Design and preparation of the site of the asphalt plant

21.12.20204244 Page views

Design of the asphalt plant is a complex process that begins upon the agreement with the customer of the size and shape of the site where the asphalt plant is planned to be located, and ends with the act of commissioning the purchased equipment and certification of the asphalt plant in the relevant government agencies.

We start with the required productivity of the asphalt plant. The power of electric substation, the cables cross-section, the volume of bitumen, mineral powder, crushed stone storage, the power of the gas distribution station and more depend on its productivity.

Design of asphalt plant (AP)

Of course, the asphalt plant is a dangerous production facility because it stores and uses combustible materials (fuel, gas), uses pressure equipment, and so on. Therefore, for the commissioning of the asphalt plant a set of coordination measures in the relevant government authorities must be approved. 

The heart of any asphalt plant is the asphalt mixing unit. Design of AP begins first of all with the analysis of the road equipment market and estimation for designing of asphalt plant. That is, what productivity is currently required, what requirements for the design of the unit dictates the market today, what competitors offer, and others.

In other words, the market determines the appearance of the unit, its design. For example, now it is very popular asphalt mixing units of tower type with units of "cold" and "hot" recycling, units of cellulose and adhesive additives, systems for modification of bitumen by polymeric additives, etc.
The tower type is attributable to space savings, because the land is getting more expensive.

"Cold" and "hot" recycling makes it possible to reduce the cost of asphalt mix by using of "used" asphalt, where is available the most expensive component of asphalt bitumen.

Adding of additives to bitumen improves the quality of the finished mixture and increases the durability of the road surface.

Such asphalt mixing plants are manufactured today by PrJSC "Kredmash".

By the way, in 2020 “Kredmash” manufactured and delivered only in Ukraine 22 asphalt mixing plants and ground-batching plants, half of which work on the construction of highways.

And for the last 5 years we have sold 110 units within Ukraine. Therefore, it is not by chance “Kredmash” has joined the National Association of Road Workers of Ukraine (NARWU), the founders of which are such companies as “Avtomagistral-Pivden”, ONUR, “Altcom”, JV “Avtostrada” and others.

Asphalt mixing and ground-batching plants manufactured by “Kredmash” are used in “Large Construction” project.

Why buy our asphalt mixing plants?

Because “Kredmash” products meet the basic requirements of the customer:

• high quality asphalt;
• ensuring of the declared productivity;
• low cost of spare parts and repairs;
• adequate indicator price - quality of “Kredmash” products;
• “Kredmash” is 100% domestic producer.

Each asphalt mixing plant manufactured by PrJSC "Kredmash" shipped to the customer is designed and assembled taking into account their needs and the requirements of technical safety regulations. For this purpose, our specialists also design AP protection system.

The basic equipment includes:

• A power supply unit that provides pre-dosing of stone materials and their supply to the drying unit, as well as pre-screening of oversized material by means of an oversized fractions sieve installed between horizontal and inclined conveyors. The supply units are equipped with drives with frequency converters, as well as contactless sensors to monitor the material availability on the conveyor belt. The assembled horizontal conveyor and the inclined conveyor have rubberized drive drums, safety cables, a fence according to the safety standard.
• The drying unit, which dries and heats the stone materials to the operating temperature and transports them to the elevator of the mixing unit, as well as cleans the smoke fumes in the bag filter. The drying unit consists first of all of a heat-insulated drying drum with a friction or gear drive. The required amount of heat is given off by a burner from a specialized European manufacturer, which is installed on a separate retractable trolley, which simplifies the maintenance of the burner and drying drum. The burner operates on natural gas, diesel or can be combined depending on the order. Such burners provide low fuel consumption (about 5 m³ of natural gas) per ton of finished mixture and minimal emissions of combustion products into the air. The smoke fumes are extracted by the smoke extractor from the drying drum and get into the block of bag filters, the area of the filter cloth of which provides emissions into the air not more than 20 mg/m2. The filter unit consists of several compartments with an autonomous purge system in each of them by means of a smoke extractor. At the entrance to the filter unit, a louvered-type dust collector is installed to collect a large fraction of dust, which can enter the elevator of stone materials and then into the first compartment of the "hot" hopper. This is the so-called "useful" dust fraction. 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 dosing system or accumulated in the dust bin with subsequent disposal through the screw in vehicles.
• Mixing unit, which provides sorting of heated stone materials into 5 or 6 fractions according to European requirements, their temporary storage in a heat-insulated hopper of hot materials, dosing and feeding to the mixer. The volumes of the hot hopper, weight batchers of stone materials, bitumen, mineral powder and dust have been increased in such a way as to produce crushed stone-mastic mixtures without any problems. The design of the mixer allows to optimize the process of mixing of mix components, to minimize a cycle of preparation of mix, but to provide thus its high quality and homogeneity. The ready mix gets through the trolley with the pneumatic drive in corresponding compartments of the accumulative bunker from the mixer. There is usually a direct unloading compartment for non-standard mix and the oversized fractions and excess compartment.
• Mineral powder and dust unit, which is responsible for the use of mineral powder and collected dust in the process.
• Bituminous equipment, which consists of the oil heat generator, horizontal or vertical bitumen tanks of auto-size, equipped with oil registers, the area of which allows not only to compensate for heat loss into the air, but also to heat the bitumen to operating temperature. The one-pipe system of bitumen feeding to the mixer allows to use each capacity as working, and application of oil cranes with electric servo drives provides an automatic mode of maintenance of temperature of bitumen in tanks.
• The control unit of the unit is a heat-insulated one-level cabin with a good view, a comfortable place for the operator, a climate control system. Computer control system is two-level, distributed type. It can be equipped with a remote monitoring system, video surveillance of individual areas of the unit. Electrical equipment is placed in sealed enclosures with individual climate control systems.

The dimensions of most of the blocks of the asphalt-mixing plant fit into the dimensions of the Euro truck. These parameters are taken into account when drawing the future asphalt plant.

Much attention is paid to the safety of maintenance of units for staff. The design meets the requirements of technical regulations of Ukraine on safety of machines and mechanisms, low-voltage equipment and electromagnetic compatibility.

Of course, the customer is offered a variety of options: additional bins for temporary storage of mineral powder, additional bins of the power supply unit, units of cellulose and adhesive additives, equipment for modification of bitumen with polymer additives, units of "cold" recycling, additional bitumen tanks with pipe fitting, electric hoist for lifting loads up to 500 kg.

Given the fact that many existing old asphalt-mixing plants are operated, today PrJSC "Kredmash" is intensifying efforts to develop the production of ready-made solutions in the form of a separate supply of components and units for modernization of old plants to new requirements for asphalt concrete. These are sorting units for the transfer of mixing units of existing plants to 5-fraction system of screening and dosing of stone materials, and separate dust units, and new casting with increased wear resistance for mixers, and new screens with wire-mesh sieves, and more powerful burners for drying drums and more.

Preparation of the site for AP installation from “Kredmash”

During the construction of the asphalt plant, it is necessary to take into account the access point for vehicles or rail vehicles for unloading the same bitumen, fuel, mineral powder, crushed stones, loading of dump trucks with the finished mixture. In addition, the preparation of the site for the asphalt plant (AP) provides for obligatory availability of a weighing station for weighing loaded and empty vehicles.

To load of the power supply unit, it is necessary to make retaining wall with surcharge.

If the environment allows the use of a dust collection system based on Venturi scrubber, it is necessary to have access to water.

The stationary asphalt mixing plant can be placed both on the concrete bases, and on metal underlying frames. In the first case, the customer builds concrete foundations taking into account the properties of local soils, in the second case - levels and compacts the site where the asphalt mixing plant will be located.
Due to the implementation of European standards in the design of a new model range of asphalt mixing plants, as well as taking into account the experience of manufacturing and operation in real conditions, it can be argued that today PrJSC "Kredmash" has reached a new level and technical parameters closer to European manufacturers of asphalt-mixing plants.

In addition, PrJSC "Kredmash" is able to manufacture other equipment: it is concrete mixing plants of periodic action, and equipment for utilities, including machines for pit repairs, mini-sprayer, which have shown themselves in real operating conditions.

Deputy Chief Designer of PrJSC "Kredmash" Serhiy Perepelchenko