In recent years, some factories have adopted air box type pulse dust collectors in the treatment of dryer exhaust gas. The author believes that this technology should not be widely promoted considering the use effect, direct investment and operating cost. Because the dryer adopts a gas box type pulse dust collector, it has at least the following defects: 1 Because the structure of the dust collector box is small, the high-humidity exhaust gas of the dryer gathers in the box body and is easy to dry, which is an important part in the preparation process of the raw material. Most cement plants in China use dryers to dry raw materials. The most used ones are back. CHANGZHOU ANTALYA TOOL AND MACHINERY CO., LTD. , https://www.atly-tool.com
Transfer dryer. The exhaust gas from the dryer is the main pollution of the cement plant.
One of the dyeing sources, its waste gas treatment is also a cement dust collection technology.
difficulty.
2 dryer exhaust characteristics
The exhaust gas discharged from the dryer has a chemical composition similar to that of the dried material; the dust concentration of the exhaust gas follows the object to be dried
The type, nature and operation of the equipment fluctuate greatly, and its characteristics
It is high in dust concentration; the temperature of exhaust gas varies greatly with fuel consumption, dryer output, exhaust gas volume, surface moisture of raw materials, etc. (but less than the fluctuation range of vertical kiln flue gas); high moisture content, moisture content in exhaust gas
Up to 20% or more. The process parameters for drying different materials are shown in Table 1.
Shown.
Material exhaust temperature (°C)
Dust concentration
(g/nl:)
Moisture content (%)
Clay 60—8050—15020～25 slag 70～10040～7520～25 iron powder 60～8010～2020-25 coal
70~100
40-75
10-15
3 dew point problem
According to the relevant dust removal theory, the dew point temperature of the dryer exhaust gas should be
55 ~ 60 ° C, but the author believes that the dew point is actually a variable. Whether it is a bag filter or an electrostatic precipitator, there is condensation problem.
In addition to the temperature and humidity content, the dust collector is ventilated.
The situation is also very important. Some dust collectors with poor ventilation conditions begin to dew when the temperature is higher than the recognized dew point, while some dust collectors with good ventilation conditions do not condense even if the temperature is lower than the recognized dew point. To control the dryer heating, we must fully understand the variability of the dew point and grasp the causal relationship between the factors affecting condensation.
1] 2
4
Primary dust removal and secondary dust removal
Dedusting of the dryer should abandon the secondary dust removal system, using ~ level
The dust system directly processes the dryer exhaust. Early dryer dust removal system
Because of the need to accommodate the dust collector's restrictions on the dust concentration of the population, a secondary dust removal system is used. The first-stage cyclone dust collector with low dust removal efficiency is used as a coarse powder separator, and the second-stage dust removal efficiency is high. Or electric precipitator. The secondary dust removal system has obvious technical defects. First, the system pipe network is complex, the resistance is high, the energy consumption is high, and the pipeline is extremely easy to block.
Plug; second, the amount of air leakage is large, resulting in a large temperature drop of the dust collector, extremely easy
Causes condensation. With the development of dust removal technology, the primary dust removal system can effectively solve the problem of high dust concentration in the population.
The secondary dust removal system is to change the secondary system to the primary system.
It is very ideal.
5
LFEF dust collector is currently the best dryer dust removal equipment
(I) LFEF dryer bag dust collector
The author personally participated in the transformation of dozens of dryers throughout the country.
The dust collector is modified from other types of dust collectors to LFEF.
The effect is generally good. Two factories in a factory in Sichuan Province. 2×12m
The dryer, originally used "first-class cyclone + two-level horizontal electric dust removal", the use of electric dust removal completely failed, the loss of dust removal capacity, after transformation into a LFEF dust collector, the effect is very satisfactory. Another factory, the 1.5×15m dryer originally used “first-class cyclone+double-layer pole-type electric dust removalâ€, the electric dust removal also failed, the pipeline was often blocked, which seriously restricted the production and was transformed into LFEF dust collector. The problem of pollution has been completely solved, and the containment of production has been eliminated. There is a 2.4×18m dryer in a factory in Guizhou. The original “first-class cyclone+two-stage multi-tube tube-type electric dust removal†has not only the dust-removing effect, but also the system ventilation is very poor, and the material has high moisture content. It became a bottleneck in the preparation process of raw materials. After we transformed it into LFEF dust collector, it not only solved the problem of dust removal and ventilation, but also reduced the final moisture of the material to I. Less than 5%, exceeding production control indicators. In another factory, the 2.2×12m dryer originally used “first-class cyclone+two-stage rotary anti-air bag dust collectorâ€. Although there is a certain dust removal effect, the filter bag is frequently dew condensation, and the damage is very serious. Operation, seriously restricting the quality of production, after we transformed into LFEF dust collector, the problem of condensation and broken bag was solved from the source, the quality of the main machine was greatly improved, compared with other various dust collectors, LFEF dust collector has Obvious technical advantages.
(2) The dust collector is not suitable for use in the dryer. The dust collector is used in the dust dryer. There are many lessons for failure. This has its technical deep-seated reasons. Electrostatic precipitator treatment of exhaust gas, there are the following technical problems that cannot be overcome:
1 It is impossible to directly treat high-concentration exhaust gas, and a secondary dust removal system has to be used. The secondary dust removal system is an important cause of a series of problems in the dust removal system;
2 There is a problem that the resistance is not suitable. Because most dryers are mixed drying materials, the dust, clay, slag, coal, iron powder and other dusts are not the same as the resistance value. Considering the investment cost, the dryer The size of the dust collector should not be too large, otherwise it will not be able to adapt to the change of the specific resistance value.
Chemical
3 Condensation and corrosion can not be overcome, the dust collector can not maintain the initial
Performance, failure to use will not expire.
(3) Technical advantages of LFEF dust collector
1 filter material technology; poor performance of filter materials, which is restricting early bags
One of the important reasons for the use of dust collectors, early on the bag filter
Whether it is chemical fiber woven fabric, cotton cloth or fiberglass cloth, its effect is very poor, and its service life is very short. Therefore, Hefei Cement Research and Design Institute is developing LFEF glass fiber bag in the process of machine dust collector. I tried to use a variety of filter materials, and I think that fiberglass woven fabric is a suitable filter material. The glass fiber woven fabric has the advantages of high temperature resistance, corrosion resistance, dimensional stability, small expansion ratio, high strength, etc.; however, the glass fiber has poor flexibility, is easily broken and worn, and the surface of the glass fiber cloth is poor in hydrophobicity and is prone to condensation. In order to improve the performance of glass fiber woven fabrics, Hefei Cement Research and Design Institute cooperated with Nanjing Fiberglass Institute to introduce glass fiber surface treatment technology through the surface of glass fiber.
Coating different high molecular organic polymers to enhance the chemistry of glass fiber
Stability, thus improving the flexibility of the glass fiber, to ensure that the strength, folding resistance and wear resistance of the glass fiber are not decreased under long-term high temperature and acid-base atmosphere, and the hydrophobic agent is added to the treatment agent to make the glass fiber have anti-knot Dew performance,
FCA formula is a kind of 专门 specially developed for dryer dust collector
Water formula. At the same time, Hefei Cement Research and Design Institute put forward improvement suggestions on the fabric structure, filter cloth thickness and air permeability of glass fiber woven fabrics in combination with practice, so that the performance of anti-condensation glass fiber woven fabrics is continuously improved. At present, the performance of anti-condensation glass fiber filter cloth has completely adapted to the requirements of dryer flue gas dust removal, not only can solve the condensation problem, but also can directly deal with high concentration flue gas, making the first stage dust removal possible.
2 cleaning technology; introducing sub-chamber backflushing technology, using off-line cleaning, ideal for cleaning, the initial performance of the precipitator remains very good;
With the continuous improvement of accessory technology, the reliability of cleaning is greatly improved.
3 control technology; introduction of PC automatic control system, automatic monitoring of exhaust gas temperature and automatic operation of cleaning and unloading ash, operation management
easy and convenient.
4 primary dust removal technology; due to the improvement of filtration materials, cleaning and discharging technology and control technology, LFEF technology abandoned the early secondary dust removal
On, directly use the glass fiber bag filter to treat the exhaust gas of the dryer, the whole system
The performance is greatly improved, and the total investment and operating costs of the system are large.
The magnitude is decreasing.
6
Suggestions on LFEF dryer glass fiber bag dust collector
(1) intake structure; the original LFEF dust collector adopts a stepped level
The tube is inhaled from the top part of the inlet chamber, which is easy to cause uneven distribution of airflow between the chambers, and is also likely to cause the middle and the periphery of the bag chamber.
The airflow is unevenly distributed. It is recommended to remove the horizontal stepped intake pipe and remove the intake air.
The chamber partition is changed to the chute air inlet, and a multi-stage baffle is installed to facilitate
The gas chamber smoke is naturally balanced.
(2) Ash and ash return; powder recovered by LFEF dryer dust collector
The dust is light, thin, dry and has strong fluidity. It is easy to run, run, escape and leak during the ash returning process. It is recommended to return the ash directly into the hoist. It is best not to return.
Belt conveyor to avoid secondary dusting; original LFEF dryer dust collector is equipped with LS250 screw conveyor for ash, but LFEF dust removal
Interrupted ash discharge, LS250 screw conveyor instantaneous ash delivery capacity
Not enough, it is recommended to send gray spiral at least with G) (300 type, conditional
Manufacturers can configure more powerful Fu chain conveyors.
(3) It can be concentrated dust removal; for some plants with suitable conditions,
Handling multiple dryer wastes with a LFEF fiberglass bag filter
Gas can greatly reduce investment costs and operating costs.
7
Conclusion
In recent years, some factories have adopted air box type pulse dust collectors in the treatment of dryer exhaust gas. The author believes that this technology should not be widely promoted considering the use effect, direct investment and operating cost. Because the dryer adopts a gas box type pulse dust collector, it has at least the following defects: 1 Because the structure of the dust collector box is small, the high humidity exhaust gas of the dryer is concentrated in the box body.
saturation. In this way, the first is that the filter bag is easy to dew the paste bag, and the main fan chimney is easy to see.
To the water vapor; the second is that the dust is easy to absorb moisture, and the moisture is not dry, which may cause the ash conveying mechanism to block the ash. 2 Because it is an external filter type dust collector, the dust and the box are in direct contact, and the dust collector is easily corroded. 3 filter material performance is not enough, RETON easy to burn bags, glass fiber needle felt, poor folding resistance, short life. 4 More importantly, RETON and fiberglass needle felts are expensive, resulting in high maintenance costs for the dust collector.
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