Vaporizing Pre-Emulsified Gasoline/Water Mixture Through an Atomizing Nozzle at Reformer Inlet

Technical Field

[0001] Operating an autothermal reformer at a near-equal steam to carbon ratio without coking is achieved by pre-emulsifying a water/gasoline mixture, such as in a high shear mixer, and passing the pre-emulsion through an atomizing nozzle, which serves, optionally with an inert bed, as a vaporizer at the inlet to an autothermal reformer; the gasoline in the mix may be desulfurized.

Background Art

[0002] Fuel cells operate on oxygen, usually derived from a flow of air, and hydrogen, which may be provided in the form of industrial grade hydrogen stored in a tank, or it may be reformate gas generated from hydrocarbon feed stock of various kinds. For mobile applications, particularly when a fuel cell power plant is to provide electric power to operate a vehicle, the use of gasoline as the hydrocarbon feed is advantageous. Typically, an autothermal reformer is chosen for generating reformate from gasoline because it is usually smaller than a catalytic steam reformer, and may process a wider variety of fuels. [0003] In order to avoid coke formation on the reformer catalyst, a high steam/carbon ratio, on the order of 2.75 to 1 is required. To achieve this, a steam generator, such as a simple burner with a steam separator, is required. In a vehicle, the steam generator is too expensive, takes up too much space, and adds too much weight to the system. Another problem in maintaining reasonably accurate carbon/steam ratios in such systems is the difficulty of accurately measuring the amount of steam being provided for mixture with the fuel. Therefore, it is desirous to eliminate the steam generator.

[0004] Elimination of the steam generator will result in a steam/carbon ratio which is nearly equal (one to one), which would result in formation of coke on the catalyst of the reformer. For simplicity, it also would be desirable to inject water and gasoline directly into the startup combustor or

a vaporizer at the inlet of the autothermal reformer. The problem is that gasoline does not mix well with water, and locally high concentrations of gasoline hydrocarbons will form coke on the catalyst at the low ^• steam/carbon ratio.

Summary

[0005] Water and a liquid hydrocarbon feed, such as gasoline or a gasoline mixture with other constituents (such as MTBE or ethanol), are pre-emulsified in an effective mixer, such as either a high shear mixer, a mechanical agitation mixer, or a long static mixer, the emulsion being fed through an atomizing nozzle with air; the mixture of hydrocarbon, water and air is heated and vaporized, optionally through an inert bed, thus providing little localized hydrocarbon excess, which in turn mitigates formation of coke in an autothermal reformer, to which the mix is fed. The raw gasoline may be fed through a desulfurizer to a clean (desulfurized) tank, which may also serve as a vessel for high shear or other mixing, although the mixing may take place downstream of a clean gasoline storage tank.

[0006] The clean fuel is then thoroughly mixed with water and fed to an atomizing nozzle where the fuel/water mixture is further mixed with air, heated, vaporized and fed to an autothermal reformer. If a hydrodesulfurizer is utilized, the hydrogen for it may be provided downstream of the reformer, such as after the reformate is passed through one or several water gas shift reactors and a preferential CO oxidizer (PROX). The feedback hydrogen will typically be the same as that fed to the fuel cell power plant when the arrangement herein is used to provide hydrogen to a fuel cell power plant.

[0007] One advantage of pre-emulsifying the liquid water and the liquid gasoline is that measurements of liquid flow are much more easily made than are measurements of the flow of steam or vapor. [0008] Other variations will become apparent in the light of the following detailed description of exemplary embodiments, as illustrated in the accompanying drawings.

Brief Description of the Drawings

[0009] Fig. 1 is a simplified, stylized schematic diagram of a system employing pre-emulsification of water and gasoline and vaporization thereof with air.

[0010] Fig. 2 is a partial, simplified, stylized schematic diagram of a system illustrating alternatives in the system of Fig. 1.

[0011] Figs. 3 and 4 are fragmentary views of alternative reformers.

Mode(s) of Implementation

[0012] In Fig. 1 , a tank 13 for storing water is connected by a conduit 14 to a valve 15, which is connected by a conduit 16 to a gasoline tank 17. The tank 17 has an inlet 21 for feeding raw gasoline into a chamber 22 within the tank 17. The chamber 22 is connected through a conduit 24, a valve 25 and a conduit 26 to a pump 27 which forces raw gasoline through a conduit 28 to the inlet 29 of a hydrodesulfurizer 30. The desulfurized gasoline is passed through a conduit 32, a valve 33 and a conduit 34 to a chamber 38 within the tank 17 which comprises a clean fuel (desulfurized fuel) storage tank 39. The pressure and flow in conduit 34 are controlled by balancing the valves 25, 33; alternatively, the pump 27 may be a variable flow pump.

[0013] A high shear mixer 41 may be disposed within the chamber 38. A conduit 44 provides a pre-emulsion mixture of water and clean fuel to a pump 45 which forces fuel through a conduit 46, a valve 47 and a conduit 48 to the inlet 49 of the inner portion 50 of a coaxial atomizing nozzle 53 which forms part of a vaporizer 54. The outer portion 55 of the nozzle 53 receives at its inlet 56 compressed air, such as turbocharger air, through conduits 59, 60 and a valve 61.

[0014] The vaporizer 54 may include a glow plug 64 in a startup combustor 65, which raises the temperature of the fuel/water/air mixture to on the order of 37O ⁰ C (700 ⁰ F) so that it vaporizes. Vaporization and mixing can be enhanced by means of an inert bed 66 of high temperature, structural labyrinth, such as inert ceramic foam, as part of the vaporizer 54. The precombustor 65 in the general case will provide enough heat, at

startup, for partial combustion of the products therein, thereby heating the inert bed so that the mixture passing through the inert bed will become totally vaporized.

[0015] Because there are always some lighter, four-carbon and five- carbon components in the gasoline (such as butane and pentane), when the gasoline/water pre-emulsion passes through the inner part 50 of the nozzle 53, these will vaporize and will more easily ignite. This causes a large expansion of volume as vaporization occurs, which drives the pre- emulsion mixture through the nozzle at high speed, helping to disperse and atomize both the water and the heavy components of gasoline. The vapor is then fed to the catalyst 69 of the autothermal reformer 70 for conversion into reformate, which, when reforming gasoline, will typically comprise (on a dry basis) about 33% hydrogen, 18% CO, 6% CO2, small amounts of unconverted hydrocarbon fuel and other, inert gases. [0016] The untreated reformate from the reformer 70 is fed through a conduit 74 to a water gas shift reactor 75, the output of which is carried in a conduit 76 to a PROX 77. The output from the PROX 77 in a conduit 78 is provided to the fuel cell power plant as its primary fuel. The output of the PROX 77 in a conduit 79 is carried through a valve 80 and a conduit 81 to the inlet 29 of the hydrodesulfurizer 30.

[0017] To control the steam/carbon ratio, a pair of flow meters 84, 85 inform a controller 86 of the precise amount of water and clean fuel being provided to the chamber 38 in the clean fuel tank 39. The valve 15 is slaved to the valve 33 to maintain the proper ratio. The controller meters the water and the clean fuel through corresponding valves 15, 33 so as to maintain the desired total flow, as well as the ratio of flows for a proper steam/carbon ratio.

[0018] The demand of the fuel cell power plant is indicated to the controller by a signal 87 which is used by the controller to adjust the valves 47 and 61, thereby controlling the amount and ratio of mix that is provided to the atomizing nozzle 53. When the load (the electrical demand) on the fuel cell is increased, more hydrogen is consumed, and that fact is passed along to the controller 86 by the signal 87. Similarly, a lower demand requires less hydrogen and that fact is communicated to the controller 86

by the signal 87. Whenever the flow through the valve 47 is altered, the amount of compressed air is adjusted by the valve 61 as well. [0019] The rate of providing clean, desulfurized gasoline through the hydrodesulfurizer 30 is not tied directly to the rate at which the fuel/air pre- emulsion is passed through the valve 47. In the embodiment of Fig. 1 , the pump 27 will be operated and the valves 33 and 15 adjusted whenever the fuel/water pre-emulsion mixture in the chamber 38 falls below a predetermined level. If a higher predetermined level is reached indicating that the chamber 38 is full, the pump 27 will be shut down, and valves 15 and 33 closed, by the controller 86.

[0020] Use of recycle hydrogen in the conduits 79, 81 for the hydrodesulfurizer 30 slows down the process of providing clean fuel for mixture with water. If a more rapid startup is desired, a small catalytic partial oxidizer (mini CPO) may be used in addition to the ATR 70 for the sole purpose of providing a small amount of hydrogen to the hydrodesulfurizer, as disclosed in U.S. patent 7,128,768, although an Ni desulfurizer (Fig. 2) will begin desulfurization without waiting for reformate to be generated.

[0021] An embodiment shown in Fig. 2 illustrates several options which may be selected, in any implementation of the pre-emulsioπ/vaporization system. The clean fuel tank 38a need not be formed within the raw fuel tank 17a. The desulfurizer 30a may have a nickel catalyst, thereby eliminating the need for a hydrogen feed (conduits 79, 81 , Fig. 1 ). The clean fuel leaving the desulfurizer 30a will pass through a conduit 32a to the clean tank 38a and thence through a conduit 32b, the valve 33 and conduit 34 to a mechanical agitation mixer 41a. If desired in any given utilization of the pre-emulsion/vaporization system, clean gasoline may be stored in a clean tank 38a, as briefly illustrated in Fig. 2, and a mixer 41a, which may be a mechanical agitation mixer, used apart from the clean fuel storage tank 38a, as briefly illustrated in Fig. 2. The water from tank 13 is fed into the mixer through conduits and valves 14-16 as in Fig. 1. The pre- emulsion leaves the mixer 41a, passes through the conduit 44, to pump 45, through conduit 46 and valve 47 to a fuel inlet 49a of a commercially obtainable gas-assist, atomizing nozzle 53a which may, for instance,

comprise an air-assist nozzle produced by Orbital, similar to those used for atomizing fuel oil in residential furnaces. Compressed air is connected to a gas-assist inlet 56a of the nozzle 53a.

[0022] In the embodiments of Figs. 1 and 2, any conventional mixers selected for suitable pre-emulsion activity may be utilized as desired. The vaporized pre-emulsion described herein may be used as feed for a catalytic partial oxidizer 70b (Fig. 3), or a homogenous, non-catalytic partial oxidizer 70c (Fig. 4), as well as other similar reformers. Means other than the glow plug 64 may be used to initiate heating, vaporizing and possibly partial combustion in advance of the inert bed 66. In any given implementation, other methodology for assuring adequate vaporization of the three way mixture may be utilized in place of the startup combustor 65 with the glow plug 64 and the inert bed 66.