RU2777773C1 - Method for regeneration of hydrophobic sorbents - Google Patents

Abstract

FIELD: waste processing.

SUBSTANCE: invention relates to a method for the regeneration of spent hydrophobic sorbents, which provides for desorption and removal of adsorbed petroleum products from the surface of the spent sorbent by heat treatment, followed by the formation of a hydrophobic film on the surface and in the pores of the sorbent, sealing and cooling of the working chamber. The method is characterized by the fact that the heat treatment of the spent sorbent is carried out at a temperature of 400-450°C for 0.5-1.5 hours, the working chamber is sealed after the completion of the heat treatment, cooled with the regenerated sorbent until the temperature is set at 25-30°C and pressure no more than 30 kPa. In this case, the hydrophobization of the spent sorbent occurs in the gas phase of hydrocarbons of petroleum origin, desorbed from its surface as a result of heat treatment and condensed on the cooled surfaces of the working chamber.

EFFECT: simplification of the method, reducing the cost of its implementation by simplifying the hardware design, as well as by carrying out hydrophobization without additional consumption of the hydrophobizer due to the absence of energy consumption for creating excess pressure, for obtaining superheated water vapor, for vacuuming the receiver while increasing the safety of the method and ensuring a higher quality of sorbent regeneration.

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Description

The invention relates to a technology for the regeneration of hydrophobic sorbents, in particular oil sorbents obtained on the basis of porous natural and artificial aluminosilicates, and can be used to restore the properties of hydrophobic sorbents intended for cleaning liquid media and water bodies from oil and oil products.

The growth in the scale of pollution of the aquatic environment by oil and oil products and, accordingly, the growth in the volume of consumption of oil sorbents, has caused the need to increase the efficiency of their use and continues to cause it. Highly effective sorbents with a wide spectrum of action are usually characterized by high cost, therefore, the possibility of their recovery for subsequent repeated use is of no small importance for sorption materials. The existing methods for the regeneration of oil sorbents are varied and depend on the nature of the material of a particular sorbent. High-temperature and low-temperature thermal regeneration, chemical treatment methods, microbiological methods, extraction, etc. find practical application. Inexpensive sorbents that cannot be regenerated can be disposed of, for example, by incineration. However, to prevent the release of toxic substances into the atmosphere during combustion, careful cleaning of the exhaust gases is required. Therefore, the burning of spent sorbents, as well as their disposal, is currently unpopular.

A known method of regeneration of oil-contaminated diatomite related to silicate sorbents (RU 2612722, publ. 13.03.2017), according to which the regeneration of the sorbent is carried out by processing it in a dielectric barrier discharge for 0.5-1.5 minutes in an atmosphere of plasma-forming gas (oxygen ) with constant shaking during the entire processing time. The disadvantages of the known method include the complexity of its hardware design, due to the need to use special equipment to create a discharge and maintain the atmosphere of the plasma gas, special equipment for shaking the container with the material being processed. In addition, when implementing the known method, it is necessary to strictly comply with the rules of increased safety in connection with working with oxygen in a hermetically sealed container. Also, its disadvantage is the impossibility to provide 100% desorption of the oil product from the surface of the spent sorbent for a given limited processing time, and with multiple regeneration, the sorption capacity of the material decreases with each of its cycles.

There is a known method of regeneration of hydrophobically modified perlite used as a sorbent for oil products, the implementation scheme of which is described in the work of Yudakov A.A., Ksenik T.V., Tsybulskaya O.N., Kisel A.A., dedicated to the method of hydrophobization of perlite (Instrumentation and features of producing the oleophilic sorbent on the perlite basis // Procedia Environmental Science, Engineering and Management 2020 Vol 8 No 1 P 103-113). The method described in this paper for the regeneration of a spent sorbent based on perlite involves its firing at a temperature of 500°C in the working chamber of a plant designed for the hydrophobization of perlite. The working chamber with the loaded spent sorbent is sealed, evacuated, and a prepared water repellent (modifier) is fed into it, which, evaporating at high temperature, turns into a gaseous state, while excess pressure is created in the chamber, under the influence of which the water repellent penetrates into the open pores of perlite granules and forms a continuous organic film on their walls. This film is formed due to the processes of chemical and physical adsorption of gaseous hydrocarbon compounds formed from the water repellent during their cooling without depressurization of the working chamber. The disadvantage of the known method is a long processing time, since regeneration includes two stages: sorbent firing to remove adsorbed substances to prepare an open-pore surface for applying a hydrophobic film and re-hydrophobization (modification). In addition, the excess pressure generated in the working chamber requires compliance with increased safety measures and pressure control, which is associated with the need to install a blast valve and, accordingly, with the complexity of the hardware design of the known method.

There is a known method (RU 2708309, publ. 12/05/2019) for the regeneration of a hydrophobic oil sorbent using the installation used to obtain it, using the same technological operations and in the same sequence as in the initial production of the sorbent, with the only difference being that that during regeneration the used oil sorbent serves as a raw material. Since the spent sorbent supplied for regeneration is initially oleophilic and does not contain physicochemically bound moisture, but retains moisture only in open pores, there is no need for its long-term calcination at high temperature. A significant disadvantage is also the need to use additional equipment (volumetric receiver, vacuum pump) and instruments to control the parameters of the regeneration process and ensure the safety of personnel and the environment.

As the closest in technical essence to the proposed method of regeneration of hydrophobic oil sorbent, described in patent RU2708362, publ. 12/05/2019), according to which the hydrophobization chamber with the loaded spent sorbent (porous aluminosilicate material) is evacuated to a residual pressure of 20-30 kPa and the material is processed in an atmosphere of superheated water vapor, raising the temperature to 280-310 ° C and maintaining the pressure in the chamber within atmospheric; maintained at the reached temperature for 20-30 minutes, after which steam is discharged into a pre-evacuated receiver to a residual pressure in the working chamber of 10-15 kPa. Then, a hydrocarbon water repellent in the liquid phase is fed into it at the rate of 0.1-0.3 g per 1 liter of the hydrophobization chamber volume, maintaining the temperature at 350-400°C for 5-20 minutes. Then the heating is turned off, the temperature decrease is monitored, and at 120°C air is let into the chamber.

The disadvantage of the known method is the insufficiently high heating temperature (280-310°C) at the first stage of heat treatment, which, at the specified duration, does not provide effective removal of adsorbed oil products, especially their heavy fractions, from the pores of the sorbent. Insufficiently thorough preparation of the aluminosilicate material for the deposition of a hydrophobic film leads to a decrease in the quality of the regenerated sorbent. In addition, the implementation of the known method requires the use of additional equipment - a volumetric receiver for discharging steam, since for its effective discharge, the volume of the receiver must be comparable to the volume of the working chamber with the regenerated sorbent. The hardware design of the known method should also include a vacuum pump for evacuating the receiver, means of supplying a water repellent (we should also mention its additional consumption) and equipment for controlling the pressure in the chamber at the stages of processing the sorbent with superheated water vapor and a water repellent, which is necessary to comply with safety measures.

The objective of the invention is to create a technically and economically efficient, simple and safe method for the regeneration of spent hydrophobic sorbents of oil and oil products obtained on the basis of porous aluminosilicates.

The technical result of the proposed method is its simplification and cost reduction due to the simplification of hardware design, as well as due to its implementation without additional consumption of a water repellent, without energy costs for processing at excessive pressure, for processing in an atmosphere of superheated water vapor, for vacuuming the receiver, while increasing the safety of the method and ensuring a higher quality of sorbent regeneration.

The specified technical result is achieved by the method of regeneration of the spent hydrophobic aluminosilicate sorbent, which provides for the desorption of adsorbed oil products by heat treatment in the working chamber of the hydrophobization unit, sealing the working chamber, its cooling with the formation of a hydrophobic film on the surface and in the pores of the sorbent, in which, unlike the known, heat treatment the spent sorbent is carried out at a temperature of 400-450°C for 0.5-1.5 hours, while the working chamber is sealed after completion of heat treatment, the processed sorbent is kept in a hermetically sealed working chamber, reducing its temperature to 25-30°C.

The method is carried out as follows.

The spent aluminosilicate sorbent is loaded onto pallets and placed in the working chamber of the hydrophobization unit. Heat treatment is carried out at a temperature of 400-450°C for 0.5-1.5 hours, depending on the chamber load. At the same time, it should be noted that the experimentally selected values of the temperature and time of heat treatment are optimal: in the stated temperature range for the specified time, complete removal of adsorbed oil products from the pores of the sorbent, including their heavy fractions, is ensured. On the other hand, when carrying out the regeneration of the sorbent, there is no need to carry out a longer calcination and use higher temperatures, which are necessary to remove moisture and prepare the surface of the material before applying a hydrophobic coating.

The calcination of aluminosilicate raw materials during primary hydrophobization is necessary so that the physico-mechanically and physico-chemically bound moisture contained in its open pores and capillaries does not prevent the formation of a continuous hydrophobic film during evaporation. In the case of regeneration, the spent sorbent is initially already hydrophobic and does not contain chemically and mechanically bound moisture, but retains only free moisture, which is easily removed during heat treatment at a temperature in the stated range.

Heating of the regenerated sorbent during heat treatment is carried out at atmospheric pressure without sealing the working chamber.

Installation for the regeneration of hydrophobic oil sorbents, in fact, which is a plant for hydrophobization, is schematically shown in the drawing, which shows: 1 - heat treatment chamber (working chamber); 2 - cooled chamber door 1 with a seal; 3 - material to be regenerated (sorbent) located in chamber 1; 4 - process pipe for discharging gasified hydrocarbons; 5 - capacitor; 6 - sensor-smoke detector; 7 - water cooling line; 8 - heaters; 9 - temperature sensor; 10 - pressure sensor.

In order not to create excess pressure in the working chamber 1, the process pipe 4 in its upper part is left open. During the heating process, oil products are desorbed from the surface of the spent sorbent particles. In this case, gasified hydrocarbons are partially discharged through the process pipe 4 into a condenser intended for their collection (not shown in the drawing) and accumulate there for subsequent disposal; they partially condense on the colder surfaces of the chamber: in the nozzle-condenser 5 provided on the rear wall of the working chamber 1, as well as on the inner surface of the cooled door 2 of the working chamber 1. The end of the process of active desorption is fixed using a smoke detector 6.

After that, the chamber is sealed: the process pipe 4 is closed to remove gases. The heating of the chamber 1 is turned off. The chamber is cooled by connecting to the water cooling line 7. Due to the decrease in temperature in the working chamber, more active condensation of the remaining gasified vapors occurs in the condenser 5 and on the door 2 of the chamber. During the cooling process, a slight vacuum is formed in the hermetically sealed chamber 1. The process of lowering the temperature in the chamber 1 is rather slow: 20-25°C per hour. Due to the pressure drop, the formation temperature of the gas phase of hydrocarbons condensed in the working chamber decreases. Therefore, an atmosphere of gasified hydrocarbons is created in the working chamber (a working gas, which consists of a mixture of hydrocarbons formed during the thermal decomposition of long hydrocarbon chains of the hydrophobizator, which was used in the initial production of the sorbent, and the thermal decomposition of the oil sorbed during the purification process.

As a result, a working atmosphere is formed in the working chamber 1 from unsaturated hydrocarbon compounds, which, being in a gaseous state, easily contact with the active surface of the calcined sorbent. With further cooling of the chamber, the working gas penetrating into the open pores and capillaries of the sorbent forms a continuous organic film on the walls of the pores, which is gradually completed during the cooling of the chamber without depressurization. At the end of the cooling process at a temperature in the chamber of 25-30°C, the vacuum is 20-30 kPa.

Thus, in one stage of processing in the working chamber of the hydrophobization unit, it is possible to carry out not only the heat treatment of the spent sorbent by firing, but also its repeated hydrophobization, without additional supply of a hydrophobiser and without creating excess pressure or vacuum. In comparison with the known method, the regeneration process using the proposed method is much faster and easier. The proposed method is cost-effective and, in comparison with the known, more economically advantageous, since its implementation does not require a separate stage of calcining the spent sorbent for desorption of adsorbed oil products, there is no need for additional consumption of a water repellent, and a vacuum pump is not needed to create a vacuum in the working chamber, no equipment is required to control the pressure in the chamber at the stages of processing with superheated water vapor and water repellent.

The proposed method ensures the preservation of the high quality of hydrophobic sorbents, in particular those obtained on the basis of aluminosilicate materials of natural and artificial origin, after their repeated regeneration.

Examples of specific implementation of the method.

The heat treatment of the chamber with the processed sorbent was carried out under the claimed conditions, the cooling was performed at a rate of 20-25°C/hour until the temperature reached 25-30°C.

The quality of regeneration was evaluated by the values of the contact angle, water absorption and sorption capacity in relation to oil products, which were determined by standard methods.

The contact angle was measured by digital processing of a photographic image of a sessile drop obtained using a Nikon D800 camera with a 61 mm macro lens. The image was processed using the KOMPAS-3D program with an error of ±0.1.

Water absorption under static conditions with respect to distilled water was calculated as the ratio of the mass of water contained in the sample to the mass of the dry sample. Samples of the material were immersed in water and removed for measurements at specified intervals.

To determine the sorption capacity for petroleum products, the most appropriate test method has been developed following the recommendations specified in ASTM F726-17 Standard Test Method for Sorbent Performance of Adsorbents for use on Crude Oil and Related Spills. The sorption capacity in g/g was determined as the ratio of the mass of the adsorbed oil product to the mass of the initial sorbent sample taken before testing.

Example 1

3 kg of spent sorbent based on expanded perlite was regenerated, which was loaded onto pallets and placed in the working chamber 1 of the hydrophobization unit. The chamber with the regenerated spent sorbent was heated to a temperature of 400°C and kept at this temperature for half an hour. This time (even with some margin) was enough to remove the oil product from the surface of the sorbent, the smoke detector no longer recorded the exhaust gases from the working chamber 1 of the hydrophobization unit. At the end of the heat treatment, the technological branch pipe 4 for the removal of gases was blocked, the heating of the chamber 1 was turned off, and the water cooling line 7 was connected. The working chamber 1 with the regenerated sorbent was left sealed during cooling until the desired temperature of 30°C was reached. When the specified temperature of 30°C was established in the working chamber 1, a rarefaction was observed in it: the pressure, according to the readings of the pressure vacuum meter, was negative and amounted to 22 kPa.

The regenerated expanded perlite sorbent was unloaded and checked for processing quality. The static contact angle on the surface of a particle of regenerated perlite with a particle size of 5 mm was 122°, the water absorption value was 0.45% for 48 hours, the sorption capacity for diesel fuel was 1.94 g/g for 24 hours.

Example 2

8 kg of spent sorbent based on expanded clay gravel were regenerated, which was placed on pallets in the working chamber 1 of the hydrophobization unit.

Heating was carried out to a temperature of 450°C and kept at the reached temperature for 0.5 hours. At the end of the heat treatment, similarly to example 1, the process pipe 4 was blocked for venting gases, the heating of the working chamber with the material being processed was turned off, and the water cooling line 7 was connected. The working chamber was left sealed and cooled to a temperature of 25°C. At a temperature of 25°C that was established in the chamber, according to the indications of a pressure-vacuum meter, rarefaction was observed in it: the pressure value was 28 kPa.

After unloading, the regenerated expanded clay sorbent was checked for the quality of processing, and the following results were obtained: the static contact angle on the surface of a particle of regenerated expanded clay with a particle size of 20 mm was 125°, the measured water absorption was 0.7% in 48 hours. The sorption capacity for diesel fuel was found to be 0.4 g/g for 24 hours.

Example 3

The spent sorbent was regenerated based on expanded perlite (4.5 kg) at the hydrophobization unit used in examples 1 and 2. After heating to 450°C, the working chamber with the regenerated sorbent was kept at the reached temperature for one and a half hours. Cooling of the sealed working chamber 1 with perlite sorbent was carried out by connecting the water cooling line 7.

After cooling at a temperature of 30° C. established in the chamber, the pressure value was 24 kPa.

The results of checking the quality of regeneration were as follows.

The static contact angle on the surface of a particle of regenerated perlite with a particle size of 5 mm was 126°, the water absorption value was 0.40% for 48 hours, the sorption capacity for diesel fuel was 1.98 g/g for 24 hours.

Example 4

In the working chamber of the hydrophobization unit, 6 kg of spent sorbent based on expanded clay gravel with particles of 20 mm were regenerated. After heating to 400°C, the working chamber with the regenerated sorbent was kept at the indicated temperature for one and a half hours. Then, similarly to the examples described above, the sealed chamber was cooled using the water cooling line 7. After cooling at a temperature of 26°C that was established in the working chamber, the pressure in it was 20 kPa.

After unloading the regenerated sorbent and analyzing the quality of regeneration, the following data were obtained.

The static contact angle on the surface of a particle of regenerated expanded clay with a particle size of 20 mm was 128°, the measured water absorption was 0.7% in 48 hours. The sorption capacity for diesel fuel was 0.45 g/g for 24 hours.

The proposed method provides effective regeneration of hydrophobic sorbents based on silicates with the restoration of their original properties, which indicates the possibility of their subsequent repeated use, while being simple to implement and cost-effective.

Claims (1)

A method for the regeneration of used hydrophobic sorbents, which provides for desorption and removal of adsorbed oil products from the surface of the used sorbent by heat treatment followed by the formation of a hydrophobic film on the surface and in the pores of the sorbent, sealing and cooling of the working chamber, characterized in that the heat treatment of the used sorbent is carried out at a temperature of 400-450 °C for 0.5-1.5 h, the working chamber is sealed after completion of heat treatment, cooled with a regenerated sorbent until a temperature of 25-30 °C and a pressure of not more than 30 kPa is established, while the hydrophobization of the spent sorbent occurs in the gas phase of oil hydrocarbons origin, desorbed from its surface as a result of heat treatment and condensed on the cooled surfaces of the working chamber.

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