REGENERATION OF USED OILS

Abstract

 A process for the enhancement of wastes of the regeneration of exhaust oils is described, which provides a treatment of the residue contained in at least a centrifuge active in a regeneration process of exhaust oils. Said residue undergoes a decanting step, to separate the solid from the liquid and said solid undergoes a drying step.
According to a second aspect, a plant for the regeneration of exhaust oils is described, comprising at least a centrifugal separator, a fractioned distillation column and a hydrogenrefining unit. Downstream of the waste exit of said centrifugal separator, said plant comprises a decanter and a dryer.
According to a third aspect, a bitumen is described, obtained through a process and with a plant as described earlier.

Description

[0001] The present invention refers to an enhancement process of waste products of the regeneration of exhaust oils, useful for increasing the fraction of products apt to be sold following the regeneration of oils, mostly used non-edible oils.

[0002] The use of lubricants - oils and fats of various types - has been fashionable since the beginning of mechanics. Such use is essential when there are mechanical parts which slide one with respect to the other, to cause such movement to occur in the smoothest possible manner, without the moving parts getting jammed in each other, preferably without removal of flakes of material coming off such parts. Moreover, lubrication remarkably reduces frictions, reducing energy consumption and allowing better performances.

[0003] In particular, lubricants are used in internal combustion engines for vehicles, for example for motor vehicles. In them, the extremely fast sliding movements bring to very high temperatures, supported also by the effects of internal combustion. Another important use is in tool machines. For this reason, lubricants undergo a series of reactions, caused by the high temperatures which arise in these situations; in particular, pyrolysis, cracking, condensation, hydrogenation, dehydration and dehydrogenation reactions occur, so that cleavages and recombinations of the molecules forming lubricants take place. That causes the chemical composition of lubricants to change over time; that implies, rather obviously, that also the physical and chemical-physical features of lubricants change over time. For this reason, in time lubricants normally lose their gliding-assisting properties and can even become dangerous for the mechanical parts they are applied to. This is made worse by the fact that small flakes of metal or of metal oxides detach nevertheless from the moving parts and remain suspended in oil and that solid, abrasive polymers often form - with the previously discussed reactions. At this point, or rather, before this point, it is suitable to replace the lubricants, with the operation known in jargon as "oil change", eliminating used lubricants and adding fresh ones.

[0004] Unfortunately, most lubricants used for internal combustion engines are substances already polluting per se; processing certainly does not help oils become less dangerous. For this reason, according to the law, exhaust oils are collected by so-called mandatory consortia, to avoid disposal thereof in the ground and in the water-bearing stratum, where they would impair food safety.

[0005] To automotive lubricants industrial ones are added, so that the amounts of exhaust oil to be disposed of are definitely significant. Unfortunately, despite the setting up of mandatory consortia, recovered exhaust oils make up only about one third of the overall exhaust oils, the rest still getting lost in the environment, with ecological damage and, as will be seen in the following, economic damage, too.

[0006] From the 1960s, with the development of an ecological awareness, people have started to try and recycle exhaust oils, in order to obtain a product which could be somehow reused, in order to reduce the need for disposal.

[0007] The first processes were those with sulphuric acid and with liquid propane. That is, oils are processed adding sulphuric acid or propane, so as to remove a good deal of the impurities contained in exhaust oils. However, the process with acid has been virtually abandoned, due to the remarkable pollution problems that it implies.

[0008] As a matter of fact, the process with sulphuric acid causes the forming of acidic sludge, which retains inside non negligible amounts of oil and which furthermore contain polymer compounds and heavy metals; this sludge is hence difficult to be disposed of. Normally, such disposal occurs in a landfill, preferably after a neutralisation, which, however, increases the volume of the same sludge to be disposed of. For this reason the way has been attempted of sludge combustion, which, however, proved impracticable.

[0009] Other processes have thus been developed, starting from the one already mentioned, which makes use of propane.

[0010] The step of acidic processing is fully replaced by a clarification with liquid propane. Propane is chosen as hydrocarbon, because it is easily liquefiable and of low density once liquefied. It hence acts as thinner on the oils it is added to, so as to allow the separation of a high-density phase - which contains polymers with a high molecular weight and heavy metals - from a second fraction, consisting of clarified and dehydrated oils. Propane is hence removed and recycled upon mixing with incoming oils.

[0011] It is then proceeded to hot filtration, allowing the retrieval of a gaseous fraction. It is then finished off with decolouring and deodorisation of the contents.

[0012] This process, which allows to achieve higher yields, still has, however, some drawbacks. Firstly, handling propane - highly flammable - may be dangerous for the plant labour force. Moreover, part of the propane remains nevertheless trapped in the tarmac which forms as a by-product; this presence rules out the use of the bitumen obtained as by-product for the manufacturing of roads, with remarkable market limitation and resulting economic damage. Hence, the bituminous fraction in this process is simply a waste, to be disposed of and cannot be valued, as would instead be auspicable. Finally, the process is per se far more expensive than the process with sulphuric acid.

[0013] In more recent times, rerefinement processes of exhaust oils have been developed, using fractioned distillation processes and others. Some processes are aimed at obtaining a product to be burnt, so as to fully remove the waste, with energy recovery. Other processes have led to reusable products, after suitable processing, to obtain new lubricants. The Applicant, in particular, has been very active in this field, filing various patents for regeneration processes which have allowed to remarkably increase the useful product yields. Basically, these processes allow to obtain bases for lubricants - which make up the most valuable product -, bitumen and for the rest there are byproducts to be disposed of and combustion to obtain the heat needed to carry out the processes.

[0014] Bitumen is a relatively poor product, less expensive and hence less profitable with respect to lubricant bases. However, it has a certain market, especially for road building. With Italian patent no. 102015000018543 and with EP 3 098 291, the Applicant disclosed a method for enhancing the bitumen fraction produced together with the lubricant bases, to obtain a higher-quality product, which could be sold as master batch or as base for inks and the like. Thereby, even the bituminous fraction has become more appealing and the production thereof more profitable. In practice, in such document, the Applicant taught to recycle all the solid waste fractions, causing them to undergo a new grinding step, further separating a liquid phase, which made up a higher-quality bitumen and a solid one, to be sent back to the initial steps of regeneration.

[0015] Different patent documents, among which some by the same Applicant, detail the use of centrifuges for improving the separation of the lubricant portion to be retrieved 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 distillation step and a packed column distillation step. This centrifugation, together with vacuum obtained through a ring pump, pushes a great deal the removal of the solid particles contained in the exhaust oil, which arrives in the packed column already highly purified, so as to remarkably increase the retrieved fraction and to allow a longer useful life of the catalysts employed in this regeneration. However, in the centrifuge a solid residue remains - the particles mentioned earlier - which nowadays is disposed of. Hence, the residue of the centrifuge remains today in the fraction to be disposed of of the oils being regenerated and makes up a cost and a burden for the environment.

[0016] The problem at the basis of the invention is to propose a process for the recovery of exhaust oils which overcomes the mentioned drawbacks and which allows to push further the recovery of exhaust oil, enhancing a further portion of the waste (the residue in the centrifuge), nowadays to be disposed of, so as to further reduce the sludge and be economically more advantageous. This object is achieved through a process for the enhancement of the wastes of the regeneration of exhaust oils which provides a processing of the residue contained in at least one centrifugal separator, active in a regeneration process of exhaust oils, characterised in that said residue is caused to undergo a decanting step, to separate the solid from the liquid and in that said solid undergoes a drying step. According to a second aspect, the present invention refers to a plant for the regeneration of exhaust oils, comprising at least a centrifugal separator, a fractioned distillation column and a hydrorefining refinement unit, characterised in that, downstream of the exit of the waste of said centrifugal separator, it comprises at least a decanter and a dryer. According to a third aspect, the present invention refers to a bitumen, obtained as a fractioned distillation tail in a process for the regeneration of exhaust oils, characterised in that a solid residue is added thereto in a step of centrifugal separation, processed in a process as described in the first aspect of the present invention. The dependent claims describe preferential features of the invention.

[0017] Further features and advantages of the invention are in any case more evident from the following detailed description of a preferred embodiment, given purely as a non-limiting example and illustrated in the attached drawings, wherein:

fig. 1 represents a block diagram of a plant for the regeneration of exhaust oils, wherein the present invention can be implemented; and

fig. 2 represents a detail of fig. 1.

[0018] According to fig. 1, the exhaust oil to be regenerated - containing many impurities of a different type - enters from entry 1 and is supplied to a flash distillation column 2. Possibly, the oil to be regenerated may be enriched with a base, preferably a strong base, such as sodium hydroxide and/or, preferably, a potassium hydroxide, to remove acidic agents which pollute 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 there is the separation of an aqueous phase, comprising water, already present in the waste supplied into 1, water within which the strong base was dissolved and water formed from the reaction of the base with the spurious agents found in the oil, which comes out of column 2 as steam, containing light cleavage products of the oil from exit 3. From exit 4 the oil which must undergo the further regeneration processing comes out instead. The oil is thus supplied to a centrifugal separator 5, wherein the oil which must continue the regeneration thereof is separated from sediments, mostly solid in a slurry, consisting of carbonaceous agents which are harmful for the mechanisms to be lubricated. The centrifugal separator provides a turbine which has a rotation speed of 5,000-6,000 revolutions per minute. Following the separation in centrifugal separator 5, the part of oil to be regenerated comes out of pipe 6, while the solid material - the residue - is removed through pipe 7.

[0019] Pipe 6 supplies a heat exchanger 8 (for example, an oven), where the oil temperature is brought to a value suitable for the subsequent fractioned distillation, which occurs in column 9, whereto it is supplied by pipe 10. Such temperature lies above 300°C, preferably ranging between 300 and 400°C. The useful product fractions come out of column 9 through pipes 11-14 and are supplied to a hydrorefining reactor 15, wherefrom, after the hydrogenrefining treatment, at a temperature ranging between 280 and 360°C, at a pressure ranging between 50 and 120 bar, they come out in 16 as bases for lubricants, ready to be treated by the manufacturer together with fresh oil fractions, to be put back onto the market in the desired formulations.

[0020] The tail of column 9 comes out of pipe 17 and essentially consists of bitumen, to be reused for less noble uses, such as the road tarmac and roof weatherproofing.

[0021] Pipe 7 coming out of centrifugal separator 5 supplies the waste of separator 5 to a decanting and drying unit 18, wherefrom the processed solid comes out in 19, ready to mix with the bitumen supplied by pipe 17, coming from fractioned distillation column 9. Unlike what happens with the solid coming out directly as waste from centrifugal separators 5, it has been detected that the solid processed according to the present invention is perfectly mixable with bitumen and imparts to the latter useful properties, up until today not even imaginable, such as greater durability and less noise.

[0022] Fig. 2 shows more in detail the part of the processing of the solid residue, real core of the present invention.

[0023] Pipe 7 carries the material to be enhanced to a decanter 20, of a type known per se. The floating part of the contents of decanter 20, containing mostly water, is taken and sent through pipe 21 to the processing unit of wastewaters, to be treated in a known manner and discharged into the sewer. Thereby, most of the water is removed from the solid, which today makes these solids unmixable with bitumen. The bottom part, heavier and more viscous, is discharged by decanter 20 onto a conveyor belt 22. Drying devices 23 act 23 on conveyor belt 22. In substance, 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. Such drying devices 23 may be of various types. It can be proceeded by causing conveyor belt 22 to undergo the action of a vacuum or of hot air, a stripping step with steam, with air or nitrogen or another inert gas can be provided. Said drying step occurs at a temperature preferably ranging between 50°C and 300°C, preferably between 80 and 280°C, in a further preferred manner between 110 and 180°C, so as not to alter the composition of the solid, while effectively removing water therefrom. Said drying step occurs preferably at a pressure ranging between 10 and 450 torr, in an more preferred manner between 50 and 800 torr, in the most preferred manner between 200 and 450 torr, so as to further accelerate the removal of water as steam. As conveyor belt 22 brings forward the material coming from decanter 20 in the direction of arrow F, the material will lose water, gradually dehydrating. At the end of the travel of conveyor belt 22, the material, once dried, is discharged through pipe 19. As visible in fig. 1, it then joins back with pipe 17: the material contained in pipe 19, after undergoing the treatment just described, is capable of being perfectly mixed with the bitumen going out of pipe 17 - unlike what happened before - and is therefore joined back therewith and sent for sale as bitumen, a less fine fraction than that of lubricant bases, but nevertheless apt to be sold and which does not require a further treatment for the disposal thereof and, due to the treatment according to the present invention, finer than bitumen as is. In this way, a fraction so far to be rejected - with the entailing costs - of the material to be regenerated becomes now part of a sellable fraction, in addition to that, ennobled, so as to imply both an economic and an ecological benefit. Preferably, in the joining point between pipes 17 and 19 a mixer is provided to make the final product bitumen perfectly smooth. This procedure is clearly different from the one illustrated in EP 3 098 291. As a matter of fact, in that document it was provided that the solid residue of centrifugation would be ground, separated into solid fraction and into liquid fraction and that the liquid fraction would be used as bitumen. In this case, instead, it has been surprisingly found that, without proceeding to further grinding steps, which are expensive, but proceeding only to a standard decanting plus drying step, the solid may be used directly as bitumen, allowing to have a more marked material recovery compared to what occurred in the past, with a significant increase of the amount of sellable bitumen, what is more of excellent quality - as mentioned, of higher value than that of bitumen per se - and consequently with smaller energy consumption and with a smaller expenditure for waste disposal.

[0024] The bitumen which is obtained according to the present invention can rightly be called "ecological bitumen", since, as mentioned, it allows a marked reduction of the final waste, which would have to be disposed of with a non negligible environmental impact. However, it is understood that the invention must not be considered limited to the particular arrangement illustrated above, which makes up only an exemplifying embodiment thereof, but that different modifications are possible, all within the reach of a person skilled in the field, without departing from the scope of protection of the invention, as defined by the following claims.

[0025] In particular, the present invention extends to the case in which centrifugal separation occurs on multiple partialised flows. In this case, multiple centrifugal separators 5 are provided, operating in parallel. Similarly, decanting and drying unit 18 may comprise multiple decanters 20, operating in parallel.

LIST OF REFERENCE CHARACTERS

[0026] 

1

Entry

2

Flash distillation column

3

Exit (of 2)

4

Exit (of 3)

5

Centrifugal separator

6

Pipe

7

Pipe

8

Heat exchanger

9

Fractioned distillation column

10

Supply pipe (of 9)

11

Pipe

12

Pipe

13

Pipe

14

Pipe

15

Hudrorefining reactor

16

Exit (of 15)

17

Bitumen pipe

18

Decanting and drying unit

19

Bitumen pipe

20

Decanter (of 18)

21

Pipe

22

Conveyor belt

23

Drying devices (of 18)

Claims

1. Process for the enhancement of waste from the regeneration of exhaust oils which provides a treatment of the residue contained in at least one centrifugal separator (5), active in a process for the regeneration of exhaust oils, characterised in that said residue undergoes a decanting step, to separate the solid from the liquid, and in that said solid undergoes a drying step.

2. Process as in 1), characterised in that said centrifugal separator (5) provides a turbine which has a velocity ranging between 5,000 and 6,000 rpm.

3. Process as in 1) or in 2), characterised in that said drying step occurs at a temperature ranging between 50°C and 300°C.

4. Process as in 3), characterised in that said temperature ranges between 80°C and 280°C.

5. Process as in 3) or in 4), characterised in that said temperature preferably ranges between 110°C and 180°C.

6. Process as in any one of the preceding claims, characterised in that said drying step occurs at a pressure ranging between 10 and 450 torr.

7. Process as in 6), characterised in that pressure ranges between 50 and 800 torr.

8. Process as in 6) or in 7), characterised in that pressure ranges between 200 and 450 torr.

9. Plant for the regeneration of exhaust oils, comprising at least one centrifugal separator (5), a fractional distillation column (9) and a hydrorefining unit (15), characterised in that, downstream of the waste exit of said centrifugal separator (5), it comprises at least one decanter (20) and one dryer (22; 23).

10. Plant as in 9), characterised in that said dryer comprises a conveyor belt (22) and one or more drying devices (23) .

11. Plant as in 10), characterised in that said drying devices (23) cause the conveyor belt (22) to undergo the action of a vacuum, of hot air, of a steam air or nitrogen or other inert gas stripping.

12. Plant as in any one of claims 9) to 11), characterised in that multiple centrifugal separators (5) operating in parallel are provided.

13. Plant as in any one of claims from 9) to 12), characterised in that multiple decanters (20) operating in parallel are provided.

14. Bitumen, obtained as fractioned distillation tail in a process for the regeneration of exhaust oils, characterised in that a solid residue of a centrifugal separation step is added thereto, treated in a process as in any one of claims 1) to 8) .

Drawing