annular shaft kilns for sale

Annular Shaft Kiln

Production Capacity: 200 – 600 t/d

Heat Consumption: 930-980 kCL/kg

Lime Activity: >350mL

Application: Active lime production, quick lime production.

AGICO Annular Shaft Lime Kiln

The annular shaft kiln is one of the mainstream high-end kiln types in the lime industry, adopting a circular structure with the inner shaft nested inside the kiln shell. Compared to traditional vertical lime kilns, the calcination process inside the annular shaft kiln simultaneously employs the principles of concurrent and countercurrent airflow, effectively solving the problems of under-burning and over-burning of lime, thus enhancing lime activity. Additionally, the annular shaft kiln also has advantages such as environmental friendliness, good energy efficiency, small footprint, high automation level, and superior quality of lime produced after calcination. As a result, it is widely used in lime production within industries such as steel, calcium carbide, alumina oxide, and building materials.

The manufacturing process of AGICO CEMENT’s annular shaft kiln originates from Germany and has been continuously optimized and improved through over twenty years of production practice. Currently, the company is capable of designing and constructing annular lime kilns with a maximum daily output of 600 tons. These kilns exhibit low energy consumption, with typical heat consumption ranging from 930 to 980 kcal/kg of lime and electrical consumption from 22 to 25 kW·h/t of lime, significantly reducing production costs. Moreover, the annular shaft kilns manufactured by our company support the use of various fuels such as natural gas, coke oven gas, converter gas, high coke mixed gas, heavy oil, coal powder, etc., allowing customers to choose the most suitable fuel scheme based on local energy prices and maximize production cost savings.

annular shaft lime kiln details

AGICO Annular Shaft Kiln Features

Scientific & advanced calcination process

The annular shaft kiln forms a circulating gas inside the kiln during lime calcination. The generation of circulating gas forms a concurrent calcination zone inside the kiln, allowing the annular shaft kiln to produce lime with high activity. By controlling the flow rate and temperature of the circulating gas inside the kiln, it is possible to control the calcination process and fully utilize heat, thereby reducing the under-burning and over-burning rate of lime and ensuring lime quality.

Environmentally friendly production process

During the lime calcination process in the annular shaft kiln, the kiln chamber is always under negative pressure, which makes it difficult for fly ash and exhaust gases generated during the calcination process to leak out, effectively reducing pollution to the surrounding environment caused by lime production. This improvement enhances the working environment for operating personnel and facilitates maintenance and inspection of the entire lime kiln system.

Flexible capacity & fuel adaptability

The daily output of the annular shaft kiln can be adjusted between 100 tons and 600 tons, with actual production reaching 60% to 110% of the nominal output. The annular shaft kiln can be designed to adapt to all types of gaseous, liquid, and powdered solid fuels. It can also be designed to use several different fuels in a single kiln (such as natural gas and heavy oil), allowing for simple operation to switch from one fuel to another.

Intelligent & worry-free automation control

AGICO’s annular lime kiln is equipped with an advanced PLC system for operation control, enabling intelligent and automated lime production. Monitoring units distributed throughout the annular shaft kiln can monitor the feeding and discharging of materials, calcination temperature, gas flow rate, and other operating conditions in real time. Based on monitoring data, the system can automatically adjust parameters and issue alarms. The system is easy to operate and significantly reduces the number of production personnel required.

Annular Shaft Kiln Working Principle

The annular shaft kiln consists of a kiln shell lined with refractory materials and an inner shaft divided into upper and lower sections. The kiln shell and the inner shaft are arranged concentrically, with the material located in the annular space between the kiln shell and the inner shaft to facilitate airflow penetration. The lower inner shaft is located at the bottom of the kiln and is structured as a double-layer steel shell forming an annular gap, which is air-cooled inside the gap with refractory lining on both the inner and outer sides. The upper inner shaft is suspended at the top of the kiln. The upper and lower inner shafts have different functions: the upper inner shaft mainly extracts high-temperature exhaust gas for preheating injection air, while the lower inner shaft is mainly used to generate circulating airflow, forming concurrent combustion, and ensuring uniform distribution of airflow.

The annular shaft kiln can be divided from top to bottom into preheating zone, upper counter-current combustion zone, middle counter-current combustion zone, lower concurrent combustion zone, and cooling zone. The core part is the lower concurrent combustion zone, where lime is finally burned. The limestone entering the kiln is preheated by convection in the preheating zone and then enters the upper combustion zone. In the upper combustion chamber, incompletely burned hot gases are fully burned, and the limestone undergoes decomposition. In the middle combustion zone, the material meets the hot gases flowing from the lower combustion chamber and undergoes counter-current combustion, and continues to decompose. In the lower combustion zone, the material undergoes concurrent combustion with the hot gases flowing from the lower combustion chamber and is completely decomposed into lime, which then enters the cooling zone and is cooled to obtain the final lime product.

annular shaft kiln design drawing
AGICO Annular Shaft Kiln Design

AGICO Annular Shaft Kiln Specifications

Daily output100t/d400t/d600t/d
Effective inner diameter6.1m×4.1m6.9m×4.1m10m×6.5m
Effective height23~23m23~24m23~25m
Effective volume350m1550m2950m3
Smoke emission concentrationdust≤10mg/m3dust≤10mg/m3dust≤10mg/m3
SO2 ≤50mg/m3SO2 ≤50mg/m3SO2 ≤50mg/m3
NOX≤150mg/m3NOX≤150mg/m3NOX≤150mg/m3
Heat consumption(kcal/kg)820-860820-860820-860
Operation rate>95%
Raw material particle size30mm~60mm(40mm~80mm)
Product granularity0mm~70mm
Residual CO2~2%~2%~2%
Lime activity≥360ml
CaO content≥90%
Power consumption~ 30Kw.h/t

Annular Shaft Kiln Structure

annular shaft kiln systems
annular shaft kiln designed structure
air flow int the annular shaft kiln

Kiln Body:

The kiln body consists of an outer shaft (kiln shell) and concentric upper and lower inner shafts. The outer shaft is formed by rolling steel plates and lined with refractory materials. The inner shaft is divided into upper and lower sections. Both the upper and lower inner shafts are cylindrical boxes made of double-layer steel plates. Continuous cooling air is introduced into the steel plate box to prevent deformation at high temperatures. Refractory bricks are laid on both the inner and outer sides of the box. The inner shafts are arranged concentrically with the outer shaft, forming an annular space where limestone is calcined to produce active lime.

Fan System:

The annular shaft kiln’s fan system consists of inner sleeve cooling fans, driving air fans, and high-temperature exhaust fans. The inner sleeve cooling fans supply cooling air to the inner sleeve. The cooling air is preheated after passing through the inner sleeve and serves as primary air for the burner. The driving air fans supply injection air to the burners through injectors, creating a circulating gas inside the kiln. The high-temperature exhaust fans are used to extract the waste gas from the kiln, exchange heat with the driving air, and maintain a negative pressure environment inside the kiln.

Combustion Chamber:

The annular shaft kiln relies on two rows of burners, one above and one below, to calcine the limestone (calcination temperatures are 1200~1300°C for the upper combustion chamber and 1300~1350°C for the lower combustion chamber). The combustion chambers are located in the middle of the kiln body and are divided into upper and lower layers. The number of combustion chambers per layer varies from 3 to 6 depending on the kiln’s production capacity. The combustion chambers are connected to the inner shaft through arches built with refractory materials. The high-temperature flue gas generated by combustion enters the layer of limestone through the space under the arches. The upper and lower layers of combustion chambers are distributed staggered and evenly along the same row.

Feeding and Discharging System:

The feeding device of the annular shaft kiln consists of a weighing hopper, gate, single-bucket elevator, sealed gate valve, rotary feeder, material bell, and material level detection device. After preheating, calcination, and cooling, the limestone is discharged directly from the bottom of the cooling zone into the lower ash bin by a drawer-type discharger, and then discharged through a vibrating feeder under the bin.

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