Case introduction

The traditional process flow of bauxite calcination: raw materials entering the factory → warehouse → crushing → grinding → pressure filtration → mud preparation → extrusion molding → drying → calcination → crushing → finished products. Due to the instability of the raw material composition of bauxite, the bauxite clinker obtained by this traditional production process of calcining bauxite clinker is of low quality and unstable product quality. In order to obtain high-quality bauxite clinker, our company proposed a new process flow of bauxite calcination: raw materials entering the factory → warehouse → crushing → grinding → desiliconization → wet homogenization → pressure filtration → mud preparation → extrusion molding → drying → calcination → crushing → finished products. It has been strongly recognized by customers

Case advantages

1. Low energy consumption, which can reduce unit coal consumption by 40% compared with ordinary dome converters, with high product quality, good stability and strong market price advantage.

2. Simple and reliable operation, less staff and stable process.

3. Low environmental pollution, low maintenance and high operation rate.

4. Applicable to various fuels such as coal gas, coal powder and fuel oil.

5. Can be upgraded to automatic control, and the system is more stable.

Production Process

The commonly used bauxite calcining process is as follows: the bauxite with a particle size of 300-500mm is crushed and sent to the boiling furnace dryer for drying, and then passed through the batching station with manganese powder, admixtures, etc., and enters the grinding system with a * eddy current powder selector to prepare raw material powder with a fineness of more than 400 mesh. The new granulator developed by Zhengkuang Machinery is used to add water to make the raw material powder into pellets with qualified particle size. The pellets enter the dryer set at the end of the kiln, and the waste heat of the exhaust gas at the end of the kiln is used to reduce the moisture content of the pellets. Then, after screening, they enter the rotary kiln for calcination. The calcined ceramsite sand is cooled by a single cooler and screened through a cylindrical screen. Qualified pellets of different particle sizes are packaged separately and shipped out, and unqualified pellets are returned to the grinding system.

Specific steps of bauxite calcination process:

1. Crushing system

The bauxite entering the factory has a block size of about 300~500mm and a moisture content of about 8%. After entering the factory, the bauxite is piled in the shed. The storage capacity is generally about one month. The forklift shovels the bauxite into the silo, and the plate feeder feeds it evenly and continuously into the jaw crusher. After crushing, the particle size becomes 50~80mm, and then it is transported to the impact crusher by a belt conveyor, and the particle size is less than 20mm. The crushed bauxite is stored in the buffer silo.

2. Alumina drying system

The crushed alumina in the buffer silo passes through a belt conveyor and an elevator and enters the round silo on the top of the fluidized bed furnace. A weighing belt feeder is set under the silo to allow the crushed alumina to enter the dryer evenly. The dried alumina is sent to the dry alumina warehouse (batch warehouse) or to the pile shed. The storage time is generally about 5 days. The fluidized bed furnace produces hot flue gas at 800~900℃. Low volatile coal is used as fuel. The crushed coal particles are 5~8mm and are fed into the furnace of the fluidized bed furnace by a disc feeder. The automatic temperature control system is used to control the feeding speed of the disc feeder and stabilize the combustion temperature of the fluidized bed furnace. The bag dust collector is used to purify the exhaust gas from the dryer to achieve dust emission standards.

3. Batching station

Bauxite, manganese powder and admixtures are used for batching. All materials are transported to the batching warehouse. A speed-adjustable belt weighing feeder is set under the warehouse, and the microcomputer batching system realizes the automatic proportioning of materials. The proportioned materials enter the grinding system through the belt conveyor.

4. Grinding system

The grinding system adopts a closed-circuit system to produce raw material powder with a fineness of more than 500 mesh. The mill adopts a three-bin tube mill. The powder selector uses an O-sepa type* eddy current powder selector. By changing the speed of the powder selector, the fineness of the product can be easily adjusted. The selected finished raw material powder is collected by a high-concentration air box pulse bag dust collector and sent to the raw material round warehouse.

5. Granulation system

The granulation adopts a new type of granulator developed by our company. The granulator has the characteristics of fast balling speed, high efficiency, good roundness and clean production. After the raw material in the raw material round warehouse is discharged, it is transported to the silo on the top of the new pelletizer by a screw conveyor and an elevator. A screw weighing feeder is used under the silo to feed the raw material into the pelletizer. The water for pelletizing is metered and put into the pelletizer. The ratio of raw material and water can be adjusted. The raw material and water in the pelletizer are formed into raw material pellets under the action of the high-speed rotating stirring rod and the low-speed rotating inner cylinder in the machine. After a certain period of time, the pelletizing is completed, and the raw material pellets are discharged from the lower discharge pipe and fall onto the belt feeder. The raw material pellets are then transported to the kiln tail dryer.

6. Kiln tail dryer system

The water content of the newly made pellets is about 15%. Using the waste heat of the exhaust gas at the kiln tail, the moisture content of the pellets can be reduced to about 8% in the kiln tail dryer, and then they are calcined in the kiln. The kiln tail dryer adopts a countercurrent type. The hot air end of the dryer is equipped with a burner to provide hot air for the dryer when the heat of the kiln tail exhaust gas is insufficient. The temperature of the kiln tail exhaust gas used by the dryer is about 500℃. After being used by the dryer, the temperature drops to about 150℃, which is suitable for the working conditions of the bag dust collector at the kiln tail. The raw material particles leaving the dryer enter the intermediate warehouse for storage and are used by the rotary kiln.

7. Rotary kiln system

The dried raw material particles are discharged from the intermediate warehouse and lifted to the kiln tail by the elevator. The vibrating screen divides the raw material particles into qualified and unqualified. Qualified raw material particles enter the rotary kiln for calcination, and unqualified raw material particles return to the grinding system. In the rotary kiln, the raw material particles gradually move toward the kiln head as the rotary kiln rotates, and are calcined into petroleum proppant ceramsite sand at a temperature of 1300℃~1350℃ in the firing zone. The ceramsite sand enters the single-cylinder cooler for cooling, and the secondary air of the cooler enters the rotary kiln.

8. Kiln tail dust collection system

Bag dust collectors are used to purify the kiln tail exhaust gas (including the exhaust gas from the kiln tail dryer). A humidification tower is also set up at the rotary kiln tail to cool the kiln tail exhaust gas to reduce the exhaust gas temperature to the required temperature of the bag dust collector. The emission concentration of the bag dust collector can reach below 30mg/Nm3, achieving standard emission and clean production.

9. Finished product system

The ceramsite sand from the cooler is lifted to the vibrating screen and divided into different particle sizes according to standard requirements. It enters different finished product warehouses. Electronic weighing scales are set under the warehouse. The bagged finished products with qualified weight are sealed by the sewing machine and stacked in the finished product warehouse for shipment.

Feedback

The bauxite beneficiation production line designed for us by Global Heavy Industries is well-equipped and the equipment is reasonably purchased. After the production line is completed, it has a large processing capacity and no failures have occurred so far. It is really economically reasonable. It is a beneficiation production line with reasonable investment and high production efficiency, which is really worthy of praise.