Pneumatic Conveying System
Pneumatic conveying system is introduced
Pneumatic conveying is also called air transportation, it is under certain conditions, the use of air flow as the medium, in the pipeline transport powder, granular solid materials to lose Send method. System is mainly composed of sending equipment, pipelines, gas separation equipment, gas source and purification equipment and electrical instrument, etc. Material in the pipeline Flow state is very complex, as the air velocity and air contained in the material and the material itself on the difference of the material such as significant changes.
Pneumatic conveying system is compared with the traditional transportation mode
|Compare items||Pneumatic conveying||Air slot||Pipe chain conveying||Tape||Chain type||Spiral||Bucket type||Vibrate|
|Particle size of the conveyed material/mm||<50||-||<||No special restrictions||<50||<30||<100||<30|
|Highest temperature of the transported material/℃||300||80||200||Ordinary tape||300||300||80||80|
|Slug sub pipeline inclination angle/（°）||Arbitrarily||Downward4~10||0~40||0~90||0~90||90||90|
|Maximum conveying capacity/t.h||50~200||300||50||3000||300||300||600||10|
|Maximum conveying distance/m||1000||200||100||8000||200||10||50||10|
|Required power consumption||General||Small||More||Small||Big||Medium||Small||Big|
|Maximum conveying speed/m.St||0.10~35||30~120||1~30/min||15~180m/min||10~30||20~100r/min||20~40||-|
|Conveying materials flying||Nil||Nil||Nil||Be likely to||Nil||Nil||Nil||Be likely to|
|Foreign objects mixed in and stained||Nil||Nil||Have||Be likely to||Nil||Nil||Nil||Nil|
|Conveying material residue||Very few||Very few||Have||Have||Have||Small amount||Have||Have|
|Flexibility of pipeline configuration||Free||Straight line||Difficult||Straight line||Straight line||Straight line||Straight line||Straight line|
|Possibility of diversion||Easily||Possible||Cannot||Possible||Difficulty||Cannot||Cannot||Difficulty|
|Section occupies space||Small||Medium||Big||Big||Big||Medium||Big||Big|
|Main maintenance parts||Elbows, Valves||-||Pipes, Chains, Blades||Idler, Bearing||Chain, Bearing||Comprehensive||Chain, Bearing||Comprehensive|
In summary, pneumatic conveying has the following features:
1) The transportation pipeline can be flexibly arranged to ensure reasonable process configuration of factory equipment;
2) Realize bulk material transportation with high efficiency and reduce packaging and loading and unloading transportation costs;
3) The system is sealed, with less dust flying and escaping, and good environmental hygiene conditions;
4) Less moving parts, convenient maintenance and easy automation;
5) It can avoid moisture, dirt, or other impurities from entering the material, ensuring the quality of the conveyed material;
6) During the transportation process, various process operations can be achieved, such as mixing, crushing, grading, drying, cooling, metering, dust removal, etc;
7) It can be remotely operated by sending data points to one location or by dispersing data points to another location;
8) For materials with unstable chemical properties. Inert gas transportation can be used.
Although to some extent, compared to other forms of transportation, the power consumption may be slightly higher, due to the high conveying wind speed, local pipeline wear and a small amount of crushing of the transported materials may occur. However, the shortcomings mentioned above can be significantly improved by using appropriate conveying methods such as low conveying wind speed and high mixing ratio.
Classification of pneumatic conveying status
According to the pneumatic conveying state, during the gas-solid two-phase flow, the movement state of the material will change with the change of conveying wind speed and air volume. When the wind speed of the material is high, the material is in a suspended state and is transported by the airflow in a uniform distribution; As the conveying wind speed decreases, the materials begin to aggregate; Afterwards, some materials gather in the pipeline and are transported in a group pulse dynamic manner; Continue to reduce the conveying wind speed, causing the material to block the cross-section and form unstable material plugs. At this time, the material plugs are pushed by the pressure of the air; Reduce the conveying wind speed again, and the unstable material plug will become a stable material plug, driven by the pressure of air for conveying.
It can be considered that the boundary between the uniform distribution of materials in vertical pipes and the boundary between the flight and transportation of materials in horizontal pipes is the boundary between the dilute phase and the dense phase. Therefore, the economic velocity line can be regarded as the boundary between the dilute phase and the dense phase.
Therefore, in summary, the entire pneumatic conveying system can be divided into two categories:
A. Dilute phase pneumatic conveying, with high airflow velocity, the material is suspended in a vertical pipe and evenly distributed, while in horizontal conveying, it is in a flying state with a large void ratio. The transportation of materials mainly relies on the energy held by the higher speed airflow.
B. Dense phase plug flow pneumatic conveying, the material is no longer uniformly distributed in the pipeline, but instead Dense state, but the pipeline well is not blocked by materials. Therefore, it is still held by the airflow Energy is transported. Devices designed for this type of flow state include high-pressure compression and fluidized conveying Etc.
The conveying mechanism and application practice of pneumatic conveying indicate that it has the advantages of a series of Point: Low carbon, environmentally friendly, high conveying efficiency, overall flexible equipment structure, maintenance management Convenient, easy to achieve automation and beneficial for environmental protection. Especially for factory workshops When transporting internally, the transportation process can be combined with the production process, which helps to simplify Equipment for the process. To achieve this, labor productivity can be greatly improved, costs can be reduced, and Reduce space occupation.
1.1 Dilute phase transportation (low pressure system)
Dilute phase transportation is the use of gas pressure below 1kg/c2, using positive pressure (pressure delivery) or negative pressure (suction) or a combination of positive and negative pressure, and pushing or pulling materials through the entire transportation line at a relatively high speed. Therefore, this transportation method is called a low-pressure high-speed system, which has a high gas to material ratio.
At the beginning of the system, there is an acceleration of about 10m/s2, and at the end, it can reach a high speed of around 1300m/min, resulting in a higher airflow speed. The initial pressure of the conveying pipeline is generally lower than 1kg/c2, while the end pressure is basically close to atmospheric pressure. The power for dilute phase transportation is generally air or ammonia, and the power is generally provided by centrifugal fan or Roots vacuum pump. When in the dilute phase, the material is suspended in the pipeline, and the conveying distance can reach several hundred meters.
The characteristic of dilute phase negative pressure conveying is that it can transport materials from one point or multiple points in bulk to a higher point.
The characteristic of dilute phase positive pressure conveying is that it can transport materials from a low point to multiple points.
Positive pressure and negative pressure can also be combined to meet special requirements, making it more suitable for multi-point feeding and multi-point discharge conveying methods to meet complex production process requirements.
Negative pressure dilute phase multi-point feeding and single point feeding
Positive pressure dilute phase single point feeding and multi-point feeding
1.2 Dense phase transportation (high-pressure system):
Dense phase transportation, also known as tank or bin pump transportation, utilizes a gas pressure higher than 1kg/c2 and uses positive pressure to push materials through the transportation pipeline. Therefore, it is often referred to as a high-pressure low-speed system. The material to gas ratio of this system is very high. The initial speed of this system is about 2m/min, and the starting speed is about 20m/s at the end (except for the full load conveying method). The pressure of the conveying pipeline is generally 2-3kg/c, and the pressure at the end of the system is almost zero. The system uses an air compressor as the power source, and its notable feature is low conveying speed, which has little impact on material quality.
At present, the use of high-pressure dense phase systems is very extensive, and different conveying methods can be selected for different conveying materials in order to maximize their performance and efficiency, and reflect their economy.
There are two ways of conveying in the sending tank: positive pressure honey phase conveying in the sending tank (tank pump), and a combination of full load conveying in the sending tank. Each type of material used by users has a certain degree of specificity and specificity. Our different conveying systems also have different operational performance and usage characteristics. Based on different requirements, we provide the best operating plan and integrated system that meets the production process and material requirements of users, ensuring that users' materials can achieve the best conveying requirements and improve production efficiency.
Positive pressure dense phase conveying of sending tank
Delivery tank combination full load transportation