DE3912418C1 - Degradation of hydrogen sulphide and fatty acids in bio-gas - by using chromatium species DSM 5080 together with rhodopseudomonas species FDSM 5020 in alkaline culture - Google Patents

Abstract

A strain of chromating spec DSM 5,080 is pref. used together with Rhodopseudomonas spec DSM 5,020 in an alkaline culture for the degradation of H2S and volatile fatty acids in a biogas inside an illuminated tubular reactor. ADVANTAGE - Biogas produced in an anaerobic plant is effectively freed from H2S and volatile fermentation prod.

Description

The invention relates to the elimination of sulfur Hydrogen and fermentation metabolites by means of a Mixed culture of phototrophic bacteria under anaerobic conditions conditions in light and a specific microorganism (see the claims).

The mixed bacterial culture of phototrophic bacteria is said to on the one hand malodorous short-chain volatile fatty acid and the proportion of toxic corrosive Hydrogen sulfide from the biogas operated anaerobically Remove bioreactors to remove the gas with a share of 75% methane for both combustion and electricity generation using gas engines.

It is known the proportion of hydrogen sulfide in biogas to decrease by either adding heavy ingredients a sulfide bilge (e.g. iron) in the reactor feed is initiated or via the addition of air sau inhibiting growth of desulfurizing Bacteria is brought about or by the sulfur biogas containing hydrogen over iron hydroxide Cleaning compounds is passed or by in a mic robust oxidation process through a sulfide oxidation to be led.

The process for lowering hydrogen sulfide in the Biogas by adding heavy metals in the biogas reactor has the disadvantage that the pollutant ver in the system remains. Air oxygen can be added in the presence of methane to an explosive mixture. Generate the processes for eliminating turf iron ore Iron sulfide as a waste.  

In microbial sulfide oxidation is a sulfate-containing waste water in the waste water cleaning process of the sewage plant returned so that renewed desulfurization under anerobic conditions can use.

The invention has for its object that the biogas of an anaerobic plant using microbial agents a phototrophic mixed culture under anerobic conditions in the light of hydrogen sulfide and volatile To clean fermentation metabolism products and to provide suitable microorganisms. The object is achieved in that Biogas through an alkaline mixed culture from phototro phen bacteria is directed (see claim 2). This will loosen sweat hydrogen sulfide, carbon dioxide and volatile organic Fatty acids in the mineral nutrient salt solution.

The strain Chromatium spec. DSM 5083 oxidizes hydrogen sulfide anaerobic in the light to elemental sulfur and stores him in this form in the cell. In the absence of sweat hydrogen sulfide occurs a further oxidation at the As simulation of carbon dioxide to sulfate.

Hydrogen sulfide can reach a concentration level richly utilized in the culture of 7.1 mg / l-14 mg / l will. The bacterial strain mainly uses radiation in the near infrared range between 700-800 nm.

The strain Rhodospeudomonas spec. DSM 5020 builds both anaerobically in Light as well as microaerobic in the dark low molecular weight organic decomposition products of the fermentation metabolism. He is also able to lower hydrogen sulfide Concentration in the range of 1.4 mg / l-2.8 mg / l im Oxidize light. The resulting sulfur becomes excreted in the culture and not in the cell saves. The strain produces during growth Biotin, the Chromatium spec. DSM 5083 as a growth substance serves. Rhodopseudomonas spec. DSM 5020 also predominantly uses Radiations in the near infrared range between 700-900 nm.  

The microbial degradation of the above Biogas pollutants in the culture solution takes place in a light-flooded Tube reactor.

It will become the subsequently pollutant-free culture solution now used for biogas washing.

The proportion of sulfuric acid as the end product of the microbi The degradation process is brought to the system by forming Calcium sulfate withdrawn.

The advantages achieved by the invention are special in that the process for biogas purification ge separates from that of the biogas production. To this Way, the microbial degradation can be optimized under  Conditions in an adjustable and controllable part of the system respectively.

Furthermore, the sulfur is egg to the system by generation recyclable material (as gypsum = calcium sulfate) withdrawn.

The bacteria are grown in a nutrient medium:
(mg / l): NaHCO ₃ : 0.8; NH ₄ CL: 0.1; MgSO ₄ x 7 H ₂ O: 0.08; CaCl ₂ × 2 H ₂ O: 0.01; K ₂ HPO ₄ : 0.2; Citric acid: 0.05; FeCl ₃ x 6 H ₂ O: 0.0005; Vitamin B ₁₂ : 0.0002; Hefeex trakt: 0.05; Na ₂ S x 9 H ₂ O: 0.25; Na acetate: 0.2; Tap water.

The static cultivation is applied in a high layer a temperature of 22-28 ° C, a pH of 7- 7.5 and an illuminance of 500-1000 lux in Light spectrum of a tungsten incandescent lamp carried out.

The cultivation period is 72 hours.

Examples of use

Methane gas from an anaerobic process reactor is passed through the mixed bacterial culture with a pH of 7.5-9. The hydrogen sulfide (H ₂ S) components of the biogas, the carbon dioxide (CO ₂ ) and the short-chain organic fatty acids are dissolved in the mineral nutrient solution.

To generate growth and elimination of harm the mixed culture loaded overflows in a circle a bypass through a light-irradiated tube craze  tor (500-1000 lux, tungsten lamp light) in one tempered section of the system.

After passing through the tube reactor, the above-mentioned. Harmful substances degraded microbially so that the nutrient solution can be reloaded in the gas scrubber section. The pH Value, temperature, nutrient salt content or mixed culture in of the plant are monitored and regulated.

Claims (2)

1. Spec. DSM 5083. 2. Use of the strain according to claim 1 in mixed culture with Rhodopseudomonas spec. DSM 5020 in alkaline culture to break down hydrogen sulfide and volatile fatty acids in biogas in a light-filled tube reactor.