RO128289A2 - Hydrogen processor for fuel cell supply - Google Patents

Abstract

The invention relates to a process for preparing highly pure hydrogen employed in the supply of fuel cells and to a device for carrying out said process. According to the invention, the process consists in steam reforming the methane or natural gases, followed by the steam conversion of CO into COand hydrogen purification with selective membranes of palladium alloy until reaching a CO content of 1 ppm, at the most. The device claimed by the invention consists of a unit for catalytic reforming of methane using steam, said unit comprising a reactor and a hydrogen advanced purification unit.

Description

HYDROGEN PROCESSOR FOR FUEL POWER SUPPLY

Description:

BACKGROUND OF THE INVENTION The present invention relates to a process for obtaining the ultrapure hydrogen needed to fuel fuel cells, by autothermal reforming of a gas mixture, consisting of methane, steam and, as the case of oxidant, which is further purified by the use of selective alloy based membranes. palladium-silver for ultrapure hydrogen permeation.

The phases of the process technology regarding the primary and secondary catalytic reforming are known to obtain a mixture of reformed gas which mainly comprises H2, CO2, CO.

A hydrogen processor is disclosed, disclosed in US Pat. No. 6254839, which discloses an apparatus for converting a combustible gas into hydrogen gas and carbon dioxide.

Generally, patents describing different reformer designs comprise a tube including a catalyst, a second tube arranged circularly in connection with the first, a fractionation fuel configured to convert an amount of hydrocarbon feedstock into a first gas mixture. and a second gas mixture which is of average molecular weight greater than the first, a steam supply line communicating with the first tube and an oxygen content fed with the gas mixture resulting from the first tube into the second tube.

In the case of US 6254389 hydrogen production was only 40% relative to the molar mass. It is an object of the present invention to increase this percentage further. On the other hand, the otherwise problematic technical objective that must be solved lies in the fact that the resulting purified gas, namely hydrogen (energy vector), can be fully utilized and not allow emissions of fluid substances into the environment.

The problem solved by the present invention is to make a compact processor easy to implement, reliable to ensure a conversion of methane into pure hydrogen as completely solved by a process that, in a first phase, a synthesis gas is produced in - a reforming unit where the endothermic reaction is carried out at high temperatures for example 850 ° C when using, for example, aluminum-based catalyst. The methane vapor mixture is made by diffusive pumping, resulting in a reformate containing mainly hydrogen and carbon monoxide.

Further the gas flow enters an exothermic catalytic zone which together with an oxidant and water vapor forms a mixed gas which is further directed into an advanced purification zone. As an oxidant, preheated air is used at a temperature of approximately 450 ° C, when using an iron-based catalyst. Thus, the technological process is of autothermal reforming type that takes place under the conditions of a precise dosage of the air and steam supply. Thus, the catalysts used must be well determined, as they must meet both the requirements of the reaction between carbon oxide and water from the catalytic reforming with vapors and the partial oxidation process. This process is carried out with another mixing chamber by diffusive pumping, finally resulting in the conversion of carbon monoxide into carbon dioxide by a suitable catalyst.

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9-08-2011

The new hydrogen processor suitable for a fuel cell assembly combines in one device a hydrogen production unit by the catalytic reforming of the methane vapor integrated with a hydrogen purification unit up to a level of CO impurities <1 ppm, more more than enough to power a PEM proton changer membrane fuel cell.

Compact steam reforming according to the present invention is carried out in a reactor which is heated by means of a burner. The reactor has a preheating device, with a high rate of heat recovery attributed to the burner. This increases the efficiency of the reform process. Temperature control is possible by controlling the operating pressure at the evaporator, respectively the methane steam mixture from the mixing chamber by diffusive pumping but also by regulating the combustion in the combustion chamber.

After obtaining a sufficient concentration of impurities in the synthesis gas processing, an advanced purification of hydrogen is performed using palladium based membranes, a technology proven to be the most effective in the field.

The palladium membrane is usually a metal tube comprising a palladium-silver alloy layer deposited on a porous ceramic support (having micro or nano-pores), which has the unique property of allowing only monoatomic hydrogen to pass through its crystalline network. , when heated above 300 ° C. The hydrogen gas molecule, which comes in contact with the surface of the palladium membrane, dissociates into monoatomic hydrogen and passes through the membrane. On the other surface of the membrane, monoatomic hydrogen is recombined into molecular hydrogen.

The following is a detailed description of a preferred embodiment of the invention.

The hydrogen processor according to the invention is composed of several insulating layer mantle modules for maintaining a constant temperature gradient on each module as in Figure 1. Starting from the processor base module 41 is intended for steam methane reforming using if for the required endothermic conversion reaction the heat from a flame burner characterized by the existence of a refractory stainless steel combustion chamber lined with nickel 33, methane is introduced through the processing pipe 1, and the air required to burn through the pipe 48. Due to the production of a spark at electrode 47, the methane air mixture ignites, generating the required thermal energy further in the process.

The methane vapor mixture for reforming is made in the ejector 7, after which it is converted to the catalyst 37 through synthesis gas. The synthesis gas is driven by pressure through the flow area 30 further through another ejector 8 which together with the oxygen or oxygen enriched air is mixed and pumped through a new catalyst 13. The synthesis gas thus oxidized and passed through a suitable catalyst at 400 ^u C temperature it enters an advanced purification zone with palladium membranes 17 (the present example is with three palladium membranes type tubes), where purified hydrogen is collected through the pipe 16.

Part of the unpermeate gas stream enriched in carbon dioxide is extracted by 11 and through a special condenser the outer shell of the hydrogen processor is cooled, and with the accumulated hydrogen and appropriately dosed, the combustion zone 33 is fed through the pipe 2, reducing methane content for combustion. At the same time, through the access pipe in the combustion zone 3, the combustion of hydrogen surplus from the type fuel cell with proton exchanger membrane (PEMFC) for which the present invention represents is in fact a hydrogen generator.

The heat exchangers for working fluid processing 34, 29 are of a spiral tubular type and are located on the path of the flue gases.

Authorized representative

Dr. ing. AnghelVasi Prof. univ. Dr. Ștefanescu Ioa:

Dr. Phys. V ari am Mih Dr. ing. Culcer Mih

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which is why Route 39 will be lined with a nickel coating. The heat exchangers according to the flow zone 24, 5, respectively the exchanger 20, which processes preheated water, each one of them is a thermal energy saver from the flue gases and allows the temperatures determined by the temperature sensors 6, 9 and 15 respectively, according to the process technology, in the area of the ejectors disposed offset on the vertical axis 32.

An adequate acquisition system allows the control of the flow rates, the pressures p 1 _t p ₂ , p ₃ , p ₄ , respectively the temperatures t-ι, t ₂ , t ₃ , t ₄ , according to the dynamic regimes determined first and foremost by the choice of the catalysts and the palladium membrane. , suitable for the prior configuration of the PEM fuel cell.

For example, the processor according to the present invention dimensioned at a hydrogen flow rate of 1Nm ³ / h will achieve a methane conversion of 78% to 91%. The purification units respectively with platinum catalyst, ruthenium catalyst reduce below 10 ppm CO by preferential oxidation and palladium membrane further reduces even below 1% CO, maintaining a hydrogen purity of 99.99% or more. By using a dense palladium alloy membrane, high purity hydrogen of at least 99.999999% can be produced.

Particularly important for the hydrogen processor is the solution adopted for sealing, especially for the permeation zone, of the advanced purification system, given the strong diffusive character of hydrogen through materials, in Figure 2 a solution of sealing of the hydrogen is presented. membrane system ensuring flow distribution on a single outlet at the top, respectively inlet for a carrier fluid such as nitrogen at the bottom. Thus, the sealing elements 56 and 54 are distinguished, which are pressed through the tubular part 57, which in turn is pressed by the reference 58 which makes common body with the flange 52 through welding. Also for the distribution area are provided the sealing elements 60, 61 pressed through the end flange 62.

The process according to the invention has the following advantages:

The process of obtaining the reformed gas in the hydrogen processor is autothermal, thus being able to achieve significant energy savings and reduce the manufacturing costs.

The hydrogen processor according to the invention has the advantage that it is compact, easy to make and maintain but also the quality of achieving a stable flow of purified hydrogen by means of which it can be facilitated to adjust the technological parameters according to the consumption in real time.

By using special ejectors, with diffuser mixing chamber, the mixed fuels can be further processed at high pressure and low speed thus facilitating the conversion needed from the reforming unit and reducing carbon monoxide.

The present invention can be used for hydrogen fuel cell fuel but reconfigured on a case-by-case basis and can be adapted for testing different catalysts to obtain hydrogen at increasingly lower costs.

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HYDROGEN PROCESSOR FOR FUEL POWER SUPPLY

Claims (4)

claims: 1. Process and apparatus for the production of ultrapure hydrogen, by steam reforming of methane or natural gas, followed by steam conversion of CO to CO ₂ and purification of hydrogen with selective palladium alloy membranes for fuel cells, characterized by that in order to reduce the energy consumption of the processor, the residual or surplus hydrogen flow from the fuel cell anode is reintroduced and on the other hand the exothermic reaction energy from the oxidation mode is further used for the hydrogen permeation module. Method and apparatus according to claim 1, characterized in that two systems can be integrated to make diffusive mixtures that facilitate the dosing of a homogeneous gas mixture in predetermined stoichiometric proportions with the achievement of pressures between 20 and 30 bar by using ejectors or compressors. by jet, the energy transfer from the motor fluid to the ejected one can be predetermined from the calculation and / or experiment. 3. Process and apparatus according to claim 1, characterized in that part of the nonpermeable gas stream enriched in carbon dioxide is extracted by 11 and through a special condenser the outer casing of the hydrogen processor is cooled and the hydrogen accumulated and dosed. correspondingly, the combustion zone 33 is fed through pipe 2, reducing the methane content for combustion. 4. Process and apparatus according to claim 1, characterized in that the sealing system is optimized according to the displacements due to the respective expansions or the leaks of gas or to provide the premises for the processing of the fluids at stable temperatures under the conditions of maintaining a competitive fuel consumption.