Botou City Nuohe Environmental Protection Equipment Co., Ltd. is aimed at the characteristics of circulating fluidized bed boiler flue gas. The design of this electric precipitator has been further improved and improved on the basis of the conventional electrostatic precipitator structure technology. Boiler Electrostatic Precipitator Reconstruction Program Botou City Nuohe Environmental Protection Equipment Co., Ltd. is aimed at the characteristics of circulating fluidized bed boiler flue gas. The design of this electric precipitator has been further improved and improved on the basis of the conventional ESP structure technology.
(1) Electrostatic precipitator modification - support A fixed support, six one-way movable supports and five multi-directional movable supports are arranged between the dust collector and the steel structure foundation. The role of the fixed support is to achieve a reliable fixation of the dust collector and the foundation, and the movable support effectively eliminates the adverse effects of the thermal expansion stress on the foundation. The support is mainly made of high quality carbon steel.
(2) housing
The shell is the main steel structure of the electrostatic precipitator. It is a frame-type integral box structure composed of steel and steel plates. It is mainly composed of the bottom beam, the inner and outer roofs, the column, the side plates and the inlet and outlet end seals. . It is subjected to body weight, wind load, snow load, seismic load and electric field load. In order to ensure the reliability of the structure, according to the force analysis program of the dust collector, the computer is used to optimize the design to ensure that the structure is not deformed when the positive and negative pressure is 6000 Pa, ensuring reliable strength and rigidity. The material of the housing is Q235B. The housing is all continuously sealed.
(1) The inlet of the precipitator should be equipped with a perforated plate or other form of flow equalization device so that the flue gas flows evenly through the electric field.
(2) The shell should be sealed, rainproof, and the shell design should avoid dead corners or dust accumulation areas. The dust collector should be equipped with an overhaul ladder every electric field.
(3) Each electric field of the precipitator shall be fitted with a manhole door and a passage. There should be manholes on the top of the precipitator to overhaul the electrode suspension system. The diameter of the circular manhole door should be at least φ600mm, and the minimum diameter of the rectangular manhole door should be 0.45m×0.80m. All people have an insulated double-layer design with a hinged, sturdy outer door.
(4) The outer casing should fully consider the expansion requirements. The thickness of the outer casing iron plate is 5mm, and the measured thickness is ≥4.75mm.
(5) The insulator compartment must be equipped with a heating device.
(6) All platforms shall be provided with railings and retaining edges. The inner layer of the electric dust-removing top shall be an integral sealing structure, the outer layer shall be a sloping roof, and the interlayer shall be insulated.
(7) The escalator should be able to meet the working surface of each platform and that needs to be repaired and operated. The escalator load should be 2000N/m2.
(8) The base of the equipment shall take into account the effect of seismic acceleration on it.
(3) The ash hopper is provided with a four-inch cone ash bucket at the lower part of the electric field.
1 In order to ensure the free flow of ash, the minimum inclination angle of the ash wall and the horizontal plane is greater than 65°, and the four intersecting angles are attached to the circular arc plate.
2 In order to prevent condensation in the ash bucket, an electric heating device is arranged on the outer wall to ensure that the lower part of the ash bucket does not condense or shed.
3 The lower part of the ash hopper has a manhole door. The manhole door is flexible, convenient and has good sealing.
4 The ash bucket is set up and down, and outputs high and low level control signals. The level gauge can meet the requirements of long-term operation in the hopper.
5 ash bucket volume guarantees 8 hours of unloading ash and not full of ash.
6 Dust collector ash bucket number: 1 , an electric field set a ash bucket.
7 ash sloping wall shall be equipped with silo wall vibrators, one for each ash bucket.
(4) The inlet and outlet of the inlet and outlet are adopting the flat-in and flat-out type (can be designed according to user requirements).
(5) The air distribution plate of the air inlet ensures the uniformity of the airflow: the uniformity of the airflow distribution is a reliable measure to improve the dust collection efficiency. The dust collector has two layers of flow-blocking and diversion flow distribution plates in the inlet head. The orifice plate is a circular orifice plate with a diameter of Ф50~Ф80, and the opening ratio of the first layer distribution plate is 45%. The second layer distribution plate then sets different opening ratios according to the distribution of the airflow, so that the airflow distribution is uniform. The circular orifice plate has a hem on both sides, which has both a diversion effect and an increase in the rigidity of the distribution plate. On this basis, the triangular baffle is arranged at the appropriate part of the circular orifice plate, which not only ensures the uniformity of the air distribution, but also functions as a mechanical louver type dust collector, pre-preparing the coarse particle dust entering the head. Dust removal, the dust removed goes into the ash bucket under the electric field. The use of the flow-blocking and diversion flow distribution plate ensures that the index of uniformity of the airflow distribution reaches σ ≤ 0.25 (relative root mean square coefficient).
(6) The dust remaining in the flue gas discharged from the air outlet through the electric field is mostly fine-grained charged dust, which is adsorbed by the trough plate at the trough plate, after being consolidated It is shattered and removed to improve dust removal efficiency, and the presence of the grooved plate is also advantageous for uniformity of airflow distribution.
(7) Extremely matched form: The anode plate of the electrostatic precipitator adopts 480C type anode plate, and the cathode line adopts modified BS thorn line.
480C type anode plate, the surface of the plate is grooved, making it easy to absorb dust. The folded edges on both sides not only increase the rigidity of the plate, but also prevent the dust from flying twice as a windbreak. The rapping acceleration is well transmitted and easy to clean. The weight of the unit dust collection area is light, and the deformation resistance is strong under the action of high temperature and rapping. Because of its reasonable structure and outstanding advantages, it is the most widely used electrode plate. The electrode separator for circulating fluidized bed boilers should also be used.
The choice of corona wire is crucial. The four requirements of the electrostatic precipitator for corona wire:
(1) Wide range of adaptive specific resistance.
(2) Adapt to high dust content.
(3) When the polar line is discharged, the electric wind is strong, and the discharge point is not sticky.
(4) The interval between inspections is long.
There are two basic requirements: one is firm and reliable, and the other is good electrical performance.
The new BS thorn line produced by our company basically has the above conditions. At present, the common "RS" line in China has the advantages of sturdy and durable, continuous line, low halo voltage, strong discharge and high current density, but the current density is not uniform enough. The effective dust collection area is reduced, that is, the effective utilization of the anode plate is lowered, which is a disadvantage of the pole line.
The company has been looking for a new type of cathode line that retains the advantages of the original "RS" line while overcoming its shortcomings. In order to be applied to actual industrial production, especially in recent years, the flue gas working conditions have changed greatly, and it is necessary to develop suitable specific working conditions. After several years of development, the company launched the "BS" line, which eliminates the polar line. The "dead zone" with zero current density on the pole plate of the original "RS" line, the new pole line has reached the average current density of σr = 0.4, which improves the effective utilization of the anode plate and prevents back corona. Obviously, the "BS" line mainly relies on the tip discharge of the thorn, and has a very strong electric wind. Under the condition of high dust content, corona sealing will not occur, and the operating voltage can be maintained ≥55KV in actual operation, thus ensuring Efficient operation of the electrostatic precipitator.
The improved BS thorn wire has a relatively uniform line current and a large corona current, which can promote the further diffusion of the charged dust, thereby preventing corona sealing, and improving the dust collecting efficiency when the dust concentration is high.
The improved BS thorn line discharges the tip of the thorn, has a strong electric wind, and does not cause corona closure when the dust content is high.
The improved BS spur line has a high operating voltage because of its uniform line current. For the anti-corona phenomenon which is higher in specific resistance, smaller in dust particle size and more viscous dust, it shows obvious suppression effect.
The BS type thorn line has a structural form with high strength and good rigidity. Under the design conditions, it can be operated for more than 8 years for a long time to ensure that the electric precipitator can operate safely and reliably.
(1) Deformation such as bending and torsion before and after installation shall comply with the relevant standards.
(2) All anode plates and cathode wire frames shall be vertically mounted and shall be protected against swings.
(3) The oil-immersed transformer placed on the top of the precipitator shall specify the data of the transformer manufacturer and capacity in the technical tender.
(4) Noise control: The maximum noise field level during operation of the rapping device and the ash rapper shall not exceed 85 decibels at a distance of 1 m from the outer surface of the device.
(5) The material of the anode plate is SPCC, the thickness should not be less than 1.2mm, the actual measurement is ≥1.2mm; the pole line requirement is the overall tubular RS thorn line, the material is SPCC, the pole line skeleton thickness is ≥1.2mm, the thorn thickness is 0.8MM, single Root line length ≤ 3.5M;
(6) The internal cathode frame structure of the dust collector, the outer support and the reinforcement frame are 80mm×80mm square tubes, and the small box size is 40mm×60mm square tube (7) The cathode requires double side side rapping, and the anode side side is rapping (8) The anode rapping device adopts a method in which the side of the cathode side is oscillated by the side of the arm and the side of the anode is oscillated by the arm.
Because the rapping pole line, the purpose of the pole plate is to clean the dust adsorbed on the board and the line by rapping, which is beneficial to the normal operation of corona discharge and plate dust collection.
According to the operating experience of domestic electrostatic precipitators for more than 20 years, and the relatively high viscosity of China's coal-fired dust, the anode system is swayed by the lateral slewing arm and the cathode system is swayed by the side slewing arm. .
1Anode system side deflection arm rotary hammer is swayed in the lower part of the electric field. Each row of plates is provided with a rapping point. The plate is suspended from the upper part, the lower part is free, the rapping point is set at the lower free end, and the anode plate is suspended after being long. The plate has good rigidity in the tangential direction, and the transmission of the side rapping force is transmitted to each part through the direction of the tangential rigidity of the plate, and the force transmission is uniform. Because the transmission mode is good, only a small impact force is needed. Effective ash can be achieved. The slamming hammer is a rotating structure, and since the force is small, deformation does not occur substantially, and the contact point of each rapping can be changed to ensure long-term use and sufficient swaying force.
Side vibrating Because the airflow passes through the distribution plate, the ash on the upper and lower plates is basically uniform, the dust particles in the lower part are slightly thicker, the lower acceleration is slightly larger during the rapping, and even if the dust is crushed in the lower part, the particles are coarser and the ash is deposited. The block falls, so the second flying is less, and the cross-sectional shape of the anode plate can prevent the second flying.
2 Cathodic system side jib hammer tangential oscillating Due to the cathode line, there is little ash accumulation, so only a small rapping force can meet the requirements of cleaning, and the cathode rapping is the side rapping of the rotating weight. In order to facilitate the repair of the rapping device, the rapping device is arranged at the top of each power supply zone, and the force is transmitted to the middle and the lower part of the cathode wire through the pin and the toothed disk drive respectively to ensure that the cathode system has sufficient rapping force. Make the rapping force uniform to facilitate cleaning.
In order to prevent the hammer from falling off, the hammer head and the hammer handle are riveted by the rotary riveting machine through the high-strength rivet steel pin shaft, which has high strength and long service life.
In order to make the rapping mechanism safe and reliable, a safety protection pin is provided.
In order to prevent condensation in the porcelain shaft box, an electric heating device is arranged in each porcelain shaft box.
The rapping shaft adopts the same anti-smashing shaft and card shaft structure measures as the vibrating plate of the dust collecting plate.
The power transmission of the anode rapping device is realized by the reducer, the vibrating shaft, the dust bearing, the vibrating hammer, etc., and the gear coupling and the universal joint coupling are connected between the reducer and the shaft for digesting each The amount of thermal expansion and installation error of the segment axis also eliminates the adverse effects caused by the misalignment of the shaft. The pin coupling also acts as an overload protection.
Each of the vibrating shafts is provided with one fixed and movable dust bearing, which can effectively prevent the boring phenomenon. The vibrating hammer material is made of 45 high-quality carbon structural steel, and the surface is quenched to improve the hardness and wear resistance.
(9) The internal baffle of the electric field is provided with a flue gas choke plate in the ash hopper of the electric field, so that the flue gas effectively passes through the electric field, thereby improving the dust removal efficiency.
(10) High and low voltage power supply and control high voltage power supply are provided by professional power supply manufacturers, including rectifier transformers, high voltage isolation switches, high voltage control cabinets and other parts.
The rectifier transformer is installed outdoors. The transformer is designed with high impedance, oil immersed and self-cooled, and equipped with gas relay protection. The transformer is installed on the top of the electrostatic precipitator, the primary side is connected from the control room via an ordinary cable, and the secondary side directly enters the electric field after passing through the high voltage isolation switchgear cabinet.
(3) When the transformer oil temperature and dangerous gas alarm transformer oil temperature exceeds the set alarm value, or the explosive gas in the precipitator exceeds the alarm value, the output current and voltage will automatically drop to zero. When the oil temperature exceeds the alarm value, the display flashes: “TEMPâ€; when the dangerous gas exceeds the standard, the display flashes: “GASâ€. ​​When the above fault is eliminated, the output current voltage is automatically restored. When the transformer oil temperature exceeds the set limit value, it trips and alarms.
The configuration of the low-altitude cabinet can realize the following functions: automatic with anode and anode (arbitrary setting of time interval, arbitrary arrangement of form), manual vibrating function; material level detection alarm display: when the gray level reaches high level, it should be displayed in time. Sound and light alarm; ash bucket heating automatic, manual constant temperature control function, electric heating fault detection and alarm; inlet and outlet air temperature detection and display; insulation barrel electric heating automatic, manual constant temperature control, electric heater fault detection and alarm; Motor operation and stop indication signal, electric heater input and cut-off indication signal; motor power "target=_blank> machine cable fault detection and alarm, hold and reset after fault.
Dust collector body lighting: Microcomputer time control switch, the switch is installed in the power distribution board.
(11) Other dust collectors have internal walking platforms for easy installation and maintenance. There are ladders, platforms and railings on the outside; the outer layer of the outer casing is provided with insulation layer, and the exterior is protected by corrugated steel sheets to increase the appearance.
(1) The main body of the precipitator is insulated with 100mm rock wool, the ash bucket is insulated with 100mm rock wool, the manhole door is double-layered and the outer layer needs to be insulated; the electric dust removal heating and insulation method is steam heating and heat preservation;
(2) The color of the insulation corrugated board is sky blue and the thickness is 0.7mm;
(3) All open-air metal components shall be painted and anti-corrosive, and the paint shall be made of Lehua brand anti-corrosive paint.
(4) The service life of the equipment is 20 years, and the overhaul period is required to be more than 5 years.
(12) Technical guarantee measures According to the design specifications, the shell design pressure is ± 7000Pa, which puts high requirements on the structure and strength of the dust collector. Many years of experience in the design and manufacture of electrostatic precipitators tell us that the electrostatic precipitator is below Several aspects are very prone to problems, namely:
A. The strength design is not enough, causing the dust collector to collapse.
B. The airflow is unevenly distributed, which reduces the dust removal efficiency.
C. Insulation measures are unfavorable, condensation, ash clogging.
D, the structural design is unreasonable, the wear is intensified and the hammer is broken; the broken pole phenomenon occurs, and the rapping failure occurs.
E. The sealing structure is unreasonable, resulting in too much air leakage rate, causing condensation and water ingress.
To this end, we mainly take the following measures in the design process:
1. Design and selection technology Our company has domestic first-class electric precipitator design team and design ability. After years of design and selection experience, based on a large number of actual operating parameters and experimental data, we have established a computer automatic selection. system. The electrostatic precipitator can be selected according to different requirements, and the main design technical parameters are given. According to the selection result, steel structure design load specification, external force load and other conditions, the overall strength calculation of the dust collector is carried out, and a calculation report is given to guide the design work.
2, excellent performance of the extreme configuration form (1) For the above characteristics of smoke, our company in the design of electrostatic precipitator technology program, the polar form of the serious research and repeated argumentation. From a large number of comparison tests of various types of cathode lines at home and abroad, a cathode line configuration type that is most suitable for this project and can effectively ensure long-term, safe, reliable and efficient operation of the electrostatic precipitator is selected.
(2), the dust collecting plate adopts the commonly used C type 480 plate in China. One of the characteristics of domestic coal-burning dust is micro-viscosity, which requires a large rapping force. The C-type plate has good rigidity and good vibration transmission performance, which can minimize the dead angle of cleaning.
4. Advanced air distribution device to ensure uniform air distribution. Our company has fully integrated the advanced airflow distribution technology at home and abroad to develop a unique flue gas flow guiding device and air distribution technology in the air inlet box. Among the equipment provided by our company, the guaranteed deviation of the flue gas volume distribution deviation of the electrostatic precipitator intake smoke box is <1%.
5. The internal rotating parts adopt wear-resistant design. Our company fully considers the characteristics of the circulating fluidized bed boiler, and wears the internal transmission parts such as fixed bearing seat and vibrating hammer to ensure the service life of the electrostatic precipitator and reduce maintenance. The labor intensity of the personnel.
The fixed bearing seat adopts the latest type of wear-resistant bearing, which is characterized in that the supporting transmission bushing structure is rolling type, the transmission contact is designed to be in line contact, the contact wear is reduced, and the inclined surface is formed at both ends of the sleeve, so the rapping The rotating contact surface of the shaft is not easy to accumulate during operation, thereby reducing wear. All bearing pairs use a new type of wear-resistant material, which greatly improves the wear resistance of the rotating parts. At least one overhaul can be guaranteed without the need to replace the wear parts. The new structure reduces the operation and maintenance requirements, the reliability of the operation is greatly improved, and the labor intensity of the maintenance personnel is greatly reduced. It has been widely used in electric precipitators in recent years and has been well received by users.
6. New sealing structure, minimizing air leakage According to the boiler's own flue gas volume and body air leakage rate, the control is ≤ 2.%. We use our company's original new double-layer sealing manhole on the hole door of this project. The door has a remarkable effect. The sealing strip is made of high temperature resistant glass fiber rubber sealing strip; the sealing of the perforation of the vibrating shaft is made of silicone rubber seal; the top is sealed by three layers; all the sealing joints are double-sided welded; the electrostatic precipitator is used for overall insulation and the welding quality is strictly required. It is necessary to ensure the double-sided welds in the sealed joints, to ensure the weld height, and to strictly control the installation during the installation, and require the installation unit to carefully construct, especially to seal welding, in order to minimize the leakage. Finally, the air leakage rate of the whole machine body is ≤2.0%, to meet the requirements of the project for the air leakage rate of the electrostatic precipitator.
7. Rapping force and rapping system (1) Reasonable vibratory force Based on a large number of tests and actual running rapping data, our company fully considers the three major factors of rapping acceleration, rapping frequency and amplitude. The cleaning effect of the plate and the pole line establishes a reasonable rapping force, and takes necessary measures on the structure to make the rapping force as uniform as possible, and to maintain effective cleaning without causing secondary dust. Specifically, in the design of the rapping transmission mechanism, the wear of the movable parts under the dust condition is taken into consideration, and the influence on the reliability of the equipment caused by the thermal expansion and contraction and the error in the installation and construction is taken into consideration; Effectively clean the dust without causing excessive vibration to cause secondary dust. The rapping force is suitable, the rapping device is flexible, the hammering position is accurate, and the rapping parts are wear-resistant, corrosion-resistant and impact-resistant. The final rapping force causes the dust deposited on the plates to slide down to the ash bucket.
(2) Reasonable rejuvenation system Considering the requirements of boiler dust cleaning characteristics, it is very important to choose a reasonable rapping system and to maximize the removal of the polar line and the ash accumulation of the plates without secondary flying. The internal flue gas flow rate of the electrostatic precipitator is higher than the lower part. Before the electric field is higher than the electric field, the viscosity electric field is larger than the electric field. These characteristics determine that the rapping period of the electric field needs to be adjusted, and the optimal rapping period is selected. Each row of anode plates and cathode lines are staggered and vortexed to ensure that the electrode plate of the electric field reaches a suitable thickness, and then the coring is cleaned, so that the accumulated ash on the plate falls down in a sheet shape, reducing the secondary flying. For the best cleaning effect.
8. Continuously improved technology, safe and reliable operation measures When the electrostatic precipitator is actually running, the most common problem is “cathode line disconnection, rapping failure, ash cloggingâ€, commonly known as “three major faults†in the operation of electrostatic precipitators. . How to prevent the occurrence of "three major failures" and improve the reliability of the actual operation of the electrostatic precipitator is the goal that our company is striving for. In recent years, our company has continuously introduced, absorbed and learned from the advanced technology of electric precipitators at home and abroad, and always maintains the advanced nature of our company's electrostatic precipitators. In response to the above "three major failures", our corresponding measures are:
(1) The connecting plates at both ends of the thorn line are made of thick-walled tubes. Through multi-point riveting, it can effectively prevent the broken line caused by fatigue and avoid the needle drop.
(2) The hammer head and the hammer arm adopt a riveted structure, which improves the reliability and service life of the rapping.
In the past, the axial displacement and installation error caused by thermal expansion of the conventional electrostatic precipitator often caused the shaft of the rapping drive shaft to be misaligned, which caused the rapping center to be misaligned, which seriously affected the rapping effect. In order to completely change this situation, our company has improved the past rigid joint whole shaft into a plurality of unit shafts, and the unit shafts are connected with a “soft†coupling by a pin coupling, each unit shaft has its own fixed bearing and sliding. Bearings, in this way, each unit shaft system digests the thermal expansion displacement by itself, effectively solving the phenomenon of the card shaft and the boring shaft, eliminating the cause of the failure of the swaying, and improving the reliability of the swaying.
In addition, our unique fixed bearing structure adds a limit stop to the bearing pair, effectively avoiding the boring phenomenon.
The lower part of the anode plate row is provided with a limiting plate to prevent the plate row from swinging and can ensure that the suspension center and the rapping center of each row of anode plates remain unchanged, thereby ensuring the reliability of the rapping.
The only innovation we have made on the structure of the electrostatic precipitator is to prevent the failure of the rapping and improve the reliability of the rapping of the electrostatic precipitator. After years of actual operation, it proved to be effective.
(3) To ensure smooth discharge of ash ash A. In order to ensure smooth ash discharge of the ash hopper, the ash bucket inclination angle of our company's electrostatic precipitator is >65°, and the inner side of the adjacent wall panel is provided with an arc plate with a radius of 200mm. Eliminate dead ends to ensure all dust is free to flow.
B. Good heating and heat preservation to prevent clogging caused by condensation and ash formation. The ash bucket is designed with steam heating device, and the heating surface is evenly distributed on the surface of not less than 1/3 of the lower part of the ash bucket. The air medium is used for heat conduction, which has a good heating effect and makes the ash have good fluidity. This structure can reduce the number of routine maintenance and effectively improve the thermal efficiency. The heating power of each side of the ash bucket is not less than 2500 watts; the interior of the ash bucket reaches at least 120 °C under the minimum ambient temperature and the arbitrary load of the boiler. The outer wall of the ash bucket is provided with a sufficiently thick insulation material.
C. Each ash bucket is provided with an artificial vibrating anvil, which protrudes in the horizontal direction from the outer edge of the ash bucket reinforcement rib. If necessary, it can be manually vibrated to prevent the ash flow in the ash bucket from sticking or ashing as soon as possible. unobstructed.
9. Advanced and reliable electrical equipment Electrostatic precipitator is an electromechanical "target=_blank> mechatronics product. Reliable body equipment is only one aspect of long-term efficient and reliable operation of electrostatic precipitator. Only electronic control equipment also has excellent performance and The quality and complete control function can make the electrostatic precipitator a perfect and excellent product.
The microcomputer-controlled high-voltage power supply device provided by our company has a variety of operating modes, which can be selected for operation under different working conditions.
(1) Spark tracking mode (2) Intermittent pulse power supply mode.
(3) The best working point detection operation mode.
(4) Power tracking mode.
(5) Voltage tracking method.
It has the functions of arc, short circuit, undervoltage and overcurrent, open circuit and partial excitation, and adapts to the changing characteristics of electric field.
Not limited to the above functions. The method of spark detection, judgment and processing is to determine the occurrence of spark by indirect detection of secondary current, secondary voltage value. Treatment methods: rectification control, peak tracking control, intermittent power supply control, and phase recovery control.
These features allow the electrostatic precipitator to operate with stable, reliable operating parameters for optimum dust removal efficiency. Http://news.chinawj.com.cn
Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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