Cement pneumatic conveying is a technology that uses air as a power source to transport cement powder in a closed pipeline. Its core advantages are dust-free sealing, flexible layout, and high degree of automation. The two most commonly used schemes in cement plants are dilute phase positive pressure and dense phase high pressure. The selection is determined by the conveying distance, capacity, and anti-wear requirements.

Positive pressure conveying (pressure conveying): The pressure inside the pipeline is higher than atmospheric pressure, and the material is pushed forward by thrust, suitable for long-distance and high flow conveying.

Negative pressure conveying (suction): The pressure inside the pipeline is lower than atmospheric pressure, and the material is sucked in and conveyed by suction, suitable for short distance and multi-point material retrieval.

2、 Typical system composition

Air source: Provides airflow power, such as Roots blowers, compressors, and vacuum pumps.

Feeding device: evenly feed cement into pipelines, such as rotary valves, bin pumps, and Venturi feeders.

Transport pipeline: a closed channel that can be arranged horizontally, vertically, or curved.

Gas material separation: such as a cyclone separator, separates cement from the airflow.

Dust removal and purification: such as bag filters, which treat exhaust gas before discharge.

3、 Basic workflow

Feeding and mixing: Cement enters the feeding device from the silo and mixes with the airflow. In some scenarios, cement will be fluidized, making it easier to transport.

Pipeline transportation: The mixed cement particles move along the pipeline in a suspended state (dilute phase) in high-speed airflow or in a slug/group flow (dense phase) at higher air pressure.

Terminal separation: After reaching the destination, the separator intercepts the cement particles and drops them into the storage bin.

Exhaust gas treatment: The airflow carrying fine powder is purified by a dust collector and discharged in compliance with standards.

Gas solid two-phase flow: Air is the continuous phase, cement particles are the dispersed phase, and transportation is achieved by overcoming gravity and pipe wall friction through the drag force of the airflow.

Fluidization: When the airflow passes through the cement layer, the gaps between particles are filled with gas, presenting a fluid like state and reducing transport resistance.

Dilute phase and dense phase: The dilute phase maintains particle suspension by high airflow velocity; Dense phase relies on air pressure to push the material plug or group forward, with lower speed but higher conveying concentration.

Application scenario: Cement plant raw material station or finished product warehouse, unloading bulk cement from transport vehicles into the factory storage.

System composition: mobile/fixed suction nozzle, telescopic hose, conveying pipeline, negative pressure separator (cyclone), bag filter, vacuum pump.

Working process: After the system is started, the vacuum pump forms a negative pressure airflow in the pipeline. Insert the suction nozzle into the discharge port of the car tanker during operation, and the atmospheric pressure will mix the cement and air inside the tanker and press it into the conveying pipeline. The gas mixture is sucked along the pipeline to the factory area, first entering the separator. Cement settles into the storage due to gravity, and the dusty airflow is filtered by a bag filter. The purified air is then discharged into the atmosphere by a vacuum pump.

Application scenario: In the finished product section of a cement plant, materials from the cement warehouse are transported to packaging machine silos or bulk truck shipping points.

System composition: bottom unloader, bin pump, air compressor, conveying main pipe, branch valve, dust collector.

Working process: Cement enters the silo type conveying pump from the bottom of the warehouse, and the pump body is inflated to make the material fluidized and establish pressure. When the set conditions are reached, the discharge valve opens and compressed air pushes the cement to move at high speed along the conveying pipeline. By using the branch valves on the pipeline, cement can be transported separately to the silos in the packaging workshop or to the bulk shipping heads at different locations. The exhaust and trace dust at the end of the transportation are treated by a dust collector to achieve closed transportation.

Application scenario: In the raw material preparation section of a cement plant, the raw material powder collected by the waste gas collector at the tail of the raw material mill is transported back to the raw material homogenization silo or kiln elevator.

System composition: dust collector ash hopper, negative pressure conveying branch pipe, collector, positive pressure transmitter, conveying pipeline.

Working process: The raw material ash separated by the dust collector is centrally sucked into the collector through multiple negative pressure branch pipes. After completing the separation of gas and material in the collector, the material falls into the positive pressure sending device below, and is then transported to the raw material homogenization silo or kiln tail feeding system at a higher position by the positive pressure airflow. This system uses negative pressure to complete multi-point collection and positive pressure to complete long-distance high head transportation.