WO2019098950A1

WO2019098950A1 - Improvement of the sotulub method for regenerating used oils while observing different environmental aspects

Info

Publication number: WO2019098950A1
Application number: PCT/TN2018/000005
Authority: WO
Inventors: Ali LOUDHABACHI; Sofienne BEN CHAABAN; Ikbel EIGLAOUI; Salah CHIBANI; Rihab BOUHDIDA
Original assignee: Société Tunisienne De Lubrifiants (Sotulub)
Priority date: 2017-11-20
Filing date: 2018-11-06
Publication date: 2019-05-23
Also published as: TN2017000484A1

Abstract

The present invention concerns the improvement of the method for regenerating used lubricating oils while observing the various environmental aspects. This document specifies the improvement actions carried out in order to increase recovery levels with the actions taken to treat the different waste matter generated during the various steps of the method. According to the invention, the installation of a second evaporator coupled to the fractionating column, and the appropriate and proportional addition, with respect to the feedstock, of a strong base after preheating, and the use of materials resistant to chemical corrosion, have had the effect of maintaining the stability and continuous operation of the production unit and significantly improving the recovery level in terms of finished products. These improvements have allowed recovery levels, which averaged 84% with the previous method, to be increased to 95% with the novel method. This improvement results in a substantial increase in the yield and quality of the finished products. This improvement has also allowed the range of used oils to be treated to be expanded. Moreover, the gases generated during the method that are essentially constituted by volatile organic compounds undergo flaring or treatment in a biofilter. The stripped water is decontaminated in an aerobic membrane bioreactor in the presence of a microbial consortium capable of degrading the phenolic compounds and the hydrocarbons.

Description

IMPROVING THE SOTULUB PROCESS FOR REGENERATING USED OILS WITH RESPECT TO DIFFERENT ENVIRONMENTAL ASPECTS

1. Technical field of the invention

The present invention relates to the improvement of the regeneration process of used lubricating oils as well as the actions recommended for treating the different discharges generated during the different steps of the process. More specifically, the present invention specifies the improvement actions taken to increase and the recovery rates and the depollution of the different discharges generated during this process.

2. State of the prior art

The present invention relates to a method and an installation for the regeneration of used lubricating oils having a low content of fuel, fatty acids and chlorinated products. The used lubricating oils are subjected to the successive stages in the order: addition of strong bases in aqueous solution at the rate of 0.5 to 3% pure base in mass of used oils, dehydration and extraction of light hydrocarbons, extraction and recovery of gas oil (stripping), extraction of impurities. According to the invention, a complementary addition of a strong base in aqueous solution due to 0.1 to 1% of pure base mass of waste oil is carried out after the dehydration step and extraction of light hydrocarbons.

The used lubricating oils thus treated are freed from their impurities by distillation.

3. Presentation of the invention

The present invention relates to improving the regeneration process of used lubricating oils while respecting the various environmental aspects.

This document specifies the improvement actions carried out to increase the recovery rates with the actions taken to treat the different discharges generated during the different stages of the process.

According to the invention, the installation of a second evaporator coupled to the fractionation column, as well as the adequate and proportional addition to the load of a strong base after preheating and the use of corrosion resistant materials. have resulted in maintaining the stability and continuous running of the production unit and significantly improving the recovery rate of the finished product. These improvements have increased the recovery rate by an average of 84% when using the old 95% process under the new process.

On the other hand, the gases generated during the process and which consist essentially of volatile organic compounds undergo flaring or treatment in a biofilter. On the other hand, the stripped waters are decontaminated in an aerobic membrane biological reactor in the presence of a microbial consortium capable of the degradation of phenolic compounds and hydrocarbons. 4. Descriptions of the figures

Figure 1: the different stages of the process of regeneration of waste oils.

Figure 2: the different stages of the physical separation and pretreatment of effluents from the process (gas and process water).

Figure 3: the different stages of the biological treatment plant for stripped water.

5. Detailed description

Referring to the process of invention registered under number TN 1997/189 in Tunisia and internationally under the number 96 15380, this document specifies the improvement actions taken to increase the recovery rates while respecting the environmental aspects. .

The embodiment of the invention will be described below, by way of non-limiting example, with reference to the following schemes in which:

• Figure 1 shows the different stages of the regeneration process of used oils.

• Figure 2: represents the different stages of the physical separation and the pretreatment of the effluents (gas and process water).

• Figure 3 shows the different stages of the biological treatment in the stripped water treatment plant.

Used oils collected can have various origins. These may be engine oils, gear oils, hydraulic oils, turbine oils, etc. Upon receipt of these oils at the regeneration unit, their suitability for treatment is controlled. Indeed, the regeneration process of this invention is essentially the elimination of light components, such as gasoline, gas oil and water, but does not eliminate some components as heavy as the oils themselves. It could be, for example, fuel whose disposal or treatment could be obtained only by a complete refining process. Excessive chlorine content of the mixtures may be likely to cause premature wear of the installation. Collected oils containing too high percentage of fuel, fatty acids or chlorine are removed. The selection criteria can be quoted as follows:

CHLOR TEST: Which allows to detect the presence of chlorides. A copper wire dipped in used oil is presented to the flame. A greenish flame indicates the presence of chlorides.

DROP TEST: Used to detect the presence of fuel. A drop of oil is deposited on a chromatographic paper. A concentric spot with a yellowish halo indicates the presence of fuel.

FAT TEST: Detects the presence of fatty acids in oils. 2 ml of used oil are heated in the presence of sodium hydroxide pellets: when the oil freezes, after cooling, it means that fatty acids are present. As shown in Figure 1, used oils after selection and storage in the tank (2), are pumped and preheated through a train of exchangers (5a; 3) by the recovery of energy from the outgoing products ( 11; 27). Subsequently, a strong base in aqueous solution (4b) adequate and proportional to the load at a rate of 0.7 to 1% (anhydrous weight / oils) is introduced at point (5b). These oils then feed a balloon (6) place of extraction of water and light essences by flash (relaxation). In this flask, the evaporation of water and light hydrocarbons is produced by expansion. The water and the light hydrocarbons (7a) are conveyed to the point (7b) of Figure 2. The dehydrated oils then pass to the stripping column of the gas oil (8). The extraction of the gas oil is carried out by distillation under partial vacuum. The extracted gas oil is withdrawn at point (8a) while the gases (9a) are conveyed to the vacuum system (SV1: Figure 2).

The stripped oil is then pumped to a vacuum distillation column (10) coupled to a thin film evaporator (13). In this column, the distillate (s) can be separated at different levels depending on the number of cuts desired. The bottom of the column flows towards an evaporator which allows a maximum of exhaustion while avoiding the clogging and the clogging of the equipments.

The impurities resulting from the reaction and distillation are withdrawn and sent to the storage (15) for possible upgrading as fuel. The gases withdrawn (9b) at the column head (10) are sent to the vacuum system (S V2: "Figure 2). The distillate (s) produced from the column undergo accelerated oxidation in the contactor (22) at a temperature between 130 and 160 ° C. Subsequently, this distillate (s) are preheated in a preheater (25) to a temperature between 215 and 225 ° C.

The oxidized and preheated distillate (s) are injection-added with a suitable and proportional aqueous solution (23b) in a proportion of 0.2 to 0.4% by using suitable corrosion-resistant materials. chemical then introduced to point (24) to the high vacuum fractionation column (20) coupled to a thin film evaporator

(26). In this column, the sections can be separated at different levels according to the desired qualities. We achieved good results by producing a light cut 150 N

(27) on the one hand, and a 350N cut (28) on the other hand.

The bottom of the evaporator (29) rich in heavy oil is recirculated for re-exhaustion to the balloon (6). This operation allowed us to avoid any loss of oils in the tailings, which contributed to the increase in the recovery rate. The gases withdrawn (9c) at the top of the fractionation column (20) are sent to the vacuum system (SV3: FIG. 2).

As shown in Figure 2, the gases (9A, 9B and 9C) respectively from the columns (8, 10 and 20) are sucked by vacuum systems SV1, SV2 and SV3. While the gases (water vapor + light hydrocarbons) from the flask (6) are condensed and separated in a condenser (7B). The incondensable gases are flared (T). All condensates are accumulated in the flask (B1) where there will be physical separation of the oily phase, and may be mixed and used as fuel.

The incondensable gases are sent simultaneously to the balloons B3 and B4. The gases from the balloon B4 are sent to the torch and the condensates will be treated with a bio-filter.

The aqueous phase from the flask (B1) is subsequently treated in a steam stripping column (C). In this column (C), the incondensables are sent to a balloon (B2) before being flared. On the other hand, the stripped waters undergo a biological treatment (Figure 3).

The invention therefore more particularly aims to improve the recovery rate for a well-defined product quality. Table 1 shows the evolution of this rate by compared to the previous SOTULUB process. Indeed, this rate has increased on average by 84% when using the old 95% process in application of the new process.

Secondly, this invention takes into account the treatment of water and waste gas from this process by the application ^I. place the following steps:

> Physical separation of water and hydrocarbons.

> Elimination of polluted volatile gases.

> Stripping process water with steam.

> Flaring of the incondensable gases resulting from the different stages of the process.

Biological treatment of stripped waters

The present invention proposes a methodology for treating stripped water from the SOTULUB process (FIG. 3). The method of biological treatment comprises a step of preparing and producing a microbial consortium capable of degradation of hydrocarbons and phenolic compounds. Treatment cycles carried out under optimal conditions and well controlled oxygen transfer result in treated wastewater that complies with the standards in force. In fact, to treat 25 m ³ / d of effluent from Tusine SOTULUB, we installed a ventilated reactor with a total volume of 40 m ³ . This reactor is fed by simple flow from a settler-float which in turn is fed with an adjustable flow lift pump. This reactor functions as a conventional activated sludge system with the addition of a bacterial consortium consisting essentially of the strain Chryseomonas luteola LBPH1 isolated * at the Sfax Biotechnology Center (CBS), harmless to humans, animals and plants. The selection pressure exerted by the hydrocarbons and the phenolic compounds present in the effluent and under the optimal conditions of its growth, the strain Chryseomonas luteola LBPH1 will be majority in the medium. An inoculation reminder by this strain, whenever the kinetics of treatment begin to decrease will maintain an adequate rate of degradation for the production of an effluent in compliance with the standards in force.

The aeration and stirring of the medium are ensured by means of a fine-bubble air diffuser placed at the bottom of the reactor and of a stirring system composed of a variable-speed gear motor of 0- 200 rpm. The temperature inside the reactor is maintained at 30 ° C. by means of circulating water thermostatically in a coil against the internal walls of the reactor. A system of 4 wedges glued to the inner wall of the reactor makes it possible to break the "vortex phenomenon" and to improve the homogenization of the medium. An outer jacket of the reactor with thermal insulation minimizes heat dissipation and saves energy. The coupling of a membrane unit to the reactor in substitution of the secondary settling makes it possible to remedy the problem of the variability of the stripped waters and to obey the standards of rejection even in the case of the high loads in hydrocarbons and in phenolic compounds. Figure 3 illustrates a diagram of an example of a stripped water treatment station without limiting its scope. The station consists essentially of a primary decanter which reduces the suspended solids and floating materials to subsequently feed in continuous mode an aerated biological reactor inoculated with a microbial consortium capable of degradation of phenolic compounds and hydrocarbons. The mixed liquor is subsequently filtered through an outer membrane unit. The concentrated part (retentate) is recycled in the reactor while the treated wastewater (Permeat) is thrown into the public pipelines by checking the quality and compliance with the standards in force.

In this example, the follow-up of the evolution of the different physicochemical parameters of the stripped waters whose composition is illustrated in table 2 made it possible to draw the following conclusions: Substantial reduction of the pollution of stripped waters thus offering water in accordance with the standards of rejection in the public pipelines (pH, COD, BOD5, MES, Nitrogen, Phenols, Hydrocarbons).

Effectiveness of the microbial consortium to release hydrocarbons and phenolic compounds with yields up to 95%.

On the other hand, this invention proposes the application of a biological filter capable of purifying odors released from the different production units. Indeed, the odors released are sucked into a fixed bed reactor inoculated with a consortium capable of oxidation and abatement of the various compounds "SOx, NOx, VOC, CO ...). Adequate humidity with the addition of some nutrients (C, N, P) with the inoculum will allow to achieve high purification efficiencies and therefore to comply with the norm 106. 04.

6. Currently used technique

This technique is currently used in our waste oil regeneration unit.

Table 1: Evolution of the recovery rate compared to the previous version of the process

Table 2: Physico-chemical characterization of stripped waters treated in the example of the station.

Claims

1) A method of regenerating used lubricating oils, wherein the used lubricating oils are subjected, and in the following order, to the following successive treatment steps:

a) Selection of used oils suitable for processing.

b) Heating used oils to be regenerated at a temperature between 120 and 150 ° C.

c) Addition of a strong base in aqueous solution, anhydrous bases, proportionally to the mass of used lubricating oils ranging from 0.7 to 1%. d) Dehydration and elimination of tree species.

e) Extraction and recovery of gas oil (Stripping).

f) Recovery of the distillate.

g) Extraction of impurities (Residues).

h) Oxidation of the distillate

i) Preheating the distillate to a temperature between 215 and 225 ° C.

j) Additional addition of a strong base in adequate aqueous solution and proportionally to the treated feedstock ranging from 0.2 to 0.4%.

(k) Fractionation of distillate into finished product (s)

2) Process for regeneration of waste oils according to claim f, guaranteeing the following qualities

- Maintaining stability and continued running of the production unit

- A noticeable improvement in the recovery rate of finished product (s)

These improvements are due to the following changes:

• The installation of a ^2nd evaporator coupled to the fractionation column.

• Adequate and proportional addition to the load of a strong base in aqueous solution after preheating and using materials resistant to chemical corrosion

3) For by-products

Process for the regeneration of used oils according to claim 1, allowing the recovery as fuels, residues and gas oil from the process.

4) For reject products

a) Process for regeneration of waste oils according to claim 1, recommending a physical pretreatment by stripping, in the first step, liquid and gaseous discharges generated during the process.

b) Process for the regeneration of used oils according to claims 1 and 3 for flaring the gases generated during the process and which consist essentially of volatile organic compounds

c) Process for regeneration of waste oils according to claims 1 and 3 for treating stripped water in an aerobic biological reactor presence of a microbial consortium capable of degradation of phenolic compounds and hydrocarbons.

d) Regeneration process for used oils according to claim 4 c guaranteeing the obtaining of treated wastewater meeting the discharge standards in public pipelines without having to make a pH correction, and opting for the combination a filtration membrane to achieve organic loads exceeding 4 kg COD / m ³ / day.

e) Regeneration process used oils according to claim 1, for the purification of odors released from the different production units and compliance with 106.04 by installing a biofilter inoculated with an appropriate consortium.