Asphalt plant process varies each other due to the different types of asphalt mixing equipment. The asphalt plant process refers to a series of production processes from the addition of aggregate to the completion of finished materials. The asphalt plant is a complete set of equipment for mixing various cold aggregates with different particle sizes, liquid asphalt, mineral powder, etc. to produce finished asphalt. Overall the asphalt plant is divided into two categories: asphalt drum plant and asphalt batch plant from the prospective of production technology. This post will describe the asphalt plant process of both categories.
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Asphalt Plant Process of Drum Type
The asphalt drum plant, also named continuous asphalt plant, is the plant that produces the finished materials in a continuous production way. The asphalt plant process of drum type includes these procedures.
Loading: According to the particle size, the different cold aggregates are fed into the different cold material bins. Generally speaking, there are three to four cold hoppers equipped in the factory, and the specific number can be customized by customers according to their needs. The filter screen in the cold hopper will filter the raw aggregate and screen out the unqualified large particle aggregate. The cold hopper feeder is equipped with an aggregate sensing device to ensure that a specific amount of aggregate is required.
Transportation: The aggregates in the cold hoppers fall onto the flat belt conveyor after screening, and then enter the drying drum through the inclined belt conveyor.
Drying and heating: The drying drum removes the moisture and heats the aggregates to ensure a appropriate mixing temperature. At the same time, The liquid asphalt separately stored in the asphalt tank enters the drum through the pipeline under the control of the asphalt pump driven by the variable speed motor. The powder stored in the powder bin enters the drum through the screw conveyor. The drying drum is inclined, which makes it easy for aggregates to move from one end to another.
Mixing: For the asphalt drum plant, the mixing area is also in the drying drum. The heated aggregates, liquid asphalt and powder are mixed in the second part of the drum. During the heating and mixing process of the drying drum, certain wastes will be discharged. In order to avoid air pollution, dust removal devices are generally used for treatment this problem.
Finally, the finished materials are discharged to the waiting truck or storage silo.
Asphalt Plant Process of Batch Type
The asphalt process of batch type is almost same as that of drum type. The difference is that the drying and heating of cold aggregate and the mixing of mixture are carried out in the drum and the mixing host respectively during the production of asphalt mixture in the asphalt batch plant. The asphalt batch plant also has the screening and metering process for hot aggregate.
First, the raw aggregates in different particle size are unloaded into the matched cold material hopper. In the process of cold aggregate passing through the hopper screen, the large particle aggregate is screened out by the screen, and the aggregate meeting the specification enters the hopper.
Second, the heated aggregate enters the drying drum under the transportation of horizontal belt and inclined belt.
Then, the hot materials are transported to the vibrating screen which is in the top of the mixing tower. The mixing tower consists of three parts, vibrating screen, hot material bins and two shaft mixer. The vibrating screen screens the hot aggregate according to the particle size, and then the hot aggregate is stored in the compartment of the hot aggregate bin for the next operation.
Next, the aggregate stored in the hot bin compartment is measured according to the mixture proportion and then released into the mixer. After separate measurement, the hot liquid asphalt and powder enter into the mixer through the hydraulic asphalt pump and screw conveyor as well. For the asphalt batch plant, a certain amount of waste gas and dust will be produced during the drying and heating of cold aggregates and the lifting and screening of hot aggregates. Installing a dust filter is very necessary to ensure the emission standard. Mostly the bag house dust filter is a good choice to treat the dust and waste gas.
Finally, the finished asphalt mix is discharged into the temporary storage silo or the waiting truck.
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