Application of FD5000 in Primary Air Fans of Steel Plants
In coal-fired power generating units of steel plant self-provided power plants, traditional primary air fans adopt the regulation mode of power frequency constant speed operation plus damper throttling. Fan motors connect directly to power frequency power supplies and run continuously at rated speed. They do not adjust the speed according to boiler load and unit power generation demand. On-site air volume and pressure regulation relies entirely on opening or closing inlet and outlet dampers. It passively adapts to air demand by increasing air duct resistance and throttling, which is an inefficient throttling regulation method. Under the traditional operation mode, the actual operating efficiency of primary air fans stays below 60% for a long time, with obvious defects:
1.The regulation method is outdated. Damper throttling causes massive pressure loss and electric energy waste.
2.Fan output mismatches the actual load. Invalid energy consumption remains high, and the plant power consumption rate stays at a high level.
3.Equipment operates away from the high-efficiency working condition for a long time. It suffers severe wear, poor stability and high maintenance costs.
A foreign steel plant intends to upgrade and transform the traditional primary air fan system in a targeted way. It aims to save energy, reduce consumption, improve operation efficiency and stabilize the working condition of coal-fired power generating units.
Implementation Plan
According to the fan parameters of the foreign customer, we select the FD5000 series high-voltage frequency converter with the model FD5000-6/1000F-1A. The main circuit is shown in the figure below.
The system protects the frequency converter physically through an automatic bypass cabinet. It also has master-slave synchronization and low-frequency compensation functions to achieve power balance and stable start-up. It delivers excellent output performance at low frequencies and meets the demand for heavy-duty start-up. And it has no restrictions on start-up time and times.
We adopt the one-to-one automatic mode. This mode ensures automatic switching to power frequency when the frequency converter has a major fault, so the load keeps running. It also avoids the whole-line shutdown caused by single-point fault of the frequency converter, prolongs the overall service life of equipment and reduces the loss from unplanned shutdown.
Application Advantages
1.We cancel the throttling damper and use the frequency converter to adjust the motor speed directly. This realizes the precise output of air volume and pressure on demand. The system features high control precision and remarkable energy-saving effect, and improves the operating efficiency of fans.
2.System collaborative optimization: The system has a complete protection system with various built-in software protections. It realizes automatic control and optimized management of the production process, improves production efficiency and reduces the cost of manual intervention.
3.Excellent speed regulation performance and control capability: High-voltage variable frequency speed regulation technology can achieve high output power and cause little harmonic pollution to the power grid.
