I. Introduction China is the world's largest producer of phosphate compound fertilizers. The production of phosphate compound fertilizers is mainly high-concentration phosphate compound fertilizer products-diammonium phosphate. Since the main raw materials for the production of diammonium phosphate are phosphate ore, sulfuric acid, liquid ammonia, etc., the market price continues rise. Due to the international financial crisis, the prices of phosphate compound fertilizers have fallen in the international market in recent years, and the export volume has also been declining. This has led domestic phosphate compound fertilizer manufacturers to do everything possible to reduce production costs. The important agenda of survival comes up. Our company built a 600,000 t / year diammonium phosphate plant in November 2011, and its device is equipped with two ykk560-6 / 10kV, 900kW motors as dry exhaust fan and granulation exhaust fan. 2. Production process 2.1 Process sketch. The production process diagram is shown in Figure 1. Figure 1 Process diagram 2.2 Introduction to production process At the entrance of the granulator, the cross-tube reactor sprays phosphoric acid into a mist through a high-pressure pump, and then sprays liquid ammonia into a mist through a high-pressure pump. ) (NH4) 2HPO4, liquid ammonia is in vapor state, encounters misty phosphoric acid liquid to generate translucent diammonium phosphate crystals, and crystallizes in the granulator after reacting in the front of the granulator. After the granulator rotates the crystals and bonds to form larger granule crystals, it falls out of the granulator outlet, and the unreacted ammonia gas is pumped to the washing tower at the control point 1 of the granulator air duct. Recycling, to prevent ammonia gas from overflowing from the control point 1, as long as negative pressure is formed at the outlet of the granulator, controlled by the electric valve of the inlet of the granulation fan, the negative pressure of the control point 1 only needs -0.5 ~ -1KPa, It can not only meet the requirements of the production process, but also reduce the large amount of ammonia gas pumped into the washing tower, so it is not that the larger the power of the granulation fan, the better. Similarly, the negative pressure of the dryer at control point 2 only needs to be -0.5 ~ -1KPa. The heat of the diammonium phosphate in the dryer is generated by the sulfur incinerator. The heat is sucked into the dryer by the drying fan as long as the diammonium phosphate is in The water content at the outlet of the dryer can meet the requirements, and the air volume control is also controlled by the electric air valve at the inlet of the drying fan. The device is designed to install a fan with a flow rate of 21500 Am3 / h, a suction pressure of -5.85 / -6.12 KPa, a solid content of 150-400 / 1000 mg / Am3. Fertilized dust F-, Cl-, and SO4-acid corrosion. The motors of the two fans are 50HZ (994r / min). When the granulating fan and the drying fan are started, the air inlet valves of the two fans must be completely closed to start the motor. The following problems have occurred in actual use : (1) When the two fan motors are running at 50HZ, the fan system can be heard beyond 2km due to fan howling and air channel vibration noise, and the whole plant is in the fan noise pollution. (2) In actual use, the opening of the electric air valve of the granulation fan is about 35%-40%, and a large amount of acid vapor substances impact the air valve and the air pipe. The electric valve adjustment is often adjusted excessively depending on the operator's experience, and the washing tower has many substances. The acid water and dust in the washing tower are continuously sucked into the fan and flow out from the blowdown pipe at the lower part of the fan. The motor runs at 50HZ for a long time, which causes a lot of waste of electrical energy. Fans and motors are worn at high speeds, fans and air pipes, air valves, washing tower equipment, etc. have large air flows and acid vapors are more seriously worn and corroded. (3) When two fans are started, the requirements on the power grid are high. The owner of our factory has become one SZ10-31500 / 110 / 10KV, and another two QF-J7.5-2 / 7500kW / 10kV generator sets. The generators are connected to the grid on the 10kV side of the main transformer. Although the inlet valves of the two 900kW / 10kV fans are all closed and the motor is started, the voltage of the 10kV side of the main transformer drops instantly when the actual fan motor is started. Due to the sampling control of the generator, the generator is also affected by the instantaneous voltage drop on the 10kV side of the main transformer. The generator's instantaneous power generation output power cannot be controlled, the instantaneous surge of more than 1,000 kVA, and multiple fault alarms. (4) When two fans are started, the electric air valve is required to be closed, but because the operator often does not close the air valve or the electric air valve is corroded and stuck due to acid vapor, etc., after starting the first fan, the control point 3 is two fans and air outlets. If the electric fans of both fans are not tightly closed, the first fan will blow the wind into the second fan and reverse the second fan. At this time, if the second fan is started In the second typhoon, from reverse to forward rotation, the fan and shaft must bear a huge shear force, and the motor must bear a huge reverse torque. The electrical shock rises several times, and the fan and electrical equipment are easily damaged. In view of the above four aspects, decided to carry out fan frequency conversion transformation. 3. Fan renovation 3.1 Inverter system solution After many comparisons, it was decided to choose 2 HARSVERT-A10 / 070 high-voltage frequency converters produced by Beijing Leader Huafu Electric Technology Co., Ltd. The system scheme is shown in Figure 2. It consists of three high-voltage isolation switches QS1, QS2 and QS3 and the original high-voltage switch QF to form a control motor power circuit. There is a mechanical interlock between QS2 and QS3, which cannot be closed at the same time. Normally, when the inverter is running, QS1 and QS2 are closed and QS3 is opened. 10kV power supply is closed by QF (charging 12 ~ 15s), start VFD frequency converter. The frequency converter starts the motor at the given speed. Abnormal conditions such as inverter failure, QS1, QS2 are open, QS3 is closed, the 10kV power supply is closed, and the motor is started directly at the power frequency. 3.2 Frequency control scheme The inverter control scheme is shown in Figure 3. Figure 3 Production process inverter control scheme The original electric cabinets in the 10kV distribution room are equipped with QF vacuum circuit breakers and NARI RCS-9626CN integrated relay, integrated control operation panel, etc. The "remote" and "local" control can be selected through the integrated switch on the operation panel; "remote" refers to the completion of the QF operation of the "opening and closing" circuit breaker in the electrical background, and "local" refers to the on-site process operator Complete the "open and close" circuit breaker on the operation box. After the 10kV power supply passes through the QF circuit breaker to the VFD of the inverter, after 12 seconds of charging, the inverter is charged and tested. It is allowed to cast the inverter. The process operation starts the inverter on the on-site operation box. The inverter runs at low speed and controls the fan motor to rotate at low speed. After starting another fan to rotate at a low speed, the process DCS alternately adjusts the variable frequency given value, which can effectively prevent the reverse rotation of the fan. Use the RCS-9626CN comprehensive relay protection instrument to effectively transfer the motor running signal, measurement signal and various protections of the motor to the electrical background for monitoring and protection. Coupled with the inverter body protection and motor protection and control functions configured by the inverter, the fan motor is double protected and monitored. 4. Basis for application 4.1 Field conditions and load technical data (1) The operating parameters of the drying exhaust fan are shown in Table 1. (2) The operating parameters of dry particle exhaust fan are shown in Table 2. V. Transformation process and process optimization 5.1 Transformation process (1) According to the actual situation, build the control room required by the inverter, and determine the layout plan of 2 sets of 1 room and 1 row. (2) According to the existing electrical background, 10kV switchgear, relay protection configuration, and process DCS control system, it is matched with the functions provided by the newly installed 10kV inverter to optimize the most reasonable control plan. (3) Install and wire according to the determined plan, and ask the manufacturer's technical personnel to guide the commissioning work. 5.2 Process optimization (1) The key to optimizing the process control parameters is to make sure that the granulation fan control point 1 is around -0.5KP to meet the process requirements, and the drying fan control point 2 is around -0.5KP to meet the process requirements. (2) It is refined to control by the revolution of the inverter, or it can be frequency conversion given 4-20MA (0% -100%) corresponding to the motor 0-960r / min. The upper limit of the frequency is used for limitation. Improve process control accuracy and facilitate process operation. Sixth, the effect after transformation (1) In normal production, the frequency converter of the granulation fan actually runs between 27-30 Hz, and the frequency converter of the drying fan actually runs between 29-35 Hz. In the fan system, the howling of the fan basically disappears, and the air duct is effectively released At the resonance point, the noise can only be heard within 20m. The whole factory is quiet. The most important thing is that there are no complaints. (2) The frequency conversion energy-saving effect is remarkable, and our factory compares the average value of the power consumption of the fan 1 month before the renovation and 1 month after the transformation as follows: It is produced in 24h every day, and calculated in 30 working hours per month, calculated at 0.4 yuan / kWh, as shown in Table 3 and Table 4. Table 3 Before using the inverter Table 4 After adopting the inverter (3) Each month can save 793400KWh of electricity and 317360 yuan of electricity bill. It only takes 4 months to change the cost of investing in inverters. (4) The inverter is started in 3 stages, each stage is set for 60s. There is no impact on the power grid, and the generator does not have a sudden increase in power generation and out of control. (5) In actual operation, the speed of the fan is reduced, the wear of each component of the fan system is also reduced, the amount of acid dust and ammonia is greatly reduced, and the equipment corrosion is reduced. 7. Conclusion After the technical transformation of two 10kV fan motor frequency converters in our plant, the ideal results have been achieved in all aspects, especially in terms of energy saving, which has achieved better results than the original plan. Break the misunderstanding that the original 10kV inverter has a large investment and a slow benefit, and choose the HARSVERT-A10 / 070 high-voltage inverter produced by Beijing Leader Huafu Electric Technology Co., Ltd., There is no quality problem after 3 months of use, and the price of each set is only half the price of imported inverters. After testing, the harmonics of the power grid are basically free of pollution, and it is a high-voltage inverter with high cost performance. Our factory is now ready to fully carry out energy-saving and consumption-reducing actions of enterprises, carry out energy-saving evaluation on the currently put into operation motors, especially high-voltage motors, and find motors with energy-saving space for frequency conversion transformation. references: 1. Beijing Leader Huafu HARSRVERT-A Series Technical Manual. 2. Nanjing Nanrui RCS-9600 Series Technical Manual. Hinge,High Quality Hinge,Hinge Details, Sunzhengde Hardware Mfg Co., Ltd. Sunzhengde Hardware Mfg Co., Ltd. , https://www.sunzhengde.com
Figure 2 System solution 
