Lime rotary kiln production line

Lime rotary kiln：

The main equipment for calcining lime in a rotary kiln is a preheater, rotary kiln, and cooler. Auxiliary equipment includes limestone storage equipment, supply equipment, exhaust gas treatment and dust removal equipment, product processing and storage equipment, and combustion equipment.
Limestone is crushed by a crusher to a size of 10mm-50mm, and then enters the preheater through the supply equipment to form a material layer that flows downward. It is then discharged by a variable speed blade rotary discharge device through a chute and supplied to the rotary kiln.
The high-temperature gas (1000-1100 ℃) coming out of the kiln is separated from the dust by the dust collection cyclone, and then rises through the pipeline into the preheater. During the filling layer, the heat is transferred to the limestone and then leaves the preheater. The gas outlet temperature is 250 ℃ -350 ℃, and limestone is heated to about 700 ℃. The decomposition degree is generally considered to be around 20%. The rotary kiln firing area is usually set within 30-40 minutes after the material enters the kiln.
The limestone preheated in the preheater is sent into the rotary kiln, and by relying on the slope and gentle rotation of the kiln, the limestone moves towards the outlet while being calcined by the hot gas from the burner. It is slightly cooled in front of the outlet and discharged into the cooling machine at the hood of the kiln through the outlet.
The fuel (coal powder, natural gas, heavy oil, etc.) entering from the burner is immediately gasified and burned to generate high-temperature gas, which is mainly decomposed and decarbonized by radiant heat and heating of the raw materials.

The products discharged from the kiln flow downwards through the maintenance room and the heat exchange part of the filling layer, and are discharged outside the kiln by the ash discharge machine located at the lower part. When the product passes through the heat exchange part of the filling layer, it undergoes counter current heat exchange with the cooling air that rises in the cooler and is cooled to below 100 ℃ by the cooling air fan. In addition, the cooling air that has undergone product heat exchange becomes 500-600 ℃, which is used as fuel for combustion twice and enters the kiln to improve thermal efficiency and save energy.

Summary of calcined limestone data:

1. The loss on ignition of limestone is 38-41, based on which it is calculated that burning one ton of limestone requires 1.61-1.69 tons of raw materials.
2. Effective calcium content ≥ 93% -95%, activity level 300-420ml (under normal circumstances, 360+)
3. Burning one ton of lime requires approximately 5000 kcal of coal, 200kg, 700m ³ of converter gas, and 120m ³ of natural gas (pressure ≥ 18-25Kpa)
4. Required coal powder indicators: (bituminous coal, anthracite) moisture content ≤ 10, volatile matter 20% -30%, ash content<10%, sulfur ≤ 1%, low calorific value ≥ 4800
5. Kiln type selection:

Selection of Preheaters：

Qualified materials such as limestone, dolomite, magnesite, etc. are transported to the storage bin above the preheater, and the materials are dropped into the preheating chamber of the preheater through ten discharge pipes. The induced draft fan extracts the hot exhaust gas at around 800-900 ℃ discharged from the kiln from bottom to top through the material layer of the preheating chamber. The descending materials absorb the heat in the exhaust gas and undergo preheating before calcination. When limestone particles are heated above 800 ℃, the outer layer of the particles begins to undergo decomposition reactions, and CO2 (gas) gradually separates from CaCO3. Theoretical practice has shown that the decomposition temperature of CaCO3 is about 870-920 ℃. In a rotary kiln with a vertical preheater, this vertical heating process generally takes about 120 minutes.
In the preheating chamber of the preheater, the preheated material is pushed into the rotary kiln by alternating hydraulic push rods. Each push rod can push about 170kg of material at a time, and the push head is made of special heat-resistant alloy steel.
Each hydraulic push rod is equipped with one hydraulic station, and the pushing time of the push rod can be adjusted through the hydraulic system. By adjusting the numerical settings of the control computer, the time interval of the push rod's alternating work can be adjusted to accurately control the production.
The material of the preheater push head is made of heat-resistant steel castings, and the material of the transfer chute extending into the rotary kiln nozzle is made of heat-resistant steel castings.

Rotary kiln barrel part：

Q235B refers to carbon structural semi killed steel with a yield point of 235 MPa.
Q235B has a certain degree of elongation, strength, good toughness, and castability, and is easy to punch and weld. It is widely used in the manufacturing of general mechanical parts. Mainly used for welding structural components with high quality requirements in construction and bridge engineering.
High quality carbon structural steel is supplied according to its chemical composition and mechanical properties. The low content of sulfur, phosphorus, and non-metallic inclusions in steel indicates good quality and uniformity of microstructure, and is commonly used in various important mechanical structural parts that require heat treatment.

Q235B element content
Carbon C: ≤ 0.20%
Silicon Si: ≤ 0.35%
Manganese Mn: ≤ 1.4%
Sulfur S: ≤ 0.045%
Phosphorus P: ≤ 0.045%
Chromium Cr: allowable residual content ≤ 0.30%
Nickel Ni: allowable residual content ≤ 0.30%
Copper Cu: allowable residual content ≤ 0.30%

Gear material:

The gear material is ZG45 (ZG310-470), with a C content of 0.42-0.5%, Si content of 0.17-0.37%, Mn content of 0.5-0.8%, Cr content ≤ 0.25%, Ni content ≤ 0.3%, Cu content ≤ 0.25%, density of 7.85g/cm ³, elastic modulus of 210GPa, and liquid phase temperature of around 1495 ℃. Heat treatment: normalizing at 850 ℃, quenching at 840 ℃, tempering at 600 ℃. If the hardness before tempering is greater than HRC55 after quenching, it is qualified According to the GB/T699-1999 standard in China, the tensile strength is 600MPa, the yield strength is ≥ 355MPa, the elongation rate is 16%, the cross-sectional shrinkage rate is 40%, and the impact energy is 39J

Refractory part：

Different refractory materials have different technical parameters such as load softening temperature, wear resistance, and insulation. The selection of refractory materials should be based on the temperature and price acceptance of the materials themselves.