RU2340656C2 - Method of obtaining nano-dispersed hydro-fuel emulsion and device to that end - Google Patents

Abstract

FIELD: chemistry; engines and pumps.

SUBSTANCE: proposed method of obtaining hydro-fuel emulsion involves pre-mixing fuel with water and a surfactant, forming a circulation fluid flow with a preset cross-section and speed of flow is described. Periodically, this flow is stopped and part of the flow is directed to the channel, which has a lot of smaller cross sections than the fluid flow, and blocks the channel, creating in the fluid moving by inertia negative pressure with the formation of cavitation bubbles. The indicated method is realised with the device, which contains situated on one axis a rotor and a stator close to the wide channels, where the wide channels of the rotor covers all the wide channels of the stator, and in the spaces between the channels with the wide openings of the stator are executed additional thin channels, and the spaces between the channels in the rotor have the capability of periodically covering the narrow channels.

EFFECT: dispersing of immiscible liquids and obtaining a hydro-fuel emulsion with nano-dimensional particles.

7 cl, 7 dwg

Description

The invention relates to the field of fuel and energy complex, namely the production of a water-fuel emulsion used as liquid fuel.

As you know, when burning liquid fuel, only its gas phase enters the reaction (see, for example: Pavlov, Steiner "Conditions for optimizing the processes of burning liquid fuel and gas in power and industrial installations", Leningrad, Energoatomizdat, 1984, p. 37- 40).

For this reason, when burning fuel, special measures are applied to increase its evaporation and combustion efficiency. Firstly, in order to increase the evaporation rate, the fuel is heated, and secondly, it is sprayed to increase the surface. Fuel is supplied to the furnaces, for example, by various types of nozzles: mechanical, centrifugal, jet, steam and pneumatic, creating pressure on the nozzles reaching 10 atm. To further increase the surface, and hence increase the degree of grinding of fuel particles, nozzles with special nozzles are used. Fuel atomization refers to the dispersion process, so the nozzle is a kind of fuel dispersant.

The disadvantages of the nozzles are that the atomization of liquid fuel even at a pressure of 10 atm does not lead to complete combustion. The incompleteness of combustion is due to the fact that a drop of fuel evaporates and decreases in diameter during combustion, heats up, and then overheats and undergoes decomposition-cracking. The consequence of incomplete combustion is the occurrence of non-combustible deposits on the internal components of the furnace, which reduce the heat transfer coefficient, increase the temperature of the exhaust gases, reduce the efficiency of the furnace and environmental degradation.

To increase the combustion efficiency, a more efficient atomization of the fuel is required, during which the diameter of the burning particles is brought to a value of 0.1 microns or less.

The degree of atomization and the particle size of the fuel depend mainly on the speed of collision of the droplets with each other or with the wall. In the furnaces of boiler units, for example, using nozzles, speeds are reached at which the particle size cannot be less than 10 microns. Further grinding a drop of fuel requires the creation of special devices that accelerate particles of atomized fuel to several hundred meters per second. A direct solution to the problem of increasing the particle velocity presents significant technical difficulties and is associated with large energy losses.

Theoretical consideration of liquid dispersion processes is based on the Weber criterion. Based on the Weber criterion, the probability W _{e of} dispersion of drops of mutually insoluble liquids (emulsions) to given sizes is selected from the equality

where ρ is the density of the colliding particles of the emulsion;

υ is the velocity of the emulsion particle relative to another colliding particle;

d is the diameter of the original colliding particle;

σ is the interfacial surface tension.

A numerical analysis of the Weber criterion shows, for example, that when W _e = 10 is reached, each drop of liquid breaks into two parts, and when increased to W _e = 14, the drop breaks into 10 parts already. Further, as the Weber number increases by an order of magnitude, the number of crushed particles increases by an order of magnitude (see, M. Volynsky, “The Extraordinary Life of an Ordinary Drop.” Znanie Publishing House, Moscow, 1986, p. 67). Theoretical calculations confirm that in order to increase the degree of dispersion it is necessary to increase the collision velocity.

Another technical solution to the problem of increasing the degree of dispersion is based on reducing the size of the sprayed fuel particles due to the surface tension of the liquid. In the early 60s it was found that a mixture of fuel with small additions of water droplets burned much more efficiently than pure fuel (see, for example: V.M. Ivanov "Fuel Emulsions", Moscow, publishing house of the USSR Academy of Sciences, 1962 ) Subsequent work made it possible to study this effect in more detail and even give practical recommendations on the industrial use of the phenomenon. However, in the process of practical implementation, problems arose associated with the peculiarities of mixing two heteropolar liquids and the separation of the liquid mixture into the original components during long-term storage. In the end, it was found that the presence of water in the fuel leads to an increase in the degree of dispersion of fuel particles and an increase in combustion efficiency, but this raises the problem of fuel stability or maintaining water in a droplet state. The problem that has arisen in full has not been solved, but it is known that to solve it it is necessary to reduce the size of the water droplets that make up the fuel and use surface-active substances (surfactants) to help maintain the droplet structure of the emulsion. The composition of a water-fuel emulsion usually includes liquid hydrocarbon fuel - 80-90%, water - 10-20%, surfactant - 1-2%. For fuel use, for example, fuel oil, diesel fuel, gasoline, as a surfactant - diphilic type substances that can be placed at the interface between fuel and water in a monomolecular layer, for example, sodium oleate, neftenol.

In the 80s, devices using the effect of hydrodynamic cavitation began to be used to obtain highly dispersed emulsions. In devices of this type in a liquid in various ways create negative pressures and conditions for the development of cavitation cavities (bubbles) with subsequent collapse of these cavities. When the cavitation bubble collapses, its opposite walls due to constriction by surface tension forces move towards each other at high speed and collide. As a result of motion and collision, high pressure develops, which ensures a high degree of dispersion of the liquid. The necessary increase in the speed of colliding particles is achieved due to the high speed of collapse of cavitation cavities.

Among devices designed for cavitation dispersion of liquid media, rotary-type devices are most widely used. Rotary devices and methods based on the use of rotary devices are known and can be used as analogues of the proposed method.

Known methods and devices include the following.

1. A method of creating acoustic vibrations in a liquid or gaseous medium and a device for its implementation (ed. St. No. 493991, B06 1/18), which consists in the fact that a series of successive compressions and rarefactions are created in the flowing liquid by applying an annular ring to the inner surface bodies (working chamber) of equally spaced and successively alternating forces of pressure and rarefaction of the liquid.

A device for implementing this method comprises a rotor and a stator with slots made along their generatrix in one or more rows, where each of the stator rows is freely closed on the outer surface by a freely seated and bounded from movement ring radiator in the form of a thin closed tape of material with elastic deformation, and the number of slots in the rotor and stator is made so that, with the coincident slots of the rotor and the stator, there is one or more stator slots in the gap between the two slots of the rotor.

2. An activator of physical and chemical processes using the effects of hydrodynamic cavitation - a cavitation mixer (ed. St. No. 1358140, MKI B01F 11/02).

3. Ultrasonic cavitation activator (PCT No. 94/09894, MKI B01F 7/00, 11/00 V).

4. Rotor-pulsation apparatus (ed. St. No. 13333954, B01F 7/28) for dispersing and homogenizing multicomponent mixtures with a liquid continuous phase.

5. Cavitation apparatus (RU No. 2166987, C1 B01F 7/10, 11/02).

The main disadvantage of the known methods and devices is the low average rate of collapse of cavitation bubbles, which is 35 ÷ 50 m / s and is limited by the size of cavitation bubbles obtained on these devices (see, for example: VA Saranin, “On the cavitation mechanism of the formation of high-voltage breakdown in liquid dielectrics ”, Journal of Applied Mechanics and Technical Physics, 3. Publishing House“ Science ”, Siberian Branch of the Academy of Sciences of the Russian Academy of Sciences, Novosibirsk, 1988, p. 45). The minimum size of the dispersed particles, which is achieved using analogues, is 0.5 microns.

As a prototype of the proposed method, the method of producing fuel mixtures (RU 2256696 C1 of 07.20.2005, Zhirnokleev I.A., Sidorov V.V.) based on the passage of liquid through successively located plates with decreasing hole diameter can be selected. The disadvantage of the prototype is the restriction on the dispersion associated with the minimum size of the holes through which the liquid penetrates. The restriction is associated with the presence of surface tension forces and the formation of an elastic boundary liquid layer, which limits the permeability of holes with a diameter of 100 nm or less. The permeability restriction mechanism is described in the following publications: 1) B. Valiev, Technical Report T38-18 / 66 “Investigation of the Processes for the Expiration of Working Fluids from Microholes of the AMg6 Alloy”, report holder - Federal State Unitary Enterprise State Rocket Center named after Academician V.P. Makeev ", Miass. 1966; 2) Bazaron U.B., Deryagin B.V., Bulgodaeva A.V. "Study of the shear elasticity of liquids", an article in the collection "Research in the field of surface forces", publishing house "Science", Moscow, 1967.

The aim of the present invention is to eliminate the above disadvantages and increase the degree of dispersion of particles of a water-fuel emulsion.

The goal is achieved in the following ways.

1. Initially form a fluid flow with a given cross-section and speed. This stream is then directed into a channel having a much smaller cross section (narrow channel). As a result of sharp inhibition of the fluid flow, the pressure at the entrance to the narrow channel and the flow velocity through the channel increase. Next, the narrow channel is closed, under the influence of inertial forces in the cavity of the narrow channel, zones with negative pressure are formed and conditions are created for the growth of cavitation bubbles and their collapse. Then again form a fluid flow with a given cross-section and speed for repeated water hammer. The effect of increased rarefaction and increased size of the cavitation cavity is created due to the transition of fluid from a wide channel to a narrow one and an increase in the speed of movement inside a narrow channel. To increase the efficiency of water hammer, the channels are made in the form of rectangular slots, the height of which is the same and several times greater than the width value (5-10 times). The width of the slit determines the size of the cross section of the channel. To form the initial fluid flow, an increased value of the width of the gap (wide channel) is used, and for the formation of an accelerated flow, a reduced value of the width of the gap (narrow channel) is used. The ratio of the flows and cross sections of the wide and narrow channels is determined by the ratio of the widths of the slits, for example, for a 5-fold ratio of flows, the width of the narrow slit is chosen equal to 0.5-1 mm, and the wide gap is 3-5 mm.

As experimental data show, with a pressure drop in the channel of 600 kg / cm ^{2, the} limiting value of the diameter of the cavitation bubble can be 100 μm. In this case, the Weber number is 5000, and the size of the dispersed liquid particles is at the level of thousandths of a micron. In this case, the average collapse velocity of cavitation bubbles significantly exceeds the value reached in analogs of 50 m / s and may eventually approach the limiting value of 1435 m / s, which corresponds to the speed of sound in an aqueous medium.

Consider in more detail the processes occurring in a narrow channel, and evaluate the possible numerical values of the parameters in the proposed method. Overlapping the channel with a fluid flow, even partial, leads to water hammer if the overlap time t is not more than

where ω is the speed of sound in a liquid;

l is the length of the channel in the rotor.

Assume that the condition for the occurrence of water hammer is satisfied, then the maximum pressure ΔР during water hammer is calculated by the Zhukovsky formula

Δρ = ω · ρ · υ,

where ρ is the density of the liquid;

υ is the linear velocity of the fluid through the channel.

We use the source data:

ω = 1435 m / s;

ρ = 1000 kg / m ³ ;

υ = 45 m / s

As a result, we obtain that the pressure at the inlet to the channel of small cross section during water hammer

ΔP = 659 kg / cm ²

The calculated value coincides with the expected value and confirms that the size of the dispersed fluid particles can be reduced to thousandths of a micron.

2. The problem is also solved by the fact that additional means are introduced into the method - a stator and a rotor with a number of wide channels, while the wide channels of the rotor are located opposite the wide channels of the stator, forming a through channel. In addition, narrow channels are introduced into the stator between the wide channels, and the spaces between the channels in the rotor are capable of periodically overlapping the narrow stator channels.

3. The task is additionally solved by the fact that two separate cavities for receiving fluid are performed in the stator. All wide channels are connected to the first cavity and the cavity is hydraulically connected to the pump inlet, which returns the liquid to the working chamber of the device. All narrow channels are connected to the second cavity, and the cavity itself is hydraulically connected to the tank, which is the drive for the finished product.

4. The invention is illustrated by drawings, where in Fig.1, 1A, 2 and 2B shows a device with channels located along the generatrix of the cylindrical surface of the rotor and stator, and also shows the cavity connected to the wide and narrow channels of the stator; figure 3 and 4 on an enlarged scale shows in cross section the arrangement of wide and narrow channels; figure 5 shows the hydraulic connection between the working chamber of the apparatus and the feed pump.

A device for implementing the method comprises a stator 1 made in the form of a cylinder (FIGS. 1, 2) and rotor 2 coaxially placed in it with a minimum clearance δ. Stator 1 and rotor 2 are installed in a sealed housing 3 having an inlet pipe 4, an outlet pipe 5 , a return pipe 8 and a partition 9, which divides the stator cavity into two components, the first of which (6) is connected to wide channels, and the second (7) to narrow channels.

The working cycle of the device is divided into two half-periods, in the first half-cycle wide channels of the rotor are located opposite the wide channels of the stator (Fig. 1A), in the second - wide channels of the rotor are located opposite the narrow channels of the stator (Fig. 2B).

In addition, the device comprises (Fig. 5) a pump 10 with an inlet pipe 11 and a pipe 12 for returning untreated liquid to the pump 10 through the pipe 8, as well as a pipe 13 for supplying liquid to the chamber 3 through the inlet pipe 4.

On the cylindrical surface of the stator 1 (Fig.3,4) made alternating through channels (wide and narrow). The wide channels K _{sf of the} stator 1 with a transverse dimension λ are evenly spaced around the circumference. The narrow stator channels K _must also are evenly spaced around the circumference. The width of the gaps between the wide stator channels is chosen equal to the sum of the double width of the wide channel plus the width of the narrow stator channel. The rotor channels K _p are evenly spaced around the circumference. The width of the rotor channels is also chosen equal to λ, and the gap between the rotor channels is also equal to the sum of the double width of the wide channel plus the width of the narrow stator channel.

In addition, in the stator 1 (Fig. 1), two separate cavities 6 and 7 are made. All wide channels with passage sections λ are connected to the cavity 6, and the cavity 6 itself is hydraulically connected through the pipe 8 by a pipe 12 (Fig. 5) with an entrance to a pump 10 supplying liquid to the working chamber through a pipe 13 and a pipe 4.

All narrow channels with a passage section β are connected to the cavity 7, and the cavity 7 itself is hydraulically connected by means of the outlet pipe 5 to the storage tank of the finished product.

The device operates as follows. The rotor 2 spins up to a given speed from the electric motor (not shown in Fig. 5), the pump 10 is turned on (Fig. 5). Through the inlet pipe 4 of the working chamber 3, a liquid is supplied under pressure (for example, a mixture of fuel 80%, water 20% and surfactant). The fluid fills the cavity of the rotor 2 and the channels with a transverse dimension λ (Fig.3, 4) throughout the volume. With the coincidence of the wide channels of the rotor 2 and the stator 1, the fluid begins to flow from the cavity of the rotor 2 into the cavity of the stator 1 through all the wide channels of the rotor 2 (Fig. 3), from where the fluid enters the cavity 6 (Fig. 1), and then through the pipe 8 and the pipeline 12 (figure 5) to the pump 10 and then circulates in a closed loop.

With a further rotation of the rotor 2 clockwise (Fig. 4), the wide channels with the transverse dimension λ overlap and the narrow channels of the stator 1 with the transverse size β open.

Thus, when the rotor 2 is rotated, in each of the narrow channels with a passage section β, an additional pressure drop is created, for example, equal to 659 kg / cm ² . Considering that at the moment of hydroblow, the channel with the passage section β of the stator 1 is open, and the formation of hydroblow occurs directly at the entrance to the channel of the stator 1, the main energy of hydroblow is accounted for by the increase in the kinetic energy of the fluid flow passing through the narrow channel.

After overlapping a narrow channel with a passage section β of the stator 1, the liquid continues to move by inertia, creating zones with negative pressures. This leads to a rupture of the fluid flow, the formation of cavitation bubbles of large diameter and collapse, which causes the dispersion of the liquid with the formation of nanoscale droplets. At the end of the cavitation treatment, the dispersed liquid enters the cavity 7 (figure 1), and then into the container for the finished product.

With further rotation of the rotor 2 (figure 3) and the coincidence of the wide channels of the rotor 2 and the stator 1, the re-flow of fluid from the cavity of the rotor 2 into the cavity of the stator 1 through all wide channels begins. Next, the next liquid dispersion cycle is repeated.

The proposed method and device in comparison with the prototype provide the following advantages:

- due to the formation of a circulating stream, conditions are provided for increasing pressure and creating a water hammer;

- by directing the flow into a narrow channel, the rate of fluid flow increases;

- overlapping a narrow channel leads to an increase in negative pressure and the formation of cavitation cavities of an increased size and an increase in the speed of collapse;

- accelerated collapse of cavitation cavities causes effective dispersion of the liquid;

- dividing the stream into two channels allows multiple processing of the liquid mixture and separate the finished dispersed product;

- a combination of wide and narrow channels allows you to implement the proposed method in the device;

- the introduction of separate cavities for the liquid mixture in the stator allows you to select the finished dispersed product from the circulating stream and to maintain circulation at a given level;

- the implementation of the channels in the form of rectangular slots allows you to reduce the time the channel is blocked and increase the efficiency of water hammer;

- the choice of a certain ratio between the width of the channels and the width of the gaps between the channels provides simultaneous periodic inhibition of the flow and the subsequent direction of the flow to the narrow channel;

- the choice of a narrow channel with a decreasing cross-section allows you to increase the speed of the fluid flow and the dispersion efficiency;

- the use of inclined channels allows you to divide the liquid into two streams;

- the choice of the number of channels allows you to change the modes and performance of the device.

Thus, the described sequence of operations of the method and the implementation of the dispersing device for performing these operations gives the method a new property - the ability to disperse the liquid to obtain nanosized particles.

Claims (7)

1. A method of obtaining a fuel-oil emulsion, comprising pre-mixing fuel with water and subsequent homogenization, characterized in that a circulating flow with a predetermined cross-section and speed is formed from a liquid consisting of pre-mixed fuel with water and a surfactant, periodically the flow is inhibited and at the same time a part of the flow is directed into a channel having a much smaller cross section (narrow channel) than that of a formed liquid flow, then blocking a narrow channel, creating a negative pressure in the inertial fluid for the formation of cavitation bubbles, while the circulating fluid stream after braking and blocking the narrow channel is divided into two parts: the stream, which is a nanodispersed water-fuel emulsion, passed through a narrow channel and dispersed in this channel, sent to the tank for finished products, and the inhibited stream, which did not pass through the narrow channel, is returned for processing in a closed loop. 2. A device for producing a water-fuel emulsion according to the method described in claim 1, comprising a rotor with a number of wide channels and a stator with a number of wide and a number of narrow channels located on the same axis, where the wide rotor channels, when opposite the wide stator channels, form wide through channels and when located opposite narrow channels - narrow through channels that are periodically overlapped by gaps between the rotor channels, characterized in that two separate cavities are made in the stator for receiving liquid, with the first of toryh connected to all outputs broad stator channels, and wherein the cavity is hydraulically connected to the input of a pump supplying liquid into the rotor cavity and a second cavity connected to all the outputs of stator channels and narrow cavity with hydraulically connected to the accumulator tank-finished products. 3. The device according to claim 2, characterized in that the wide and narrow channels of the stator and wide channels of the rotor are made in the form of slots of a rectangular shape parallel to the axis of the rotor. 4. The device according to claim 2, characterized in that in the rotor the width of the gaps between the slots is chosen equal to the sum of the double width of the wide slit plus the width of the narrow stator slit, and in the stator the width of the gap between the wide and narrow slit is chosen equal to the width of the wide slit. 5. The device according to claim 2, characterized in that the cross section of the narrow stator slit is selected to decrease in the direction of fluid movement. 6. The device according to claim 2, characterized in that the direction of the wide and narrow channels in the stator is chosen inclined with access to the corresponding cavity. 7. The device according to claim 2, characterized in that the number of channels in a circle is selected from one to a number determined by the geometric dimensions of the stator, rotor and channels.

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