Determination of main design parameters of high temperature flue gas electrostatic precipitator for large copper smelting converter

I. Overview

In large copper smelters, matte is converted to blister copper by converter. During the blowing process, a large amount of flue gas is generated, and after the dust is removed, it is sent to the acid production section to produce sulfuric acid. Since the acid-making equipment has strict requirements on the dust concentration of the flue gas, the dust-removing effect of the electric precipitator has a great influence on the normal production of the acid-making process. In addition, the electrostatic precipitator also recovered a large number of valuable gold dust in the genus, improve the overall recovery of the plant, improving economic efficiency, protection of the environment has a very important role.

Because the temperature of the converter flue gas entering the electric precipitator is high, the gas pulsation fluctuates greatly, the dust concentration is high, the specific resistance is large, and the dust concentration of the outlet flue gas is low, which puts forward the design of the electric precipitator. Very high demand. After the actual investigation and research on the production of converter dust collectors in many domestic copper smelters, and based on the advanced technology of the introduction of converter electric dust collectors and the latest domestic research results, the author designed a horizontal double room. High-temperature flue gas electrostatic precipitator for five-electric field copper-making converter. This paper discusses the design parameters, main technical improvement measures and some main features of the high temperature flue gas electrostatic precipitator for copper converters.

Second, the main design parameters

Handling of flue gas: 68500Nm ³ /h

Flue gas temperature: 350 ~ 380 ° C

Flue gas dew point temperature: about 190 ° C

Inlet smoke pressure: -1000~-2000Pa

Inlet smoke dust content: 30g/Nm ³

Export flue gas dust requirements: <0.5g/Nm ³

Soot bulk density: 1 ~ 1.2t / m ³

Soot true density: 4.2t/m ³

The main components of smoke and soot are shown in Table 1 and Table 2.

Table 1 Main components of flue gas V%

Table 2 Main components of soot W%

Third, the characteristics of converter blowing process and the impact of flue gas and smoke on the electrostatic precipitator

The converter blows the iron in the copper crucible into the slag, and the elements such as Pb, Zn, As, and S are oxidized into the flue gas, and elements such as precious metals enter the blister copper. At the same time, the blowing process is intermittent, and the air supply volume during the slag making period and the copper making period is also different, which has many adverse effects on the electric precipitator:

(1) The dew point temperature of SO ₂ in the flue gas is high, and the fluctuation of the flue gas volume causes the flue gas to be easily dew condensation, corrodes the equipment, and affects the increase of the secondary voltage, thereby affecting the dust collection efficiency.

(2) The dust concentration of the flue gas is high, the specific resistance of Pb and Zn is high, and the dust of the dust collecting pole is not easy to be shaken down, the corona current is reduced, and the dust collecting efficiency is affected.

Fourth, the determination of the main technical parameters

(1) Electric field breaking area (A) and electric field wind speed (V)

The electric field breaking area depends on the amount of flue gas and the wind speed of the electric field.

High electric field wind speed will cause secondary flying, reduce dust collection efficiency, low electric field wind speed requires large electric field breaking area, and uneven distribution of flue gas along the cross section, so that the plate is wasted. Therefore, the electric field wind speed needs to be comprehensively considered to determine a better design value. After investigation and research combined with production practice, on the one hand, due to the high temperature of the converter flue gas, the smoke has an upward trend. On the other hand, due to the large proportion of soot, the dust has a downward trend. Considering the design, the electric field wind speed is 0.54m/s. .

According to A = Q / V, the electric field sectional area was determined to be 84 m ² . (where Q is the amount of smoke.)

According to the electric field sectional area, the double chamber is used, and the electric field breaking area per chamber is 42 m ² .

(two) pole spacing

In the past, due to the limitation of the high-voltage silicon rectifier power supply, the pole pitch was mostly narrow-pole pitch. After the 1970s, domestic and foreign experimental studies have shown that increasing the pole spacing can increase the insulation distance and increase the working voltage of the pole spacing, which can increase the ion drive speed of the dust, thus reducing the dust collecting plate area of ​​the electrostatic precipitator. , reduce equipment costs. Production practice shows that the pole spacing S of the converter high-temperature flue gas electrostatic precipitator should be 400-600mm. Due to the high temperature of the converter flue gas and the large selection of the pole spacing, the working voltage also increases. At present, the quartz sleeve material for hanging cannot withstand the excessive voltage under high temperature conditions. In addition, after the pole spacing is increased, the hot air hoisted by the cleaning cathode is also increased, thereby increasing the leakage of hot air into the electric field and reducing the concentration of SO ₂ in the flue gas, which is disadvantageous for the subsequent process of acid production. Therefore, it is determined in this design that a pole pitch of 400 mm is used.

(3) Ion drive speed of dust (W)

Ion drive speed is related to many factors, such as polar configuration, electric field strength, dust concentration, flue gas properties, soot characteristics, dust particle size, flue gas temperature, temperature, pole spacing, dust specific resistance, and the like. It is difficult to quantitatively calculate the ion drive speed. The analogy method is generally used in engineering. The analogy is calculated based on the ion drive speed of a similar smoke dust collector operating under operating conditions:

W=K×(d/d ₀ )×W ₀

In the formula: W is the dust ion driving speed of the designed electrostatic precipitator, cm/s; d is the design of the pole distance of the electric precipitator, mm; W ₀ is the dust ion drive of the electric precipitator in the working condition The inlet speed, cm/s; d ₀ is the pole distance of the electric precipitator in the working condition, mm; K is the speed coefficient that affects the dust ion drive.

The dust ion driving speed is an important parameter for comparing and evaluating the performance of the electric precipitator, and is also an important parameter for the design of the electric precipitator. If the dust ion driving speed is too large, the electric dust collector cannot meet the production requirements, and the dust in the outlet can not meet the design requirements; if the value is too small, the electric dust collector is insufficiently loaded, resulting in waste of equipment. This design adopts the analogy calculation with the introduction of the converter electric precipitator, and the W is 0.037m/s in combination with the actual operation analysis.

(4) Spacing line spacing (L)

The spacing of the corona wire of the electric precipitator has a direct influence on the dust collection efficiency. If the distance of the corona wire is too small, the unit current value of the wire will be reduced due to the electric shielding effect; if the current value is too large, the current density will be lowered to make the dust collection. The efficiency is declining. Based on actual experience, the spacing of the corona wires is determined to be 300 mm.

V. Main technical improvement measures

Whether an electric precipitator can achieve the expected dust collection effect is not only related to whether the parameters of the electric precipitator are reasonable, but also related to whether the mechanism design is reasonable. The reasonable structure can make the electric dust collector finally achieve high dust collection efficiency, low investment, energy saving, safety and reliability, and convenient operation and maintenance. The following technical improvements have been taken in this design.

(1) Measures to prevent condensation of smoke

Air leakage from a vacuum operated vacuum cleaner is a common problem. If the high temperature flue gas dust collector of the converter leaks into the cold air, it will increase the gas volume, reduce the SO2 concentration of the flue gas, affect the acid production, and reduce the temperature of the flue gas, causing condensation, corrosion of the device, and even creepage and short circuit. In order to reduce the efficiency of dust collection, strict air leakage prevention measures are adopted in the design: (1) A new type of electric heater and hot air cleaning device is added to the quartz sleeve and quartz pot packing sealing device of the cathode suspension. . At the same time, the sealing of the cathode vibrating shaft and the difficulty of solving the insulation of the rapping shaft due to the high temperature of the flue gas effectively prevent the occurrence of creepage and short distance. (2) The electric precipitator adopts double-layer closed-hole entrance door with all-steel structure; at the same time, the overall boat-shaped ash hopper is used to reduce the number of discharge openings and reduce the air leakage point. This greatly reduces the air leakage rate of the device. (3) Increase the insulation layer of the casing from 100mm to 150mm to reduce the temperature drop of the flue gas in the electric precipitator and prevent condensation of the flue gas.

(2) Effective and effective resilience measures

According to the analysis of the production practice, different rapping measures were taken for the dust collection, corona pole, ash bucket, and diverter plate, and the adjustable rapping frequency was improved.

(3) Advanced and reasonable matching measures

In this design, five electric fields are used with large C-shaped plates. Since the dust concentration of the converter flue gas inlet is large, and the particle size of the soot in the first, second, and third electric fields is relatively large, the first, second, and third electric fields need to be charged as much as possible to generate a large amount of electricity. Corona current. For this design, an improved tubular thorn line capable of generating a relatively strong dust end discharge is selected, and the degree and rigidity of the cathode level are good, and it is suitable for use in high temperature flue gas and has a long service life. After the flue gas is collected by the first, second, and third electric fields, the dust particles entering the fourth and fifth electric fields are fine in particle size, and the dust content of the flue gas is also small. In order to improve the ion driving speed of the soot, the fourth and fifth electric fields select a star corona wire which can increase the operating voltage between the poles, so as to increase the electric field strength and accelerate the transportation of the charged dust to the dust collecting set, thereby improving the dust collecting efficiency. Achieve the best dust collection effect.

(4) Advanced low-voltage control system

In this design, the low-voltage control device of the electric precipitator uses a programmable controller for automatic control. It consists of a controller, a power box, an analog display, etc., and can perform real-time measurement and control of the hot air temperature of the electric precipitator and implement time control and logic control of the rapping device and the ash discharging device, and has a function of fault alarm, etc., which can ensure The electrostatic precipitator operates safely and reliably.

Sixth, the main features of this design electric dust collector

(1) Negative pressure operation is adopted to prevent smoke from escaping, especially to prevent SO2 from polluting the environment.

(2) The air inlet box is horn-shaped, and a flue gas deflector with adjustable horizontal and vertical directions is arranged at the inlet of the flue gas. At the same time, a 3-layer air flow distribution orifice plate is set, and a gas flow distribution test is required to enter The flue gas in the electric field is evenly distributed along the section.

(3) An electrostatic separation trough plate is arranged in the air outlet box to further deposit the fine charged dust discharged from the electric precipitator to reduce dust at the outlet.

(4) The ash discharge is driven by a buried scraper and sealed with a star-shaped rotary valve to reduce air leakage. At the same time, a herringbone plate is arranged in the boat-shaped ash hopper to make the dust fall evenly distributed in the squeegee conveyor, thereby ensuring the normal operation of the buried squeegee conveyor.

(5) A baffle plate is arranged between the electric fields to ensure that the flue gas does not generate a short circuit and reduce the dust collecting efficiency.

Seven, knot speed language

The design of the electric precipitator is a complex system work. When determining its performance and structure, many factors should be considered comprehensively. For the design of high temperature flue gas electrostatic precipitator, this paper discusses some local theory and introduces it. Some structural improvements are available for reference by relevant personnel.