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coal silo

• Solid structure & strong resistance to corrosion
• Short construction term
• Lime silo's service life can reach 30 years
• Diameter: 3-28m
• Maximum height: 28m

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The technology of silo storage for coal is often used in power plants and coal mines. Concrete silos and steel silos are both usually used as coal storage silos. A concrete silo requires a long construction period and high investment, but a steel silo can be quickly built with less budgets.

As the latest type of steel silo, Lipp steel silo has been widely used in coal storage, grain and oil storage, brewing, building materials, environmental protection, chemical industry, energy and other industries.

Lipp Silo is invented by a German engineer named Xaver Lipp. This silo technology was introduced to China in 1960s, and starts its application in the field of coal storage in 1980s. Now it has been widely used in coal mines, cement plant, grinding station, hydropower station, thermal power station, and cement transfer depot.

Lipp Silo Technical Performance & Features

Technical performance

• Good integrity and long service life. Special equipment was used in the whole process of Lipp silo construction, this greatly strengthened the carrying capacity of the silo body, and granted the silo high integral strength, good stability and excellent seismic performance.
• High sealing effect, prevent rain and leakage. Due to the five layer undercut technology, Lipp Silo has an outstanding sealing effect. It can prevent cement, fly ash and other materials from caking and hardening.
• Short construction period, low cost. By using field construction, Lipp equipment can provide a shaping speed of 3-5m per minute, which shortens the construction period.  A 15m tall coal silo could be constructed in 8-10 days. Cost-effective can be achieved for light sheets are used for the whole silo, which also makes the lipp silos  much lighter than concrete silos.
• Covers small area, easy to manage. Lipp Silo’s height and diameter can be arbitrarily adjusted within a large range. Comparably small coverage that could narrow the separation distance between two silos down to 500mm for maximized space utilization.

Technical characteristics

The construction technology of Lipp Silo is the world's most advanced steel silo construction technology. It’s construction method is unique: during the construction, put the 495mm width coil from the decoiling machine into forming machine rolled into the desired geometry then through the bending machine. During the rolling process, the silo wall undercut a 30mm-40mm spiral convex strip, which is 5 times thicker than the material. Stiffeners were installed inside the silo to structurally enhance its stability and durability.

Explore the use of Lipp Silo coal storage process

Production flow (take coal silo for example)

A complete set of coal silo system includes feeder system, dedusting system, gas path arch breaking device, silo body, electrical control system, under carriage, guardrail and other components.

On the top of coal silo, there is an electric dedusting device, which can reduce the coal dust released to the surrounding environment. When dust accumulate to a certain degree on the top of dust catcher, it’s easy to start the vibration motor to shake them off through electrical control.

There is also a level e sensor on the top of the silo, or a radio-frequency capacitive material level limit switch both on the top and bottom of the coal silo.

When the switch is on, we can be aware of the body height of materials inside the silo through the electrical signals and then analyze the inventory of coal or other powders.

The silo is equipped with an air blowing arch breaker on the cones of its bottom. By using a small electromagnetic directional valve in the pneumatic box, it’s able to control the release compressed air, which helps to broke coal powder arch and avoid accumulated plugging.

The air supply can be provided through gas circuit by supporting stirring device, and the air blowing arch breaker can be controlled by electrical system according to the supply time of coal powders. Namely, when the material supply time is beyond the set time, the automatic blowing broken arch can also be controlled manually.

Conveying powder material from feeding tube to coal (fly ash) silo, bulk coal or fly ash can be directly sent to the silo by bulk material vehicles.

Coal silo is provided with a coal silo grounding protection device.

Rhe silo layout can be set according to the requirements of the factory. The selection of steel silo should be according to the actual needs and circumstances.

Discharge mode of silo

Due to the poor mobility of coal, the discharge mode of the silo usually use inverted cone. Cone wall angle should be greater than 45 degrees for easy discharge. Discharge port can be used with double feed port, multiple feed port etc. In order to prevent eccentric unloading, and to ensure that the main structure of the silo is balanced and the discharge port is symmetrically arranged.

Problem of coal arch blocking

Application of large capacity Philips silo in the coal storage and transportation, are more prone to arch blocking phenomenon. There has many existing coal bunker arch breaking method. Commonly used Artificial broken arch method, Hydraulic broken arch method, Wind broken arch method, Vibrator broken arch method, Air guns, etc. Should according to the specific circumstances of Lipp Silo choose one or more methods.

Problem of dust explosion in silo

Coal stored in steel silos for a long time is prone to spontaneous combustion. In the process of spontaneous combustion, it not only releases heat, but also combustible gas in different content. When the temperature, the concentration of combustible gas, and dust concentration reach ro a certain value, the steel silo will explode. So it is necessary for us to take measures to prevent such accidents.

1. Enter the inert gas in the steel silo to reduce mixture of dust and combustible gas. Destroy the combustion condition of coal dust and flammable gas to avoid explosion.
2. Establish a ventilation system and use an insulation system to extend the coal storage cycle.
3. Establish GD2000 combustible gas detector, and use it with the combustible gas alarm controller to form a silo safety inspection system to detect abnormal conditions in time and accurately. When there is combustible gas in the silo, the detector can immediately send out the electrical signal which is proportional to the content of the combustible gas in the air. Signal transmitted to the alarm controller can display (or record) the concentration of combustible gas in the air, at the same time sent out sound, light alarm and control signal, so as to ensure the safety of production, to avoid the occurrence of malignant events.

This automation industrial production can effectively reduce the labor cost and improve the production efficiency.

Lipp silo uses galvanized plate

Choose galvanized plate can effectively prevent the coal silo wall corrosion. For other parts of the inner wall of the silo, such as stiffener need to brush paint for anti-corrosion and regular inspection.

Problem of coal spontaneous combustion

Due to the special nature of coal, it is very prone to spontaneous combustion, the following measures can be used to prevent.

1. Adding insulation layer outside the silo wall. In northern China, the winter is very cold, the insulation layer out of the silo wall can prevent the coal from freezing and agglomeration. Also can prevent steel silo in the southern region because of the high temperature out side the silo caused coal in the silo heating up too fast caused spontaneous combustion of coal. Heat insulating material usually use rock wool attached with color steel plate outside.
2. Steel silo has complete ventilation system. To prevent coal spontaneous combustion, must reduce the temperature inside the silo, so the construction of ventilation system is the necessary condition of the silo. At the bottom of the steel silo set the ventilator, through the Ventilating duct leading-in the outside dry cold air to the ventilation geosyncline vent pipe, using the diffusion of gas continuous heat exchange with coal in silo, timely discharge the hot gas in silo to achieve the purpose of reducing the temperature. The roof of Lipp Silo all installation explosion proof vent, AQZZ series steel silo pressure release device, can achieve some ventilation explosion-proof effect.
3. Using temperature measuring cable to detect the temperature of coal in silo. When the temperature reaches the set value, the alarm signal is sent out.
4. Enter the inert gas in the silo to prevent coal spontaneous combustion or dust explosion.

Through the above method, can effectively control the problems that may occur when carrying coal in Lipp Silo, and improve the utilization rate, make it possible to store coal in Lipp silo.

Economic and technical comparison between Lipp Silo and Concrete Silo

Technical performance comparison with Concrete Silo

Technical performance comparison between Lipp Silo and Concrete Silo are shown in table 1.

Technical performance comparison with Concrete Silo
No.	Item	Lipp Silo	Concrete Silo
1	Sealing Property	Good air tightness, can store liquid	Good air tightness
2	Service Life	More than 20Years	More than 50 Years
3	Construction Method	Imported equipment, mechanical operation	Sliding mode construction
4	Maintenance Work	Regular maintenance, small amount of maintenance	No need to maintain
5	Appearance	Aesthetic	Commonly
6	Meteorological requirement	Construction is not affected by the weather	Construction affected by the weather
7	Environmental requirements for construction	Less	More

Economic comparison with Concrete Silo

Mengyuan coal Co.,ltd, used Lipp Silo in their lignite project. The economic comparison with the same type of concrete silo are shown in table 2.

Economic comparison with Concrete Silo
No.	structural style	Lipp Silo and Concrete	Complete Concrete Silo
1	Quantity of coal silo	1	1
2	Coal silo specification/m	Φ15×H18	Φ15×H18
3	Silo volume/m³	3179	3179
4	Silo wall thickness/mm	4.0	4.0
5	Heat preservation	Rock wool, Choi metal	-
6	Cost/RMB	1,400,000	1,850,000

Conclusion:Lipp Silo compared with Concrete Silo, the former is more economical and practical, it also has the characteristics of beautiful appearance, excellent construction, short construction period and so on. Especially introduce the important problem that coal storage in Lipp Silo should avoid and notice. We are sure that Lipp silo will be widely used in the coal industry with it’s unique advantages, and play a greater role in the energy sector.