WO2017021977A1

WO2017021977A1 - Multi-stage liquid atomizer for fluidized catalytic cracking

Info

Publication number: WO2017021977A1
Application number: PCT/IN2016/050182
Authority: WO
Inventors: Madan Kumar K; Praveen Kumar Singh; Pramod Kumar; Venkata Chalapathi Rao PEDDY; Venkateswarlu Choudary Nettem; Sriganesh Gandham
Original assignee: Hindustan Petroleum Corporation Limited
Priority date: 2015-08-06
Filing date: 2016-06-10
Publication date: 2017-02-09

Abstract

A spray nozzle assembly 10 to use multi-stages atomization of liquid feed for fluidized catalytic cracking process is described. The assembly comprises an inner conduit 50 comprising a liquid inlet 22 to let liquid feed flow to enter there through and a passageway to provide a passage to the liquid feed flow. The inner conduit comprises a plurality of sets of discharge orifices disposed at specific locations of the inner conduit to discharge droplets of the liquid feed flow. The assembly 10 further comprises an outer conduit 17 comprising a gas inlet 21 to let a gas stream to enter into the outer conduit. The outer conduit defines a mixing zone 20 where the liquid feed and the gas stream are mixed to achieve the atomization. The mixed flow is discharged through orifices 26 of the spray nozzle tip.

Description

MULTI-STAGE LIQUID ATOMIZER FOR FLUIDIZED CATALYTIC

CRACKING

TECHNICAL FIELD

[0001] The present subject matter relates, generally, to liquid spray nozzles, and more particularly, to a spray nozzle for atomizing and spraying a liquid feed to a fluidized catalytic cracking riser reactor.

BACKGROUND [0002] Generally, fluidized catalytic cracking (FCC) process is used in petroleum refineries to convert high-boiling, high-molecular weight hydrocarbon fractions of petroleum crude oils to more valuable gasoline, olefin gases, and other products. To achieve an effective FCC process, higher boiling fractions of crude oil is first atomized and then fed to a FCC riser reactor. The atomization process generally involves interaction of pressurized liquid feed, such as higher boiling fractions of crude oil, and gas, such as steam, that breaks the liquid into very fine droplets. The atomized droplets are discharged into the FCC riser reactor for the cracking reactions. A high pressure atomization device is one of important hardware used for the FCC process. Conventionally, a spray nozzle is used to carry out the high pressure atomization process. The high pressure atomization process involves the pressurized liquid feed with high jet velocities to be discharged into low pressure gas/liquid atmosphere through orifices. Due to differential pressure, pressure energy is converted to kinetic energy leading to liquid atomization. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference the same elements.

[0004] Figure 1 illustrates a schematic representation of a spray nozzle assembly in accordance with the present invention mounted within the wall of a riser of a catalytic cracking reactor.

[0005] Figure 2 illustrates a schematic representation of an enlarged longitudinal section of the spray nozzle assembly.

[0006] Figure 3 illustrates a schematic representation of an enlarged transverse section of the spray nozzle taken at an impingement plate of the spray nozzle.

DETAILED DESCRIPTION

[0007] The present subject matter relates to a spray nozzle assembly to be used in Fluidized Catalytic Cracking Process (FCC). Conventional spray nozzles typically include a conduit which defines a mixing chamber. Liquid feed, for example, higher boiling fractions of crude oil, and pressurized gas, for example, steam, are introduced within the mixing chamber such that the steam will shear droplets of the higher boiling fractions of crude oil to achieve atomization. To improvise a liquid atomization within the mixing chamber, an impingement pin is used. The impingement pin extends into the mixing chamber and defines liquid impingement surface on a center line of the mixing chamber in diametrically opposed relation to a liquid inlet. The liquid inlet is provided to allow a pressurized liquid stream to enter the mixing zone. The pressurized liquid stream impinges against the impingement pin, and is transversely dispersed. Across the dispersed liquid stream, a pressurized gas stream from a gas inlet is directed. Interaction between the liquid stream and the gas stream causes shearing of the liquid into fine droplets. Force of the gas stream further causes the sheared liquid droplets within the mixing chamber to flow outwardly through an elongated tubular barrel. The elongated tubular barrel is commonly disposed within a wall of the catalytic reactor riser, such that a spray tip nozzle at a downstream end of the elongated tubular barrel discharges the liquid in a predetermined pattern within the catalytic reactor riser. In one example of the predetermined pattern, the liquid may get discharged in a flat fan spray pattern. Within the riser, a catalyst is mixed with the atomized liquid droplet to cause a FCC process. To achieve optimum performance of the FCC process, the spray tip nozzle must spray the liquid as very fine liquid droplets. For effective break up of the liquid in very fine liquid droplets, the gas stream must be of a very high volume and high pressure, approximately around 110 psi, and further, even the liquid pressure must be kept at the same or greater pressure than the gas stream pressure to create differential pressure within the mixing zone.

[0008] Such spray nozzles are designed such that liquid flow, for example liquid hydrocarbon flow, must travel through the mixing chamber before impacting the impingement pin. Traveling distance is half of a diameter of the mixing chamber. For example, a spray nozzle with the mixing chamber of diameter of about four inches, liquid hydrocarbon flow has to travel the mixing chamber about two inches. In such nozzles with a large diameter of the mixing zone, the liquid hydrocarbon flow stream may tend to impact the impingement surface of the impingement pin partially. A reason behind the partial impact is that the liquid hydrocarbon flow has to travel significant distance through the mixing chamber, and it is subjected to heavy cross flow of the stream before impacting the impingement surface. The heavy cross flow of the stream further causes a shift in the liquid flow stream away from a center of the impingement surface. Magnitude of the shift depends upon the velocities of the pressurized stream and liquid flow streams for a particular spray nozzle. The shift prevents the liquid hydrocarbon flow from fully impacting the impingement pin, and the magnitude of the shift determines the portion of the liquid hydrocarbon flow that will impact the impingement pin. The partial impingement results in larger droplet size of the liquid hydrocarbon that adversely affects the spray performance. [0009] For eliminating such shifts of the liquid flow introduced in the mixing chamber, in one example, pressure of the liquid flow may be increased. To increase the pressure, process pumps with larger and higher pressure handling capacity are required. Such pressure pumps, however, are expensive to operate. Additionally, such spray nozzles, if operated at lower pressure, are subject to poor spray performance and clogging, particularly, when spraying heavier crude oils. In another example, more steam energy is used to atomize the pressurized liquid. Such arrangement, however, is subject to higher consumption of water and energy. [0010] The present subject matter presents a spray nozzle assembly that is adapted for more effective and optimized liquid atomization and is to improvised spray performance in catalytic cracking reactors. According to one embodiment of the present subject matter, the spray nozzle assembly includes two conduits, referred as an inner conduit and an outer conduit. [0011] According to the embodiment, the inner conduit is a tubular member to provide a passageway to a pressurized liquid flow there through. The inner conduit includes a liquid inlet to allow the pressurized liquid feed flow to enter into the inner conduit from a liquid feed supply. In one example, the liquid inlet may be fixedly mounted on an upstream end of the inner conduit. In another example, the liquid inlet may be an integral part of the inner conduit.

[0012] The inner conduit further includes an annulus which is an elongated tubular hollow section to provide a passageway for the liquid flow. When the pressurized liquid feed, entered through the liquid inlet, passes through the passageway, momentum may get induced into the liquid flow in direction of a downstream end of the inner conduit. At a downstream end of the annulus, a first set of discharge orifices is disposed to allow exit of the liquid feed flow. A part of the liquid feed flow is then discharged through the discharge.

[0013] The annulus then directs the liquid feed flow in axial direction towards the downstream end. At the downstream end of the annulus, another tubular hollow section is attached, referred as an accelerating zone. The accelerating zone is a tubular zone which is extension of the annulus and extended towards the downstream end of the inner conduit. The accelerating zone is of a smaller diameter than the annulus. Therefore, the accelerating zone increases velocity of the liquid flow coming out of the annulus. A second set of orifices is disposed at a downstream end of the accelerating zone to allow discharger of a part of the accelerated liquid flow. In one example, a diameter of the second set of orifices is smaller than a diameter of the first set of orifices.

[0014] Remaining part of the accelerated liquid feed flow forms a streamline flow which gets discharged through a third set of orifices disposed at a closed downstream end of the inner conduit. A diameter of the third set of orifices is smaller than the diameter of the second set of orifices.

[0015] The liquid feed flow, while passing through the annulus and the accelerating zone, gains velocity and then gets discharged through a plurality of sets of discharge orifices. Increased velocity and discharger of the liquid flow through small orifices results in reduction in size of droplets of the liquid feed flow, achieving a first level of atomization thereby. Discharged droplets are discharged in a mixing zone of the outer conduit of the spray nozzle to achieve a second level of atomization.

[0016] The outer conduit is an elongated tubular member enclosing the inner conduit. The outer conduit defines the mixing zone which is a hollow tubular section that provides a passageway where the droplets of the liquid feed flow discharged from the discharge orifices can interact with a pressurized gas stream. At an upstream end of the outer conduit, a gas inlet is placed to allow the pressurized gas stream to enter inside the mixing zone. In one example, the gas inlet is fixedly mounted on an outer side of a wall of the spray nozzle. In another example the gas inlet is an integral part of the outer conduit formed at outer side of the wall of the outer conduit. In accordance with one embodiment, one or more jet tubes are placed within the mixing zone, particularly, between an outer side wall of the inner conduit and an inner side wall of the outer conduit to form a passage for the pressurized gas stream coming from the gas inlet in order to increase velocity of the gas stream.

[0017] According to the embodiment, discharged droplets from the plurality of sets of discharge orifices are dispersed in the mixing zone for sufficient residence time for proper mixing of the liquid feed and the gas stream and for further shearing of the droplets of the liquid feed. The shearing of the droplets results in reduction in size of the droplets, and thus, achieving the second level of atomization of the liquid feed. The atomized liquid flow is then directed to an impingement wall for further atomization. The impingement wall is a ring placed perpendicular to the surface of the outer conduit. The impingement wall includes slit type discharge orifices. In one example, a plurality of discharge orifices is rectangular in shape having sharp inner edges to shear off the liquid droplets further prior to final atomization. The impingement wall provides a third level of atomization. [0018] According to the embodiment, the atomized liquid flow is directed towards a spray nozzle tip which is a downstream end of the spray nozzle. In one example, a plurality of discharge orifices is disposed at the spray nozzle tip in predetermined manner. The plurality of orifices at the spray nozzle tip discharges the atomized liquid droplets, resulting in further atomization of the droplets. Thus, a fourth level of atomization is achieved. The fourth level of atomization enables discharger of the finest droplets of the liquid in a predetermined pattern.

[0019] According to the present embodiment, the plurality of sets of discharge orifices, where diameter of each set of the discharge orifices is predetermined, are disposed at respective specific location at a certain angle to increase velocity of the liquid feed flow in predetermined manner, and to discharge droplets of predetermined size, where the discharger results in reduction in size of the droplets. Further, when the predetermined velocity and the size of the droplets are mixed with the gas stream, the mixing results in reduction of viscosity of the mixed flow. Due to the reduced viscosity, the droplets of the liquid feed can be sheared effectively, in turn, achieving further reduction in the size of the droplets. Thereafter, when the droplets impinges on the impingement wall, the impingement results in yet further reduction in size of the droplets. The discharge orifices with sharp inner edges shears the droplets further, reducing the droplets significantly. Finally, the discharge orifices at the spray nozzle tip shears the droplets to achieve final reduction in the size of the droplets.

[0020] An arrangement of selectively determined size, number, and placement of the discharge orifices, and similarly, selectively determined length and diameter of the inner conduit and the outer conduit, respectively, results in effective and optimized multi- staged atomization of liquid without consuming large steam energy, and further eliminating a need of large and expensive pressure pumps.

[0021] Figure 1 illustrates a schematic of a spray nozzle assembly 10 in accordance with the conventional mounting of the spray nozzle at an insulated wall 11 of a fluidized catalytic reactor. The spray nozzle assembly 10 is of a tubular shape and fixed in a tubular sleeve 12. The tubular sleeve 12 is vertically fixed within the insulated wall 11 at an acute angle to the insulated wall 11. A vertical column is provided to discharge atomized liquid feed upwardly into a riser. A support flange 15 is attached to an outwardly extending flange 14 of the tubular sleeve 12. The support flange 15 is to secure the spray nozzle assembly 10. A catalyst to be used in a fluidized catalytic cracking (FCC) process rises vertically within the insulated wall 11. The catalyst comes in contact with the atomized liquid feed sprayed by the spray nozzle assembly 10. Reaction between the catalyst and the atomized liquid feed causes the FCC process. [0022] Figure 2 illustrates a spray nozzle assembly 10. According to the present embodiment, the spray nozzle assembly includes an inner conduit 50 which is a tubular hollow part that extends in direction of a downstream end of the spray nozzle along a central axis 51 for providing a passageway for a liquid feed flow. In one example, the inner conduit 50 may have an upstream outwardly extending annular flange 55 which is clamped between a shoulder defined by an annular end 38 of a fitting 40 and the downstream end of a liquid inlet orifice 45 mounted within the fitting 40.

[0023] The inner conduit includes a liquid inlet 22 mounted at an upstream end of the inner conduit 50 to let the liquid feed enter into the inner conduit and flow there through. In one example, the liquid inlet 22 may be fixedly mounted on the inner conduit 50. In another example, the liquid inlet 22 may form an integral part of the inner conduit 50. The liquid inlet 22 includes the liquid inlet orifice 45 of a predetermined diameter. The liquid inlet 22 is mounted such that a liquid feed supply is connected to an upstream end of the liquid inlet 22, and the supplied liquid feed then passes through the orifice member 45. The orifice member 45 is to provide a liquid inlet passage through which the liquid feed is accelerated. In one example, the orifice member 45 may have a conical entry section that accelerates the pressurized liquid feed stream through an orifice member passage 46. [0024] The inner conduit 50 has an annulus 52, a tubular member that provides a passageway to the liquid feed entered from the liquid inlet 22. The annulus 52a has a diameter larger than a diameter of the liquid inlet orifice 45 so that unimpeded flow of the liquid feed can enter into the inner conduit 50. Flow of the liquid feed passing through the annulus is directed with increased velocity towards the downstream end of the annulus. A first set of discharge orifices is disposed at the downstream end of the annulus to discharge droplets of liquid feed into the mixing zone 20. The first set of discharge orifices 57 extends radially outwardly with an angle about 30-90□ to the central axis 51 of the mixing zone 20. The increased velocity of the flow and small discharge passage of the first set of discharge orifice 57 cause reductions in size of the droplet of the liquid feed, achieving a first level of atomization.

[0025] The unimpeded flow of remaining droplets of the liquid feed flow is then channeled into a smaller passage section, referred as an accelerated zone 52b. The unimpeded flow from the annulus 52a enters into the accelerating zone 52b. The accelerating zone increases velocity of the unimpeded flow further in direction of a downstream end of the accelerating zone. The second set of discharge orifices 58 is disposed at the downstream end of the accelerating zone 52b and extends radially outwardly with an angle about 30-90□ to the central axis 51 of the mixing zone 20. A part of the accelerated liquid feed flow, passing through the accelerating zone 52b, is discharged through the second set of discharge orifices 58. Accelerated velocity and small discharge passage of the second set of discharge orifice 58 cause reductions in size of the droplets of the accelerated liquid feed, achieving a first level of atomization of the accelerated liquid feed. [0026] By the time the liquid feed flows through the annulus 52a and the accelerating zone 52b, impeded droplets of the liquid feed flow with increased velocity are discharged through the first set of the discharge orifices, and further, the unimpeded droplets of the accelerated liquid flow with further increased velocity are discharged through the second set of the discharge orifices. After discharging, remaining droplets of the liquid flow form a streamline flow which is discharged through a third set of discharge orifices 54. The third set of discharge orifices 54 is disposed at a closed downstream end of the accelerating zone 52b for discharging the droplets of the streamlined liquid flow. The droplets discharged through the plurality of sets of the discharge orifices achieve significant reduction in size. Thus, the liquid feed flow achieves the first level of atomization on discharger of the droplets through the plurality of sets of the discharge orifices.

[0027] The spray nozzle assembly 10 further includes an elongated tubular member 17, referred as an outer conduit. At an upstream end, the outer conduit defines the mixing zone 20 and has a gas inlet 21. The outer conduit is further provisioned with an elongated barrel extension zone 24 that communicates with the mixing zone 20. A spray tip 25 has a plurality of discharge orifices and is supported at a downstream end of the outer conduit 17 within the insulated wall 11 for discharging and directing the atomized liquid spray. [0028] According to the present embodiment, the liquid inlet 22 is also attached to the outer conduit 17 at its upstream end for securing the spray nozzle assembly 10. The liquid inlet 22 also includes the fitting 40. The fitting 40 has a mounting flange 41 to secure a supply line 42. An upstream end of the supply line 42 is coupled to the liquid feed supply, and a downstream end of the supply line 42 is coupled to a downstream cylindrical section 44. The downstream cylindrical section 44 secures an upstream axial end of the outer conduit 17. Ends of the fitting 40 and the outer conduit 17 are welded for securement.

[0029] In accordance with the present embodiment, the gas inlet 21 is disposed at a side wall of the outer conduit 17. The gas inlet 21 is provided to allow a gas stream, for example, steam, to enter into the mixing zone 20. In one example, the gas inlet 21 is fitted on the side wall of the outer conduit using a fitting 30. The fitting 30 includes a mounting clamp 31 to secure a supply line 32. An upstream end of the supply line 32 is coupled to a steam or gas supply and a downstream end of the supply line 32 is coupled to a counter bore section 34 which fits within an opening 35 of the outer conduit 17. The counter bore section 34 is formed with an inwardly tapered conical side wall for securing the fitting 30 at the side wall of the outer conduit 17 by appropriate welding. To communicate through the outer conduit 17, the fitting 30 provides a central flow passageway 36 with a steam inlet passage section 36a.

[0030] As describes earlier, the gas stream is mixed with the liquid feed discharged from the plurality of sets of the discharge orifices in the mixing zone 20. In one example, a plurality of jet tubes 80 is placed within the mixing zone to increase velocity of the gas stream. Diameter of the jet tubes is smaller than diameter of the gas inlet, specifically, 1/8* to half of the diameter of the gas inlet. The mixing zone 20 provides sufficient residence time for proper mixing of the liquid feed and the gas stream that result in effective shearing of the droplets of the liquid feed. The shearing of the droplets results in significant reduction in the size of the droplets. Thus, the droplets of the liquid flow achieve a second level of atomization. [0031] The mixed flow of the gas stream and the liquid feed is then directed towards an impingement wall 64 for further atomization. The impingement wall 64 is a ring placed about perpendicular to the surface of the outer conduit. The droplets discharged through the third set of discharge orifices are mixed with the gas stream in the mixing zone, and further are directed towards an impact surface 66 of the impingement wall 64. The impingement wall 64 includes slit type discharge orifices 65. In one example, the plurality of discharge orifices 65 is rectangular in shape having sharp inner edges to shear off the liquid droplets further prior to the final atomization. The impingement wall 64 provides a third level of atomization.

[0032] According to the embodiment, the atomized liquid flow is directed towards a spray nozzle tip which is a downstream end of the spray nozzle. In one example, a plurality of discharge orifices is disposed at the spray nozzle tip 25 in predetermined manner. The plurality of orifices 26 at the spray nozzle tip discharges the atomized liquid droplets, resulting in further atomization of the droplets. Thus, a fourth level of atomization is achieved. The fourth level of atomization enables discharger of the finest droplets of the liquid in a predetermined pattern.

[0033] Figure 3 illustrates a cross section of the spray nozzle taken at an impingement wall of the spray nozzle. The impingement wall 64 forms an outer circular boundary to accommodate a plurality of discharge orifices 65. The plurality of discharge orifices are of rectangular slit type shape having sharp inner edges to shear off the droplets of the droplet passing through the plurality of discharge orifices 65. An impact surface 66 forms a center of the impingement wall 64.

[0034] According to the one aspect of the embodiment, decreasing size of the diameter of the inner conduit in direction of the liquid feed flow, increases velocity of the liquid feed flow. As per another aspect of the embodiment, utilization of the jet tubes having relatively smaller diameter than the gas inlet significantly increases velocity of the gas stream. [0035] According to another aspect, the gas inlet 21 is aligned precisely with the plurality of sets of discharge orifices (57, 58, 54) such that the gas inlet directs the gas stream over the liquid feed flow for direct shearing and atomizing the liquid feed flow effectively. Combination of the increased velocities of the streams and energy of the gas stream reduces the viscosity of the mixed flow. The present embodiment increases atomization efficiency by enabling the spray nozzle assembly to be operated at low liquid pressure, such as 60 psi, which is nearly 60 -70% of the pressure requirement of conventional catalytic cracking spray nozzle assemblies. The concentration and the focused direction of the gas stream passing through the jet tubes reduce quantity of the pressurized gas energy required for effective atomization. The present embodiment is effective for breaking up even heavier crude oils, such as petroleum bottoms and resides, without clogging or plugging of the nozzle components.

[0036] The present simple and durable embodiment of the spray nozzle assembly results in effective, optimum, and relatively inexpensive atomization of the liquid feed for FCC process.

Claims

A nozzle assembly to use in a fluid catalytic cracking unit comprising: an inner conduit (50) for accelerating a liquid feed comprising: a liquid inlet (45), coupled to an upstream end of the inner conduit (50), for enabling the liquid feed to enter into the inner conduit (50); an annulus (52), coupled to a downstream end of the liquid inlet (45), for providing a passageway for flow of the liquid feed, wherein the annulus is a tubular member; an accelerating zone (52b), coupled to a downstream end of the annulus (52), for accelerating the flow of the liquid feed, wherein the accelerating zone is a tubular member; and a plurality of sets of discharge orifices (57, 58, 54), disposed at the downstream end of each of the annulus (52), and the accelerating zone (52b), for discharging the accelerated liquid feed; and an outer conduit (17) enclosing the inner conduit (50) to create a mixing zone (20), wherein the mixing zone (20) is a hollow portion between an upstream end of the outer conduit (17), and wherein a flow of pressurized gas and the flow of the liquid feed discharged from the plurality of sets of discharge orifices (57, 58, 54) of the inner conduit (50) are mixed, the outer conduit comprising: a gas inlet (21), fitted on a wall at the upstream end of the outer conduit (17), for directing the flow of pressurized gas into the mixing zone (20); an impingement plate (64), fixed along a central axis (51) of the mixing zone (20) at the downstream end of the outer conduit (17), for impinging particles of a mixed flow of the pressurized gas and the liquid feed, and for discharging the impinged particles at a closed downstream end of the outer conduit (17); and a plurality of discharge nozzle tip orifices (26), disposed on a circular wall at the closed downstream end of the outer conduit (17), for atomizing the particles discharged by the impingement plate and discharging the atomized particles in a predetermined pattern.

2. The nozzle assembly as claimed in claim 1, wherein a diameter of the annulus is of bigger size than a diameter of the accelerating zone.

3. The nozzle assembly as claimed in claim 1, wherein the inner conduit has impingement surface, wherein the liquid feed is directed towards the impingement surface through the accelerating zone.

4. The nozzle assembly as claimed in claim 3, wherein the impingement surface is perpendicular to the central axis of the mixing zone against which pressurized liquid is directed.

5. The nozzle assembly as claimed in claim 3, wherein a first set of discharge orifices amongst the plurality of sets of discharge orifices of the inner conduit is placed at the downstream end of the annulus with an angle about 30-90□ with respect to the flow direction of the liquid feed.

6. The nozzle assembly as claimed in claim 3, wherein a second set of discharge orifices amongst the plurality of sets of discharge orifices of the inner conduit is placed at the downstream end of the accelerating zone annulus with an angle about 30-90□ with respect to the flow direction of the liquid feed.

7. The nozzle assembly as claimed in claim 3, wherein a third set of discharge orifices amongst the plurality of discharge orifices of the inner conduit is placed near to the impingement surface about perpendicular to the central axis of the mixing zone.

8. The nozzle assembly as claimed in claim 1, wherein the outer conduit is a hollow cylindrical tubular member.

9. The nozzle assembly as claimed in claim 1, wherein the impingement plate is of a circular shape having sharp inner edges.

10. The nozzle assembly as claimed in claim 9, wherein the impingement plate includes a plurality of orifices placed on the impingement plate, and wherein the plurality of orifices are rectangular in shape, extending radially from center of the impingement plate towards a wall of the outer conduit.

11. The nozzle assembly as claimed in claim 9, wherein the impingement plate is integrated with an impingement surface for causing impingement of droplets discharged by the third set of discharge orifices of the inner conduit.

12. The nozzle assembly as claimed in claim 1, wherein a plurality of jet tubes are placed between an outer wall of the annulus of the inner conduit and an inner wall of the outer conduit for increasing velocity of the pressurized gas flow entered through the gas inlet.