DE102004054468A1 - Anaerobic fermentation of vegetable substrates for production of bio gas, comprises extruding substrates to form high-grade homogenized biomass by double escargots extrude, and growing nutrient for mead producer by biogenous material - Google Patents

Abstract

The extruded coenzyme is fixed on a dung plate. The substrates are added into a reactor by an extrusion and a direct entry, which avoids a strong temperature gradient.

Description

The The invention relates to a process for the production of biogas by anaerobic fermentation of vegetable Substrates in a reactor.

The Invention is preferably applied in the field of agricultural Biogas. About that In addition, an appropriate use in the anaerobic waste and digested sludge fermentation possible, where a wide variety of biomass used as Koferment case by case can be.

Independent of the development of livestock and thus the seizure of liquid or festmist represents the reinforced Use of renewable raw materials and grassland growth is an appropriate alternative for recycling in agricultural biogas production.

at The known method for biogas production was an increase in Efficiencies in biomass conversion into electrical and thermal energy essentially by the further development of the fermentation technology, including the most diverse feeding techniques of solids as well the development of combined heat and power plants, but not by better Exploiting the biochemical energy bound in the biomass itself, sought.

in the Contrary to the animal excretions, in which there are no more cell associations because, when passing through the digestive tract of the carcass, the nutrient completely be opened up and offered the anaerobic bacteria a very large attack surface The plant cofactors are due to their cellular bonds of the bacteria much harder to decompose and require one decidedly longer Residence time in the biogas reactor.

in the State of the art are various methods and devices for crushing, mixing and shredding vegetable substrates high dry matter contents with combined direct entry into biogas reactors known.

all These methods are in terms of technical controllability high dry matter contents in the fermenter limits. The dry matter contents in slurry plants with proportional co-fermentation amount to between 10 and 12%.

In especially for grass or silage fermentation designed wet fermentation plants can with reinforced Rührwerkstechnik and corresponding input and Austragungsaggregaten a dry matter content from 13 to 15% are still mastered. At higher dry matter contents However, the homogenization of the septic tank substrate can no longer be ensured and there are increased levels of floating or grafting on, the disorders in the gas formation process.

In DE 203 17 305 U1 describes a device for rupturing, mixing and pumping in a single aggregate for the fermenter feed in biogas plants, which, although an improvement of previous crushing, mixing and Einbringtechnik represents, but does not realize cell disruption. The high risk of floating depending on the dry matter content remains.

It is also known higher Dry matter contents by direct input of vegetable biomass to realize in the bioreactor. This is achieved by that Einspülschächte different Type, feed screws, dosing stations with hydraulic injection, spiral conveyors or the system "solids wolf" the company PLAN ET.

Of the permanent warranty the flow and pumpability of the substrate and associated process stability are also limits set here. Likewise disadvantageous in all these devices the persistence of plant biomass for swimming and Sinkschichtbildung at comparatively higher energy and technical Effort for the use of agitator or homogenization technology.

To DE 198 00 224 C1 is the treatment of a pumpable mixture of biowaste and sewage sludge in a digester known, in which the dry matter content is increased in the suspension formed by sewage sludge by the addition of biomass in appropriate mixing ratios. The defibration of biowaste is considered to be advantageous.

For the biotechnical Further treatment of waste for the production of biogas, it is expedient to increase the Reaction rate of the organic biomass before separation to disintegrate organic components.

In DE 38 36 379 A1 For this purpose, an arrangement is described in which a ball mill is used for comminution. A secured cell disruption of the substrate takes place here only conditionally.

With the in DE 197 19 895 C1 solution is to increase the space load of fermentation reactors be achieved in that the sludges are subjected to mechanical thickening before fermentation.

Of the Invention is based on the object, a method of the initially with the type mentioned in the fermentation of organic dry substances from purely agricultural substrates an improved biogas yield based on a defined residence time at high Faulraumbelastungen is achieved.

According to the invention Task with a method which specified in claim 1 Has features solved.

advantageous Embodiments are derived in the subclaims.

at the method according to the invention it is a modified one-step wet fermentation process for biogas production with optimized gas yield at enhanced or exclusive use Vegetable biomass and their treatment-technical pretreatment by extrusion. The fermentation process becomes a processing technology Precursor outside preceded by the reactor, wherein by extrusion of the vegetable Substrates a highly homogenized biomass is produced, their cell structure largely destroyed is. Through targeted surface enlargement of the biogenic material will increase the fermentation and methanogenic bacteria allows for greater nutrient availability. This is a demonstrably greater gas formation rate reached.

Depending on the technological requirement, the extruded vegetable biomass can be fed to the reactor via a pre-pit or via a suitable direct introduction technique. In this case, dry matter contents> 18% or digester loads> 6 kg of organic dry matter / m ³ × d) can be permitted without any disruption in the gas formation process. This leads to the optimization and saving expensive foul space volume.

When Episode of the higher nutrient availability are the biogas yield per time unit and used organic Dry substance mass and the plant-specific biogas productivity with exclusive Use of renewable raw materials, manure and solid manure higher than previously known in agricultural biogas practice.

The highly homogenized biomass has a better pumping and transportability and only a slight tendency to swim and Sinkschichtenbildungen up and leaves thus extremely high Faulraumbelastungen too. Due to lower homogenization and agitator technology process energy is saved.

By Combination of bioextruder and direct entry, temperature gradient is avoided, what favorable affects the methane formation process and saves thermal energy helps.

By the high temperatures produced in the extruder become disease germs, Mushroom spores, weed seeds etc. destroyed and the fermented substrate has a lower germ load.

The Invention uses the thermomechanical digestion by means of extrusion, around the energy stored in the plant biomass for the actual Methane formation process faster and more efficient available too do.

• • Gras- und Maissilage
• • Festmist, Stroh
• • Grünschnitt und Getreide

wird für das Hydrolysestadium im Allgemeinen eine Vor- oder Maischgrube verwendet.By selecting and proportioning suitable plant biomass such as:

• • Grass and maize silage
• • Muck, straw
• • Green waste and cereals

For example, a pre- or mash pit is generally used for the hydrolysis stage.

at Abandonment of a pre-pit can the hydrolysis stage (in the beginning acidification stage) to be replaced by a "preparation" of the pretreated, extruded Kofermente on a dung plate (sufficient: 3-5 daily rations). Show Manure and Solid manure has an excellent chemical buffering effect.

By suitable solids introduction technique or thick matter pumps become very high dry matter contents introduced into the digester.

With the method according to the invention succeeds in the digestion room optimal reaction conditions and for the actual Methane production process favorable To create environmental conditions so as not to affect the overall process of fermentation Take care to have to.

• – Temperaturverhalten
• – pH-Wert
• – Äquivalente der leichtflüchtigen Fettsäuren
• – Erfassung der Stoffpotentiale und des C/N-Verhältnisses
• – Zusammensetzung und Menge des Biogases
• – Bestimmung der Trockensubstanz-Gehalte

This requires careful monitoring of the fermentation process, including the measurement and analysis of the following parameters:

• - Temperature behavior
• - PH value
• - Equivalents of the volatile fatty acids
• - Recording the substance potentials and the C / N ratio
• - Composition and quantity of biogas
• - Determination of dry matter contents

The treatment-related preliminary stage uses known extrusion technology. As beneficial has a twin-screw extruder, which is available as a further development from the wood fiberization.

In the flank areas of the worm shafts arise in the encapsulated and armored device, variable depending on substrate feed and consistency Pressure and temperature conditions, the are capable of cell structure of plant material and other biomass to explode.

at the forward movement of the substrate, it becomes thermomechanical due to the entering cross-sectional constriction so claimed that a desired Texture and texture change entry. The biogenic material is between the worm shafts and the outer wall grated and homogenized, thoroughly mixed and plasticized. By the extensive destruction of the cell structure creates a much larger attack surface for the microbes and thus an effective acceleration of the gas formation process.

in the Extruder channel are peak pressures above 50 bar possible, Temperatures> 120 ° C were measured.

By This process takes place such a cell disruption, the demonstrable to a much higher one and faster nutrient availability in the methane production process. This effect contributes Turbo character.

The results obtained in large-scale experiments are in the 1 and 2 explained in more detail. Showing:

1 the substrate-specific biogas yield as a function of the residence time
and

2 the gas productivity as a function of the foul space load.

As from the in 1 illustrated comparison of the course of the substrate-specific gas yields for untreated substrate and the extruder material according to the invention can be, rates of increase .DELTA.E could be determined up to 14%. Some of the resulting plant-specific income increases were in some cases more than 30%. This is made possible by the control of extremely high Faulraumbelastungen and optimized conditions for methane gas production.

2 shows the course of gas productivity in current biogas practice and when using the method according to the invention. The process-specific productivity optimum, at which the maximum gas productivity is achieved, results here for a digested space load FB in the range of 5 to 6 kg of organic dry matter / m ^{3 of} septic tank volume.

Regarding the energy balance becomes the energy-intensive treatment step through higher Biogas yields and gas productivities more than compensated.

The have fiber components still present after the extrusion process a length of up to 40 mm and remain due to their nature during insertion in the reactor liquid in limbo. This will create favorable conditions for effective Homogenization of the septic tank substrate created. It exists over others Technological procedures of wet fermentation a much lower Inclination of the pretreated plant substrate to process-endangering Floating and sinking layers.

The In the extruder resulting temperature of about 100 ° C corresponds to the requirements EUV 1774 on the sanitation of certain biowaste that is pathological be questionable. But since all Additives such as plant cut, plant waste, compost, etc. the extruder In addition to pathogens, other germs, such as fungal spores and weed seeds, are transmitted etc. partially destroyed. The fermented substrate is then when shipped as a fertilizer the fields are largely germ-free.

O

optimum

G

gas productivity

FB

Lazy loading rate

BG

biogas

oTS

organic dry matter

m ³ _F

Faulraumvolmen

d

Day

Claims (6)

Process for the anaerobic fermentation of plant substrates for the production of biogas, characterized in that to achieve a demonstrably higher gas formation rate the fermentation process upstream of a processing precursor outside the reactor by extrusion of the plant substrates so that a highly homogenized biomass is produced, the cell structure is largely destroyed and by targeted surface enlargement of the biogenic material a faster nutrient availability for the Metanbildner is made possible. A method according to claim 1, characterized in that the extruded vegetable biomass, depending on technological requirements, is fed via a pre-pit or via a suitable direct entry technique to the fermenter and such TS contents (<18%) or Fraulraumbelastungen (of> 6 kg oTS / m ³ × d) allows disturbances in the gas formation process to be avoided. Method according to claim 1 or 2, characterized that the extruded biomass by means of twin screw extrude so that will work better pumping and transportability biomass has only a slight tendency to swim. and Sinkschichtenbildung and thus allows extremely high Faulraumbelastungen. Method according to claim 1, characterized in that that extruded coferments are applied to a dung plate. Method according to claim 1, characterized in that that the vegetable substrates are combined into the reactor by Use of an extruder and direct entry are introduced. Method according to one of the preceding claims, characterized characterized in that to avoid a strong temperature gradient of the Material entry through combination of bioextrude and direct entry into the reactor.