The Ventilation Mode of Steel Silos for Grain Storage

With the outstanding advantages of small space occupation, high strength, nice appearance, short construction period, and a high degree of automation, steel silos are favored by many grain processing enterprises and have been widely used in the field of grain processing, storage, and transshipment. Besides, its applications in the building materials industry, chemical industry, sewage treatment industry, etc., also maintain strong development momentum.

In the grain material storage, a significant development trend of steel silo is that the single silo capacity is getting larger and larger. This leads to its corresponding grain storage security requirements are increasingly high. There are various kinds of grain can be stored in steel grain silos, such as corn, soybean, rice, wheat, barley, malt, rapeseed, etc. Different grain has different application requirements, so their storage time in steel silos is different:

• Grain reserve steel silo for long term storage: storage time is more than 1 year.
• Transshipment steel silo at bulk grain port: storage time is 2 to 3 months.
• Steel silos in grain and oil processing plants: storage time is 1 to 2 months.

The storage time is directly related to the safety of grain storage. To ensure that the grain will not be moldy due to changes in temperature and humidity, a ventilation system should be set up in the steel grain silo. The ventilation method we commonly adopt is to equip a fan at the silo bottom to introduce the outside dry air into the silo ventilation trough or ventilation duct. After that, the diffused dry air will continuously exchange with the hot and humid air between grain piles. With the help of the axial flow fan (or the air vent on the silo roof), the hot and humid air inner the silo can be discharged in time to reduce the grain temperature and balance the humidity.
In addition to the ventilation rate and fan selection, ventilation mode is another important factor to determine the ventilation effect of a steel grain silo. Common ventilation modes include trough type, ground cage type, single pipe type, multi-pipe type, radial ventilation type, vertical ventilation type, etc. However, the steel grain silo can be divided into the flat bottomed silo and cone bottomed silo, and their ventilation modes have different characteristics. Next, we will talk about it in detail.

Ventilation Mode of Flat Bottom Steel Grain Silo

There are mainly two ventilation modes for flat bottomed steel grain silos. One is to set up the ventilation trough in the silo foundation and lay ventilation sieve plates on the trough. The other is to build a ground cage on the silo foundation. In addition, according to the diameter of steel grain silos, the ventilation mode can also be divided as follow.
Single Fan Mode
It is usually used for small size steel grain silos (diameter:φ<14m).
Features: simple ventilation duct circuit, small loss of air volume and discharge head, low requirements for foundation construction, easy installation of the ventilation duct, uneven distribution of air volume, etc.
Double Fan Mode
It is applied for middle size steel grain silos (diameter: 14m<φ<20m).
Features: large ventilation area, small loss of air volume and discharge head, uniform distribution of air volume, great difficulty in foundation construction and air duct installation, etc.
Four Fan Mode
It is used for large size steel grain silos (diameter:φ>20m).
Features: large ventilation area, symmetric distribution, uneven distribution of air volume, etc.
Full Bottom Ventilation Mode
This mode is to fully cover the silo bottom with ventilation sieve plates to realize the whole section ventilation of the silo bottom. It is commonly used for steel grain silos with a diameter less than 8m.
Generally speaking, the ventilation effect of flat bottomed steel grain silo is excellent, which can realize a large ventilation cross-section area to facilitate the uniform distribution of air volume. But its investment in civil engineering foundation and ventilation equipment is larger.

Ventilation Mode of Cone Bottom Steel Grain Silo

External Ring-type Ventilation Mode
This mode needs to open holes on the discharge cone and convey dry air to the grain piles through multiple ventilation pipes. It features simple installation, easy maintenance, small ventilation section, poor ventilation effect, and small investment. It is usually applied for small size steel grain silos (diameter:φ<8m).

Trough Mode
The trough ventilation mode features a small investment but an obvious ventilation effect.
Ground Cage Mode
The ground cage mode has high requirements for the silo foundation but it has a good ventilation effect. Its ground cage must be strength calculated to ensure sufficient bearing strength, which is difficult to manufacture and install.
In the actual selection of ventilation modes, we must consider a variety of factors, such as construction investment, grain material characteristics, discharge form of steel silo, grain material storage time, etc. Only in this way can we reduce the probability of problems in the process of grain storage and realize the safe storage of grain materials.