Lime production process
1. Raw material conveyor system
Limestone (dolomite) will be conveyed after screening. Qualified lime stone particle size 10 ~ 50mm will be conveying to top silo of preheater by lifting equipment. discharging finished size of 5 ~ 40mm above 90%.
2. Lime calcining system
Lime calcining system consists of a vertical preheater, rotary kiln, cooler.
Vertical preheater: Vertical preheater is consisting of a preheater body, a feeding pipe, a storage bin, hydraulic push rod device etc.
Preheater has polygonal and round using compartment partition device .Making the limestone gradually heating to avoid sharp warming burst into the kiln produces a large amount of powder, limestone decomposition rate is 30% ~ 40%, the average temperature of exhaust gas temperature is 230~260℃, thereby reducing the heat consumption.
Rotary kiln: rotary kiln is composed of cylinder, supporting device, drive device, block wheel device, kiln tail and kiln head seal, burning device, kiln head cover etc.
The kiln body is a cylindrical vessel, equipped with supporting device; the roller bearing is the water-cooled oil lubricated bearings. Near the gears ring are also equipped with hydraulic blocking wheel, using frequency conversion motor driving kiln body, and an auxiliary driving kiln. Kiln head and kiln tail adopts sealing device, using frequency conversion motor driving kiln and with preheater decomposition rate, to control effectively calcination temperature and time, reached our burning requirements.
Lime is fed into the upper end of the cylinder. As the kiln rotates, material gradually moves down towards the lower end.
Vertical Cooler: vertical cooler is composed of cooler body, fixed screen, cooling device, electric vibrating discharging machine etc.
Vertical cooler has many cooling discharge area, each area discharging speed can be controlled separately according to material temperature; Cooling air meet hot lime directly, cooling has well effect, ash temperature is low, ash temperature higher than the ambient temperature 40 ℃; cooling air after cooling lime, temperature can be preheated to more than 600℃, one part is used as second combustion air in rotary kiln, the other part is used to dry pulverized coal. Cooler is without moving parts, good cooling effect, simple structure, less equipment repair.
3. Pulverized coal preparation system
Pulverized coal preparation system is an important part of lime rotary kiln system. There are generally two kinds of system; firstly, it is the wind swept coal mill tube mill pulverized coal preparation system with bag dust collector. It is convenient operation and clean environment etc. Its production process as follows: Block degree ≤ 25mm coal, from bucket elevator into the belt, then conveyed to coal bunker by belt, through disc feeder or electromagnetic vibration feeder that under coal bunker, the mill is a set of grinding, drying, when grinding, introducing hot air from rotary kiln system or flue gas from auxiliary combustion chamber to dry.
Gas out from separator, the dust discharged after purification by an exhaust fan, a part of exhaust gas recycled in coal grinding mill, another part exhaust gas into the atmosphere through the chimney. Pulverized coal collected by the dust collector is discharged into the kiln coal storage bin. According to the need of coal warehouse, into the kiln front burner with a Roots blower, through the burner combustion air blower air supply for combustion, used for calcining limestone.
4. Finished product conveying system
The final lime is conveyed to bucket elevator through bucket machine by cooler, then into top sieving grain silo by elevator, qualified part ≧5mm conveying to finished product bin by belt conveyer, powder≦5mm conveying to powder bin.
5. Flue gas treatment system
High temperature flue gas from rotary kiln combustion, after the heat exchange with the limestone in preheater, the temperature dropped to 280 ℃ below, these gases will be cooled down by multi-tube cooler to 200°C lower. Cooling through multi tube cooler and then into the high-temperature bag type dust collector. After dust collector, high temperature fan into the atmosphere through the chimney, the dust concentration is less than 30mg/Nm ³. 
The calcination process adopts preheater+ rotary kiln+ vertical cooler system; it can reduce the fuel consumption 40%, and increase output capacity 30% due to reuse the waste gas in the system. Others advantage are in the following.
1. Good quality and high activity.
2. It is suitable for large-scale lime production line.
3. Running stable, the whole process using negative pressure, air flow freely and high production safety
4. Using the bag filter system, it can reduce the exhaust gas
5. It shortens kiln length, so it can reduce heat loss and area.
6. Cooler and kiln hood cover designed together, good seal, saving area.
Main Equipment:
| No. |
Equipment name |
Specification |
Type |
|
|
1
|
rotary kiln
|
Ф4.0×60m
|
|
1
|
|
2
|
vertical preheater
|
Ф10.5×8.5m
|
|
1
|
|
3
|
vertical cooler
|
105m3
|
4.2*9m
|
1
|
|
4
|
multi pipe cooling machine
|
dealing air：260000m3/h
|
|
1
|
|
5
|
High temperature exhaust fan
|
900kw，10KV
|
|
1
|
|
6
|
coal mill system
|
8-10t/h
|
PDM1250
|
1
|
|
7
|
Gas/coal burning system
|
|
four way burner
|
1
|
|
8
|
dust collector equipment
|
|
8.1
|
kiln tail flue dust collector
|
dealing air ：260000m3/h
|
LCMD-3660
|
1
|
|
8.2
|
coal grinding dust collector
|
dealing air：45000m3/h
|
FGM128-6(M)
|
1
|
|
8.3
|
cooling dust collector
|
dealing air：18600m3/h
|
PPc64-4
|
1
|
|
8.4
|
finished product screening dust collector
|
dealing air：18600m3/h
|
PPc64-4
|
1
|
|
9
|
accessory equipment
|
|
9.1
|
bucket elevator
|
|
NE100
|
1
|
|
9.2
|
Circular vibrating screen
|
|
YA1536
|
1
|
|
9.2
|
Circular vibrating screen
|
|
YA1236
|
1
|
|
9.4
|
chain scraper conveyor
|
|
DS500
|
1
|
|
9.5
|
belt conveyor
|
|
|
6
|
|
10
|
fan
|
|
10.1
|
axial flow fan
|
|
|
4
|
|
10.2
|
centrifugal fan
|
|
|
2
|
|
10.3
|
coal mill fan
|
|
|
1
|
|
10.4
|
roots fan
|
|
|
3
|
|
