Method for producing biomethane incorporating the production of heat for the methaniser using membrane separation

Patent metadata

Field	Value
Publication number	US-2016289580-A1
Application number	US-201415037198-A
Country	US
Kind code	A1
Filing date	Nov 6, 2014
Priority date	Nov 18, 2013
Publication date	Oct 6, 2016
Grant date	—

Abstract

The present invention relates to a process for producing biomethane suitable for supplying a natural gas network that incorporates a process for providing heat for heating the biogas production step, the process comprising at least steps of producing biogas by anaerobic fermentation of organic matter, of pretreating and compressing the biogas and also of permeation in order to obtain, after a first separation by permeation, a stream of biomethane and a gaseous permeate having a reduced methane content; the process additionally provides the heat necessary for the anaerobic fermentation step via a boiler using the retentate from a second permeation step fed by the permeate from the first separation.

First claim

1 - 6 . (canceled)

7 . A process for producing biomethane suitable for supplying a natural gas network that incorporates a process for providing heat for heating the biogas production step, wherein the biomethane production process comprises at least:
a step (a) of producing biogas by methanization of organic matter; a step (b) of pretreating the biogas produced during step (a); a step (c) of compressing the pretreated biogas with a compressor; a step (d) of separating by permeation the pretreated and compressed biogas resulting from step (c) in order to produce a gaseous retentate having a methane content of greater than 89% and a gaseous permeate having a methane content of between 10% and 25%; a step (e) of providing the gaseous retentate from step (d) as biomethane, a step (g) of heating said heating water in a gas boiler having burners, heat being provided to step (a) via a heating water circuit including the gas boiler; a step (h) of separating by permeation the gaseous permeate resulting from the first permeation separation step (d) in order to produce a methane-enriched gaseous retentate and a methane-depleted permeate, the methane content of the gaseous retentate of step (h) being greater than or equal to 25; a step (i) of supplying the burners of the boiler from step (g) with the retentate from the separation step (h); and a step (j) of discharging the permeate produced by the permeation separation step (h).

8 . The process of claim 7 , further comprising a step (k) of providing additional heat to the water circulating in said heating water circuit using heat recovered during steps (b) and (c).

9 . The process of claim 7 , wherein a variable fraction of the methane-enriched retentate from the separation step (h) is sent back to an inlet of the compressor of step (c) when the supply of heat to step (a) is greater than heat requirements of step (a).

10 . A plant for carrying out the process of claim 7 for producing biomethane intended for supplying a natural gas network and the integrated provision of heat for heating the biogas production step, said plant comprising at least:
a biomethane production unit comprising at least a source of organic matter, a digester for producing biogas by methanization of said organic matter, and a module for prepurifying the biogas produced;
a compressor suitable for compressing the prepurified biogas;
a first module for separating, by membrane permeation, the prepurified and compressed biogas, said first module being suitable for producing a gaseous retentate having a methane content of greater than 89%, preferably greater than 96.5% and a gaseous permeate having a methane content of between 10% and 25%, preferably of the order of 20%;
a system for heating the organic matter contained in the digester comprising at a heating water circuit suitable for heating the digester and a gas boiler being suitable for heating the water of the heating water circuit; and
a second module for separating, by membrane permeation, the gaseous permeate resulting from the first permeation separation module, said second module being suitable for producing a methane-depleted permeate and a methane-enriched gaseous retentate having methane content greater than 25, wherein the second module provides the gaseous retentate retentate thereof as biogas, the second separation module supplies the retentate thereof to the burners of said gas boiler, and the second separation module discharges the permeate resulting therefrom.

11 . The plant of claim 10 , wherein the means suitable for cooperating in order to heat the organic matter contained in the digester comprise additional means suitable for recovering heat from the biogas prepurification module and the prepurified biogas compressor and also additional means suitable for providing the heat recovered to the water of the heating circuit of the digester.

12 . The plant of claim 10 , further comprising a line equipped with a flow control valve suitable for recycling a fraction of the retentate from the second membrane stage to the inlet of the compressor.

13 . The process of claim 7 , wherein the gaseous retentate resulting from performance of step (d) has a methane content of greater than 96.5%.

14 . The process of claim 7 , wherein the gaseous retentate resulting from performance of step (h) has a methane content of between 30% and 40%.

15 . The plant of claim 10 , wherein said first module is suitable for producing a gaseous retentate having a methane content of greater than 96.5%.

16 . The plant of claim 10 , wherein a second module is suitable for producing the methane-enriched gaseous retentate at a methane content of between 30% and 40%,

Assignees

• Air Liquide
• L'Air Liquide Soc Anonyme Pour I'Etude Et I'Exploitation Des Procedes Georges Claude

Inventors

• Paget Nicolas
• Garnaud Delphine
• PRINCE Guéaël
• Lefebvre Mathieu

Classifications

• Y02E50/30

  Fuel from waste, e.g. synthetic alcohol or diesel · CPC title

• C10L2290/06

  Heat exchange, direct or indirect · CPC title

• C10L3/104 Primary

  Carbon dioxide · CPC title

• C10L2290/548

  Membrane- or permeation-treatment for separating fractions, components or impurities during preparation or upgrading of a fuel · CPC title

• C10L2290/26

  Composting, fermenting or anaerobic digestion fuel components or materials from which fuels are prepared · CPC title