What kind of dust collector is used in slag grinding system

In order to better play the potential of slag,slag is required to be ground. From the《for the cement and concrete granulated blast furnace slag powder》(GB/T18046-2000) standards,as long as the slag specific surface area control in the 420-450 ㎡/kg,to meet the standard S95 requirements. This will not only meet the cement factory to provide 42.5-52.5 grade slag cement (slag content of 30% to 50%) requirements,but also to meet the ready-mixed concrete company configuration is greater than C60 concrete requirements. According to the existing equipment,can take vertical grinding,roller press,ball mill,vibration grinding four final grinding process,or the use of vertical grinding + ball mill,roller press + ball mill combined grinding process. In recent years,the use of vertical grinding slag powder production of the final grinding process is the most common and rapid development.

1. Characteristics of Dust-Containing Exhaust Gas in Slag Grinding System

(1) Fine dust particles

Grinding the slag to a certain fineness (specific surface area) in order to fully participate in the hydration reaction to improve the activity,but also with the particle composition,fine particles and more than the surface area. In the standard specific surface area, slag less than 10μm particles accounted for 58%,more than fly ash and P.0525 cement.It can be seen,the slag powder particle size is small, in the exhaust gas suspension,to bring more difficult dust.

(2) High dust concentration

Whether it is ball milling process or vertical grinding process,due to the abolition of the secondary dust with cyclone dust collector,slag grinding system dust exhaust dust concentration is high,generally 400 -1000 g/m³.

(3) High dust moisture content

As the water quenching slag with high water content,sometimes up to 15% to 20%,into the mill before the water is difficult to remove,in the mill grinding process will produce a lot of heat,vertical grinding also attached hot air furnace heating air to the grinding Machine,the final finished powder moisture control in the 0.5% to 1.2%,with the exhaust gas into the dust collector too fine powder easily lead to deodorization paste phenomenon.

2. Current Situation of Dust Control Technology in Slag Grinding System

With the continuous development of dust collector technology, especially the development of new filter and application and cleaning technology development,the dust collector in the slag grinding system dust has been more widely used. Aiming at the characteristics of slag grinding process system and dust-containing exhaust gas,two types of bag-type dust collector are developed and applied both at home and abroad.One of the pulse injection type air box pulse bag filter,low pressure long bag pulse bag filter and box combination of low resistance high efficiency dust collector.

Back-blowing dust collector is the use of high-pressure anti-hair dryer for cleaning the filter bag,has the following characteristics:

(1) The use of internal filter blowing back,cleaning power is low,the filter wind speed must take a low value,the design of the normal selection of wind speed 0.4-0.5 m/min,so the equipment is larger,high steel consumption,accounting for large area of investment and high investment shortcomings.

(2) The normal handling of low concentrations of dust-containing gas, allowing the inlet dust concentration of less than 150 g/m³,for high concentrations of exhaust dust,must use two dust collection,so the process is more complex;

(3) Dust removal efficiency is higher,such as the filter wind speed to take low value,but also to achieve emission concentration < 50 mg/Nm³, but it is difficult to achieve emission concentration < 30 mg/Nm³;

(4) The use of anti-blowing dust,cleaning is difficult to complete, equipment design resistance is less than 1770 Pa,when the introduction of a large number of fresh air,is not conducive to anti-condensation;

(5) Due to the equipment bulky,complex process,covers an area of large,does not apply to large-scale,large air handling slag grinding production line.According to the above characteristics of the analysis,the technology will be less and less,until eliminated.

With the improvement of new filter performance and the development of pulse cleaning technology,pulse jet bag filter in the slag grinding system dust to a certain degree of application.Compared to the back-blowing dust collector,pulse-blown bag filter has better performance, its performance characteristics are as follows:

(1) The use of external filter,the design filter speed of 0.8-1.0 m/min,so the equipment is small,low steel consumption,small footprint and less investment advantages;

(2) Can handle less than 1000 g/m³of high concentrations of dust-laden gas,whether it is with the vertical mill or milling with a single as long as a dust collection,the process is simple;

(3) The use of electromagnetic pulse valve for pulse cleaning, cleaning power,cleaning thoroughly;

(4) Selection of polyester needle felt film filter,anti-wear and tear resistance of the strong performance,anti-condensation performance.

However,low pressure long bag pulse dust collector for slag grinding system,due to slag powder dust particles fine,high moisture content, strong viscosity,cleaning more difficult,it will cause the machine resistance and high system production and operating costs.The dust collector is a row of spray,the presence of dust flying twice,the resistance rose faster,cleaning the number of times,shortening the pulse valve and filter bag life.

In order to effectively avoid the high resistance of the dust collector,filter bag life is short and power consumption and other shortcomings,the domestic research and design institute has developed the PPW air box pulse bag filter and LDM large low-resistance bag dust Device. Among them,PPW air box pulse bag filter is in the original box pulse bag filter on the basis of improved,suitable for 200,000 m³ below the air flow;LDM large low-resistance bag filter is in the original box Pulse bag filter on the basis of large air volume,low resistance and the structure of the optimal design of the wind,the use of "box tube pulse pulse" cleaning device for more than 200,000 m³ processing air volume,two bags of dust filter on the filter materials are optimized for the selection,the two bags of dust collector has become a domestic slag grinding system of domestic dust removal equipment of choice.

3. Introduction of New Technology of Dust Removal in Slag Grinding System

3.1 PPW type air box pulse bag filter use for slag

PPW air box pulse bag filter mainly by the box,bag room,ash bucket, inlet and outlet,filter bag,filter cage,pillar,ladder,railings,gas system,poppet valve system,ash removal device,and other components. And the inlet and outlet are connected to form a duct,the inlet and outlet are arranged in the opposite sides of the bag chamber,the middle with a diagonal partition separated into two parts of the airtight,so that the air distribution and uniform dust collection effect.

The working principle is dust flue gas first into the air inlet,in the duct oblique baffle under the guidance of the duct to reduce the wind speed decreases,part of the larger dust particles here due to inertia, natural settlement and other reasons fall ash, most of the dust particles with the air into the bag room,filtered by the filter bag, the dust particles were blocked in the filter bag outside,the purification of the smoke from the bag into the net inside the air box. The outlet into the atmosphere,to achieve the purpose of dust collection;with the continuous process of filtration, filter bag outside the dust gradually increased,so that the dust collector running resistance is gradually increased. When the resistance increases to a pre-set value (1245-1470 Pa) or set time to time,the cleaning controller sends a signal,first control the valve to close the valve plate to cut off the unit to filter the flue gas flow,stop the filtration process,then the electromagnetic pulse valve is opened, in a very short time (0.1-0.15 s) to the netting box into the pressure of 0.5-0.7 MPa of compressed air,compressed air in the clean air tank quickly expanded into the bag inside.So that the filter bag deformation, vibration,coupled with the role of anti-air flow,the bag outside the dust will be cleared down into the hopper,after cleaning the poppet valve once again open,dust collector and into the filter state. Cleaning action by the PLC for automatic control,cleaning controller has two kinds of timing and constant pressure.

Features:

(1) Can handle high concentrations of dust-laden gas, as long as a dust collection, the process is simple;

(2) The advantages of smaller equipment, low steel consumption, small footprint and less investment;

(3) Has high efficiency in dust removal, especially for micro dust with a higher dust removal efficiency;

(4) Equipment running resistance is low, the resistance is less than 1500 Pa;

(5) Filter bag long life, good anti-condensation performance.

4. Selection of Dust Collector for Slag Powder

According to the process design and the original parameters of the dust collector for the selection,the main steps include: the determination of the amount of air handling,dust collector type to determine the selection of filter wind speed,filter area calculation, dust collector specifications selection.

4.1 Determination of Handling Air Volume

Due to the different process of slag grinding system,the raw material moisture is different,the quality requirement of the product is different,so the unit production is different in air volume. In the practice of industrial operation,most of the use of vertical grinding grinding process,the finished material all with wind transport,air flow is usually used to" take the mined powder required minimum air flow" calculated,take away the required the minimum air volume can be calculated according to the inlet dust concentration of 220-270 g/m³. The processing air volume can also be calculated by the mill stand-alone output when the air flow rate Q =(4200-4800) G,where G is the mill output (unit: ton/hour),the results of the two calculation methods are basically the same the bag air filter processing air volume should be based on theoretical calculation combined with empirical data selection, according to the general production of the maximum amount of waste generated by the selection,and to consider 5% of the system air leakage.

4.2 Determination of Dust Collector Type

According to the above structure and principle analysis,PPW air box pulse bag filter and LDM large low resistance bag filter has its own scope. For 200,000 m³ below the handling of air flow,the choice of PPW air box pulse bag filter; for more than 200,000 m³of air flow,you can use LDM large low-resistance bag filter.

For the treatment of small air volume PPW air box pulse bag filter, the normal working conditions can be used ordinary polyester needle felt and polyester needle felt film filter. Such as the use of 550 g/㎡ polyester needle felt filter,filter wind speed selected 1.0 m/min below the more appropriate; such as the use of 550 g/㎡ polyester needle felt filter, filter wind speed of 0.8-0.9 m/min more appropriate. For the treatment of large air volume LDM large-scale bag filter,should be taken into account the characteristics of slag powder,running resistance and filter bag life and other factors,the choice of 550 g/㎡ polyester needle felt filter media filter speed 1.0 m/Min the following is more appropriate.

5. Concluding

The selection of the slag powder bag type dust collector should mainly consider the determination of the air volume,the type of dust collector,the selection of the filter wind speed,the calculation of the filter area,the selection of the dust collector and so on. At present,PPW air box pulse bag filter and LDM large low resistance dust collector has been widely used,with the slag powder production line scale is growing, LDM large low resistance dust collector has a good application economic benefits,social benefits and environmental benefits,the dust collector has become the first choice for owners and design institutes.