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Application of High-Voltage Frequency Converter in Energy-saving Reform of Circulating Ammonia Pump

Aug 26, 2020

Application of High-Voltage Frequency Converter in Energy-saving Reform of Circulating Ammonia Pump

Frequency conversion speed regulation is a mature new technology that has emerged in recent years. It realizes speed adjustment by changing the power frequency. Because of its stable speed regulation, high transient stability, and energy saving, it is increasingly being valued by people. . With the continuous maturity of frequency conversion speed regulation technology, the application of frequency conversion speed regulation devices in water pump equipment has become more and more extensive.


  1. Working conditions and problems of circulating ammonia pump


  1.1. Working condition characteristics of circulating ammonia pump


In the first phase of the purification plant, there are two circulating ammonia pumps, one used and the other prepared. The pump set pumps the circulating ammonia water into the gas collecting pipe for preliminary cooling of the raw gas, and controls the raw gas temperature to 75-80 degrees before sending it to the primary cooler. The amount of raw gas should be adjusted in time to circulate ammonia.


  1.2. There are problems in power frequency operation:


   The two circulating ammonia pump motors both operate at power frequency and have high starting current, which not only affects the life of the equipment but also has a great impact on the power grid. Moreover, the power frequency operation consumes high power and cannot be automatically adjusted with the production load, which does not conform to the management concept of "energy saving and consumption reduction" of modern enterprises.


  The circulating ammonia pump runs at power frequency, and the flow and pressure can only be adjusted through the bypass valve and the outlet valve, but the adjustment load is limited. At the beginning of 2012, the coking time was long, the amount of raw gas was small, and the circulating ammonia flow could not be further reduced. As a result, the temperature of raw gas was extremely low. The fluidity of the tar-ammonia mixture in the pipeline is extremely poor, and there is a hidden danger of blocking the raw gas pipeline. It can be seen that the raw gas temperature is a crucial indicator. If it is not properly controlled, the entire purification system will be paralyzed.


   The circulating ammonia pump was originally designed for power frequency operation, and only the operator can adjust the pump outlet valve and the opening of the circulating pipe valve to control the circulating ammonia water pressure and flow. If the amount of circulating ammonia water changes and the staff on the post cannot adjust in time, the pressure of the circulating water pump will be too high or too low. If the pressure is too high, it will cause pump seals and motor burns; if the pressure is too low, it will lead to uncontrollable raw gas temperature, excessive collection temperature, and serious blockage of primary cooling, electric capture and gas purification systems.


  2, transformation plan


   The circulating ammonia pump is an important equipment to ensure the normal operation of the gas system of the coking plant, and it must ensure continuous, stable and reliable operation. After detailed technical and economic demonstrations, it was decided to adopt a high-voltage frequency conversion speed control device, and the motor speed can be adjusted to meet the technological requirements through frequency conversion speed control.


The high-voltage variable frequency speed regulation system adopts power unit series technology to directly output 10KV voltage, which is a high-voltage source type inverter. The overall structure of the high-voltage inverter speed control system is composed of bypass cabinets, transformer cabinets, unit cabinets and control cabinets. Adopt a dual-circuit power supply scheme with one use, one standby and two pumps, one with two manual bypasses. The basic schematic diagram is as shown below


  Dual power supply manual switch cabinet once schematic diagram


   This system consists of high-voltage switches 1QF, 2QF, dual-power manual switching cabinets (composed of high-voltage isolating switches QS1-QS6), high-voltage inverters, and two high-voltage motors. The dual-power manual switching cabinets and high-voltage inverters are provided by the bidder.


Description: ①QS2 and QS3 are double-pole double-throw isolating switches, QS5 and QS6 are also double-pole double-throw isolating switches; realize natural mechanical interlock ②QS1 and QS4 cannot be closed at the same time to achieve electrical lockout; QS2 and QS5 cannot be closed at the same time to achieve Electrical lock; ③When the inverter fails, the corresponding high-voltage switch will be combined. The cabinet doors have high-voltage locks. After the high-voltage power is turned on, the cabinet doors will be automatically locked by the electromagnetic lock, unless a special key is used. Open the cabinet door.


   3. Operational reliability analysis


After many debuggings, it is realized that the frequency converter controls the motor speed to change with the change of the outlet pressure of the circulating ammonia pump, which reduces the power consumption and reduces the noise of the motor. The improvement effect is very obvious: ①The power saving effect is significant, and the motor stator current From 15A to 6A, the daily electricity saving is about 3500 degrees. ② The speed of the motor decreases, and the operating conditions of the motor and pump are significantly improved, which extends the service life of the equipment and reduces the maintenance cost of the equipment. ③After adopting frequency conversion speed regulation technology, because the pump outlet valve is fully opened, the noise caused by throttling of the valve is eliminated, and the working environment is improved; ④The acceleration and deceleration of the motor can be automatically adjusted according to the process requirements, and the control accuracy is high, which is guaranteed The production index is stable and the workload of workers is reduced. ⑤The pressure of the circulating ammonia water is stable, which avoids pressure fluctuations, significantly reduces pipeline leaks, and reduces maintenance work.


  4. Economic benefits produced


  According to the above data, it is known that the daily electricity saving is about 3,500 kWh, the monthly saving is 106,500 kWh (calculated in 30 days), and the annual saving is 1,277,500 kWh. Based on the 0.48 yuan per kWh, the annual electricity saving is 613,200 yuan.


  5 Conclusion


With the increasingly fierce market competition and the increasingly stringent national requirements for energy conservation and emission reduction, it is particularly important for enterprises to save energy, reduce production costs, and improve competitiveness. The inverter has been put into use for nearly four months. The outlet valve is fully opened and the operation is stable, reducing the energy loss caused by the valve closure, and the energy saving effect is obvious, the soft start of the motor is realized, and the service life of the motor, pump and auxiliary equipment is prolonged. Practice has proved that the application of high-voltage frequency converter in the circulating ammonia pump is very successful.