What is Vertical Lime Kiln?
Lime vertical kiln, also known as lime shaft furnace, lime rotary kiln, mainly includes the furnace wall and the burner set on the furnace wall. A cylindrical furnace core is implanted in the center of the shaft furnace, and there is an annular gap between the furnace core and the furnace wall.
Mechanized vertical lime kilns are the main calcining equipment in the production of cement and alumina production. The kiln has reasonable design, advanced technology, large transmission device carrying capacity, long service life and stable output, and can produce high-quality lime.
Overview Of Lime Shaft Kiln Process
The loader loads the qualified raw fuel into the limestone silo and the coal silo, and then transports them to the mixing silo through the conveyor belt. The raw fuel is accurately weighed by the electronic weighing system according to the set value, and the material is evenly fed by the vibrating feeding machine or called distributor and then mixed evenly. Then the mixed material is transported to the vertical lime kiln’s top receiving hopper by the lifting truck, and the kiln distribution is completed through the kiln top volute type distributor. The mixture of coal and limestone moves down slowly by its own weight, and successively passes through the preheating zone, the calcining zone and the cooling zone.
During the descending process of the coal and limestone, a complex heat exchange is carried out with the hot rising gas flow, which is accompanied by the decomposition of limestone and the development and growth of quicklime grains. When the whole process is completed, it is also cooled down to 40-60 ℃ by the combustion air, and then unloaded by the unloader to the finished product belt outside the furnace without air leakage. The lime is transported to the finished product silo by the multi-bucket elevator. If sieving is required, it should be sieved first and then loaded into the block ash bin and the powder ash bin.
Process characteristics
Uniform feeding, rotating cloth
The top feeding system consists of receiving hopper, transmission and rotating distributor. The material is evenly and quantitatively fed from the material truck to the rotating distributor, which promotes the material to be further mixed before entering the furnace. The rotary distributor is a circular fixed-point distribution, which can be automatically or manually distributed. The limestone and coal are distributed in the shape of “Dots and nets” on the section of the furnace, and the material surface is in the shape of “M”, therefore, the air flow in the furnace is evenly distributed, which plays a key role in the stability of the calcining belt.
Reasonable air supply, sealing & ash output
This part is composed of centrifugal fan, air cap and ash unloader. Fans supply air quantitatively as required. The air cap is designed by us. The air cap ensures the uniform air supply in the furnace and effectively suppresses the partial burning and overburning of the shaft furnace. The ash unloader can make the material discharge evenly around the circumference, ensure the uniform and steady descent of the material column and the timely removal of the abnormal material column, which not only ensures the stability of the airflow in the furnace and prevents the furnace gas from leaking out, but also improves the on-site environment.
Automatic weighing and uniform batching
Accurate weighing and reasonable ratio of incoming limestone and coal is one of the key links for high-quality calcination and energy saving and consumption reduction in lime shaft kilns.
Automatic control, safe and reliable
The lime furnace system adopts automatic control technology. It is used on key equipment such as material distribution, mixing, air supply and ash discharge to ensure the safe operation of each key equipment.
Cross-section of normal vertical shaft kiln
a. the preheating zone b. calcining zone c. the cooling zone
Vertical Lime Kiln Specification
| Vertical Kiln(Effective vol)(m³) | 100-500 |
| output(t/d) | 80-400 |
| Energy consumption(KJ/kg·lime) | 910×4.1868 |
| Coal consumption(kg/t·lime) | ＜130 |
| Utilization factor(t/d.m3) | ≥0.85 |
| Activity degree(ml) | ≥300 |
| Calcium content of quicklime (%) | ≥90 |
| Over-burning rate of quicklime (%) | ＜ 5-7 |
| Quick lime consumption(t/t) | 1.8 |
| CO2 concentration in flue gas (%) | 42 |
| Soot emission index(mg/Nm3) | ＜ 10 |
