Process for starting mode or stand-by mode operation of a power-to-gas unit comprising a plurality of high-temperature electrolysis (soec) or co-electrolysis reactors

Patent metadata

Field	Value
Publication number	US-2019194816-A1
Application number	US-201816227252-A
Country	US
Kind code	A1
Filing date	Dec 20, 2018
Priority date	Dec 22, 2017
Publication date	Jun 27, 2019
Grant date	—

Abstract

The application relates to a process for operating in starting mode or in stand-by mode a unit, termed power-to-gas unit, comprising a number N of reactors (1) with a stack of elemental electrolysis cells of solid oxide type (SOEC), the cathodes of which are made of methanation reaction catalyst material(s).

First claim

1 . A process for operating in starting mode or in stand-by mode a unit, termed power-to-gas unit, comprising a number N of reactors with a stack of solid oxide (SOEC) type elemental electrolysis cells, the cathodes of which are made of methanation reaction catalyst material(s),
wherein, when it is desired to carry out an increase in temperature of the N reactors or of a fraction thereof, or when the level of available electricity is insufficient to carry out a high-temperature electrolysis (HTE) or a co-electrolysis of H 2 O and CO 2 within all of the N reactors, the process comprises the following steps: a/ a number P of reactors are supplied with electricity and, if required, with heat, and either steam H 2 O, or a mixture of steam and carbon dioxide CO 2 is supplied and distributed to the cathodes of the P reactors so as to carry out, at each cathode of the P reactors, either a high-temperature electrolysis (HTE) of the steam H 2 O, or a high-temperature co-electrolysis of steam and carbon dioxide, b/ at least one part of the gases resulting from the electrolysis (hydrogen H 2 , steam H 2 O ) or from the co-electrolysis (H 2 , steam, carbon monoxide CO, carbon dioxide CO 2 , methane CH 4 ) is recovered and is supplied and distributed to each cathode of a number X of reactors not supplied with electricity, the number X being less than or equal to N−P, so as to carry out, at each cathode of the X reactors, a methanation by heterogeneous catalysis.

2 . The operating process according to claim 1 , wherein the carbon dioxide is emitted by a production source, from a production site, in particular chosen from energy production sites (nuclear power stations for the waste heat, biomass methanization or gasification power stations for CO 2 -emission and/or waste heat), industrial production sites (cement works, steel industries for CO 2 emission and/or waste heat), service industry buildings such as hospitals, closed-site transportation networks, or else elimination sites, such as waste heat treatment units, etc.

3 . The operating process according to claim 1 , wherein, in starting mode or in stand-by mode, the heat requirements of the unit, including the reactors (SOEC), are supplied by the waste heat of a production source, of a production site.

4 . The operating process according to claim 3 , wherein the production site is chosen from energy production sites (nuclear power stations for the waste heat, biomass methanization or gasification power stations for CO 2 -emission and/or waste heat), industrial production sites (cement works, steel industries for CO 2 emission and/or waste heat), service industry buildings such as hospitals, closed-site transportation networks, or else elimination sites.

5 . The operating process according to claim 1 , comprising a step c/ wherein the gases produced by methanation in the SOEC reactors produced by step b/ are introduced into the N dedicated methanation reactors of the power-to-gas unit.

6 . The operating process according to claim 1 , wherein step a/ is carried out at temperatures of between 600° C. and 1000° C.

7 . The operating process according to claim 1 , wherein step b/ is carried out at temperatures of between 400° C. and 800° C., and inferior to at least 100° C. to the temperature of step a/.

8 . The operating process according to claim 1 , wherein steps a/ and b/ are carried out at pressures of between 0 and 100 bar, preferably of between 4 and 80 bar.

9 . The operating process according to claim 1 , the N reactors all being reactors with a stack of elemental electrolysis cells of SOEC type, each formed from a cathode, an anode and an electrolyte inserted between the cathode and the anode, and a plurality of electrical and fluid interconnectors, each arranged between two adjacent elemental cells with one of its faces in electrical contact with the anode of one of the two elemental cells and the other of its faces in electrical contact with the cathode of the other of the two elemental cells.

10 . The operating process according to claim 9 , wherein step a/ is carried out by supplying and distributing to each cathode of the P reactors either steam H 2 O, or a mixture of steam and carbon dioxide CO 2 , or by supplying and distributing steam to each cathode of one of the two adjacent elemental cells of the P reactors and carbon dioxide is fed and distributed to the cathode of the other of the two elemental cells of the P reactors, so as to carry out, at each cathode of the P reactors, either a high-temperature electrolysis of the steam H 2 O, or a high-temperature co-electrolysis of steam and of carbon dioxide.

11 . The process for producing methane CH4 from an “intermittent” energy source, implementing the process for operating in stand-by mode a power-to-gas unit according to claim 1 , wherein step b/ is carried out when said intermittent source is no longer capable of producing the level of electricity sufficient for all the N reactors.

Assignees

• Commissariat Energie Atomique

Inventors

• Brunot Aymeric
• Lacroix Vincent

Classifications

• C25B11/0426

  Chemistry & Metallurgy · mapped topic

• C25B11/035

  Chemistry & Metallurgy · mapped topic

• C25B15/08 Primary

  Supplying or removing reactants or electrolytes; Regeneration of electrolytes · CPC title

• C25B9/20

  Chemistry & Metallurgy · mapped topic

• C25B15/02

  Process control or regulation · CPC title