CN101381072A - Hydrogen production method by sweet sorghum stalk anaerobic fermentation - Google Patents

Abstract

The invention relates to a method for producing hydrogen with sweet sorghum straws through anaerobic fermentation, which belongs to the technical field of renewable energy source utilization. The method comprises the processes such as selecting raw materials, preprocessing the materials by dilute alkali solution, fermentation and so on; and the concrete steps include: a. air-dried sweet sorghum straws are selected as raw materials and crushed; b. the crushed sweet sorghum straws are hydrolyzed in a NaOH solution with a concentration of 0.5 percent for eight hours, the hydrolysis temperature in a thermostatic bath is controlled to be 60 DEG C, and the hydrolyzate and residues are all taken as substrates; c. the sweet sorghum straws preprocessed by the dilute alkali solution are put into a fermentation vessel, meanwhile, anaerobic activated sludge bacteria source which is aerated at room temperature and mixed for two hours is put into the fermentation vessel, and the hydrogen is prepared through natural fermentation at the temperature of between 35 and 37 DEG C; and d. the dosage ratio is as follows: 20 g of raw materials and 250 ml of bacterial strains which are replenished with water to 1L. In order to start preparing the hydrogen quickly, the fermentative liquid can be added with a little lactic acid, so that the initial pH value of the liquid is between 5.3 and 5.7. The hydrogen production rate is 124.23 ml/g.TVS, and the utilization rate of the main components, namely cellulose, hemicellulose, and sugar is 45.86 percent, 64.75 percent and 99.17 percent respectively. Compared with the prior art, the method has the advantages of high utilization rate of the raw materials and high hydrogen production rate, simple and convenient method and so on.

Description

A kind of method with the hydrogen manufacturing of sweet sorghum stalk anaerobically fermenting

Technical field:

The present invention relates to a kind of method, belong to the renewable energy utilization technical field with the hydrogen manufacturing of sweet sorghum stalk anaerobically fermenting.

Background technology:

Energy scarcity and environmental pollution are just seriously restricting human Sustainable development, and the exploitation of new forms of energy is imperative.Hydrogen Energy (H ₂) being the clean energy of high heating value: every gram hydrogen burning will discharge the heat of 122kJ, and only generate water after the burning, can realize " zero release " of polluting.2005, the hydrogen energy source that the whole world is used for trade reached 5,000 ten thousand tons, and estimation will be risen with nearly 10% annual growth; Hydrogen will become one of important substitute energy of fossil oil.With pyrolysis method, ordinary methods such as water electrolysis method hydrogen manufacturing are compared, and microbial fermentation hydrogen manufacturing has cleaning, advantage such as energy-conservation.

At present, microbial fermentation hydrogen manufacturing mainly rests on laboratory stage, and major cause is to be that the product hydrogen rate of ferment for hydrogen production of substrate is also lower with cheap raw material (as agricultural wastes straw).Cellulose series biomass is the profuse renewable resources of occurring in nature.The annual production of Crop in China stalk surpasses 6.2 hundred million tons, is trapped in the environment but these biomass resources are most for a long time as waste; It is effectively utilized the effective way that becomes alleviating energy crisis and environmental pollution.The agricultural crop straw kind is a lot, and the present technique patent is chosen sweet sorghum stalk as the ferment for hydrogen production raw material.Although sugar degree is more in the sweet sorghum stalk, spontaneous fermentation state product hydrogen rate down is not high, and coarse-fibred utilization ratio is lower.Though people such as Claassen with the enzymic hydrolysis of sweet sorghum stalk slag after, be that inoculum carries out ferment for hydrogen production with the thermophile bacteria, produce the hydrogen rate and reach more than the 200ml/gTVS; But, add the cost height of cellulase and thermophilic fermentation system, only limit to laboratory study so far, also widespread use aborning.Thereby, seek more economical pretreatment technology easily, become the important step that realizes stalk raw materials ferment for hydrogen production suitability for industrialized production.Temperature used dilute alkaline soln to handle sweet sorghum stalk down during patent of the present invention was chiefly directed to, and made the fermentation and hydrogen production rate that raising by a relatively large margin arranged.

By literature search, do not see the open report identical with the present invention.

Summary of the invention:

The objective of the invention is to improvements over the prior art, it is the method for the anaerobically fermenting hydrogen manufacturing of raw material with the sweet sorghum stalk with what produce that the hydrogen rate is higher, method is easy that a kind of raw material availability is provided.

The present invention is a raw material with the sweet sorghum stalk that gathers in the back natural air drying, with dilute alkaline soln sweet sorghum stalk is carried out pre-treatment, be the bacterium source with anaerobic activated sludge again, medium temperature condition bottom fermentation hydrogen manufacturing at 36 ± 1 ℃, producing the hydrogen rate is 124.23ml/gTVS, the utilization ratio of main component Mierocrystalline cellulose, hemicellulose, sugar reaches 45.86%, 64.75%, 99.17% respectively in the stalk.

The inventive method comprises material choice, raw material is carried out operations such as pre-treatment, fermentation with dilute alkaline soln; Concrete steps are:

A. raw material is the sweet sorghum stalk behind harvesting, the natural air drying, before the fermentation it is pulverized;

B. it is 0.5% NaOH solution hydrolysis 8 hours that the sweet sorghum stalk after will pulverizing is put into concentration, and controlling the thermostatic bath hydrolysis temperature therebetween is 60 ℃;

C. will put into fermenting container through the pretreated sweet sorghum stalk of dilute alkaline soln (hydrolyzed solution and residue), and add aeration at room temperature simultaneously and stir anaerobic activated sludge (bacterial classification) after 2 hours, be spontaneous fermentation hydrogen manufacturing under 36 ± 1 ℃ of conditions at temperature control.

D. usage ratio is raw material 20g, bacterial classification 250ml, and moisturizing is to 1L; For guaranteeing to produce the quick startup of hydrogen, can in fermented feed liquid, add a small amount of lactic acid, the initial pH value that makes feed liquid is 5.5 ± 0.2.

The present invention compared with prior art has raw material availability and produces advantages such as the hydrogen rate is higher, method is easy.

Description of drawings:

Fig. 1 is a process flow diagram of the present invention.Among the figure: 1-fermentation flask (jar), 2-thermostatic bath, 3-thief hole, 4-air collector, 5-recorder jar, 6-scale marks.

Fig. 2 is each fermentation group pH value change curve in the fermenting process.

Fig. 3 is each fermentation group cumulative gas production change curve in the fermenting process.

Fig. 4 is liquid product content graphic representation in the fermentation group 1.

Fig. 5 is liquid product content graphic representation in the fermentation group 2.

Embodiment:

Below in conjunction with accompanying drawing the present invention is described specifically.

Described in the concrete steps such as summary of the invention of present embodiment, use volume as the Erlenmeyer flask of 1L or three-necked bottle as fermentation flask, the wide-necked bottle that with volume is 1L is as air collector, recorder jar, carry out batch ferment for hydrogen production (fermentation flask, air collector, recorder jar and raw material consumption all can enlarge by corresponding proportion, as 5L device, 100 gram raw materials); Adopt conventional drainage to collect the gas that produces.

1, raw material and pre-treatment

If fermentation group 1 is the raw material group, the sweet sorghum stalk behind harvesting and the natural air drying is pulverized, directly add in the fermentation flask, sample introduction concentration is controlled to be 20g/L.If fermentation group 2 is the dilute alkaline soln pretreated group, the raw material after 20g pulverized are hydrolysis 8 hours in the 0.5% NaOH solution in 500ml concentration, and controlling the thermostatic bath hydrolysis temperature therebetween is 60 ℃, and hydrolyzed solution and residue are all as substrate.It is nutritive medium that each experimental group is not added any inorganic salt solution.Total solids level (TS) is calculated as follows with general volatile substances content (TVS, promptly organic):

$\mathrm{TS}=\frac{W_2}{W_1}\&times;100\%,$ ? $\mathrm{TVS}=\frac{W_2-W_3}{{\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="A200810233440E00061.png,A200810233440E00062.png"\; state="\{\{state\}\}">W</figure-callout>}}_2}\&times;100\%$

Annotate: W ₁Represent the total mass of certain material, W ₂The quality of material to the constant weight, W are dried in representative ₃Represent the quality of calcination material to the constant weight, promptly ash content is heavy.

2, inoculum

Fermentation and hydrogen production bacterial classification (being inoculum) comes the methane-generating pit anaerobic sludge of self energy normal gas producing.Before the fermentation, at room temperature with sludge aeration and stirred 2 hours, to suppress hydrogen-consuming bacteria group's (being the methanogen of strictly anaerobic) activity.

3, analytical procedure

Available gas chromatograph (GC) or formula gas analyzer difficult to understand are measured the gas (H that produces in the fermenting process ₂) composition and content, use composition and variation that gas chromatograph is analyzed liquid product (organic acid, alcohols etc.).Use PSH-25 type acidometer to measure the variation of the pH value in the fermentation period.Adopt the total sugar content in the sweet sorghum stalk after DNS method (3, the 5-dinitrosalicylic acid) is measured the dilute hydrochloric acid hydrolysis; Adopting volume fraction is that 20% nitric acid-80% alcohol mixed solution dissolution method is measured cellulosic content (lignin conversion is to be dissolved in the ethanol behind the nitration of lignin, remaining Mierocrystalline cellulose residue); Adopt the dilute sulphuric acid hydrolysis method to measure the content of hemicellulose in the stalk (hydrolysis is 1 hour under 100 ℃, in 2% the dilution heat of sulfuric acid).The utilization ratio of each component in the raw material in the fermenting process (Utilized rate UR) is calculated as follows:

$\mathrm{UR}=\frac{W_a-W_b}{W_a}\&times;100\%,$

Annotate: W _aCertain components contents in the raw material before the expression fermentation, W _bCertain components contents after the expression fermentation period finishes.

4, experimental result

A. the pre-treatment of substrate is to producing the influence of hydrogen rate and hydrogen output

See that from Fig. 3 the pre-treatment of raw material has a significant effect to whole fermentation and hydrogen production process.Soluble sugar (mainly referring to simple carbohydrates such as monose, disaccharides) is the optimal nutritive substance of microorganism, for sweet sorghum stalk or other stalk, they contain compositions such as a large amount of Mierocrystalline celluloses, hemicellulose, these materials are to be difficult to be decomposed utilization by Institute of Micro-biology under state of nature, and this is to produce the lower major cause of hydrogen rate when causing raw material fermentation.In fermentation group 2, because of raw material had passed through the dilute alkaline soln pre-treatment before fermentation, promote material parts such as Mierocrystalline cellulose, hemicellulose or most of be hydrolyzed to simple carbohydrate, the content of soluble sugar improves in the hydrolyzed solution, helping the hydrogenogens group utilizes, thereby the aerogenesis cycle stretch-out is 2.16 times of raw material group, and product hydrogen rate and hydrogen output all rise to 2.55 times of fermentation group 1.

Each experimental group aerogenesis status list of table 1

Group	Total gas production	Hydrogen content	Total hydrogen output	Produce the hydrogen rate
					1	1520ml	52.4％	796ml	48.79ml/g·TVS
2	3890ml	52.1％	2027ml	124.23ml/g·TVS

Annotate: the mean value of the hydrogen content of listing in the table 1 for drawing after each group analysis does not detect the methane generation of high level in the experiment.

B. the composition of liquid product and variation

Be accompanied by the generation of VFA and alcohols in the ferment for hydrogen production process.Know that from Fig. 4,5 main liquid product is ethanol, propionic acid and butyric acid in the feed liquid.In fermentation group 1, ethanol, propionic acid, butyro-high-content are respectively 830mg/L, 890mg/L, 1050mg/L.In the fermentation group 2, owing to contain soluble saccharide after a large amount of hydrolysis in the feed liquid, be converted into ethanol and the organic acid amount is more, wherein, the high-content of alcoholic acid reaches 1680mg/L.For fermentation group 2, ethanol is the maximum liquid product of content, illustrates that reaction process is to carry out according to ideal ethanol-type fermentation comparatively, also proves that sweet sorghum stalk is to produce the alcoholic acid desirable feedstock simultaneously.

C. the raising of the utilization ratio of main component in the raw material

The main component of table 2 sweet sorghum stalk and utilization ratio

Annotate: other organic matter comprises xylogen, crude protein, crude fat etc. ,-be illustrated in and detect.

The utilization ratio difference of finding out lignocellulose and sugar in the table 2 is very big.In the raw material fermentation, sugar is easy to be utilized, and transformation efficiency is near 90%; But hemicellulose and Mierocrystalline cellulose are difficult to be degraded under the spontaneous fermentation state, and utilization ratio only is respectively 15.32%, 13.89%.Because the total amount of carbohydrate surpasses 70% in the sweet sorghum stalk, the raw material after the dilute alkaline soln hydrolysis, hemicellulose and cellulosic utilization ratio rise to 64.75% and 45.86%, are respectively 4.2 times and 3.3 times of raw material fermentation.Therefore, the dilute alkaline soln hydrolysis treatment has more significantly help to the utilization ratio that improves stalk raw materials in the fermenting process with product hydrogen rate.

Claims (1)

1, a kind of method with the hydrogen manufacturing of sweet sorghum stalk anaerobically fermenting comprises material choice, fermentation procedure, it is characterized in that present method also comprises with dilute alkaline soln raw material is carried out pretreatment process; The concrete steps of present method are:

A. the sweet sorghum stalk of material choice after air-dry pulverized;

B. it is 0.5% NaOH solution hydrolysis 8 hours that the sweet sorghum stalk after will pulverizing is put into concentration, and controlling the thermostatic bath hydrolysis temperature therebetween is 60 ℃, and hydrolyzed solution and residue are all as substrate;

C. will put into fermenting container through the pretreated sweet sorghum stalk of dilute alkaline soln, and add aeration at room temperature simultaneously and stir 2 hours anaerobic activated sludge bacterium source, be the hydrogen manufacturing of 36 ± 1 ℃ of condition bottom fermentations in temperature.

D. throwing amount ratio is raw material 20g, bacterial classification 250ml, and moisturizing is to 1L; For guaranteeing to produce the quick startup of hydrogen, can in fermented feed liquid, add a small amount of lactic acid, the initial pH value that makes feed liquid is 5.5 ± 0.2.

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