NZ592086A - Fuel conditioning unit comprising a chamber, at least one nozzle and at least one gas port - Google Patents

Abstract

A fuel conditioning unit (100) is disclosed. The unit (100) comprises a cylindrical vaporization chamber (110) with a sidewall (112) and an end wall (160). There are plurality of nozzles (120) mounted along the sidewall (112) and in fluid communication with a liquid supply. The nozzles (120) are configured to spray liquid fluid radially inward into the chamber (110). The unit (100) further comprises at least one diluent gas port (140) that is in fluid communication with the chamber (110). The diluent gas port (140) is in fluid communication with the supply of heated inert diluent gas. The port (140) is configured to introduce the diluent gas into the chamber (110). There is at least one exit port (170) that provides a path for vaporized liquid fuel to exit the chamber (110). In use, the heated inert diluent gas supplies at least a portion of the heat required for vaporization of the liquid fuel. A mixture of the diluent gas and vaporized liquid fuel has a lower dew point than that of the liquid fuel in the absence of the diluent gas.

Description

NEW ZEALAND PATENTS ACT, 1953 Divided out of application No: 555544 Date: 8 December 2005 COMPLETE SPECIFICATION METHOD AND APPARATUS FOR CONDITIONING LIQUID HYDROCARBON FUELS We, LPP COMBUSTION, LLC, of 8940 Old AnnapoUs Road, Suite L, Columbia, Maryland 21045, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: (followed by pages 1 a) TITLE METHOD AND APPARATUS FOR CONDITIONING LIQUID HYDROCARBON FUELS

[001] This application claims priority from U.S. provisional patent application ser. no. 60/634,221 filed December 8, 2004, the content of which is incorporated fully herein by reference.

The present divisional application has been divided out of New Zealand patent application 555544 (NZ 555544). In the description in this specification reference may be made to subject matter which is not within the scope of the appended claims but relates to subject matter claimed in NZ 555544. That subject matter should be readily identifiable by a person skilled in the art and may assist in putting into practice the invention as defined in the presently appended claims.

BACKGROUND INFORMATION

[002] Low emissions from combustion devices are obtained by burning a lean mixture of fuel and air obtained by pre-mixing gaseous fuel and air. Dry Low NOx (DLN) technology gas turbines, for example, typically bum natural gas under lean, pre-mixed conditions. Liquid fuels, by contrast, are typically burned by injecting a fuel spray directly into the combustor. This results in a diffusion flame in which the fuel is burned in a locally stoichiometric fuel/air mixture and causes high emissions. Under certain conditions, burning a liquid fuel is more desirable than burning a gaseous fuel. However, it would be desirable to avoid the high emissions associated with diffusion flames when burning such liquid fuels.

SUMMARY The present invention provides a fuel conditioning unit comprising: a cylindrical vaporization chamber, the cylindrical vaporization chamber comprising a sidewall and an end wall; la (followed by page lb) a plurality of nozzles mounted along the sidewall and in fluid communication with a liquid fuel supply, the nozzles being configured to spray liquid fuel radially inward into the chamber; at least one diluent gas port in fluid communication with the chamber, the diluent gas port being in fluid communication with a supply of heated inert diluent gas, the port being configured to introduce the diluent gas into the chamber; and at least one exit port in fluid communication with the chamber, the exit port providing a path for vaporized liquid fuel to exit the chamber; wherein the heated inert diluent gas supplies at least a portion of the heat required for vaporization of the liquid fuel, and wherein a mixture of the diluent gas and vaporized liquid fuel has a lower dew point than that of the liquid fuel in the absence of the diluent gas.

Throughout this specification, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The present invention further provides a method for conditioning a liquid fuel comprising the steps of: spraying the liquid fuel into a cylindrical vaporization chamber through a plurality of nozzles mounted on a sidewall of the chamber and in fluid communication with the chamber such that the liquid fuel does not impinge on any wall of the chamber; supplying a heated diluent gas to the vaporization chamber through at least one diluent gas port in fluid communication with the chamber; and receiving a conditioned vaporized fuel gas from at least one exit port in fluid communication with the chamber, the conditioned vaporized fuel gas comprising a mixture of the diluent gas and a vaporized form of the liquid fuel, the conditioned vaporized fuel gas having a lower dew point than that of the vaporized form of the liquid fuel in the absence of the diluent gas.

[003] A method and apparatus for conditioning liquid fuels at a location external to a combustion device so that the resulting vapor phase fuel may be pre-mixed with air and burned under lean conditions, thus achieving low emissions, is described herein. Preferably, the liquid fuel is conditioned such that it may be used in a combustion configured for natural gas without modification to the combustor/fuel metering system. In one embodiment, the lb iiquid fuel is sprayed into a vaporization chamber such that the spray does not impinge on any surface. The energy for vaporization is supplied through the injection of a hot diluent such as nitrogen or oxygen depleted air. Additional heat is added through the surface of the chamber to prevent heat loss and to maintain an internal surface temperature above the boiling point of the least volatile component of the liquid. The diluent gas also serves to control the dew point of the resultant vapor phase mixture. Additional heating to augment the vaporization process in the event that the diluent flow or temperature fall below the minimum levels needed for complete vaporization is supplied by internal heaters.

[004] In another embodiment, the liquid fuel is sprayed onto a hot surface using a geometry such that the entire spray is intercepted by the surface. Heat is added through the surface to maintain an internal surface temperature above the boiling point of the least volatile component of the liquid fuel. The liquid droplets impinging on the surface are thus flash vaporized such that there is no build up of bulk liquid or a liquid film in the vaporizer. A carrier gas, such as nitrogen or air, may also be flowed through the vaporizer to control the dew point of the resultant vapor phase mixture. In some embodiments, a fuel nozzle is mounted at one end (the enclosed end) of a cylindrical chamber. The nozzle forms a hollow cone type spray with a spray angle chosen such that all of the spray impinges on the cylinder surface (in other embodiments a solid cone type spray nozzle is used). The preferred orientation is vertical, with the spray downward, so that the impingement of the spray on the walls is even. Two or more such chambers can be joined to a common manifold to accommodate higher capacities. 2 BRIEF DESCRIPTION OF THE FIGURES

[005] The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference numbers indicate identical or functionally similar elements.

[006] Figure 1 is a schematic drawing of a fuel vaporizer according to a first embodiment of the invention.

[007] Figure 2 is a schematic drawing of a single nozzle vaporizer according to a second embodiment of the invention.

[008] Figure 3 is a schematic drawing of a plurality of the vaporizers of Figure 2 joined to a common manifold according to a third embodiment of the invention.

DETAILED DESCRIPTION

[009] Various embodiments of methods and apparatuses for conditioning liquid fuels are discussed below. Specific details are set forth in order to provide a thorough understanding of the present invention. The specific embodiments described below should not be understood to limit the invention. Additionally, for ease of understanding, certain method steps are delineated as separate steps. These steps should not be understood as necessarily distinct or order-dependent in their performance unless so indicated.

[010] The complete disclosure of U.S. Patent Application Serial Number 10/682,408 (published as US 2004/0134194 A1 on July 15, 2004), which was filed October 10, 2003, and which describes methods and devices for vaporizing, mixing, and delivering liquid fuels or liquefied gases which have been pre-vaporized with a reduced oxygen content air stream for use in combustion devices, is fully incorporated herein by 3 reference. In addition, U.S. Patent Application Ser. Nos. 60/535,716, filed January 12, 2004, and 11/033,180, filed January 12, 2005 (published as US 2006/0046218 A1 on March 2, 2006), which disclose systems and methods for flame stabilization and control, are both also fully incorporated herein by reference.

[011] In some embodiments of a method and apparatus for conditioning liquids, such as hydrocarbon fuels, the liquid is sprayed into a chamber such that the spray does not impinge on any surface. The energy for vaporization is supplied through the injection of a hot diluent such as nitrogen or oxygen depleted air. Additional heat is added through the surface to prevent heat loss and to maintain an internal surface temperature above the boiling point of the least volatile component of the liquid. The diluent gas also serves to control the dew point of the resultant vapor phase mixture. Additional heating to augment the vaporization process in the event that the diluent flow or temperature fall below the minimum levels needed for complete vaporization is supplied by internal heaters. One application of the invention is the vaporization of liquid fuels, such as kerosene and heating oil, for introduction into a combustion device, such as a gas turbine. Pre-vaporizing the fuel in this manner allows the operation of the gas turbine in the lean, premixed mode, resulting in extremely low pollutant emissions.

[012] Figure 1 illustrates a fuel conditioner 100 according to such an embodiment of the invention. The fuel conditioner 100 includes a cylindrical vaporization chamber 110. Liquid fuel is sprayed into the chamber 110 through nozzles 120 mounted on the sidewall 112 of the chamber 110. The nozzles 120 are pressure atomizing spray nozzles in some embodiments. In other embodiments, the nozzles 120 may be two-fluid nozzles (such as filming or "air" blast type nozzles), in which case the diluent (or carrier) gas may enter the chamber 110 through such two-fluid nozzles. In an alternative embodiment, the nozzles are mounted on a 4 manifold which runs parallel to the axis of the cylindrical chamber and which gets installed from an end of the chamber.

[013] In some embodiments, the sidewall and/or end wail of the chamber 110 are heated. In some embodiments, heating tape or heat tracing (MI cable) (not shown in Figure 1) is used to heat the sidewall and/or end wall. As discussed above, the heating of the sidewall and/or end wall of the chamber 110 serves to prevent heat loss and maintain an internal surface temperature above that of the boiling point for least volatile component of the liquid fuel.

[014] In the embodiment of Figure 1, the nozzles 120 are arranged in rings spaced around the circumference of the cylinder, with each column of nozzles 120 supplied by one of a plurality of manifolds 130. Diluent gas is supplied through an inlet 140 that is in fluid communication with a plenum 150 formed by a space between the top end wall 160 of the chamber 110 and a perforated plate 160. The diluent gas enters the interior of the chamber 110 through perforations in the plate 160. The diluent gas is preferably a gas that has less oxygen than ambient air, such as nitrogen, steam, methane, oxygen depleted air, or exhaust gas from a combustion device. The diluent gas is preferably heated to at least the boiling point of the liquid such that the diluent gas supplies the heat required for vaporization of the liquid fuels entering the chamber 110 through the nozzles 120. As discussed above, the diluent gas also serves to lower the dew point of the vapor phase mixture. Lowering the dew point temperature is desirable so that downstream components, such as the line connecting the vaporizer to the combustion device, can be maintained at a temperature lower than that required for the initial vaporization. The use of an inert carrier gas can also serve to limit chemical reaction in the conditioner 100 and transfer lines connecting the conditioner 100 to a combustor, thus suppressing coking. Vaporized fuel exits the chamber through one or more exit ports 170 for transport to the combustion device.

[015] In alternative embodiments, the diluent gas is introduced into the chamber 110 through nozzles arranged on the sidewall of the chamber 110 and positioned, for example, between the nozzles 120 and or on one of the end walls of the chamber 110. Depending on the location and method in which the diluent gas is introduced into the chamber 110, the diluent gas may be introduced in a co-flow arrangement, a counter-flow arrangement, and/or at various angles in order to, for example, induce a swirling flow inside the chamber 110.

[016] Referring now back to Figure 1, an optional spool section 180 is attached to the chamber 110 in some embodiments. The length of the spool section 180 is chosen to increase the vaporizer residence time so that it is sufficient for complete evaporation of the fuel droplets. The spool section 180 preferably has a plurality of heating elements 190 disposed therein (two concentric rings of heating elements 190 are illustrated in Figure 1). The heating elements 190 preferably extend the length of the spool section 180, and may be electrical bayonet heaters, heat exchange tubes, or any other type of heating element. In some embodiments, each heating element 190 is provided with a separate temperature control.

[017] The spool section 180 also includes one or more exit ports 182, similar to those of the chamber 110, through which vaporized liquid may exit the spool section 182. A drain 186 passes through the end cap 184 of the spool section 180 to allow any unvaporized liquids to be removed from the conditioner 100.

[018] The spool section 180 may include a particulate collection device (not shown in Figure 1) in some embodiments. The particulate collection device controls particulate or 6 droplet carryover exiting the conditioner 100. Possible particulate control devices include mist eliminators, cyclones, and filter elements.

[019] In some embodiments, a preheater (not shown in Figure 1) is used to pre-heat the; liquid prior to entry into the chamber 110. This lowers the amount of heat needed to vaporize the liquid in the chamber 110. Preheating also lowers the viscosity of the liquid, which improves the quality of the spray produced by the nozzles 120.

[020] It should be understood that the number of nozzles 120, the length of the chamber 110 and the spool section 180 can be modified to suit desired operating conditions (e.g., volume of fuel needed, type of liquid fuel to be conditioned, etc.). Thus, the design illustrated in Figure 1 is easily scalable for a variety of operating conditions.

[021] In the embodiments discussed above in connection with Figure 1, the liquid fuel does not impinge on any interior surface. In other embodiments, such as those illustrated in Figures 2 and 3, the liquid fuel does impinge on interior surfaces of a vaporization chamber. In such embodiments, the energy for vaporization is supplied by heat transfer through the walls of the vaporization chamber. The essential design feature of a fuel conditioner operating in this manner is the match of the heat transfer rate through the walls to the heat required to vaporize the liquid. This is achieved by matching the surface area used for vaporization with the liquid flow rate and the achievable heat flow through the walls. Since the heat requirement is different in different sections of the vaporizer, the heat input may be staged with separate temperature control for each stage.

[022] Figure 2 is a schematic drawing of a single nozzle vaporizer 200 according to a second embodiment of the invention. Liquid fuel is sprayed into the vaporizer 200 through a 7 WO 2006/063126 PCT/US2005/044414 nozzle 210 mounted on the end flange 220. A carrier gas such as nitrogen or air, which is preferably pre-heated to supply some of the heat required for vaporization, is also introduced through ports 230 on the end flange 220. As with the embodiment of Figure 1, the use of a carrier gas serves two purposes: 1) to aid in removing the vapor from vaporizing chamber, and 2) to lower the dew point temperature of the vapor. Lowering the dew point temperature is desirable so that downstream components, such as the line connecting the vaporizer to a combustion device, can be maintained at a temperature lower than that required for the initial vaporization. The use of an inert carrier gas can also serve to limit chemical reaction in the vaporizer and transfer lines, thus suppressing coking. There are many possible ways to introduce the carrier gas such as, but not limited to: in each vaporizer module, in the main body of the vaporizer, in an axial direction, and in a tangential direction to induce swirl. In the vaporizer 200, the carrier gas is injected tangentially at two ports 230 to induce a swirling co-flow. ■\

[023] The resulting spray from the nozzle 210 impinges on the interior cylindrical surface 240 of the vaporizer 200, and is evaporated due to heat input through the surface and from the hot carrier gas. The surface 240 is heated by a combination of electrical heating tape 250 and band heaters 260 in this embodiment. In other embodiments, the heat input may be supplied by heat exchange with a hot liquid or gas (such as steam or hot combustion products).

[024] Figure 3 is a schematic diagram of a fuel conditioning system 300 with multiple single nozzle vaporization units 200. In order to maintain the optimum surface area to volume ratio for spray vaporization, additional capacity is obtained by grouping multiple vaporizer "legs" onto a common manifold 310. The body of the manifold 310 is also heated, 8 WO 2006/063126 PCTYUS2005/044414 in this case with heating tape 350. A rupture disc 370 is mounted on one end of the manifold 310 for safety. Vapor exits the other end of the manifold 310. [025} Several embodiments of fuel conditioning devices have been discussed above. Numerous other modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 9

Claims (19)

Claims:

1. A fuel conditioning unit comprising: a cylindrical vaporization chamber, the cylindrical vaporization chamber 5 comprising a sidewall and an end wall; a plurality of nozzles mounted along the sidewall and in fluid communication with a liquid fuel supply, the nozzles being configured to spray liquid fuel radially inward into the chamber; at least one diluent gas port in fluid communication with the chamber, the 10 diluent gas port being in fluid communication with a supply of heated inert diluent gas, the port being configured to introduce the diluent gas into the chamber; and at least one exit port in fluid communication with the chamber, the exit port providing a path for vaporized liquid fuel to exit the chamber; wherein the heated inert diluent gas supplies at least a portion of the heat 15 required for vaporization of the liquid fuel, and wherein a mixture of the diluent gas and vaporized liquid fuel has a lower dew point than that of the liquid fuel in the absence of the diluent gas.

2. The fuel conditioning unit of claim 1, wherein the at least one diluent gas port 20 comprises a plurality of diluent gas ports formed in a perforated plate located within the chamber, the perforated plate, the end wall and a portion of the sidewall forming a plenum in fluid communication with the plurality of diluent gas ports and the supply of heated diluent gas. 25

3. The fuel conditioning unit of claim 1, further comprising a spool section attached to a portion of the sidewall opposite the end wall such that the spool section forms an extension of the chamber, the spool section having a heating element disposed therein, the heating element supplying additional heat to vaporize any liquid fuel not vaporized in the portion of the chamber corresponding to the sidewall, the 30 spool section having at least one additional exit port through which any fuel vaporized in the spool section may exit the fuel conditioning unit.

4. The fuel conditioning unit of claim 3, wherein the spool section has a plurality of heating elements disposed therein. 3162406-1 10

5. The fuel conditioning unit of claim 4, wherein each of the plurality of heating elements has an individual temperature control.

6. The fuel conditioning unit of claim 3, wherein the heating element has a length 5 equal to a length of the spool section.

7. The fuel conditioning unit of claim 1, wherein at least a portion of the chamber sidewall or the chamber end wall is heated. 10

8. A method for conditioning a liquid fuel comprising the steps of: spraying the liquid fuel into a cylindrical vaporization chamber through a plurality of nozzles mounted on a sidewall of the chamber and in fluid communication with the chamber such that the liquid fuel does not impinge on any wall of the chamber; 15 supplying a heated diluent gas to the vaporization chamber through at least one diluent gas port in fluid communication with the chamber; and receiving a conditioned vaporized fuel gas from at least one exit port in fluid communication with the chamber, the conditioned vaporized fuel gas comprising a mixture of the diluent gas and a vaporized form of the liquid fuel, the conditioned 20 vaporized fuel gas having a lower dew point than that of the vaporized form of the liquid fuel in the absence of the diluent gas.

9. The method of claim 8, wherein the diluent gas is supplied to the vaporization chamber through a plurality of diluent gas ports formed in a perforated plate located 25 within the chamber, the perforated plate, the at least one end wall of the chamber and a portion of the side wall of the chamber forming a plenum in fluid communication with the plurality of diluent gas ports and the supply of heated diluent gas.

10. The method of claim 8, wherein the chamber has at least one heating element 30 disposed therein to vaporize any liquid fuel not vaporized by the heat supplied by the diluent gas.

11. The method of claim 10, wherein the at least one heating element comprises a plurality of heating elements. 11 3162406-1 Received at IPONZ on 27 July 2011

12. The method of claim 11, wherein each of the plurality of heating elements has an individual temperature control.

13. The method of claim 8, further comprising the step of heating at least a portion of a wall of the chamber.

14. The method of claim 8, wherein the diluent gas is inert.

15. The fuel conditioning unit of claim 1, wherein each of the plurality of nozzles is oriented toward a central axis of the vaporization chamber.

16. The fuel conditioning unit of claim 1, further comprising a combustor in fluid communication with the exit port, wherein the fuel conditioning unit is configured such that the mixture remains at a temperature above the dew point for the mixture until it is combusted in the combustor.

17. The method of claim 8, further comprising the step of maintaining the conditioned vaporized fuel above the dew point until the conditioned vaporized fuel is combusted in a combustor in fluid communication with the exit port.

18. The fuel conditioning unit of claim 1, the fuel conditioning unit being substantially as herein described with reference to any embodiment disclosed.

19. The method of claim 8, the method being substantially as herein described with reference to any embodiment disclosed. LPP COMBUSTION. T.T.C By the authorised agents A T Park Per 12