How does the boiler dust collector work?

Boiler dust collector is a key equipment used to treat the large amount of dusty flue gas generated during boiler combustion process. Its main function is to separate the dust particles in the flue gas, so that the discharged flue gas meets environmental standards. Here are its common ways of working:

1、 Mechanical dust removal

1. Cyclone dust removal

-When the boiler flue gas enters the cyclone dust collector, its working principle is mainly based on centrifugal force. The flue gas forms a high-speed rotating airflow inside the dust collector. Due to the different masses of dust particles and gas molecules, heavier dust particles experience greater centrifugal force during the rotation process. These dust particles are thrown towards the wall of the dust collector and then fall into the ash hopper along the wall under the action of gravity. Smaller gas molecules, on the other hand, continue to move along the direction of the airflow in the central area of the cyclone, thus achieving preliminary separation of dust and gas.

-The cyclone dust collector has a simple and compact structure, and has good separation effect on larger dust particles (generally larger than 10 microns). Its processing efficiency is affected by factors such as the inlet flue gas velocity, the diameter and height of the dust collector. For example, increasing the inlet flue gas velocity appropriately can enhance centrifugal force and improve dust removal efficiency, but excessively high velocity may lead to secondary dust and affect the dust removal effect.

2. Inertial dust removal

-Inertial dust collector utilizes the inertia of dust particles. Inside the dust collector, the flow direction of the flue gas will suddenly change, while the dust particles will continue to move in their original direction due to inertia, thus separating from the gas. For example, in a louvered inertial dust collector, when smoke passes through the louvers, the direction of the airflow constantly changes, and dust particles collide with the blades of the louvers and then fall under the action of gravity.

-The dust removal efficiency of inertial dust collectors is relatively low, and they are generally used as pre dust removal equipment in combination with other effective dust removal equipment. They have a certain removal effect on larger coarse particle dust (greater than 20-30 microns).

2、 Filter and dust removal

1. Bag dust removal

-After entering the bag filter, the boiler flue gas is filtered through the filter bag. Filter bags are usually made of high-temperature and corrosion-resistant fiber materials, such as polyester fibers, glass fibers, etc. When smoke passes through the filter bag, dust particles are intercepted on the outer surface of the filter bag, while clean gas enters the interior of the filter bag through its pores and is then discharged from the air outlet.

-As dust accumulates on the surface of the filter bag, the resistance of the filter bag will gradually increase. When the resistance reaches a certain level, dust cleaning operation is required. The main methods of dust cleaning include pulse jet cleaning and mechanical vibration cleaning. Pulse jet cleaning is achieved by injecting compressed air into the filter bag, causing it to instantly expand and the dust to detach from the surface of the filter bag under the action of inertia. Mechanical vibration cleaning is achieved by using a mechanical device to vibrate the filter bag and shake off dust. Bag filter has high filtration efficiency for small particle dust (particle size can be as small as 0.1 microns), which can effectively remove fine particles from boiler flue gas.

3、 Electrostatic precipitator

1. Principle of electrostatic adsorption

-There is a high-voltage electric field inside the electrostatic precipitator. When the boiler flue gas enters the electric field, the dust particles will be ionized in the electric field. Gas molecules are ionized into positive and negative ions under the action of a high-voltage electric field, and dust particles also become charged after colliding with these ions. Positively charged dust particles move towards the negative electrode (collecting electrode), while negatively charged dust particles move towards the positive electrode (discharging electrode). During the movement, dust particles are adsorbed on the dust collection electrode and discharge electrode, thereby achieving the separation of dust and gas.

-The electrostatic precipitator has high dust removal efficiency, can handle a large amount of flue gas, and has good capture effect on dust of different particle sizes, especially for sub micron dust with particle sizes of 0.1-1 microns, it has outstanding removal ability. However, its equipment investment and operating costs are relatively high, and it has certain requirements for the conductivity and other properties of dust.

4、 Wet dust removal

1. Principle of washing and dust removal

-Wet dust collector uses water or other liquids to wash boiler flue gas. When the flue gas enters the wet dust collector, it comes into full contact with the sprayed washing liquid, and the dust particles are captured by the liquid. For example, in a wet dust collector of a spray tower, the washing liquid is sprayed into the tower through a nozzle, forming small droplets. The flue gas collides and mixes with the droplets, and the dust particles are adsorbed by the droplets. Then, under the action of gravity, the dust containing droplets fall into the water tank at the bottom of the tower.

-Wet dust collectors are effective in removing water-soluble and viscous dust from boiler flue gas, as well as providing cooling and desulfurization functions. But it also has some drawbacks, such as generating wastewater that requires further treatment, and the equipment may be corroded.

The boiler dust collector separates the dust particles in the boiler flue gas through these different dust removal mechanisms, reducing the pollution of dust to the environment and also helping to protect the normal operation of the boiler system and other related equipment.