Application of frequency conversion technology in

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Application of lepang frequency conversion technology in Roots blower of gas furnace in recent years, our factory has adopted frequency conversion speed regulation technology in boiler drum, induced draft fan, induced draft fan of white carbon black, mono pump and feeding grate, and the power saving effect is more than 30%. In april1998, roots blower (L48) of our gas producer × 66wd-2) has been successfully applied to Hitachi j300 frequency converter, which can save energy and increase efficiency significantly

1 introduction to roots blower process of gas producer × 103Pa ≤P2≤5.5 × 104pa, the following undesirable conditions may occur when the return valve SV and the blow off valve ZP are used for regulation:

(1) a large amount of gas is discharged through the ZP valve, wasting energy and polluting the air

(2) the use of return valve SV enables the outlet gas of Roots blower to return to the inlet, doing a lot of useless work and wasting electric energy

(3) the combustion furnace suddenly did not use gas for some reason, while the roots blower was still working, the pressure P2 was rapidly raised, and the blow off valve ZP had no time to react, which caused the desulfurization liquid to leak out and the outlet pressure of Roots blower to rapidly increase, resulting in impeller damage, excessive current, fan fault trip, equipment damage and other failures

(4) when the voltage is unstable, the fan often trips; The fan trips due to the damage of the starter

2 the adopted scheme

adopts variable frequency speed regulation technology to control roots blower, which can eliminate the tripping of blower due to electrical failure without starting device

from the safety point of view, open-loop manual control of frequency conversion is adopted, and the output frequency of frequency converter can be controlled by changing the face plate of the control room to operate potentiometer W, so as to control the fan speed. At the same time, the feedback frequency f is introduced into the face plate of the control room to facilitate observation during operation

(1) cancel the return pipe and do not do a lot of useless work: ZP valve is only used for fault dispersion. The fan speed is controlled by changing the output frequency of the frequency converter, so as to control the fan outlet pressure P2 and reduce the emission waste; The working frequency of the fan is about 39hz, saving a lot of electric energy and gas

(2) P2 > 5.5 when gas is not used for combustion furnace suddenly × 104pa, the output of the frequency converter is automatically reduced to 15Hz (through the action of J4) and the dispersion is turned on at the same time, which protects the roots blower from damage due to the instantaneous high output pressure; The fuzzy logic acceleration and deceleration functions of the frequency converter are adopted, and the best acceleration/deceleration time is automatically calculated according to the motor load and braking requirements, which saves the necessity of test and avoids mistakes; The fault tripping and stopping are recorded for easy cause finding

(3) the AVR function of the frequency converter is adopted. According to the principle of electric drive, the relationship between the output torque of the motor and the output voltage of the frequency converter and the domestic frequency of the white paperboard is m ∝ (v/f) 2. When the voltage of waianyang industry suddenly fluctuates up and down after nearly 60 years of accumulation and cultivation, the CPU in the machine will send out frequency tracking information according to the measured voltage fluctuation signal, so as to maintain the v/f unchanged, that is, the frequency converter maintains the original torque M, maintains the torque balance, and then avoids the frequency converter tripping, so as to make the motor operate normally

3 effect

(1) power saving roots blower (with motor model js- 380V, 90kw), after controlled by frequency conversion technology, the working frequency is about 39hz, and the active power can be calculated according to the measured data. The formula is:

measured current without frequency converter = 145a

measured current after frequency converter is put into operation =94a

1.732iv cos α= one point seven three two × one hundred and forty-five × three hundred and eighty × 0.85=81.12kw (before installation)

=1.732 × ninety-four × three hundred and eighty × 0.85=52.58kw (after installation)

81.12 - 52.58 = 28.54kw, i.e. 28.54kw per hour, with a power saving rate of 28.54 ÷ 90 × 3. for adjusting the speed gear, open the leftmost cabinet door and the reducer cover door on the console. 100%= 31.71%, and the power saving effect is very obvious

according to the actual measured production power consumption, in March of 1998 (30 days as the unit), the power consumption of Roots blower was 58320kwh, and the average hourly power consumption was 81kwh. In July, 1998 (30 days), the power consumption of Roots blower was 36720 kwh, with an average of 51 kwh per hour. It can be calculated that after the fan is controlled by the frequency converter, the power saving rate is 37%, as shown in Table 1. Table 1 power saving benefit analysis table

(2) since ZP valve is used for regulating and dispersing energy saving, the minimum allowance is 0.5%, and the annual allowance for gas is 0.5% × thirteen thousand and five hundred × 2700=182300 m3. After using frequency conversion technology to control the fan, gas waste can be avoided, and the benefits are shown in Table 2. Table 2 power saving and energy saving benefits and analysis table

(3) before using the frequency converter to save mechanical maintenance costs, the roots blower fault trip rate is once every two days. After using the frequency converter, the fan fault trip rate is twice a month. Up to now, the frequency converter has been running safely, in good condition, and the mechanical fault has decreased significantly. The maintenance cost decreased from 35000 yuan in the whole year to 12000 yuan now

4 conclusion

(1) due to the frequency conversion technology, the motor realizes soft start, and there is no starting current impact; It reduces the impact on the fan caused by the instantaneous increase of the fan outlet pressure, thus prolonging the service life of the fan and other equipment

(2) fast return on investment, remarkable power saving, energy saving and efficiency increase. In the future, the energy-saving technical transformation of boiler water supply pump and air compressor should first take the frequency conversion and speed regulation technology into account. (end)

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