CN103773807B - A kind of method of utilizing nano magnetite to improve anaerobism product methane efficiency - Google Patents

Abstract

The invention belongs to biomass energy source domain, relate to a kind of method of utilizing nano magnetite to improve anaerobism product methane efficiency. Using SCFA as electron donor, nano magnetite is as electron carrier, under anaerobic fermentation condition of culture, and short-chain fat acid degradation and then make system syntrophism oxidation produce methane efficiency. Adopt the inventive method can significantly improve the efficiency of energy utilization of SCFA. The present invention is significant to the operational efficiency of raising methane-producing reactor, has good economic benefit simultaneously.

Description

A method for improving the efficiency of anaerobic methane production by using nano-magnetite

technical field

The invention belongs to the field of biomass energy, and relates to a method for improving the efficiency of anaerobic methane production by using nano-magnetite.

Background technique

Mutualism is a closely linked mutualistic cooperative behavior among different microbial species, and it is an essential part of the methanogenic ecosystem. Mutualism plays a very important role in the anaerobic fermentation methanogenic system. The conversion of short-chain fatty acids (such as propionic acid and butyric acid) into methane requires the indirect force between mutualistic bacteria and methanogens, which is through interspecific electron transfer. to realise.

In the anaerobic methanogenesis system, the interoperability relationship mainly exists between interoperating bacteria and methanogens. It is generally believed that during the methanogenic process, short-chain fatty acids (such as propionic acid and butyric acid) produced by acidogenic fermentative bacteria transforming macromolecular organic matter (such as carbohydrates and lipids) are degraded by interoperating bacteria and become substrates for methanogenic bacteria. (acetic acid, hydrogen and _CO2 ). However, under standard conditions, the oxidation of short-chain fatty acids by syntrophic bacteria to acetic acid is an endothermic reaction, which cannot be carried out thermodynamically spontaneously. They need to establish a mutualistic relationship with methanogens to complete the conversion from short-chain fatty acids to methane. Therefore, the acetogenic step in the oxidation of short-chain fatty acids is the rate-limiting step in the methanogenic process.

For a long time, researchers have believed that _H2 or formic acid can be used as a carrier for interspecies electron transfer to complete the degradation of short-chain fatty acids to produce methanogenesis. However, due to the limitation of the diffusion rate of _H2 or formic acid in the solution and the influence of agitation during fermentation, the spatial distance of the syntrophic flora largely limits the efficient and rapid transformation of organic matter. Therefore, this form of interoperability greatly limits the rate of the biogas fermentation process, resulting in an excessively long biogas fermentation cycle and increasing the operating cost of the biogas project.

In summary, there is an urgent need to develop a methanogenic process that does not use _H2 or formic acid as an electron carrier, which is of great significance for breaking through the thermodynamic barriers in the degradation of organic matter and ensuring efficient and fast operation of anaerobic digestion reactors.

Contents of the invention

The object of the present invention is to provide a method for improving the efficiency of anaerobic methane production by using nano-magnetite.

In order to achieve the above object, the technical solution adopted by the present invention is:

A method for improving the efficiency of anaerobic methanogenesis by using nano-magnetite. Short-chain fatty acids are used as electron donors, and nano-magnetite is used as an electron carrier. Under anaerobic fermentation conditions, short-chain fatty acids are rapidly degraded to improve the system Methanogenic Efficiency of Mutual Oxidation.

Furthermore, anaerobic digested sludge or paddy soil is used as inoculum, short-chain fatty acid as electron donor and nano-magnetite as electron carrier are sequentially added to the medium, under the conditions of pH = 7.0 and 30-37 ° C , anaerobic fermentation of methane.

The composition of the medium is: NaH ₂ PO ₄ ·H ₂ O 1g/L, Na ₂ HPO ₄ ·H ₂ O 0.55g/L, NaHCO ₃ 3g/L, CaCl ₂ 275mg/L, NH ₄ Cl 310mg/L, MgCl ₂ 330 mg/L, KCl 130 mg/L, MnSO ₄ 6H ₂ O 5 mg/L, FeSO ₄ 7H ₂ O 10 mg/L, CuSO ₄ 5H ₂ O 0.1 mg/L, CoCl ₂ 5H ₂ O 1 mg/L, NiSO ₄ 28 -42 mg/L, ZnCl ₂ 1 mg/L, H ₃ BO ₃ 0.1 mg/L, Na ₂ MoO ₄ 0.25 mg/L, NiCl ₂ .6H ₂ O 0.24 mg/L and EDTA 1 mg/L.

1-10g of electron donor, 1-4g of magnetite and 10-20g of inoculum are sequentially added to each liter of culture medium.

Wherein, electron donor is propionic acid and/or butyric acid (propionic acid and butyric acid can be mixed in any ratio); Magnetite final concentration is 1-4g/L, and diameter is 5-50nm; Inoculum final concentration is 10 -20g/L.

The advantages that the present invention has:

1. The present invention utilizes nano-magnetite to produce methane, which significantly improves the energy utilization efficiency of short-chain fatty acids, maintains the stability and high-speed operation of the methanogenic reactor and can significantly increase the methane content in the biogas component, and then increases the methane concentration .

2. Adopt the method of the present invention to make short-chain fatty acids (as propionic acid, butyric acid) degrade rapidly, thereby solve this bottleneck problem of the thermodynamic restriction that short-chain fatty acid degradation such as propionic acid, butyric acid exists in the anaerobic fermentation process.

Description of drawings

Fig. 1 is a graph showing the methane production of anaerobic digested sludge after adding magnetite provided by the embodiment of the present invention.

Fig. 2 is an analysis diagram of the current-voltage response of the anaerobic digested sludge provided by the embodiment of the present invention.

Fig. 3 is a performance diagram of methane production in paddy soil after adding magnetite provided by the embodiment of the present invention.

detailed description

The following examples are detailed descriptions of the present invention.

Example 1

Synthesize 10nm magnetite colloidal solution by co-precipitation method according to the prior art, and set it aside. Anaerobic digested sludge was selected as the inoculum, and the electron donor was a mixture of propionic acid and butyric acid (mass ratio, 1:1).

Add the above-mentioned magnetite with a final concentration of 2g/L, anaerobic digested sludge with a final concentration of 15g/L, propionic acid and butyric acid (each 5g/L) and 150mL medium to the high-purity nitrogen purging to remove anaerobic In the anaerobic reactor with the oxygen remaining in the bottle, it was anaerobically fermented under the sealed conditions of pH=7.0 and 37°C.

At the same time, no magnetite was added as a control group (see Figure 1).

As shown in Figure 1, the addition of magnetite led to a 90% increase in the methane production of the system compared with the non-addition of magnetite group, and a 1.9-fold increase in the methane generation rate, and the enriched mutualistic microbial flora had significant electrochemical activity (Figure 2) .

The medium recipe is:

NaH ₂ PO ₄ H ₂ O 1g/L, Na ₂ HPO ₄ H ₂ O 0.55g/L, NaHCO ₃ 3g/L, CaCl ₂ 275mg/L, NH ₄ Cl 310mg/L, MgCl ₂ 330mg/L, KCl 130mg/L L, MnSO ₄ 6H ₂ O5mg/L, FeSO ₄ 7H ₂ O10mg/L, CuSO ₄ 5H ₂ O0.1mg/L, CoCl ₂ 5H ₂ O1mg/L, NiSO ₄ 28-42mg/L, ZnCl ₂ 1 mg/L, H ₃ BO ₃ 0.1 mg/L, Na ₂ MoO ₄ 0.25 mg/L, NiCl ₂ .6H ₂ O 0.24 mg/L and EDTA 1 mg/L.

The properties of anaerobic digested sludge: pH, total solids (TS) and volatile suspended solids (VSS) were 6.94, 3.63±1.30g/L and 11.75±0.79g/L, respectively.

Example 2

Synthesize 10nm magnetite colloidal solution by co-precipitation method according to the prior art, and set it aside. Paddy soil was selected as the inoculum, and the electron donor was propionic acid.

Add the above-mentioned magnetite with a final concentration of 2g/L, paddy soil with a final concentration of 10g/L, propionic acid (5g/L) and medium (30mL) into the anaerobic bottle purged with high-purity nitrogen to remove residual oxygen In the anaerobic reactor, the anaerobic fermentation was carried out under the sealed conditions of pH=7.0 and 37°C.

At the same time, no magnetite was added as a control group (see Figure 3).

As shown in Figure 3, the addition of magnetite led to a 7-fold increase in methane production and a 12-fold increase in the methane generation rate compared to the group without magnetite addition.

Properties of paddy soil: pH6.3, organic matter 20.1g/kg.

Example 3

Synthesize a 30nm magnetite colloidal solution by co-precipitation method according to the prior art, and set it aside. Paddy soil was selected as the inoculum, and the electron donor was butyric acid.

Add the above-mentioned substances into the culture medium, and then transfer to the anaerobic reactor that purged with high-purity nitrogen to remove the residual oxygen in the anaerobic bottle. Add 8g of butyric acid and 3g of magnetic Iron Ore and 20g of Paddy Soil. Anaerobic fermentation was carried out in a reactor under sealed conditions of pH=7.0 and 37°C.

Claims (2)

1. utilize nano magnetite to improve a method for anaerobism product methane efficiency, it is characterized in that: withSCFA is as electron donor, and nano magnetite, as electron carrier, is cultivated bar at anaerobic fermentationUnder part, methane efficiency is produced in SCFA generation fast degradation and then raising system syntrophism oxidation;

Taking anaerobically digested sludge or rice soil as inoculum, SCFA are as electron donor and nano magneticIron ore adds in culture medium successively as electron carrier, under the condition of pH=7.0 and 30-37 DEG C,Anaerobic fermentation produces methane;

Described electron donor is propionic acid and/or butyric acid, and concentration is 1-10g/L;

Described magnetic iron ore final concentration is 1-4g/L, and diameter is 5-50nm;

Described inoculum final concentration is 10-20g/L.

2. by the method for utilizing nano magnetite to improve anaerobism to produce methane efficiency claimed in claim 1,It is characterized in that: described culture medium composition is: NaH₂PO₄·H₂O1g/L、Na₂HPO₄·H₂O0.55g/L、NaHCO₃3g/L、CaCl₂275mg/L、NH₄Cl310mg/L、MgCl₂330mg/L、KCl130mg/L、MnSO₄·6H₂O5mg/L、FeSO₄·7H₂O10mg/L、CuSO₄·5H₂O0.1mg/L、CoCl₂·5H₂O1mg/L、NiSO₄28-42mg/L、ZnCl₂1mg/L、H₃BO₃0.1mg/L、Na₂MoO₄0.25mg/L、NiCl₂.6H₂O0.24mg/L and EDTA1mg/L.