DE102005025040A1 - Preparation of methane-rich biogas comprises anaerobic fermentation of biomass and/or other substrates to raw fermentation gas, biochemical desulfurization of the gas, and photo-biological carbon dioxide reduction of the desulfurized gas - Google Patents

Abstract

Preparation of methane-rich biogas comprises: anaerobic fermentation (1) of biomass and/or other substrates to raw fermentation gas (5), where the process liquid is enriched with oxygen and at least a part of the oxygen comes from an oxygen-enriched, methane-rich fermentation gas (7); biochemical desulfurization (2) of the produced raw fermentation gas; and photo-biological carbon dioxide reduction (3) of the desulfurized fermentation gas, where oxygen-enriched, methane-rich fermentation gas and algal biomass (14) are produced. Preparation of methane-rich biogas comprises: anaerobic fermentation (1) of biomass and/or other substrates to raw fermentation gas, where the process liquid is enriched with oxygen and at least a part of the oxygen comes from an oxygen-enriched, methane-rich fermentation gas (7) that is produced in a photo bioreactor; biochemical desulfurization (2) of the produced raw fermentation gas, results in a separable methane-rich fermentation gas (8) and desulfurized fermentation gas (6);and photo-biological carbon dioxide reduction (3) of the desulfurized fermentation gas, where oxygen-enriched, methane-rich fermentation gas and algal biomass (14) are produced, after which the oxygen-enriched, methane-rich fermentation gas is led to the process of biochemical desulfurization. An independent claim is included for a plant for the production of methane-rich fermentation gas comprising at least a biogas container, a biochemical desulfurization container and a photo-bioreactor container.

Description

The The invention relates to a method and apparatus for generating methane-rich biogas, whereby the raw biogas used as starting material produced by anaerobic fermentation of biomaterial and / or substrate mass and then this raw biogas a biochemical desulfurization and photobiological carbon dioxide Reduction is subjected.

• – anaerobe Fermentation von Biomasse und/oder Substraten zu Rohbiogas,
• – biochemische Entschwefelung des gewonnenen Rohbiogases, wobei entschwefeltes Biogas entsteht und
• – photobiologische Kohlendioxid -Reduzierung des entschwefelten Biogases, wobei methanreiches Biogas und Algenbiomasse entstehen.

Such a process for producing methane-rich biogas comprises at least the steps

• - anaerobic fermentation of biomass and / or substrates to produce raw biogas,
• - biochemical desulphurisation of the raw biogas produced, whereby desulfurized biogas is produced and
• - Photobiological carbon dioxide reduction of the desulphurised biogas, producing methane-rich biogas and algal biomass.

The Device for producing methane-rich biogas comprises at least a biogas plant, a biochemical desulphurisation plant and a Photobioreactor.

biogas Being an environmentally friendly source of energy is becoming increasingly important to cover the energy demand in the global sense. It arises in the anaerobic Fermentation of organic waste and renewable raw materials.

The Main components of such a biogas are methane with approx. 65 % By volume and carbon dioxide with approx. 35% by volume. Biogas is a water vapor saturated Mixed gas and contains in addition to the two main components also small amounts (about 1 vol. %) Nitrogen, hydrogen, hydrogen sulfide and ammonia.

at optimized anaerobic fermentation process, eg. B. two-stage Methane content of 65 to 75% by volume is achieved.

Under methane-rich biogas is in the context of the invention with a biogas a methane content of more than 75% by volume understood. This methane rich Biogas has a carbon dioxide content less than 25% by volume and an oxygen content of less than 5% by volume. The sulfur content (H2S) is less as 0.1% by volume.

• • Verbrennung in Gaskesseln (Wärmeerzeugung),
• • Verbrennung in Gasmotoren (Stromerzeugung) und
• • Einspeisung in Gasversorgungsnetze (z.B. Erdgasnetz).

Biogas is basically used for:

• • combustion in gas boilers (heat generation),
• • combustion in gas engines (power generation) and
• • Feed into gas supply networks (eg natural gas grid).

at the aforementioned, different types of utilization must required equipment and the biogas quality be coordinated with each other. As a rule, a gas treatment, especially desulfurization, necessary.

Becomes Biogas (raw biogas) is not desulfurized before combustion, is the Operating time of boilers and gas engines due to corrosion under normal Conditions limited to approx. 2 to 3 years.

The Infeed of untreated, in particular not desulphurised Biogas (raw biogas) in gas supply networks is therefore regularly excluded.

to Biogas desulfurization become adsorption and absorption processes used.

In The last few years will be economic establish reinforced biochemical desulfurization applied.

The in the anaerobic fermentation biogas contains in the Usually no oxygen or only small amounts.

Of the for the biochemical oxidation necessary oxygen is therefore the to be desulfurized biogas mixed, which is usually by air he follows. It should be noted that the specific air entry by the lower explosion limit of the combustible components in the Biogas is limited. In addition to the explosion hazard is the inerting of biogas due to the nitrogen input with the air adversely.

Of the Carbon dioxide content of the untreated biogas is about 30 to 40 vol.%. Becoming present Adsorptive and absorptive carbon dioxide removal method used.

In recent years, the use of photobioreactors for carbon dioxide removal in a number of patent applications, for example in the DE 297 08 955 U1 , described.

carbon dioxide is converted photobiologically into biomass. This process produces oxygen in the photoreactor.

From the DE 197 21 243 C2 (or the DE 297 08 955 U1 ) is a method and a device for efficient energetic and material use of biogas known in this method, the carbon dioxide from the biogas produced in a biogas plant and desulfurized biogas in an algae reactor is removed. In the algae reactor low-carbon and oxygen-enriched biogas is a fermenter for PHB production and / or combustion fed system. The algal biomass from the algae reactor can be fed to the biogas plant.

adversely it is that the algal biomass fermented unaufgeschlossen and thus only a small biogas yield is achieved.

One Another disadvantage is the oxygen content in the methane-enriched Biogas for the feed into a gas supply network.

task The invention is a method and an apparatus for generating to provide methane-rich biogas that is an efficient energetic and material use of biogas.

The The object of the invention is achieved by a method according to the features of claim 1.

essential to the invention is doing that in the multi-stage desulfurization process oxygen out the oxygen-enriched, methane-rich biogas, which in a Photobioreactor is generated, is supplied.

In order to is achieved that in the photobiological carbon dioxide reduction resulting oxygen for the biochemical desulfurization is used and at the same time the Methane concentration in biogas is increased.

The detrimental oxygen supply through a monitored ventilation for desulfurization not necessary.

in the Compared to the prior art, the invention in the Photobioreactor derived algal biomass, e.g. through ultrasound, open-minded to higher yields in anaerobic fermentation to achieve. The oxygen formed in the photobioreactor is used for the biochemical Desulfurization used and at the same time removed from the biogas. The result is a methane-rich biogas that as a high-quality energy source and / or can be used materially.

Prefers is that the digestion of the algal biomass and / or additional Substrate takes place, which is fed to the anaerobic fermentation or will. Will be digested biomass and / or substrate in the Process step of the anaerobic fermentation of bio and / or substrate mass to Fed to raw biogas, is a particularly efficient generation of biogas allows.

Especially it is preferred that the biomass digestion by ultrasound and / or mechanically.

The The object of the invention is also achieved by a system according to the features of claim 4 solved.

The The object of the invention is also by a method for the biochemical desulphurisation of raw biogas according to the features of claim 6 and a plant for biochemical desulfurization of raw biogas according to the characteristics of Claim 7 solved.

Advantageous embodiments The invention are specified in the further subclaims.

The The invention is described below using an exemplary embodiment with reference to drawings explained in more detail.

It demonstrate:

1 a schematic representation (system principle) of the plant according to the invention for the production of methane-rich biogas and

2 a schematic representation of a plant for biochemical desulfurization of raw biogas.

1 shows the plant principle of the plant according to the invention for the production of methane-rich biogas in a preferred embodiment with an integrated stage of Biomass digestion.

• • Anaerobe Fermentation 1 zur Biogaserzeugung,
• • Biochemische Entschwefelung 2,
• • Kohlendioxidentfernung 3 in einem Photobioreaktor 3.1 und
• • Biomasseaufschluss 4.

This plant for the production of methane-rich biogas comprises the following stages:

• • Anaerobic fermentation 1 for biogas production,
• • Biochemical desulfurization 2 .
• • carbon dioxide removal 3 in a photobioreactor 3.1 and
• • biomass digestion 4 ,

The biogas production of raw biogas 5 takes place in the usual way in the first stage, anaerobic fermentation 1 , in a biogas plant known in this regard 1.1 (Fermenter) for biogas production. In particular, such substrates of fermentation 1 fed, which are well usable without digestion 15 and / or are open-minded 16 ,

In the second stage, the raw biogas produced in the first stage is recovered 5 desulfurized. (This biochemical desulfurization 2 is in 2 and is described separately below.) The biological desulfurization 2 closes a known carbon dioxide removal 3 , here in a photobioreactor 3.1 , as the third stage.

This is done in the desulfurized biogas 6 containing carbon dioxide in a photobioreactor 3.1 metabolized. Algae are used in a known manner as carbon dioxide recyclers. The result is an oxygen-enriched, methane-rich biogas 7 ,

This oxygen of the oxygen-enriched, methane-rich biogas 7 is used in biochemical desulfurization 2 used for hydrogen sulfide oxidation. The desulphurised, low-carbon dioxide-free and methane-rich biogas 8th is separated in the usual way and thus supplied to a recovery or use.

Photobiological carbon dioxide conversion produces (algae) biomass 14 , This is from the photobioreactor 3.1 carved out and in another stage, the biomass digestion 4 For example, by means of an ultrasonic flow cell or a ball mill, open-minded. The digested biomass 16 becomes biogas production 1 used. The digestion of further substrates 9 is possible.

2 shows a schematic representation of a plant for the biochemical desulfurization of raw biogas.

The biochemical desulfurization 2 of the raw biogas 5 takes place in a two-stage system.

The oxygen required for the biological oxidation becomes the raw biogas 5 indirectly, dissolved in the process liquid fed.

The oxygen absorption and the hydrogen sulfide oxidation is carried out separately in two separate reactors 10 ; 11 ,

The two reactors 10 ; 11 , Preferably packed columns are traversed in the circulation of the process liquid. In the first stage, the absorber 10 , the oxygen absorption takes place in the process fluid 12 , The oxygen-enriched biogas 7 from the photobioreactor 3.1 and the oxygen-poor process fluid 12 be in dc through the absorber 10 guided. With the oxygen-enriched process fluid 13 that the absorber 10 leaves the oxygen in the second stage, a bioreactor 11 , transported. The bioreactor 11 is in cocurrent of the oxygen-rich process fluid 13 and of the raw biogas to be desulphurised 5 flows through. The hydrogen sulphide is converted biochemically. For the hydrogen sulfide oxidation chemolithotrophic bacteria are suitable. The oxidation products sulfur and sulfuric acid are mixed with the process fluid 12 from the bioreactor 11 removed from circulation.

Around a salting of the process fluid To avoid this, a part of the liquid is cyclically replaced by new nutrient solution. As a nutrient solution can diluted Manure used become. It contains the for the Hydrogen-oxidizing microorganisms necessary nutrients.

The discarded low-oxygen process fluid 12 gets into the absorber 10 entered and again with oxygen from the oxygen-enriched biogas 7 enriched.

In case of occlusion of the bioreactor 11 by deposited sulfur and / or biomass is the gas supply ( 5 and 6 ) of the bioreactor 11 with the gas guide ( 7 and 8th ) of the absorber 10 switch. The change of the gas guides allows a regeneration of the blocked system.

Claims (8)

Process for producing methane-rich biogas, at least comprising the steps of: o anaerobic fermentation ( 1 ) from biomass and / or other substrates to raw biogas ( 5 ), o biochemical desulphurisation ( 2 ) of the recovered raw biogas ( 5 ), wherein in a first stage the process liquid ( 12 ) is enriched with oxygen and at least a part of this oxygen from the oxygen-enriched, methane-rich biogas ( 7 ), which in a photobioreactor ( 3.1 ) is produced, and in a second stage, the biochemical desulfurization takes place and methane-rich biogas ( 8th ), which can be distinguished, and desulfurized biogas ( 6 ) and o photobiological carbon dioxide reduction ( 3 ) of desulphurised biogas ( 6 ), wherein oxygen-enriched, methane-rich biogas ( 7 ) and algal biomass ( 14 ) and oxygen-enriched, methane-rich biogas ( 7 ) of biochemical desulphurisation ( 2 ) is supplied. Process according to claim 1, characterized in that a biomass digestion ( 4 ) of the algal biomass ( 14 ) or in addition to substrate ( 9 ), which of the anaerobic fermentation ( 1 ) is or will be supplied. A method according to claim 2, characterized in that the biomass and / or substrate digestion ( 4 ) by ultrasound and / or mechanically. Plant for the production of methane-rich biogas according to a method according to claim 1, this plant at least comprising a biogas plant ( 1.1 ), a biochemical desulphurisation plant ( 2.1 ) and a photobioreactor ( 3.1 ). Plant according to claim 4, characterized in that the plant is a plant for biomass and / or substrate digestion ( 4.1 ). Process for the biochemical desulphurisation of raw biogas ( 5 ), wherein in a first stage, the process liquid is enriched with oxygen and at least a portion of this oxygen from the oxygen-enriched, methane-rich biogas ( 7 ), which is in a photobioreactor ( 3.1 ) and in a second stage biochemical desulphurisation ( 2 ) he follows. Plant for biochemical desulphurisation ( 2.1 ) of raw biogas according to a method according to claim 6, wherein said plant comprises at least one photobioreactor ( 3.1 ) and a biochemical desulphurisation plant ( 2.1 ). Plant according to claim 7, characterized in that the biochemical desulphurisation plant ( 2.1 ) at least two reactors ( 10 ; 11 ), whereby through the first reactor ( 10 ), an absorber, oxygen-poor process solution ( 12 ) and oxygen-enriched, methane-rich biogas ( 7 ) are conducted in cocurrent, and low-oxygen, methane-rich biogas ( 8th ) leaves the plant and oxygen-rich process solution ( 13 ) into the second reactor ( 11 ), which is a bioreactor, is passed, and wherein through the second reactor ( 11 ) oxygen-rich process solution ( 13 ) and raw biogas ( 5 ) and desulfurized biogas ( 6 ) the bioreactor ( 11 ) and the biochemical desulphurisation plant ( 2.1 ) and the resulting low-oxygen process solution ( 12 ) in the first reactor ( 10 ) to be led.