I. Introduction

In the process of coal production and storage, coal bunkers—key storage facilities—play a crucial role in ensuring the stability of the coal supply chain. However, coal bunkers that have been in use for extended periods often face the challenging issue of coal buildup. Such buildup not only occupies valuable storage space within the bunker, reducing the amount of coal that can be stored, but also may lead to coal clumping and blockages, severely affecting the smooth discharge and transportation of coal and thereby disrupting the continuity of the entire production process. For instance, at some thermal power plants, coal-bunker buildup has previously caused interruptions in coal supply, forcing generating units to operate at reduced load or even shut down for maintenance, resulting in substantial economic losses and increased operational pressures for the enterprises.

Traditional coal bunker cleaning methods, such as manual cleaning, although relatively low in cost, are inefficient and involve harsh working conditions that pose significant health risks to workers. Mechanical cleaning methods, on the other hand, require large-scale equipment, which is costly and may cause some degree of damage to the internal structure of the coal bunker. The emergence of pneumatic coal-bunker cleaning equipment has provided an efficient, safe, and cost-effective solution to the problem of coal accumulation in bunkers. Thanks to its unique operating principle and distinct advantages, this technology is gradually gaining prominence in the field of coal-bunker cleaning and has become a focal point of attention and application for many coal enterprises.

II. Working Principle of Pneumatic Tank Cleaning Equipment

Pneumatic coal-cleaning equipment primarily uses the powerful energy of compressed air to drive cleaning tools, enabling efficient removal of accumulated coal in coal bunkers. The core working principle is as follows:

Compressed air, generated by an air compressor, is conveyed through pipelines to the power unit of the pneumatic coal-cleaning equipment. In the power unit, the energy of the compressed air is converted into mechanical energy, driving cleaning tools such as rotating scrapers, impact hammers, or air-jet nozzles to operate at high speeds. For example, under the propulsion of compressed air, the rotating scraper rotates at high speed and cuts into the accumulated coal. With its sharp blades, it breaks up and scrapes off the caked coal from the bin walls. The impact hammer, on the other hand, uses repeated impacts to loosen and disintegrate hard coal chunks, making them easier to remove during subsequent cleaning operations. The air-jet nozzle, meanwhile, emits a high-speed, high-pressure airflow that strikes and blows clean the surface of the accumulated coal, dislodging loose coal particles and directing them toward the discharge port of the coal bin, where they can be smoothly discharged outside the bin.

Compared with other cleaning methods, pneumatic coal-cleaning equipment offers significant advantages. On the one hand, compressed air serves as the power source, eliminating the safety risks that electrical equipment might pose in a coal bunker—a space prone to fire and explosion—and thereby greatly enhancing the safety of the cleaning operation. On the other hand, pneumatic equipment features a relatively simple structure with fewer components and low wear rates. This not only reduces the equipment’s failure rate but also makes maintenance and repair easier, effectively minimizing downtime and maintenance costs. Moreover, pneumatic coal-cleaning equipment can flexibly adapt to the complex structures within coal bunkers and varying degrees of coal accumulation. By adjusting the pressure and flow rate of compressed air as well as the operating parameters of the cleaning tools, it can precisely remove coal buildup of different shapes and hardnesses, ensuring thoroughness and efficiency in the cleaning process.

III. Types and Characteristics of Pneumatic Depot-Cleaning Equipment

(1) Air Cannon Type

The air cannon is a common and highly efficient pneumatic equipment used for clearing coal bunkers. Its main components include an air chamber, nozzles, ducts, and control valves. During operation, the air cannon rapidly fills the air chamber with compressed air via a control valve, causing the pressure inside the chamber to rise sharply within a very short time. Once the pressure reaches the preset level, the control valve instantly opens, allowing the high-pressure air from the chamber to be ejected through the nozzles at high velocity and with tremendous force, directly targeting the arch foundations or blocked areas where coal has accumulated in the bunker. The sudden release of this compressed air generates an intense shock wave that effectively breaks down the compacted structure of the coal, loosening and collapsing clumped coal masses, thereby restoring the bunker’s normal discharge function. For example, during bunker-cleaning operations at a large coal mine, the installed air cannons—with their powerful impact—successfully resolved a severe blockage caused by long-term coal accumulation, significantly increasing the coal-unloading speed and improving the utilization rate of the bunker. Air cannons are characterized by their strong impact force and remarkable clogging-clearing effectiveness, making them suitable for various large-scale coal bunkers as well as situations involving severe coal accumulation and high degrees of blockage. Their effective working range is relatively large, enabling them to act on extensive areas of accumulated coal in an instant, quickly breaking through material blockages and ensuring smooth coal discharge from the bunker.

(2) Pneumatic Jackhammers

The pneumatic rock drill consists primarily of components such as the air distribution mechanism, the impact mechanism, and the drill bit. Its working principle is based on using compressed air to drive a piston back and forth within a cylinder, thereby causing the drill bit to perform high-frequency impact movements. When compressed air enters the cylinder of the rock drill, it pushes the piston forward, causing the tip of the drill bit to strike and break up the accumulated coal inside the coal bunker. After the piston reaches a certain position, changes in pressure within the cylinder and the action of the air distribution mechanism cause it to rapidly move backward, preparing for the next impact cycle. In small coal bunkers or during localized cleaning operations within coal bunkers, the pneumatic rock drill can demonstrate its unique advantages. For example, when small chunks of accumulated coal block the discharge outlet of a coal bunker or when localized areas of the bunker’s inner walls have coal that has adhered tightly, operators can hold the pneumatic rock drill in their hands and precisely clean these specific areas. The advantages of this tool include its flexible operation and high precision, enabling targeted cleaning tailored to the actual conditions of accumulated coal without unnecessarily disturbing other parts of the bunker. However, the pneumatic rock drill also has certain limitations: its cleaning efficiency is relatively low, making it less effective for large-scale or highly hardened accumulations of coal; moreover, the labor intensity for operators is quite high, as they must hold the rock drill in their hands for extended periods, which can easily lead to fatigue.

(3) Guangzhou Daisler Pneumatic Clinker Cleaning Equipment GIRONET & POWERNET

GIRONET & POWERNET is widely used abroad for cleaning warehouses and silos of various materials, including cement, steel, energy, minerals, lime, food, and other industries. It is today’s safe and efficient pneumatic warehouse-cleaning equipment. The device operates using compressed air and features a high-performance pneumatic cleaning motor paired with a robust, specially designed aluminum articulated arm. The equipment is installed atop the warehouse, allowing personnel to access the interior of the warehouse via remote control of the specialized aluminum articulated arm and the pneumatic cleaning motor—without needing to enter the warehouse themselves.

Main features:

• Safe and efficient—no need for personnel to risk entering the warehouse interior for mechanical operations. Depending on the powder characteristics, the maximum cleaning rate can reach up to 100 tons per hour.

• The ingenious design and precise positioning of the non-destructive storage bin ensure its seamless bin walls and linings.

• No need to halt or shut down production—equipment operates from the top of the warehouse inventory, eliminating the need for you to stop or suspend operations.

• Economically reasonable one-time investment; just 1-2 people can efficiently complete installation and cleaning operations.

IV. Summary of Advantages of Pneumatic Dust-Cleaning Equipment

(1) Efficiency

Compared to traditional manual cleaning methods, pneumatic coal-cleaning equipment has significantly boosted work efficiency. Take the air cannon as an example: its powerful impact force can instantly disrupt the compact structure of coal accumulations, causing the accumulated coal to quickly loosen and collapse. In contrast to manually shoveling coal bit by bit, this approach dramatically increases the cleaning speed. In some large-scale coal-storage facility cleaning projects, after adopting pneumatic coal-cleaning equipment, the cleaning time has been reduced by several times—or even dozens of times—greatly minimizing downtime at coal storage facilities, enhancing coal production and transportation efficiency, and generating greater economic benefits for enterprises.

(2) Safety

Safety is of paramount importance in industrial production, and pneumatic hopper-cleaning equipment offers significant advantages in this regard. Since it uses compressed air as its power source, it eliminates the risk of electrical sparks—potential safety hazards that could be triggered by electrical equipment in flammable and explosive environments such as coal bunkers—thereby reducing the likelihood of fires and explosions. At the same time, operators do not need to enter the coal bunker directly to carry out cleaning operations, effectively avoiding injuries caused by factors such as coal collapses, gas leaks, and dust poisoning, thus providing reliable protection for the safety of workers' lives.

(3) Environmental friendliness

Today, as environmental protection requirements become increasingly stringent, the eco-friendly performance of pneumatic coal-cleaning equipment is receiving growing attention. During the cleaning process, through rational design and operational practices, this equipment can effectively minimize dust generation, thereby preventing coal dust from polluting the surrounding environment. Meanwhile, thanks to its precise cleaning capabilities, the equipment reduces coal spillage and waste during the cleaning process, lowering the potential risk of pollution to land and water resources and aligning with the eco-friendly principles of sustainable development.

(4) Flexibility and Precision

The structure and coal accumulation conditions of coal bunkers are often complex and varied, and pneumatic coal-cleaning equipment is well-suited to handle this complexity. By adjusting the pressure and flow rate of compressed air and selecting different types of cleaning tools and equipment combinations, operators can flexibly develop customized cleaning plans tailored to specific factors such as the bunker’s actual shape and size, as well as the hardness and thickness of the accumulated coal. This allows for precise cleaning of every part of the coal bunker. Whether it’s narrow corners, high-up accumulations, or hard clumps at the bottom, all these areas can be effectively addressed, ensuring that the coal bunker achieves optimal cleaning performance.

V. Precautions and Maintenance Tips for Application

(1) Safe Operating Procedures

The safety awareness and operational skills of operators are critical factors in ensuring the safe operation of pneumatic hopper-cleaning equipment. Before putting the equipment into service, operators must undergo comprehensive and systematic training to gain a deep understanding of the equipment’s operating principles, procedures, safety precautions, and emergency response measures. Only after passing the assessment can operators be authorized to operate the equipment, thereby preventing safety incidents caused by improper operation.

Before each use of pneumatic hopper-cleaning equipment, it is essential to thoroughly inspect all components of the equipment, including the tightness of connection points, the integrity of seals, and the wear condition of cleaning tools. This ensures that the equipment is free of potential faults and can operate normally. Meanwhile, operators must be equipped with complete and qualified personal protective equipment, such as hard hats, safety goggles, earplugs, dust masks, work uniforms, and safety shoes, to effectively guard against injuries caused by dust, noise, flying debris, and other hazards that may arise during equipment operation.

During the cleaning operation, it is necessary to monitor the gas environment inside the coal bunker in real time, with particular attention paid to key indicators such as oxygen content, methane concentration, and carbon monoxide concentration, ensuring that these parameters remain within safe limits. If any abnormal gas concentrations are detected, operations must be immediately halted, and appropriate measures—such as ventilation, air exchange, and gas dilution—must be taken promptly. Only after the gas environment has returned to normal can the cleaning work resume. We must firmly prevent serious accidents, such as poisoning or explosions, caused by gas leaks.

(2) Equipment Maintenance and Servicing

Daily maintenance inspections are the foundational work for ensuring the long-term stable operation of pneumatic ash-cleaning equipment. After using the equipment, promptly clean away accumulated dust, coal slag, and other debris from its surface to keep it clean and prevent foreign objects from entering the equipment interior and disrupting its normal operation. Conduct a detailed inspection of the equipment’s connection points, pipelines, valves, and other components to check for looseness or air leaks. If any issues are found, tighten connections or replace seals immediately. Regularly inspect and clean the wear condition of cleaning tools—for example, the degree of blade wear on scrapers or the condition of the impact hammer heads. When wear exceeds the specified limits, replace these parts promptly to ensure effective cleaning performance and maintain the equipment’s operational efficiency.

Some wear-and-tear parts in pneumatic dust-cleaning equipment—such as seals, filter elements, and nozzles—are prone to issues like wear, aging, and clogging after prolonged use, necessitating regular replacement. The specific replacement cycle should be determined comprehensively based on factors such as the equipment’s usage frequency, working environment, and operating parameters. Generally speaking, seals can be replaced every [X] months, filter elements every [X] months, and nozzles should be inspected every [X] months and replaced according to their actual condition of wear.

As the power source for pneumatic hopper-clearing equipment, the compressed air system’s stable operation is of paramount importance. Regular maintenance and servicing of the air compressor are essential, including checking the oil level and quality of the lubricating oil. If the oil quality has deteriorated or the oil level is insufficient, it should be promptly replaced or topped up. The air filter must also be cleaned regularly to prevent dust and other impurities from entering the compressor and disrupting its normal operation. Additionally, the tension of the compressor’s belt should be checked to ensure efficient power transmission. At the same time, the compressed air pipelines should be inspected for any signs of air leakage; if leaks are detected, they should be repaired immediately. Furthermore, the pipelines should be periodically purged to remove accumulated dust and moisture, ensuring that the compressed air remains dry and clean, thereby providing a stable and reliable power supply for the equipment.

In addition to routine maintenance inspections and replacement of wear-and-tear parts, pneumatic hopper-cleaning equipment should also undergo comprehensive inspections and maintenance on a regular basis. This includes disassembling, cleaning, lubricating, and adjusting the equipment’s mechanical components to ensure smooth operation and eliminate any jamming or sticking phenomena. Furthermore, the electrical control system must be inspected and tested to verify that its control functions are operating properly and signal transmission is accurate. The equipment’s overall performance—such as cleaning efficiency, impact force, and airflow velocity—should be thoroughly tested and evaluated. Based on the test results, appropriate adjustments and optimizations should be made to keep the equipment in optimal working condition, thereby extending its service life, enhancing its reliability and stability, and providing strong assurance for the safe and efficient cleaning of coal bunkers.

VI. Conclusion and Outlook

The application of pneumatic coal-cleaning equipment in coal storage facilities offers significant advantages and value. Thanks to its unique operating principle and diverse equipment types, it can efficiently, safely, and environmentally responsibly address the issue of coal buildup in coal bins, thereby enhancing the efficiency of coal production and transportation, reducing operational costs and safety risks for enterprises, and aligning with modern industrial requirements for environmental protection and sustainable development.

However, current pneumatic ash-cleaning equipment still has some areas that need improvement and refinement. For example, the cleaning efficiency of certain devices could be further enhanced, especially when dealing with large coal bunkers and situations where coal accumulation is extremely complex. Moreover, the durability and stability of some equipment still require further enhancement to reduce failure rates and maintenance frequency in harsh working environments. In addition, the level of智能化 (smartification) of these devices remains relatively low, and their operation and maintenance still rely heavily on human expertise.

Looking ahead, with the continuous advancement and innovation of technology, pneumatic hopper-cleaning equipment is poised to achieve breakthroughs and development in the following areas: First, in terms of equipment design and manufacturing, we will adopt more advanced materials and processes to enhance performance and reliability, thereby extending the service life of the equipment. Second, we will further boost the automation and intelligence levels of the equipment by integrating sensor technologies, automated control systems, and artificial intelligence algorithms, enabling remote monitoring, autonomous operation, and fault diagnosis. This will reduce the difficulty and risks associated with manual operations, while improving the precision and efficiency of cleaning tasks. Third, we will continue to optimize the energy efficiency of the equipment, exploring more energy-saving and environmentally friendly methods for generating and utilizing compressed air, thus reducing energy consumption and minimizing environmental impact. Fourth, we will expand the application scope and scenarios of pneumatic hopper-cleaning equipment beyond just coal storage facilities in the coal industry. The equipment can also be applied to the cleaning of other similar storage facilities that handle powdery or granular materials, such as grain storage, cement storage, and chemical raw material storage, providing efficient and reliable cleaning solutions for material storage and transportation across a wider range of industries.