Blast furnace centrifugal fan working principle and operation requirements

What is a centrifugal blower?

The centrifugal fan is a machine that relies on the input mechanical energy to increase the gas pressure and discharge the gas. It is a driven fluid machine. Centrifugal fans are widely used in ventilation, dust removal and cooling in factories, mines, tunnels, cooling towers, vehicles, ships and buildings; ventilation and induced draft in boilers and industrial furnaces; cooling and in air conditioning equipment and household appliances. Ventilation; drying and selection of grain; air source of wind tunnel and inflation and propulsion of hovercraft, etc.

The principle of blast furnace centrifugal blower

The centrifugal fan is based on the principle of converting kinetic energy into potential energy, using a high-speed rotating impeller to accelerate the gas, then decelerate and change the flow direction, so that the kinetic energy is converted into potential energy (pressure). In a single-stage centrifugal fan, the gas enters the impeller from the axial direction, changes to the radial direction as the gas flows through the impeller, and then enters the diffuser. In the diffuser, the gas changes the direction of flow and the increase in the cross-sectional area of the duct slows down the gas flow, which converts kinetic energy into pressure energy. The pressure increase occurs mainly in the impeller, and secondly in the diffusion process. In a multi-stage centrifugal fan, a recirculator is used to move the airflow to the next impeller, creating a higher pressure.

What does a centrifugal fan consist of?

The centrifugal fan is composed of a casing, a main shaft, an impeller, a bearing transmission mechanism and a motor.

Chassis: It is made of steel plate, which is strong and reliable. It can be divided into integral type and semi-open type, and the semi-open type is convenient for maintenance.

Impeller: consists of blades, curved front disc and flat back disc.

Rotor: Static balance and dynamic balance should be done to ensure smooth rotation and good performance.

Transmission part: It consists of main shaft, bearing box, rolling bearing and pulley (or coupling).

Application of blast furnace centrifugal compressor

Centrifugal fans are widely used in ventilation, dust removal and cooling of factories, mines, tunnels, cooling towers, vehicles, ships and buildings; in the ventilation and induced draft of boilers and industrial furnaces; in air conditioning equipment and household appliances cooling and ventilation; drying and selection of grain; air source of wind tunnel and inflation and propulsion of hovercraft, etc.

1. Centrifugal blower clean air treatment

In industrial operations and facilities, air movement is always part of the process. Air handling fans support your operation and the surrounding ambient air. Processes range from industrial system components, to make-up air units, to renewal.

2. Centrifugal blower light dust load

Industrial processes use light dust loading and fume extraction fans as part of the overall dust collection system to improve air quality and safety. They move air and material through the system to capture, collect and transport particles through various parts of the system. These can include range hoods, air filtration, dust collectors (such as baghouses), steam traps, and of course air ducts.

3. Centrifugal blower material handling

Centrifugal material handling fans can handle particles such as sand, plastic pellets, sawdust, wood chips, grain, paper trim, pet food and countless others. They range from small and light to larger, heavier and more abrasive.

4. Centrifugal blower heat treatment

Many industrial processes rely on high temperature process heat. Operations such as heat treatment, stress relief, industrial furnaces and ovens use convection to circulate hot air in a room. These process air streams require specially designed centrifugal fans. Improper design of fans used in designs above this temperature will result in catastrophic failure.

Operating requirements for blast furnace centrifugal compressor

Requirements for blower under normal production conditions of blast furnace

1. The constant air volume operation of the blower. The stability of the air supply is a necessary condition for the furnace temperature of the blast furnace to be stable and the gas in the furnace to be stable. The fluctuation of the air volume affects the speed of the feeding speed, which in turn affects the heat balance of the hearth, causing the thermal system in the hearth to fluctuate, and in severe cases, the furnace condition will be abnormal. Therefore, the blower is required to operate at a constant air volume so that the air supply volume is relatively stable.

When the blast furnace needs to increase the air volume, it should be increased gradually to avoid damaging the blast furnace forward. When the air is reduced, it can be quickly reduced to the required air volume at one time.

2. The constant air pressure operation of the blower. All blast furnace forward factors will affect the wind pressure, and the reaction is fast, so the wind pressure is one of the main parameters for judging the blast furnace condition. Under normal circumstances, the general wind pressure fluctuation of a large blast furnace is not more than 0.01 MPa.

When the hot blast stove is replaced, air is supplied to both hot blast stoves. If the original constant air volume is still used for operation, the pressure of air supply to the blast furnace will drop, resulting in unstable furnace conditions, so it should be operated with constant air pressure at this time. Under constant air pressure operation, the blower automatically increases the air volume required for charging the hot blast stove, while the air pressure remains unchanged. After the charging is completed, the constant air volume operation is still restored.

When the blower is replaced, it is required that the outlet air pressures of the two blowers be switched when they are very close or equal. At this time, the use of constant air pressure operation will make the machine more stable and fast when reversing.

Requirements for blower in abnormal production of blast furnace

1. Low feed line. When the blast furnace cannot be charged on time, the top material surface will gradually drop, so that the low material line is called when the probe is more than 0.5 m lower than the normal specified material line. When a low material line occurs, generally reduce the wind.

2. Suspended material. When the blast furnace charge stops falling for more than 1 to 2 batches, it is overhang. When the material is suspended, due to the suspension of the material column, the air permeability is deteriorated, the air volume blown into the hearth is reduced, and the air pressure is also higher and higher, which will cause the fan to surge in severe cases. If it is not dealt with in time, the pressure difference between the hearth and the furnace top will become larger and larger, and it will become more difficult to cut the material, making the hanging material more and more serious. When the overhang occurs, the air valve is often opened to quickly reduce the air by 10% to 15%, or other operational measures are taken to strive for the reduction of the charge.

3. Seating. The purpose is to collapse the suspended charge. That is, artificially quickly open the air release valve on the cold air pipe to release the air, so that the air pressure drops rapidly until it drops to 0.01 MPa ~ 0.005 MPa, and maintains it for 3 min to 5 min, so that the charge loses the floating force of the gas in the furnace and collapses. . The air pressure of 0.01 MPa to 0.005 MPa must be left when the material is set to prevent the gas in the furnace from flowing back into the air duct and causing an explosion.

When the material is set, due to the sudden release of air, the air pressure of the blower decreases rapidly and the air volume increases, resulting in an abnormal situation. Therefore, the blower station should be notified in advance to reduce the load of the blower before feeding.

4, rest wind. In the blast furnace production process, due to temporary maintenance, the air supply to the furnace is stopped for a short period of time, which is called air break. The wind break for more than 6 hours to 8 hours is called long-term wind break. At this point the blower can be stopped. Generally, short-term wind break is adopted to release air to stop supplying air to the blast furnace. At this time, the blower needs to take corresponding measures to adjust the air volume.