Application of Frequency Converter in Energy Saving Technical Transformation of Carbon Black Production

The Maoming Technician College (525000) in Guangdong province applied the example of energy-saving technology reformation to the air-compression blower, analyzed in detail the energy-saving principle of the frequency conversion speed control of the fan, the transformation process of the frequency conversion technology, and the energy-saving and operational effects of the fan. It is clarified that the fan frequency conversion speed regulation technology not only has a significant effect on energy saving and consumption reduction, but also improves the stability and reliability of the fan operation, and is simple to install, convenient to maintain, and produces good economic benefits.

Since the “Eleventh Five-Year Plan” period, based on the urgent requirements of energy conservation and consumption reduction, the National Development and Reform Commission announced in its April 2007 energy development plan for the 11th Five-Year Plan that China's energy consumption per unit of GDP will be reduced by 20% by 2010. In response to the country’s request for energy saving and emission reduction, in January 2008, Maoming Huanxing Carbon Black Co., Ltd. had reformed the frequency conversion technology, and through actual operation, it was proved that the technical transformation of fan frequency conversion not only has significant energy saving effect, but also has high reliability. The process control is more stable, which plays an important role in reducing the cost of production operations and improving the economic efficiency of the company.

Second, the fan speed control of energy-saving principle of fan is a typical quadratic torque load, its flow, pressure and shaft power of the three basic parameters and speed relationship, after ignoring the wind change factor, the amount of wind is proportional to the speed, The wind pressure is proportional to the rotational speed quadratic and the mechanical shaft power is proportional to the rotational speed cube. It is called the similarity theory of the wind turbine. Therefore, the electric power input by the speed control system also drastically decreases. This is the quadratic torque load in the frequency conversion speed regulation. The basic basis for substantial energy savings.

Fan shaft power calculation formula: Pw = pQ / ~ (1) speed, unit is r/min; - fan air flow, unit is m3 / s; - wind pressure, unit is Pa; one shaft power, fan motor required output Shaft power in kW; fan efficiency.

The wind volume and the wind pressure of the wind pressure fan, in addition to the influence of the structural parameters of the wind turbine itself and the rotational speed, are also affected by factors such as windage resistance, but the relationship between the wind volume and the wind pressure at a certain rotational speed is fixed. That is, when the air pressure at the outlet is high, the air volume is small. As shown, 1,12 curves are two different frequencies corresponding to the speed (ni, n wind-wind pressure curve, it reflects the characteristics of the fan itself, and the wind parameters have nothing to do. Fan system always has its own unique air path, The amount of air flowing through the air duct is related to the capacity of the air blower, and how much wind pressure needs to be determined is only determined by the resistance of the air duct.Ri and R2 are the air volume and pressure loss curves under two different air duct resistances. The intersection point A with the Ri curve is the intersection of the natural operating characteristics of the fan and the natural air duct resistance curve, ie the standard operating point when no adjustment measures are taken.

The air volume adjustment shows that there are two ways to adjust the air volume.

Does not change the fan's operating characteristics, only changes the wind resistance to adjust the air flow installed in the duct throttle device, such as pneumatic control valve, used to adjust the air volume. As the wind resistance increases, the windage curve transitions from R1 to R2, and the working point A moves along curve M1 to point B. The change of the intersection causes the air volume to decrease from Q to Q2, and at the same time, the wind pressure increases from p to P1. Fan Shaft Power Pw The strict BDOG area does not change the air duct resistance, but only changes the fan speed to adjust the air volume fan's operating characteristics as the speed changes. The speed of the fan is changed so that the speed changes, the fan characteristic curve transitions from M1 to M2, and the working point A follows the curve R and moves to point C. The change of the intersection causes the air volume to decrease from Q0 to Q2, and it also causes the wind pressure to decrease from p to p2. Fan Shaft Power: Through the above analysis, if a fan needs to get the same amount of air Q2, adjust the air volume by changing the fan speed. The method of adjusting the air volume is more power saving than changing the air duct resistance. The speed regulation of the fan can be achieved by the variable frequency speed control system.

Third, the technical transformation of the fan frequency conversion speed control system Based on the above motor parameters, Wuxi, Jiangsu is now selected low noise, high performance, multi-function, fan and pump standard series inverter.

The principle of variable frequency electrical control of the tail gas pressurization fan The tail gas pressurization fan is changed from the auto-coupling step-down starting control mode to the frequency conversion speed control mode. The electrical principle of the frequency conversion speed control system is shown.

Exhaust pressure fan motor control process: close the circuit breaker QF, press start button SB2, power L3 phase - 1 line - fuse FU1 - 3 GM general machinery name circuit breaker fuse stop 〖I: button three-phase asynchronous motor by DCS input tuning signal to DCS running status letter! 3-Exhaust gas blower circuit number line - Stop button SB1 Break contact - Line 5 - Start button SB2 Move contact - Line 7 - Relay KA coil - Inverter alarm output contact 30B, 30C (Normal The contact is closed and the contact is open when the alarm is made.) ― The power neutral line is N phase and forms a 220V circuit. The AC relay KA coil is electrically actuated, and a moving contact of the AC relay KA is closed to maintain the working state of the AC relay KA, and the other three moving contacts of the AC relay KA are closed, so that the inverter's forward input signal is input. When the terminals (FWD, CM) are closed, the inverter enters the running working state. At the same time, the motor enters the running working state signal to the distributed control system DCS, and the red signal light is on. The distributed control system DCS outputs the analog current signal (420mA) to the (C1, 11) terminal of the inverter, and adjusts the size of the analog current signal so that the exhaust gas pressurizing fan motor implements the frequency conversion speed regulation work.

Rotate the selector switch SA. The inverter controls the exhaust fan in the cabinet and starts to run. The heat that is dissipated when the inverter is working is discharged outside the cabinet.

Inverter control cabinet and circuit diagram design considerations As the inverter will generate a lot of heat when the work, the inverter control cabinet must install the exhaust fan, and select the cooling fan must be large enough air volume, ventilation path to take the next way out of the work. Otherwise, the inverter will generate a lot of heat when it is working and cannot be discharged outside the cabinet, resulting in over-temperature protection of the inverter. Two 300mmX300mm air inlets are opened in the lower part of the frequency conversion control cabinet door. The control power supply of the two exhaust fan exhaust fans installed in the upper part of the cabinet cannot share the same fuse with the inverter control loop power supply. Because the exhaust fan motor coil is relatively easy to burn, if they share the same fuse, when the inverter is working, the coil of the exhaust fan burns out the short circuit, and the fuse of the control circuit power supply blows to make the inverter control circuit lose power and stop working; When the frequency converter stopped working, the exhaust gas pressure fan motor stopped, and finally, the entire line of the carbon black production line was shut down.

In order to ensure the reliable operation of electrical equipment, electrical components must use quality products that meet the national quality certification.

In addition to complying with national safety technical standards and acceptance specifications, all exposed conductors in the cabinet shall be equipped with insulating sleeves.

Inverter control cabinet installation and precautions Disconnect the old auto-drop starter cabinet and retain the power inlet cable and motor cable.

Place the new inverter control cabinet in place, adjust the level of the cabinet, and weld the cabinet feet with an electric welder.

Connect the input cable, outlet cable, ground cable and control cable of the inverter control cabinet.

Laying a control cable with shield layer from the DCS control room to the inverter control cabinet (cable type: KVVP-2X1.5), used by the DCS to output the analog current signal to control the inverter, and the exhaust gas pressurizing fan motor for frequency conversion. speed.

Yarn, paper, screws, metal shavings, and other foreign objects must not be allowed to fall into the inverter, nor should they be attached to the heat sink to prevent damage to the inverter.

The inverter and control cabinet must be well grounded.

Never connect the power supply to the output terminal of the inverter. Doing so can damage the inverter.

The installation of the inverter control line must be as far away from the exposed live parts of the inverter main circuit as possible, and fixed with a small cable tie.

9 When the inverter is in operation, it will generate many harmonics, which will cause disturbances to the surrounding electrical and instrumentation equipment. Therefore, all electrical and instrument equipments around should be reliably grounded, and the control connection between them should be shielded control cables. The shield should be well grounded.

Parameter setting and debugging of the inverter In addition to installing the wiring, the parameter setting of the inverter is the basic condition for its operation. There are about 200 functional parameters of Fuji inverter for the user to choose to set. In practical applications, it is not necessary to set and debug each parameter one by one. Most of the parameters can be factory set values. However, some of the parameters have a lot to do with actual usage. Therefore, some important parameters must be set and adjusted according to the actual situation, such as acceleration time F07, deceleration time F08, and torque boost F09 electronic thermal relay 1 (action Select F10, action value F11 and thermal time constant F12) and so on.

Acceleration time refers to the time required for the inverter output frequency to rise from OHz to the highest frequency. Deceleration time refers to the time required for the inverter output frequency to fall from the highest frequency to OHz. If the acceleration/deceleration time is set too long, it will affect the production time; if the acceleration/deceleration time is set too short, the inverter output current instantaneous value is greater than the overcurrent detection value, the overcurrent protection function action, the inverter issued "OC1 or OC2" Overcurrent alarm. Or because the motor regenerative current increases, so that the main circuit DC voltage reaches the overvoltage detection value, the protection function action, the inverter issued "OU1, 0U2" over-voltage alarm. According to experience, the method for setting the acceleration and deceleration time for the inverter is to set a longer time first. By starting and stopping the motor, observe whether the inverter has overcurrent and overvoltage alarms, and then gradually shorten the acceleration and deceleration time. With the principle that the motor does not generate alarms during operation, repeat the operation several times to determine the appropriate acceleration and deceleration time.

The torque boost is to compensate for the decrease of the excitation voltage in the low frequency region of the frequency converter, and to enhance the low frequency range V/F characteristics, increase the torque of the motor, and increase the load carrying capacity of the motor. The fan belongs to the quadratic reduction torque characteristic load, that is, with the decrease of the fan speed, the load torque is proportional to the square of the speed. The Fuji inverter design has a special fan, pump load quadratic decline characteristic parameters selection (0.10.9. Electronic thermal relay operating current value is set in accordance with the motor rated current value of 11.1 times the range, the thermal time constant refers to when the thermal relay operating value 150% of the current continuous flow, the electronic thermal relay operating time.

According to Maoming Huanxing Carbon Black Co., Ltd. exhaust gas pressure fan motor parameters, fan operation characteristics and carbon black production process requirements, some of the Fujitsu inverter parameters are set, the inverter parameter settings in Table 1 (only listed and control Process-related parameters, other parameters are factory defaults).

Table 1 Frequency Inverter Parameter Setting Table Code Code Name Setting Range Setting Value Code Code Name Setting Range Setting Value Frequency Setting 1 OL Setting Value Running Operation Thermal Constant Maximum Output Frequency 1 Upper Limit Frequency Acceleration Time 1 Lower Limit Frequency Deceleration Time 1 pole torque boost 1 capacity thermal relay 1 rated current GM general machinery IV. Fan energy saving and operational effects after conversion of frequency conversion technology After conversion of carbon black production line exhaust gas pressure fan, the fan runs at full speed from the original power frequency, using pneumatic butterfly valve The control method for adjusting the air volume and the air pressure of the fan becomes a fully open pneumatic butterfly valve, and the frequency and the air pressure of the fan are adjusted by the frequency modulation and frequency modulation control method of the frequency converter. The energy consumption comparison of the two different control methods is shown in Table 2. Table 2 Comparison of energy consumption before and after the fan's energy-saving modification Valve opening degree Exit pressure Frequency Measured current Measured voltage Before transformation After transformation After transformation, exhaust gas pressure fan Frequency operation (by annual production time 330d, calculated every day 24h, power frequency operation cos furnace production 0.82): After the transformation, the exhaust gas pressure fan operation (in accordance with the annual production time is 330d, 24h per day, frequency conversion operation cos 2 meaning 0.95): U1, U2 - before and after the transformation of the line voltage, the unit is kV; from the above analysis shows that the carbon black production line after the end of the air compressor fan after the transformation of frequency technology, saving about 193,100 yuan per year electricity, energy-saving effect is remarkable . Frequency conversion of a fan, the cost of about 85,000 yuan, running five months to recover the cost of transformation.

The frequency conversion speed control method can not only save a lot of electric energy and reduce the production cost, but also has the following advantages: it can realize the soft start of high-power motor, avoid the impact of high current on the motor and the power grid when the motor starts, and prolong the service life of the motor. .

The frequency conversion speed regulation system is simple and convenient in operation, the output frequency is stable, and the precision is high, which plays an important role in stabilizing the production process.

Improve the power factor and reduce the reactive power loss of the line.

The reduced fan speed results in longer fan impeller and bearing life.

Easy to realize electrical control automation.

Through the above analysis, it can be seen that the application of frequency conversion technology to high-power fans in the production of carbon black not only saves energy and reduces consumption, prolongs the service life of the equipment, but also makes the process control more stable, and the success of the integrated economic and technical frequency technological transformation. In August 2008, Maoming Huanxing Carbon Black Limited Compressed Air Blower (132kW) and Return Fan (55kW) also carried out frequency conversion technology. In September 2009, Maoming Huanxing Carbon Black won a special fund for energy conservation in Guangdong Province. After the transformation of the frequency conversion technology, the fan has been operating well for the past few years. The failure of the fan and the frequency converter has rarely occurred, indicating that the frequency converter has extremely high reliability. In today's world with a shortage of energy, the frequency conversion speed control system is an important equipment for effective energy conservation, and it is worthy of China's carbon black counterparts and other industries to promote the application. In this frequency conversion energy-saving technological transformation project, the control system of the frequency converter belongs to the open-loop control system. In the future, it will be more perfect to change the control system into a closed-loop control system.

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