DE102011051836A1 - Producing biogas comprises providing reactor with fillers, immobilizing methanogenic microorganisms on the surface of fillers, sprinkling fillers with nutrient solution, introducing gaseous substrates and discharging the biogas - Google Patents

Abstract

Producing biogas comprises: (a) providing a reactor fitted with fillers; (b) immobilizing methanogenic microorganisms (methane bacteria) on the surface of the fillers; (c) sprinkling the fillers with a nutrient solution for the micro-organisms along with the immobilized methanogenic microorganisms; (d) introducing gaseous substrates in the reactor for biogas production; and (e) discharging the biogas produced from the reactor. An independent claim is also included for a device for producing the biogas, comprising at least one biogas reactor, which is filled with fillers, where immobilized microorganisms are provided on the surface, a sprinkler for sprinkling the filler with a nutrient solution, an inlet for introducing the gaseous substrates into the bioreactor and a diverter to derive the resulting biogas.

Description

The invention relates to a method and a device for using gaseous substrates for the production of biogas and for reducing the hydrostatic pressure in biogas plants.

The use of only gaseous substrates for the production of biogas is previously unknown and unusual. There are only known applications in which in addition to the usual substrate (ie renewable resources, manure, etc.), a pressing of gases, including hydrolysis gas and hydrogen, is carried out in the biogas reactors to increase the yield of methane or undesirable gas components to convert biologically.

Therefore, gaseous substrates have so far played no role in the biogas production, because their volume was estimated to be very low and the pressing in biogas plants encounters technological problems: It must be applied a high pressure to the gases in the usual, filled with fermentation liquid Press in biogas reactors, and it is a very good distribution of gas bubbles required to ensure optimal mass transfer between gas and liquid.

The use of gaseous substrates is particularly interesting because now the complete conversion of a mixture of hydrogen and carbon dioxide in methane succeeds and thus serves the carbon dioxide as a carbon source for methane production. In addition, pyrolysis gases containing a variety of different hydrocarbons mixed with hydrogen, carbon monoxide and carbon dioxide can be converted into a gas mixture with the main component methane. Furthermore, there are other gases, eg. As waste gases from the heat treatment of food and beverages, as substrates available. However, these gaseous substrates must be free of molecular or atomic oxygen to avoid inhibition of the methane bacteria. The named potential gas streams are today often cleaned by means of aerobic (bio) filter or (bio-) scrubber consuming. There is no conversion into a usable high-energy end product (biogas).

Another problem with biogas production in all previously operated biogas plants or methane reactors is that these reactors are completely filled with liquid. According to the height of the liquid column, a hydrostatic pressure builds up, through the action of which the solubility of gases increases. Thus, it also increases the partial pressure of gases and as a result, the equilibrium shift in biogas formation. At high pressure, the gases (mainly methane and carbon dioxide) remain dissolved to larger proportions in the liquid, so are not removed and hinder the re-emergence of biogas.

The entry of the gases takes place via nozzles in finely divided form. By introducing mechanical energy, the formation of small gas bubbles can be supported.

The initially generated bubble size and distribution can not be maintained in all known methods. The gas bubbles rapidly agglomerate into larger ones and it is possible for true gas strands to form that only interact locally with the surrounding liquid.

The residence time of the gas in the liquid is determined by the bubble ascent rate and the height of the reactor, and may be controlled by internals which delay the bubble rise.

The feeding of the gas takes place at the bottom of the liquid column in order to obtain a sufficient residence time. However, for this, the hydrostatic pressure of the liquid column must be overcome so that higher performance compressors with a correspondingly high energy requirement must be used here. Since gases are compressible, a volume change work must be applied during compression, which is lost through the heating of the gas.

From the US 4,351,729 A For example, a biofilter and corresponding method is known for cleaning liquid organic wastes and waste gases. This waste is converted into carbon dioxide and other gases such as nitrogen or carbon dioxide, methane and other gases. Depending on the composition of the liquid organic waste or waste gases such as nitrous gases or nitrous oxide, the carbon contained therein is converted to carbon dioxide and the nitrogen contained therein to molecular nitrogen (N ₂ ). The production of biogas exclusively from gaseous starting products is not disclosed.

The object of the present invention is to overcome the disadvantages of the prior art.

The object is achieved by a method having the features of the main claim. Advantageous embodiments are characterized in the dependent claims.

The object is further achieved by a device for carrying out the method with the features of the independent device claim.

• a) Bereitstellen eines mit Füllkörpern versehenen Reaktors;
• b) Immobilisieren von methanbildenden Mikroorganismen („Methanbakterien”) an der Oberfläche der Füllkörper;
• c) Berieseln der Füllkörper mit den darauf immobilisierten methanbildenden Mikroorganismen mit einer Nährstofflösung für die Mikroorganismen;
• d) Einleiten gasförmiger Substrate für die Biogaserzeugung in den Reaktor;
• e) Ableiten des erzeugten Biogases aus dem Reaktor.

The invention relates to a process for the production of biogas, wherein the following steps are carried out:

• a) providing a packed reactor with a reactor;
• b) immobilizing methanogenic microorganisms ("methane bacteria") on the surface of the packing;
• c) sprinkling the fillers with the methane-forming microorganisms immobilized thereon with a nutrient solution for the microorganisms;
• d) introducing gaseous substrates for biogas production into the reactor;
• e) deriving the biogas produced from the reactor.

For the purposes of the invention, a nutrient solution means any liquid medium which contains components which are necessary for maintaining the living conditions for the microorganisms. This includes especially water. The nutrient solution preferably further contains nutrients such as N, P, S and metabolic trace substances.

In accordance with the invention, it is preferred in this case that, in addition to methane-forming microorganisms, an accompanying flora is immobilized on the packing in step b).

According to the invention, it is preferred that in step c) the nutrient solution for sprinkling continuously circulates.

According to the invention, it is preferred that in step d) the gaseous substrates selected from hydrogen, carbon dioxide, hydrocarbons, hydrocarbon compounds containing optional heteroatoms such as oxygen, nitrogen, sulfur or halogens, and mixtures thereof.

Substances which are preferred are essentially all gaseous substances which provide the constituents necessary for the formation of methane, namely carbon and hydrogen, in such a way that the constituents necessary for the formation of methane can be utilized by the methane-forming microorganisms.

According to the invention, it is preferred that in step d) the gaseous substrates are previously dissolved in the nutrient solution or in water or in another feed liquid.

In accordance with the invention, it is preferred that in step d) the gaseous substrates be conducted in cocurrent, countercurrent, crosscurrent or other flow variants relative to the nutrient solution.

According to the invention are therefore suitable as substrates all substances which are present in gaseous form or can be converted into the gaseous form. Thus, such substances can be used as substrates, which are liquid or solid at normal temperature, but are gaseous at the respective operating temperature in the bioreactor. Since methane-forming microorganisms at temperatures between about 0 ° C and 70 ° C, up to about 90 ° C metabolism, all substances and compounds are suitable as substrates, which have a boiling point in the vicinity of the maximum metabolic temperature of microorganisms, ie about 90 ° C.

When introducing or feeding substrates which are not gaseous at normal temperature, it may be advantageous to previously heat these substrates and to convert them into the gaseous state.

As substrates, therefore, in addition to hydrocarbons, compounds such as ethers, esters, alcohols, ketones or organic acids are suitable according to the invention and also preferred.

The invention thus relates to a process for the production of biogas in a biogas reactor, wherein in the bioreactor packing is provided, on the surface of which a biofilm is immobilized, which contains methane bacteria and possibly accompanying flora, and the packing is sprinkled with a liquid, wherein a liquid film forms on the surface of the filler. It is preferred that the liquid contains nutrients for the biofilm and / or substrates for biogas production. It is also contemplated that the substrates contained in the liquid are solids, liquids and / or gases. It is preferred that one continues to feed a gas into the bioreactor. It is preferred that one gas in relation to the liquid in the DC, in the countercurrent, in the cross flow or in other flow variants leads. It is preferred that the gas comprises gaseous substrates containing hydrocarbon compounds or carbon compounds and hydrogen.

The essence of the invention is thus the exclusive or almost exclusive use of gaseous substrates for the formation of biogas.

The invention also provides an apparatus for carrying out a method according to the invention, comprising at least one biogas reactor, filling bodies filled therein, at the ends thereof Surface immobilized microorganisms are provided, a sprinkler for sprinkling the filler with a nutrient solution; an introduction device for introducing the gaseous substrates into the bioreactor and a discharge device for discharging the biogas formed.

The invention thus also relates to a device for the production of biogas, comprising a biogas reactor, filled therein filler, wherein the filler carry on the surface of an immobilized biofilm, a feed device for liquids, which is designed such that it is the filler with the liquid such sprinkled to form a liquid film on the packing. It is further provided that the device further comprises at least one feed device for gases. It is advantageous that the biofilm contains methane bacteria and possibly accompanying flora.

In this case, a device is preferred, wherein the feed device for gases is arranged such that the gas in relation to the liquid in the DC, countercurrent, cross flow or other flow variants is feasible.

A bioreactor is proposed, which is filled with growth bodies (filler of hydrophobic plastic with a large volume-specific surface) on which an active biofilm has been immobilized. The biofilm contains both the methane bacteria and the necessary accompanying flora. However, the known arrangements of these biogas reactors are completely filled with liquid, which completely surrounds the filling bodies.

According to the invention, these random packings are then merely sprinkled with the microorganisms immobilized thereon (analogously to an aerobically operated trickling filter in sewage technology). The entire liquid in the reactor now forms a slowly flowing over the packing down liquid film. This liquid film provides the biofilm with sufficient water and nutrients. The elimination of the tensioned liquid eliminates the static pressure of the liquid column. The pressure inside the reactor is therefore almost constant, determined only by the system pressure applied from the outside (usually tens of mbar) and not by the liquid column (about 1 bar per 10 m height).

The interspace volume in the reactor is now empty of liquid or filled with gas. The (flowing) gas thus has a very low pressure drop. The residence time of the gas is determined only by the gas flow and no longer by the bubble ascent rate and can therefore be controlled in arbitrary orders of magnitude.

This system is suitable for both liquid and gaseous substrates. When using liquid substrates, the substrates and the nutrients are supplied to the microorganisms via the trickling down liquid.

When using gaseous substrates, the microorganisms are supplied by the liquid only with nutrients (macro and micronutrients), the substrate, however, is supplied as a gas.

Since the amount of liquid in the reactor is very low and the liquid is present as a surface film, there is a very good mass transfer between gas and liquid. Balance weights are set quickly. This is the prerequisite for the use of gaseous substrates, which diffuse from the gas into the liquid film and are transported from there to the microorganisms. The reaction products take the opposite route. The transport routes are extremely short (a few tenths of a millimeter), which is synonymous with a high process intensity.

When feeding the gaseous substrates no high pressure must be applied. Also, the gas formed can be removed with little pressure loss. Equilibrium shifts, as they occur in liquid-filled reactors due to the static pressure, do not take place here. In addition, the gas can be conducted in cocurrent, countercurrent, crosscurrent or other flow variants relative to the liquid. The reactors can have any shape, since they only have to bear the weight of the packing, but not a large amount of water. This allows a lower wall thickness and the cheaper foundation.

The advantage of the device according to the invention and of the method according to the invention consists in replacing the liquid column in a methane reactor with a liquid film. This is possible if a biofilm with the active bacterial mass can be immobilized on internals or packing in the reactor. Then only the living conditions of this biofilm have to be maintained, which does not necessarily have to be done by filling the entire reactor with liquid. A constant moistening of the biofilm and the supply of nutrients is sufficient.

The present invention thus has a number of advantages which overcomes the disadvantages described in the prior art.

In the prior art, in particular in the US 4,351,729 A , only the supply of Hydrogen for methane enrichment in the product gas described. According to the invention, the addition of carbon dioxide in addition to the hydrogen in the mixture or separately proposed, so that only with these gases, the product gas is formed. No additional liquid substrate is supplied (only the recirculation medium contained). Thus, there is no wastewater.

In addition, the invention provides to use alternative organic gases, which can also be converted to methane. This aspect is neither suggested nor suggested in the prior art.

In the present invention, a biofilm with accompanying flora is described. This biofilm has a layering of various microorganisms involved in the metabolism, which leads to a particular stability of the degradation process or of the entire reaction process in the reactor. This layering in a trickle bed reactor has not yet been described in the prior art.

Another novelty is that it is possible to change very quickly between different substrates. This is also not described yet.

The performance of such a system or the formation and stability of the biofilm is highly dependent on the mode of operation. In the prior art, no information or findings on the reflux ratio, liquid volume and volume loading in relation to the active biofilm surface have been described or their influence on the flow conditions in the trickle bed has been carried out. However, such adjustments can easily be carried out with the method according to the invention, since the growth conditions of the microorganisms can be optimally adapted. This is easily and readily possible for the person skilled in the art, since the sprinkling of the microorganisms takes place exclusively with a nutrient solution for precisely these microorganisms. Negative influences by liquid substrates are avoided.

Another advantage of the invention is the pressure reduction and the associated advantage of avoiding gas losses. This is not recognized in the prior art.

Another advantage of the invention is the almost complete controllability of biogas formation. In comparison to the previously described fixed-bed methane reactors, an increased controllability of the gas production is possible here, since the actual reaction space is significantly smaller, and after switching off the supply of substrate, the fading of the gas formation is significantly shorter. A rapid regeneration of the biofilm is possible because negative influences of the substrates on the growth of the biofilm can be stopped in the short term by shutting off the substrate supply.

Embodiment of the invention.

It is a reactor filled with previously seeded packing. In contrast to the known procedure, the reactor is not flooded with liquid, but evenly sprinkled from above with liquid, so that a liquid film runs down the packing.

Depending on the desired mode of operation, this liquid may contain the dissolved substrate - in this case the liquid is the hydrolyzate of an upstream hydrolysis stage - or else only the necessary micronutrients and macronutrients, wherein a gas is additionally supplied as a substrate.

• – Biogasanlagen, die mit Füllkörpern in der Methanstufe ausgerüstet sind
• – Windkraftanlagen
• – Kohlekraftwerken, um CO₂ nicht abzulagern, sondern zumindest teilweise energetisch zu verwerten
• – Produktionsanlagen mit organikreichen Abgasen.

With this arrangement, it is inventively provided to form methane from a carbon dioxide-hydrogen mixture. The carbon dioxide may, for. B. from combustion processes, the hydrogen could be obtained by means of excess energy (wind power!) In low load times by electrolysis. The carbon dioxide serves as a carbon source for methane formation. The device according to the invention and the method according to the invention can be used in the following fields of application:

• - Biogas plants equipped with fillers in the methane stage
• - wind turbines
• - Coal-fired power plants, not to deposit CO ₂ , but at least partially utilize energy
• - Production plants with organic exhaust gases.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4351729 A [0010, 0039]

Claims (7)

Process for the production of biogas, carrying out the following steps: a) providing a packed reactor with a reactor; b) immobilizing methanogenic microorganisms ("methane bacteria") on the surface of the packing; c) sprinkling the fillers with the methane-forming microorganisms immobilized thereon with a nutrient solution for the microorganisms; d) introducing gaseous substrates for biogas production into the reactor; e) deriving the biogas produced from the reactor. Process according to Claim 1, characterized in that, in addition to methane-forming microorganisms, an accompanying flora is immobilized on the packing in step b). Process according to Claim 1, characterized in that, in step c), the nutrient solution for irrigating is continuously circulated. A method according to claim 1, characterized in that one selects in step d) the gaseous substrates selected from hydrogen, carbon dioxide, hydrocarbons, hydrocarbon compounds containing optional heteroatoms such as oxygen, nitrogen, sulfur or halogens, and mixtures thereof. A method according to claim 1, characterized in that in step d), the gaseous substrates previously dissolved in the nutrient solution or in water or in another feed liquid. A method according to claim 1, characterized in that in step d), the gaseous substrates in relation to the nutrient solution in cocurrent, countercurrent, cross-flow or in other current variants leads. Apparatus for carrying out a method according to claim 1, comprising at least a biogas reactor, filling bodies filled therein, on the surface of which immobilized microorganisms are provided, a sprinkling device for sprinkling the filling bodies with a nutrient solution, an introduction device for introducing the gaseous substrates into the bioreactor and a discharge device for discharging the biogas formed.