RU2139467C1 - Method of regeneration of bottom deposits of mazout storages and device for realization of this method - Google Patents

Abstract

FIELD: oil industry; destruction of bottom deposits of mazout storages by introducing them in fuel fed for burning. SUBSTANCE: method includes dispersion of deposits to be regenerated in the course of mixing them with heated mazout. Dispersion and mixing procedure are performed in three stages. At first stage, dispersion and mixing are effected by means of low-speed mechanical facilities; at second stage, use is made of high-speed mechanical facilities which ensure development of cavitation process and, at third stage, use is made of flow-through hydrodynamic cavitation activator. EFFECT: increased productivity at reduced cost of regeneration. 9 cl, 4 dwg

Description

 The invention relates to the field of waste recovery using environmental technologies and can be used to destroy bottom sediments of fuel oil storages by introducing them into the fuel supplied for combustion.

 Bottom deposits of fuel oil are a highly viscous black oil, heavily flooded, and also containing visible mechanical impurities in the form of solid grains and dense oily formations. At room temperature, they resemble paste and practically do not have fluidity.

 For example, the studied fuel oil sample contained moisture 19%, mechanical impurities 35.8%, and also had a high ash content (6.29%). A comparison of the values of mechanical impurities and ash content shows that a significant part of mechanical impurities is combustible substances.

The viscosity of the sample was extremely high and even at 100 ^o C it was several times higher than the viscosity of fuel oil at 30 ^o C. If we exclude high ash content, then the calorific value of bottom sediments approaches the calorific value of fuel oil. Therefore, for this indicator, bottom sediments are good fuel. However, due to the high viscosity, ash content and significant moisture and solids content, this product cannot be burned using standard technology.

 At the same time, according to estimates by the US Environmental Protection Agency, 4-5 liters of fuel oil or fuel oil deposits can contaminate 3.5-4 million liters of water (http: //www.cogen.ait.ac.th/fsdp/fsdpkis2.htm , 1998).

 Fuel oil is a complex chemical composition of high molecular weight, heteroorganic (containing cycles in molecular chains, which in addition to carbon and hydrogen atoms include atoms of other elements) and metalloporphyrin complexes (MPC). The molecular weight of the components of fuel oil varies from 300 to 3000.

 In the process of oil production, transportation and refining, solid mineral impurities, alkali metal salts dissolved in water extracted from the reservoir along with oil get into its composition. During transportation, storage and processing, wear products, including corrosive ones, of pipelines, tanks and equipment are added to the oil. All of these highly undesirable components ultimately remain in fuel oil.

 Resin-asphaltene substances (CAB) contained in oil, which are distinguished by a particularly complex structure and chemical composition, are converted to fuel oil in its original form or are transformed into asphaltenes during thermocatalytic cracking.

 Further compaction of asphaltenes and their condensation during oil cracking lead to the formation of carbenes and carbides, which are in solid form in fuel oil. Carboids differ from other CABs in that they do not dissolve in any solvents, and therefore they are usually called coke.

 Asphaltenes, as well as other resinous asphaltene compounds, are natural surfactants prone to coagulation and the formation of groups of relatively unstable associates and micelles. The various compounds that make up fuel oil form its structure as a multiphase disperse system consisting of complexes whose existence is due to intermolecular interaction forces (Van der Waals forces).

 Particles of the dispersed phase contained in fuel oil include high-melting paraffin hydrocarbons, carbenes, carbides, solid mineral impurities, water globules with dissolved mineral salts, gas bubbles.

 Particles of the dispersed phase adsorb surface-active components of fuel oil on their surface. The resulting molecular layer creates a structural-mechanical barrier that increases the stability of fuel oil. The structural complex, consisting of a dispersed particle (core of the complex) and an adsorbed layer of polar molecules, is surrounded by molecules of the dispersion medium — a solvate layer oriented with respect to the dispersed particle. The thickness of the solvate layer can be tens of times greater than the size of the dispersed particle. As a result, the dispersed phase of fuel oil passes into a colloidal-dispersed state, which has a reduced tendency to coagulate and precipitate.

 Due to the complex chemical structure, perturbing forces of intermolecular interaction arise in fuel oil, leading to its destabilization. The result of destabilization is the physicochemical processes, accompanied by the allocation and enlargement of the dispersed phase, turning into deposits at the bottom of the storage tanks. These processes are natural, however, their intensity substantially depends on temperature and fuel flow rate.

To perform operations related to the storage of fuel oil, it is necessary to warm it up to 60 ... 90 ^o C, and related to the transportation of fuel oil to spray nozzles - to 120 ... 130 ^o C. At the same time, an increase in the process temperature will intensify the destabilization of fuel oil, and sedimentation or insufficient motion speeds contribute to an increase in the intensity of coagulation of carbenes and carbides and their deposition.

 The deposition of CAB and mineral impurities leads to the formation of viscous hard to remove deposits in fuel oil tanks. Particles of carbides and mineral impurities cause abrasive wear of pumps, valves, nozzles.

A known method for producing liquid fuel from polyolefin waste, i.e., essentially a method for the recovery of waste by burning (http: // www.femirc. Org.pl/oferty/ ofe45.htm, 1998). In this method, a non-zeolitic catalyst is introduced into a polyolefin mass preheated to 350-450 ^° C.

 However, the process of chemical decomposition of fuel oil sludge is extremely slow, which does not allow using the known method for the regeneration of bottom sediments of fuel oil storages.

 The same drawback is inherent in the method of co-chemical decomposition of municipal waste, biomass and coal dust (http: //www.nedo.go.jp/itd. Grant-e / JITU / JE007.htm, 1998).

 A known method of regenerating municipal waste, in which 75% of the waste is crushed with 25% oil shale and served for burning (http://www.peatsorb.com/index3.htm, 1998).

 However, the known method can be used only for the solid part of the bottom sediments, thus, its scope is limited. In addition, an unacceptable amount of nitrogen oxides and other harmful substances are emitted into the atmosphere when chopped solid waste is supplied for combustion.

 A known method for the regeneration of waste oil, in which oil and surfactants are injected into a pulverized wood pulp in order to obtain a colloidal solution (French application N 2519019, C 01 L 1.00, 1983).

 However, this method is quite expensive and low productivity, since it is associated with the dissolution of biomass.

 Closest to the proposed method is the regeneration of fuel oil deposits, including the introduction of an additive and heating the deposits, followed by the introduction of heated fuel oil in an amount of 80-90% and passing 1-2 times through a dispersant, where 10-20% of water is fed (see a.c. N 1791673, F 23 G 7/05, 1990).

 However, the introduction of additives and the need to heat the sludge to significant temperatures leads to a rise in price and lower productivity of the method, which nevertheless does not allow the regeneration of highly viscous and close to solid deposits. At the same time, an insufficient degree of dispersion leads to the fact that when the mixture is burned, nozzles and heating surfaces of boiler units are coked, and harmful emissions into the atmosphere increase.

 For the grinding of solid materials (coke, lignite, etc.) in the presence of hydrocarbon liquids and water, it is known to use ball mills before serving for combustion (see UK Patent No. 1,600,865, C 01 L 1/00, 1978).

 However, the degree of dispersion of solid inclusions and water is low (particle size 0.15-2 mm), which leads to an increase in harmful emissions.

 Also known is a hydrodynamic cavitation mixer, in the housing of which swirlers (cavitation bodies) are placed. In the mixture, the gel is fed with coal dust with a particle size of 20-40 microns, water and an organic liquid, for example fuel oil, and a suspension is obtained at its outlet (see RF patent N 2097408, C 01 L 1/32, 1994).

 The complexity of using this device for the regeneration of bottom sediments lies in the fact that highly viscous sediments cannot be fed into the cavitation zone at high flow rates, and fluctuations in speed lead to the disruption of the cavitation process.

 Closest to the proposed device is a. with. N 1791673, containing fuel oil supply lines, dispersant and pump, as well as tanks for bottom sediments and water-fuel emulsion.

 As already noted, this device is low-productivity and does not allow the regeneration of highly viscous and close to solid deposits.

 Thus, the technical result expected from the use of the proposed method and device is to increase productivity and reduce the cost of regeneration of bottom sediments while maintaining high environmental performance, the possibility of regeneration of highly viscous deposits.

 This result is achieved by the fact that in the method of regenerating bottom sediments of fuel oil storages, including dispersing regenerated sediments during their mixing with heated fuel oil, dispersing and mixing are carried out in three stages, with dispersing and mixing at the first stage using low-speed mechanical means, and at the second stage, high-speed mechanical means ensuring the development of the cavitation process, and on the third - using flow hydrodynamic cavit insulating activator.

Moreover, in the first stage, the amount of fuel oil heated to a temperature of 60-70 ^o C, in the mixture is maintained in the range of 50-75%, in the second 67-85% and in the third 95-96.3%.

In addition, dispersion and mixing at the first stage is carried out at shear rates of 10 ² -10 ³ s ^-1 and at shear stresses of 10 ³ ... 10 ⁵ Pa, at the second stage - at cavitation numbers up to 2, and pa third at cavitation numbers 4-6.

 The indicated result is also achieved by the fact that the device for carrying out the method, comprising fuel oil supply lines, a dispersant and a pump, is equipped with an extruder with a loading neck, a perforated hollow worm and side hollow pins displaced relative to the holes of the worm, and an activator, and the dispersant is made in the form of a rotary mixer , the inlet pipe of the hollow stator which is made with a swirler and an inclined pipe for supplying heated fuel oil, while the output of the extruder is connected to the inlet pipe of the hollow stat pa rotary mixer whose output is connected through a pump to the input of the activator, and the cavities and extruder screw pins, inclined conduit supplying heated fuel oil rotary mixer and an input connected to the corresponding activator arteries supplying heated fuel oil.

 In this case, the activator can be made with a confuser, a diffuser and a wave-shaped cavitation body, the generatrix of which is made with one point as far away from the axis of the cavitation body.

 In addition, the rotor and stator of the rotary mixer can be made with alternating ring concentric protrusions made with radial slots, and valleys, laterally limited by the surfaces of rotation, while the median diameters of the protrusions and valleys of the stator are equal to the median diameters of the reciprocal cavities and protrusions of the rotor, and the depth of the radial the slots on the protrusions of the stator and rotor are selected from the condition of their complete overlap in the axial direction by the protrusions of the rotor and stator, respectively.

 In this case, the diametrical section of the protrusions can be made trapezoidal, with the location of the smaller base of the trapezoid on the free end of the protrusion.

It is also advisable to choose the sum of the angles for a larger trapezoid base in the range of 170-155 ^° .

 In addition, the stator of the rotary mixer can be made with the possibility of adjustable axial fixed movement.

 In FIG. 1 shows a General view of the device for implementing the method, FIG. 2-4 illustrate the implementation of the extruder, activator and rotary mixer, respectively.

 The device (Fig. 1) contains a hopper 1 for recyclable waste, an extruder 2 with a loading neck 3, a rotary mixer 4 and an activator 5, at the input of which a centrifugal pump 6 is set, driven by an electric motor 7. An electric motor 8 rotates the rotor of the mixer 4, and the electric motor 9 - extruder screw 2. Fuel oil supply is regulated by valves 10, position 11 indicates the steam supply line necessary to clean the installation, and valves 12 allow sampling.

 The extruder 2 is made with hollow pins 13 and the screw 14. The latter is also made hollow, with holes 15 offset relative to the pins 13 (Fig. 2).

 The activator 5 (hydrodynamic, cavitation - Fig. 3) is made with a confuser 16 and a diffuser 17, between which a cylindrical housing 18. The activator 5 is connected using the output 19 and input 20 flanges. Behind the wave-shaped cavitation body 21 in FIG. 3, a cavitation zone 22 is shown. The body 21 is mounted cantilevered on an axis 23 fixed between the frames 24 by means of a nut 25. The purpose of the activator is the chemical and physico-chemical activation of the mixture, which is expressed, in particular, in a decrease in surface tension forces.

 The rotary mixer 4 (Fig. 4) contains a housing 26, in the cavity of which a hollow stator 27 and a rotor 28 with annular protrusions 29 are placed. The stator 27 is made with an inlet axial pipe 30, which is made with an inclined pipe 31. In the pump part 32 of the mixer 4 on the impeller 34 is mounted to the shaft 33. The nozzle 30 is connected to the body of the stator 27 through a diffuser 35. In FIG. 4 also shows the outlet pipe 36 and the swirl 37 of the pipe 30.

 For the supply of heated fuel oil, pipelines (lines) 38 are used (Fig. 1).

 At the exit of the extruder 2, a filter 39 is installed, through which the crushed mixture is fed into the outlet pipe 40, and the pipe 41 is returnable, through which larger particles can again be fed into the neck 3. The position of the stator 27 is regulated by a small displacement mechanism 42, providing an adjustable fixed displacement of the stator 27 (Fig. 4). With the trapezoidal shape of the protrusions 29, the mechanism 42 provides simultaneous adjustment of the axial and radial clearance between the stator 27 and the rotor 28. Between the protrusions 29 of the stator (rotor) are depressions 43, radial slots 44 are made in the protrusions 29. The diametrical section of the protrusion is indicated by 45.

 The method is based on the destruction of enlarged and heavier dispersed components of bottom sediments that arose during storage of fuel oil, due to the action of high shear stresses in the high-speed flow, including when the cavitation effect occurs.

 The method is implemented in three stages (in three series-connected apparatuses) by hydromechanical processing (GMO) of bottom sediment mixtures with fresh heated fuel oil. At the same time, the proportion of fresh fuel oil at each stage increases. The fuel oil content in the mixture at each stage depends on the initial viscosity of the deposits.

 By low-speed mechanical means it is necessary to understand mechanical mixers in which cavitation phenomena do not occur, by high-speed mechanical means combined means in which, along with mechanical stirring (usually carried out by a rotating rotor), the cavitation process develops.

 The implementation of the method is illustrated by the example of the operation of the device.

Bottom sediments enter through the self-unloading bucket (hopper) 1 into the neck 3 and, under their own weight, fall onto the rotating worm 14 of the extruder 2. Into the extrusion processing zone, through the pins 13 and the cavity of the worm 14, fresh fuel oil is heated up to a temperature of 60 ... 70 ^o C, where it mixes with bottom sediments. Here, the mixture goes through the first stage of high-intensity hydromechanical treatment, as a result of which it is homogenized and becomes fluid.

Under the influence of the pressure arising in the extruder 2, the homogenized mixture is supplied through the nozzles 40 and 30 to the rotary mixer 4, where fresh fuel oil heated to a temperature of 60 ... 70 ^o C is fed through the inclined pipe 31, which is mixed with the swirling flow from the axial pipe 30. The resulting the diluted mixture enters the space between the stator 27 and the rotor 28. When the rotor 28 is rotated and the slots 44 of the rotor 28 and the stator 27 are combined, a pulsation of the liquid causes cavitation of the flow. As a result of cavitation and repeated collision of the jets of the mixture with the protrusions 29, the inclusions contained in it are crushed to a size of 15 ... 30 microns.

 For the effective operation of the mixer 4, the gap between its stator 27 and the rotor 28 should be no more than 2 mm. At the same time, in order to avoid jamming of the mixer 4 by large mechanical inclusions, the mixture is filtered through openings 8 in the housing 2 with a diameter of up to 2 mm. Particles settling on the filter surface are cleaned off by the worm 3 and transported to the nozzle 41, and the cleaned mixture through the nozzle 12 is fed to the inlet of the mixer 4.

The treated mixture enters the impeller 34 of the pump part 32 and under pressure is transported to the suction nozzle of the centrifugal pump 6, and fresh fuel oil heated to 60 ... 70 ^o C is supplied there under pressure. Upon exiting pump 6, the mixture enters activator 4, which is a hydrodynamic cavitation apparatus (GCA), where it undergoes final GMO in a hard cavitation field, due to which chemical and physicochemical activation of the mixture is achieved. As a result, the size of the dispersed phase is reduced to 5 ... 8 microns.

The cavitation process is understood to mean the formation in the liquid medium of bubbles filled with steam, gas or a mixture thereof. Cavitation bubbles form in those places of the liquid where the pressure drops below a certain critical pressure (p _cr ) due to the high flow rates. Typically, the cavitation process occurs at pressures slightly lower than the saturated vapor pressure at a given temperature. In liquid boiler fuel, the role of cavitation nuclei is played by particles of the dispersed phase: the solid fraction of carboids and mineral impurities, water globules, gas bubbles.

Bubbles of gas or vapor, moving with the flow and falling into the pressure region p <p _cr , expand greatly as a result of the fact that the pressure of the gas and vapor contained in them is greater than the combined effect of surface tension and pressure in the liquid. As a result, a zone filled with moving bubbles is created in the reduced pressure section of the stream.

 After the transition to the zone of high pressure, the growth of bubbles stops, and they begin to contract. If the bubble contains a lot of gas (vapor), then when it reaches the minimum radius, it is restored and performs several cycles of damped oscillations. If there is little gas (steam), then the bubble collapses completely in the first period of life.

 The collapse of cavitation bubbles occurs at a high speed (comparable to the speed of sound). If the degree of development of cavitation is such that many bubbles arise and collapses simultaneously, then the phenomenon is accompanied by a powerful wave process with a continuous spectrum of vibration frequencies from several hundred hertz to thousands of kilohertz. In the cavitation region, hydrodynamic perturbations arise in the form of strong compression pulses (micro shock waves) and microflows generated by pulsating bubbles.

 The energy released as a result of post-cavitation relaxation of the stream intensively crushes the particles of the dispersed phase to sizes of 1 ... 5 μm, significantly reducing the rate of their deposition.

The cavitation number is the quantity σ = 2 (P ₁ -P _cr ) / ρυ $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ where P ₁ is the inlet pressure; P _cr - pressure in the narrowest section; ρ is the density, υ ₁ is the velocity in the narrowest section.

 The three-stage treatment of mixtures is caused by the need to gradually reduce the viscosity of bottom sediments by mixing them in stages with fresh fuel oil. Moreover, the performance of each subsequent apparatus of the installation exceeds the productivity of the previous one several times. Due to the different viscosity of the mixture, apparatuses of various designs are used at each stage of processing, the intensity of the hydrodynamic effect of which increases as the fuel oil passes through the tract.

 As a result of a high-intensity hydrodynamic effect on the components of the bottom sediments, they undergo mechanical destruction in the range from mechanical crushing of particles of the dispersed phase (carbenes, carbides, mineral particles, water globules) to mechanocracking of heavy hydrocarbon and heteroorganic components of the sediments.

 With mechanical dispersion of particles, their interfacial surface increases. Surfactants contained in excess in fresh fuel oil are adsorbed on newly formed surfaces. The resulting structural-mechanical barrier stabilizes the particles of the dispersed phase, i.e. prevents their aggregation and sedimentation.

 As a result of mechanocracking of heavy organic components of sediments, fragments of molecules arise, the free radicals of which have high chemical activity. Active cracking products interact with the surfactant of fresh fuel oil, forming compounds that increase fuel stability. Mechanocracking also leads to a decrease in the branching of paraffin structures.

 Thus, fuel oil bottom sediments, which are highly viscous unstable systems with a significant content of coarse dispersed abrasive inclusions and water, as a result of a three-stage GMO mixed with fresh heated fuel oil turn into a colloidal dispersed system suitable for burning, i.e. effectively disposed of.

Claims (9)

 1. A method of regenerating bottom sediments of fuel oil storages, comprising dispersing the regenerated sediments during their mixing with heated fuel oil, characterized in that the dispersion and mixing are carried out in three stages, the dispersion and mixing being carried out in the first stage by low-speed mechanical means, and in the second, by high-speed mechanical means ensuring the development of the cavitation process, and on the third - using a flowing hydrodynamic cavitation activator . 2. The method according to claim 1, characterized in that in the first stage the amount of fuel oil heated to 60 - 70 ^o C in the mixture is maintained in the range of 50 - 75%, in the second - 67 - 85% and in the third 95 - 96, 3% 3. The method according to claim 1, characterized in that the dispersion and mixing in the first stage is carried out at shear rates of 10 ² - 10 ³ s ^-1 at shear stresses of 10 ³ - 10 ⁵ Pa, in the second stage - at cavitation numbers up to 2, and on the third - with cavitation numbers 4 - 6.  4. A device for implementing a method for the regeneration of bottom sediments of fuel oil depots containing fuel oil supply lines, a dispersant and a pump, characterized in that it is equipped with an extruder with a loading neck, a perforated hollow worm and side hollow pins displaced relative to the holes of the worm, and an activator, and the dispersant is made in the form of a rotary mixer, the inlet pipe of the hollow stator which is made with a swirler and an inclined pipe for supplying heated fuel oil, while the output of the extruder is connected to the input CB conduit hollow rotor stator mixer, the output of which is connected through a pump to the input of the activator, and the cavities and extruder screw pins, inclined conduit supplying heated fuel oil rotary mixer and an input connected to the corresponding activator arteries supplying heated fuel oil.  5. The device according to claim 4, characterized in that the activator is made with a confuser, a diffuser and a wave-shaped cavitation body, the generatrix of which is made with one point as far away from the axis of the cavitation body.  6. The device according to p. 4, characterized in that the rotor and stator of the rotary mixer are made with alternating ring concentric protrusions made with radial slots, and valleys laterally bounded by rotation surfaces, while the median diameters of the protrusions and valleys of the stator are equal to the median diameters of the reciprocal cavities and protrusions of the rotor, and the depth of the radial slots on the protrusions of the stator and rotor is selected from the condition of their complete axial overlap with the protrusions of the rotor and stator, respectively.  7. The device according to claim 6, characterized in that the diametrical section of the protrusions can be made trapezoidal, with the location of the smaller base of the trapezoid on the free end of the protrusion. 8. The device according to claim 7, characterized in that the sum of the angles with a larger trapezoid base is selected in the range of 170 - 155 ^o .  9. The device according to claim 4, characterized in that the stator of the rotary mixer is made with the possibility of adjustable fixed movement.

Images