Role of PA and SA Fans In the Manufacturing Combustion Process

Industrial process fans are essential in the manufacturing process of many industries. We hardly find any sector where usage of these process fans isn’t there in some way or the other. Industrial process fans, also called blowers, perform many important tasks in factories/ plants such as conveying/handling of materials, combustion air, the elimination of noxious pollutants and removal of moisture / drying.

In fact, in quite a few plants like the ones that involve the generation of thermal power, the presence of the blowers attains much more importance. For, they make sure that the process of combustion gets completed most appropriately. And, combustion is a highly significant aspect of these facilities. Let us now go into more detail.

• When combustion of fuel is considered, the PA (primary air) fans as well as the SA (secondary air) fans are of almost equal importance. It is only when both these blowers are there that the process progresses devoid of hassles.
• In plants/ factories where combustion is a key process, the significance of PA fans can never be overstated. These fans bring in an airflow having a very high pressure, which thrusts the crushed coal particles toward the furnace, by creating a positive pressure. It is only after that that proper combustion takes place. Centrifugal fans that are curved in a backward direction are the variants generally used as the primary air fans.
• In the same way, we have the SA fans, which are crucial in units where combustion is among the most paramount of all processes, too. The main job of secondary air fans is to play a supportive role for the PA blowers. There are some situations where the airflow coming from the PA fans isn’t sufficient for combustion.

It’s in these instances that the SA fans come to the rescue; they lose no time in supplying the added airflow to the system. Following that, there won’t be any further issues in the process of combustion. The relevance of the SA fans is also attributable to the fact that they make sure that fuel doesn’t get wasted.

ID fans and FD fans in the combustion process
The ID (induced draft) fans and FD (forced draft fans) are the types that are generally installed as primary/ secondary air fans in these facilities. Which of those is the primary blower, and which is the secondary varies from one unit to another. This is primarily dependent on the nature of processes.

• The outlet that is exactly in the middle of the chimney and dust collector is the location where the ID fans are fixed. It is from this spot that these blowers collect the flue gasses having extreme heat and expel them into the outside environment, through the chimney. The fans carry out this by creating negative pressure.
• Since the ID fans are continuously exposed to flue gasses, these blowers tend to develop issues related to corrosion quite often.
• The forced draft blowers are present near the boiler’s inlet. From there, the FD fans take in the air from outside and push it with high pressure into the chamber where combustion happens.
• The cost of maintaining forced draft fans is much less than their ID counterparts.
• Despite the differences in ID and FD fans, both these kinds of blowers ensure that power consumption is always on the lower side. This leads to a lot of cost savings, in the long- run.