How to choose the appropriate negative pressure conveying system method
Negative pressure conveying systemIt provides an environmentally friendly and hygienic conveying method for powders that are prone to flying, and can achieve conveying distances that mechanical conveying systems cannot reach. However, using the wrong pneumatic conveying method to transport mixed powders may result in uniformity issues. These issues may render efforts in vain, resulting in the scrapping of powder materials, downtime, and loss of brand standards and reputation. This article will discuss two main types of pneumatic conveying systems: dense phase pneumatic conveying and dilute phase pneumatic conveying, and emphasize that the dense phase is the best choice for conveying mixed powders.
The working principle is to generate airflow (usually air) in the pipeline and create a pressure difference between the feeding point and the receiving point, causing the powder material to move from the high pressure point to the low pressure point.
In the dilute phase powder conveying system, the powder material is fed into a continuous airflow generated by a blower at the front (pressure) or back (vacuum) of the process. In this airflow, the air velocity can generally reach 15-35 meters per second. Dilute phase pneumatic conveying is an excellent way to transport solid powders, but it cannot be used to transport fragile powders or mixed powders. When the airflow speed is too fast, fragile powder materials will be greatly crushed due to internal and pipeline collisions, and mixed powder materials will be separated in the pipeline due to differences in particle size, shape, and density, losing the mixing effect.
The dense phase powder conveying system is conveyed through a plug type pressure differential formed by airflow and material, with a typical conveying speed of 0.5-12.5 meters per second. The lower conveying speed and higher powder concentration prevent the decomposition of fragile powders or the separation of mixed powders. The dense phase pneumatic conveying system almost meets any production requirements. The purpose of this system is to slowly transport powder materials without causing blockages, and to supply production calculations. According to production requirements, a dense phase pneumatic conveying system can be set up to operate as an intermittent or continuous conveying system, and can achieve a rate of 20 tons/hour.
The dense phase powder conveying system can be further subdivided into a positive pressure pneumatic conveying system that uses compressed air to pressurize the transport container to push the powder, or a negative pressure pneumatic conveying system that uses a vacuum pump to evacuate the receiving container and pull the powder. The conveying distance of the positive pressure dense phase pneumatic conveying system can reach 100 meters, and the conveying height is 23 meters; The conveying distance of the negative pressure dense phase pneumatic conveying system can reach 50 meters, and the conveying height is 18 meters.
When production requirements exceed the limits of the dense phase powder conveying system, semi dense phase conveying is a good choice. By adding a little air, the powder material can move faster, increasing the total distance (horizontal and vertical) without excessively affecting the integrity or uniformity of the powder material.
When developing an automatic powder batching system, not only should efforts be made in the design of the batching and mixing process, but also in the material conveying process after mixing. Incorrect powder conveying methods may result in the failure of the batching and mixing work.
Word tag: Negative pressure conveying system