The field of the invention is thermal conversion of waste vegetable and animal fats into liquid fuel products.

In result of various technological processes the waste vegetable and animal fats are produced, which are troublesome. These fats may be rancid, rotten, chemically, mechanically or biologically contaminated. Thus, they are not suitable for processing into soap, biodiesel or related products. Often, such fats accompany wastewater streams or they are collected from drains, grease traps or they are obtained when disposing dead animals. Such waste fats can be used in specifically adapted furnaces for burning. Alternatively, they are directed to fermenters where the fats are decomposed to biogas with certain yield. In Poland hundreds of tons of this type of waste are produces and there are no good methods for their disposal. The high energy value of animal fats as well as vegetable ones is basis for their use as an alternative fuel or even as a biofuel.

The various processes and apparatus for fat conversion in to the fuel or other suitable recycled product are described in the prior art.

PL291929 discloses a method that allows to obtain a diesel substitution for diesel internal combustion engines, heating oil, fuel oil and components for the preparation thereof, and esters or mixtures of esters with CI to C4 alcohols, fatty acids, while also high-percentage recovery of glycerol. The method consists of purification of the ester (fuel) phase in the process of alcoholysis of fats after mixing this phase with adsorbent materials, preferably clay, in an amount of from 0.1 to 12% by weight, in relation to the ester phase, preferably from 0.5 to 2.0 wt.%, preferably at a temperature of 50-80°C, preferably under reduced pressure, and then separated from the remainder of the filtrate in a centrifuge and/or filter press. Purification of the ester (fuel) phase may be preceded by neutralization and/or rinsing this phase with water, preferably at 60-65°C.

WO02068565 discloses a method and an apparatus for recycling of waste oil such as waste cooking oil or animal fat into fuel for diesel engines or boilers. The method of reproduction of waste oil includes the steps of: adding an absorbent into the waste oil from which dregs are removed at the temperature of 50-80°C, stirring the waste oil for 20-40 minutes while applying ultrasonic impact energy to the waste oil, and removing the absorbent cohered with oxidized substances, water and other contracted materials using a high-performance centrifugal separator and a filter; adding potassium hydroxide-methanol solution, which is made by melting potassium hydroxide in methanol, into the refined waste oil, and stirring in the temperature of 50-80°C for 30-65 minutes to carry out the reaction of methyl esterification, separating and removing glycerol from the methyl- esterified reaction solution to collect light oil; adding and mixing a predetermined amount of water into the collected oil; adding and neutralizing a small amount of 3N phosphoric acid (H ₃ P0 ₄ ) solution and magnesium silicate in the mixture, and removing salt and other oxidized products through the centrifugal separator of high function and the filter; and applying ultrasonic wave impact energy to the neutralized oil, emulsifying oil through cavitation phenomenon and obtaining fatty acid methyl-ester of an emulsified state without phase-separation.

KR101077923 describes apparatus for producing of biofuels from waste animal fats, in combination with waste oil. The apparatus comprises a tank for the animal fat such as animal and fish fat, oil reservoir comprising heating means for heating oil and for the preparation of biofuels, and an outlet for removing the biofuel; wherein the animal fat feeding pipe is connected to the lower part of the reservoir oil. In addition, the apparatus also includes a sieve for solids filtering from biofuel and means for removing particulate matter.

RU02354670 describes a method for waste oil recycling wherein said method comprises preparing an active agent by mixing quicklime ground to the size of 10 ^"3 -10 ^"5 m, the absorbent obtained by the pyrolysis of waste tires at a temperature of 850 to 1100°C after separating the metal wires and pulverization of the absorbent to the particle size being 10 ^"3 -10 ^"5 m and technical animal fat addition in the following proportions (% by weight): technical animal fat 1-3%, 18-22% absorbent and lime - remaining amount. All the ingredients are mixed vigorously with the waste oil with the addition of water, water is added in an amount corresponding to quick lime taking into account the water in the waste oil. The resulting product is treated with carbon dioxide for 10-15 min, and maintained in a sealed condition for 18 to 30 hours. Preferably, the fat technical is heated to a temperature of 45-50°C,

The difficulty in direct application of waste fats is based on their non-homogeneous composition, which results in the physical form of the waste (liquid or solid) and the presence of various impurities.

Surprisingly it has been found that under certain conditions waste fats, including waste vegetable and animal fats can be processed into liquid fuel of fuel oil with a very high yield.

The subject of the invention is a process for thermal conversion of waste vegetable and animal fats to liquid fuel products, wherein said process comprises steps of heating waste fats with the addition of at least one catalyst in a reactor at a temperature in the range of 200-280°C, transferring the mixture to a second reactor maintained at a temperature of 350-460°C, distilling off the products which are condensed in an external condenser. Preferably, the catalyst is introduced into fats and distributed in the fat phase prior to the directing the fats into the thermal reactor and the catalyst is carbonate of an alkali metal or alkaline earth metal, preferably sodium or potassium carbonate. Preferably, the catalyst is recovered, subjected to regeneration and returned to the processing cycle.

In a preferred embodiment the process comprises the step of pre-treating and/or filtering and/or drying of waste fats to remove mechanical impurities, water and/or proteins prior to the process.

By-products obtained by the process according to the invention, including carbon dioxide and hydrocarbon gas, are used as fuel additives in the process of the invention.

The process according to the invention is carried out at a higher or lower pressure then atmospheric pressure, preferably at atmospheric pressure. In a preferred embodiment of the invention the method comprises steps of heating waste fat in the tank and melting said fat at 70-100°C, keeping the constant bulk (volume) temperature, then charging the reactor with the catalyst, preferably in the form of finely ground particles, mixing thereof and increasing the temperature to 200- 280°C and maintain the mixture under these conditions for 0.1-6 hours and then introducing gradually in a controlled manner the mixture to a second reactor, wherein maintaining the temperature at 350-460°C and withdrawing the volatile products in the form of vapor from the reactor to the condenser, wherein said volatile products condense to form a major fuel product while the non-condensable gases are used for diaphragm heating of the first and/or the second reactor, then interrupting the process when the reaction rate drops significantly, to yield fuel product and carbonate sediments, which are used in quantity for the next cycle of treatment of waste fat, the process is then repeated periodically until the reaction rate drops significantly, after the last batch, the deactivated catalyst is collected from the second reactor and subjected to a regeneration by burning thereof. Preferably, the temperature in the first reactor is from 200 to 310°C and the mixture is maintained at this temperature for 0.1 to 6 hours and the temperature in the second reactor is from 350 to 460°C.

In a preferred method, the aqueous waste fat is subjected to . preliminary dehydration by heating thereof to the temperature of 120-140°C to evaporate the water.

Preferably the contents of the first reactor is stirred and gradually heated to a temperature of minimum 200°C and up to 310°C.

In the process according to the invention preferably the second reactor is purified using a portion of the carbonate deposits of fat, and after dissolution the mixture is poured into the first reactor.

The technological process involves heating the fats with the addition of catalysts in an adapted reactor and distilling off the product, which then condense in the outer condenser. The reactor process is preceded by a purification of fats from mechanical impurities and water and proteins, as long as they are an essential component of waste. The catalysts are recovered during the process and regenerated. The only by-products are carbon dioxide and small amounts of hydrocarbons of low boiling point, wherein said hydrocarbons also can be used as fuel additives. The reactor is adapted for recycling of wastes and can be heated electrically, but one can also use heating oil or gas burners. It is important to ensure stability of the temperature of the process and avoid large temperature differences in the heating surfaces to maximize homogeneity of the products obtained. The process of fat thermal treatment may be carried out under elevated or reduced pressure in relation to the atmospheric pressure, but it is also effective at normal pressure. This allows simplifying of the construction of apparatus wherein the process under normal pressure is carried out.

Direct energy use of waste fats is limited by the delivery temperature. At too low temperatures, the viscosity of vegetable oils greatly increases and they become solidified. Animal fats under normal conditions also are solid and their use in furnaces or panics is difficult. Fuel products obtained by new technology remains flowable even at low temperatures, similarly as fuels derived from petroleum.

Example 1

In a tank having a volume of 2 m ³ equipped with a heating jacket and a stirrer, a mixture of 655 kg of beef tallow, 245 kg of fat used for frying potatoes and 125 kg of porcine lard was heated. Once the mixture was melted and the temperature reached 80- 90°C, the reactor was charged with 87 kg of finely ground sodium carbonate. The reactor content was stirred and the temperature was raised to 260°C. While the mixture was maintained under these conditions for 4 hours, dissolution of the catalyst in a mixture of fat occurred. Thus prepared feedstock was introduced subsequently to a second reactor, wherein the temperature was maintained at 375°C. In the reactor, the pyrolytic decomposition of bonds in the fat molecules took place forming the volatile products which left the reactor as a vapor. These vapors were directed to the condenser, which condense thereof delivering a major fuel product. The non-condensable gases are used to heat the diaphragm heating system of the second reactor. The second reactor having a volume of 1 m ³ was feed with the flow rate of the raw material of 76 kg/h. The reaction rate gradually decreased as the used catalyst was gradually deposited in the second reactor, which reduces the heat transfer process. The amount of raw material fed into the second reactor was controlled and fresh portions of the hot raw material were added while the material was used. The purpose of this inspection was to avoid the risk of overfilling or excessive emptying of the second reactor. After approx. 18 hours, the efficiency of the process of main product formation decreased rapidly and the process was stopped. The amount of 843 kg of a pale yellow liquid product having a specific flavor was obtained. The density of the product was 877 kg/m ³ . After cooling of the second reactor the carbonate sediments were taken out from the reactor and used quantitatively for the next batch using the same amount of fat materials. After pre-heating treatment of the waste fat with the use of recycled catalyst fat was introduced into the second reactor at the same flow rate as the first batch and after 18 hours 831 kg of petroleum products were obtained with similar characteristics as the first batch. Complete production cycle was repeated four times more. Gradual decrease of productivity of the second reactor was observed, and the last batch carried lasted 21 hours. After completing this batch and collecting the deactivated catalyst from the second reactor, the catalyst was subjected to regeneration by burning thereof. After burning, almost quantitative recovery of the catalyst as originally used was obtained.

Example 2

The content of fat traps installed on the waste water stream at catering plants, with the waste containing 73% by weight of fat components, was initially purified. The fat waste was heated in the reactor until all water evaporated and the reactor contents reached temperature of 127°C. The dehydrated fatty waste was then filtered to remove all solid impurities, such as food scraps, pieces of plastic cutlery, fragments of polymer films and the like. Fats clarified this way in an amount of 980 kg were poured into the first reactor having a volume of 2 m equipped with heating jacket and agitator. Then, 110 kg of dry potassium carbonate was feed into the reactor. The mixture was stirred and heated gradually to 310°C and held at this temperature for a period of 3 hours to fully dissolve the catalyst particles. The resulting material was then fed to a second, smaller reactor equipped with an anchor stirrer moving near the surface of the reactor walls. The second reactor was electrically heated to a temperature of 380°C. The feeding of the raw materials to the second reactor lasted 18 hours. During this time, the condensate, being the major product of the process, was accumulated. 793 kg of liquid fuel product was collected. This product was yellow colour, had a specific odor, and its density was 875 kg/m . After partial cooling of the second reactor, 400 kg of fat extracted from waste grease traps was poured into said reactor followed by the agitation of the resultant slurry, which was then pumped into the first reactor. The cleaning of the second reactor was repeated twice, each time with 300 kg of fat. In result the second reactor was cleaned from the catalyst accumulated inside said reactor.

The content of the first reactor was subjected to the same thermal processes as previously described, except that no additional catalyst was added. The resulting material was progressively introduced as the second batch to the second reactor. After 18.5 hours, 789 kg of liquid products were collected. Then the steps of stripping the second reactor from accumulating catalyst particles were repeated four times with a fresh portion of fats and second reactor stream from the first reactor. Each batch was stopped when the receiving performance of the final product was significantly decreased. The last batch in the second reactor lasted over 21 hours.