Research and Application of Water Pump Frequency Conversion and Electricity Conversion Technology in Laiwu Steelmaking Plant

Research and Application of Water Pump Frequency Conversion and Electricity Conversion Technology in Laiwu Steelmaking Plant
The core tips: Frequency conversion energy-saving Chinese map law classification number TM344.6; Sign code B1 proposed pump equipment (especially centrifugal pump) used in a large number of steel steel plant circulating water system, long-term continuous operation, power consumption is very Big. The efficiency of pump operation is crucial to saving electricity. Water pump

Frequency conversion transformation energy-saving Chinese map law classification number TM344.6; logo code B1 proposed pump equipment (especially the centrifugal pump) is widely used in steel steelmaking plant circulating water system, long-term continuous operation, great power consumption. The efficiency of pump operation is crucial to saving electricity. The traditional operation mode of the water pump is that the rotation speed is constant, and the size of the flow is adjusted by using a valve, a return valve, etc., thus causing a large amount of energy waste.

Since the valve is often adjusted to adjust the amount of water, the valve is frequently damaged and leaks, and needs to be shut down for replacement. The above reasons lead to waste of electrical energy, waste of spare parts of the pump, and shutdown of the production line.

If the use of water pump frequency conversion technology, can save 20% -40% of electrical energy. In addition, the frequency conversion speed regulation has high efficiency and a wide range of speed regulation, and is particularly suitable for long-time operating conditions. It can also soft start, can reduce the impact on the grid, the operation is simple and labor-saving; because the speed is reduced after the pump noise is reduced, wear is reduced, so that the pump and regulating valve life is extended, the amount of maintenance is also reduced. In addition, the flow rate can be controlled more accurately and quickly according to the requirements of the production process.

Therefore, energy-saving transformation of the pump area can completely achieve a better energy-saving effect, and facilitate the real-time control of power consumption per ton of steel.

Energy-saving and consumption reduction has always been the goal pursued by various units of Laiwu Steel. Steel-making steel plants are also large households of Laiwu Steel's electric energy consumption. They consume more than 2 hours of electricity per month, and their electricity bills exceed RMB 12 million. Therefore, they need to be strictly enforced. control. As the main unit of electric energy consumption, the steelmaking plant must carry out power-saving control in accordance with the company's steel consumption target per year. Since the main line does not save space for the production of electrical energy, energy saving control can only be started from the auxiliary equipment. The traditional management approach is to strictly control opening and shutting down time by issuing management regulations, conducting spot checks from time to time, and relying on the subjective awareness of personnel. Since the implementation of this management, the management efficiency is low and the power saving effect is poor. Therefore, new ways to save electricity must be found to change the situation. Steel plant has converter water pump house, refining furnace water pump house, and continuous caster pump house. Because the production equipment needs continuous cooling, the water pump house pumps need to run continuously. According to the statistics of the power report, the monthly electricity consumption of the pump house accounts for the entire factory month. With 40% of the electricity consumption, the power saving of the pump room can greatly reduce the electricity consumption per ton steel of the steel section steelmaking plant and achieve the purpose of resource conservation.

October 18, 2011 Received the basic principle of 2 frequency conversion energy-saving transformation The pump is a quadratic decreasing torque load. The rated flow rate of the used water pump usually exceeds the actual flow rate. Because the flow rate needs to be adjusted according to the process requirements, the valve is used to adjust the water pump. Some of the work done is wasted, and this method of artificially increasing resistance actually achieves the goal of regulating the flow, but it wastes a lot of electricity, and if it does not do so, the recovery of this part of the power consumption will receive very good energy savings. effect. The relationship between flow rate and motor rotation speed and motor power is as follows: From the above formula, it can be seen that when the actual flow rate Q decreases, the pump lift H and the motor shaft power P decrease in square sum cubic terms, respectively.

Obviously, when using speed regulation, assuming that the required flow rate Q is reduced from 1 to 3/4, as long as the speed is reduced from 1 to 3/4, the shaft power is reduced from 1 to 3/4 cubed = 27/64. = 0.42, that is, 0.58 electric power is saved, and the efficiency is very significant. If traditional throttling is used, the rotational speed remains constant and the valve opening decreases. (At this time, the resistance of the pipeline increases.) At this time, when Q decreases from 1 to 3/4, the head H does not change much, and most of them increase slightly. In addition, as the flow rate Q decreases, the pump efficiency also decreases.

3 Retrofitting situation Through one year's time, our factory carried out frequency conversion control transformation of the 14-220kW pump motor control system in the pump room system, and used the special pump-type inverter from Siemens to replace the original Schneider soft starter. (Panel operation keys) or remote control (PC control analog potentiometer automatic control mode), the use of remote control during normal control, manually through the upper computer flow, pressure meter to determine the amount of water, manually adjust the pump motor operating frequency on the PLC screen ( Speed), can achieve the purpose of regulating the amount of water, the original need for two pumps at the same time the water supply equipment, Taiwan pump valve fully open, the maximum flow, another pump need to manually adjust the outlet valve to regulate the flow, the second pump motor running at full speed , Produce less flow, and lead to the occurrence of helium pumps, after the transformation, the two pumps in the case of ensuring the water supply, can all run at a reduced speed, not only saves electricity, but also ensure the long-term stable operation of mechanical pumps.

The schematic diagram of the control circuit after the transformation is as follows.

When the inverter power contactor MC closes, it sends a ready signal to the PLC. Start the inverter through the computer screen, and adjust the given frequency of the inverter on the screen according to the actual need of the flow and pressure of the caster to reach the optimal load for actual needs to prevent the waste of water and electricity.

When the inverter is stopped in a fault, the fault can be displayed on the computer screen and flashes on the screen. The operator is notified to stop the pump. The operator can promptly notify the maintenance and remotely reset and start again.

Install frequency conversion control cabinets, air switches, and motor cables. Consider the on-site working environment. A 1.2m power cabinet (1200x900x300mm) is equipped with a unique anti-corrosion, moisture-proof heat sink. The main circuit and other vulnerable places spray insulating paint or sealant. The system is stable and the starting current is greatly reduced. The small stator and rotor losses are very beneficial to extend the life of the motor. It can also reduce noise, reduce motor heat generation, improve the load characteristics of the pump, and improve the system's operating efficiency. The energy-saving rate can reach 20%. 4 After transformation of power-saving transformation, the equipment runs smoothly and the energy-saving effect is significant.

4.1 Efficient and energy-saving, to achieve a balance between supply and demand Through the analysis of on-site working conditions, the frequency conversion of the water pump with space saving is implemented. After the transformation, the energy-saving effect is obvious, and the monthly energy saving is about 241,000 kW h. Table 1 is cumulative after the transformation. The electricity saving of the month, data is shown in Table 1. Table 1 Electricity statistics Order equipment name Electricity saving rate April 185 months 15 meter reading volume meter reading ratio saving electricity saving swirl well 101 pump 1 cyclone well 104 pump 1 Cyclone well 203 Pump 2 Cyclone 101 Pump 1 Turbid ring 302 Pump 2 Turbid ring 102 Pump 2 Clean ring Pump room 103 Pump 1 Clean ring Pump room 402 Pump 1 Clean ring Pump room 503 Pump 1 Clean ring Pump room 702 Pump 1 net ring pump room 802 pump 1 net ring pump room 1101 pump 1RH pump room 211 pump 1RH pump room 212 pump 55 yuan calculation, the annual electricity savings: 12x241000X0.55 = 1.59 million yuan.

4.2 increase power factor, reduce reactive power As the original motor driven by the power frequency, the power factor at full load is about 0.85, the actual operating power factor is much lower than 0.8. After the use of variable frequency speed control system, the power factor of the power supply side can be increased to Above 0.9, no reactive power compensation device can greatly reduce the reactive power, meet the power grid requirements, and can improve the operating cost of upstream equipment. 4.3 Reducing mechanical wear and reducing maintenance costs After variable frequency control, energy saving is achieved by adjusting the motor speed. When the load factor is low, the motor speed is also reduced. The wear of the main equipment and corresponding auxiliary equipment such as bearings is less than before, and the maintenance period can be reduced. Longer, longer equipment operating life; and after the frequency conversion valve opening up to 100%, due to eliminate the frequent switching valve and pump situation, so extend the life of mechanical equipment such as valves, water pump body.

4.4 The degree of automation is increased, and the labor intensity of workers is reduced. According to the process requirements, the amount and pressure of water supply need to be adjusted. The amount of water is adjusted by the operator to manually rotate the valve on the spot to complete the mouse click on the computer screen to reduce labor intensity and improve labor efficiency.

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