DESCRIPTION

The present invention relates to a process for the recovery of a complex of wastes , in particular an integrated recovery process for waste oils and non-recyclable plastic wastes .

A vast maj ority of human activity ( in truth, animal activity in general ) leads to the production of waste . Nature ' s design is such that waste of one species forms nutriment for another, and therefore species can all survive without being overrun and overwhelmed by waste . For example, animal excrement is an optimal fertiliser for plant s , allowing nutrient s to be introduced to them, such as nitrogen, which they would not be capable of obtaining otherwise . Some human activities however lead to waste products which no longer return to the natural cycle . With the industrial revolutions and production of the last few centuries , the production of waste has increased considerably . Thus , waste which normally was disposed of in the natural cycle has increased to the point that the natural cycle no longer manages to dispose of it , while , alongside this , there is waste which the natural cycle is incapable of disposing of due to it s particular chemical nature, such as for example plastic materials .

The consequence of this is that waste today is an enormous problem, involving pollution, contamination, formation of dangerous liquids and gases , and so on .

Ecological awareness started to spread in the 1960 s , originally due to the early negative ef fect s of pollution, gradually resulting in an ever increasing number of people being concerned about the impact of waste discharge on the environment . This first led to scientists raising the alarm, then to protest s by ecological activist s , then to waste regulation laws and, lastly, to new research by industry aimed at finding solutions for reducing pollution and contamination, while however maintaining a satis factory financial profit for producers . The latter stage led to the creation of the "circular economy", a model of production and consumption which involves sharing, borrowing, reusing, repairing, reconditioning and recycling of existing products and materials for as long as pos sible, so as to extend the life cycle of product s , contributing to minimise waste . Once a product has become unusable, the materials from which it is made are , where pos sible, reintroduced into the economic cycle after appropriate trans formations . Hence they can continually be reused within the productive cycle generating further value .

Waste product s come in many different types and are each treated, during disposal, in the appropriate way for them . For example , there is household waste , currently separated out according to collections dif ferentiated as organic waste ( also referred to as "wet waste" ) , paper and cardboard, plastic, metals , glass and dry or undif ferentiated residual waste . Organic waste is generally composted to produce humus and compost , paper is soaked, re-bleached and dried, plastic is ground, separated, melted and mixed in normally small percentages with other fresh plastic, metals are purified, each according to it s own chemico-physical characteristics , glas s is melted and remoulded, and the undif ferentiated waste is generally dumped or burned, preferably in a waste-to-energy plant , where the energy produced can be used to generate electricity or to supply district heating . There is special hospital waste which must be treated according to its nature , but under conditions preventing the spread of germs and bacteria found therein . There is gaseous waste, such as ef fluent s of certain chemical and/or petrochemical processes , which are to be filtered and possibly purified before being introduced into the atmosphere . Many other examples of dif ferent kinds of waste can be given .

In some cases , the waste has not been enhanced or used as raw material for the creation of other product s . Waste oils certainly feature among such waste . After decades of direct disposal and non-regulation, without any type of treatment , various treatment s have begun to be set up, aimed at preventing the introduction of the waste and its derivatives into the ground, into the groundwater layers and into the atmosphere . A large part of the proces ses for recovering waste oils implemented, for example , by one of the Applicants ( Itelyum Regeneration) of the present application trans form the oil waste into bases for new lubricants and bitumen, with little waste , preventing vast quantities of the continuously produced waste from possibly contaminating the ground and strata . Being highly polluting waste, this type of proces s provides for significantly improving the quality of the ground, strata and even the air . Furthermore , the consumption of more oil is avoided, slowing down the depletion of this precious resource .

An example of this is given in EP 3 683 295 , in which there is described a proces s for the enhancement of waste oils which provides a proces sing of the residue contained in at least one centrifuge, active in said proces s , in which said residue undergoes a decanting step, to separate the solid from the liquid; the solid is later dried .

Another example is given by EP 3 098 291 , in which there is described a proces s for regenerating waste oils , comprising a step of flash distillation of said oil to be regenerated, a step of decanting of the heavy fraction into a packed column, so as to send an oil fraction to hydrorefining, recovering bitumen as a by-product . The bitumen fraction is ground; the liquid fraction obtained after the grinding is separated and used as bitumen, while the solid fraction is separated and recycled at the step of decanting of the heavy fraction .

Another type of waste is that of plastic materials . Some of these are recyclable, to a greater or lesser extent ( as has already been seen, always mixed with a fresh load) , but there are non-recyclable ones , such as thermosetting materials and vulcanised materials . These materials are generally known as "Plasmix" , i . e . a mixture of various materials . An example of Plasmix is : 57% by weight of plastic, 10% by weight of paper and cardboard, 3% by weight of wood, 3% by weight of textiles , 27 % by weight of inert materials that are unsuitable for recycling such as PVC and ABS . It is desirable to succeed in recovering even this waste .

Another example of waste that is dif ficult to dispose of is used tyres , known by the jargon "ELTs" ( end-of-life tyres ) , which are vulcanised and the combustion of which leads to a high content of highly polluting gases . Until now, attempt s made to recover ELTs have led to extremely polluting substances , shifting the problem rather than solving it .

WO2016/112 371 relates to a process and a system for pyrolysing rubber taken from tyres to form fuels such as , for example , naphtha, kerosene , diesel and fuel oil . Provision can also be made for the formation of other product s , such as carbon black, powder activated carbon, sulphur and non-condensable gases .

Proces ses for regenerating waste oils have been seen above . These oils are mostly very pure hydrocarbon substances which are used for long periods in machines and engines , where they reduce the friction, which it self is very strong, degrading in a manner that is not always predictable and collecting from the engines debris of various kinds , especially polymeric and metallic debris , sometimes becoming contaminated even by water . There is no evidence that tyre pyrolysis processes lead to oily substances similar to waste oils , given that the origin is from substances containing carbon and other atoms , such as sulphur and nitrogen, which at high temperatures are broken down in a substantially non-selective manner . Therefore, a person skilled in the art cannot anticipate any similarity between pyrolysis oil and used lubricants .

The problem underlying the invention is to propose an environmental recovery process which overcomes the drawbacks mentioned and which provides for eliminating plastic and rubber based waste, recycling it in a manner that is completely safe for the environment and reusable in an economically viable way . This aim is achieved through a proces s for the recovery of a complex of wastes , comprising waste oils and non-recyclable plastic materials , among which vulcanised plastic materials , fed separately, characterised in that it provides at least a fractional distillation step of the waste oils as well as a devulcanisation step and a depolymerisation step of the non- recyclable plastic materials with oil production, the mixing of the products of the fractional distillation of the waste oils and of the depolymerisation of the non-recyclable plastic materials , and the subsequent hydrorefining of the mixture obtained . Based on a second aspect , the aim is achieved with a plant for the recovery of a complex of wastes , characterised in that it comprises a steam reforming area, a hydrorefining reactor, a fractional distillation column, and a "Plastbreaker" unit . Said "Plastbreaker" is a proces s which exploits mild thermal treatments to trans form the mixture of plastic wastes (end-of-life wastes ) into lubricant s and hydrogen by means of hydrorefining . This process has a significantly lower CO2 production impact as compared with other proces ses for gasifying wastes , by virtue of the mild conditions . This process can be sustained by solar radiation concentration technologies . Preferably, the plant furthermore comprises a flash distillation column and/or a centrifuge . The dependent claims describe preferred characteristics of the invention .

Further features and advantages of the invention will become clearer from the following detailed description of a preferred embodiment , given purely by way of example and in a non-limiting manner, and illustrated in the appended drawings in which :

Figure 1 is a block diagram, providing an overview, summarising the main components of a plant suitable for running the process according to the present invention;

Figure 2 is a block diagram of a first main component of the diagram of Figure 1 ;

Figure 3 is a block diagram of a second main component of the diagram of Figure 1 ;

Figure 4 is a block diagram of a third main component of the diagram of Figure 1 ; and

Figure 5 is a block diagram of the whole process according to the present invention .

The present invention is based on the surprising discovery of the fact that the material which is obtained from devulcanising and depolymerising tyres and plastic waste, an oily material, can be mixed with the used lubricant s to be regenerated . The proces s according to the present invention can be divided into three main areas , corresponding to the categories of component s of the plant in which it can be carried out . In particular, according to that shown in Figure 1 , there is a steam reforming area 1 which feeds , via a duct 2 , a hydrorefining reactor 3 . A flow 4 of H2S and a flow 5 of product , formed by bases for lubricants , exit the reactor 3 . The hydrorefining reactor 3 is also fed by a flow 6 from a fractional distillation column 7 , as well as by the flow 8 from a "Plastbreaker" unit 9 .

To clarify, the following arrive at the hydrorefining reactor 3 : hydrogen by the ducts 2 , fractions ( divided into fractions 6A, 6B, 6C, 6D and pos sibly others ) of bases for lubricating oils to be refined, by the duct 6 , and oils to be refined, from the treatment of plastic materials , by the duct 8 .

The components just described in an extremely simplified and general manner will now be described in greater detail hereinafter, in con junction with Figures 2 to 4 .

In Figure 2 , "1" represents a steam reforming unit , the feed 10 of which is formed by biomethane (methane obtained from agricultural and agro-industrial biomass and from the organic fraction of municipal waste ("wet waste" ) , so as not to require extraction activities and to dispose of any waste ) and water . In addition to the hydrogen which exit s by the duct 2 , CO2 is produced which is discharged by the duct 11 . In a particularly integrated plant and one which minimises wastes , the CO2 which is discharged by the duct 11 is fed to an amine capture unit , in other part s of the plant or in another plant , located nearby . Thus , the CO2 which is produced is sequestered and not emitted into the atmosphere ; therefore the process does not have an impact on the greenhouse ef fect , which is highly felt today . Moving on to Figure 3, there is represented waste oils being fed to the plant via the duct 12. There is a flash distillation column 13, a duct 14 which feeds a centrifuge 15, following which is a duct 16 which feeds the column 7. From the flash distillation column 13, there is a waste outlet 17 which transports mostly aqueous substances (often with surfactant content or waste material similar to soap) , while a duct 18 discharges bitumen from the fractional distillation column 7.

Lastly, examining Figure 4, vulcanised plastic is fed to this part of the plant by the duct 19 to a shredder 20. There are three outlets from the shredder 20. The outlet 21 discharges rubber powder, the outlet 22 discharges inorganic residues, while the outlet 23 feeds a melting reactor 24. A duct 25 exits the reactor 24 and feeds a reactor 26, suitable for devulcanising the vulcanised material. A duct 27 exits the reactor 26 and feeds the "Plastbreaker" unit 9. In addition to the duct 8, a duct 28 exits the unit 9. A second duct 29 exits the reactor 26 and feeds a second devulcanisation waste treatment reactor 30, from which sulphur exits, as a by-product, via the duct 31. Thus, harmful emissions of H2S or SO2 are prevented .

Referring now to the whole-view diagram of Figure 5, the process according to the present invention will be illustrated in its entirety.

Biomethane is introduced into the plant, into the reactor 1, by the duct 10. Water, in the form of vapour, is added to the same reactor. In the reactor 1, in a known way, the following reaction takes place:

CH ₄ + 2H ₂ O - > CO ₂ + 4H ₂ (1)

The CO2 is discharged by the duct 11, while the hydrogen produced by the "steam reforming" of the biomethane goes, via the duct 2, to the reactor 3, where it is used for the subsequent hydrorefining of lubricant bases, as will be seen later .

Waste oils, from municipal consortia or from other waste sources, are fed via the duct 12 to a flash distillation column 13 , where the waste oil undergoes a step of flash distillation, in order to remove aqueous substances . Therein, the oil to be regenerated is brought to a temperature higher than 100 °C, in order to eliminate, via the duct 17 , the aqueous substances which reduce the properties of the oil . The product which is not removed through distillation exits the column 13 via the duct 16 and is fed to a fractional distillation column 7 , if necessary after other purification steps , such as the centrifugation step 15 ( represented in Figure 3 ) and if necessary other steps , such as packed column absorption, decanting, removal of silica and others , not indispensable per se for the implementation of the regeneration proces s but which provide for simultaneously obtaining higher yields and qualities , often at lower energy costs .

Generally, the fractional distillation column 7 is a plate column, from which various fractions exit (more flows 6A-6D are represented in Figure 3 ) , each of dif ferent weight , while the heavy residue, made up of bitumen, exit s by the duct 18 and is fed to a mixer 32 . The fractions , indicated collectively in Figure 5 by the reference 6 , are fed to the hydrorefining reactor 3 , where it has just been seen that hydrogen enters by the duct 5 for the next operation .

Vulcanised plastic waste items are fed to the plant by the duct 19; it is referred to as a duct 19, but given that the waste items are solid substances , this term can be understood to mean various apparatus , even quite different from a duct , such as a hopper, a conveyor belt , a feed screw or other device . The vulcanised plastic waste items are fed into a shredder 20 of known type by the duct 19 . The shredder may for example be a ball mill, a triturator or other device , suitable for reducing the waste materials fed by the duct 19 into tiny pieces or even into powder, so as to facilitate chemical and thermal exchanges , given that the specific surface area of the plastic material is increased . The shredder 20 has an outlet duct 22 from which inorganic residues exit , separated from the rest by using the dif ference in weight or with the aid of eddy current devices or other means , so as to expel from the load substances which would not be able to regenerate , such as metallic materials , sand, pebbles and similar, which are thus expelled from the plant and disposed of in a more appropriate manner, usually as inert substances , even for the production of concrete or similar .

The shredder 20 has a second outlet 21 by which rubber powder exits and is fed to the mixer 32 where, as was illustrated previously, the bitumen has already arrived, exiting the fractional distillation column 7 . Thus the rubber powder which is discharged after the shredding step is mixed with the bitumen obtained from the fractional distillation of the waste oils , to give a mixture of bitumen and rubber, exiting by the duct 40 , called rubber-powder-modified bitumen and which exhibit s high performance in the production of road stretches , with a net reduction of noise from vehicles driving along them . This product also provides for preventing the introduction of polluting substances into the environment .

Lastly, the shredder 20 has a third outlet 23 , from which the shredded fraction exits for the next steps of the operation .

The duct 23 feeds a melting unit 24 with the shredded material, where the plastic material is brought to a temperature so as to completely melt the plastic . Preferably, the melting takes place in the absence of air, to prevent combustion or in any case degradation of the plastic material . The melted material exits by the duct 25 and enters a devulcanisation reactor 26 . The vulcanised plastic material is fed to the devulcanisation step after having been shredded and melted . Therein, in a manner that is known per se , reactions take place breaking the bonds between the vulcanised materials and sulphur . Based on a preferred embodiment , the devulcanisation in the reactor 26 takes place according to the process developed by one of the Applicants (the Politecnico di Milano ) and known by the process name SACS . In this proces s , H2S is split into hydrogen (blue ) and elementary sulphur, according to the following reaction : 2H ₂ S - > 2H ₂ + S ₂ by means of catalysis and under mild operating conditions . The cleavage is thermally sustained inside a furnace which can be a new, completely dedicated, unit , or a previous , preferably electrical, unit adapted for the purpose .

A fraction containing sulphur exits via the duct 29 and is conveyed to the completion of the treatment in the reactor 30 ; at the end of this treatment , the sulphur is discharged via the duct 31 . The fraction which no longer contains sulphur is transported by the duct 27 to the reactor 9 , where the product s of devulcanisation are trans formed into lubricants to be refined and hydrogen . In particular, the hydrogen exits the reactor 9 via the duct 28 , is fed to a pressure swing absorption unit , by which the hydrogen is purified and sent , via the duct 34 , to the hydrorefining reactor 3 , where it is added to the hydrogen from the steam reforming of the biomethane . The oil obtained from the trans formation of vulcanised plastic waste items exits on the other hand by the duct 8 and is fed to the same reactor 3 , where it is mixed with the oil from the regeneration of waste oils .

In the reactor 3 , produced as a packed catalytic reactor, the various fractions , divided up according to their molecular weight , are treated with hydrogen and transformed into bases for lubricant s , which are discharged from the plant via the duct 5 , to be sold to lubricant manufacturers to complete the operation according to the particular requirements to be met . And this is the highest-value product of the process according to the present invention .

It is appropriate to note that the lubricant base fraction which exit s by the duct 5 is clean and does not contain rubber powder nor plastic nor other substances . This result is completely surprising with regard to that which has taken place until now, since the oils until today obtained from the regeneration of vulcanised plastic waste items contained considerable quantities of powder making the use of this oil dangerous in many respects , both technical and environmental . The key change that has enabled a cleaner product to be obtained is the mixing with the fraction from the regeneration of waste oils and the hydrorefining step, which process steps until today have never been put into practice by the industry of the sector .

As regards the proces s which takes place in the reactor 9 , according to a preferred embodiment , this is a process known as "Plastbreaker" . The proces s involves oxidising the materials with air or oxygen and nitrogen, at a temperature that varies between 25 °C and 500 ° C . Plastic materials are pyrolysed, thus reducing them to shorter chain hydrocarbon substances , after an actual depolymerisation, with a gasification stage, hence leading to the bases for lubricants .

From the reactor 3 , there is also an outlet for by-product via the duct 4 . This is conveyed to an H ₂ S separator 35 . A duct 36 carries the H ₂ S to a reactor 37 where, according to the process known as "AG2S", the mixing of H ₂ S with CO ₂ takes place, which leads to the formation of syngas , according to the following reaction : 2H ₂ S + CO ₂ - > CO + H ₂ + S ₂ + H ₂ O ( 2 )

A duct 38 carries the hydrogen obtained from this proces s back to the hydrorefining reactor 3 , where it is combined with the other two sources of hydrogen - steam reforming of biomethane and depolymerisation of plastics - as raw material to carry out the refining . Another duct 39 on the other hand discharges the sulphur which is combined with that discharged in 31 , for its subsequent uses .

In practice, the process according to present invention allows three types of waste to be loaded (biomethane in 10 , waste oils in 12 and non-recyclable plastic materials in 19 ) and, after treatment , bases for lubricant s to be obtained as the main product , in 5 , of high added value , and a lower added value product but with rather high performance in any case, namely rubber-powder-modified bitumen which exit s by the duct 40 , and sulphur, in 31 and 39 , which has a certain market value in the sulphuric acid industry . The hydrogen which is produced and used in the proces s is to be considered to be at least blue, given that the CO ₂ produced is used in the capture of amines and is therefore not discharged into the atmosphere . The proces s according to the present invention does not create waste in significant quantities and which does not have a subsequent and saleable use, thereby completely closing the cycle . For this reason, it proves to be extremely advantageous , both from an environmental and economical point of view, integrating fully and in a significant manner in the "circular economy" . Furthermore , if managed correctly, the proces s according to the present invention could sustain itself alone, using hydrogen as energy vector, reducing or even eliminating the consumption of methane in the furnaces , with clear ecological and economic advantages as well as that of the conservation of raw materials .

It is understood that the invention must not be considered to be limited to the particular arrangement illustrated above, which forms only one example embodiment thereof , but that various variants are possible , all within the capabilities of a technician skilled in the art , without thereby departing from the scope of protection of said invention, which scope is defined in the claims that follow . LIST OF REFERENCE CHARACTERS

1 Steam reforming plant

2 Duct

3 Hydrorefining reactor

4 Flow of H2S

5 Flow of bases for lubricant s

6 Duct

7 Fractional distillation column

8 Duct

9 "Plastbreaker" plant

10 Feed ( for 1 )

11 Duct

12 Duct

13 Flash distillation column

14 Duct

15 Centrifuge

16 Duct Discharge (from 13)

Discharge (from 7)

Duct

Shredder

Outlet (of 20)

Outlet (of 20)

Outlet (of 20)

Melting reactor

Duct

Devulcanisation reactor

Duct

Duct

Duct

Devulcanisation waste treatment reactor

Duct

Mixer