FR2662377A1 - METHOD AND DEVICE FOR SPRAYING LIQUID, AND APPLICATIONS THEREOF - Google Patents

Abstract

The invention relates to a process for spraying a liquid with the aid of at least one auxiliary fluid, such as a gas, this process comprising the use of: - an annular flow of the said liquid (27), - an annular flow of a primary gas (38), - an annular flow of a secondary gas (23) which is identical to or different from the previous gas, the said process consisting in: a) directing the flow of liquid within the said flow of primary gas in the flow direction of the latter, b) producing an annular thin film of liquid by directing the coaxial flows of liquid and primary gas onto the periphery of a ring (30), one of the free ends of which is shaped in the form of a ridge, c) spraying the liquid at the end of the said ridge. According to the invention, the ratio of the total mass of gas with respect to the total mass of the liquid is less than 0.5.

Description

i

  METHOD AND DEVICE FOR SPRAYING LIQUID, SO

AS THEIR APPLICATIONS.

  The present invention relates to a method and a device for spraying liquids. The invention also relates to various applications of this method and

of this device.

  The method and the device according to the invention have been particularly studied for the spraying of fuels with a view to their combustion, but, of course, they can be used for

  spraying liquids for other applications.

  Reference will be made hereinafter, to situate the problem posed, to the combustion of products from the refining of crude oil, but the solution provided by the invention can be applied to solve equivalent problems, as will be explained in the

following this description.

  The refining of crude oil is producing, at the present time, heavy products, more and more viscous,

from conversion units.

  To obtain a good combustion of these heavy products, it is necessary that they be pulverized in fine droplets, whose diameter is small enough, of the order of 100 thousandths of an mm. It is estimated that, to obtain this size of droplets, it It is necessary for the viscosity of the product to be reduced to less than

  mm 2 / s, at the temperature of formation of the droplets.

  For products whose viscosity at 100 ° C is 106 mm 2 / s, it is necessary to use spraying temperatures of 2700 C to 3000 C, so as to reduce the viscosity of the product to about 20 mm 2 / s and to achieve good spraying by the usual spraying means. If we do not want to use too high temperatures, we have to flux (dilute) viscous heavy products partly by middle distillates, which the refining industry is in deficit, and therefore to increase production. heavy fuels, the

refining is surplus.

  If one tries to use the usual processes of spraying at lower temperatures without flowing the fuel, one has to use this fuel at higher viscosities. The usual methods used for this purpose have the following disadvantages: mechanical spraying then requires high pressures, of the order of 2 107 pascals, at 200 ° C, for a product with a viscosity of 400 mm 2 / s at 200 ° C; steam-assisted spraying is therefore not economical because of the high required vapor levels (above 80%); spraying with rotary cup burners is possible (see for more details A GUILLERMIC's book "Heating by liquid fuels", TECHNIP Editions, Volume 3, page 269), but these burners have the disadvantage of requiring delicate adjustments and a particular maintenance of the fact

  of the existence of moving parts.

  The Applicant has found the means of spraying viscous fuels at higher viscosities than those generally used and therefore at lower temperatures, by developing, in the spraying device, a film of viscous fluid, which is then pulverized into fine droplets using

two streams of gaseous fluids.

  This technique, called injection technique with pre-film formation, is already known. For example: fuel spraying in gas turbines (see "The development of an air blast atomizer for

  gas turbine application ", by A H LEFEBVRE and D MILLER.

  Granfield College of Aeronautics, Report No. 193, June 1966, or "Influence of liquid properties on airblast atomizer spray characteristics", by A. RIZKALLA and H. LEFEBVRE, Journal of Engineering for Power, April 1975, pp. 173-179; the spraying of coal-water mixtures (see "A new burner design for CWS combustion", by SK BATRA and WA WALSH Jr., Fifth International Symposium on Coal Slurry Combustion and Technology, 25-27 April 1983, TAMPA, Florida. all these known devices, which are combustion devices where the gaseous fluid is therefore air, the gas / liquid mass ratio must be very high, often of the order of 2, for the spraying to be correct. gases used are from

the order of 100 to 150 m / s.

  Such flows of gas are inconceivable, when it comes, as is the case in refineries, to spray with the help of pressurized water vapor a fuel

high viscosity.

  Indeed, even if refining is available in pressurized steam, it is not

  not economical to use such vapor levels.

  In addition, the Applicant has found that, if it is possible to lower the vapor content to values much lower than those usually mentioned, while maintaining a good quality of spraying, it is then necessary to use high vapor speeds. to obtain a good spray, impossible to achieve with the previously known devices,

  using relatively low gas velocities.

  The purpose of the present invention is therefore the spraying of liquids, especially with a view to their combustion. For this purpose, the subject of the invention is a process for spraying a liquid using at least one auxiliary fluid such as a gas, this process comprising the use of: an annular flow of said liquid , an annular flow of a primary gas, an annular flow of a secondary gas, identical or not to the preceding one, said method consisting of: a) driving the flow of liquid inside said

  primary gas flow in the flow direction of that

  ci, b) to produce an annular thin film of liquid, by conducting the coaxial flows of liquid and primary gas on the periphery of a ring whose one of the free ends is shaped in the shape of a ridge, c) to spray the liquid at the end of said ridge by the combined action of said primary gas flow and the secondary gas flow flowing inside the ring in the same direction as said liquid flow and said gas flow primary, this method being characterized in that the ratio of the total mass of gas to the total liquid mass

is less than 0.5.

  The subject of the invention is also a device for spraying a liquid flow using at least one auxiliary fluid such as a gas, for carrying out the above process, by carrying out: an annular flow of said liquid, an annular flow of a primary gas, an annular flow of a secondary gas, identical or not to the previous one, this device being characterized in that it comprises a) at least one duct supplying said liquid in a first annular liquid channel, b) at least one supply duct for supplying said primary gas in a second annular primary gas channel, c) at least one duct (19) for supplying said secondary gas in a third annular secondary gas channel, the outlets of the annular channels being arranged from the outside to the inside of the device such that the outlet of the first channel and the outlet of the second channel open jointly into a fourth annular channel, which leads the mixture of liquid and gas pr at the outlet of the third channel, the mixture of liquid and primary and secondary gases being led outside the device by a fifth annular channel possibly forming a venturi, the inner wall of the fourth annular channel being shaped in the form of a ridge . The main characteristic of the process according to the invention is therefore that the mass ratio of the gas or gases relative to the liquid is less than 0.5. The velocity of the gas or gases must be as high as possible. It is advantageous for the velocities of the primary and secondary gas flows to be sonic at height.

of the ridge.

  The gas may be air, water vapor, refinery gas, in the case of fuel combustion, or water vapor, in the case of pre-spraying

said fuel.

  In the device according to the invention, when the primary gas and the secondary gas are identical, these preferably come from one and the same main source, from which the primary gas flows

  and secondary gas are then separated.

  For reasons of technical realization, the various annular channels are made by an assembly of parts nested within each other

  as will be seen below in the description of the

  FIGS. The accompanying drawings, which are not limiting in nature, are intended to illustrate the invention. In these drawings: FIG. 1 is a longitudinal section of a sprayer according to the invention, intended for the combustion of a heavy fuel; FIG. 2 is an exploded view, in section, of different parts of the sprayer of FIG. 1, shown as they are adapted to each other along axis AA 'of FIG. 1, during assembly of the sprayer, with the exception, for purposes of simplification, tube 3, which will be mentioned later. The sprayer 1, shown in the drawings and intended to equip an oven for the combustion of a heavy fuel oil, is incorporated in an outer body 2 of cylindrical section, integral with a rod, not shown,

fixing everything to the wall of the oven.

  The sprayer itself is composed of several parts, incorporated or attached to the outer body 2, namely: a main cylindrical tube for supplying water vapor 3, a central injector body 4, a peripheral distributor of steam, water 5, a central distributor of water vapor 6, a nozzle 7, a fastening element such as a screw 8, possibly a calibrated piece in the form of venturi 50 disposed in the tube 3, intended to maintain the flow rate as constant as possible, to facilitate the use of the device (only the flow rate of

  liquid may have to be adjusted).

  All parts of the injector are parts of

revolution around the axis A-A '.

  As will be described below, the combination of the body 4, the distributors 5 and 6 and the tip 7,

  is the distributor of water vapor.

  The tube 3 is, as mentioned above, the main steam supply tube of the sprayer, through the internal cylindrical channel 9 of the tube

  3, connected to a steam source not shown.

  The outer wall 10 of the tube 3 and the inner wall 11 of the outer body 2 constitute an annular channel 12 for supplying heavy fuel oil, connected to a fuel source

heavy, not shown.

  The channel 9 supplies with water vapor a cylindrical central internal chamber 13, arranged in the body

central 4.

  In the central body 4 are provided cylindrical channels 14, the inputs 16 are disposed at the inlet of the chamber 13 and whose outputs 17 open into an annular chamber 18 arranged in the distributor 5 so as not to overload the figures, the channels 14 not visible on the cuts were not

  represented in broken lines, as is customary.

  In the central body 4 are also provided cylindrical channels 19, the inputs 20 of which are arranged at the downstream end of the chamber 13 and whose outlets 21 open into entries 22 of corresponding cylindrical channels 23, arranged in the distributor 6, through a groove 21 'forming an annular channel

of distribution.

  At the outlet of the channels 23, there is an annular channel 23 'formed by a portion of the inner wall of the endpiece 7 and the inner wall 32' of the distributor 6 forming the edge with the outer wall 32 of said

distributor.

  In order not to overload the figures, the channels 19 and 21, which are not visible on the sections, have also not been shown in dashed lines. In the central body 4, cylindrical channels 24 are furthermore arranged, of which only two have been for the purpose of clarity, the inputs 25 are located at the end of the channel 12 and whose outputs

  26 open into an annular channel 27.

  The walls of this channel are constituted by a bevelled portion 28 of the body 4 and by a portion of the

internal wall 29 of the distributor 5.

  The channel 27 is extended by an annular channel 30, whose walls are constituted by a portion of the inner wall 31 of the outer body 2 and a portion of the outer wall 32 of the distributor 6, which constitutes the edge on which the prefilm of liquid, which can

be smooth or serrated.

  The channel 30 is extended by a circular channel 33 in the form of a ring and possibly a venturi, the walls of which consist of a portion 34 of the inner wall of the outer body 2 and a portion 35 of the outer wall of the endpiece 7. When the channel 33 is in the form of a venturi, part of the kinetic energy of the gas is transformed into pressure.

lower pressure levels.

  The annular chamber 18 is connected to the channel 30 by cylindrical channels 36, arranged in the distributor 5 and extended by an annular channel 38, constituted by a portion 37 of the outer wall of the distributor 5 and

  a portion 39 of the inner wall of the outer body 2.

  The sprayer is mounted as follows.

  The distributor 5 is slid into the outer body 2, the central body 4 is engaged in the outer body, its end 40 passing through the distributor 5, which is plated

  against the recessed end 41 of the outer body 2.

  The distributor 6 and the nozzle 7 are threaded onto the end 40 of the body 2 and the screw 8 is screwed into the

thread 42 of the body 4.

  The sprayer is then slid on the tube 3, feeding it with steam, and then connected to the feed

in fuel.

  The operation of this sprayer is as follows.

  The heavy fuel oil is fed through the annular channel 12, the cylindrical channels 24, the annular channel 27 to

annular channel 30.

  At its entry into said channel 30, the heavy fuel oil stream is pressed onto the outer wall 32 of the distributor 6 by an external peripheral flow of water vapor. This external peripheral flow comes from a main flow of water vapor, brought by the internal channel 9, a part of which enters the inlets 16 is driven by the cylindrical channels 14 in the annular chamber 18 and then

  in the cylindrical channels 36 and the annular channel 38.

  At the end of the lip formed by the end of the wall 32, the film of fuel formed by the action of the primary peripheral water vapor stream receives internally a secondary peripheral water vapor flow. from room 13, through the entrances

, channels 19 and 23.

  The heavy fuel oil is thus finely divided in the annular channel 33 and pulverized into fine droplets at the

exit from it.

  When the process according to the invention is used for the combustion of heavy fuel oil having a viscosity at 1000 ° C. of between 40 and 106 mm 2 / s, the operating conditions are as follows: fuel oil pressure: between 105 and 40 10 pascals , water vapor pressure: between 105 and 15.105 pascals, fuel oil temperature between 50 and 350 C, water vapor temperature: between 100 and 2500 C,

  fuel flow: between 80 kg / h and 2000 kg / h.

  Although the method and device according to the invention have been developed for the spraying of viscous product, and they can be applied to the spraying of less viscous products, such as a catalytic cracking feed, such as

  show the examples that follow.

  These examples are intended to illustrate the invention and

  naturally have no limiting character.

Example 1

  Various attempts have been made to spray an oil and to burn a heavy liquid fuel to

  using the sprayer shown in Figures 1 and 2.

  Spray test The spraying test is carried out using an oil having a density at 15 ° C of 850 kg / m 3 (measured according to the AFNOR NFT 60-101 standard) and a viscosity of 300 mm 2 / s, at 200 ° C. (measured according to the AFNOR NFT standard)

-100).

  This oil was chosen because of its high viscosity at 20 CC, representative of that of a viscous fuel at a higher temperature. It is indeed preferable to carry out the test at 20 ° C. for reasons of

  security and ease of measurement.

  We measure the diameter of the droplets at the exit of the

  sprayer using a laser granulometer.

  The oil flow is 200 kg / h and the pressure of

6.105 pascals.

  As auxiliary fluid, nitrogen is used at a mass ratio of 0.2 with respect to the oil, the pressure of the nitrogen being 610 pascals. The average diameter of the droplets obtained, defined according to the law of ROSINRAMMLER (see "Introduction to fluid mechanics and heat transfer by J M KAY pages 299-306, Editions DUNOD), is 85

thousandths of a millimeter

  This test shows the effectiveness of the sprayer according to the invention for spraying liquids.

high viscosity.

  Combustion test The combustion test is carried out in a 2 MW furnace using a fuel oil having the following characteristics: density at 150 ° C: 1025 kg / m 3,

viscosity at 1000 C: 1200 mm 2 / s.

  The fuel oil temperature is 1200 C (its viscosity is then 330 mm 2 / s) and its pressure of 5 105 Pascals,

the flow rate being 150 kg / h.

  As the auxiliary fluid, water vapor is used at a weight ratio of 0.2 with respect to the fuel.

  the pressure of the water vapor being 5.5 105 Pascals.

  Good fuel combustion was obtained.

Example 2

  In this test, an oil with a density of 840 kg / m 3 at 150 ° C. and a viscosity of 15 mm 2 / s at 200 ° C. is used. The diameter of the droplets at the outlet of the

  sprayer using a laser granulometer.

  The oil flow rate is 600 kg / h and the pressure is 6,105 pascals. Nitrogen is used as an auxiliary fluid at a mass ratio of 0.07 with respect to the oil.

  nitrogen pressure being 5,105 pascals.

  The average diameter of the droplets obtained, defined

  according to the law of Rosin-Rammler, is 100 thousandths of a millimeter.

  This test shows the effectiveness of the sprayer according to the invention for the spraying of low-viscosity liquids, as encountered in processes and devices for catalytic cracking in a fluidized bed.

hydrocarbon loads.

Claims (5)

  A method of spraying a liquid with at least one auxiliary fluid such as a gas, said method comprising the use of: an annular flow of said liquid, an annular flow of a gas primary, an annular flow of a secondary gas, identical or different from the previous one, said method consisting of: a) driving the flow of liquid inside said   primary gas flow in the flow direction of that   ci, b) to produce an annular thin film of liquid, by conducting the coaxial flows of liquid and primary gas on the periphery of a ring, one of whose free ends is shaped in the shape of an edge, c) to be sprayed the liquid at the end of said ridge by the combined action of said primary gas flow and the secondary gas flow flowing inside the ring in the same direction as said liquid flow and said gas flow this process being characterized in that the ratio of the total mass of gas to the total mass of the liquid is less than 0.5.   Method according to Claim 1, characterized in that the speeds of the primary and secondary gas flows   are sonic at the height of the ridge.   3 Device for spraying a liquid flow using at least one auxiliary fluid such as a gas, for carrying out the process according to Claim 1, by producing: an annular flow of said liquid, an annular flow of a primary gas, an annular flow of a secondary gas, identical or not to the previous one, this device being characterized in that it comprises a) at least one conduit (24) supply said liquid in a first annular liquid channel (27), b) at least one conduit (14) for feeding said primary gas into a second annular primary gas channel (38),   c) at least one duct (19) for supplying said secondary gas into a third annular secondary gas channel (23 '), the outlets of the annular ducts being arranged from the outside to the inside of the device so that the the first channel (27) and the outlet of the second channel (38) jointly open into a fourth annular channel (30), which conducts the mixture of liquid and primary gas at the outlet of the third channel (23 '), the mixture liquid and primary and secondary gases being led outside the device by a fifth annular channel (33), the inner wall of the fourth annular channel (30) being shaped in the form of an edge. 4 Device according to claim 3, characterized in that it consists of the following elements, nested in each other: an outer body (2), a main cylindrical gas supply tube (3), a central body d injector (4), a peripheral gas distributor (5), a nozzle (7), fastening means (8).   Device according to one of claims 3 and 4,   characterized in that it further comprises a venturi-shaped piece (50) disposed in the cylindrical tube   main gas supply (3).   6 Use of the process according to one of   1 or 2 or the device according to one of the   claims 3 to 5 for spraying fuels   liquids, in particular of heavy and viscous fuels, view of their combustion.   7 Use of the process according to one of   1 or 2 or the device according to one of the   Claims 3 to 5 for spraying the charge   a catalytic cracking unit.