Application of Fan in Cement Industry
Solution of Frequency Conversion and Energy Saving of Fan in Cement Industry
Such equipment like vertical kiln and rotary kiln fan in cement industry needs great power consumption, high starting current and whose transformer is large enough to have enough, In the air duct system design, in order to meet the requirements of the production environment, we must have a margin. Therefore, the air volume and the pressure of the fan are often too large, the power of the large design will inevitably lead to waste of energy. In the traditional situation, are used to regulate the flow of the valve, and some of the bypass valve or return valve to solve the flow and pressure margin is too large problem, These methods all have very large energy consumption, A lot of fans have 30 to 70% of the energy is consumed in the pressure drop on the regulator, which is not only a waste of energy, low efficiency, and often cause accidents.
In recent years, the frequency conversion technology has completely changed the situation, Practice has proved that the use of frequency conversion technology to change the speed of the motor to adjust the air flow and pressure changes can achieve significant energy saving effect.
1. 1.Energy saving principle
Fan operating shaft kiln, rotary kiln is determined by the load, According to the theory of fluid mechanics, the relationship between motor shaft power P and air volume Q, pressure H is:
K is a constant;
η means efficiency.
The relationship between them and rotational speed N is:
The curve in the figure 1 for fan characteristic curve at constant speed under the pressure of H and flow rate Q, the curve 2 is the pipe network drag characteristics (the valve opening degree is 100%). Assuming the wind turbine in the design work at the A point of the highest efficiency, the output of the wind Q1 is 100%, at this time the shaft power P1=Q1*H1 is proportional to area AH10Q1. According to the process requirement, when the air volume is reduced from Q1 to Q2 (e.g. 70%), the use of the method of adjusting the valve is equivalent to increase the resistance of the pipe network. The resistance characteristic of pipe network is changed from curve 2 to curve 3, and the system is changed from the original working condition A point to the new working condition B point operation, It can be seen from the figure that the wind pressure has increased, and the axial power BH20Q2 is proportional to the area P2, and the reduction is not much.
If the use of frequency control method controls the fan speed from N1 down to N2, According to the proportion of wind turbine law, can be drawn at the speed of N2 under pressure H and flow Q characteristics as shown in curve 4, We meet the same situation can be found in the air Q2, H3 wind pressure will be greatly reduced the power of P3 (equal to the area of CH30Q2) with significantly reduced, saving the power of delta P= Delta HQ2 and BH2H3C is proportional to the area, Energy saving effect is very obvious.
The fluid mechanics, a side air volume Q and the speed is proportional to the pressure and speed is proportional to the square of H, P and the speed of shaft power is proportional to the cube, when the flow rate decreased, fan speed decreases, the power down a lot.
For example, air dropped to 80%, the speed dropped to 80%, while the shaft power drops to the rated power of 51%; the amount of wind power can be decreased to 50%, P decreased to 13% of the rated power, of course, because of the actual condition of the actual value, such is not so obvious, even so, the energy-saving effect is very obvious.
Therefore, in the mechanical equipment of the fan and water pump, the variable frequency speed regulation is adopted to adjust the air flow and the flow rate, and the energy saving is one of the most effective methods.
2.Energy saving system:
To sum up, as long as the normal production process in the opening of the electric valve below 85%, after the installation of energy-saving systems, we expect the rate of energy conservation should be more than 30%. At the same time, energy saving system also has the following advantages:
1) using the closed loop control system, reliability, accuracy and stability are greatly improved.
2) to achieve motor soft start, to eliminate the impact of motor starting current, to extend the service life of mechanical equipment.
3) ACI converter has a unique control:
The inside of the braking unit (7.5KW and a) can be externally connected to the brake resistance, can get a lot of braking force;
Protection function is more substantial;
Surge current suppression circuit (optional);
High speed current limiting function, inhibit over current jitter (180% of rated current). Make jitter free running (stop and start running, stall prevention function, abnormal reset and try again, etc.) to a higher level.
ACI inverter can completely meet the requirements of energy saving in the cement industry. And the effect that is very obvious has been unanimously approved by the majority of users. Our products are worthy of our trust.