NO170429B - PROCEDURE FOR REFINING USED LUBRICATING OILS AND APPLIANCES FOR USING THE PROCEDURE - Google Patents

Description

The present invention relates to a method for refining used lubricating oils and an apparatus for use in the method. •

More specifically, the invention relates to an efficient and environmentally friendly method for refining used lubricating oils into high-quality lubricating oils using a vacuum distiller of the type described in more detail below.

The general method according to the invention for re-refining used lubricating oils into high-quality lubricating oils shall initially be described quite briefly with reference to figure 1 where the steps: I include deposition of freed water, distillation of

residual water and lighter hydrocarbons as well as drying;

II includes the production of fuel oil by fractionation;

III comprises cyclonic vacuum distillation where the lubricating oil fractions are distilled from contaminants such as metal residues, sludge and soot; and

IV includes hydrogen treatment (polishing) of the lubricating oil,

after heating in a settling tank, with final fractionation.

In light of today's environmental requirements and the resulting environmental policy, it is becoming increasingly important to ensure that emissions of harmful and environmentally harmful pollutants to nature are kept to a minimum.

This also applies to cases where the emissions themselves are small but where an accumulation can lead to unfavorable or even catastrophic consequences.

In light of today's economic situation, it is also increasingly important to seek to perfect recycling processes in order to be able to utilize the values that would otherwise be wasted during the simultaneous separation of harmful substances that, for example, originate from additives from the time when you were not aware of these substances' adverse side effects.

There are a large number of well-known facilities in the area which work according to principles known in and of themselves and which aim to process used lubricating oils in order to take care of the existing values and at the same time to be able to separate and deposit harmful substances in a safe way.

These facilities are all based on process engineering and chemical considerations which are known in and of themselves and where the individual components depend to a significant extent on the location of the facility and its interconnection with existing facilities in terms of heat sources, energy sources, combustion possibilities and so on.

However, relatively little has been done when it comes to the purely technical design of the device, with the result that there is still a need for improvements in various areas.

A step which until now has not been completely satisfactory in the process outlined above is the execution of the cyclonic vacuum distillation under point 3 above where the lubricating oil fractions are distilled from contaminants such as metal residues, sludge and soot.

According to this, the present invention relates to a method for the redistillation of used lubricating oils into high-quality lubricating oils, comprising

1) deposition of freed water, distillation of residual water and light hydrocarbons; 2) fractionated production of fuel oils and separation of a residual material; 3) cyclonic vacuum distillation of the residue from step 2) for the distillation of lubricating oil fractions and separation of impurities; and 4) hydrogen treatment of the lubricating oils obtained in step 3)

for final processing for new use;

and this method is characterized by the fact that the cyclonic vacuum distillation in step 3) is carried out using a vacuum still as described in the characterizing part of claim 1.

As indicated above, the invention also relates to an apparatus for carrying out step III in the above-mentioned method and this apparatus is characterized by a vacuum distiller as described in the characterizing part of claim 2.

The invention shall be described in more detail with reference to the attached drawings where: figure 1 is a flow chart of the overall process; - figure 2 shows a section through a vacuum distiller according to the invention.

The general procedure for recycling used lubricating oils starts with the collection of all forms of used lubricants in a reception facility for classification.

Good qualities 1 are pumped to a settling tank 2 where an initial heating to 25°C takes place.

Free water is deposited as a bottom layer and drained to a water tank, while oil is deposited as the upper layer and the oil obtained there is transferred to a storage tank 5. From this storage tank 5, water-poor oil 6 is then pumped to a drying plant 7 where a heat exchange is carried out with a previously obtained distillation residue 22, after which it is all fed to a mixing nozzle 8.

In the nozzle 8, the oil 6 is brought together with a heated dried oil 9 from the bottom of the drying plant 7. The residual water in the oil flow 6 evaporates in the mixing nozzle and distills off together with fuel residues and gas via the pipeline 10.

This material stream 10 is condensed and separated before it is taken to a separate, per se known destruction facility.

The dried oil 11 from the dryer 7 is fed to a mixing nozzle 12 where heated oil 13 from the bottom of a fractionation plant 14 is brought to the required temperature, then fed to a mixing nozzle 12 on a fractionation container 14 which works under a negative pressure of 100 to 500 mbar and at a temperature of 280 to 300°C.

In the fractionation plant 14, fuel oil 15 evaporates, which is condensed and fed to a storage tank.

The lubricating oil fraction 16 at the bottom of the fractionation stage 14 is pumped on to a mixing nozzle 17 on the vacuum distiller 18 of the invention which works under a negative pressure of 15 to 20 mbar and at a high temperature of 345 to 350°C.

In the vacuum distiller 18 of the invention, all lubricating oils are separated from the impurities present.

The lubricating oils evaporate via 19, condense and are fed to a settling tank 23 and from there to a storage tank 24.

The thickest oils and impurities, the distillation residues 20, are recycled via a furnace 21 for heating and then emit their energy in the mixing nozzle 17 of the vacuum distiller 18 of the invention.

The distillation residue 22 thus produced is pumped via a heat exchanger as mentioned above to storage.

In the settling tank 23, "flying particles" which came with the lubricating oil distillate 19 from the vacuum distiller 18 of the invention meet, these form flakes or large particles which in turn form a sludge which is deposited in the tank.

This sludge 26' is then withdrawn from the settling tank 23 for burning in the above-mentioned separate destruction plant. Oil from the settling tank 23 is fed via line 25 to a clarification tank 24 from which additional sludge 26'' is removed and incinerated as above.

The obtained, clarified lubricating oil 27 is then pumped via a heat exchanger and furnace 28 for a per se conventional hydrogen treatment in the reactor 29.

Hydrogen gas for this purpose is produced separately, for example in a production unit 30 using the electrolysis of water, where the production is adapted to the amount of hydrogen 31 that must be fed to the reactor 29.

The hydrogen gas 31/oil 27 mixture is fed into the reactor 29, passes through the catalyst mass, for example in the form of a fixed bed mass, and out of the bottom of the apparatus.

The gas/oil mixture 32 is then fed to a separator 33 which separates the lubricating oil 34 from the excess hydrogen 35 which is pumped back to the hydrogen gas feed line 31.

Reaction gas 36 is burned off in the above-mentioned separate destruction facility.

The obtained lubricating oil 34 is passed on to a fractionation/drying tower 37 for separating the oil fractions according to viscosity, where 300 N oil is generally obtained at 38, 150 N oil at 39 and fuel oil/water at 40.

Fractions 38, 39 and 40 are then pumped to storage tanks while water is pumped to the above-mentioned separate destruction facility.

This is not described separately but generally includes a facility for burning and destroying waste streams by heat treatment, for example at 1200°C for 3 to 5 seconds.

In the case described here, these waste streams are exhaust gases from vacuum pumps, non-condensed gases from drying 10, fuel residues 10, reaction gas 36, deposition water 3, distilled water 10, distillation residue 22 and deposited sludge 26.

The secondary air for this destruction facility is preferably sucked off from the process hall's atmosphere and burned via a water trap and fire net in the destruction furnace.

For optimal utilization of the existing heat balance in the plant, in the combustion chamber of the destruction furnace in the destruction plant, the energy source is placed on the hot oil plant in the form of a double-wound pipe loop, and the flue gases are further dump-cooled for the exhaust gas purification.

Finally, the cleaned flue gas is led via the chimney to the atmosphere.

The vacuum distiller according to the invention is shown in Figure 2.

It comprises an inlet mixing nozzle or a mixing pipe 101 for introducing the material into the vacuum still which is delimited by a still wall 102 with an internal wall or a skirt 103.

Under the skirt 103, a conically slotted droplet catcher 104 is arranged.

The outside of the vacuum still is heated using an electric heating tape 105.

Externally, the vacuum distiller is also equipped with mounting aids such as a foot for mounting 106 and lifting lugs 111.

The middle part of the vacuum still, bounded by the still wall 102, is essentially cylindrical while the upper part has the form of an upwardly pointed conical top 112 and the lower part has the form of a downwardly pointed conical part 107 which merges into a substantial cylindrical outlet channel 108 for distillation residue which is connected by means of a flange 115 to an extended cylindrical outlet channel 109 which then via transfers and flanges passes into conventional pipeline equipment.

At the top, the conical part 112 is equipped with an outlet 114 for distillate which in turn at its lower end, the end which is inside the vacuum still and inside the skirt 103, is equipped with a drip ring 113.

In the vacuum distiller according to the invention, the mass to be distilled is blown in through the inlet and mixing pipe 101, tangentially to the still wall 102 and in the upper part of the annulus formed between the still wall 102 and the skirt 103.

According to the invention, this annular space preferably constitutes at least half of the cylindrical part of the vacuum still.

The lower part of the skirt is formed as a downwardly pointed cone in which slits 104a are arranged.

The top surface of this inverted truncated cone is preferably located approximately at the level of the lower part of the cylindrical part of the still wall.

The distillation residue 16 from step 2, see Figure 1, comes to the invention's vacuum still via the inlet mixing nozzle 101 in which it also meets heated distillation residue from the furnace 21.

The fractionated oil from stage II evaporates instantly, for example at 347°C and 0.02 bar absolute pressure and thereby splits into approx. 85% distillate and approx. 15% stillage.

Due to the enormous increase in volume in the inlet/mixing nozzle and the tangential feeding in connection with the installation of the inlet nozzle on the vacuum still, the vacuum still according to the invention already produces a separating effect when blown into the annulus.

The heavy distillate residue with the rest of the fractionated oil is flung against the still wall while the distillate gases are forced against the outer wall of the skirt 103.

Because of the new added material, the already partially separated material is forced downwards whereby the gases, after the skirt has passed into the conical part 104, have the opportunity to escape through the slits 104a and into the inner space of the skirt 103 and later to escape via the outlet 114.

On the outlet pipe 114, as mentioned above, a drip ring 113 is indicated which provides a further fractionating effect.

During evaporation as described here, energy is required and the oil part on the still wall 102 is given additional energy by means of an attached electric heating band 105.

The distillate residue is then initially transported in a spiral and later a more vertical path along the still wall towards the conical bottom 107 and finally flows down into the outlet channel 108.

With the distiller construction indicated above, the following advantages are achieved:

1. All unnecessary dead volume in the still has been removed as the skirt extends over approximately the entire length of the still. 2. The gas flowing in the annulus between the still wall 102 and the skirt 103 is given additional heating by means of the heat sink 105. This, together with the high velocity in the annulus, causes minimal coke formation and thereby also reduces the thermal splitting or cracking in the unit. 3. Due to the fact that large quantities of distillation residue circulate through the still, it can be about 40 m'/h, lower temperature increases occur over the furnace while at the same time maintaining the energy requirement for evaporation in the still.

The large volume of distillate residue prevents so-called dry zones on the still wall 102 and this means that a possible incipient coke formation is washed down.

Contamination in particulate form that comes with the mass of the vacuum still will constantly grind the wall and support cleanliness. 4. The fact that the skirt 103 is drawn all the way down to the end of the cylindrical part of the still, i.e. along the entire wall 102, means that a high gas velocity is maintained in the still, which in turn prevents coke formation.

As the lower part is conically shaped, the gas velocity will be reduced here, slits in the cone part of the skirt allow separated gas to penetrate to the center of the still together with gas that escapes under the lower edge of the inverted frustum that forms the lower part of the skirt .

Above these slits, as indicated in Figure 2, droplet catchers 104b are arranged, this prevents oil droplets or any distillation residue that flows down from the skirt being pulled along by the gases through the slits and accompanying the distillate. The drip rings in the lower part of the skirt, in the same way as the drip ring 113 on the outlet pipe 114, means that the drops will be large and thereby drip down to the conical bottom 107 of the still.

The relatively large inner space in the skirt provides a low gas velocity towards the outlet pipe, which also helps to reduce the danger of entrainment of droplets or flying particles, which helps to achieve a greatly improved product with increased purity from the vacuum distiller 18 in the plant as shown in Figure 1, which in turn greatly improves the quality achieved on products 38, 39 and 40 after the finishing in step 4 of the process as shown in Figure 1.

Claims (4)

1. Process for refining used lubricating oils into high-quality lubricating oils comprising the following steps: 1) deposition of freed water, distillation of residual water and light hydrocarbons; 2) fractional production of fuel oils; 3) cyclonic vacuum distillation of the lubricating oil fractions from contaminants such as metal salts, sludge and soot; and 4) final hydrogen treatment or polishing, above a catalyst with subsequent fractionation; characterized in that the cyclonic vacuum distillation is carried out in a vacuum still comprising a cylindrical part (102), a conically pointed part (112) with a drain tube (114), a lower conically pointed part (107) with drain pipe (108) and with an inner skirt, where the inner skirt consists of a cylindrical part (103) running parallel to the still wall (102) and a lower conical pointed part (104), equipped with slits and droplet catchers, the wall (102) being equipped with heating devices (105) substantially over the part covering the cylindrical part (103) of the skirt. 2. Vacuum distiller for use in the method according to claim 1, comprising a still wall (102), an upper conical part (112) with drain pipe (114) and a lower conical pointed part (107) with drain pipe (108), and further equipped with an inner skirt (103, 104), characterized in that the total length of the skirt (103, 104) essentially corresponds to the total length of the cylindrical still wall (102) of which the cylindrical part (103) constitutes approximately half the height of the wall (102), that the lower conical part (104) of the skirt is equipped with slits (104a) and droplet catchers (104b) and that the still wall (102) is equipped with heating bands (105) substantially above the part which envelops the cylindrical part (103) of the skirt .