ANNULAR NOZZLE AND PROCESS FOR ITS USE

Abstract: A synthetic or fuel gas mixture containing hydrogen and carbon monoxide is made by the partial oxidation in a free-flow­ ing hollow reactor of a slurry of solid carbonaceous fuel in a liq­ uid carrier admixed with a gas containing free oxygen using a nozzle in which an annular slurry stream is enveloped between central and annular streams of high velocity gas. A uniform atomized admixture of solids, liquids and gases is formed by impinging the annular slurry stream on a downstream nozzle diffuser, and then transported through an exit orifice at an ac­ celerated velocity to further atomize the admixture. The nozzle preferably has a slurry passageway (32) formed of two elon­ gate segments (32a, 32b), the upstream segment (32a) being of greater cross-sectional area than the downstream segment (32b). The nozzle also is of general use in mixing a slurry with a gas.

Description: The present invention concerns the production of synthetic gas or fuel gas containing hydrogen and carbon monoxide which is formed by partially oxidizing a slurry of solid carbonaceous fuel and a carrier liquid admixed with a gas containing free oxygen in a hollow free-flowing reactor. More particularly, this invention concerns an improved burner nozzle for admixing the slurry and oxygen-containing gas, and then introducing the admixture into a reactor. Three basic processes have been developed for the gasification of carbonaceous materials. They are the fixed bed process, fluidized bed process, and the suspension or entrained process. The efficiency of the entrained process, with which the present invention is concerned, is significantly affected by the degree of mixing of reactants prior to carrying out the partial oxidation reaction leading to gasification. In the case where a slurry of a finely divided carbonaceous fuel in a carrier liquid is admixed with an oxygen-containing gas, it is very important that the reactants are uniformly mixed and atomized into very fine droplets at the time they are vaporized and then ignited to form a gaseous product. Annular-type burner nozzles have been employed for introducing an admixture of slurry and oxygen-containing gas into a reactor. For example, annular-type burners are shown in US-A-4,364,744 and US-A-4,443,230. Problems that have been addressed with such burner nozzles include mixing to provide proper distribution of the fuel and oxygen in the admixture, atomization of the admixture, stability of burner nozzle operation, reduction of localized overheating in the reactor and burner nozzle, and reduction of mechanical wear of the burner nozzle. In addition to these problems, slurries containing a high concentration of divided solids also tend to plug or partially plug annular passageways as they are transported through the burner nozzles. US A-4,443,230 discloses the partial oxidation of a slurry of carbonaceous fuel using a nozzle through which four feedstreams are simultaneously introduced into a reactor. The nozzle has a central conduit coaxially surrounded by three concentric annular conduits. All four conduits are closed at their upstream ends except for inlets for the respective feedstream and are open at their downstream ends. The carbonaceous fuel slurry is the feedstream to the innermost of the annular conduits and the other three feedstreams are oxygen-containing gas. The central conduit and innermost annular conduit both converge near their downstream ends to terminate in cylindrical portions which discharge their respective feedstreams in the axial direction. The outer two conduits converge at their downstream ends and, depending upon the embodiment, can discharge their respective feedstreams in or towards the axial direction. The tips of the three annular conduits can be progressively retracted to provide a diverging frusto-conical discharge zone in which some mixing of the feedstreams may take place. However, most of the mixing takes place in the reactor. In general, the present invention provides an improved burner nozzle and process for making a synthesis gas or fuel gas mixture containing hydrogen and carbon monoxide by the partial oxidation of a slurry of solid carbonaceous fuel in a liquid carrier admixed with a gas containing free oxygen, the partial oxidation occuring in a free-flowing hollow reactor. By means of the burner nozzle, the slurry and oxygen-containing gas are admixed, atomized and introduced into the reactor. The gas is produced in the reactor at a temperature of from about 1700°F (930°C) to about 3500°F (1930°C) and a pressure from about atmospheric to about 3500 pounds per square inch (0.1 to 24 MPa). Processes and reactors for producing such a gas are generally illustrated and described in U.S. Patents 2,716,598; 3,607,156; and 3,607,157. The raw gas produced also contains additional by-product gases such as nitrogen, carbon dioxide and hydrogen sulfide, as well as particulate matter, which usually requires additional processing to remove the same before final use of the product gas. An inorganic slag by-product may also be produced in the reactor along with the product gas. One embodiment of the present invention provides an improved process for making a gas mixture containing hydrogen and carbon monoxide by the partial oxidation of a slurry of solid carbonaceous fuel in a liquid carrier admixed with a gas containing free oxygen, the partial oxidation occurring in a free-flowing hollow reactor, which process comprises: (a) passing a first gas stream containing free oxygen through a first passageway formed by a central conduit of a burner with an exit discharge velocity from about 75 feet per second (23 m/s) to about sonic velocity, the burner nozzle including spaced coaxial second and third conduits surrounding the central conduit forming a second annular passageway between the central and second conduits and a third passageway between the second and third conduits, the first, second and third passageways being closed at their upstream ends wherein inlets are provided for a gas feedstream and a slurry feedstream and open at downstream discharge ports; (b) simultaneously passing a second gas stream containing free oxygen through the third annular passageway with an exit discharge velocity from about 75 feet per second (23 m/s) to about sonic velocity and a stream of the slurry through the second annular passageway with an exit discharge velocity from about 1 to about 50 feet per second (0.3 to 15 m/s); (c) impinging the second gas stream and stream of slurry on a converging surface of a nozzle diffuser, whereby the stream of slurry and first and second gas streams are simultaneously mixed by the impact of the slurry on the converging surface and by the shearing action of the first and second gas streams to produce a uniformly dispersed atomized admixture of finely divided solid carbonaceous fuel, liquid carrier and gas containing free oxygen; (d) passing the admixture through an elongate exit orifice at an accelerated velocity of from about 100 feet per second (30 m/s) to about sonic velocity to further atomize the admixture before it enters the reactor; and (e) reacting the admixture in the reactor to form the partially oxidized gas mixture containing hydrogen and carbon monoxide. A further embodiment of the present invention provides a burner nozzle for a free flowing hollow reactor used to make a gas mixture containing hydrogen and carbon monoxide by a process of partially oxidizing a slurry of solid carbonaceaus fuel in a liquid carrier admixed with a gas containing free oxygen comprising, a central conduit forming a central passageway for transporting a gas stream containing free oxygen; a second spaced coaxial conduit forming a second annular passageway between the central and second conduits for transporting a stream of slurry; a third spaced coaxial conduit forming a third annular passageway between the second and third conduits for transporting a second gas stream containing free oxygen; the first, second, and third passageways being closed at their upstream ends wherein inlets are provided for a gas feedstream and a slurry feedstream and open at downstream discharge ports formed by the termination of the central, second, and third conduits; a nozzle diffuser interconnecting with and disposed near the end of the third conduit, and in a juxtaposed position downstream from the discharge ports of the central and second passageways, the diffuser having a converging surface on which the slurry stream and second gas stream impinge to simultaneously mix the slurry and gas streams by impact of the slurry on the converging surface and by the shearing action of the first and second gas streams to produce a uniformly dispersed atomized mixture of finely divided solid carbonaceous fuel; and an elongate exit orifice inter-connected with the diffuser through which the admixture of slurry and gas containing free oxygen is transported at an accelerated velocity into the reactor. Suitably, the second passageway formed by the central and second conduits includes a first elongate segment and a second elongate segment, the first segment extending from the slurry feed inlet and converging into the second segment which in turn extends to its discharge port formed by the termination of the central and second conduits, the cross-sectional area of the first segment being substantially larger than the cross-sectional area of the second segment thereby providing a pressure of the slurry stream in the first segment which is substantially uniform throughout the annular area of the first segment at the point where it converges and interconnects with the second segment. The present invention also provides an improved plug resistant nozzle which can be used in other applications such as their use as spray nozzles during aeration of waste sluge in waste disposed plants. The nozzle has been designed to provide an efficient and uniform admixture of a slurry having a high concentration of finely divided solids with a gas while, at the same time, reducing the tendency of such a concentrated slurry to partially or completely plug annular passageways in the nozzle. The nozzle of the present invention may also be used in other applications where nozzles are required to handle slurries having a high concentration of finely divided solids that must be uniformly admixed with a gas, as for example, in the aeration or incineration processes of a waste disposal plant. In a preferred embodiment of this invention, means are provided to reduce plugging by the separation of solids in the slurry passageways and providing uniform flow over the entire passageway cross-section, which means include maintaining a uniform annular pressure in the annular slurry passageways. This characteristic makes the nozzle not only useful as a gasification burner nozzle, but also for other nozzle applications as well. The present burner nozzle comprises a central conduit with coaxial second and third conduits surrounding the central conduit which form a central passageway and two annular passageways. The central and annular passageways are closed at their upstream ends wherein inlets are provided for gas and slurry feedstreams, and are open at their downstream discharge ports formed by the termination of the central and annular conduits. The burner nozzle includes a nozzle diffuser interconnecting with and disposed near the end of the third conduit which is in a juxtaposed position downstream from the discharge ports of the central and first annular passageway. The burner nozzle also includes an elongate exit orifice interconnected with the diffuser. During operation of the burner nozzle a gas feedstream and slurry feedstream are introduced into upstream inlets. The gas feedstream is split and passes through the central axial passageway and through the outer annular passageway while the slurry feedstream simultaneously passes through the middle annular passageway between the central passageway and outer annular passageway, thereby enveloping the annular slurry stream between a central axial stream of oxygen-containing gas and an outer annular stream of the same gas. The slurry stream and gas streams are discharged through the discharge parts of their respective passageways and the slurry stream and outer gas stream are then impinged on a converging surface of the nozzle diffuser, whereby the slurry stream and gas streams are mixed by the impact of the slurry on the converging surface of the diffuser and the shearing action of the gas streams to produce a uniformly dispersed atomized admixture of finely divided solid carbonaceaous fuel liquid carrier and gas containing free oxygen. This admixture is then passed through an elongate exit orifice at an accelerated velocity to further atomize the admixture before it enters the reactor. These and other aspects of the invention will be apparent to those skilled in the art from the foregoing description and from the more detailed description which follows, including the following description of the drawings. FIGURE 1 is a partial longitudinal cross-section illustrating a burner nozzle made in accordance with the principles of the present invention; FIGURE 2 is a transverse cross-section taken at line A-A of FIGURE 1 illustrating an embodiment of the burner nozzle; FIGURE 3 is a partial longitudinal cross-section illustrating another preferred burner nozzle made in accordance with the principles of the present invention; and FIGURE 4 is a transverse cross-section taken at line B-B of FIGURE 3 illustrating an embodiment of the burner nozzle. The following description, by reference to the drawings, illustrates the manner in which the principles of the present invention are applied, but it is not to be construed as in any sense limiting the scope of the invention. More specifically, referring to Figures 1-4, burner nozzles 10 and 30 are illustrated. Burner nozzle 10 includes a central conduit 1 forming a passageway 4; a second coaxial annular conduit 2 forming an annular passageway 5; and a third coaxial annular conduit 3 forming an annular passageway 6. The passageway 5 is held in a spaced relationship with passageways 4 and 6 by spacers 17. Spacers 17 should be kept to a minimum to avoid unnecessary disruption of the slurry stream flow in passageway 5. The passageways 4, 5 and 6 are closed at their upstream ends by walls 7a, 7b and 7c wherein inlets 15 and 16 are provided for slurry and gas feedstreams. A distribution chamber 18 is provided to uniformly transport the slurry feedstream into the annular passageway 5. The passageways 4, 5 and 6 have discharge ports 8a, 8b, and 8c at their downstream ends formed by the termination of conduits 1, 2 and 3. A tube 19 is used to provide open communication between passageways 4 and 6 for the transport of the gas feedstream. The burner nozzle 10 also includes a nozzle diffuser 9 having a converging surface 9a for impinging the slurry passing through passageway 5 and the gas passing through passageway 6, and an elongate exit orifice 11 to transport the admixture of slurry and oxygen-containing gas into the reactor at an accelerated velocity. In this embodiment the diffuser 9 is a continuing extension of conduit 3. As a result of the harsh environment to which the diffuser 9 is subjected, i.e., high temperatures, chemical attack, and mechanical wear, it is an advantage, if not a necessity, to construct the diffuser 9 from a material, for example, which has high corrosion resistance, toughness, and wear characteristics, such as tungsten carbide, or silicon carbide, whereas the remainder of the nozzle 10 can be constructed of a metal such as stainless steel. It is also an advantage to provide a water jacket 12 having a water inlet 13 and outlet 14 to cool the diffuser 9 and walls 11a of the orifice 11. The orifice 11 of nozzle 10 has a cylindrical design, but may have diverging or converging walls 11a. Also, although not a critical design requirement, the length of the orifice 11 is beneficially longer than its diameter to provide for additional time in a zone of high shear for the slurry/gas mixture, and for a high degree of atomization of the admixture transported into the reactor. Referring to Figures 3 and 4, another embodiment of the present invention is illustrated. Elements of burner nozzle 30 shown in Figures 3 and 4 which are like characters of reference as those shown in Figures 1 and 2 for burner nozzle 10 have the same reference numerals. Burner nozzle 30 includes modification of both the central and second annular conduit, thus changing the central gas passageway and the slurry passageway, as well as including changes in the nozzle diffuser and exit orifice. Thus, burner nozzle 30 includes annular conduit sections 31a and 31b which form an annular passageway with a first segment 32a and a second segment 32b. The cross-sectional area of segment 32a is substantially larger than the cross-section of segment 32b. The slurry feedstream from the inlet 15 is fed directly into segment 32a, thereby eliminating the need for the gas tuba 19 of nozzle 10 and allowing direct flow of the gas feedstream into passageways 4 and 6. This provides much less disruption of the slurry flow in passageway segments 32a and 32b. If necessary, fasteners 34 may be included to overcome any structure weakness. Burner nozzle 30 also includes a ceramic nozzle diffuser 33 having a converging surface 9a for impinging the slurry stream from passageway segment 32b and the gas stream from passageway 6, which diffuser 33 is held in place by conduit 3. There are many well known ceramic materials that can be used to make the diffuser 33, for example, a dense-phase alumina refractory. Use of a ceramic diffuser not only provides the diffusion surface 9a, but also insulates the nozzle from the heat produced in the reactor. As previously noted, handling highly concentrated slurries of finely divided solids in annular nozzles such as burner nozzles 10 and 30 may result in a problem of the finely divided solids separating from the liquid carrier and plugging slurry passageways. To overcome the possibility of this occuring, and to provide uniform flow across the entire cross-section of the annular flow passageway, nozzle 10 includes the distribution chamber 18 and nozzle 30 includes the combined segments 32a and 32b that form the slurry passageway. In both nozzles 10 and 30, the upstream chamber or segment of the passageway for the slurry stream has a substantially larger cross-sectional area than the downstream segment. As a specific example, a nozzle designed like nozzle 30 was constructed of metal pipe wherein the central gas stream passageway had about a three inch ( 8 cm) diameter and 16 inch ( 41 cm) length, and the first segment of the slurry passageway had an annular cross-sectional thickness of about one and one-half inches ( 4 cm) around the central passageway and a 4 inch (10 cm) length, and the second segment of the slurry passageway had an annular cross-sectional thickness of about one quarter of an inch (0.6 cm) and a 12 inch (30 cm) length. The slurry stream in the larger upstream chamber or segment provides a substantially uniform pressure throughout the annular area of the upstream segment at the point where the upstream segment interconnects with the downstream annular portion of the passageway, thus substantially reducing flow variations around the annular flowpath of the slurry stream. It has been also found that this uniform annular pressure at the point of interconnection can be substantially maintained by designing the upstream portion of the slurry passageway from the inlet downstream to the point of interconnection with the annular portion of the passageway so that the pressure drop is about 20 percent or less of the pressure drop that occurs in the annular portion of the slurry passageway downstream to its discharge port. In order to produce the desired uniformity of dispersion and atomization of the admixture of slurry and gas, it has been determined that the preferred velocities of the gas and slurry streams through the various passageways should be maintained within the following ranges. The gas stream passing through the central axial passages should have an exit discharge velocity from about 75 feet per second (23 m/s) to about sonic velocity. The gas stream passing through the outer annular passageway should have an exit discharge velocity of from about 75 feet per second (23 m/s) to about sonic velocity. The slurry stream passing through the second or middle annular passageway should have an exit discharge velocity from about 1 to about 50 feet per second (0.3 to 15 m/s). The velocity of the combined admixture of slurry and gas through the exit orifice of the nozzle into the reactor should be from about 100 feet per second (30 m/s) to about sonic velocity.

Claims: A process for making a gas mixture containing hydrogen and carbon monoxide by the partial oxidation of a slurry of solid carbonaceous fuel in a liquid carrier admixed with a gas containing free oxygen, the partial oxidation occurring in a free-flowing hollow reactor, wherein a first gas stream containing free oxygen passes through a first passageway formed by a central conduit of a burner with an exit discharge velocity from 23 m/s (75 ft/s) to sonic velocity, the burner nozzle including spaced coaxial second and third conduits surrounding the central conduit forming an annular second passageway between the central and second conduits and an annular third passageway between the second and third conduits, the first, second and third passageways being closed at their upstream ends wherein inlets are provided for a gas feedstream and a slurry feedstream and open at downstream discharge ports; a second gas stream containing free oxygen simultaneously passes through the annular third passageway with an exit discharge velocity from 23 m/s (75 ft/s) to sonic velocity; and a stream of the slurry simultaneously passes through the annular second passageway with an exit discharge velocity from 0.3 to 15 m/s (1 to 50 ft/s); characterised in that the stream of slurry and second gas stream impinge on a converging surface of a nozzle diffuser, whereby the stream of slurry and first and second gas streams are simultaneously mixed by the impact of the slurry on the converging surface and by the shearing action of the first and second gas streams to produce a uniformly dispersed atomized admixture of finely divided solid carbonaceous fuel, liquid carrier and gas containing free oxygen; the admixture passes through an elongate exit orifice at an accelerated velocity of from 30 m/s (100 ft/s) to sonic velocity to further atomize the admixture before it enters the reactor, and said admixture reacts in the reactor to form the partially oxidized gas mixture containing hydrogen and carbon monoxide. A process as claimed in Claim 1, wherein the discharge ports of the first and second passageways are located within a converging zone defined at the discharge end of the third conduit by the converging surface of the nozzle diffuser. A process as claimed in any one of the preceding claims, wherein the second conduit comprises a distribution chamber or annular segment, said chamber or segment extending from the slurry feed inlet to the, or tile remainder of the, annular second passageway and having a substantially larger cross-sectional area than the, or the remainder of the annular second passageway thereby providing a substantially uniform pressure of the slurry stream throughout the annular area where it interconnects with the, or remainder of the, annular second passageway. A process as claimed in Claim 1 or Claim 2, wherein the second passageway comprises a first elongate segment and a second annular elongate segment, the first elongate segment extending from the slurry feed inlet and converging into the second segment which in turn extends to its discharge port, the cross-sectional area of the first segment being substantially larger than the cross-sectional area of the second segment thereby providing a pressure of the slurry stream in the first segment which is substantially uniform throughout the annular area of the first segment at the point where it converges and interconnects with the second segment. A process as claimed in Claim 3 or Claim 4, wherein the pressure drop for the slurry stream from the slurry feed inlet to said point of interconnection is twenty percent or less of the pressure drop for the slurry stream from the point of interconnection to the discharge port of the second segment. A burner nozzle for a free flowing hollow reactor used to make a gas mixture containing hydrogen and carbon monoxide by a process of partially oxidizing a slurry of solid carbonaceous fuel in a liquid carrier admixed with a gas containing free oxygen, said nozzle comprising a central conduit (1) forming a central passageway (4) for transporting a gas stream containing free oxygen; a coaxially spaced second conduit (31) forming an annular second passageway (32) between the central and second conduits for transporting a stream of slurry; a coaxially spaced third conduit (3) forming an annular third passageway (6) between the second and third conduits for transporting a second gas stream containing free oxygen; the first, second, and third passageways being closed at their upstream ends wherein inlets (15,16) are provided for a gas feedstream and a slurry feedstream and open at downstream discharge ports (8) formed by the termination of the central, second, and third conduits, characterised in that the nozzle further comprises a nozzle diffuser (33) interconnecting with and disposed near the end of the third conduit, and in a juxtaposed position downstream from the discharge ports of the central and second passageways, the diffuser having a converging surface (9a) on which the slurry stream and second gas stream impinge to simultaneously mix the slurry and gas streams by impact of the slurry on the converging surface and by the shearing action of the first and second gas streams to produce a uniformly dispersed atomized mixture of finely divided solid carbonaceous fuel; and an elongate exit orifice (11) interconnected with the diffuser through which the admixture of slurry and gas containing free oxygen is transported at an accelerated velocity into the reactor. A burner nozzle as claimed in Claim 6, wherein the second passageway (32) formed by the central and second conduits includes a first elongate segment (32a) and a second elongate segment (32b), the first segment extending from the slurry feed inlet and converging into the second segment which in turn extends to its discharge port (8b) formed by the termination of the central and second conduits, the cross-sectional area of the first segment being substantially larger than the cross-sectional area of the second segment thereby providing a pressure of the slurry stream in the first segment which is substantially uniform throughout the annular area of the first segment at the point where it converges and interconnects with the second segment. A nozzle as claimed in Claim 7, wherein the cross-sectional areas of the first and second segments are proportioned to provide a pressure drop for the slurry stream from the slurry feed inlet to the point where the first segment interconnects with the second segment which is twenty percent or less of the pressure drop for the slurry stream from the point of interconnection to the discharge port of the second segment. A nozzle as claimed in any one of Claims 6, 7 and 8, wherein the discharge ports of the first and second passageways are located within a converging zone defined at the discharge end of the third conduit by the converging surface of the nozzle diffuser.

Inventors: LIPP, CHARLES W., MERRICK, DOUGLAS D., PEARSON, STANLEY R., WHITE, WILLIAM P.
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1986
Main classification: C10J3
IPC codes: C10J3, F23D99