Selection of large-scale asphalt mixing equipment High-grade highways have strict requirements for black pavement equipment. Mixing, paving, and rolling are the three main processes of mechanized pavement construction. Asphalt concrete mixing equipment is an important factor in determining progress and quality. Mixing equipment is generally divided into two categories, namely continuous and intermittent. Due to the poor specifications of domestic raw materials, high-grade highways do not use the continuous roller type and require the forced intermittent type. There are many types of asphalt mixing equipment, with different mixing and dust removal methods, and different site requirements.

1.1 Overall machine performance requirements
(1) The output should be ≥200t/h, otherwise it will be difficult to organize mechanized construction and ensure continuous paving of asphalt pavement, which will eventually affect the overall quality of the pavement.
(2) The gradation composition of the asphalt mixture to be mixed should comply with the requirements of Table D.8 of JTJ032-94 "Specifications".
(3) The allowable error of the oil-stone ratio is within ±0.3%.
(4) The mixing time should not exceed 35 seconds, otherwise the asphalt penetration in the mixer will be lost too much and it will easily age.
(5) A secondary dust collector must be equipped; the Ringelmann blackness of the flue gas at the chimney outlet shall not exceed level 2.
(6) When the moisture content of the mineral material is 5% and the discharge temperature is 130℃~160℃, the mixing equipment can work at its rated productivity.

1.2 Main components
(1) The main burner requires a large air-to-oil ratio, easy adjustment, reliable operation, and low fuel consumption.
(2) The blade life of the mixer is required to be no less than 3000 hours, and the mixed finished materials should be uniform and free of whitening, segregation, agglomeration, etc.
(3) The service life of the power part of the drying drum is not less than 6000h. The drum can make full use of heat and the material curtain is even and smooth.
(4) The vibrating screen is required to be fully enclosed. Dual vibration motors replace the previous eccentric shaft vibration. Each layer of screen mesh is easy to assemble quickly.
(5) The asphalt supply system is required to be insulated with thermal oil and equipped with an automatic control device that displays the temperature.
(6) The main console should generally have manual, semi-automatic and fully automatic (programmed controller) control methods. Imported equipment is required to have electronic computer control functions (i.e. PLC logic computer + industrial computer); try to use fully automatic control when weighing/mixing Way.
1.3 Composition of asphalt mixing plant 
Asphalt mixture mixing equipment generally consists of the following parts: cold material grading machine, belt feeder, drying cylinder, aggregate elevator, vibrating screen, hot aggregate bin, mixer, powder system, It is composed of asphalt supply system, electronic scale, bag dust collector and other systems. In addition, finished product silos, thermal oil furnaces, and asphalt heating facilities are optional.

2 Selection and supporting equipment of asphalt plant auxiliary equipment When the asphalt mixing plant host machine is selected based on the project volume, project progress and other requirements, the asphalt heating facilities, barrel remover, thermal oil furnace and fuel tank should be immediately calculated and selected. If the main burner of the mixing plant uses heavy oil or residual oil as fuel, a certain number of heating and filtering facilities must be installed.

3. Installation of asphalt plant
3.1 Site selection
(1) In principle, large-scale asphalt mixing plants occupy a larger area, have more types of equipment, and must have a certain storage capacity for stone stacking. When selecting a site, it should be close to the roadbed of the bid section and located near the midpoint of the bid section. At the same time, the convenience of water and electricity sources should be considered. Convenient transportation of raw materials and finished materials in and out of the mixing station should be adopted.
(2) Natural conditions of the site The environment of the site should be dry, the terrain should be slightly higher, and the groundwater level should be low. When designing and prefabricating equipment foundations, you must also understand the geological conditions of the site. If the geological conditions of the site are good, the cost of equipment installation foundation construction can be reduced and equipment deformation caused by settlement can be avoided.

(3) Selection of a site that can supply asphalt mixture to several connected road surfaces at the same time. In this case, whether the equipment installation location is suitable or not, a simple way is to compare various costs by converting various costs into the weighted average transportation distance of the material. Confirm later.
3.2 There are many types of equipment for laying out large-scale asphalt mixing plants, mainly including mixing main engine, asphalt storage facilities, finished product silos, thermal oil furnaces, barrel removers, power distribution rooms, cable trenches, double-layer asphalt pipeline layout, automotive electronics There are scales, parking spaces for all road construction machinery and vehicles, machine repair rooms, laboratories and materials yards of various stone specifications; after the start of construction, more than ten kinds of raw materials and finished materials will enter and exit the mixing plant. This should be planned comprehensively and reasonably, otherwise it will seriously interfere with the normal construction order.
3.3 Installation
3.3.1 Preparations before installation
(1) Before all auxiliary facilities and complete sets of asphalt mixing equipment are transported to the site, it is particularly important to draw the mutual position diagram of the major assemblies and foundations. During installation, it is particularly important to ensure that the crane is successfully in place in one lift. Otherwise, the crane will be placed on site multiple times. Lifting and transporting equipment will cause an additional increase in shift costs.
(2) The installation site should meet the requirements and achieve "three connections and one level".
(3) Organize an experienced installation team to enter the construction site.
3.3.2 Required equipment for installation: 1 administrative vehicle (for contact and sporadic purchase), 1 35t and 50t crane each, 1 30m rope, 1 10m telescopic ladder, crowbar, sledgehammer, Common tools such as hand saws, electric drills, grinders, wire crimping pliers, various wrenches, safety belts, levels, and a ZL50 loader are all available.
3.3.3 The main sequence of installation is asphalt auxiliary facilities (boiler) → mixing building → dryer → powder machine → aggregate elevator bag dust collector → cold extraction → general distribution → finished product warehouse → central control room → wiring
3.3.4 Other work The construction season of asphalt pavement is mainly summer. In order to ensure the accuracy of electrical instruments such as electronic scales, lightning rods, arresters and other lightning protection devices need to be installed.

4 Comprehensive commissioning of asphalt plant
4.1 Conditions for debugging and trial production stages
(1) The power supply is normal.
(2) Fully equipped production and maintenance personnel enter the site.
(3) Calculate the amount of thermal oil used in each part of the mixing station, and prepare various lubricating greases.
(4) The reserves of various raw materials for the production of asphalt mixture are sufficient and meet the specifications.
(5) Laboratory testing and sewage treatment equipment inspection instruments required for on-site acceptance of equipment (mainly refer to the Marshall tester in the laboratory, rapid determination of oil-stone ratio, thermometer, round hole sieve, etc.).
(6) Test section where 3000t of finished materials are put.
(7) 40 20kg weights, totaling 800kg, are used for electronic scale debugging.