CN1032671A - Recovery of lubricating oil - Google Patents

Abstract

A method for purifying the dirty oil of lubricating oil features that the dirty oil is heated and flash evaporated. The water is first flashed off and the fuel is then flashed off under reduced pressure. After flash evaporation, the oil is treated with a coagulant to flocculate the particles and submicron particles of insoluble material in the contaminated oil and the purified oil is separated for reuse.

Description

The present invention relates to the recovery of lubricating oil, and more particularly to a method by which contaminated lubricating oil, for example from the crankcase of an internal combustion engine, can be decontaminated for reuse.

After being used for a period of time in the internal combustion engine, the lubricating oil will be polluted by some carbon, metal and other insoluble particles and submicron particles, and also contain varying amounts of water and fuel. Over time, the performance of the lubricating oil is affected by these impurities, therefore, such lubricating oil must be replaced in order not to damage the engine. However, it has been found that as long as impurities can be removed, the performance of the lubricating oil itself remains basically unchanged.

A well-known method is to remove these impurities by flocculating insoluble particulates and submicron particles by adding coagulants. A suitable coagulant is an aqueous mixture containing amino compounds bearing hydroxyl groups and single or multiple oxygen groups. This coagulant separates the solid particles, resulting in a clean lubricating oil that can be reused. This method is described in British Railways patent application number 7905434. An advantage of this method is that unused lubricant additives are not affected.

However, how to remove liquid impurities remains a problem, which mainly refers to removing unburned fuel oil. In the past, these impurities were tolerated, and the purified oil was mixed with fresh oil to achieve the condition of reuse, so as to meet the physical properties required by users.

It is therefore an object of the present invention to remove these liquid impurities.

The method of the present invention is to heat the dirty oil to be purified, but the heating temperature is lower than the temperature at which the lubricating oil and its additives will be significantly decomposed, and carry out decompression flash evaporation to basically remove all condensed water. Next, the flash pressure is reduced to remove condensed fuel impurities while keeping the slop oil at a temperature below that at which it would decompose significantly. Afterwards, it is treated with a coagulant to flocculate and precipitate insoluble particles and submicron particles, and to separate the purified oil from solid impurities and coagulants for reuse.

By operating in this manner and removing the water first, a simple device can be used. Therefore, the pressure used for evaporating water can be higher than the pressure used for evaporating fuel oil, so that water can be removed first and then the water vapor generated can be condensed with ordinary cold water instead of using cooled cold water. Therefore, sufficient pressure must be maintained in the first step to ensure complete condensation of the water vapor with plain cold water. But once the water in the purified oil has basically evaporated, the pressure can be further reduced to vaporize the fuel oil. Because fuel has a much higher boiling point than water, plain cool water can still be used to condense the fuel vapor and prevent it from entering the vacuum pump.

Generally, in the first step, in order to remove water, decompression is carried out, so that the dirty oil is under the pressure of 400-550mm pump column, and the oil is heated to 40-85°C at the same time. Under these conditions, water will vaporize in the temperature range of 40-80°C. The water vapor can be cooled with plain cool water in a condenser (eg shell and tube) to condense it so that it does not enter the vacuum pump. The temperature of the cooling water should not exceed 40°C, preferably lower than 26°C.

In the second step, the pressure is further reduced to vaporize the fuel, and the ultimate pressure value after decompression depends to a certain extent on the types of fuel impurities in the lubricating oil. If the fuel impurity is gasoline, it can be vaporized under the conditions of 35-80°C and 400-600mm Hg. But the boiling point of diesel oil is much higher, which is 250-300°C under normal pressure. Therefore, the pressure must be reduced to a low level to ensure that it vaporizes in the temperature range of 110-125°C, which is lower than the temperature at which the lubricating oil and/or its additives decompose significantly. Therefore, the pressure should be controlled at or below 5 mm Hg, preferably close to 1 mm Hg. Under this pressure, diesel will vaporize at a temperature of 105-115°C. Therefore, the processed dirty oil must be heated to 115-125°C to ensure the vaporization of diesel oil, and at the same time, it must be ensured that the temperature will not be too high to prevent the decomposition of lubricating oil and its additives.

According to another feature of the present invention, we also found that the dirty oil needs to maintain temperature during the whole flashing process, so as to achieve the best vaporization and separation effect. For this reason, heating baffles and (or) heating plates can be installed in the dirty oil flash tank to continuously provide heat for the atomized dirty oil as water or fuel vaporizes and absorbs heat.

In order to ensure complete removal of water and fuel oil during evaporation, it is generally necessary to continuously circulate dirty oil through a flash tank where water vapor and fuel vapor are flashed off. This means that the dirty oil passing through the flash tank must be pumped back to the sump to maintain circulation. This requires a pump that can return the lubricating oil to the oil collection container at an extremely low flash pressure (as low as 1 mm Hg) in the final step of removing the fuel. To achieve this, in a preferred embodiment of the invention, a mechanical pump is used in series with a Venturi pump. The outlet of the mechanical pump is divided into two streams; one stream provides oil flow back to the oil collection container to maintain circulation, and the other stream provides the oil used as the operating medium for the Venturi pump to prevent the oil from being stolen. Α?

Describe the present invention with embodiment below, can refer to accompanying drawing. in:

Figure 1 is a flow chart of removing fuel oil from dirty oil.

Fig. 2 is the general process of dirty oil purification including the parts shown in Fig. 1 .

Figure 3 is an enlarged view of the flash tank internals that vaporize fuel and water.

Look at Figure 2 first. To collect the dirty oil in the oil tank 10, it is generally necessary to test the type and content of impurities. After collecting the required amount of waste oil for one operation, the pump 12 is used to transport the oil to the settling tank 14 . In the settling tank, keep the temperature constant and add a coagulant from the inlet pipe 16 to mix it with the dirty oil, and then leave it for a period of time to make it divide into two layers. The upper layer is clear oil and the lower layer is sludge. As long as the gravity settling time is sufficient, or centrifugation and (or) filtration and other means can be used, the purpose of separation can be achieved in the settling tank 14 . Sludge is removed from pipe 18 . Since the sludge contains a high proportion of carbon fines, it is often used in the manufacture of inks, while cleaning oil is drawn from pipe 20 into a clean oil tank 22.

This method is well known and used. It is generally described in British Patent Application No. 7905434, the entirety of which is incorporated herein by reference.

The coagulant can be an aqueous mixture containing amino compounds with hydroxyl groups and single or multiple oxygen groups. This is described in the UK patent mentioned above.

However, this method cannot remove a large amount of fuel impurities in waste lubricating oil. Therefore, according to the present invention, the dirty oil sent to the settling tank is treated in the vacuum dehydration step 24 to remove water and fuel oil before adding the coagulant. The vacuum dehydration process 24 is shown in Fig. 1 for details.

In Fig. 1, the pump 28 pumps the dirty oil from the settling tank 14 to the flash tank 30 through the pipe 26, and then is pumped out by the pump 32 and pumped back to the settling tank 14 through the pipeline 34. Before the dirty oil enters the flash tank 30, it is heated to an appropriate temperature by a heater 38 containing a heating element 40 to vaporize the fuel oil and water.

In the flash tank 30, the hot oil is sprayed into a mist through nozzles 42, which can create a large surface area to facilitate the vaporization of water and/or fuel oil. Vapors flashed off in tank 30 exit through line 44 , while oil collected at the bottom of tank 30 is pumped by pump unit 32 through line 46 .

Shown in Fig. 3, is the part that maintains the oil temperature in the tank 30. Rely on it to avoid re-condensation of water and fuel vapors. Initially, the liquid droplets ejected from the nozzles 42 gather on the surfaces of many concentric cylindrical baffles 50, these baffles are separated by partitions 51, and their surface temperature is maintained by each heating coil 52, and the heat medium in the heating coil is A portion of the process medium from the heater 38 . The oil collected on the baffle 50 flows down the surface in the form of a film, and then collects in the lower part of the tank 30 .

The vapor evaporated from the flash enters the shell-and-tube condenser 60, and there is cooling water in the condenser to condense it, and the condensate tank 62 collects the condensate.

The flash tank 30 is evacuated by a vacuum pump 64, and a filter 66 is installed before the pump in order to protect the pump and prevent solid particles that may be brought by the steam from entering. The condensate tank is equipped with a vent valve 67, which can control the degree of vacuum. With the purge valve fully closed, pump 64 will create a high vacuum in tank 30, condenser 60 and tank 62.

Due to the extremely low pressure in the tank 30 during processing, the pump unit 32 must be able to pump the oil from the tank 30 and pump it back into the settling tank 14 . The pump unit includes a mechanical pump 68 having a discharge port 70 . The pipe 70 is divided into two streams: one stream returns the oil to the settling tank 14 through the line 34, and the other stream 72 forms a circuit through which oil circulates to drive a jet pump, i.e. a Venturi pump 74. The suction port of the pump 74 is connected with the pipe 46, so it improves the pumping capacity of the pump 68, so that the pump unit 32 can pump oil from the tank 30 under extremely low pressure.

In operation, dirty oil is collected in the oil tank 10 and when a sufficient amount is collected, it is sent by the pump 12 to the settling tank 14 . The oil in tank 14 is then circulated through vacuum dehydration unit 24 .

Start vacuum pump 64 and pressure is controlled at about 600mm Hg with purge valve 67. Pump 28 then circulates the oil through tube 26 into the device. Heater 38 heats the oil, which enters tank 30 to flash. The oil droplets collected by the baffle are pumped out from the bottom of the tank 30 by the pump unit 32 and returned to the settling tank 14 through the pipeline 34 .

In heater 38 the oil is heated to about 80°C and in tank 30 this temperature is maintained by heating tubes 52 and coils 56 . Under the pressure of 600mm Hg, the water in the oil vaporizes and enters the condenser 60 through the outlet 44 to condense and collect in the tank 62. The vaporized water is completely condensed by the cooling water in the condenser. The temperature of the cooling water can be room temperature, for example, up to about 35° C., and it is not necessary to use cooled water. Therefore, water vapor will not enter the vacuum pump and make the vacuum pump go to α?

After the oil circulates for a period of time, all the water has been removed substantially, the air release valve 67 can be closed, and the pressure is gradually reduced, so that the fuel oil in the dirty oil is vaporized in the flash tank. In the case of diesel fuel, if the temperature is to be controlled below about 115°C in order to avoid the decomposition of lubricating oil and/or its additives, then the pressure should not exceed 5mm Hg, preferably about 1mm Hg or less . In this way, the vacuum pump will gradually reduce the pressure in the tank 30 to around 1 mm Hg. At this time, the diesel oil in the lubricating oil will be vaporized, condensed in the condenser 60, and collected in the condensate tank 62.

The dirty oil will circulate as above until all water and fuel has been removed. Then stop the pump, add the coagulant from the pipe 16, make it mix with the waste oil, and precipitate the solid impurities. Thereafter, clean oil is sent via line 20 to clean oil tank 22, while sludge is removed from line 18. The decontaminated oil may be used alone or, if desired, blended with fresh oil and/or additives to restore its lubricating properties to the range required for any particular application.

Claims (11)

1. A method of purifying lubricating oil and dirty oil, the method comprises first heating the dirty oil, but must be lower than the temperature that will cause significant decomposition of the lubricating oil and additives, and then decompressing and flashing the dirty oil to remove basically all the condensation The water, then, is flashed under reduced pressure to remove condensed fuel oil impurities while still keeping the oil temperature below the point at which the lubricating oil will decompose significantly, and the slop oil is then treated with a coagulant to make fine particles of insoluble matter and submicron flocculation, and finally, the purified oil is separated from solid impurities and coagulants for reuse. 2. The method as claimed in claim 1, wherein the pressure on the dirty oil is 400-550mm Hg when the condensed water is removed by flash evaporation, and the oil temperature is kept in the range of 40-85°C. 3. The method as claimed in claim 2, wherein the flashed water vapor is condensed with cooling water not higher than 26°C. 4. The method according to any one of the preceding claims, wherein the lubricating oil contains gasoline impurities, and the vaporization temperature of the fuel oil is 35-85°C, and the corresponding pressure is 400-600mm Hg. 5. The method according to any one of claims 1 to 3, wherein the lubricating oil contains diesel impurities, and the vaporization temperature of the fuel oil is 110-125°C, and the pressure is 5 mm Hg or less. 6. The method of claim 5, wherein the pressure is about 1 mm Hg and the temperature is 105-115°C. 7. The method according to any one of the above claims, wherein the waste oil is heated to a temperature range of 110-125°C, which can not only ensure the vaporization of the fuel oil, but also prevent the decomposition of the lubricating oil and its additives. 8. The method according to any one of the above claims, wherein during the flashing process, the method of maintaining the temperature of the dirty oil is to install a heating baffle and (or) a heating plate in the flashing tank to supplement the water and The heat absorbed by fuel when it vaporizes. 9. A method as claimed in any one of the preceding claims, wherein hot dirty oil is continuously circulated through a flash tank to vaporize water and fuel oil. 10. The method according to claim 9, wherein the waste oil is circulated by a pump group consisting of a mechanical pump and a Venturi pump in series, and the mechanical pump provides an oil flow to circulate through the Venturi pump, resulting in very low The suction pressure of the pump group improves the oil pumping ability from the flash tank. The outlet of the mechanical pump is divided into two streams: one stream returns part of the oil to the oil collection container, so that the dirty oil can continuously circulate through the flash tank , and the other is supplied to the Venturi pump as the operating medium. 11. Lubricating oil purified by a method as claimed in any one of the preceding claims.

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