Ceramic sand, also known as oil fracturing proppant, is a new type of material made of bauxite, manganese powder and additives, which is crushed, dried, batched, pelletized, calcined, cooled and screened. Ceramic sand has the advantages of high strength, pressure resistance, wear resistance, high roundness, good shock resistance and permeability resistance.
Production process of ceramsite sand rotary kiln:
1. Crushing:
The mined bauxite is generally about 300~500mm in size and contains a small amount of water. Generally, a secondary crushing system consisting of a jaw crusher and a hammer crusher is used to control its particle size to ≤8mm.
After entering the factory, the bauxite can be stacked separately according to different grades. Use it according to the indicators. In the process of producing ceramsite sand, manganese (Mn) is usually added to reduce the sintering temperature and dye the product dark. Most domestic manufacturers use low-grade (content ~50%) manganese ore or manganese ash as the source of manganese.
2. Batching:
Several materials such as bauxite, manganese powder, and recycled materials are transported to their respective material warehouses, and a speed-adjustable belt scale is set under the warehouse to realize automatic batching and metering of materials.
3. Grinding:
Generally, a ball mill that is used for drying and grinding is used, and a powder selector is used to form a closed-circuit system. This has high grinding efficiency. The hot air for drying materials can come from the exhaust gas of the rotary kiln to achieve waste heat utilization; a special hot air furnace can also be set up.
4. Ball making:
The raw material powder discharged from the mill is stored in the raw material warehouse. Generally, 2 to 3 warehouses are set up, and materials can be discharged separately or in combination with multiple warehouses.
The raw material powder is sent to a small silo, and a spiral metering device or a speed-adjustable belt scale device is set under the silo to measure the amount of raw material. The raw material enters the disc ball making machine. At the same time, a flow meter can be used to measure the amount of water, and the water is sprayed into the disc ball making machine by a pipeline pump. During the rotation of the ball making machine, balls of various particle sizes can be made.
After the balls are discharged from the disc, they are sent to the screening device by the belt conveyor. The qualified ones enter the rotary kiln, and the oversized ones return to the raw material grinding process. Different numbers of disc ball making machines can be equipped according to the output of different kilns.
The ball making system has a high degree of automation and a continuous process. After matching with a bag dust collector, it can achieve the dust standard at the post and purify the post working environment.
5. Calcination:
The balls enter the rotary kiln with a certain slope for calcination. As the rotary kiln rotates, the balls roll toward the kiln head, and the coal powder is sprayed into the kiln from the kiln head for combustion. The balls are calcined into high-strength ceramsite sand in the rotary kiln.
The kiln body of the rotary kiln is inclined at 3%-4% (sine) with the horizontal plane. The entire kiln body is supported on the corresponding supporting wheel device through two wheel belts. The wheel blocking device at the kiln tail prevents it from moving up and down in the axial direction of the kiln body. The transmission process is that the variable frequency motor drives the small gear to rotate through the reducer and its matching coupling, and the small gear meshes with the large gear ring fixed in the middle of the cylinder, and finally the large gear ring drives the cylinder to rotate. The fuel is sprayed into the kiln by the gas or coal powder at the kiln head through the burner for combustion. The heat is transmitted to the material by the radiation of the flame, the convection of the hot air, the conduction of the kiln bricks, etc., and it becomes a finished product after calcination. The calcination process is that the material is input from the high end (kiln tail part) of the kiln cylinder. Due to the inclination and slow rotation of the cylinder, the material will produce a comprehensive movement of rolling along the circumferential direction and moving along the axial direction, and is continuously transported to the lower end (kiln head part) of the kiln cylinder. The material is sent into the kiln from the kiln head for combustion. During the flow process, the material meets the high-temperature airflow and is continuously heated to complete the physical and chemical reaction. The burnt clinker is discharged from the kiln head and enters the next process.
The pulverized coal burner can adopt a single-channel coal injection pipe, which is simple and reliable with high primary air volume; it can also adopt a multi-channel burner, the primary air volume can be reduced to 8% of the air volume required for pulverized coal combustion, increasing the secondary air volume entering the kiln, and the energy saving effect is significant. The multi-channel burner is divided into external axial flow air, coal air, internal axial flow air, etc., and the flame shape is very easy to adjust.
The metering of pulverized coal can be carried out by a rotor metering scale or a Coriolis force scale to accurately control the amount of coal and stabilize the thermal system in the kiln.
6. Preparation of pulverized coal:
The preparation of pulverized coal can be carried out by ball milling or vertical milling, and hot air can be extracted from the kiln head hood to dry the pulverized coal. The use of a dynamic powder selector can adjust the fineness of pulverized coal at will, providing conditions for the full combustion of pulverized coal.
7. Finished product cooling:
The cooling of ceramsite sand generally adopts a rotary cooler, which is simple and reliable. The secondary air of the cooler is completely fed into the kiln. With the use of multi-channel burners, a lot of energy consumption can be saved. The temperature of the ceramsite sand out of the cooler is very low and can be picked up by hand.
8. Screening:
The ceramsite sand out of the cooler can be directly transported to the multi-stage vibrating screen and divided into multiple particle size grades as required.
Rotary kiln fuel:
The fuel for calcining in the rotary kiln can be gas, heavy oil or solid fuel.
The outstanding advantages of the rotary kiln production process of ceramsite sand
1. The combustion equipment uses energy-saving burners to automatically control the air volume and reduce the loss of incomplete combustion of fuel.
2. The refractory bricks of the rotary kiln use composite bricks with lightweight insulation on the outer layer and fire-resistant and wear-resistant inner layer to reduce the heat dissipation of the outer skin of the rotary kiln.
3. A vertical preheater is installed at the tail of the rotary kiln, which makes full use of the high-temperature flue gas generated by the combustion of the rotary kiln to preheat the materials in the preheater, so that the materials are partially decomposed in the preheater, and the system output is increased.
4. A vertical cooler is installed at the head of the rotary kiln, which makes full use of the heat contained in the high-temperature calcined white material of the rotary kiln to preheat the secondary air to 600℃, so that the thermal efficiency is improved. Kiln head adopts
5. The vertical cooler and the kiln head cover are designed and constructed in an integrated manner, which has a small footprint and good sealing, and effectively avoids the unorganized emission of hot exhaust gas.
6. The environmental protection dust collection at the kiln tail is good, and the cyclone dust collector and pulse bag dust collector are used for secondary dust removal, and the emission concentration is lower than the national standard.
7. The automation level is high, and the adjustment, control and alarm of the production system operation are centrally controlled by PLC in the main control room, with fewer on-site operators and high labor efficiency.
