Asphalt Plant Road Construction

Dust Extraction in Asphalt Plant

 Dust extraction  of aggregate is the process to remove dust after drying cold aggregate. A certain amount of dust is carried away in the hot gases from the dryer and it is usual for this to be collected in a dust collector.

The type of extractor normally used consists of a set of high energy cyclones and a low energy water scrubbing system. In isolated areas the scrubber may be eliminated.

The fan in the dust extractor creates suction from the dryer, hot bins etc. and delivers the dust to the cyclone type collector, where it is precipitated by centrifugal force. If the dust is found to be suitably graded, it can be returned to the plant for inclusion in the mix

Aggregate  from  the  dryer  is  fed  to  screens  mounted  over  the  hot  bins.  The screens separate the aggregate into selected sizes for proportioning, and reject oversize particles. Vibrating screens are preferred. This screening and recombining of aggregate  is carried out to correct segregation resulting from passing the combined aggregate through the dryer.

It will also help to correct variations in relative proportions of sand and coarse aggregate. However, as the smallest hot screen size is approximately 4 mm, hot screening will not correct any grading variations in material below this size.

For efficient screening the screens should be:-

• Of Adequate effective area

• Of the correct size opening

• Clean and in good condition

• Property arranged and at the correct slope

• Vibrating in the correct manner.

Hot storage Bins and Screens

For a general purpose plant there should be at least four bins to hold the hot aggregates, but  the  number  in  use  will  depend  on  the  type  and  size  of  mix  being  produced.  Bin  capacity should be adequate for continuous operation at maximum output. Each bin should be fitted with a  contents  indicator  in  full  view  of  the  operator,  and  with  an  overflow  outlet  to  ensure  that should  a  bin  become  overfull,  the  excess  will  not  spill  into  an  adjoining  bin.  A  thermometer should  be  installed  in  each  hot  bin.  The  hot  bins  function  as  small  reservoirs  to  dampen variations in supply rate and to improve batching.

Dust extraction is one step of the asphalt batch and continuous  plants. It is recommended to see that post.

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