1. Steelmaking practice has proven that active lime can improve desulfurization and dephosphorization efficiency by 80%, while shortening smelting time. It can completely react with acidic substances in the molten steel within 3-5 minutes, while the reaction time of vertical kiln lime is at least 6-10 minutes. In addition, increase the furnace ridge by more than 40%. The consumption of furnace materials has also been reduced by 5-8Kg/t of steel, with an annual savings of about 15 million based on 10 million tons, resulting in significant production benefits.
2. The efficiency of S and P removal by activated lime is significantly improved, with an average S removal rate of 34.5% in steelmaking, especially for high S molten iron (S ≥ 0.06%). The consumption of S removal agent can be reduced by about 45%.
3. The use of activated lime in steelmaking can reduce iron consumption by 5-15Kg/t compared to non activated lime steelmaking, and can also reduce steel splashing and oxygen sticking; Sticking furnace mouth; Sticky flue phenomenon.
4. Decrease in lime consumption per ton: The consumption of activated lime in steelmaking can be reduced by 20-25Kg/ton of steel compared to non activated lime, while the consumption of non activated lime per ton of steel is not less than 65-70Kg, and the consumption of activated lime is 40-41.5Kg/ton of steel.
5. Activated lime steelmaking has fast slagging, significant desulfurization and dephosphorization capabilities, and can increase production efficiency by 5% to 10%.

1. Raw material conveying system
Limestone and dolomite are crushed in the mine and transported to the factory area. They are then transported by shovel trucks to the raw material pit, screened and lifted to the raw material warehouse. After measurement, qualified limestone with a particle size of 10-50mm is sent to the top material bin of the preheater through lifting equipment. The particle size of the incoming material is 10-50mm, and the particle size of the finished product from the outgoing material is 5-40mm, reaching over 90%.
2. Active Lime Calcination System
The active lime calcination system consists of a vertical preheater, a rotary kiln, and a cooler.
(1) Vertical preheater: A vertical preheater is composed of a preheater body, a storage bin, a feeding pipe, a hydraulic push rod device, etc. Preheaters come in both polygonal and circular shapes, equipped with partition walls to gradually heat limestone and prevent rapid heating and explosion, resulting in a large amount of powder. The decomposition rate of limestone entering the kiln reaches 30% to 40%, and the average temperature of the discharged gas is 230 ℃ to 260 ℃, thereby reducing system heat consumption.
(2) Rotary kiln: The rotary kiln consists of a cylinder body, support device, variable speed transmission device, gear wheel device, kiln tail and kiln head seal, and kiln head cover. The kiln body is placed at a 3.5% inclination from the horizontal. Equipped with two sets of support devices, the roller bearings are water-cooled oil spoon lubricated sliding bearings, and have spherical tiles that can automatically adjust their center. There is also a hydraulic stop wheel located near the large gear ring. The kiln body is driven by a variable frequency speed regulating motor and equipped with auxiliary transmission to drive the kiln body. The kiln head and tail are equipped with spring type sealing devices. By using a variable frequency speed regulating motor to drive the kiln body and combining it with the preheater decomposition rate, the calcination time and temperature are effectively controlled to meet the requirements of raw and over fired indicators.
The burner adopts a coal gas mixed combustion four channel burner. Flexible and convenient adjustment, easy operation, the spraying speed of each air duct can be adjusted freely during operation, and any flame required under different kiln conditions can be adjusted. The kiln calcination temperature is easy to control.
(3) Vertical cooler: A vertical cooler consists of a cooler body, a fixed screen, a cooling air device, an electric vibration unloader, etc. The vertical cooler is divided into several cooling discharge areas, and the discharge speed of each area can be controlled separately according to the material temperature; The cooling air comes into direct contact with the hot lime inside the cooler, resulting in good cooling effect and low ash discharge temperature, which is about 40 ℃ higher than the ambient temperature; After cooling the lime, the temperature of the cooling air can be preheated to above 600 ℃. Part of it is used as secondary combustion air for the rotary kiln, and the other part is used for drying coal powder. The cooler has no moving parts, a simple structure, good cooling effect, and requires less equipment maintenance.
3. Coal powder preparation system
Coal powder preparation is an important component of using coal in the active lime rotary kiln system. There are generally two types of systems, one is the coal powder preparation system composed of an air swept tube coal mill and a bag filter, which has the advantages of easy operation and clean environment. The production process is as follows:
Coal blocks with a block size of ≤ 25mm are lifted and supplied to the belt by the process bucket, and then input into the raw coal bin through the belt. They are fed into the coal mill through the lower disc feeder or electromagnetic vibration feeder of the raw coal bin. The coal mill is a device that integrates grinding and drying. During grinding, hot air from the rotary kiln system or hot flue gas from the auxiliary combustion chamber is introduced for drying. The coal powder containing gas coming out of the coal mill, under the suction force of the exhaust fan, enters the powder separator for separation. The coarse coal powder is returned to the mill for further grinding through the automatic ash discharge valve, while the fine powder is driven by the airflow and enters the bag filter for dust collection, achieving the purpose of powder gas separation. The gas from the powder selection machine is purified by dust collection and discharged by the exhaust fan. Some of the waste gas is blown into the coal mill for recycling, while the other part is discharged into the atmosphere through the chimney. The coal powder collected by the dust collector is discharged into the coal powder storage bin in front of the kiln. According to the needs, the coal powder is sent from the coal powder silo to the front burner of the kiln through a Roots blower, and then supplied with air by the burner combustion fan for combustion, which is used for calcining limestone.
4. Finished product conveying system
Finished lime is transported from the cooler to the elevator through the chain bucket machine, and then sent to the top of the silo by the elevator. After screening, qualified products with a particle size of 5mm or more are sent to the finished product silo by the belt conveyor, while powder with a particle size smaller than 5mm is sent to the powder silo. Both the finished product silo and the powder silo are equipped with electric discharge valves. The main function of the finished product warehouse here is to serve as a buffer for measurement, and finished products should be promptly sent to the steel plant's calcium carbide plant for use to reduce pulverization.
5. Smoke treatment system
The high-temperature flue gas generated by the combustion of the rotary kiln is cooled by a multi tube cooler after heat exchange with limestone in the preheater, and then enters the high-temperature bag filter. After dust removal, it is discharged into the atmosphere through the chimney by a high-temperature fan. The dust concentration of the flue gas discharged into the atmosphere is less than 30mg/Nm ³.
To meet the process requirements of modern active lime pre decomposition rotary kiln production line, ensure reliable operation of process equipment, stabilize process parameters, ensure product quality, save energy, and improve the operation rate of the production line. The entire line adopts advanced technology for full process control, and adds DCS control on the basis of PLC control to centrally monitor, operate, and decentralize the main production line, control the rotary kiln operating system to improve product quality and reduce consumption. Improve the reliability and maintainability of electronic control equipment to achieve modernization of control, monitoring, and operation.
6. Product Quality
CaO ≥ 93, MgO ≤ 4.5, SiO2 ≤ 1.0 P ≤ 0.01 S ≤ 0.025, ignition loss ≤ 3, activity ≥ 350ml ～ 380ml, raw burning ≤ 1.5%, over burning ≤ 1.5%.

Qualified limestone is stored in the silo, lifted by the elevator, and transported into the top silo of the preheater. The top material bin of the preheater is controlled by two level gauges on top and bottom, and then the limestone is evenly distributed into each chamber of the preheater through the discharge pipe. Limestone is heated to around 900 ° C by 1150 ° C kiln flue gas in the preheater, with about 30% decomposed. It is pushed into the rotary kiln through a hydraulic push rod, and the limestone is sintered and decomposed into CaO and CO2 in the rotary kiln. The limestone generated after decomposition enters the cooler and is cooled to below 100 ° C by the cold air blown into the cooler before being discharged. 600 ° C hot air that has undergone heat exchange enters the kiln and mixes with coal gas for combustion. The exhaust gas is mixed with cold air and enters the bag filter through the induced draft fan, and then enters the chimney through the exhaust fan. The lime from the cooler is fed into the lime finished product warehouse through a vibrating feeder, chain bucket conveyor, bucket elevator, and belt conveyor. Whether to carry out screening and other processes according to customer requirements.

shaft preheater
The vertical preheater is one of the main engines of the active lime equipment. The main function of the vertical preheater is to send limestone materials into the preheater, and at the same time, use the high-temperature exhaust gas (1150 degrees Celsius) emitted after calcination in the kiln to uniformly preheat the materials to about 900 degrees Celsius in the preheater. During the preheating process, 30% CaCO3 is decomposed in the preheater, and then pushed into the rotary kiln for calcination by a hydraulic push rod. This calcination process not only greatly shortens the calcination time of limestone in the kiln, but also obtains lime with higher activity.
The vertical preheater system mainly consists of six parts.
1. Feeding system: mainly includes an upper material bin and a feeding pipe. The feeding method and structure can ensure safe sealing when feeding into the preheater body, so that external cold air cannot enter the preheater. The feeding can be achieved continuously or intermittently with the help of rod valves.
2. Preheater: It is an important part to ensure the preheating of materials to around 900 degrees Celsius. It consists of a preheating chamber, a suspension device, and refractory brick lining (which is not within the scope of equipment design and manufacturing). The structure of this part is mostly made of metal components, and some materials are selected from heat-resistant steel as needed. Heat resistant steel can work at high temperatures of 1000-1100 degrees Celsius. In addition, the refractory brick lining structure has a novel design and good sealing performance, which can ensure that the material is uniformly preheated in the preheater and reaches the preheating temperature.
3. Pushing device: mainly includes pushing head, frame, connecting rod and other parts. The pushing head is made of heat-resistant steel casting or welding, which can withstand high temperatures. With the help of electronic control and hydraulic system, each hydraulic push rod can push materials sequentially according to the automatic control program.
4. Hydraulic system: mainly includes oil tank, oil pump, motor, solenoid valve, hydraulic oil pipe, etc. Its main function is to control the pushing device and complete the pushing action. 5. Feeding chamber: mainly includes a chute, feeding chamber body, feeding nozzle, etc. Its main function is to introduce preheated materials into the rotary kiln for calcination.
6. Framework: It mainly includes columns, ring beams, etc., and its main function is to support the upper structure of the preheater.