Does the kind-hearted person have an introduction to the digester? Show me!

Ordinary biogas digesters, also known as traditional or conventional biogas digesters, have a history of 100 years. Digester is usually a closed cylindrical tank. In order to make the feed fully contact with anaerobic sludge and the generated biogas bubbles can escape in time, there is always a stirring device. There are three types of blends:

Mechanical stirring in the tank

Biogas stirring

Circulating digestive juice stirring

1, mechanical stirring in the tank

Mixing and stirring is also one of the technological conditions that affect the efficiency of anaerobic digestion. In an anaerobic digester without stirring, the feed liquid in the digester is often layered. By stirring, the feed liquid in the tank can be fully mixed, which can increase the contact between feed and microorganisms, avoid stratification and promote biogas separation. In a continuous feed digester, stirring can also promote the rapid mixing of feed with the original liquid phase in the digester. Stirring can significantly improve the digestion efficiency, so in the traditional anaerobic digestion process, the digester with stirring is also called high efficiency digester.

2, biogas stirring

In order to make the feed fully contact with the anaerobic sludge and the generated biogas bubbles can escape in time, the biogas is pumped out from the top of the tank by the compressor and then pumped in from the bottom of the tank to make the biogas circulate. Mechanical stirring digester is a mechanical stirring device installed in digester, which is driven by motor and other equipment to stir.

Grille grit chamber sedimentation tank digestion tank sludge dewatering contact tank

3. Stir the circulating digestive juice

In order to make the feed fully contact with anaerobic sludge, the generated biogas bubbles can escape in time. There is a jet in the tank, and the circulating digestive juice pumped by the water pump outside the tank is sprayed out through the jet, forming a vacuum in the throat and sucking part of the digestive juice in the tank to form strong stirring.

Second, the operation mode of digester

Gastrointestinal digestion

Secondary digestion (multistage digestion)

Anaerobic contact digestion

1, primary digestion

Primary digestion is general digestion, which usually involves connecting several identical digesters in parallel, and each digester completes all the digestion processes independently.

2. Secondary digestion

Because the decomposition degree of organic matter is 45% ~ 55% when sludge is digested at medium temperature, the digested sludge is not stable enough. When discharged into the drying field or mechanically dehydrated, the organic matter will continue to decompose, resulting in methane escaping into the atmosphere, which not only pollutes the atmosphere, but also loses heat. In addition, the moisture content of cooked sludge will be higher than that of fresh sludge, thus increasing the load of drying field or dewatering machinery and equipment. In order to solve the above problems, the digestion process can be divided into two parts, that is, the sludge is digested to a certain extent in the first digestion tank, and then transferred to the second digestion tank, and the organic matter is further decomposed by using the waste heat. This operation is called secondary digestion. .

3. Anaerobic contact digestion

The anaerobic contact digestion process of sludge and organic sewage is shown in the following figure. Fresh sludge is continuously sent to the digestion tank through the balance tank, and the digested sludge is discharged from the bottom of the digestion tank, enters the sedimentation tank through the degasser, and the supernatant of the sedimentation tank is discharged. Part of the concentrated sludge is pumped back to the digester for stirring, and the rest is discharged as surplus sludge. The return flow is 1 ~ 3 times of the sludge volume. With this operation mode, due to the increase of methanogens in the biogas digester, the decomposition speed of organic matter is accelerated and the digestion time can be greatly shortened.