Process for the production of bio-oil lubricants

Abstract

A process for the regeneration of waste oils, comprising at least the following steps: pre-flash, fractional distillation and hydrofinishing is disclosed. According to the invention, such a process further includes a step of separation of bio-lubricants from the other lubricants. Preferably, a fraction of oils to be regenerated coming from the fractional distillation step is fed to a mixer (60) and therein is mixed with an organic polar solvent and in that the resulting mixture is decanted in a first decanter (64).

Description

[0001] This invention refers to a process for the regeneration of waste oils, particularly suitable for recovering oils coming from both a mineral and a biological source.

[0002] Lubricants have been very important products for centuries: they allow machinery to be performed avoiding gripping and overheating. Oils and fats normally lower the friction coefficient of two surfaces sliding with respect to each other. In this way, energy consumption for producing the relative motion is lowered, as well as the production of heat. A lower heat production avoids that the sliding surfaces partially melt on their surface facing the other sliding one, in this way preventing the at least partial soldering of the two surfaces which otherwise would grip. Lubricants also reduce the mechanical detachment of surface particles normally due to the friction, so reducing wear.

[0003] Anyway, reduction does not mean complete removal. Therefore, there is a friction, producing energy consumption, heat production and mechanical detachment of particles from the sliding surfaces. All of this leads to an impairment of the lubricants. Indeed, the relatively high temperature triggers some reactions within the lubricants, like cracking, cleavage, hydration, dehydration, dehydrogenation, oxidation and so on. The particles detached from the sliding surfaces pollute the lubricant, impairing its ability in reducing friction coefficients and such particles can even scratch the moving surfaces to which they are applied.

[0004] Therefore, after a certain duty cycle, lubricants should be removed and replaced with fresh ones.

[0005] Most lubricants are oil derivatives and waste oils are normally pollutants, which can pollute waters, soils and possibly even the atmosphere. Since the production and use of oils in mechanics is very massive, waste oils can become a major environmental problem and their disposal is surely among the most important problems in industry, nowadays.

[0006] Only 50-60 years ago, oils were simply wasted, with no particular measure. However, after it was realised that this was becoming an important ecologic problem, ways of disposal which were less impacting were studied. A first attempt was to burn the waste. However, this led to a poor recover of energy, while oil production should be kept rather high to meet the market needs. This led to some attempts to regenerate waste oils and get new bases for producing lubricants which would be regenerated but keeping high quality standards.

[0007] The Applicant has filed many patents referred to the regeneration of waste oils. The great result was that more than 60 wt.% of waste oils can be transformed into new bases. This allows to make economically advantageous to regenerate oils, to properly collect waste oils and to produce, together with regenerated oils, also high-quality bitumen, which can be used even for high added value products (like inks and similar).

[0008] A typical process for regenerating waste oils according to patents previously filed by the Applicant is shown in fig. 1.

[0009] According to the block scheme, waste oils are uploaded in 1 to a flash column 2, were wastewater and low boiling solvents are removed at a temperature of 140 °C and under a pressure of 53329-66661 Pa and vented in 3, while oils to be further treated leave the column 2 in pipe 4. The latter feeds a plate, fractional distillation column 5, wherein wastewaters and solvents are vented in 6, bitumen is downloaded in 7, from where it is stored in a tank 8. The distillation is carried out at 360-370 °C, under a head pressure of 266,65-399,67 Pa (2-3 torr) and a bottom pressure of 1333-2000 Pa (10-15 torr). Fractions 9 to 12 are recovered. Each fraction 9 to 12 undergoes a hydrofinishing treatment 13, with hydrogen coming from a steam reforming unit 14, through a pipe 15 at a temperature of 280-3560 °C, under a pressure of 10 7< -1.1×10 7< Pa. Bases for lubricants are collected in tanks 16 to 23 for marketing.

[0010] Although waste cooking oils are not harmful for the environment as the mineral ones, they anyway have very long decomposition times and tend to build up in soils and waters. Therefore, although the problem of their disposal is not so stringent as for waste oils derived from oil, it has anyway got an importance and it has been studied, in order to find solutions which can be implemented, in order to avoid their build up, especially in closed water bodies, like sewage, where such a build- up can result in failures and breakages. Among the possible uses of used cooking oils, their transformation into bio-lubricants and biofuels has become rather important in the last years. In spite of some practical problems, biolubricants are reaching a certain success and are often used where mineral oils were used in the past. Accordingly, waste biolubricants are often mixed with waste mineral oils. While mineral oils are mostly hydrocarbons exhibiting various extents of hydrogenation, bio-lubricants are normally carboxylic acids, alcohols, aldehydes and esters. Although processes like the one shown in fig. 1 can be useful also for regenerating biolubricants, the quality of the bases for lubricants which can be obtained is normally lower and biolubricants act as pollutants in the mixture of oils to be regenerated.

[0011] It is to be mentioned that bases for lubricants are normally divided into three categories, according to API: group I grade, having a sulfur content higher than 0.03 wt.%, a content in saturated hydrocarbons lower than 90 wt.% and a viscosity index ranging from 80 to 120; group II grade, having a sulfur content lower than 0.03 wt.%, a content in saturated hydrocarbons higher than 90 wt.% and a viscosity index ranging from 80 to 120; and group III grade, having a sulfur content lower than 0.03 wt.%, a content in saturated hydrocarbons higher than 90 wt.% and a viscosity index higher than 120. Group I grade is the lowest quality product, whereas group III grade is the highest quality product.

[0012] According to the present state of the art, group III grade lubricants can be produced through a waste oil regeneration process only under a pressure higher than 10 7< Pa (100 bar) and with small volumes of products and this is the reason why the production of bases of group I and group II grade is presently preferred, so as to save energy costs. Moreover, the production of group III grade bases for lubricants can produce only small volumes of products.

[0013] Therefore, on one hand, the production of group III grade lubricants from waste oils would be a good goal, on the other hand this has not been possible up to now without getting very high energy costs for little productions.

[0014] Among its activities, the Applicant has also developed processes aimed at recovering biolubricants from waste cooking oils, such processes having led to a few related patents.

[0015] The invention aims at proposing a process for the regeneration of waste oils, which overcomes the above problems, and which allows to get bases for lubricants belonging to the group III grade. This object is achieved through a process for the regeneration of waste oils, comprising at least the following steps: pre-flash, fractional distillation and hydrofinishing, characterised in that it further includes a step of separation of biolubricants from the other lubricants. Subclaims disclose preferred features of the invention.

[0016] According to an embodiment said step of separation of bio-lubricants from the other lubricants is carried out after the fractional distillation step and before the hydrofinishing step.

[0017] According to an embodiment, fractions which must undergo other purification and process steps are Vacuum Gas Oil, lubricant half-finished bases FLS, FLL and FLP. According to an embodiment, such fractions are processed one by one. Preferably, the stream to be processed is chosen through cut-off valves.

[0018] According to an embodiment, a fraction of oils to be regenerated coming from the fractional distillation step is fed to a mixer and is mixed therein with an organic polar solvent and the resulting mixture is decanted in a first decanter. The said organic polar solvent can be chosen among methanol, ethanol, propanol and 1-methyl-2-pyrrolidones. Preferably, the said organic polar solvent is methanol.

[0019] According to an embodiment, in the said first decanter the bottom layer is removed by a pipe and enters a mixer, where it is mixed with fresh water and washed and fed to a second decanter, where two layers separate: the bottom layer containing mostly wastewater, and the top layer, containing purified lubricant bases and undergoing a further hydrofinishing step.

[0020] According to an embodiment, the top layer in the first decanter is washed with water and sent to a third decanter, where two layers separate, the top layer being made up by bio-lubricants, bio-solvents and bio-fuels and the bottom layer being further processed. Preferably, the said bottom layer coming from the third decanter is fed to a packed column, from where two flows seeparate, one containing wastewater and the other containing the organinc polar solvent, which is partly recycled to the mixer, together with a solvent make up.

[0021] According to an embodiment, the hydrofinishing treatment is performed with the use of hydrogen coming from a steam reforming unit.

[0022] According to an embodiment, the hydrofinishing treatment is carried out with hydrogen coming from the regeneration of wastes.

[0023] According to an embodiment, the oils to be regenerated undergo a centrifugal separation before they are sent to a fractional distillation column. Preferably, solids separated through the centrifugal separation step are ground and the liquid coming from the grinding is recycled to the inlet to the process.

[0024] According to an embodiment, liquid sent to a decanter for a separation undergoes a centrifugal separation before entering the decanter.

[0025] According to an embodiment, liquid recovered from a decanter at any stage of the process undergoes a centrifugal separation step.

[0026] According to an embodiment invention, the unit for separating the biological fraction of waste biolubricants from mineral lubricants can be replaced through a separate plant for recovering biolubricants, biosolvents and / or biofuels.

[0027] According to an embodiment, the separation of the biological fractions takes place between the fractional distillation step and the hydrofinishing step.

[0028] Further features and advantages of the invention are more apparent from the following detailed description of a preferred embodiment of the invention, given purely as a non-limiting example and explained according to the annexed drawings, wherein: fig. 1 is a block diagram of a process for the regeneration of waste oils according to the prior art; fig. 2 is a block diagram of a process for the regeneration of waste oils according to this invention; and fig. 3 is a detail of fig. 2.

[0029] Figs. 2 and 3 disclose a preferred embodiment of this invention. Looking at fig. 2, the mixture of waste oils is fed through the pipe 24 to the pre-flash column 25. An outlet 26 vents part of the mixture, whereas the remainder is led by the pipe 27 to a plate distillation column 28.

[0030] A number of streams leave column 28. A stream 29 leads a product to a product reservoir 30. An outlet 31 vents wastes. And pipes 32, 33, 34 and 35 lead to respective reservoirs 36, 37, 38, 39.

[0031] Pipes 40, 41, 42 and 43 leave the respective reservoirs 36, 37, 38 and 39 and join in a feed 44, feeding an extractor 45. Two fractions leave the extractor 45: a pipe 46, which leads to a hydrofinishing step, summarised with the reference 47, which receives also hydrogen from a steam reforming unit 48 and leads to products 49, 50, 51, 52, 53, 54, 55, 56 and 57; and a pipe 58, leading to a unit 59 for the production of biolubricants, biosolvents and biofuels.

[0032] The extractor 45 is summarised in fig. 3. The feed 44 brings the oils to a mixer 60, where also a feed 61 ends. Feed 61 is fed with make-up reagents from the stream 62. After mixing, oils leave the mixer 60 from a pipe 63 and are fed to the extraction unit 64, where two layers separate. The lower layer leaves the extraction unit 64 through a pipe 65 and reaches a mixer 66, where the extracted fraction is washed with water coming from a pipe 67. The liquid mixture obtained in the mixer 66 is fed through a pipe 68 to an extraction unit 69. Two layers separate in the extraction unit 69, one being brought by the pipe 70 to a reservoir 71 and one being brought by a pipe 72 to a reservoir 73.

[0033] The upper layer leaves the extraction unit 64 through a pipe 74 and feeds a mixer 75, where another liquid is fed by a pipe 76. The liquid leaving the mixer 75 flows in a pipe 77 to a decanter 78, where two layers are separated. The upper layer is downloaded through an outlet 79, while another stream leaves the decanter 78 through a pipe 80, feeding a packed column 81.

[0034] Tails produced in the column 81 are downloaded through an outlet 82 and heads leave the column 81 through an outlet 83. This flow splits into a vent 84 and a recycle, feeding the feed 61.

[0035] Taking into account the above description of the general scheme, the process according to this invention is now described below.

[0036] Waste oils, collected by the mandatory consortia, are mixture of any kind of lubricants, including, inter alia, mineral oils and biolubricants. Such waste oils contain relatively high amounts of water, coming from the different steps of the collection process, polymers, formed through reactions like thermal cleavage, cracking and others, because of the high temperatures developed by the relative friction motion of the mechanical parts of machinery, and metal particles, mechanically detached from the metal parts of the machinery. All these matters are pollutants and impair the quality and performance of the oil, so that they should absolutely be removed from the oil during the regeneration, in order to get regenerated oils exhibiting a sufficiently good quality for the intended uses.

[0037] The first step is a flash distillation in column 25, taking place typically at a temperature of 110-160 °C, preferably at 140 °C, under a pressure of 53329-66661 Pa (400-500 torr), in order to remove as much water as possible from the oil under regeneration. The outlet 26 vents the water removed during the flash distillation; the stream venting from the outlet 26 contains wastewater and possible diluents.

[0038] The pipe 27 brings dehydrated waste oils to the plate distillation column 28. The dehydrated oil is fractionally distilled, normally at a temperature of 300-400 °C, preferably 350 to 370 °C, under a head pressure of 267-400 Pa (2-3 torr) and a bottom pressure of 1333-2000 Pa (10-15 torr), in order to separate oil fractions from one another.

[0039] The pipe 31 vents remainder wastewater and diluents and the outlet 29 brings bitumen to the reservoir 30, where it is stored for the subsequent sale, being a byproduct which has a certain added value. The fractions which must undergo other purification and process steps are Vacuum Gas Oil (pipe 32 and reservoir 36), lubricant half-finished bases FLS (pipe 33 and reservoir 37), FLL (pipe 34 and reservoir 38) and FLP (pipe 35 and reservoir 39). These fractions contain valuable bases for lubricants, suitable for most uses.

[0040] Products temporarily stored in reservoirs 36 to 39 should undergo further steps. Normally, they are processed one by one, so as to carry outr the process every time under homogeneous conditions. Products contained in reservoirs 36 to 39 can be feed through the respective pipes 40 to 43 to the pipe 44. This can be done by using cut off valves: one valve is put upstream of each pipe 40 to 43. One valve is open and the others are closed, so that only one fraction reaches the tube 44 and enters the extraction step 45, from which the tube 58 leads to the the unit 59 for the production of biolubricants, biosolvents and / or biofuel and the pipe 46 brings other lubricants to the hydrofinishing step 47, where the bases undergo a reaction with hydrogen, usually coming from a steam reforming unit 48, at a temperature ranging from 250 to 400 °C, preferably from 280 to 350 °C, under a pressure of 10 7< 1.1×10 7< Pa (100-110 bar), leading to the products aimed at.

[0041] According to an alternative embodiment of this invention, the unit 59 can be replaced through a separate plant for recovering biolubricants, biosolvents and / or biofuels. In this way, existing plants can suitably be employed, without the need to build new facilities, so getting cost and soil savings.

[0042] The products coming from the hydrofinishing step are, for example, hydrofinished Vacuum Gas Oil (49), lubricant bases of group I grade (80N 50, 100 N 51, 150 N52 and 400 N 53), lubricant bases of group II grade (HG-3N 54, HG-4N 55, HG-5N 56), and lubricant bases of group III grade 57. A product distribution as just depicted is possible only if the step 45 is provided, since pollutants are removed from the pipe 58 and the production of group III grade lubricant bases is by far less expensive than without such a step. The hydrofinishing step can be carried out at a hydrogen partial pressure lower than usually.

[0043] The step 45 is now disclosed in detail, with reference to fig. 3.

[0044] The fraction coming from the fractional distillation step through the pipe 44 is fed to the mixer 60. Another pipe 61 brings an organic polar solvent, which is made up by the pipe 62. Preferable solvents added from the pipe 62 are methanol, ethanol, propanol, 1-methyl-2-pyrrolidone and others, all of which can easily and selectively dissolve fatty acids making up the biological fraction of waste oils under regeneration. Methanol is particularly preferred, because of the costs and of its availability.

[0045] The mixer is stirred, so that the solvent mixes very well and thoroughly with the oils under regeneration. The tube 63 leads the mixture obtained in the mixer 60 to the decanter 64, where two phases separate, creating two layers. Practically, a fraction of oils to be regenerated coming from the fractional distillation step is fed to the mixer 60 and is therein mixed with an organic polar solvent and the -resulting mixture is decanted in the first decanter 64. This step can be aided with a centrifuge, which improves the separation into layers. The bottom layer contains mineral oils, and it is removed by a pipe 65 and enters the mixer 66, where it is mixed with fresh water and washed, so as to remove impurities from the mineral oil. The mixture leaves the mixer through the pipe 68 and reaches the decanter 69, where two layers separate: the bottom layer goes to the reservoir 71 through the pipe 70 and contains mostly wastewater. This step can be aided with a centrifuge, which improves the separation into layers. The top layer contains purified lubricant bases, and it is removed by the pipe 72 to the reservoir 73, from where it goes to the pipe 46 and is fed to the hydrofinishing step 47. The content of the reservoir 73 is so pure that the production of group III grade lubricant bases becomes feasible under economic conditions and with high throughput.

[0046] The top layer in the decanter 64 is removed by the pipe 74 and fed to the mixer 75, where it is mixed with water fed by the pipe 76 and it is washed. The mixture leaves the mixer 75 through the pipe 77 and reaches the third decanter 78, where two layers separate. The top layer -made up by bio-lubricants- is removed through the pipe 79 and is made up by bio-lubricants, bio-solvents and bio-fuels. The bottom layer is removed by the pipe 80 and it is fed to the packed column 81, from where two flows separate. The pipe 82 removes wastewater. On its turn, the pipe 83 removes the organic polar solvent which had been fed in 62. Part of it is vented through the pipe 84 and part is recycled to the pipe 61 and fed to the mixer 60, together with the solvent make up coming from the pipe 62, so as to take complete advantage of the ability of this polar solvent to dissolve fatty acids making up the biological fraction of the oils under regeneration. Practically, the top layer in the first decanter 64 is washed with water and sent to a third decanter 78, where two layers separate, the top layer being made up by bio-lubricants, bio-solvents and bio-fuels and the bottom layer being further processed.

[0047] The process is very effective in regenerating a mixture of oils, with the production of biological products, mineral lubricant bases (with a non-negligible amount of group III grade lubricants in high volumes (comparable to the ones of group I and group II grade), and bitumen. The position between the fractional distillation step and the hydrofinishing step of the regeneration of mineral oils of the unit 59 for the recovery of bio-lubricants in the operating chain surprisingly allows to achieve such a goal.

[0048] In the mineral fraction produced by the inventive process, sulfur is contained in an amount lower than usually; also, the aromatic carbon is less than usually and the viscosity index is higher than 120 even before hydrofinishing, which is not usual.

[0049] As an example, the effects of the inventive process are shown in the Table 1 below, with reference to the FLL fraction before the hydrofinishing step: ParameterMeasure unitsFLL treated according to this inventionUntreated FLL (prior art)Colour-6.507.50Kv 40 Mm 2< / s29.6028.5-31Viscosity index-123-124119,00PP°C-9-6,00CP°C-5-2,00Neutralisation numberMg KOH / g0.050.5-0.6SiliconPpm160.00190,00SulfurPpm1120.001700-1900VA flammability°C238.00218-228

[0050] It is understood that the invention should not be considered as limited to the particular arrangement above, which is only an exemplary embodiment thereof, but that several modifications are possible, all at reach of the skilled person, without departing from the scope of the invention itself, as depicted in the appended claims.REFERENCE NUMERALS

[0051] 1waste oil upload 2pre-flash column 3vent 4pipe 5fractional distillation column 6vent 7bitumen download 8tank 9distilled fraction 10distilled fraction 11distilled fraction 12distilled fraction 13hydrofinishing treatment 14steam reforming unit 15pipe 16tank 17tank 18tank 19tank 20tank 21tank 22tank 23tank 24pipe 25pre-flash column 26outlet 27pipe 28plate distillation column 29stream 30product reservoir 31outlet 32pipe 33pipe 34pipe 35pipe 36reservoir 37reservoir 38reservoir 39reservoir 40pipe 41pipe 42pipe 43pipe 44feed 45extraction step 46pipe 47hydrofinishing step 48steam reforming unit 49product 50product 51product 52product 53product 54product 55product 56product 57product 58pipe 59unit for the production of biolubricants 60mixer 61feed 62make up 63pipe 64extraction unit 65pipe 66mixer 67pipe 68pipe 69extraction unit 70pipe 71reservoir 72pipe 73reservoir 74pipe 75mixer 76pipe 77pipe 78decanter 79outlet 80pipe 81packed column 82outlet 83outlet 84vent

Claims

1. Process for the regeneration of waste oils, comprising at least the following steps: pre-flash, fractional distillation and hydrofinishing, characterised in that it further includes a step of separation of biolubricants from the other lubricants.

2. Process as claimed in claim 1), characterised in that said step of separation of bio-lubricants from the other lubricants is carried out after the fractional distillation step and before the hydrofinishing step.

3. Process for the regeneration of waste oils as claimed in claim 1) or 2), characterised in that fractions which must undergo other purification and process steps are Vacuum Gas Oil (pipe 32 and reservoir 36), lubricant half-finished bases FLS (pipe 33 and reservoir 37), FLL (pipe 34 and reservoir 38) and FLP (pipe 35 and reservoir 39).

4. Process for the regeneration of waste oils as claimed in claim 3), characterised in that such fractions are processed one by one.

5. Process for the regeneration of waste oils as in any previous claim, characterised in that a fraction of oils to be regenerated coming from the fractional distillation step is fed to a mixer (60) and therein is mixed with an organic polar solvent and in that the resulting mixture is decanted in a first decanter (64).

6. Process for the regeneration of waste oils as claimed in claim 5), characterised in that the said organic polar solvent is chosen among methanol, ethanol, propanol and 1-methyl-2-pyrrolidones.

7. Process for the regeneration of waste oils as claimed in claim 6), characterised in that the said organic polar solvent is methanol.

8. Process for the regeneration of waste oils as in any claim 5) to 7), characterised in that in the said first decanter (64) the bottom layer is removed by a pipe (65) and enters a mixer (66), where it is mixed with fresh water and washed and fed to a second decanter (69), where two layers separate: the bottom layer containing mostly wastewater and the top layer, containing purified lubricant bases and undergoing a further hydrofinishing step (47).

9. Process for the regeneration of waste oils as claimed in any claim 5) to 8), characterised in that the top layer in the first decanter (64) is washed with water and sent to a third decanter (78), where two layers separate, the top layer being made up by bio-lubricants, bio-solvents and bio-fuels and the bottom layer being further processed.

10. Process for the regeneration of waste oils as claimed in claim 9), characterised in that the said bottom layer coming from the third decanter (78) is fed to a packed column (81), from where two flows separate, one (82) containing wastewater and the other (83) containing the organic polar solvent which is partly recycled to the mixer (60), together with a solvent make up.

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