Biogas is a mixed gas composed of multiple gases. It contains methane, carbon dioxide, hydrogen sulfide, carbon monoxide, hydrogen, oxygen, nitrogen and other gases. Among them, there is much methane, accounting for 50% to 70% of the total volume, carbon dioxide accounting for 25% to 40%, and a few other gases, which generally add up to only about 2% of the total volume. Biogas can be burned mainly by methane. Methane is colorless and odorless. It is mixed with a certain amount of air and can be burnt when it is ignited, emitting a blue flame and a lot of heat. Sometimes you will smell the smell of rotten eggs, which is a unique smell of hydrogen sulfide. After ignition, this smell disappears.
How is biogas produced
Organic matter (such as human and livestock manure, crop straw) under certain moisture, temperature and anaerobic conditions, through the catabolism of various microorganisms, produces mixed gases such as methane and carbon dioxide (biogas).
Basic conditions for artificial biogas production by biogas generators
①Strict anaerobic environment (biogas digester)
②Sufficient fermentation materials
③Abundant biogas bacteria
④ Proper fermentation concentration
⑤ Proper pH (PH value)
⑥Proper temperature. One of these conditions is not suitable for biogas bacteria, and cannot produce biogas.
What are the parts of the biogas digester?
Generally, the hydraulic biogas digester is composed of the feed inlet, the discharge (water pressure) room, the gas storage room, the fermentation room, the movable cover, and the air duct.
What is the “three-in-one” biogas digester
It is to build the biogas digester together with the pig pen and the toilet and connect with each other, so that human and animal manure can automatically flow into the biogas digester at any time, so as to achieve the purpose of frequent feed and labor saving. This method of building a pond can not only ensure the continuous replenishment of new fermentation raw materials into the biogas digester, and ensure a balanced gas production, but also help improve the environmental sanitation in the countryside and kill mosquitoes and flies.
What is biogas fermentation
Biogas fermentation, also known as anaerobic digestion and anaerobic fermentation, refers to the process of organic matter under certain moisture, temperature and anaerobic conditions, through the catabolism of various types of biogas fermentation microorganisms to generate mixed gases such as methane and carbon dioxide (biogas) .
What are the commonly used biogas fermentation raw materials in rural areas
There are many sources of biogas fermentation in rural areas. The most commonly used are manure of humans, livestock and poultry (pigs, cattle, sheep, chickens, ducks, geese, etc.), various crop stalks (straw, wheat straw, corn stalks), and green weeds. , Rotten leaf grass, water hyacinth, organic waste residue and waste water (waste water from wine, tofu, slaughterhouse waste water), etc., are all good raw materials for biogas fermentation.
Which fermentation raw materials to choose to make the biogas digester produce fast and good gas?
Biogas fermentation raw materials are the material basis for the production of biogas. During biogas fermentation, various microorganisms absorb water, carbon sources, nitrogen sources, inorganic salts and certain mineral elements from the fermentation raw materials.
In order to ensure that there are sufficient and stable fermentation raw materials for the start-up and fermentation of the biogas generator, it is necessary to select cow dung, pig dung, and sheep dung with suitable organic nutrition as the start-up fermentation raw materials before feeding. Because these manure raw materials have finer particles, contain more low-molecular compounds, and have high nitrogen content, their carbon-to-nitrogen ratios are less than 25:1, which are all within the carbon-nitrogen range suitable for fermentation. Therefore, the above manure is selected as the fermentation raw material for fast start-up and good gas production. Don’t start with chicken manure, human manure and sweet potato residue alone, because these kinds of raw materials are easy to acidify when there are few biogas bacteria, so that fermentation can not proceed normally.
How to start a newly fed biogas digester
The process of the newly fed biogas generator and biogas digester from the start of the feed to the normal and stable natural gas production is called the start of biogas fermentation. The smooth start-up of the digester fermentation is very important for maintaining long-term stable operation. The startup procedure is generally:
1. Proportion of fermentation raw materials as required.
2. Add water above 20C.
3. Use pH test paper to measure the pH before closing the movable cover.
4. Close the movable cover.
5. Vent and test the fire.
What problems should be paid attention to when starting a biogas digester
When starting a biogas digester that does not leak water and gas, the following issues should be paid attention to:
①There must be sufficient inoculum. Before loading the new tank, collect the biogas residue and liquid from the old biogas tank, the black sludge from the bottom of the manure pit, pond mud, sewage sludge from urban sewage ditches, and sewage and sludge from food factories, wineries, and slaughterhouses. , Which are rich in biogas bacteria, are good inoculants. The quantity of one of the above inoculums should be 10%-30% of the fermentation raw materials. Mix the inoculum and fermentation raw materials uniformly, add them to the tank together, and add water to seal the tank in time. The water added to the biogas digester can be selected from biogas fermentation liquid, domestic wastewater, river water or pond water, etc., and well water can also be used, but tap water is not used as much as possible. Industrial wastewater containing toxic substances cannot be used.
② Suitable temperature. In the range of 10-60C, the biogas generator and biogas digester can normally ferment and produce gas. In this temperature range, the higher the temperature, the higher the gas production. Therefore, the start-up of the biogas digester will take place from April to October.
③Proper pH (pH value). The growth and reproduction of biogas microorganisms require the pH of the fermentation raw materials to be neutral or slightly alkaline (ie, pH 6.5-7.5). Over-acid and over-alkali will affect gas production.
④ Appropriate load. The load of rural biogas digesters is usually expressed by the concentration of fermentation raw materials, and the suitable dry matter concentration is 6%-12%. If the concentration is too high, the fermentation raw materials are not easy to decompose, and it is easy to accumulate a large amount of acidic substances, which affects the normal gas production. If the concentration is too low, the organic content per unit volume is relatively reduced. The biogas digester should be started at a low load (concentration below 6%). After the gas production is normal, the load will be gradually increased until the designed operating load is determined.
⑤ Control of adding water. When the biogas generator and biogas digester are started, the amount of water added to the digester is relatively large, accounting for about 5/8 of the effective volume of biogas. Therefore, the start-up water temperature has a great influence on the smooth start-up of the biogas digester. Generally, the starting water temperature should be controlled above 20C. If the biogas digester is started in autumn and winter, the temperature of the starting water added to the tank should generally be controlled above 35C.
⑥Cover. Lime mortar is used to seal the movable cover, which should not be too hard or too soft, and should be able to fill the gap between the movable cover and the skylight. The water storage ring on the movable cover should be filled with water frequently to prevent the sealing glue from drying out and leaking.
Post time: Sep-01-2021