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Two 1000 MW coal-fired units at a certain company use a direct-fired coal grinding system, and the coal storage bins frequently get clogged when the quality of the coal is poor. Based on the practical experience from other projects of the client in China, methods such as traditional vibration motors, curved coal discharge hoppers, and rotating clog-clearing machines have all proven to be unsatisfactory. After careful consideration and based on the successful experiences gained from its use in other power plant projects within the group, it was decided to adopt the AirSweep intelligent cleaning and anti-clogging technology in its new projects. This has **reduced the frequency of blockages in the coal storage bins, improved the reliability of the coal grinding system, and prevented downtime caused by coal blockages in these bins. At the same time, it has **reduced the high investment costs associated with the use of curved coal discharge bins and rotary clogging removal devices. I. Current status of equipment in domestic power plant coal storage bins: In recent years, the supply of coal has had an impact on these systems. There is a shortage of low-quality coal, and its price is high. The so-called low-quality coal purchased is often a mixture of different types of coal, resulting in unstable coal quality, a high biomass content, small coal particles, and high moisture levels – all of which can easily lead to blockages in the coal storage bins. Additionally, since the coal storage areas are not fully enclosed, and during transportation they are subject to significant weather influences, especially during the rainy season, the moisture content in the coal increases and its viscosity rises, making it particularly easy for blockages to occur at the inlets and outlets of the coal storage bins. There are a wide variety of techniques used in China to address coal blockages in raw coal silos, but the effectiveness of these existing methods is not satisfactory; none of them can properly solve the problem of coal blockages at its root. Coal blockage in the raw coal bunker poses a series of hazards, such as reducing the output of the units and leading to a decrease in power generation; it can cause interruptions in fuel supply, forcing the units to use oil for combustion; in severe cases, if multiple coal feeders become blocked at the same time and the issue isn’t resolved in a timely manner, it will result in the units having to be shut down. Over the past two years, many power plants in China have been urgently seeking effective solutions to the problem of coal blockage in their raw coal silos. II. Introduction to the solutions for clearing blockages in raw coal silos: Currently, the main methods used in the market to address blockages in raw coal silos include vibration motors, rotary cleaning machines, air hammers, curved coal discharge silos, and shrimp-shaped silos. The first 3 methods can be used individually or in combination; they can help improve flowability when the raw coal has good flow properties. However, when the fluidity of the coal is poor, the clogging removal effects of the first three methods are limited, forcing the use of manual clearing methods. However, this method requires a long time to clear the obstruction, involves high risks, and has a poor working environment, making it an unsuitable solution. If the coal blockage is located at a high position, it is necessary to set up scaffolding for workers to carry out operations at heights, which poses safety risks; the effectiveness of clearing the blockage is limited, and it is time-consuming and labor-intensive. When knocking cannot resolve the issue, it is required to make holes in the walls of the raw coal bin, which causes significant damage to those walls, and the exposed raw coal piles can contaminate the environment. Method 1: Working principle of the vibrating motor: The vibrator uses vibrations from outside the container to stimulate the flow of materials; these vibrations break down friction, loosening the materials so that they can fall under the force of gravity. Its characteristics are as follows: * It acts on the outer wall of the silo, and the vibration forces can cause the silo to crack or deform ； * The sound is extremely loud; it is a distracting noise that damages the hearing of those present, creating a poor working environment ； * Vibration causes degassing and compaction of the material, which instead exacerbates the flow problems rather than solving them ； * Metal and weld fatigue can occur due to vibration or hammering, and the container needs to be repaired or replaced ； * High electricity costs ； * It is difficult to handle materials with high humidity, high viscosity, and high oil content effectively ； * In certain working environments, high-current power supply lines can be dangerous ； * Even after bridge construction, material sticking to and caking on the silo walls requires regular shutdowns for cleaning. The rapping motor method only works when there is a gap below the rapping point; otherwise, the material will become even more compact as a result of the rapping. The position of the vibrating hammer on the coal bin remains fixed, and this method is only suitable for situations where the flow rate is low or where the area below the vibration point is suspended. The vibrating motor generates significant vibration and noise, and it can sometimes cause the lining on the bin walls to loosen as well as metal fatigue, leading to the detachment of the vibrating motor and damage to the structure of the bin. Method 2: Working principle of the air hammer: The air hammer directs all the compressed air stored in the tank in a single direction toward a specific area. The released compressed air overcomes the static friction between the materials, allowing them to flow again. Its characteristics are as follows: * The released compressed air enters the pores between the materials, resulting in a reduction in energy; it may even create channels within the materials or compact them ； * The immediate release and descent of large amounts of material can cause damage to the equipment at the bottom of the silo, or even lead to the collapse of the silo ； * It is not possible to control the material flow rate; although the air hammer releases a large amount of energy, this energy release is uncontrollable ； * Due to direct blowing, the cleaning area is limited, making it impossible to effectively remove materials stuck to the walls, which can lead to cross-contamination ； * The open nozzle extends into the silo and the material, and dust or material may enter the nozzle and solenoid valve, forcing frequent shutdowns for cleaning as well as costly maintenance and replacement ； * Each time the air hammer is released, the recoil force is extremely large, leading to long-term fatigue and damage of the silo walls, thereby creating safety hazards ； * The noise is extremely loud and can spread throughout the entire production area, increasing the stress on workers ； * High gas consumption means high operating costs ； * The valve body is prone to mechanical failures and requires regular maintenance and repair ； * The effective impact of a single air hammer on the silo is limited; therefore, a larger number of them need to be installed, which increases costs ； * Pneumatic hammers are large in size and heavy in weight; their installation is complex. For silos with thin walls, the installation becomes even more difficult, and there are limitations regarding the space required for installation and use ； * For materials with high humidity, high viscosity, and high oil content, only voids can be blown out. Wet, sticky materials will still stick to the walls of the bin. Even with bridge control in place, the accumulation of material on the warehouse walls forces regular shutdowns for cleaning ； * Not suitable for food and hygiene applications ； * Pneumatic hammers are generally arranged facing each other on both sides of the coal hopper; when they move up and down to expand the cleaning area, compressed air is injected into the raw coal bin in an instant. Method 3: Working principle of the rotary clog remover: The rotary clog remover is essentially a scraping-type cleaning device; it is driven by a motor, with the reducer facilitating the rotation of the scraper. The rotary cutter and rotating cone form a spiral forced-conveying system that uses external force to forcibly change the flow pattern of the material within the bin, thereby restoring the material flow from a central flow to a uniform flow. Its main features are as follows: * It is only applicable to cylindrical coal bins and coal drop pipes; irregular shapes such as squares cannot be used. * It can only address partial blockages in the coal bin or chute; it is ineffective against the coal piled up in the upper areas. The range of cleaning is limited, and there are dead zones that make it difficult to clean thoroughly, resulting in poor cleaning effects for the entire coal bin or chute. It needs to be used in conjunction with other cleaning devices such as air hammers or vibration devices. * Additionally, when the scraper is located in the coal bin or chute, it becomes a cause of coal blockage, especially when arching does not occur; this reduces the flow area and increases flow resistance, leading to more internal blockages and making coal blockage more likely. * Installation, modification, and design are complex; the coal bin requires an additional storage area as well as components designed to prevent blockages, which demands substantial driving power. The structural dimensions of the rotating bin also increase, raising manufacturing costs, and thorough design and calculation are necessary. Since the anti-clogging blade has a cantilever structure, it requires high rigidity and strength; a large and rigid geometric structure is needed to meet its operational requirements, which results in a long renovation period. * The mechanism is complex, requiring significant maintenance efforts; the drive gears need to be lubricated regularly, and the seals and scrapers must be replaced periodically ； * Maintenance is difficult; replacing seals and scrapers is challenging and carries high risks. It is necessary to empty and clean the coal bin or chute before entering to replace the scrapers and seals. Moreover, maintaining and replacing components such as the reduction gearbox and support bearings is extremely difficult, requiring lifting equipment to carry out the work. The components wear out rapidly, resulting in heavy maintenance workload and high maintenance costs. * It has a high failure rate, and the cantilever structure is prone to scraper-related issues such as bending and deformation, as well as problems with the gearbox. At the outlet end of the shrimp-shaped coal hopper in the shrimp-bin & curved coal feeding bin, as well as above the conveyor belt of the coal feeder, coal flow shaping devices are installed to create a proper guiding channel area. These devices address the issues of coal spillage caused by the skirt baffles at the discharge outlet and the frequent changes in the shape of the coal flow, allowing the coal flow to take on a natural shape. As a result, the shape of the coal flow becomes more regular, stable, and uniform, making it easier to adjust and facilitating transportation by the conveyor belt. Its characteristics are as follows: • Complex design: The cross-sectional design of the shrimp-shell curve coal bin is circular or nearly circular; after fabrication, it is divided into curved sections and vibrating sections. Computer-based analysis and simulation are combined with practical experience in parameter setting, and this complex design increases the difficulty of manufacturing and installation. • High cost: Due to the complex design and manufacturing process of the Shrimp Curve coal bin, the associated costs increase, which may pose an economic burden on users with limited budgets. • Difficult maintenance: The design characteristics of the Shrimp Curve coal bunker result in complex maintenance requirements; professional technicians are needed to carry out regular inspections and upkeep to ensure its proper operation. • There is a risk of coal clogging: Although the shrimp curve coal bin design is intended to reduce coal clogging, in practice, various types of coal are used, and especially when dealing with raw coal that is sticky, prone to agglomeration, and high in moisture, there remains a risk of coal clogging. Although the shrimp-shell curve coal bin has certain advantages in preventing coal blockage, its main disadvantages are its complex design, high cost, difficulty in maintenance, and the potential risk of coal blockage. Recommended method: Working principle of AirSweep intelligent cleaning and anti-clogging technology – A simulation model is designed based on the actual conditions, and controlled pulse forms and energies such as radial flow and impact flow are strategically utilized to effectively activate a specific area and angle, thereby achieving uniform flow within the silo. Its main features are as follows: * Simulation model design is carried out on-site, with controlled pulse forms and energies such as radial flow and impact flow being strategically utilized to achieve effective activation within a specific range and at certain angles, without affecting the natural gravity flow of the existing materials, thereby facilitating overall flow within the silo. * There are no restrictions on the installation of this application; it is suitable for the vast majority of silos or chutes, regardless of their size or shape. It can be easily installed on flat or curved surfaces, and no specific wall thickness is required. Installing the modules against the wall does not interfere with the normal flow of coal within the silo or chute. * It has broad applicability and is not affected by spatial location, equipment type, or the materials stored in the warehouse. The pulse module can be installed at any location in the coal bin or chute; it operates continuously, effectively preventing sticking to the walls, ensuring the flow of materials, keeping them in an active state, and at the same time enabling the removal of arch-shaped coal blockages. * Installation, modification, and maintenance are simple – all that is required is to make an opening on the outside of the warehouse wall; no other complex supporting systems or power systems are needed. The modification process is quick, and there is no need to empty the warehouse or interrupt production. * It starts up quickly and operates with high efficiency. First in, first out to achieve 100% clearance. * It controls and adjusts the discharge flow rate, making efficient use of the storage capacity, and can be combined with on-site operations to perform functions such as wall cleaning, mixing, and crushing. * Channel simulation design to achieve energy optimization and prevent internal damage caused by backflow, dust, etc. * It exerts no recoil on the container, and can be easily installed on materials such as metal, concrete, fiberglass, and plastic. * With an operating temperature exceeding 800°C, it can be properly used in harsh environments such as those with liquids. * Durable and robust, with almost no moving parts, resulting in low maintenance costs*. It poses no noise hazard, ensuring the safety of employees*. It comes with a 36-month warranty, is imported directly from the United States, and is designed to last over twenty years. III. Case Study: A renovation project at a power plant belonging to an energy group. The customer’s original coal storage bins were designed using a hyperbolic shape; however, due to the high viscosity and high humidity of the material (high-moisture lignite with a high content of biomass, as shown in the diagram), problems such as material sticking to the walls and blockages occurred frequently. Later, the owner modified its raw coal silo by adding a transitional coal silo, and equipped it with air hammers, rotary clogging removal machines, slide gates, as well as rotary clogging removal devices for coal discharge pipes. However, after the renovation, sticking and arching problems still existed over a large area in the coal bin and its bottom cone section; it is necessary to regularly empty the coal bin for cleaning, otherwise coal spillage will occur. The raw coal bin is designed in a hyperbolic shape, with a rotating block-clearing machine installed at its bottom; an air hammer is placed above this rotating machine. The raw coal in question is lignite, which has a high biomass content and high humidity. Under the action of the scraper of the rotating block-clearing machine and external forces, the raw coal becomes more compact, resulting in reduced fluidity. This increases the workload on the rotating block-clearing machine, leading to motor damage and broken scrapers. Additionally, the obstruction of the coal flow by the scraper creates new flow problems in the upper part of the machine, and an air hammer cannot resolve these issues. We designed the model based on on-site conditions, and provided a targeted AirSweep intelligent cleaning and anti-clogging solution. After the AirSweep intelligent cleaning and anti-clogging system was installed and put into operation, the temperature of the coal bin walls equipped with this system remained around 55 degrees, indicating that the anti-clogging device was functioning effectively; the coal in the bin remained in motion and did not compact, staying in an active state throughout. The gradual decrease in the temperature of the coal bin walls, where the AirSweep intelligent cleaning and anti-clogging system is not installed, indicates that the material inside the bin is gradually compacting and thickening. In coal bins that do not have the AirSweep intelligent cleaning and clog-prevention system, the coal grinding system must be shut down after at most 4 days of operation; the coal bin needs to be emptied so that the coal stuck in it can be cleared manually, otherwise problems with coal accumulating on the upper part of the bin will occur. The coal bin, equipped with the AirSweep intelligent cleaning and anti-clogging system, can operate for extended periods of time. To date, no coal clogging incidents have occurred since the customer installed the system, and it is operating stably. Installed in July 2020, this system has so far completely resolved the problem of coal blockage in the original coal storage bin. During the 4 years that the system was in operation, its performance remained stable, and the AirSweep intelligent cleaning and clog-prevention system required no maintenance or replacement. **For a new construction project at one of the power plants owned by an energy group, the client is building 2x1000MW units on-site; there are 2 boilers, with each boiler equipped with 6 raw coal storage bins, resulting in a total of 12 raw coal storage bins at the site. The customer has tried various different methods for clearing blockages in the raw coal silos of other power plants in the country, but with limited success; the issue of coal blockages has thus become a challenge in the production process. This is a new project, but prior to its implementation, the client had already installed our AirSweep intelligent cleaning and anti-clogging system in other power plants within the group, and was very satisfied with its performance and stable operation. The AirSweep intelligent cleaning and clog-prevention system employs simulation model design based on actual conditions, and strategically uses controlled pulse forms such as radial flow and impact flow along with appropriate energy levels. This approach enables effective activation within specific areas and at certain angles, without affecting the natural gravity-driven flow of the materials, thus facilitating overall fluid movement within the silo. It addresses the issue of material flow at its root; this technology also reduces the design requirements for the structure of the raw coal silo, thereby lowering customer costs as well as subsequent operation and maintenance expenses. Since the commissioning of Unit 1 by the customer in July 2022, there has been no occurrence of coal blockage in the coal bin, the operation at the site has been stable, and customer satisfaction is high.