.

The heating pipe 9 disposed on the stirring space 12 of the first processing tank 1 and the heating pipe 91 disposed on the reaction space 22 of the second processing tank 2 transmit heat through thermal oil supplied from the outside or directly transmit heat by having a heating wire inside, thereby heating and/or keeping warm the stored contents at a predetermined temperature.

In another embodiment, as shown in FIG. 3a, the oscillating part 31 of the oscillator 3 generating ultrasonic wave of 15 KHz-100 KHz passes the bottom surface of the bottom plate 14, which forms the stirring space 12 of the first processing tank 1, or the bottom surface of the bottom plate 24, which forms the stirring space 22 of the second processing tank 2, and protrudes to the inside, so that ultrasonic impact energy generated from the oscillating part 31 of the oscillator 3 is directly applied to solution to increase efficiency. A retainer 33 is inserted into a part, where vibration is generated smallest, and fixed to the bottom plates 14 and 24 of the first and second processing tanks 1 and 2, and thus, load is not applied to the oscillating part 31 of the oscillator 3, liquid type oil is not leaked, and the oscillator 3 can be easily replaced with a new one. Moreover, because there is no loss of ultrasonic wave generated from the oscillator 3, the same ultrasonic wave as the initially mounted oscillator 3 can be transmitted to waste oil.

In a further embodiment, as shown in FIG. 3b, a multi-oscillator 3 having a plurality of ceramic oscillating elements is adopted to increase output three times.

Additionally, the oscillator 3 having one oscillating element is 45mm in a diameter of an ultrasonic transmission part but the oscillator 3 having three or more of oscillating elements is 30mm in the diameter of the ultrasonic transmission part. Thus, the multi-oscillator 3 can obtain power capable of cutting polymeric link by amplifying ultrasonic wave without using a separate horn. At this time, it is preferable that a

length of the oscillating part 31 of the oscillator 3 is 1/4 of ultrasonic wavelength oscillated in the oscillator 3.

Especially, to maximize ultrasonic impact energy of the oscillator 3, it is preferable that the structures of the first and second processing tanks 1 and 2 are designed such that liquid type oil exists in positions of 50mm and 150mm from the bottom plates 14 and 24 of the first and second processing tanks 1 and 2, that is, ultrasonic wave generating parts of the oscillator 3, in consideration that ultrasonic power is maximized at 1/4 and 3/4 positions of wavelength of ultrasonic wave where speed of ultrasonic wave of fatty acid and glycerin is 28 KHz, namely, 1400m.

In a still further embodiment, a stirring impeller 41 is mounted on the reaction space 22 of the second processing tank 2 and a motor 51 rotating the impeller 41 is mounted on a lower space of the bottom plate 24 to perform stirring and ultrasonic wave generation by the oscillator 3 at the same time, thereby reducing a chemical reaction period of time and an emulsification period of time.

To make mass production possible through a continuous process, the first processing tank 1, the circulation pump, the centrifugal separator and the filter part may be additionally mounted to the second processing tank. The first processing tank 1 performs refinement and phase separation and the second processing tank performs neutralization and emulsification.

An embodiment for reproducing fuel through the method and device for reproducing waste oil will be described.

First, waste oil, from which dregs are removed through the filter part 7, of 100kg is supplied into the stirring space 12 of the first processing tank 1. Magnesium silicate, which is absorbent, is added into waste oil of 0.5% by weight through the inlet 13 while heating and/or maintaining warm the stirring space 12 in the temperature of 50

- 80 C using heat generated from the heating pipe 9. The motor 5 operates for 20- 40minutes to rotate the impeller 4 while impact energy amplifying ultrasonic wave of 15 KHz-100 KHz, and the waste oil in which absorbent is added is stirred. To remove magnesium silicate cohered with the foreign matters using the centrifugal separator 16 of high function (RPM 7500) and the filter, the circulation pump 10 is operated and the waste oil is circulated through the filter part 7 of the upper portion, thereby refining the waste oil.

Since the refined waste oil is triglyceride of polymer material, potassium hydroxide- methanol solution, which is made by melting potassium hydroxide of lkg into methanol of 21.9kg having purity of 99%, is added into the refined waste oil through the inlet 23 for methyl-esterification. After that, while being maintained in the temperature of 50 ~ 80 C through the heating pipe 9, the mixture is stirred in the impeller 41 for 30-65minutes, and at the same time, ultrasonic impact energy is applied. In the above process, fatty acid is cut from triglyceride, and at the same time, methyl group is chemically cohered to fatty acid, thereby being changed into methyl-ester.

Glycerol is separated from the reacted solution of the methyl-ester waste oil by controlling RPM of the centrifugal separator 16. Since the separated glycerol cannot be used as fuel, glycerol is discharged to the outside through the three-way valve 6 and may be regenerated into material for manufacturing cosmetics. The methyl- ester oil of about 90% remains in the first processing tank 1.

Next, if 5% weight of water is added into the residual methyl-ester oil remaining in the first processing tank and the impeller 41 is turned, oil is first stirred. If magnesium silicate of 0.5% by weight and 3N phosphoric acid (H3 P04) of 0.05% (V/W) by weight are mixed in the first stirred oil and the impeller 41 is turned

for 20minutes, oil is second stirred. Then, oil is neutralized by magnesium silicate and 3N phosphoric acid (H3 PO4), and thereby, foreign matters of salt (K3PO4) and oxidized substances capable of being used as phosphoric manure are generated.

In addition, the foreign matters is simply removed by the high-performance (RPM 7500) centrifugal separator 16 of FIGS. 4 and 5a, 5b and 5c using a specific gravity difference. The process is not have to be performed in the first processing tank 1, and may be performed in the second processing tank by adding a circulation pump, the centrifugal separator and a filter part to the second processing tank.

Because the neutralized methyl-ester oil of the second processing tank 2 contains water of a small amount and methanol, ultrasonic impact energy of 15 KHz-100 KHz generated from the oscillating part 31 of the oscillator 3 operated by control of the ultrasonic oscillating part 32 is applied to emulsify water and methanol, so that fuel is emulsified with an atomization state of water and oil through the ultrasonic cavitation by which bubbles are collected, grown, pressed and destroyed, thereby obtaining fatty acid methyl-ester, which is car fuel of an emulsified state without being phase- separated. The emulsified fatty acid methyl-ester fuel contains methanol of about 5% and water of about 2%, and thus, fuel can be burned perfectly by micro explosion (aqueous reaction) due to temperature difference by water lain on oil when being injected into a vehicle or a boiler combustion chamber.

Moreover, in the neutralization step or the emulsification step, as shown in FIG. 2, if the mixture is stirred by the motor 51 and the impeller 41 mounted in the second processing tank 2, the reaction effect is increased to reduce the manufacturing period of time, and necessary temperature can be maintained through the heating pipe disposed in the second processing tank 2.

In the device according to the present invention, the division into the first processing

tank 1 and the second processing tank 2 is for mass production. If the filter part 7 and the circulation pump 10 mounted in the first processing tank 1 are mounted in the second processing tank 2 and the three-way valve 6 is removed, a single processing tank can process the stationing, phase-separation, neutralization and emulsification steps collectively, and thereby fatty acid methyl-ester can be obtained.

Industrial Applicability The fatty acid methyl-ester fuel obtained through the method and the device according to the present invention can be used as safe and good fuel without phase- separation. Furthermore, when the emulsified oil is burnt, water of the small amount contained in oil helps the perfect combustion of fuel through minute explosion, thereby resulting in excellent combustion and preventing environmental pollution.

Additionally, by the manufacturing device of the simple structure and the manufacturing process, the refinement, separation, neutralization and emulsification steps of waste oil are performed simply, thereby reducing waste oil disposal cost and costs for refining facilities.

Furthermore, the present invention can prevent generation of unnecessary foreign matters by reusing dregs, namely salt (K3PO4), which is generated during the neutralization process of waste oil, as phosphoric manure.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.