WO2008032129A1

WO2008032129A1 - Improved method for purifying contaminated oils

Info

Publication number: WO2008032129A1
Application number: PCT/HU2006/000075
Authority: WO
Inventors: Tamás DÁVID; József PASINSZKI
Original assignee: David Tamas; Pasinszki Jozsef
Priority date: 2006-09-14
Filing date: 2006-09-14
Publication date: 2008-03-20

Abstract

The object of the invention is an improved method for purifying contaminated oils, primarily hydrocarbon, polyether, or silicon oils, comprising the steps of treating the contaminated oil after dehydration and flash-point adjustment at a given temperature for a given duration, eliminating the foaming tendency of oil under treatment, the treatment being carried out applying amine group-containing alkaline complexing compounds; separating after the treatment the oily phase from the aqueous phase utilizing an inertial- force apparatus and/or applying a distillation apparatus; and separating contaminants bonded to the adsorbent by means of filtering. Oils purified with the application of the method can be used without any further treatment as fuel for conventional furnaces, or can be applied as feedstock in other technological processes.

Description

Improved method for purifying contaminated oils

The invention relates to an improved method for purifying contaminated oils.

Description of prior art

The treatment of used, contaminated lubricating oils (collectively referred to as spent oils or used oils) has been a constant problem for both users and lubricant distributors and thus it has also been a major concern to make these waste products suitable for re-use through purification.

The majority of known methods offer solutions to the above problem by producing lubricant feedstock from used oils by means of purification, from which reusable lubricating oil can be obtained with further purification and treatment. A common trait of these solutions is that purification is carried out primarily with the application of conventional refinery methods (by means of fractional or continuous distillation

<rectification> in a fractionating tower), or by combining these conventional methods with others, for instance with alkaline or acidic treatment for removing contaminants, cracking, or the combination of these. (See the following applications and patents: US 08/925279,

DE 19852007, US 5527449, WO 9921945, FR 2703067, GB 707606, EP 574272, and HU 213650 / IT MI92A002271.)

The main drawback of the above methods is that distillation has a significant amount of residue (in certain cases above 30%) that has to be treated as a waste product, which may pose serious problems. Methods with a smaller amount of residue, on the other hand, are expensive either because of the need for costly additives or their high energy demand. The method disclosed in international patent application WO 9100329 is free from the above mentioned disadvantages, but requires a high amount of chemicals, is complicated, and has high energy demand due to the applied treatment temperature (320 °C-420 ⁰C).

A further disadvantage is the fluctuating quality of spent lubricating oils collected from various sources, which makes it difficult to produce sustained-quality lubricating oil from spent oil.

It is also a problem that the methods described above (the treatment of used oil with distillation/rectification) can be implemented predominantly on an industrial scale, in oil refineries, which requires the centralization of spent oil collection and makes the method more expensive.

A well-definable solution was provided for eliminating the above drawbacks by patent application HU P 0105022 which discloses a method for the purification of

5 contaminated hydrocarbon or poly ether oils. The aim of the method according to the patent application HU P 0105022 was the purification of waste oils to an extent that they would become suitable to be used for energetical purposes in conventional firing apparatuses, or to be applied as feedstock in other technological processes. The invention was based, on the one hand, on the recognition that zinc and aluminium compounds and halogenated

.0 aliphatic hydrocarbons (making up the greater part of contaminants) are decomposable by alkaline agents, and the decomposition products can be extracted into an aqueous phase.

The other part of the inventive recognition was that extracted substances may be bound to a suitable adsorbent and water may be distilled from the bound contaminants without their solving back into the oily phase, and thus they can be filtered as mechanical contaminants

L 5 together with worn particles and other adsorbed contaminants.

The method disclosed in patent application HU P 0105022 was significantly easier to apply industrially than prior art solutions, and an actual apparatus was built for carrying out the inventive method after the priority application was filed. In the course of real- world tests performed for implementing the method it has turned out that both the method and the

20 apparatus possesses hitherto unrealized possibilities for improvement.

The method and apparatus described in detail in patent application HU P 0105022 has the following disadvantages:

• The chief drawback of the method is the foaming tendency of the spent oil under treatment, which posed serious technological difficulties in the technological phase 5 of driving out unnecessary water and during the removal of the ammonia solution functioning as treatment agent.

• Another unfavourable characteristics of the method was that it comprises two steps where water or the aqueous treatment agent is removed via distillation. This solution requires more energy and longer cycle times than what is absolutely 0 necessary.

• A further disadvantage concerns the operability of the apparatus implementing the method and the ability to keep reaction conditions (primarily pressure conditions) within the confines of safe operation. These may seem simple engineering problems; but an engineering solution to them would significantly increase costs and would deteriorate the industrial applicability of the method. Thus, the question had to be addressed in an entirely different manner.

Definition of the inventive objective

The objective set to the present invention is to improve the method and the apparatus implementing the method according to the patent application HU P 0105022 such that

- the foaming tendency which disturbed the process is eliminated; - the energy demand of the method is lowered;

- the controllability of the method is improved;

- a safer, faster and more economical method is provided;

- the sensitivity of the method to fluctuations in the quality and quantity of collected used oils is lowered.

Accomplishment of the inventive objective

The method and apparatus according to the invention is the result of the simultaneous application of multiple recognitions.

The known method according to patent application HU P 0105022 was based on the recognition that contaminants dissolved into the oil during use (zinc and aluminium compounds and halogenated aliphatic hydrocarbons) are decomposable, under suitable reaction conditions, by means of alkaline treatment and the simultaneous application of adsorbents, and can be extracted together with worn particles from the oily phase in such a way that it is not necessary to separate the oily and aqueous phases, and thus the process can be accelerated without producing waste water. Extracted contaminants may be bound to a suitable adsorbent, preferably diatomaceous earth or zeolite, and water may be distilled from the bound contaminants without their solving back into the oily phase, and thus they can be filtered out as mechanical contaminants together with worn particles and other adsorbed contaminants. However, it has since turned out that not all alkaline solutions are suitable for performing the above described role.

The inventive improved method is based on the recognition that there exists a group of alkaline compounds that can be applied for transforming the contaminants dissolved into the oil during use (zinc and aluminium compounds, halogenated aliphatic hydrocarbons) - A -

into water-soluble compounds, thereby providing that the transformed contaminants can be most advantageously extracted from the oily phase. This group of compounds is the group of amine group-containing alkaline complexing agents. The group contains compounds with higher and lower volatility. It was known at the time of designing our previous method that decomposed contaminants extracted into an aqueous phase may be bound by means of a suitable adsorbent, preferably of diatomaceous earth or zeolite, hi addition to that, while working on the present invention we have recognised that bentonite and activated carbon, as well as mixtures of the above adsorbents may also be applied to the same purpose. An essential component of the method is that water may be removed from the bound contaminants without their solving back into the oily phase, and thus they can be filtered out or separated as mechanical contaminants together with worn particles and other adsorbed contaminants.

The improved method according to the present invention is based on the further recognition that after a chemical treatment performed as specified herein, the separation of oily and aqueous phases can be carried out applying an apparatus based on inertial forces, to the advantageous effect that thermal energy demand can be lowered and no unmanageable foaming occurs during the removal of water by distillation.

According to the essential steps of the inventive improved method the spent oil to be purified is first pumped into a reactor through an inertial separator means after preheating it in a heat exchanger, with the addition of 0.1-4 parts by mass, preferably 1 part by mass of adsorbent. Water discharged from the inertial separator means is treated as dangerous waste. In the following step the temperature of the - now dehydrated and preheated - oil to be purified is set to a value between 100 ⁰C and 200 ⁰C, preferably to 150 ⁰C. In order to adjust the flash point, light hydrocarbons are distilled off from the oil fed into the pressurizable treatment vessel, subsequently adding the aqeous solution of

0.1-15 parts by mass, preferably 1.5 parts by mass of concentrated reagent to the oil, and performing a treatment of intensive phase contacting for a duration of 20-60 minutes, preferably 30 minutes. In the final step, the treated oil is passed through another inertial separator means, a filter, and a heat exchanger, where reagent residues and contaminants still present in it are removed.

Brief description of the drawings

Fig. 1 shows the flow chart of the improved method according to the invention, and Fig. 2 shows the functional scheme of the apparatus carrying out the inventive improved method.

The inventive method is described in more detail with reference to Figs. 1 and 2. The flow chart shown in Fig. 1 and the functional scheme of Fig. 2 illustrate a preferred way of implementing the invention.

100 parts by mass of spent oil A₁ (a measure calculated with respect to water-free state, so the total measure would be 100 parts by mass of spent oil + X parts by mass of water) is preheated in a heat exchanger 1 and is passed through a continuous centrifuge 2 into a buffer tank 4. The separated water A₂ (X parts by mass) is discharged through a water treatment unit. With the application of a pump 6 the spent oil A₃ is then pumped to a pressurizable treatment vessel 10 that has been previously evacuated by means of a compressor 12 and has been filled with inert gas. Meanwhile, 0.1-4 parts by mass (preferably 1 part by mass) of suitably activated adsorbent B is mixed to the oil. Next, with continuous, intensive stirring the oil is heated to the treatment temperature (between 100 °C and 200 ⁰C) in the sealed pressurizable treatment vessel 10 and after the desired temperature has been reached, light hydrocarbons B₂ are distilled off. The condensate (light hydrocarbons) is accumulated in a condensate container 15 until condensate dripping is finished. The condensate is treated as dangerous waste. Subsequently, 0.2-30 parts by mass of 50% monoethanolaniine solution C₁ (consisting of 0.1-15 parts by mass of concentrated reagent + the same amount of water) is added to the oil B₃ to be purified, with intensive, large-surface phase contacting being carried out for 20-60 minutes (e.g. by means of stirring or ultrasonic energy).

After the treatment is finished, the contents C₂ of the pressurizable treatment vessel 10 are passed through a centrifugal filter 18. The separated reagent solution C₂ is collected in a reagent container 17, passing the purified oily phase D₁ through heat exchanger 1, thereby cooling it (and preheating the next batch at the same time), with said oily phase D₁ being discharged as the end product of the process. If needed, the sludge D₃ is removed from the centrifugal filter 18 and is treated as dangerous waste.

A preferred way of carrying out the invention is described by Example 1. Example 1.

Our invention will now be illustrated by an example consisting of steps A-D, without limiting the scope of protection to the presented example. The process according to the method is illustrated in Fig. 1, with Fig. 2 showing the functional scheme of the apparatus implementing the method. Step A) Dehydration

Before starting the process, the pressurizable treatment vessel 10 is evacuated by means of compressor 12 and is filled up with N₂ to prevent conditions potentially leading to inflammation or explosion. By means of preliminary laboratory analysis, the water and contaminant content of the spent oil A₁ to be purified is establihsed. Pump 3 is applied to pass 100 parts by mass (calculated with respect to water-free state) of spent oil A₃ into the buffer tank 4 through continuous centrifuge 2, the oil being preheated in heat exchanger 1. (At the same time, the previous batch C₁-D₂, having been treated in the pressurizable treatment vessel 10, is discharged through heat exchanger 1.) Water A₂ separated in centrifuge 2 is discharged through a water treatment unit. Flow rates of in-fed liquids are measured with flowmeters. The buffer tank 4 is vented through adsorbent (activated carbon filter) 5. Step B) Flash point adjustment

Next, pump 6 is applied to pump the spent oil A₃ into the pressurizable treatment vessel 10, with the simultaneous addition of preferably 1 part by mass of suitably activated zeolite B₁ through adsorbent feed means 7 to the oil. Then, the oil pumped into the sealed pressurizable treatment vessel 10 is heated with continuous, intensive stirring to preferably 150 °C and, after the desired temperature has been reached, light hydrocarbons B₂ are distilled off to a condensate container 15. The condensate is treated as dangerous waste (anticipated quantity of condensate is 0-2 parts by mass per batch). The product B₃ of this step (the adjusted flash-pont spent oil) remains in the pressurizable treatment vessel 10.

Step C) Chemical treatment, decomposing contaminants Next, with the application of pump 16, preferably 3 parts by mass of 50% monoethanolamine solution C₃ is retrieved from the reagent container 17 and is added to the oil B₃ to be treated. The oil to be treated is intensively stirred for preferably 30 minutes, while keeping it at the treatment temperature. The pressurizable treatment vessel 10 is protected by a safety vent 9 venting into a safety vessel 8 in case of overpressure. The product C₂ of this technological step will be removed from the pressurizable treatment vessel 10 in the next step (step D).

Step D) Removal of the reagent and contaminants

After the treatment is finished, the chemically treated oil C₂ (still at a temperature of approximately 150 °C) is removed from the pressurizable treatment vessel 10 under the pressure of the vessel and assisted by pump 19, with the treated oil being passed through a centrifugal filter 18, the oily phase Di being separated from the aqueous phase D₂ and the now mechanically filterable contaminants D₃ bound to the adsorbent. The separated reagent solution D₂ is fed into reagent container 17, with the purified oily phase D₁ being discharged as an end product through heat exchanger 1 simultaneously with the in-feed of the next batch. The sludge D₃ is removed from the centrifugal filter 18 if so required and is treated as dangerous waste. Thus, the end product obtained from 100 parts by mass of spent oil (calculated for water-free mass) is 96-99 parts by mass of purified oil that can be directly used as heating oil or applied as feedstock oil for other technological processes; with 2-4 parts by mass of filter sludge and 0-2 parts by mass of condensated light hydrocarbons and water being produced as by-products, which should be purified or treated as dangerous waste.

Industrial applicability of the invention

The improved method according to the invention can be implemented easier, in a simpler and cheaper manner than known solutions for purifying and reusing contaminated hydrocarbon, polyether or silicon oils. An important factor of industrial applicability is that oil purification is carried out by means of a simple chemical treatment method that renders the contaminants contained in used oils mechanically filterable. The method improved according to our invention has eliminated the foaming tendency that caused major problems in our previous method.

Advantageous features of the invention compared to prior art The inventive improved method and the related apparatus has the following advantages over prior art:

• energy demand has been lowered with respect to our previous method,

• the method is capable of removing worn particles, zinc and aluminium compounds, and halogenated aliphatic hydrocarbons from contaminated oils without the production of technological wastewater and with few waste products,

• process control is easier due to the lack of foaming, and thus

• apparatus safety has been significantly increased, and

• industrial applicability has been improved. List of reference numerals

1 heat exchanger

2 continuous centrifuge 3 pump

4 buffer tank

5 adsorbent (activated carbon filter)

6 pump

7 adsorbent feed means 8 safety vent

9 safety vessel

10 pressurizable treatment vessel

11 cooler

12 compressor 13 safety vent

14 adsorbent (activated carbon filter)

15 condensate container

16 pump

17 reagent container 18 centrifugal filter

19 pump

A₁ spent oil

A₂ water

A₃ dehydrated spent oil (product of step A) B₁ adsorbent

B₂ discharged vapours (light hydrocarbons)

B₃ adjusted flash-point spent oil (product of step B)

C₁ aqueous reagent solution

C₂ chemically treated spent oil (product of step C) D₁ oily phase (purified oil, end product of process)

D₂ aqueous phase (re-usable reagent solution)

D₃ sludge

Claims

1. Improved method for purifying contaminated hydrocarbon, polyether, or silicon oils under reaction conditions determined by given temperature, pressure, and duration values, characterised by that chemical treatment is carried out in a heatable, inertized pressurizable treatment vessel (10) utilizing amine group-containing alkaline compounds, the method comprising the steps of removing water (A₂) from the spent oil (A₁) to be purified, feeding the substance to be purified (A₃) into the pressurizable treatment vessel (10) with the simultaneous addition of an adsorbent (B₁), raising the temperature of the substance to be purified (A₃) to the range between 100 °C and 200 °C, distilling off light hydrocarbons

(B₂) to set the flash point of the substance, mixing the amine group-containing alkaline reagent (D₁) to the oil, contacting the oily and aqueous phases along a substantially large surface, and subsequently separating the oil (D₁), the reagent (D₂), and contaminants (D₃) rendered mechanically filterable during previous steps.

2. The method according to Claim 1, characterised by that the treatment by amine group- containing alkaline complexing compounds (C₁) is carried out utilizing 0.1-15 parts by mass, preferably 1.5 parts by mass, of a reagent substance (C₁).

3. The method according to Claims 1 or 2, characterised by that 0.1-4 parts by mass of zeolite or diatomaceous earth or bentonite or activated carbon or a mixture thereof is applied as adsorbent (B₁).

4. The method according to any one of Claims 1-3, characterised by that chemical treatment is carried out at a temperature between 100 °C and 200 ⁰C, preferably at 150 °C.

5. The method according to any one of Claims 1-4, characterised by that chemical treatment is carried out during intensive phase contacting with a duration of 20-60 minutes, preferably 30 minutes.

6. The method according to any one of Claims 1-5, characterised by that after the chemical treatment an apparatus applying inertial forces (18) and/or a distillation apparatus and/or a filter is utilized for separating the oily (D₁), aqueous (D₂), and solid (D₃) phases.

7. The method according to any one of Claims 1-6, characterised by that purified oil (D₁) obtained as the end product of the method can be used without any further treatment as "artificial heating oil" for fuelling conventional furnaces or can be applied as feedstock in other technological processes.