FIELD OF THE INVENTION

The present invention relates to fuel cells and, more particularly, high-temperature solid oxide fuel cells to generate electricity and ammonia as a byproduct available for further use.

BACKGROUND OF THE INVENTION

Fuel cells are electrochemical devices that convert the chemical energy of fuel and an oxidizing agent into electricity. Hydrogen or substances that include hydrogen are used as fuel in fuel cells. The fuel cells where ammonia is directly fed to an anode of the fuel cell are known in the art (see, for example, US7157166). An alternative technical solution concerns the fuel cells fueled by hydrogen generated in the decomposition of ammonia fuel into hydrogen and nitrogen (US3532547).

WO/2020/141500 discloses a high-temperature solid oxide fuel cell arrangement fueled by a hydrogen or hydrocarbon fuel and generating electricity and ammonia as a byproduct. The arrangement comprises (a) a cathode area fed with air; (b) an anode area fed with the fuel; and (c) an oxide ion-conducting electrolyte disposed between the cathode and anode areas. The cathode has an ammonia-rich tail-gas stream. The fuel cell further comprises a gas separator configured for separating ammonia generated on the cathode from tail-gas stream and means for utilizing separated ammonia selected from the group consisting of an ammonia reformer configured for generating hydrogen to be admixed to the fuel fed to the anode, a collecting tank for storing the ammonia and an auxiliary solid oxide fuel cell fueled by the separated ammonia and any combination thereof.

The high-temperature solid oxide fuel cells fed with hydrogen or hydrocarbon fuels enabling utilization of ammonia generated as a byproduct at the cathode area are known in the art. Thus, there is a long-felt need for providing fuel cells generating ammonia in a more effective manner at the anode with a higher ammonia output. SUMMARY OF THE INVENTION

An aspect of the present invention relates to a high-temperature solid oxide fuel cell arrangement fueled by a hydrogen or hydrocarbon fuel and generating electricity and ammonia as a byproduct. The aforesaid fuel cell comprises: (a) a cathode area fed with dry air; (b) an anode area fed with said fuel; and (c) an oxide ion-conducting electrolyte area disposed between said cathode and anode areas.

It is a core purpose of the invention is to provide the anode area comprising transition metals selected from the group consisting of Lanthanum, Cerium, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Rhodium, Palladium, Argentum and any combination thereof; n. The anode area when fed with a hydrogen (H2) and nitrogen (N2) mixture generates exhausted gases comprising gaseous ammonia.

A further object of the invention is to disclose the anode area comprising a cermet Ni-ScSZ layer and a catalytic layer.

A further object of the invention is to disclose the catalytic layer comprising a compound of transition metals and nitrogen {TM^oTM^ TM^ N _y where i and xi are positive integers; said transition metals are selected from the group consisting of Lanthanum, Cerium, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Rhodium, Palladium, Argentum and any combination thereof.

A further object of the invention is to disclose the fuel cell arrangement comprising a gas separator.

A further object of the invention is to disclose the gas separator comprising a compressor configured for pressurizing said exhausted gases.

A further object of the invention is to disclose the compressor said compressor configured for pumping said exhausted gases via a membrane arrangement such that ammonia is separated from said exhausted gases.

A further object of the invention is to disclose the compressor configured for liquefying said gaseous ammonia while other constituents of the exhausted gases are vented to the atmosphere. A further object of the invention is to disclose the gas separator comprising an ammonia absorber and an ammonia evaporator heated by heat generated by said fuel cell.

A further object of the invention is to disclose a method of generating ammonia as a byproduct by a high-temperature solid oxide fuel cell arrangement fueled by a hydrogen or hydrocarbon fuel; said method comprising steps of: (a) providing a high-temperature solid oxide fuel cell arrangement fueled by a hydrogen or hydrocarbon fuel; said fuel cell comprising: (i) a cathode area fed with a air; (ii) an anode area said comprising transition metals selected from the group consisting of Lanthanum, Cerium, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Rhodium, Palladium, Argentum and any combination thereof and (iii) an oxide ion-conducting electrolyte disposed between said cathode and anode areas; said anode comprises a cermet Ni- ScSZ layer and a M N catalytic layer; said anode area being fed with an hydrogen-nitrogen mixture generates exhausted gases comprising gaseous ammonia; (b) feeding said fuel-nitrogen mixture to said anode area; (c) feeding air to said cathode area; (d) operating said fuel cell; (e) generating said ammonia as a byproduct in said anode area; and (f) separating said ammonia from said exhausted stream.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be implemented in practice, a plurality of embodiments is adapted to now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic diagram of a high-temperature solid oxide fuel cell arrangement;

Fig. 2 is a schematic diagram of a high-temperature solid oxide fuel cell arrangement provided with an ammonia reformer;

Fig. 3 is a detailed schematic diagram of a dephlegmator-based separator;

Fig. 4 is a detailed schematic diagram of a membrane -based separator; and

Fig. 5 is a detailed schematic diagram of an expansion-based separator. DETAILED DESCRIPTION OF THE INVENTION

The following description is provided, so as to enable any person skilled in the art to make use of said invention and sets forth the best modes contemplated by the inventor of carrying out this invention. Various modifications, however, are adapted to remain apparent to those skilled in the art since the generic principles of the present invention have been defined specifically to provide high-temperature solid oxide fuel cell arrangement fueled by a hydrogen or hydrocarbon fuel and generating electricity and ammonia as a byproduct.

Reference is now made to Figs 1 and 2 presenting alternative embodiments of high-temperature solid oxide fuel cell arrangement 100a to 100b fueled by a hydrogen or hydrocarbon fuel to anode fuel cell and dry air to the cathode and generating ammonia as a byproduct on the anode of the fuel cell.

Referring to Figs 1 and 2, hydrogen or any hydrocarbon fuel is fed to anode area 113 of fuel cell 110 via passage 121. Concurrently, air is fed to cathode area 117 via passage 123. Numeral 115 refers to an oxide ion conducting electrolyte. Arrangements 100a and 100b include gas separator 130, which separates gaseous ammonia exhausted gases fed to separator 130 via passage 131. Numeral 140 marks electric energy provided by fuel cell 110 to a load (not shown). Anode area 113 is fluidly connected to separator 130 by passage 131. Anode area 113 is made of a cermet comprising transition metals such as Lanthanum, Cerium, Scandium, Titanium, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Rhodium, Palladium and Argentum. According to one embodiment of the present invention, anode area 113 is provided with a catalyst layer (not shown) made of made of a compound of transition metals and nitrogen {TM^oTM^ TM^ N _y where i and xi are positive integers Exhausting gases from cathode area 117 are vented to atmosphere. Feeding dry air to cathode area 117, generating gaseous ammonia therewithin and feeding the exhausting gases containing ammonia to separator 130 is also in the scope of the present invention. Electric energy generated by fuel cell 110 is designated by numeral 127. The heat generated in fuel cell 110 is transferred to separator 130 via passage 131.

Referring to Fig. 1 showing arrangement 100a, ammonia separated from exhausted gases is fed to ammonia tank 140 via passage 135. In Arrangement 100b (Fig. 2), separated ammonia is fed to reformer 150 via passage 151. After reforming, obtained hydrogen and nitrogen are admixed via passages 153 and 155 to hydrogen or any hydrocarbon fuel fed to anode area 113 via passage 121.

Reference is now made Figs 3, 4 and 5 presenting alternative embodiments 200a, 200b and 200c of ammonia separators, respectively. Embodiment 150a in Fig. 3 includes ammonia absorber 270, ammonia evaporator 280 and dephlegmator 290. The exhausted gases are fed into ammonia absorber 270 via passage 131 based on absorbing ammonia from the exhausting gases in water. An ammonia solution obtained in absorber 270 then is fed into ammonia evaporator 280 via passage 275. Within evaporator 280, the aqueous ammonia solution is vaporized by the heat generated by fuel cell 110 (not shown) via heat transfer means 129. The vapor generated within ammonia evaporator 280 via passage 285 is provided to dephlegmator 290 where ammonia and water vapor fractions are separated. Separated ammonia outputs via passage 295.

Referring to Fig. 4 showing embodiment 200b, the exhausted gases via passage 131 are collected in tank 210 configured for storing exhausted tail gases. The exhausted gases stored in tank 210 are then pumped by compressor 220 via passages 215 and 225 and fed to membrane arrangement 260 configured for separating ammonia from the aforesaid exhausted gases. Separated ammonia (permeant gas) outputs from passage 265. Passage 265 is designed for venting retentate gases.

In Fig. 5, embodiment 200c is presented. The gases exhausted from the anode area (not shown) are fed to tank 210 via passage 131. Tank 230 is configured for accumulating the aforesaid exhausted gases. Then, the exhausted gases via passage 215 reach compressor 220 is used for pressurizing the exhausted gases. The pressurization of the exhausted gasses results in liquefying ammonia which is accumulated via passage 225 in tank 230 while other constituents of the pressurized gases are vented to the atmosphere via passage 235. Ammonia is cooled when it passes via expansion valve 240. Thereat, low-temperature gaseous ammonia can be used for cooling a working body circulating in loop 255 in heat-exchange arrangement 253. Finally, gaseous ammonia is provided via pipe 155 to a consumer.

Example 1::

Cathode: Eanthanum-Strontium Manganate/Cerium oxide doped with Gadolinium.

Electrolyte: Zirconium oxide stabilized by Scandium

Anode: Nickel oxide-Zirconium oxide stabilized by Scandium. The fuel cell was fed with hydrogen and nitrogen (1:1 ratio) with flow rate of 0.4 1/min at the anode and air at the cathode with flow rate of 1 1/min. Operation temperature was about 800°C.

The results of characterization are in Table 1.

Example 2:

Cathode: Lanthanum-Strontium Manganate/Cerium oxide doped with Gadolinium.

Electrolyte: Zirconium oxide stabilized by Scandium and Cerium

Anode: Nickel-Zirconium oxide stabilized by Scandium provided with a layer of catalyst MmN. The catalyst layer is coated onto the anode by means of serigraphic deposition

The fuel cell was fed with hydrogen and nitrogen (1: 1 ratio) with flow rate 0.4 l/min at the anode and air at the cathode with flow rate of 1 1/min. Operation temperature was about 800°C. The results of characterization are in Table 1.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.