During the production process, a significant amount of dust is released during the crushing, screening, transport, drying, mixing and loading processes that must be done in asphalt plants. Outdoor aggregate storage areas, conveyor belts and aggregate transfer points can also be a source of high amounts of dust due to wind effect in open areas.
In dryers where the aggregate is heated, undesirable gases such as sulfur dioxide, carbon monoxide and nitrogen oxides originating from combustion, along with dust, and harmful organic substances that may arise by heating the bitumen material are also formed.
Depending on the fuel type, dust and gaseous pollutants originating from combustion are formed from the hot oil boilers used while heating the bituminous material.
Dust will be released as a result of crushing-sieving processes in integrated facilities where aggregate production is also carried out. In other words, drilling, blasting operations, loading-unloading, crushing-sieving operations in the quarry and open transport and storage of materials are also sources of dust emission.
WAYS TO REDUCE AND CONTROL EMISSIONS
The main pollutant for both integrated asphalt plants and non-integrated plants is dust. Dust emission can be reduced by collecting dust with dust collection systems and passing it through a dust filtering system. The most preferred filtration system is bag filters. Apart from this, electrostatic filters and aqueous dust control systems can also be used.
Apart from this, dust emissions that will occur on the aggregate conveyor belts can be reduced by using closed belt systems. The dust retained in the dust filtering system is reused as filler material in production and provides an economic contribution.
In order to reduce gas emission, drying and heating processes in dryer rotary kilns should be done with quality fuels and combustion systems. The heat energy of the waste gases must be recovered and used in the drying system. Dust emissions that will occur in these furnaces should also be filtered with the existing dust collection system or an independent dust control system should be established.
In mixers where aggregate, bitumen and other additives are mixed, it is recommended to collect and treat the organic compounds that evaporate during loading on the truck and during the bitumen filling.
Organic harmful substances will be formed as a result of heating the bituminous material in drum mix (continuous mix) asphalt plant dryers and facilities using recycled asphalt. Depending on the amount of oscillations, control techniques can be applied.
In addition, in-plant roads should be covered, cleaned and dust suppression applied in order to reduce dust emission in production areas. In addition, windbreak curtains and dust suppression systems should be used in storage areas. Thin materials should be stored indoors as much as possible.
It is recommended to carry out crushing-screening activities in completely closed areas in order to reduce dust emission and to be easily controlled.
Electrical energy may be preferred as an option for heating insulated bitumen tanks.