Limestone Grinding Mill and Production Line Process

Limestone Grinding Mill is equipment used to grind limestone into powder. Raymond Mill delivers the best cost performance for processing medium and fine limestone powder of 80 to 400 mesh. For ultra-fine powder above 400 mesh, the Ultra-fine Ring Roller Grinding Mill is the preferred option. If large-scale and high-output production is required, Vertical Roller Mill is recommended. The production line shall control feed particle size and material moisture, and be equipped with iron removers to guarantee the quality of finished limestone powder.

What is Limestone?

Limestone is a sedimentary rock mainly composed of calcium carbonate (CaCO₃), containing trace impurities such as silicon, aluminum and iron. Its color varies with impurities, generally white, grayish white, blue gray and other colors. Its Mohs hardness is about grade 3, with a density of 2.5 to 2.7 g/cm³. It belongs to medium-soft material, brittle and easy to grind. Limestone powder produced by pure physical crushing and grinding process is also known as Ground Calcium Carbonate (GCC). With excellent chemical stability, good whiteness and high filling value, this powder is widely applied in building materials, chemical industry, metallurgy, environmental protection and other fields.

Precautions for Limestone Grinding Production Line

Feed Particle Size: Generally, the smaller the particle size of material entering the mill, the lower the energy consumption and the higher the output of the grinding mill. Large limestone blocks must be crushed by crusher to meet the feed size requirement of the grinding mill (usually less than 30 to 40 mm). Excessively large or uneven feed particle size will aggravate the wear of grinding rollers and grinding discs, and even cause main engine vibration. It is recommended to equip a variable frequency feeder at the feeding section to ensure uniform and quantitative material feeding into the grinding mill.

Moisture Content: Limestone usually has low natural moisture content. If the moisture content exceeds 5 percent, blockage and low efficiency may easily occur during grinding. It is necessary to consider equipping drying equipment or selecting a grinding mill with drying function.

Impurity Control: Limestone may contain hard impurities such as silica and iron substances. If mixed into the grinding mill, they will seriously damage grinding rollers, grinding discs and even the main engine. Iron removers and screening equipment shall be installed on the conveyor belt before feeding to remove impurities. It can protect equipment and prevent iron contamination, so as to ensure the purity and whiteness of finished limestone powder.

Equipment Wear: Although limestone has low hardness, long-term grinding will still cause wear to the grinding mill. It is recommended to adopt wear-resistant materials for core grinding components such as grinding rollers and grinding rings.

How to Select a Suitable Limestone Grinding Mill?

Raymond Mill

Raymond Mill has high cost performance for limestone processing within the range of 80 to 400 mesh. Its grinding rollers and grinding rings are made of high manganese steel, offering long wear-resistant service life when processing limestone with high calcium carbonate content. The finished limestone powder features uniform particle size and stable sieve passing rate for 325 mesh. The system operates under negative pressure to effectively suppress dust leakage. With economical price, it is suitable for fine limestone powder processing such as power plant desulfurization, asphalt pavement filler, glass raw material and feed additive.

Ultra-fine Ring Roller Grinding Mill

Ultra-fine Ring Roller Grinding Mill is the preferred equipment for producing 400 to 2500 mesh ultra-fine limestone powder. It adopts multi-layer grinding principle and high-precision turbo classification technology to ensure concentrated particle size distribution of finished limestone powder, meeting strict fineness requirements of high-end industries. It consumes less power compared with jet mill. It applies to medium and small-scale ultra-fine limestone powder processing for plastics, coatings, papermaking, rubber, sealant and adhesive. If larger production capacity is required, Ultra-fine Vertical Roller Mill can be adopted as the solution with higher corresponding investment.

Vertical Roller Mill

Vertical Roller Mill requires high initial investment cost yet low operating energy consumption. Its unit power consumption for limestone grinding is much lower than other grinding equipment. It has strong drying capacity and can directly process limestone with moisture content up to 15 percent, eliminating the need for pre-drying equipment. Grinding rollers do not make direct contact with grinding discs, which effectively reduces metal contamination and guarantees the whiteness and purity of finished limestone powder. It is suitable for large-scale and high-output limestone powder production for large power plant desulfurization projects, sintering agents for steel plants and large building material bases.

Technological Process of Limestone Grinding Production Line

In a limestone grinding production line, vibrating feeder evenly sends large limestone blocks ≤400 mm into jaw crusher to be crushed into 30 to 50 mm gravel. Iron impurities are removed by iron remover. Hammer crusher may be used to further reduce particle size to ≤20 mm according to grinding mill type. Qualified limestone material is conveyed by elevator and stored in raw material silo, then quantitatively fed into the main mill by electromagnetic vibrating feeder for grinding and classification. The collection system generally uses cyclone collector for primary collection and pulse bag dust collector for secondary purification to ensure qualified tail gas emission. The whole system runs under negative pressure without dust overflow. Finally, finished limestone powder is collected by screw conveyor and transported by elevator into finished product silo for packaging.

Application Scenarios of Limestone Grinding Mill

Frequently Asked Questions about Limestone Grinding

What to Do If the Powder Produced by Limestone Grinding Mill Turns Black?

Under normal circumstances, raw limestone has high whiteness and the produced powder will not turn black. If the raw ore contains high impurities, ore washing equipment can be used for purification. Iron remover shall be installed before grinding to effectively remove impurities in limestone raw materials and keep the finished powder white and pure. During grinding, iron scraps generated from worn grinding rollers and grinding rings will mix into powder and cause blackening. Therefore, core grinding components are recommended to adopt wear-resistant materials such as high chromium alloy to reduce iron scrap generation at the source.

Which is Better for Limestone Processing, Raymond Mill or Vertical Roller Mill?

There is no absolute better option between Raymond Mill and Vertical Roller Mill for limestone processing; only the more suitable one. Vertical mill suits continuous operation with large output, energy saving and environmental protection, yet it demands high upfront investment. Raymond Mill features low investment cost and simple maintenance, suitable for medium and small-scale limestone powder production of 80 to 400 mesh. Equipment selection shall comprehensively consider raw material characteristics, finished fineness, production capacity and investment budget.

Can Limestone Grinding Mill Perform Activation Modification Directly?

Limestone powder used in high-end industries such as plastics and rubber needs coating treatment (such as adding stearic acid) to improve compatibility with resin. This process is called activation modification. It should be noted that modifier cannot be added directly inside the grinding main machine, because high temperature and impact inside grinding chamber will destroy molecular structure of modifier and cause coating failure. The correct process is to grind qualified limestone powder first, and then send the powder into modifier for modification treatment.

Which Grinding Mill to Choose for Limestone Raw Material with High Silicon Content?

Some limestone with high silicon content has Mohs hardness close to grade 7 and causes fast equipment wear. Ordinary Raymond Mill should be avoided, otherwise grinding rollers and grinding rings may need replacement within several days with unbearable cost. Vertical Roller Mill is a good choice. Its grinding rollers and discs adopt premium material and can be flipped for reuse with high utilization rate. If the required fineness is not high, about 80 mesh, ball mill is also an alternative. Ball mill is especially good for processing hard materials, and the replacement cost of liners and steel balls is relatively controllable. In addition, limestone with high silicon content usually contains high iron impurities, so multiple iron removers must be installed, otherwise the color of finished powder will turn dark.