GB2521133A

GB2521133A - Method for desulfurization and aromatic compound removal of re-refined base oil that is recovered from waste lubricating oil

Info

Publication number: GB2521133A
Application number: GB1321775.7A
Authority: GB
Inventors: Wei-Ming Chang; Cheng-Yin Chang
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-12-10
Filing date: 2013-12-10
Publication date: 2015-06-17
Also published as: GB201321775D0

Abstract

A method for desulfurization and aromatic compounds removal of a re-refined base oil being recovered from waste lubricating oil with the use of NMP (N-Methyl Pyrrolidinone) as an extracting agent, including a re-refined base oil extraction process for mixing re-refined base oil with NMP (N-Methyl Pyrrolidinone) and performing the extraction process of desulfurization and aromatics removal, a high speed centrifuge separation process using a high speed disc separator to separate sulfide and aromatics from the produced fluid mixture so as to obtain a mixture of re-refined base oil and extracts, a re-refined base oil recovery process for performing a core operation of short path distillation, and a utility facility process using a cooling tower and a chiller to generate and circulate a chilled water for circulating through the re-refined base oil recovery process short path evaporator and an external cold well for condensing the produced re-refined base oil.

Description

METHOD FOR DESULFURIZATION AND AROMATIC

COMPOUND REMOVAL OF RE-REFINED BASE OIL THAT IS

RECOVERED FROM WASTE LUBRICATING OIL

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to re-refined base oil extraction technology, and more particularly to a method for desulfurization and aromatic compounds removal of re-refined base oil that is recovered from waste lubricating oil. The invention also employs a short path distillation technique for recycling NMP.

2. Description of the Related Art:

Because crude oil prices have been rising continuously, the prices of base oil for the preparation of lubricating oil also keep rising.

At the present time, the mostly known method of recovering base oil from lubricating oil is to distill re-refined base oil from waste lubricating oil with vacuum distillation or thin-film evaporation, and then to purify the distilled re-refined base oil using acid white clay as an adsorption filter media so as to obtain sellable base oil. However, most waste lubricating oil comes from vehicle lubricating oil or the so-called engine oil.

During operation of the engine, the fuel oil that is injected into the cylinder and not burned out will eventually penetrate into the lubricating oil. causing the base oil in the lubricating oil to be contaminated by the aromatics and sulfide in the fuel oil. These aromatics and sulfide will be introduced into the base oil and cannot be easily removed by a simple filtration or adsorption method. The re-refined base oil obtained using the conventional acid white clay based base oil recovery method has the disadvantages of deep c&or, pungent smell, low flash point and low viscosity index.

Further, using acid white day w recover re-refined base oH will produce a large amount of waste acid soil. This waste acid soil can cause a severe environment& profflem if it is not proper treated.

Except the method of using acid white day to recover re-refined base oil, large waste lubricating oil processing companies of capaciiy over 10M3/h usually will employ a distillation process under a low pressure or a film evaporation process to distill or evaporate re-refined base oil from waste lubricating oil, and then a follow-up hydro-treating process to cut off longer carbon bonds of the distilled re-refined base oil using a high pressure hydrogen cracking energy, thereby obtaining light color (typically <1.0) good-looking re-refined base oil. lloweyer, the hydro-treating process is dangerous because leakage of hydrogen can cause an explosion hazard.

In general, conventional re-refined base oil recovery

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methods can be classified into two types, namely, (1) acid white clay filtration recovery method and (2) hydro-treating recovery method. The former is less effective and can cause a secondary pollution, and therefore, it will be gradually phased out. The hydro-treating recovery method has the disadvantages of high equipment investment cost. Further, due to security concerns, it is difficult to get an operating license from the local government for the application of the hydro-treating recovery method. Therefore, there is a strong demand for a simple re-refined base oil recovery method that is easy to perform and can eliminate the drawbacks of conventional methods.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a method for desulfurizing re-refined base oil and removing aromatic compounds from re-refined base oil that is recovered from waste lubricating oil without using any white acid clay as commonly applied in the conventional waste lubricating oil recover techniques, lowering the chroma of the re-refined base oil and increasing the flash point and viscosity index of the re-refined base oil so as to improve the quality of the re-refined base oil.

It is another object of the present invention to provide a method for desulfurizing re-refined base oil and removing aromatic compounds from re-refined base oil that is recovered from waste lubricating oil, which enables the re-refined base oil refining process to be performed under a high vacuum (low pressure) and low temperature working environment, preventing a secondary pollution, assuring a high level of safety, saving energy consumption and reducing the processing cost.

To achieve these and other objects of the present invention, method for desulfurizing re-refined base oil and removing aromatic compounds from re-refined base oH that is recovered from waste lubricating oil in accordance with the present invention uses NMP (N-Methyl Pyrroildinone) as an extracting agent, comprising a re-refined base oil extraction process, a high speed centrifuge separation process for re-refined base oil, a re-refined base oil recovery process and a utility facility process. The re-refined base oil extraction process is to mix refined base oil with NMP (N-Methyl Pyrrolidinone) and to perform the extraction process of desulfurization and aromatics removal. The high speed centrifuge separation process uses a high speed disc separator to separate sulfide and aromatics from the produced fluid mixture so as to obtain a mixture of re-refined base oil and extracts.

The re-refined base oil recovery process is to perform a core operation of short path distillation. The utility facility process uses a cooling tower and a chiller to generate and circulate a chilled water for circulating through the re-refined base oH recovery process

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short path evaporator and an external cold well for condensing the produced re-refined base oil.

It is still another object of the present invention to provide a method for desulfurizing re-refined base oil and removing aromatic compounds from re-refined base oil that is recovered from waste lubricating oil, which is capable of recovering NMP (N-Methyl Pyrrolidinone).

To achieve this object, the method of the invention further comprises a NMP recovery process to run short path distiflation for recovering NMP (N-Methyl Pyrrolidinone) under a low temperature and ow pressure working environment.

Thus, the invention has the advantages and features as follows: The invention provides an improved method for desulfurizing re-refined base oil and removing aromatic compounds from re-refined base oil. This improved method is more safety and more efficient than conventional techniques. and can greatly reduce virgin base oil loss and energy consumption and the processing cost and obtain high quality re-refined base oil. As the method of the invention eliminates the use of acid white clay as an adsorption filler media, the method of the invention prevents generation of environmentally harmful waste acid soil.

The method of the invention not only can achieve deep desulfurization and removal of aromatics but also lower the chroma of the re-refined base oil and increase the flash point and viscosity index of the re-refined base oil without producing any environmentally harmful waste products. When compared to the conventional method that uses acid white clay as an adsorption filter media, the invention does not produce any environmentally harmfu' waste products. Therefore, the method of the invention is environmentally friendly.

Further, as the short path distiflation process of the present invention is performed under a high vacuum (low pressure) and low temperature working environment, assuring a high Ieve of operationa' safety and reducing the consumption of energy. The NMP recovery process is also performed under the same low pressure and low temperature working environment, meeting the demands of energy-saving and environmental protection. In general, the method of the invention, when compared to conventional technique of using acid white clay as an adsorption filter media has the advantages of low energy consumption, low operating cost and secondary pollution prevention.

Other advantages and features of the present invention will he fufly understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference signs denote Uke components of structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system block diagram used for the application of a method for desulfurization and aromatic compounds removal of re-refined base oil been recovered from waste lubricating oil in accordance with the present invention.

FIG. 2 is a schematic drawing illustrating the equipment arrangement of the re-refined base oH extraction process and the high speed centrifuge separation process for re-refined base oil in accordance with the present invention.

FIG. 3 is a schematic drawing illustrating the equipment arrangement of the re-refined base oil recovery process in accordance with the present invention.

FIG. 4 is a schematic drawing illustrating the equipment arrangement of the utility facility process in accordance with the present invention.

FIG. 5 is a schematic drawing illustrating the equipment arrangement of the NMP recovery process in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1-5, the invention provides a method for desulfurizing re-refined hase ofl and removing aromatic compounds from re-refined base oil that is recovered from waste lubricating oil.

This method indudes the steps of: re-refined base oil extraction process 10, high speed centrifuge separation process for re-refined base oil 20, re-refined base oil recovery process 30, and utility facility process 40.

The re-refined base oil extraction process 10 is to mix the re-refined base oil with NMP (N-Methyl Pyrrolidinone) so as to perform the extraction process of desulfurization and aromatics removal.

Performing the re-refined base oil extraction process 10 needs the equipments of one re-refined base oil reconcile heating tank 11, a plurality of material delivery pumps 12/13, one NMP storage tank with built-in heater 14, one centrifugal extractor 15, one re-refined base oil and extract buffer tank 16, and one NMP and extract buffer tank 17.

When starting the re-refined base oil extraction process 10, heat the re-refined base oil reconcile heating tank 11 to 70°C and keep it at this temperature level when the prepared re-refined base oil is being continuously supplied, and heat the NMP storage tank 14 to 50°C and keep it at this temperature level when the prepared NMP is being continuously supplied. When the temperature of the re-refined base oil reconcile heating tank 11 and the temperature of the NMP storage tank 14 reached the respective predetermined values, start the material delivery pumps 12 and 13 synchronously. At this time, the material delivery pumps 12 and 13 synchronously and respectively pump the prepared re-refined base oil and NMP at a predetermined feed ratio to the centrifugal extractor 15 for desulfurization and aromatic compound removal. After extraction through the centrifugal extractor 15, the extracted re-refined base oil and related

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extract are delivered to the re-refined base oil and extract buffer tank 16, and the extracted NMP and related extract (fluid mixture containing sulfides and aromatic hydrocarbons) are delivered to the NMP and extract buffer tank 17.

The predetermined feed ration between the re-refined base oil and the NMP is determined subject to the characteristics and amount of aromatic compound content of the re-refined base oiL Based on the actual operational verification, the feed ratio between the re-refined base oil and the NMP is preferably within the range of 2: I 1:2.5, i.e., one liter of re-refined base oil with O.52.5 liters of NMP. The ratio of the NMP is adjustable from 0.5 liter to 2.5 liters subject to the concentration of aromatic compounds and sulfides in the re-refined base oil. However, the feed can also be slightly adjusted subject to actual working temperature during the extraction process.

The high speed centrifuge separation process for re-refined base oil 20 is adapted to separate the re-refined base oil and the extract of the extracted product obtained through the re-refined base oil extraction process 10 by means of a high speed disc separator, removing sulfides and aromatic compounds of relatively higher specific gravity, and reducing the workload of the short path evaporator in the re-refined base oil recovery process 30 to accelerate the application of the re-refined base oil recovery process 30.

Running the high speed centrifuge separation process for re-refined base oil 20 requires the equipments of a plurality of material delivery pumps 21, one high speed disc separator 22, one re-refined base oil buffer tank 23, one by-product storage tank 24, and a plurality of by-product outlet pumps 25.

When the fluid level in the re-refined base oil and extract buffer tank 16 reaches a predetermined value during the operation of the high speed centrifuge separation process for re-refined base oil 20, the material delivery pumps 21 are started to pump the re-refined base oil and extract fluid mixture out of the re-refined base oil and extract buffer tank 16 into the high speed disc separator 22, enabling the high speed disc separator 22 to separate the re-refined base oil in the upper layer of the fluid mixture from the extract in the lower layer of the fluid mixture. The separated re-refined oil is delivered through a respective piping to the re-refined base oil buffer tank 23, and the separated extract is delivered through a respective piping to the by-product storage tank 24. When the fluid level in the by-product storage tank 24 reaches a predetermined value, the by-product outlet pumps 25 are started to pump the extract out of the by-product storage tank 24.

The re-refined base oil recovery process 30 is adapted to perform the core operation of short path distillation subject to the following characteristics: a) Prepare re-refined base oil recovery process 30 equipments, comprising a plurality of re-refined base oil recovery process material delivery pump 31/32/33, one re-refined base oil recovery process pre-heater 34, one re-refined base oil recovery process short path evaporator 35, one re-refined base oil recovery process thermal oil expansion tank 36, one re-refined base oil recovery process thermal oil heating furnace 37, a plurality of re-refined base oil recovery process thermal oil delivery pumps 38, one re-refined base oil finished product deposit tank 391, one re-refined base oil recovery process by-product deposit tank 392, one re-refined base oil recovery process vacuum buffer tank 393, one re-refined base oil recovery process gas-liquid separator 394, one re-refined base oil recovery process vacuum pump system 395, one re-refined base oil finished product storage tank 396, a plurality of re-refined base oil recovery process finished product outlet pumps 397. one by-product storage tank 24, and a plurality of by-product outlet pumps 25.

b) In actual operation of the re-refined base oil recovery process 30, initiate the re-refined base oil recovery process thermal oil heating furnace 37 and the re-refined base oil recovery process thermal oil delivery pump 38 where one flow of thermal oil is being circulate through the re-refined base oil recovery process thermal oil heating furnace 37 via a fluid passage in the cylinder wall of the re-refined base oil recovery process short path evaporator 35 and a fluid passage in the heating layer of the re-refined base oil recovery process pre-heater 34; another flow of thermal oil is being delivered through a sub piping to the re-refined base oil recovery process thermal oil expansion tank 36 and then back to the re-refined base oil recovery process thermal oil delivery pump 38 and then to the re-refined base oil recovery process thermal oil heating furnace 37; this pre-heating process is continued till the temperature of the cylinder wall of the re-refined base oil recovery process short path evaporator 35 and the temperature of the heating layer of the re-refined base oil recovery process pre-heater 34 reach the predetermined working temperature level; the re-refined base oil recovery process thermal oil heating Furnace 37 will stop heating after reached the predetermined working temperature, and will start to heat again when the temperature of the returned thermal oil dropped below the predetermined temperature level, i.e., the re-refined base oil recovery process thermal oil heating furnace 37 will he intermittently started to maintain the desired system working temperature; the control of the heating power and temperature of the re-refined base oil recovery process thermal oil heating furnace 37 is performed through a diode based heating fluid controller (not shown).

c) During operation of the thermal oil heating system of the re-refined base oil recovery process 30, the re-refined base oil recovery process vacuum pump system 395 is simultaneously started to pump air out of the re-refined base oil recovery process short path evaporator 35, the re-refined base oil finished product deposit tank 391 and the re-refined base oil recovery process by-product deposit tank 392 via the re-refined base oil recovery process vacuum buffer tank 393 and re-refined base oil recovery process gas-liquid separator 394. The re-refined base oil recovery process vacuum pump system 395 stops pumping immediately after the vacuum pressure in the related piping reaches the predetermined working pressure.

Thereafter, material feeding is started, causing rise in the internal working pressure of the re-refined base oil recovery process short path evaporator 35. When the internal working pressure rises, the re-refined base oil recovery process vacuum pump system 395 is started again, i.e., the re-refined base oil recovery process vacuum pump system 395 works intermittently to maintain the system working pressure. This operation manner enables the internal working pressure of the re-refined base oil recovery process short path evaporator 35 of the re-refined base oil recovery process 30 to be maintained within the predetermined range, assuring a high level of system stability.

d) The operation is started when system preparation is done. When the fluid level in the re-refined base oil and extract buffer tank 23 of the high speed centrifuge separation process for re-refined base oil 20 reaches a predetermined high level position. the re-refined base oil recovery process material delivery pump 31 is started to pump the extracted mixture of re-refined base oil and extract through the re-refined base oil recovery process pre-heater 34 for indirect heating; the fluid material passing through the re-refined base oil recovery process pre-heater 34 for indirect heating is delivered to a distribution panel at a top side inside the re-refined base oil recovery process short path evaporator 35, and then guided by a discharge gap. which is disposed in a diagonal relationship with the vacuum exhaust port, downwardly along a cylinder into the re-refined base oil recovery process short path evaporator 35; the re-refined base oil recovery process short path evaporator 35 has a scrapper module mounted therein and rotatable by a top-sided motor 351 through a gear speed reducer 352 at a speed about 160-180r.p.m. with spring-loaded front blades thereof stopped against the internal cylinder wall of the re-refined base oil recovery process short path evaporator 35 to spread downward falling re-refined base oil onto the internal cylinder wall of the re-refined base oil recovery process short path evaporator 35 so that a thin film of re-refined base oil of a predetermined thickness can he formed on the internal cylinder wall of the re-refined base oil recovery process short path evaporator 35; when the material is being distributed through the distribution panel into the inside of the cylinder wall of the re-refined base oil recovery process short path evaporator 35. the cylinder wall of the re-refined base oil recovery process short path evaporator 35 is being continuously pre-heated, the internal working pressure and temperature are locked, enabling the re-fined base oil to be optimally evaporated and refined; thus, when the re-fined base oil is being distributed into the inside of the cylinder wall of the re-refined base oil recovery process short path evaporator 35 and spread by the graphite blades of the scraper module to form an oil film on the internal cylinder wall of the re-refined base oil recovery process short path evaporator 35, it will he heated to release out re-refined base oil molecules for free traveling, enabling the re-refined base oil molecules to enter the internal condenser (not shown) in the re-refined base oil recovery process short path evaporator 35 subject to the pumping effect of the re-refined base oil recovery process vacuum pump system 395, thus, the molecules of the transiently heated target thin film of re-refined base oil are immediately evaporated and released out; the continuous pumping operation of the re-refined base oil recovery process vacuum pump system 395 causes formation of a relatively low pressure in let for the passing of the molecules; however, because the re-refined base oil recovery process short path evaporator 35 has the condenser (not shown) vertically disposed therein at the center, the re-refined base oil molecifies wifl touch the condenser coils of the condenser before passing through the condenser to the exhaust port; because the condenser coils has a cooling water flowing therethrough. the re-refined base oil molecules are immediately cooled down and condensed into a liquid state to flow into the beneath re-refined base oil finished product deposit tank 391; when the fluid in the beneath re-refined base oil finished product deposit tank 391 reaches a high level, the re-refined base oil recovery process material delivery pump 32 is automatically started to pump the cumulated re-refined base oil out of the re-refined base oil finished product deposit tank 391 to the re-refined base oil finished product storage tank 396 and then pumped out of the re-refined base ofl finished product storage tank 396 by re-refined base oil recovery process finished product outlet pumps 397 for deflvery and further application.

e) During the re-refined base oil recovery process 30, the minor amount of extracts that are adhered to the re-refined base oil and contain impurities such as sulfur and aromatics are synchronously delivered to the re-refined base oil recovery process short path evaporator 35, however because the internal working pressure and working temperature in the re-refined base oil recovery process short path evaporator 35 are still below the predetermined values, the minor amount of extracts in the mixture will not he evaporated into molecules and will he maintained in the form of a suspension and guided along the internal cylinder wall into an oblique hopper at the bottom side of the re-refined hase oil recovery process short path evaporator 35 and then discharged into the re-refined base oil recovery process by-product deposit tank 392; when the fluid in the re-refined base oil recovery process by-product deposit tank 392 reaches a predetermined high level, the re-refined base oil recovery process material delivery pump 33 is automatically started to pump this by-product into the by-product storage tank 24 for storage; when the fluid in the by-product storage tank 24 reaches a predetermined high level, the by-product outlet pump 25 is started to pump the by-product out of the by-product storage tank 24.

The utility facility process 40 is adapted to provide cooling water and chilled water to the internal condenser of the re-refined base oil recovery process short path evaporator 35 and the internal condenser of the NMP recovery process short path evaporator 55 of the NMP recovery process 50 and the related external cold wells.

The utility facility process 40 provides a cooling tower 41, a chiller 42, a plurality of chilled water delivery pumps 43. a cooling water recycling pump 44, and cooling water delivery pumps 45/46.

When starting the utility facility process 40, all the equipments of the utility facility process 40 are turned on, enabling chilled water and cooling water to he pumped by the chilled water delivery pumps 43 and the cooling water delivery pumps 45/46 to the target equipments, i.e., the re-refined base oil recovery process short path evaporator 35 and the cooling water inlet pipeline of the NMP Recovery process short path evaporator 55, and then delivered by the cooling water recycling pump 44 through recycling pipelines to the cooling tower 41 for cooling, and thus, the recycled cooling water is kept at the predetermined working temperature level; subject to system requirements, the temperawre of the delivered cooling water is about 25-28°C, the temperature of the recycled cooling water is about 30-33°C, and the temperature dilierence between these two flows of water is about 5°C; therefore, the heat dissipation capacity of the cooling tower 41. the working pressure and flow rate of each individual cooling water delivery pump and other related parameters are determined subject to individual conditions and requirements of the operating system to satisfy actual requirements.

In one application example of the present invention, the internal working pressure of the re-refined base oil recovery process short path evaporator 35 is set at 20-25Pa (Pascal).

In one application example of the present invention, the internal working temperature of the re-refined base oil recovery process short path evaporator 35 is set at I 90-205t.

In one application example of the present invention, the graphite blades of the scraper module in the re-refined base oil recovery process 30 is adapted to spread the supplied mixture of re-refined base oil and extracts on the internal cylinder wall of the re-refined base oil recovery process short path evaporator 35 to form an oil film of thickness less then 1mm.

In one application example of the present invention, the re-refined base oil recovery process short path evaporator 35 in the re-refined base oil recovery process 30 has connected thereto a cooling well 353. a re-refined base oil recovery process material delivery pump 354, and a material storage tank 355; in the evaporation operation of the re-refined base oil recovery process short path evaporator 35, there are some light hydrocarbons such as C115ll222 whose molecular weight is lower than the re-refined base oil to he recycled and whose mean free path is longer than the re-refined base oil to be recycled; during the operation, these minor amount of light hydrocarbons will he simultaneously evaporated and released out of the internal condenser of the re-refined base oil recovery process short path evaporator 35 into the exhaust passageway and then trapped by the cold well 353; the light hydrocarbons contain a volatile gas and the predetermined working temperature is as high as I 90°C-205°C, and therefore. in order to prevent the light hydrocarbons from entering the pipeline of the vacuum system to damage the re-refined base oil recovery process vacuum pump system 395. a condensing coil is provided in the utility facility process 40 For continuously guiding 5°C chilled water into the cold well 353 to condense the light hydrocarbons in the cold well 353; thereafter, as soon as the fluid in the cold well 353 reaches a predetermined high level, the re-refined base oil recovery process material delivery pump 354 is started to pump the fluid material out of the cold well 353 into the material storage tank 355 for further delivery; the chilled water for this condensing system is provided by the chiller 42 of the utility facility process 40; during operation, the 5°C chilled water generated by the chiller 42 is pumped by the internal pump of the chiller 42 to the cold well 353 for condensing, enabling the condensed water to he sent hack to the chiller 42 for chilling, enabling the chilled 5°C water to be Further delivered to the cold well 353 again; further, in order to prevent overheat of the lubricant of the gear speed reducer 352 of the re-refined base oil recovery process short path evaporator 35 and further gear speed reducer damage due to continuous long period operation. a branch pipeline is provided to guide a part of the generated chilled water from the chiller 42 to the axle seals of the re-refined base oil recovery process short path evaporator 35 to cool down the axle seals, and the used cooling water is then delivered with the discharged condensed water of the cold well 353 back to the water chiller 42 by a cooling water circulating pipeline.

In an alternate form of the present invention, the method for desulfurizing re-refined base oil and removing aromatic compounds from re-refined base oil further comprises a NMP recovery process 50.

The NMP recovery process 50 is adapted to perform the core operation of short path distillation subject to the following characteristics: a) The NMP recovery process 50 needs to use the equipments of: a plurality of NMP recovery process material delivery pumps 51/52/53, one NMP recovery process pre-heater 54, one NMP recovery process short path evaporator 55, one NMP recovery process thermal oil expansion tank 56, one NMP recovery process thermal oil heating furnace 57. one NMP recovery process thermal oil delivery pump 58, one NMP buffer tank 591, one NMP recovery process by-product deposit tank 592, one NMP recovery process vacuum buffer tank 593, one NMP recovery process gas-liquid separator 594. one NMP recovery process vacuum pump system 595, one NMP recovery process storage tank 596. one NMP recovery process by-product storage tank 597, a plurality of NMP recovery process outgoing pump 598, and a plurality of NMP recovery process by-product outlet pumps 599.

b) During operation of the NMP recovery process 50, start the NMP recovery process thermal oil heating furnace 57 and the NMP recovery process thermal oil delivery pump 58 to pump a thermal oil through the cylinder jacket of the NMP recovery process short path evaporator 55 and the thermal oil heating jacket of the NMP recovery process pre-heater 54 and then back to the NMP recovery process thermal oil heating furnace 57; another flow of thermal oil is delivered through a branch pipeline to the NMP recovery process thermal oil expansion tank 56 and the NMP recovery process thermal oil delivery pump 58 and then back to the NMP recovery process thermal oil heating furnace 57; the pre-heating operation keeps going till that the temperature of the cylinder jacket of ihe NMP recovery process short path evaporator 55 and the temperature of the thermal oil heating jacket of the NMP recovery process pre-heater 54 reach the predetermined working temperature, and the NMP recovery process thermal oil heating Furnace 57 is stopped from heating when the predetermined working temperature is obtained, or started again when the temperature of the returned therma' oil drops below the predetermined working temperature; the heater power and heating temperature of the NMP recovery process thermal oil heating furnace 57 are controlled by a diode-based heating fluid controller and a programmable logic controller (not shown).

c) During the operation of the thermal oil heating system of the NMP recovery process 50, the NMP recovery process vacuum pump system 595 is simultaneously started to draw air out of the NMP recovery process short path evaporator 55, the NMP buffer tank 591 and the NMP recovery process by-product deposit tank 592 via the NMP recovery process vacuum buffer tank 593 and the NMP recovery process gas-liquid separator 594, and the NMP recovery process vacuum pump system 595 is stopped from pumping when the pressure in the entire pipeline system reaches a predetermined working pressure, and then material feeding is started, and the NMP recovery process vacuum pump system 595 will be started again as the internal working pressure of the NMP recovery process short path evaporator 55 rises, i.e., the NMP recovery process vacuum pump system 595 works intermittenily to maintain the internal working pressure of the NMP recovery process short path evaporator 55 within the set range, assuring system operation stability.

d) After system preparation is done, the NMP recovery processing process is started; if the fluid mixture of the NMP and extracts in the buffer tank 17 of the re-refined base oil extraction process 10 reaches the predetermined high ev&, the NMP recovery process material deilvery pump 51 is started to pump the fluid mixture of the NMP and extracts through the NMP recovery process pre-heater 54 for indirect heating; the fluid material being heated by the NMP recovery process pre-heater 54 is guided by a discharge gap in a diagonal relationship with the vacuum exhaust port downwardly along a cylinder into the to the internal distribution panel of the NMP recovery process short path evaporator 55; the to the internal distribution panel of the NMP recovery process short path evaporator 55 has a scrapper module mounted therein and rotatable by a top-sided motor 551 through a gear speed reducer 552 at a speed about 16O-180r.p.m. with spring-loaded front blades thereof stopped against the internal cylinder wafi of the NMP recovery process short path evaporator to spread downward falling re-refined base oil onto the internal cylinder wall of the NMP Recovery process short path evaporator 55 so that a thin film of re-refined base oil of a predetermined thickness can be formed on the internal cylinder wall of the NMP recovery process short path evaporator 55; when the material is being distributed through the distribution panel into the inside of the cylinder wall of the NMP recovery process short path evaporator 55, the cyflnder wafl of the NMP recovery process short path evaporator 55 is being continuously pre-heated, the internal working pressure and temperature are locked, enahflng the re-fined base oil to he optimally evaporated and refined; thus, when the re-fined base oH is being distributed into the inside of the cyhnder wafl of the NMP recovery process short path evaporator 55 and spread by the graphite blades of the scraper module to form an oil film on the internal cylinder wall of the NMP recovery process short path evaporator 55, it will be heated to release out re-refined base oil molecules for free traveling, enabling the re-refined base oil molecules to enter the internal condenser (not shown) in the NMP recovery process short path evaporator 55 subject to the pumping effect of the NMP recovery process vacuum pump system 595, thus, the molecules of the transiently heated target thin film of re-refined base oil are immediately evaporated and released out; the continuous pumping operation of the NMP recovery process vacuum pump system 595 causes formation of a relatively low pressure inlet for the passing of the molecules; however, because the NMP recovery process short path evaporator 55 has the condenser (not shown) vertically disposed therein at the center, the re-refined base oil molecules will touch the condenser coils of the condenser before passing through the condenser to the exhaust port; thus, when the re-fined base oil is being distributed into the inside of the cylinder wall of the NMP recovery process short path evaporator 55 and spread by the graphite blades of the scraper module to form an oil film on the internal cylinder wall of the NMP recovery process short path evaporator 55, it will he heated to release out re-refined base oil molecules for free traveling, enabling the re-refined base oil molecules to enter the internal condenser (not shown) in the NMP recovery process short path evaporator 55 subject to the pumping effect of the NMP recovery process vacuum pump system 595, thus, the molecules of the transiently heated target thin film of re-refined base oil are immediately evaporated and released out; the continuous pumping operation of the NMP recovery process vacuum pump system 595 causes formation of a relatively low pressure inlet for the passing of the molecules; however, because the NMP recovery process short path evaporator 55 has the condenser (not shown) vertically disposed therein at the center, the re-refined base oil molecules will touch the condenser coils of the condenser before passing through the condenser to the exhaust port; because the condenser coils has a cooling water flowing therethrough, the re-refined base oil molecules are immediately cooled down and condensed into a liquid state to flow into the NMP buffer tank 591; when the fluid in the NMP buffer tank 591 reaches a high level, the NMP recovery process material delivery pump 52 is automatically started to pump the cumulated re-refined base oil out of the NMP buffer tank 591 to the NMP recovery process storage tank 596; when the fluid level in the NMP recovery process storage tank 596 reaches a high level, the NMP recovery process outgoing pump 598 is started to pump out the storage NMP fluid.

e) During the NMP recovery process 59, the minor amount of extracts that are adhered to the re-refined base oil and contain impurities such as sulfur and aromatics are synchronously deilvered to the NMP recovery process short path evaporator 55, however because the internal working pressure and working temperature in the NMP recovery process short path evaporator 55 are still h&ow the predetermined values, the minor amount of extracts in the mixture will not be evaporated into molecules and will be maintained in the form of a suspension and guided along the internal cylinder wall into an oblique hopper at the bottom side of the NMP recovery process short path evaporator 55 and then discharged into the NMP recovery process by-product deposit tank 592; when the fluid in the NMP recovery process by-product deposit tank 592 reaches a predetermined high level. the NMP recovery process material delivery pump 53 is automatically started to pump this by-product into the NMP recovery process by-product storage tank 597 for storage; when the fluid in the NMP recovery process by-product storage tank 597 reaches a predetermined high lev&, the NMP recovery process by-product ouflet pump 599 is started to pump the by-product out of the NMP recovery process by-product storage tank 597.

In one application example of the present invention, the internal working pressure of the NMP recovery process short path evaporator 55 is set at 20-25Pa (Pascal).

In one application example of the present invention, the internal working temperature of the NMP recovery process short path evaporator 55 is set at 11O-120°C.

In one application example of the present invention, the graphite blades of the scraper module in the NMP recovery process SO is adapted to spread the supplied mixture of re-refined base oil and extracts on the internal cylinder wall of the NMP recovery process short path evaporator to form an oil film of thickness less then 1mm.

In one application example of this alternate form, the NMP recovery process short path evaporator 55 in the NMP recovery process 50 has connected thereto a cooling well 553, a NMP recovery process material delivery pump 554, and a NMP material storage tank 555; in the evaporation operation of the NMP recovery process short path evaporator 55, there are some light hydrocarbons such as C1015H2232, ihese light hydrocarbons have a low molecular weight and long mean free path and can he evaporated under the working pressure of 2OPa and working temperature of I I0°C-l30°C; during the operation, these minor amount of light hydrocarbons will he simultaneously evaporated and released out of the internal condenser of the NMP recovery process short path evaporator into the exhaust passageway and then trapped by the cold well 553; the light hydrocarbons contain a volatile gas and the predetermined working temperature is as high as 1 1O°C-430°C, and therefore, in order to prevent the light hydrocarbons from entering the pipeline of the vacuum system to damage the NMP recovery process vacuum pump system 395, a condensing cofl is provided in the utility facflhy process 40 for continuous'y guiding 5°C chilled water into the cold well 353 to condense the light hydrocarbons in the cold well 553; thereafter, as soon as the fluid in the cold well 553 reaches a predetermined high level, the NMP recovery process material delivery pump 554 is started to pump the fluid material out of the cold well 553 into the NMP material storage tank 555 for further delivery; the chilled water for this condensing system is provided by the chifler 42 of the utility facility process 40; during operation, the 5°C chilled water generated by the chifler 42 is pumped by the interna' pump of the chifler 42 to the cold wefl 553 for condensing, enabling the condensed water to be sent back to the chiller 42 for chilling, enabling the chilled 5°C water to be further delivered to the cold well 553 again; further, in order to prevent overhear of the lubricant of the gear speed reducer 552 of the re-refined base oil recovery process short path evaporator 35 and further gear speed reducer damage due to continuous long period operation, a branch pipeline is provided to guide a part of the generated chilled water from the chiller 42 to the axle seals of the NMP recovery process short path evaporator 55 to cool down the axle seals, and the used cooling water is then delivered with the discharged condensed water of the cold well 553 back to the water chiller 42 by a cooling water circulating pipeline.

Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may he made without departing from the spirit and scope of ihe invention. According'y, the invention is not to he limited except as by the appended claims.

Claims

What the invention claimed is: 1. A method for desulfurization and aromatic compounds removal of a re-refined base oil being recovered from waste lubricating oil with the use of NMP (N-Methyl Pyrrolidinone) as an extracting agent, the method comprising: (I) a re-refined base oil extraction process for mixing said re-refined base oil with NMP (N-Methyl Pyrrolidinone) and performing the extraction process of desulfurization and aromatics removal; (2) a high speed centrifuge separation process using a high speed disc separator to separate sulfide and aromatics from the fluid mixture obtained from step (1) so as to obtain a mixture of re-refined base oil and extracts; (3) a re-refined base oil recovery process for performing a core operation of short path distillation, said re-refined base oil recovery process comprising: a) a set of preparation equipments comprising a plurality of re-refined base oil recovery process material delivery pump, one re-refined base oil recovery process pre-heater, one re-refined base oil recovery process short path evaporator, one re-refined base oil recovery process thermal oil expansion tank, one re-refined base oil recovery process thermal oil heating furnace, a plurality of re-refined base oil recovery process thermal oil delivery pumps, one re-refined base oil finished product deposit tank, one re-refined base oil recovery process by-product deposit tank, one re-refined base oil recovery process vacuum buffer tank. one re-refined base oil recovery process gas-liquid separator, one re-refined base oil recovery process vacuum pump system, one re-refined base oil finished product storage tank, a plurality of re-refined base oil recovery process finished product outlet pumps, one by-product storage tank, and a plurality of by-product outlet pumps; h) driving said re-refined base oil recovery process thermal oil heating furnace and said re-refined base oil recovery process thermal oil delivery pump to circulate a thermal oil through a cylinder jacket of said re-refined base oil recovery process short path evaporator and a heating jacket of said re-refined base oil recovery process pre-heater and said re-refined base oil recovery process thermal oil heating furnace and to deliver another flow of said thermal oil through said re-refined base oil recovery process thermal oil expansion tank and then back to said re-refined base oil recovery process thermal oil heating furnace to the extent that the temperature of said cylinder jacket of said re-refined base oil recovery process short path evaporator and the temperature of said heating jacket of said re-refined base oil recovery process pre-heater reaches a predetermined working temperature, and then intermittently running said re-refined base oil recovery process thermal oil heating furnace to maintain said predetermined temperature level; c) starting said re-refined base oil recovery process vacuum pump system to pump air out of said re-refined base oil recovery process short path evaporator, said re-refined base oil finished product deposit tank and said re-refined base oil recovery process by-product deposit tank via said re-refined base oil recovery process vacuum huffer tank and said re-refined base oil recovery process gas-liquid separator till that the internal pressure of said re-refined base oil recovery process short path evaporator, said re-refined base oil finished product deposit tank and said re-refined base oil recovery process by-product deposit tank reaches a predetermined working pressure level, and then intermittently running said re-refined base oil recovery process vacuum pump system to maintain said predetermined working pressure; d) driving one said re-refined base oil recovery process material delivery pump to pump the fluid mixture of re-refined base oil and extracts produced in said high speed centrifuge separation process for re-refined base oil through said re-refined base oil recovery process pre-heater for heating and to continuously pump the fluid mixture to said re-refined base oil recovery process short path evaporator, enabling the fluid mixture to be spread by graphite blades of an internal scraper of said re-refined base oil recovery process short path evaporator onto an internal cylinder wall of said re-refined base oil recovery process short path evaporator to form an oH mm of a predetermined thickness, said oil film being further evaporated by the head of said cyhnder jacket of said re-refined base oH recovery process short path evaporator to release out re-refined base oil molecules for free travel, the released said re-refined base oil molecules being pumped by said re-refined base oil recovery process vacuum pump system to an internal condenser of said re-refined base oil recovery process short path evaporator and then condensed into a re-refined base oil that is then delivered into said re-refined base oil finished product deposit tank and then said re-refined base oil finished product storage tank; and e) the extracts left in said re-refined base oil recovery process short path evaporator in a fluid state being guided into said re-refined base oil recovery process by-product deposit tank and said re-refined base oil recovery process by-product storage tank; and (4) a utility facility process using a cooling tower and a chiller to generate and circulate a chilled water for circulating through said re-refined base oil recovery process short path evaporator and an externa' cold wefl for condensing the produced re-refined base oil.
2. The method as daimed in daim 1, wherein said predetermined working pressure of said re-refined base oil recovery process short path evaporator is in the range of 20-2SPa.
3. The method as daimed in daim 1, wherein said predetermined working temperature of said re-refined base oil recovery process short path evaporator is in the range of 190-205°C
4. The method as claimed in claim 1, wherein the oil film formed of the fluid mixture being spread by said graphite blades of said internal scraper of said re-refined base oil recovery process short path evaporator onto said internal cylinder wafl of said re-refined base oil recovery process short path evaporator has a thickness tess then 1mm.
5. The method as claimed in claim 1, wherein said re-refined base oH recovery process short path evaporator of said re-refined base oil recovery process has connected thereto a cold well, a re-refined base oil recovery process material delivery pump and a material storage tank, said cold well being adapted to trap light hydrocarbons produced by said re-refined base oil recovery process short path evaporator during condensing, enabling the material being condensed in said cold well to he delivered to said material storage tank by said re-refined base oil recovery process material delivery pump for further delivery.
6. The method as claimed in claim 1, further comprising a NMP recovery process for running short path distillation, said NMP recovery process comprising: a) preparing NMP recovery process equipments of a plurality of NMP recovery process material delivery pumps. one NMP recovery process pre-heater, one NMP recovery process short path evaporator, one NMP recovery process thermal oil expansion tank, one NMP recovery process thermal oil heating furnace, one NMP recovery process thermal oil delivery pump, one NMP buffer tank, one NMP recovery process by-product deposit tank, one NMP recovery process vacuum buffer tank, one NMP recovery process gas-liquid separator.one NMP recovery process vacuum pump system, one NMP recovery process storage tank, one NMP recovery process outgoing pump, one NMP recovery process by-product storage tank and one NMP recovery process by-product outlet pump; b) driving NMP recovery process thermal oil heating furnace and the NMP recovery process thermal oil delivery pump to pump one flow of thermal oil to circulate through the cylinder jacket of the NMP recovery process short path evaporator and the heating jacket of the NMP recovery process pre-heater and then back to the NMP recovery process thermal oil heating furnace and another flow of thermal oil through said NMP recovery process thermal oil expansion tank and then hack to said NMP recovery process thermal oil heating furnace till that the temperature of said cylinder jacket of said NMP recovery process short path evaporator and the temperature of said heating jacket of said NMP recovery process pre-heater reaches a predetermined working temperature level, and then said NMP recovery process thermal oil heating furnace being intermittently initiated to maintain said working temperature level; c) driving said NMP recovery process vacuum pump system to pump air out of said NMP Recovery process short path evaporator, said NMP buffer tank and said NMP recovery process by-product deposit tank via said NMP recovery process vacuum buffer tank and said NMP recovery process gas-liquid separator till that the internal pressure of said NMP Recovery process short path evaporator, said NMP buffer tank and said NMP recovery process by-product deposit tank reaches a predetermined working pressure level, and said NMP recovery process vacuum pump system being intermittently initiated to maintain said working pressure level; d) driving one said NMP recovery process material delivery pump to pump the fluid mixture of NMP and extracts produced in said re-refined base oil extraction process through said NMP recovery process pre-heater to said NMP recovery process short path evaporator, enabling the fluid mixture of NMP and extracts to he pre-heated by said NMP recovery process pre-heater before entering said NMP recovery process short path evaporator, said NMP recovery process short path evaporator comprising an internal scraper having graphite blades for spreading the NMP fluid mixture of NMP and extracts on an internal cylinder wall of said NMP recovery process short path evaporator to form an oil film, said oil film being heated by the heat of said cylinder jacket of said NMP recovery process short path evaporator to release out NMP molecules for free travel, said NMP molecules being caused by a vacuum effect to fly to an internal condenser of said NMP recovery process short path evaporator for condensing into a fluid state for delivery through said NMP buffer tank to said NMP storage tank; and e) the waste fluid in said NMP recovery process short path evaporator being forced by the gravity thereof to fall to a hopper at a bottom side of said NMP recovery process short path evaporator and then discharged into said NMP recovery process by-product deposit tank and then delivered to said NMP recovery process by-product storage tank.
7. The method as claimed in claim 6. wherein said predetermined working pressure of said NMP recovery process short path evaporator is in the range of 20-25Pa.
8. The method as claimed in claim 6, wherein said predetermined working temperature of said NMP recovery process short path evaporator is in the range of 110-130°C
9. The method as claimed in claim 6, wherein the oil film formed of the fluid mixture being spread by said graphite blades of said internal scraper of said NMP recovery process short path evaporator onto said internal cylinder wall of said NMP recovery process short path evaporator has a thickness less then 1mm.
10. The method as claimed in claim 6, wherein said NMP recovery process short path evaporator of said NMP recovery process has connected thereto a cold well, a NMP recovery process material delivery pump and a NMP storage tank, said cold well being adapted to trap light hydrocarbons produced by said NMP Recovery process short path evaporator during condensing, enabling the material being condensed in said cold well to he delivered to said NMP storage tank by said NMP recovery process material delivery pump for further delivery.