DD282671A5 - PROCESS FOR ANAEROBFERMENTATION OF ORGANIC PRODUCTS - Google Patents

Abstract

The invention relates to a method for anaerobic microbiological waste product utilization, which is suitable, ammonia-containing aqueous dispersions and solutions with biodegradable organic substances, so agricultural waste, such as guellen, so waste products of the food industry, such as slaughterhouse and chemical by-products of the chemical industry to so-called biogas and to convert high quality natural fertilizer. The object is achieved by the fact that after the known substrate degradation to carboxylic acids a self-alkalization of the digested sludge can be exploited by the anaerobic fermentation in a surprising manner to remove from a portion of the circled reaction medium alone or in admixture with substrate, ammonia. The mixture can be fermented without the addition of disinfestants, so that biogas and high quality fertilizers are produced. {Biogas; microbiological waste product utilization; anaerobic fermentation; ammonia-containing organic waste products; unprocessed processing of waste products; Fertilizer; Sludge}

Description

Field of application of the invention

The invention relates to a method for anaerobic microbiological waste product utilization, which is suitable ammonia-containing aqueous dispersions and solutions with biodegradable organic substances, so Abprodukte dor agriculture, such as manure, so Abprodukte the Lebensmitteiindust ie, slaughterhouse waste and chemical by-products undiluted to so-called biogas and high quality natural fertilizers.

Characterization of the known prior art

It is well known that organic St iffe, preferably waste products from various production branches, microbiologically under anaerobic conditions in a high-quality combustible gas, so-called biogas can be converted. The decomposition of the organic components, mainly carbohydrates, proteins and fats, takes place in two stages. So-called acid-forming bacteria break down the carbohydrates, proteins and fats into low-molecular-weight fatty acids, which are then further converted into methane and carbon dioxide in a second stage by premature bacteria. It is also generally known that an increasing ammonia or ammonium content first inhibits the methane-forming microorganisms and irreversibly damages them at high ammonia or ammonium concentrations. The ammonia or ammonium concentration is differently tolerated by the methane-forming microorganisms depending on the environmental conditions, such as buffering efficiency of the substrate, pH, etc. Cold water (B.J. cold water: Biogas regenerative energy production by anaerobic fermentation of organic waste in biogas plants, Bauverlag Berlin 1980) indicates a dependence of sogenann.en Ammoniaktoxizität for ammonium or ammonia-containing substrates, from which it appears that with increasing pH values z. B. from 7.5 to 8.0 a large increase in the ammonium toxicity is observed. Furthermore, it is known that waste products with high ammonium or ammonia concentrations can be fermented anaerobically only if this inhibitor concentration is lowered by dilution with water or wastewater (E. Scheurer: Studies on anaerobic degradation of chicken manure, Dissertation University of Hohenheim 1986) However, this dilution increases din for the mesophilic or thermophilic fermentation to be heated liquid amount of the substrate and the then to be used Faulgutmenge strongly what u. a. adversely affects the amount of heating energy, the reactor size and the Transportkostr η.

It is known that ammonia can be eliminated from dilute solutions. There are basically 3 methods in use:

- The distillati »" «removal of alkaline ammonia-containing liquids DE PS 3520934

- Alkalization by means of bases, such as AiKaIi- or alkaline earth and gas stripping of ammonia from ammonia-containing liquids DE OS 2722419

- The coupling of alkalization and steam stripping for removal of ammonia DE OS 2911745, DE OS 2722559.

In DE Patent 2952794 the possibility of coupling of alkalization and Dampfstrippung for removing ammonia for liquid manure is described.

Ammonium or ammonia-containing organic products in most cases react by the above-mentioned. first step of substrate degradation to carboxylic acids neutral or slightly acidic.

From these substrates ammonia can be separated only after alkalization by stripping in the manner described.

However, this method requires the use of molar amounts of bases, based on the ammonia to be separated.

Object of the invention

The aim of the invention is to develop a novel ana ibes mikrobii'ogisches method that he. allows ammonium- or ammonia-containing aqueous dispersions .indepositions containing biodegradable organic substances, so agricultural by-products, such as manure, so waste products of the food industry, such as slaughterhouse waste and chemical by-products convert undiluted to biogas and high-quality fertilizers and thereby the Separate ammonia contained.

Explanation of the essence of the invention

The object of the invention is to develop a novel process for anaerobic microbial fermentation ammonium- or ammonia-containing aqueous dispersions and solutions containing biodegradable organic substances, which allows the substrate undiluted to convert biogas and high quality fertilizers and the ammonia contained partially or completely separate.

According to the invention the object is achieved in that after the known substrate degradation to carboxylic acids at temperatures of 0-65 ⁰ C, a self-alkalization of the digested sludge can be surprisingly exploited by the anaerobic fermentation to from a portion of the stripped reaction medium alone or in admixture with substrate, by Steam or gas stripping to remove ammonia. The both ammonium or ammonia-reduced mixture, as well as the ammonium or ammonia-reduced part of the digested sludge can be fermented alone or in admixture with ammonium or ammonia-rich substrate after recycling in the reaction system without the addition of diluents, so that biogas and high-quality fertilizers arise.

The self-alkalization is effected by the fact that in the anaerobic fermentation organic acids are converted to methane and carbon dioxide, which leave the reaction system as gases. As a result, the pH increases during the fermentation. For strongly ammonium- or ammonia-containing substrates, a pH rise to more than 7 causes self-alkalization. Although the ammonia toxicity for the microorganisms is enhanced by this rising pH value, only the combination of the ammonia stripping at high pH values from part of the digested material before or after mixing with ammonium- or ammonia-rich substrate makes a microbial anaerobic fermentation of the substrate possible without thinner. In the case of substrates containing little ammonium or ammonia, self-alkalization occurs only after buffering of the fresh substrate with alkali or alkaline earth bases and subsequent fermentation. D mach ammonia stripping is possible even at low ammonium or ammonia concentrations.

embodiments

example 1

In a biogas reactor of 201 content and a reaction volume of 181, chicken manure is fermented continuously at a temperature of 35 ° C. The reactor is charged every 0.6 hours with 0.6! Fed chicken manure, so that an average mean residence time. the reaction time of 30 days. The chicken manure used has the following properties:

- Concentration of the solids content 22.3Ma .-%

- Concentration of the organic solids content 16.2Ma .-%

- Concentration of free ammonia 11,0g / l

- Concentration of volatile organic fatty acids, based on acetic acid 19.7g / l. The dosage is carried out as follows:

0.31 digested sludge are removed from the reactor and mixed with 0.61 fresh substrate. This mixture is subjected to steam distillation. 65.0 ml of condensate with an ammonia content of 6.0 g are obtained. The mixture, which is depleted in its ammonium or ammonia content, is added to the reactor for fermentation and 0.235 l of digested sludge are drawn off to maintain the constancy of the reaction volume. The reactor produces 50, oil biogas in 24 hours. The ammonium or ammonia content in the digestate varies between 4.5-6.5 g / l. The pH of the digested sludge has risen from 6.5 to 8.4 due to self-alkalisation as a result of the fermentation compared to the fresh substrate despite ammonia separation.

Example 2

In a biogas reactor of 20, oil content and a reaction volume of 18.01 Kühnergülle is continuously fermented at a temperature of 35 ⁰ C. The reactor is charged with 0.61 chicken slurry every 24 hours to give an average mean residence time of the reaction mass of 30 days. The chicken manure used has the following properties:

- Concentration of the solids content 22.3Ma .-%

- Concentration of the organic solids content 16.2% by mass

- Concentration of free ammonia 11,0g / l

- Concentration of volatile organic fatty acids, based on acetic acid 19.7g / l.

The dosage is made by taking 11 digested sludge. This digested sludge is subjected to ammonia stripping in vacuo at 35 ^° C. 75 g of distillate with an ammonia content of 6.5 g are obtained. The ammonia- or ammonia-reduced sludge is mixed with 0.31 fresh substrate to improve its flow properties and added to the reactor. To maintain the constancy of the reaction volume, 0.225 l digested sludge is removed from the reactor.

Example 3

In a biogas reactor of 20I content and a reaction volume of 181, a mixture consisting of 40% homogenised slaughterhouse waste and 60% pig slurry is continuously fermented. The substrate mixture has the following ^c; characteristics:

- Concentration of the solids content 7.1 Ma .-%

- Concentration of the organic solids content 6.05Ma .-%

- Concentration of ammonium or ammonia nitrogen 4.5g / l

- Concentration of volatile organic fatty acids, based on acetic acid 8.2 g / l

- pH word 6.5.

The dosage is carried out as follows:

The reactor is supplied to a substrate mixture quantity of 1.81 and thus realized an average residence time of 10 days. This substrate is raised to a pH of 6.8 by adding 2 g of soda or lime. This pH increase is sufficient to self-alkalinize to pH 8.0 as a result of the fermentation. In order to maintain the constancy of the reaction volume, 1.81 digested sludge are taken from the reactor. This digested sludge is subjected under vacuum at 4O ⁰ C an ammonia stripping. 120 ml of a solution containing 8 g of ammonia are recovered. The reactor produces 37.21 biogas in 24 hours.

Claims (8)

1. A method for anaerobic microwave fermentation ammonium or ammonia-containing aqueous dispersions and solutions containing biodegradable substances, characterized in that after the known Substatabbau to carboxylic acids at temperatures of 0-65 ⁰ C, a self-alkalization of the reaction medium and thus associated increase in the pH to about 7 is used to convert the present in the substrate as ammonium salt or organically bound nitrogen into volatile ammonia, separate with physical separation methods to ferment so undiluted substrates with nitrogen loaded j can. 2. The method according to claim 1, characterized in that a part of the digested by microbiological fermentation self-digested digested sludge, its ammonia content is reduced to 0.1-8.0 g / l, preferably 1.0-4.0 g / l and then is returned to the reactor. 3. The method according to claim 1 and 2, characterized in that a part of the di¬ rch the microbiological fermentation self-alkalinised digested sludge is recirculated · mixed with fresh substrate in such a ratio that this mixture gisrt alkaline, separated therefrom ammonia, and Mixture is then added to the reactor again. 4. The method according to claim 1-3, characterized in that by raising the pH in FrischsubsLrat until its neutral reaction by the addition of alkali or Erdalkalibasen a Selbs'calkalisierung by the microbial fermentation is made possible. 5. The method according to claim 1-4, characterized in that is separated from the self-alkalized by the microbial fermentation digested sludge after its removal from the reaction system for environmental relief ammonia. 6. The method according to claim 1-5, characterized in that the separation of ammonia takes place by stripping with an inert gas or water vapor. 7. The method according to claim 6, characterized in that the ammonia separation takes place by reducing the pressure to the volatility of the ammonia. 8. The method according to claim 1-5, characterized in that in the application e'nes thermal Ammoniaabtrennverfahrens Q ^: e heating of the ammonia-rich part of Reai. System through the ammonia-poor part of the reaction system takes place.