Blockage and arching of materials is a common and inevitable problem in silos. To solve such a problem in a safest, most energy-saving and fastest way, an advanced and ideal device is needed to be installed to ensure the continuity of the production process. Likewise, raw coal clogging is also a common problem occurring in raw coal silos in thermal power plants. Such a blockage may cause many forms of harms, for example, it may decrease the output of the coal pulverizer, or cause spontaneous combustion or even explosion.
Our dredging equipment including air cannons and loosening machines have been in use in a number of power plants. These devices have advantages of high automation, low maintenance and outstanding dredging effects, and can be substituted for many ways of preventing arching and assisting in flow which are ineffective, unsafe and high-cost, such as hand pounding, explosion, mechanical vibration, or grinding plates. The dredging equipment can not only reduce the labor intensity and ensure the production safety, but also bring economic benefits to the users. Moreover, it is eco-friendly and pollution-free, and is recognized as the safest, most advanced, economical and idea device to prevent arching and assist in flow.
Features
Air cannon (also known as air blaster or dredging device) works by creating a sudden violent blast of compressed air, and making it directly rush into the blockage area at over one Mach (velocity of sound). The sudden release of such shock wave avoids the static friction within materials and restores the flow of the materials in the container. It adopts the aerodynamic principle, and involves a differential pressure device and an automatically controlled fast exhaust valve to convert air pressure into jet power and blasting force. It is an ideal dredging or ash-removing device that is clean, pollution-free and low energy-consumption.
The air cannon has the basic advantages of simple structure, high impact force, safety, energy saving, automatic control, simple operation, and no harm to hoppers.
※ High blasting speed; destroy the bridges effectively and thus to eliminate the blockage;
※ Combined air cannon which can produce a large blasting force;
※ Create low noise and no pollution;
※ No leakage design which ensures an efficient use of energy;
※ Avoid compressing raw materials in the silos;
※ Minimum maintenance: maintenance can be done by simply moving parts and components, with no lubrication required. It involves no motors and no bearings;
※ Create a strong blast which has effects within a vast area;
※ Include a special reset device that ensures the automatic reset of the piston, thus prevent materials in the silo inversely enter into the air cannon;
※ Long service life; the parts are free for maintenance within one year.
Air cannon (also known as air blaster or dredging device) works by creating a sudden violent blast of compressed air, and making it directly rush into the blockage area at over one Mach (velocity of sound). The sudden release of such shock wave avoids the static friction within materials and restores the flow of the materials in the container. It adopts the aerodynamic principle, and involves a differential pressure device and an automatically controlled fast exhaust valve to convert air pressure into jet power and blasting force. It is an ideal dredging or ash-removing device that is clean, pollution-free and low energy-consumption.
The air cannon has the basic advantages of simple structure, high impact force, safety, energy saving, automatic control, simple operation, and no harm to hoppers.
※ High blasting speed; destroy the bridges effectively and thus to eliminate the blockage;
※ Combined air cannon which can produce a large blasting force;
※ Create low noise and no pollution;
※ No leakage design which ensures an efficient use of energy;
※ Avoid compressing raw materials in the silos;
※ Minimum maintenance: maintenance can be done by simply moving parts and components, with no lubrication required. It involves no motors and no bearings;
※ Create a strong blast which has effects within a vast area;
※ Include a special reset device that ensures the automatic reset of the piston, thus prevent materials in the silo inversely enter into the air cannon;
※ Long service life; the parts are free for maintenance within one year.
Principal Causes and Forms of Material Blockage in Silos
At present, raw coal silos of thermal power plants in China are mostly constructed by cement, steel, or concrete, adopting similar structures like cylindrical shapes, or square tapered, conical and hyperbolic shapes at the lower part. The structure comes with a larger opening at the upper part for feeding and a smaller opening at the lower part for discharging, which allow materials to flow from the top down. As the falling materials flow downwards in the conical container, it will enter into places with smaller cross-sectional areas where the materials will be squeezed and encounter increased friction. This is the main reason for blockage. Furthermore, many factors may also lead to clogging, including water content, granularity, temperature changes, long storage period of materials, and increased friction coefficient between container walls and materials. At present, clogged silos come in shapes of arch, parabola, and fireplaces. The blockage places are mostly within the areas 1.5-3.5 m up from the material gate (but not limited to these areas), where the materials start to stick to the wall to form a thin layer and consequently increase the frictional force. The layer then extends in both the axial and radial directions and becomes thicker. Finally, blockage and stoppage of flow will happen.
Materials in a variety of silos may induce arching or blockage in many forms due to the moisturized or long-term storage. In order to fit different applications, our company provides a wide range of air cannons as follows:
1. The air cannons with a volume of 50 L or 75 L are mainly applicable in the silos where the materials have a low specific gravity or good fluidity, or the silos with a low storage volume and a low cross-sectional area. Such places include granaries, storage bins of saw dusts and plastic particles, ash storage bins, small-sized cement storage bins and materials conveying pipes.
2. The air cannons with a volume of 75 L, 100 L or 150 L are mainly applicable in small and medium sized silos for general materials, for example, storage bins for chemicals, cement, foundry sand, small-sized truck loading gates, or small-sized waste rock bins.
3. The air cannons with a volume of 150 L or 300 L are mainly applicable in silos where the materials have a high specific gravity, or the silos with a large storage volume but a low cross-sectional area, or where there is poor fluidity and solidification tends to occur. For example, all kinds of medium-sized truck loading coal bins, large-volume raw coal bins, buffer silos, and small-sized fine ore bins.
4. The air cannons with a volume of 500 L are mainly suitable for applications in large-sized coal bins and fine ore bins with a high specific gravity and other special purposes.
At present, raw coal silos of thermal power plants in China are mostly constructed by cement, steel, or concrete, adopting similar structures like cylindrical shapes, or square tapered, conical and hyperbolic shapes at the lower part. The structure comes with a larger opening at the upper part for feeding and a smaller opening at the lower part for discharging, which allow materials to flow from the top down. As the falling materials flow downwards in the conical container, it will enter into places with smaller cross-sectional areas where the materials will be squeezed and encounter increased friction. This is the main reason for blockage. Furthermore, many factors may also lead to clogging, including water content, granularity, temperature changes, long storage period of materials, and increased friction coefficient between container walls and materials. At present, clogged silos come in shapes of arch, parabola, and fireplaces. The blockage places are mostly within the areas 1.5-3.5 m up from the material gate (but not limited to these areas), where the materials start to stick to the wall to form a thin layer and consequently increase the frictional force. The layer then extends in both the axial and radial directions and becomes thicker. Finally, blockage and stoppage of flow will happen.
Materials in a variety of silos may induce arching or blockage in many forms due to the moisturized or long-term storage. In order to fit different applications, our company provides a wide range of air cannons as follows:
1. The air cannons with a volume of 50 L or 75 L are mainly applicable in the silos where the materials have a low specific gravity or good fluidity, or the silos with a low storage volume and a low cross-sectional area. Such places include granaries, storage bins of saw dusts and plastic particles, ash storage bins, small-sized cement storage bins and materials conveying pipes.
2. The air cannons with a volume of 75 L, 100 L or 150 L are mainly applicable in small and medium sized silos for general materials, for example, storage bins for chemicals, cement, foundry sand, small-sized truck loading gates, or small-sized waste rock bins.
3. The air cannons with a volume of 150 L or 300 L are mainly applicable in silos where the materials have a high specific gravity, or the silos with a large storage volume but a low cross-sectional area, or where there is poor fluidity and solidification tends to occur. For example, all kinds of medium-sized truck loading coal bins, large-volume raw coal bins, buffer silos, and small-sized fine ore bins.
4. The air cannons with a volume of 500 L are mainly suitable for applications in large-sized coal bins and fine ore bins with a high specific gravity and other special purposes.
Note
1. The device demonstrates different features depending on different properties of materials, and so it is with the skinning and blockage of silos. Accordingly, the required number of air cannon units varies widely. In general cases, the finer the powder, the more difficult the dredging is. Meanwhile, bulk materials are difficult to be removed in cases of clogging due to meshing.
2. The silos come in round or square shapes. In the case of square silos, the length of the diagonal is regarded as the diameter.
3. The air cannon with a large volume is needed for the following materials stored in silos: 1) Highly adhesive powdery materials; 2) Agglomerate materials that may induce meshing; 3) Solidified materials due to long-term storage; 4) Materials stored in silos that have a low taper angle or a narrow exit; 5) Materials with excellent moisture absorption capability or fluidity, or high sensitivity to temperature.
4. In applications where explosion-proof requirement exists, a gas control valve or an electric control explosion-proof quick exhaust valve is required to be installed.
1. The device demonstrates different features depending on different properties of materials, and so it is with the skinning and blockage of silos. Accordingly, the required number of air cannon units varies widely. In general cases, the finer the powder, the more difficult the dredging is. Meanwhile, bulk materials are difficult to be removed in cases of clogging due to meshing.
2. The silos come in round or square shapes. In the case of square silos, the length of the diagonal is regarded as the diameter.
3. The air cannon with a large volume is needed for the following materials stored in silos: 1) Highly adhesive powdery materials; 2) Agglomerate materials that may induce meshing; 3) Solidified materials due to long-term storage; 4) Materials stored in silos that have a low taper angle or a narrow exit; 5) Materials with excellent moisture absorption capability or fluidity, or high sensitivity to temperature.
4. In applications where explosion-proof requirement exists, a gas control valve or an electric control explosion-proof quick exhaust valve is required to be installed.
Operation of Air Cannon
The air cannons allow easy operation. It can either be operated manually or pneumatically for each single unit, or electrically for each unit or a combination of units, or automatically at a setting time. For operation, open the ball valve to allow the inflow of air into the air cannon; when the blasting is needed, press the start button to deliver a pulse signal or a gas signal to the quick discharge valve. After that, the air cannon release a strong blast through the air outlet completely, and then return to the state of air pressure automatically. This cycle will repeat again at any time on request. The manual operation is to perform the operation through the control button or by using the small handle on the change valve, and the automatic operation is to perform the action through an automatic control device. The control system can also involve a PLC to control the operation through the entire process. The operator is allowed to either control the sequence of the operation steps by pressing the buttons on the control panel, or control a single unit of air cannon in a separate way. This safe automatic system enables the unattended operation of the air cannons.
The air cannons allow easy operation. It can either be operated manually or pneumatically for each single unit, or electrically for each unit or a combination of units, or automatically at a setting time. For operation, open the ball valve to allow the inflow of air into the air cannon; when the blasting is needed, press the start button to deliver a pulse signal or a gas signal to the quick discharge valve. After that, the air cannon release a strong blast through the air outlet completely, and then return to the state of air pressure automatically. This cycle will repeat again at any time on request. The manual operation is to perform the operation through the control button or by using the small handle on the change valve, and the automatic operation is to perform the action through an automatic control device. The control system can also involve a PLC to control the operation through the entire process. The operator is allowed to either control the sequence of the operation steps by pressing the buttons on the control panel, or control a single unit of air cannon in a separate way. This safe automatic system enables the unattended operation of the air cannons.
Automatic Control System of Air Cannon
Our company has the self-developed intelligent control box for air cannons, with the performance superior to general PLCs. The box allows for easy programming, which means that a worker with no professional skills can operate it. The box also offers good communication functions and sound I/O settings. In this way, it can meet various needs, like networking, parallel operation management, alarm signal releasing, etc.
Three Working Modes
Automatically program-control mode which can realize the control of time order and conditioned reflex. It can also realize the time setting operation of the turning on and off, which helps the operator control the time flexibly.
Microcomputer operation. The operator can control the equipment involved through BOP network with the mouse or keyboard
Hand operation which means the operator can operate through the control switch of the switch board
Our company has the self-developed intelligent control box for air cannons, with the performance superior to general PLCs. The box allows for easy programming, which means that a worker with no professional skills can operate it. The box also offers good communication functions and sound I/O settings. In this way, it can meet various needs, like networking, parallel operation management, alarm signal releasing, etc.
Three Working Modes
Automatically program-control mode which can realize the control of time order and conditioned reflex. It can also realize the time setting operation of the turning on and off, which helps the operator control the time flexibly.
Microcomputer operation. The operator can control the equipment involved through BOP network with the mouse or keyboard
Hand operation which means the operator can operate through the control switch of the switch board