ES2884927T3 - Regeneration of used oils - Google Patents

Abstract

Process for the recovery of waste from the regeneration of used oils that provides a treatment of the residue contained in at least one centrifugal separator (5), active in a process for the regeneration of used oils, characterized in that said residue is subjected to a stage decantation, to separate the solid from the liquid, because said solid is subjected to a drying stage and because the processed solid is mixed with bitumen, coming from the fractional column distillation of the centering of the at least one centrifugal separator (5).

Description

DESCRIPTION

Regeneration of used oils

The present invention relates to a process for recovering residual products from the regeneration of used oils, useful for increasing the fraction of products suitable for sale after regeneration of the oils, mainly used non-edible oils.

The use of lubricants—oils and greases of various kinds—has been in fashion since the beginning of mechanics. Said use is essential when there are mechanical parts that slide with respect to each other, to make said movement occur as smoothly as possible, without the moving parts getting stuck together, preferably without removing flakes of material that come off these pieces. In addition, lubrication significantly reduces friction, reducing energy consumption and allowing better performance.

In particular, the lubricants are used in the internal combustion engines of vehicles, for example motor vehicles. In them, extremely fast sliding movements lead to very high temperatures, also supported by the effects of internal combustion. Another important use is in machine tools. For this reason, lubricants undergo a series of reactions, caused by the high temperatures that arise in these situations; in particular, pyrolysis, cracking, condensation, hydrogenation, dehydration and dehydrogenation reactions take place, so that splits and recombinations of the molecules that form the lubricants take place. This causes the chemical composition of lubricants to change over time; which implies, quite obviously, that the physical and chemical-physical characteristics of lubricants also change over time. For this reason, over time, lubricants usually lose their slip-aid properties and can even be dangerous for the mechanical parts to which they are applied. This is aggravated by the fact that small flakes of metal or metal oxides nonetheless become detached from moving parts and remain suspended in the oil, and that solid, abrasive polymers are often formed—with the reactions previously treated. At this point, or better said, before this point, it is appropriate to replace the lubricants, with the operation known in the jargon as "oil change", removing the used lubricants and adding new ones.

Unfortunately, most of the lubricants used for internal combustion engines are already polluting substances; processing certainly does not help make the oils less dangerous. For this reason, according to the law, used oils are collected by the so-called mandatory consortiums, to avoid their dumping on the ground and in the aquifer stratum, where they would harm food safety.

Industrial lubricants are added to automotive lubricants, so the quantities of used oil that must be disposed of are definitely important. Unfortunately, despite the creation of mandatory consortiums, recovered used oils only represent approximately one third of total used oils, and the rest continues to be lost in the environment, with ecological damage and, as will be seen below, also economic damage.

Starting in the 1960s, with the development of ecological awareness, people began to try to recycle used oils, in order to obtain a product that could be reused in some way, in order to reduce the need for its disposal. .

The first processes were those with sulfuric acid and with liquid propane. That is to say, the oils are processed by adding sulfuric acid or propane, to eliminate a good part of the impurities contained in the used oils. However, the acid process has been practically abandoned, due to the considerable contamination problems that it implies.

In fact, the process with sulfuric acid causes the formation of acid sludge, which retains significant amounts of oil inside and also contains polymeric compounds and heavy metals; this sludge is therefore difficult to remove. Normally, said disposal is carried out in a landfill, preferably after neutralization, which, however, increases the volume of the same sludge to be disposed of. For this reason, the sludge combustion route has been tried, which, however, has turned out to be impractical.

Thus, other processes have been developed, starting with the one already mentioned, which makes use of propane.

The acid processing stage is totally replaced by a clarification with liquid propane. Propane is chosen as the hydrocarbon because it is easily liquefied and has a low density once liquefied. Therefore, it acts as a diluent for the oils to which it is added, to allow the separation of a high-density phase — containing polymers with a high molecular weight and heavy metals — from a second fraction, consisting of clarified oils and dehydrated. Therefore, the propane is removed and is recycled by mixing with the incoming oils.

Next, hot filtration is carried out, which allows the recovery of a gaseous fraction. TO Then it is finished with the decolorization and deodorization of the content.

However, this process, which allows higher yields to be obtained, still has some drawbacks. First, handling the highly flammable propane can be hazardous to plant labor. In addition, some of the propane is, however, trapped in the asphalt that forms as a by-product; this presence rules out the use of the bitumen obtained as a by-product for the manufacture of roads, with the notable limitation of the market and the consequent economic damage. Therefore, the bituminous fraction in this process is simply a waste, which must be eliminated and to which value cannot be given, as would be desirable instead. Finally, the process is inherently much more expensive than the sulfuric acid process.

In more recent times, used oil re-refining processes have been developed, using fractional distillation and other processes. Some processes aim to obtain a product to be burned, to completely eliminate the waste, with energy recovery. Other processes have given rise to reusable products, after suitable processing, to obtain new lubricants. The applicant, in particular, has been very active in this field, filing several patents for regeneration processes that have made it possible to significantly increase the yields of useful products. Basically, these processes allow the obtaining of bases for lubricants —which constitute the most valuable product—, bitumen and the rest are by-products that must be eliminated and burned to obtain the heat necessary to carry out the processes.

Bitumen is a relatively poor product, less expensive and therefore less profitable compared to lubricant bases. However, it does have a certain market, especially for road construction. With the Italian patent No. 102015000018543 and with the patent EP 3098291, the applicant revealed a method for the recovery of the bitumen fraction produced together with the bases for lubricants, to obtain a higher quality product, which could be sold as a mixture. mother or as a base for inks and the like. In this way, even the bituminous fraction has become more attractive and its production more profitable. In practice, in said document, the applicant taught how to recycle all the residual solid fractions, subjecting them to a new crushing stage, also separating a liquid phase, which constituted a higher quality bitumen and a solid phase, which was sent again to the initial stages of regeneration.

Different patent documents, including some by the same applicant, detail the use of centrifuges to improve the separation of the portion of lubricant to be recovered from the impurities to be removed. In particular, Italian patent No. 102015902347524 discloses the use of centrifugation of the liquid to be regenerated, which occurs between a flash expansion distillation stage and a packed column distillation stage. This centrifugation, together with the vacuum obtained through a ring pump, greatly promotes the elimination of the solid particles contained in the used oil, which reaches the filled column already highly purified, to significantly increase the fraction recovered and allow a longer useful life of the catalysts used in this regeneration. However, a solid residue remains in the centrifuge – the particles mentioned above – which is now removed. Therefore, the residue from the centrifuge remains today in the fraction to be eliminated from the oils that are regenerated and represents a cost and a burden for the environment.

Patent US 3,625,881 relates to the recovery of oil from the crankcase by flash expansion vaporization, mixed with a hydrocarbon oil in the presence of an alkali. Fractional distillation steps also take place.

The problem at the base of the invention is to propose a process for the recovery of used oils that overcomes the aforementioned drawbacks and that allows further boosting the recovery of used oil, valuing an additional part of the waste (the residue in the centrifuge), today day to remove, to further reduce sludge and be economically more advantageous. This object is achieved by means of a process for the recovery of waste from the regeneration of used oils that provides a processing of the residue contained in at least one centrifugal separator, active in a process of regeneration of used oils, characterized in that said residue is subjected to a decantation step, to separate the solid from the liquid, because said solid is subjected to a drying step and because said processed residue is ready to be mixed with the bitumen, coming from a fractional distillation column. According to a second aspect, the present invention refers to a plant for the regeneration of used oils, comprising at least one centrifugal separator, a fractional distillation column and a refining unit by hydrorefining, characterized in that, downstream of the outlet of the waste from said centrifugal separator, comprises at least one decanter and a dryer at the end of which the processed solid exits, ready to be mixed with the bitumen supplied by the pipe, coming from a fractional distillation column. According to a third aspect, the present invention refers to a bitumen, obtained as a fractional distillation tail in a process for the regeneration of used oils, characterized in that a solid residue is added to it in a centrifugal separation stage, processed in a process as described in the first aspect of the present invention. The dependent claims describe preferred features of the invention.

Other features and advantages of the invention are in any case more apparent from the following detailed description of a preferred embodiment, given purely as a non-limiting example and illustrated in the accompanying drawings, in which:

the fig. 1 represents a block diagram of a plant for the regeneration of used oils, where the present invention can be implemented; Y

the fig. 2 represents a detail of fig. one.

According to fig. 1, the used oil to be regenerated —which contains many different types of impurities— enters through inlet 1 and is supplied to a distillation column by flash expansion 2. Possibly, the oil to be regenerated can be enriched with a base, preferably a base strong, such as sodium hydroxide and/or, preferably, a potassium hydroxide, to eliminate the acidic agents that contaminate the oil to be regenerated. In column 2, the temperature is maintained above the boiling temperature of water —preferably at 130-140 °C, at a pressure of about 250 torr— and the separation of an aqueous phase occurs, comprising water, already present in the waste supplied in 1, the water in which the strong base was dissolved and the water formed from the reaction of the base with the false agents found in the oil, which leaves column 2 as water vapor , which contains light cleavage products of the oil from outlet 3. From outlet 4, on the other hand, comes the oil that has to undergo the additional regeneration process. The oil is thus supplied to a centrifugal separator 5, where the oil that must continue its regeneration is separated from the sediments, mostly solid in suspension, consisting of carbonaceous agents that are harmful to the mechanisms to be lubricated. The centrifugal separator provides a turbine having a rotational speed of 5,000-6,000 revolutions per minute. After separation in the centrifugal separator 5, the part of the oil to be regenerated leaves through pipe 6, while the solid material —the residue— is eliminated through pipe 7.

Pipe 6 supplies a heat exchanger 8 (for example, a furnace), where the temperature of the oil is brought to a suitable value for subsequent fractional distillation, which occurs in column 9, to which it is supplied by the pipe 10. Said temperature is above 300 °C, preferably ranging between 300 and 400 °C. The useful fractions of the product leave column 9 through lines 11-14 and are supplied to a hydrorefining reactor 15, from where, after hydrorefining treatment, at a temperature ranging between 280 and 360 °C, at a pressure ranging between 50 and 120 bar, come out in 16 as bases for lubricants, ready to be treated by the manufacturer together with the new oil fractions, to be put back on the market in the desired formulations.

The tail of column 9 exits through pipe 17 and consists essentially of bitumen, to be reused for less noble uses, such as asphalting roads and waterproofing roofs.

Pipe 7 coming out of centrifugal separator 5 supplies the waste from separator 5 to a settling and drying unit 18, from where the processed solid exits at 19, ready to be mixed with the bitumen supplied by pipe 17, coming from the fractional distillation column 9. Unlike what happens with the solid that comes out directly as waste from the centrifugal separators 5, it has been found that the solid processed according to the present invention is perfectly miscible with the bitumen and gives the latter properties useful, until today not even imaginable, such as greater durability and less noise.

Fig. 2 shows in more detail the solid waste processing part, the true core of the present invention.

Pipe 7 carries the material to be recovered to a decanter 20, of a type known per se. The floating part of the contents of the decanter 20, which contains mainly water, is taken and sent through the pipe 21 to the wastewater processing unit, to be treated in a known manner and discharged into the sewer. In this way, most of the water in the solid is removed, which means that today these solids cannot be mixed with the bitumen. The heavier and more viscous lower part is discharged by the decanter 20 onto a conveyor belt 22. The drying devices 23 act on the conveyor belt 22. In essence, the decanting and drying unit 18 comprises a decanter 20 and a dryer. Said dryer preferably comprises a conveyor belt 22 and one or more drying devices 23. Said drying devices 23 can be of various types. One can proceed by subjecting the conveyor belt 22 to the action of a vacuum or hot air, a stripping step with steam, air or nitrogen or another inert gas can be envisaged. Said drying stage occurs at a temperature that preferably ranges between 50 °C and 300 °C, preferably between 80 and 280 °C, more preferably between 110 and 180 °C, so as not to alter the composition of the solid, while water is effectively removed from it. Said drying step preferably occurs at a pressure ranging between 10 and 450 torr, in a more preferred mode between 50 and 800 torr, in the most preferred mode between 200 and 450 torr, to further accelerate the elimination of water as steam. of water. As the conveyor belt 22 advances the material from the settler 20 in the direction of arrow F, the material will lose water, gradually dehydrating. At the end of the path of the conveyor belt 22, the material, once dry, is discharged through the pipe 19. As seen in fig. 1, is then rejoined with pipe 17: the material contained in pipe 19, after undergoing the treatment just described, is able to mix perfectly with the bitumen coming out of pipe 17 —unlike what used to happen before—and is therefore re-united with it and sent for sale as bitumen, a less fine fraction than that of lubricant bases, but which is nonetheless suitable for sale and which it does not require additional treatment for its removal and, due to the treatment according to the present invention, finer than bitumen as it is. In this way, a fraction of the material to be regenerated that until now was going to be rejected —with the costs that this entails— becomes be part of a salable fraction, in addition to that, ennobled, so that it implies both an economic and ecological benefit. Preferably, at the joining point between the pipes 17 and 19, a mixer is provided so that the final product is a perfectly homogeneous bitumen. This procedure is clearly different from the one illustrated in patent EP 3098291. In fact, in that document it was foreseen that the solid residue of the centrifugation would be crushed, separated into a solid fraction and a liquid fraction and that the liquid fraction would be used as bitumen. In this case, on the other hand, it has surprisingly been found that, without proceeding to additional crushing stages, which are expensive, but proceeding only to a standard decanting stage plus drying, the solid can be used directly as bitumen, which allows that it has a more remarkable recovery of material compared to what happened in the past, with a significant increase in the quantity of salable bitumen, in addition to excellent quality —as mentioned, of greater value than that of the bitumen itself— and, consequently, with less energy consumption and less expense for waste disposal.

The bitumen obtained according to the present invention can rightly be called "ecological bitumen", since, as mentioned, it allows a significant reduction in final waste, which would have to be disposed of with a not inconsiderable environmental impact. However, it is understood that the invention should not be considered limited to the particular arrangement illustrated above, which constitutes only one exemplary embodiment thereof, but that different modifications are possible, all within the scope of a person skilled in the field, without departing from the scope of protection of the invention, as defined by the following claims.

In particular, the present invention extends to the case in which the centrifugal separation occurs in multiple partial flows. In this case, multiple centrifugal separators 5 operating in parallel are provided. Similarly, the decanting and drying unit 18 may comprise multiple decanters 20 operating in parallel.

LIST OF REFERENCE CHARACTERS

1 Ticket

2 Rapid expansion distillation column

3 Output (of 2)

4 Output (of 3)

5 Centrifugal separator

6 Pipe

7 Pipe

8 heat exchanger

9 Fractional distillation column

10 Supply pipe (of 9)

11 Pipe

12 Pipe

13 Pipe

14 Pipe

15 Hydrorefining reactor

16 Output (of 15)

17 bitumen pipe

18 Settlement and drying unit

19 bitumen pipe

20 Decanter (of 18)

21 Pipe

22 conveyor belt

23 Drying Devices (from 18)

Claims (14)

1. Process for the recovery of waste from the regeneration of used oils that provides a treatment of the residue contained in at least one centrifugal separator (5), active in a process for the regeneration of used oils, characterized in that said residue is subjected to a decantation stage, to separate the solid from the liquid, because said solid is subjected to a drying stage and because the processed solid is mixed with bitumen, coming from the fractional distillation in column of the centering of the at least one centrifugal separator (5) . 2. Process as in 1), characterized in that said centrifugal separator (5) provides a turbine having a speed ranging between 5,000 and 6,000 rpm. 3. Process as in 1) or 2), characterized in that said drying step occurs at a temperature ranging between 50 °C and 300 °C. 4. Process as in 3), characterized in that said temperature ranges between 80 °C and 280 °C. 5. Process as in 3) or 4), characterized in that said temperature ranges between 110 °C and 180 °C. 6. Process as in any one of the preceding claims, characterized in that said drying step occurs at a pressure ranging between 10 and 450 torr. 7. Process as in 6), characterized in that the pressure ranges between 50 and 800 torr. 8. Process as in 6) or 7), characterized in that the pressure ranges between 200 and 450 torr. 9. Plant for the regeneration of used oils, comprising at least one centrifugal separator (5), a fractional distillation column (9) and a hydrorefining unit (15), characterized in that , downstream of the outlet of the residue of said centrifugal separator (5), comprises at least one decanter (20) and a dryer (22; 23) at the end of which the processed solid leaves (in 19), and is mixed with bitumen supplied by the pipe (17), coming from of the fractional column distillation of the centering of the at least one centrifugal separator (5). 10. Plant as in 9), characterized in that said dryer comprises a conveyor belt (22) and one or more drying devices (23). 11. Plant as in 10), characterized in that said drying devices (23) cause the conveyor belt (22) to be subjected to the action of a vacuum, hot air, steam dragging, air or nitrogen or another inert gas. Plant as in any one of claims 9) to 11), characterized in that multiple centrifugal separators (5) operating in parallel are provided. 13. Plant as in any one of claims 9) to 12), characterized in that multiple settlers (20) operating in parallel are provided. 14. Bitumen obtained as tailings from the fractional distillation of the concentrate of a centrifugal separation stage in a process for the regeneration of used oils, characterized in that a processed solid from the centrifugal separation stage is added, where the processed solid is treated in a process as in any one of claims 1) to 8).