I. INTRODUCTION After the reform of the desulfurization system (FGD) in the thermal power plant, in order to overcome the smoke pressure drop caused by the FGD baffle, absorption tower and internal components, a booster fan, desulfurization gas, is required on the original flue gas side of the FGD. The pressure control system controls the speed of the flue gas fed into the FGD system according to the pressure in front of the original flue gas damper by controlling the static leaf diversion angle of the booster fan, so as to ensure that the pressure of the original flue gas baffle plate is stable and adapts to the boiler Load changes. The booster fan is an adjustable blade axial fan.
II. Overview Nayong Power Plant No.2 Large-scale thermal power generation enterprises currently have a total of four 300MW coal-fired power generation units that use wet desulfurization technology to meet the desulfurization and environmental protection requirements. After the boiler flue gas is dedusted by electric dust, it enters the absorption tower through a booster fan and removes SO2 and SO3. After the subsequent series of chemical reactions and technological processes, the flue gas after desulphurization is finally discharged into the atmosphere to reduce environmental pollution. Nayong Plant began to use frequency conversion in 2010 to meet the national requirements of energy-saving emission reduction targets, of which there are 24 auxiliary machines using energy-saving inverter Harvard-type HARSVEST-VA inverter.
Third, the feasibility of the use of fan frequency conversion The operating characteristics of the fan are as follows:
From the above knowledge, the fan speed was adjusted to reduce the air volume, the fan was changed to run at speed N2, the work characteristic was curve 2, the fan was working at point C, and the air flow was still Q2, but the pressure was H2. Compared with B and C, the reduced axial power of the fan is: ΔP=PB-PC=(H3–H2)×Q2. In the case where the windage resistance characteristics are not changed, the wind volume Q, pressure H, and shaft power P of the fan The relationship between the speed N and the speed N satisfies the following relation (similarity theorem): QâˆN, HâˆN2, PâˆN3 Therefore, if the wind speed of the fan is changed by the speed control method, the fan shaft power will decrease when the air volume decreases by half.
HARSVERT-A06/485 high voltage frequency converter principle The frequency conversion device adopts multi-level series technology and consists of phase-shifting transformer, power unit and main controller. The structure and electrical performance of each power unit are completely consistent and interchangeable. The structure of the power unit is a basic AC-DC-AC inverter circuit. The rectifier side is a three-phase full-bridge rectifier circuit. PWM control is performed through an IGBT inverter bridge. The output voltage of a single power unit is obtained by stepping sinusoidal PWM waveforms obtained by recombining and superimposing the waveforms of multiple units. This type of waveform has a good sinusoidal degree and a small dv/dt, which can reduce the damage to the insulation of cables and motors. Output filter; colleagues, the harmonic loss of the motor is greatly reduced, eliminate mechanical vibration, reduce the mechanical stress of the bearing and the blade.
In order to fully ensure the reliability of the system, the following main loop solution is adopted:
This scheme is a typical scheme for automatic bypass. The principle is composed of three high voltage switches QF1, QF2 and QF3 and a high voltage switch QF, motor M (see the left figure). QF2 and QF3 closing circuits are required to have mechanical, electrical, and interlocking logic and cannot be closed at the same time. When the inverter is running, QF3 is turned off and QF1 and QF2 are closed. When power frequency is running, QF1 and QF2 are turned off and QF3 is closed. High-voltage switch QF, motor M is the original equipment on site.
Inverter supporting facilities As the HARSVERT-A06/485 high-voltage inverter is composed of phase-shifting transformers, power units and main controllers. The inverter's efficiency is about 96%, theoretically about 4% of the energy is lost. Among them, the primary equipment transformer and power unit account for the main part. If the control loop is neglected, it can be considered that the two most of the losses are about 50%.
The power of the frequency converter used in this booster fan is 4000KW, which is calculated according to 4% of the rated power. Then the heat output during rated operation: 4000KWx4%=160KW, this heat will be lost in the indoor environment of the inverter. In order to ensure the normal use of the equipment, the heat dissipation problem of the equipment needs to be solved. There are the following methods:
1, natural wind cooling. This method has low investment, high environmental requirements, and is greatly affected by the surrounding environment of the equipment. It is not suitable for on-site use where the dust is large and the air is humid, and it cannot guarantee the long-term stable operation of the equipment.
2, using air conditioning cooling. The air-conditioning environment is good. If the air-conditioning cooling capacity is about 2.5KW/P, this equipment is rated by the rated heat value of 160KW, 160KW÷2.5=64 horsepower. It can be concluded that if air-conditioning cooling is used, the purchase of air-conditioning, as well as the long-term operation of the electricity is very large, and the maintenance costs are high.
Compared with the above two methods, the air-cooled system matching device designed by our company can fully solve the problem.
Air cooling system principle:
As shown in the figure, the high-voltage frequency converter operates in a closed room and a hood is installed on the top of the equipment cabinet. The wind produced by FD-1, FD-2, FD-3, FD-4, FD-5 and FD-6 The tube leads to the heat that is dissipated from the top of the cabinet of the high-voltage converter, and a booster fan is installed outside. After passing through the FD-7 (water cooler) installed in the wall, the cooling air is circulated to the high-voltage inverter room again for the high-voltage inverter. The body is cooled. 
For the use of air conditioners, the cost of cooling is extremely low and investment is not significant. Only need to provide circulating cooling water of FD-7 and a low-voltage motor for circulating the pressure in the air duct. Environmental sanitation, high cooling efficiency, long-term investment, and easy maintenance.
After summarizing the use of high-voltage frequency conversion devices, according to the user's rough statistics, the normal load operation reduces the current by about 50A compared with the industrial frequency operation. Especially at low load operation, the effect is particularly obvious, and the power grid impact and mechanical impact caused by the start of the power frequency are significantly reduced. , Reduce motor maintenance two, save inspection and maintenance costs, while the life of the motor is greatly extended.
II. Overview Nayong Power Plant No.2 Large-scale thermal power generation enterprises currently have a total of four 300MW coal-fired power generation units that use wet desulfurization technology to meet the desulfurization and environmental protection requirements. After the boiler flue gas is dedusted by electric dust, it enters the absorption tower through a booster fan and removes SO2 and SO3. After the subsequent series of chemical reactions and technological processes, the flue gas after desulphurization is finally discharged into the atmosphere to reduce environmental pollution. Nayong Plant began to use frequency conversion in 2010 to meet the national requirements of energy-saving emission reduction targets, of which there are 24 auxiliary machines using energy-saving inverter Harvard-type HARSVEST-VA inverter.
Third, the feasibility of the use of fan frequency conversion The operating characteristics of the fan are as follows:
HARSVERT-A06/485 high voltage frequency converter principle The frequency conversion device adopts multi-level series technology and consists of phase-shifting transformer, power unit and main controller. The structure and electrical performance of each power unit are completely consistent and interchangeable. The structure of the power unit is a basic AC-DC-AC inverter circuit. The rectifier side is a three-phase full-bridge rectifier circuit. PWM control is performed through an IGBT inverter bridge. The output voltage of a single power unit is obtained by stepping sinusoidal PWM waveforms obtained by recombining and superimposing the waveforms of multiple units. This type of waveform has a good sinusoidal degree and a small dv/dt, which can reduce the damage to the insulation of cables and motors. Output filter; colleagues, the harmonic loss of the motor is greatly reduced, eliminate mechanical vibration, reduce the mechanical stress of the bearing and the blade.
In order to fully ensure the reliability of the system, the following main loop solution is adopted:
Inverter supporting facilities As the HARSVERT-A06/485 high-voltage inverter is composed of phase-shifting transformers, power units and main controllers. The inverter's efficiency is about 96%, theoretically about 4% of the energy is lost. Among them, the primary equipment transformer and power unit account for the main part. If the control loop is neglected, it can be considered that the two most of the losses are about 50%.
The power of the frequency converter used in this booster fan is 4000KW, which is calculated according to 4% of the rated power. Then the heat output during rated operation: 4000KWx4%=160KW, this heat will be lost in the indoor environment of the inverter. In order to ensure the normal use of the equipment, the heat dissipation problem of the equipment needs to be solved. There are the following methods:
1, natural wind cooling. This method has low investment, high environmental requirements, and is greatly affected by the surrounding environment of the equipment. It is not suitable for on-site use where the dust is large and the air is humid, and it cannot guarantee the long-term stable operation of the equipment.
2, using air conditioning cooling. The air-conditioning environment is good. If the air-conditioning cooling capacity is about 2.5KW/P, this equipment is rated by the rated heat value of 160KW, 160KW÷2.5=64 horsepower. It can be concluded that if air-conditioning cooling is used, the purchase of air-conditioning, as well as the long-term operation of the electricity is very large, and the maintenance costs are high.
Compared with the above two methods, the air-cooled system matching device designed by our company can fully solve the problem.
Air cooling system principle:
After summarizing the use of high-voltage frequency conversion devices, according to the user's rough statistics, the normal load operation reduces the current by about 50A compared with the industrial frequency operation. Especially at low load operation, the effect is particularly obvious, and the power grid impact and mechanical impact caused by the start of the power frequency are significantly reduced. , Reduce motor maintenance two, save inspection and maintenance costs, while the life of the motor is greatly extended.
Heavy-range of chain conveyors are developed to convey materials like cement, power coal, gypsum, potash, crushed chalk and lime type of products where material is moderately abrasive and flow able.
Forged, hardened chain links with welded crossbars are used to convey materials which run on manganese wear rail.
Conveyor casings and bolt holes are cut using CNC laser machines and folded. The conveyor is off fabricated construction with bottom, side and covers plates are fitted with butt straps for easy removal.
Chain conveyors can be situated in a horizontal, inclined, or in vertical arrangement. Conveyor`s bottom and side panels are made off 5mm folded sheets with 3mm top cover. Drive and tail units are fitted with flanged bearing housings with seals in standard design and Plummer bearing housing is available as an option.
They have special designed easy removable type split sprockets for tail and head end assembly.
Tail end comes with adjustable screw take up with spring washers. Dust tight and high temperature conveyors are available on request.
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Quantum Conveying Systems Yangzhou Co.,Ltd. , https://www.fkconveyor.com