In the emulsified asphalt production system of road engineering, asphalt emulsifying equipment is the core equipment to realize asphalt water-based emulsification and prepare high-quality emulsified asphalt products, and colloid mill is the core unit of the whole set of emulsifying equipment.The key indexes such as particle size uniformity, storage stability, adhesive strength and workability of emulsified asphalt depend entirely on the grinding and shearing performance and operation accuracy of colloid mill.Compared with traditional stirring and pipeline emulsification devices, colloid mill completely solves the pain points of asphalt particles such as uneven dispersion, oil-water stratification and poor stability of finished products by virtue of its unique multi-stage shear grinding mechanism, which is the core guarantee for the production of standardized and high-quality emulsified asphalt and modified emulsified asphalt.This paper will give a comprehensive and detailed explanation of the special colloid mill for asphalt emulsification from the dimensions of structure composition, working principle, core advantages, classification and selection, operation and maintenance points and industry application.

Core positioning and working value of colloid mill

The essence of emulsified asphalt production is to crush high temperature viscous asphalt into micron fine particles by mechanical external force, and uniformly disperse them in aqueous solution containing emulsifier to form stable oil-water two-phase suspension system.Ordinary mixing equipment can only realize simple mixing of materials, but can not break the aggregation structure of asphalt macromolecules. The emulsified asphalt particles produced are coarse and uneven in size, and it is easy to cause layering and demulsification in a short time, which cannot meet the engineering construction standards such as road paving, sticky layer, permeable layer and slurry sealing layer.
As a special fine emulsification unit, the core function of colloid mill is to crush asphalt particles to standard particle size of 1-5μm through four physical actions of high speed shearing, high pressure extrusion, ultrafine grinding and homogeneous dispersion, and at the same time, let emulsifier evenly wrap asphalt particles, strengthen the oil-water interface adhesion, and fundamentally improve the stability, adhesion and durability of emulsified asphalt.It can be said that the performance of colloid mill directly determines the quality of emulsified asphalt, which is the core mark to distinguish low-end simple emulsification equipment from industrial standardized emulsification production line.

Asphalt emulsion colloid mill core structure composition

The colloid mill for asphalt emulsification adopts horizontal integrated precision structure, compact and wear-resistant, and can operate continuously. The core consists of five modules: drive system, precision grinding head assembly, bearing transmission system, gap adjustment system and sealing protection system. Each module works together to ensure high precision and high load emulsification operation.

Operated power system

The core is a special frequency conversion explosion-proof motor, suitable for asphalt high temperature, multi-moisture operating environment, power matching industrial grade emulsion production needs.The motor can achieve accurate speed control through frequency conversion speed regulation, and the normal working speed is stable at 3000-3600r/min, providing stable power for material shearing and grinding.Compared with ordinary fixed-speed motor, variable frequency drive can adjust the speed according to different production conditions such as ordinary emulsion and modified emulsion, taking into account production efficiency and finished product accuracy, and at the same time has the advantages of overload protection, noise reduction and energy saving.

Grinding head assembly (core working part)

Grinding head is the core of colloid mill operation, composed of rotor (dynamic grinding disc), stator (static grinding disc), grinding cavity, but also the highest precision, the most direct wear of the key components.
The rotor is a high-speed rotating component, made of high-chromium wear-resistant alloy material, forged and formed by numerical control precision grinding. The surface is designed with multi-layer trapezoidal tooth structure, which has high hardness, impact resistance and wear resistance, and can withstand high-intensity friction and shear of asphalt materials for a long time.The stator is a fixed part, coaxially nested with the rotor, and matched with the corresponding tooth groove inside to form a multi-stage annular shearing grinding channel.The meshing gap between rotor and stator is micron level, which is the core structure of superfine emulsification.
The grinding cavity is made of high quality stainless steel, corrosion resistance, high temperature resistance, can adapt to 130-140℃ high temperature asphalt material continuous processing, prevent the cavity corrosion pollution materials, ensure the cleanliness of the finished product.

Bearing drive system

High-precision and heavy-duty bearing set and integrated transmission shaft design, high transmission precision, strong operation stability, long-term high-speed rotation, high-load conditions, effectively reduce equipment vibration and noise.High-quality bearings have the characteristics of high temperature resistance, wear resistance and long service life, avoiding the problems of transmission shaft eccentricity and grinding head offset in long-term operation, ensuring uniform and stable rotor stator clearance, and eliminating the deviation of finished product particle size.

Precision clearance adjustment system

This is the core differentiation design of asphalt emulsion colloid mill, equipped with manual precision adjustment mechanism, which can accurately adjust the working gap between rotor and stator in shutdown state.The gap adjustment range can adapt to different production requirements such as ordinary emulsified asphalt and modified emulsified asphalt (SBS, rubber powder modification). The conventional emulsification mode and high-precision superfine emulsification mode can be switched through fine adjustment of gap, and the material standards of different projects can be flexibly adapted. The equipment has strong versatility.

Seal protection system

Mechanical seal + packing seal double protection structure, excellent sealing performance, can effectively prevent high temperature asphalt materials from infiltrating into the bearing cavity, avoid material leakage, bearing oil mixed into the finished product, at the same time prevent moisture, dust from entering the equipment, protect the transmission and bearing system, greatly reduce the equipment failure rate, prolong the service life of the whole machine.

Working principle of colloid mill emulsification

The asphalt emulsion colloid mill relies on the high-speed relative movement of the rotor and stator to form a unique shearing-extrusion-grinding-homogenization four-in-one operation mechanism. The whole process is continuous and automatic, and the material processing flow is stable and efficient.
Firstly, liquid asphalt preheated to process temperature and emulsifier aqueous solution with good proportion are mixed preliminarily by a premixer, and then enter a grinding cavity from a central feed port of a colloid mill.High speed rotating rotor drives high speed centrifugal movement of materials, so that materials quickly fill the micron slot channels of rotor and stator.
Under the high speed operation above 3000r/min, the material is subjected to extremely strong mechanical shear force, extrusion force, friction force and high frequency turbulent impact force between tooth structures, the asphalt macromolecular agglomeration structure is torn and broken instantly, and the large particle asphalt is ground and refined step by step.At the same time, the material flows from the center of the grinding disc to the edge along the radial S-shaped track, which prolongs the shear grinding path and realizes multi-stage repeated processing, so that the asphalt particles are uniformly refined to the standard micron level.
At the same time of mechanical refinement, emulsifier molecules are fully adsorbed and wrapped on the surface of asphalt particles, greatly reducing the interfacial tension between oil and water, preventing secondary agglomeration and sedimentation of asphalt particles, and finally forming emulsified asphalt products with uniform particle size, stable dispersion and good fluidity, which are discharged from the grinding head discharge port at a constant speed to complete the whole emulsification process.

Core Performance Advantages of Special Colloid Mill for Asphalt Emulsification

Compared with traditional emulsification equipment, colloid mill, as a core special unit, has irreplaceable advantages in finished product quality, production efficiency, equipment stability and other aspects, and is also the standard core of modern standardized emulsified asphalt production line:
1. the finis product has uniform particle size and high quality precision: through multistage shearing and grin, that particle size of the asphalt particles can be accurately controlled to be 1-5 mu m, the particle size distribution is uniform, no coarse particles exist, the problem of uneven particle size and demulsification layering of the finished product of common emulsifying equipment are thoroughly avoided, the storage stability of the finished product can reach more than 7 days, and the finished product can fully meet the construction standards of various road works.
2. the invention has wide adaptability and can be use for processing modify emulsified asphalt: that invention can adapt to the production of a plurality of products such as common emulsified asphalt, SBS modify emulsified asphalt, rubber powder modified emulsified asphalt, slow-cracking/fast-cracking emulsified asphalt and the like by adjusting the gap and the rotating speed of a grinding head, and meets the requirements of conventional engineering and high-standard maintenance engineering.
3. Continuous operation and high production efficiency: integrated continuous operation mode, uninterrupted feeding, emulsification and discharging, suitable for industrial batch production, with production efficiency increased by more than 30% compared with intermittent emulsification equipment, suitable for large-scale mixing station and centralized construction scene of engineering.
4. Wear-resistant and durable, low operation and maintenance cost: the core grinding head is made of high-hardness wear-resistant alloy material, which is wear-resistant, corrosion-resistant and high-temperature resistant, and is not easy to deform and wear during long-term operation, with low equipment failure rate.The precise adjustment structure is simple to operate and convenient to maintain, and the operation and maintenance cost in the later period is greatly reduced.
5. The finished product has excellent performance and good construction effect: the emulsified asphalt processed by the colloid mill has tight oil-water combination, high bonding strength and good permeability; after paving and molding, the pavement has high flatness, firm bonding, water damage resistance and strong durability, and effectively improves the road construction quality and service life.

Colloid mill common classification and selection basis 

According to the production conditions, capacity requirements and processing accuracy, asphalt emulsion colloid mill is mainly divided into two types: conventional type and high-precision modified type. The selection needs to be accurately matched in combination with engineering requirements: 

Conventional emulsion colloid mill 

It is suitable for the production of common cationic and anionic emulsified asphalt, with stable rotation speed, moderate gap adjustment range, high productivity and cost performance, meeting the basic construction requirements of ordinary sticky layer, permeable layer and sealing layer of roads, and adapting to small and medium-sized emulsion production lines. 

High-precision modified colloid mill 

For the development of modified emulsified asphalt, the grinding head tooth structure is more precise, the gap adjustment accuracy is higher, the rotation speed adjustable range is wider, the modifier particles can be fully broken and dispersed, and the modifier and asphalt are uniformly fused without agglomeration and precipitation. It is suitable for high standard road maintenance projects such as micro-surface, slurry seal layer and ultra-thin coating. 

Core basis for selection 

The main reference is three dimensions: one is the capacity demand, and the corresponding specification model is matched according to the daily output; the other is the product type, the ordinary emulsified asphalt is selected as the conventional model, and the modified emulsified asphalt must be selected as the high-precision model; the third is the working condition environment, the outdoor mobile production line can select the compact horizontal colloid mill, and the fixed large-scale production line can select the heavy-duty industrial model. 

Core points of daily operation and maintenance and fault handling 

Colloid mill belongs to precision mechanical unit, its operation status directly determines the quality of finished products, standard daily maintenance and fault handling is the key to ensure long-term stable operation of equipment. 

Daily maintenance points 

Before operation, check grinding head clearance, sealing state and belt tightness to ensure no looseness and leakage; after startup, no-load test run shall be conducted to observe whether equipment vibration and noise are normal before feeding operation. After the operation, the grinding head cavity must be washed with clean water in time, and residual asphalt materials must be cleaned to prevent the materials from drying and blocking the toothed channel and wearing the grinding disc. Regularly check bearing lubrication and seal wear, replace worn parts in time, regularly calibrate grinding head clearance, and ensure emulsion accuracy. 

Common faults and solutions 

(1) Coarse particles and poor stability of finished products: mostly caused by grinding head wear, excessive clearance or insufficient rotation speed, it is necessary to check and replace worn rotor stator, recalibrate grinding head clearance, and adjust motor running speed. 
(2) equipment vibration, abnormal noise: a large probability of bearing damage, eccentric transmission shaft or material jam, need to stop to check the bearing state, grinding head concentricity, clean up impurities in the cavity. 
(3) Material leakage: aging and wear of seals are the main reasons, and mechanical seals and packing seal components need to be replaced in time. 
(4) Productivity decline: cavity blockage, grinding head tooth surface scaling, abnormal speed caused by thorough cleaning of grinding head channel, troubleshooting motor frequency conversion system fault. 

Industry application and development trend 

At present, colloid mill has become the standard core unit of asphalt emulsion production line, widely used in highway municipal road construction, reconstruction and expansion, preventive maintenance projects, covering emulsified asphalt production, modified emulsified asphalt processing, asphalt recycled material pretreatment and other scenarios. With the continuous upgrading of road engineering quality standards, high-precision, intelligent and energy-saving have become the core development trends of colloid mills. 
The new generation of intelligent colloid mill is equipped with frequency conversion speed regulation system, automatic gap calibration system and operation status monitoring system, which can realize intelligent regulation of speed, gap and production capacity, monitor equipment vibration, temperature, load and other parameters in real time, have automatic fault warning function, greatly improve production automation level and finished product stability, and meet the needs of modern and standardized road engineering construction. 

Summary 

Colloid mill, as the core unit of asphalt emulsification equipment, realizes ultrafine refinement, uniform dispersion and stable emulsification of asphalt materials by virtue of its unique multi-stage shear grinding mechanism, which completely determines the finished product quality and engineering application effect of emulsified asphalt. Its precise rotor stator structure, flexible gap adjustment ability and stable continuous operation performance are the core advantages that ordinary emulsion equipment cannot replace. In the context of high-quality development of road engineering, precise selection, standardized operation, and scientific operation and maintenance of colloid mills can not only ensure that emulsified asphalt production quality meets standards, but also improve production efficiency, reduce equipment loss and construction costs, and improve the quality of road engineering construction. Provide core equipment support with long-term durability.