DIGESTER COMPRISING AN OXYGEN INJECTION SYSTEM HAVING A TUBULAR MEANS FORMED IN A GRID PATTERN

Abstract

A plant for producing at least partially desulfurized biogas, comprising a biomass digester and/or post-digester, the digester and/or post-digester comprising: a chamber comprising the biomass and the gas space, and a system for injecting an oxidizing gas into the gas space, wherein the injection system comprises a tubular means formed in a grid pattern, having a centre of symmetry placed in the axis of symmetry of the chamber, and having micro-injectors.

Claims

1. A plant for producing at least partially desulfurized biogas, comprising a biomass digester and/or post-digester, the digester and/or post-digester comprising: a chamber comprising the biomass and the gas space, and a system for injecting an oxidizing gas into the gas space, wherein the injection system comprises a tubular means formed in a grid pattern, having a centre of symmetry placed in the axis of symmetry of the chamber, and having micro-injectors.

2. The plant according to claim 1, wherein each square of the grid pattern comprises a micro-injector on one of its sides.

3. The plant according to claim 1, wherein each square of the grid pattern comprises a micro-injector on each of its sides.

4. The plant according to claim 1, wherein the grid pattern comprises at least four squares.

5. The plant according to claim 1, wherein at least one micro-injector is located less than two metres from the axis of symmetry of the chamber.

6. The plant according to claim 1, wherein the tubular means is located less than one metre from the gas space-biomass interface.

7. The plant according to claim 1, further comprising a desulfurization net placed horizontally and fastened in the upper portion of the chamber and the tubular means is placed on said net.

8. The plant according to claim 1, further comprising a desulfurization net placed horizontally and fastened in the upper portion of the chamber and the tubular means is suspended from this net.

9. The plant according to claim 1, wherein the tubular means is composed of a material which is resistant to a humid and corrosive atmosphere.

10. A process for producing at least partially desulfurized biogas, using a plant according to claim 1, comprising: injecting biomass into the digester; injecting an oxidizing gas into the gas space of the digester via the system for injecting oxidizing gas; and mixing the biomass.

11. The process according to claim 10, wherein the oxidizing gas is oxygen or air or enriched air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0023] FIG. 1 is a cross-sectional view of the biogas flows in a laminar mode;

[0024] FIG. 2 is a perspective view the biogas flows in a laminar mode; and

[0025] FIG. 3 is a horizontal schematic section through the chamber of the digester.

[0026] Note that the section is taken in the portion of the inner wall of the chamber located at the level of the gas space.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] Depending on the case, the plant according to the invention may have one or more of the features below:

[0028] each square of the grid pattern comprises a micro-injector on one of its sides.

[0029] each square of the grid pattern comprises a micro-injector on each of its sides.

[0030] the grid pattern comprises at least four squares.

[0031] at least one micro-injector is located less than two metres from the axis of symmetry of the chamber.

[0032] the tubular means is located less than one metre from the gas space-biomass interface.

[0033] the plant comprises a desulfurization net placed horizontally and fastened in the upper portion of the chamber and the tubular means is placed on said net.

[0034] the plant comprises a desulfurization net placed horizontally and fixed in the upper portion of the chamber and the tubular means is suspended from this net. This suspension is preferably effected by means of ropes.

[0035] the tubular means is composed of a material which is resistant to a humid and corrosive atmosphere. Mention may be made by way of example of certain stainless steels, PEEK, PTFE.

[0036] The plant according to the invention makes it possible to more homogeneously distribute the injected doses of the oxidizing gas within the whole of the digester. The reactions will therefore no longer be localized, which makes it possible to better reduce the hydrogen sulfide in its entirety.

[0037] In addition, this more homogeneous distribution of the oxidizing gas within the gas space of the digester enables an optimization of the amount of oxygen used and makes it possible to reduce the consumption thereof. In the case of injecting air or enriched air, the amount of nitrogen in the biogas will thus be minimal.

[0038] A further subject of the present invention is a process for producing at least partially desulfurized biogas, using a plant according to the invention, comprising:

[0039] injecting biomass into the digester;

[0040] injecting an oxidizing gas into the gas space of the digester via the system for injecting oxidizing gas; and

[0041] mixing the biomass.

[0042] The injection rate of the oxidizing gas will preferably be between 0.3 and of the volume of the biogas produced.

[0043] Note that the oxidizing gas might be oxygen or air or enriched air. Enriched air refers to air having a higher oxygen content than the oxygen content normally present in air.

[0044] The solution according to the invention makes it possible to obtain a biogas stream comprising less than 200 ppm of hydrogen sulfide.

[0045] The invention makes it possible to reduce the costs of purifying biogas by removal of hydrogen sulfide effectively and without any need for complex engineering.

[0046] While 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 in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0047] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0048] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of comprising, Comprising is defined herein as necessarily encompassing the more limited transitional terms consisting essentially of and consisting of; comprising may therefore be replaced by consisting essentially of or consisting of and remain within the expressly defined scope of comprising.

[0049] Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0050] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0051] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, its to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range,

[0052] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.

[0053] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.

[0054] While embodiments of this invention have been shown and described, modifications thereof may be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments described herein are exemplary only and not limiting, Many variations and modifications of the composition and method are possible and within the scope of the invention. Accordingly the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims.