AСP aggregates: what they are and why they are for
31.08.2021846 Page views
Modern asphalt mixing plant consists of many units and ACP aggregates, which are needed to ensure the continuity of asphalt mixture production.
From a technological perspective, the latest “Kredmash” models have all characteristics of current and future equipment concepts. They are optimized in terms of wear and maintenance, safe for the environment, have excellent accessibility and easy in operation.
Due to their ergonomic dimensions and well thought-out functionality, our AMP are valued on the market as they easily fulfil all tasks of a modern road worker.
Read in our material about all main aggregates of ACP, their structure and purpose.
What types of ACP aggregates are there?
Modern asphalt mixing plant consists of many units and different aggregates that are mounted on the foundation site.
This equipment is based on the principle of modular aggregation. It provides for the interchangeability of components, parts and some units.
Their complete set of asphalt plant equipment is selected taking into account wishes of the customer, and it can include any desirable variant of implementation.
As a rule, the following units are provided in modern AMP:
- ACP power supply unit;
- ACP drying unit;
- Mineral powder and dust;
- Bituminous equipment;
- Pneumatic system;
- Control block;
- Cellulose additive unit;
- Adhesive additive unit.
Construction of ACP units and aggregates and their purpose
Let's look at this in great detail on the construction of ACP components and units and let's see what functions they perform.
- Power supply unit
ACP power supply unit is designed for pre-dosing of stone materials, as well as for removing of oversized material, foreign objects and so on.
It consists of unified blocks with a loading width of 3.5 m, equipped with grids with vibrators for the separation of large oversized material more than 100 mm. Each unit has a belt conveyor equipped with a drive with a frequency converter, as well as a contactless sensor to monitor the material availability on the belt. Pre-dosed stone material on the belt conveyor enters the collecting horizontal conveyor and then the inclined conveyor, and then is fed into the drying drum. Between the conveyors there is a vibrating grid for separating of oversized material more than 60 mm.
- Drying unit
The drying unit is designed to remove moisture, heat stone materials to operating temperature, as well as clean the furnace gases with minimal emissions of harmful substances into the air.
The drying unit consists of:
- heat-insulated drying drum with gear drive or friction drive with four gear motors on support rollers and smooth-start system. The drum is equipped with the original blades and buckets system that allow you to heat stone materials to operating temperature with minimal heat loss into the air;
- furnace unit is equipped with a burner that runs on natural gas or diesel fuel, or can be combined depending on the order. Thanks to the installed modern equipment, the furnace unit provides low fuel consumption per ton of finished mixture and minimal emissions of combustion products into the air;
- furnace gas filtration system based on modern bag filters, at the outlet of which we have a dust concentration of up to 20 mg/m3, which meets European environmental standards.
Bag filter unit consists of several compartments with an autonomous purge system in each of them due to the draft of the induced drag. At the inlet of the filter block, a louver-type dust collector is installed to collection of large "useful" fraction of dust, which can get into the elevator of stone materials and then into the "hot" hopper. The main part of the dust is collected in the filter unit and then transported by a separate elevator to the dust and mineral powder batching unit or accumulated in the dust silo with subsequent disposal (unloading to the side in the vehicle).
Thus, the operator can fully control the amount of dust in the recipe, which is the most bitumen-absorbing component of the mixture, which significantly affects the quality of asphalt concrete.
- Mixing unit
The mixing unit is intended for sorting of the stone materials into fractions, batching according to the recipe of components of asphalt concrete mixture (stone materials, bitumen, mineral powder, dust and various additives), their mixing and delivery of ready mixture to the vehicles or its temporary storage in storage hoppers.
The mixing unit consists of:
- Chain elevator of stone materials, which transports the heated material from the drying drum to the screen;
- Screen with wire-mesh sieves and two motor vibrators as a drive. It sifts stone materials into 5 or 6 fractions;
- Heat-insulated "hot" hopper, divided into 5 or 6 compartments, which gets the material from the screen. The compartments are equipped with continuous level sensors and sampling trays for quality control of the screening, and their total volume is increased to allow continuous operation of the unit if any fraction is missing in the source material. The bottom of the hot hopper is fitted with pneumatic gates which are designed to ensure accurate dosing of stone materials;
- Batching unit, in which the accuracy of bitumen, mineral powder and dust batching as well as stone materials is ensured by a frequency-controlled drive of the bitumen pump, butterfly valves on the augers of mineral powder and dust, and above all bending strain gauges. The volumes of the bitumen batcher and the mineral powder and dust batcher have been increased in order to easily produce mixtures with a higher percentage of bitumen and mineral powder (primarily stone-mastic asphalt).
- Mixing unit. The base of the mixing unit is the double shoulder or single shoulder layout of blades and racks. The blades of the mixing unit are cast from ni-chard, and the steel racks are protected by cast plates also from ni-chard. The blades life reaches about 100 thousand tons in Ukrainian granite.
- The next unit is responsible for distribution of the finished mixture between the compartments of the hopper, which is a movable carriage with a pneumatic drive.
- The heat-insulated hopper-storage has one or two compartments for temporary storage of ready mix, and also a compartment of direct unloading in the vehicle and a compartment of surpluses and oversized material.
- Mineral powder and dust unit
The mineral powder and dust unit is designed for receiving, temporary storage and transportation to the mixing unit of mineral powder and collected dust. The collected dust can also be sent for disposal to vehicles. Mineral powder is a filler that improves bitumen bonding properties and reduces the water absorption of asphalt concrete and increases its cold resistance property.
- Bituminous equipment
Bituminous equipment is designed for receiving bitumen, its temporary storage, heating if necessary to operating temperature, as well as the preparation of modified bitumen and its use in the manufacture of asphalt mixtures.
Bituminous equipment includes: horizontal or vertical heat-insulated tanks with oil registers, which due to the increased surface area provide high-speed heating of bitumen to the working temperature
The one-pipe system of bitumen supply to the mixer allows to use each capacity as working, and application of oil valves with electric servodrives ensures that the temperature of the bitumen in the tanks is maintained automatically. The heat-carrier is heated in a heat generator, the capacity of which depends on the number of bitumen tanks.
- Pneumatic system
The pneumatic system of the asphalt mixing plant is designed to provide units and assemblies with proper quality compressed air. The base of the pneumatic system is a screw compressor mounted on a receiver with a safety system for operating personnel against the effects of compressed air energy. Pneumatic cylinders, pneumatic distributors, pressure sensors, bags, etc. are also an integral part of the pneumatic system.
- Control block
The control block of the unit is a heat-insulated one-level cabin with a good visibility, a comfortable place for the operator, a climate control system. The computer control system is two-level, distributed type. It can be equipped with a remote monitoring system and video surveillance of individual areas of the installation. Electrical equipment is placed in sealed enclosures with individual climate control systems.
- Cellulose additive unit
This ACP unit is intended for dosing and giving the cellulose into the cellulose mixer which is used at production of stone-mastic asphalt mixtures. The cellulose additive prevents the binder from flowing off the stone materials and increases the strength of the road surface. The unit consists of a receiving block with the blowing fan for giving of cellulose upwards, air ducts, the dosing block with the weight batcher on bending strain gauges, control system.
- Adhesive additive unit
The adhesive additive unit is intended for dosing and giving into the mixer or in the bitumen batcher of liquid adhesive additives that improve the bond between bitumen and mineral materials on the chemical level, which in turn reduces the water absorption of asphalt concrete and increases its cold resistance property.
To find out more about the operation of each unit and aggregate, to discuss the suitable functionality and model of asphalt mixing plant for your job, contact the specialists of “Kremenchuk plant of road machines”.
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