Calcium hydroxide pneumatic conveying
Calcium hydroxide pneumatic conveying
The core of calcium hydroxide pneumatic conveying is to utilize the kinetic or static pressure energy of air to form a stable gas-solid two-phase flow of calcium hydroxide powder in a closed pipeline, completing the transportation from the storage bin to the point of use, and achieving gas separation and exhaust gas purification at the end.
Unlike ordinary mineral powder, calcium hydroxide has a fine particle size, high surface activity, and is prone to react with moisture in the air to form hard lumps. The key to its transportation principle lies in "preventing agglomeration, blocking pipes, and moisture absorption", rather than simply power transmission. The overall workflow still follows the three major stages of "feeding conveying separation", but each stage has a targeted principle adaptation. The mainstream is divided into three modes: positive pressure dilute phase, positive pressure dense phase, and negative pressure suction. The following is the general principle+core logic of the mode:
1、 General core working principle
Arch breaking and bridge prevention - Calcium hydroxide is prone to forming "bridges" in storage due to moisture absorption and aggregation, making it difficult to cut naturally. Therefore, before starting the conveying process, it is necessary to use warehouse wall vibration or arch breaking devices to break the material aggregation structure, making the powder loose and laying the foundation for subsequent uniform feeding. This is the unique pre principle that distinguishes calcium hydroxide transportation from other dry powders.
Mixing of feed and gas - Loose calcium hydroxide is controlled and evenly fed into the conveying pipeline through a dedicated gas locking feeding device. At this point, the airflow enters the pipeline from the power source and is fully mixed with the material: the airflow breaks the adhesive force between the material particles, causing the calcium hydroxide particles to be carried or aggregated into loose clusters by the airflow, forming a gas-solid two-phase flow that can be transported. Key adaptation: The feeding device needs to have good airtightness to prevent external humid air from entering the pipeline and reacting with calcium hydroxide.
Pipeline transportation - Gas solid two-phase flow moves forward in pipelines relying on the kinetic or static pressure energy of the airflow. Calcium hydroxide particles are lightweight and strongly influenced by air flow, but due to their tendency to aggregate, they need to be designed through pipeline air supply and optimized bend curvature to avoid particle deposition and agglomeration in the pipeline, which can cause pipe blockage. The entire pipeline is sealed to isolate external moisture and dust leakage.
Gas material separation and exhaust gas purification - When the material reaches the endpoint, it enters the separation equipment. Calcium hydroxide particles separate from air under the action of gravity or centrifugal force and fall into the receiving bin; The exhaust gas carrying a small amount of fine dust enters the dust removal equipment for purification before being discharged. Key adaptation: Anti adhesive filter materials should be selected for dust removal equipment to prevent calcium hydroxide dust from adhering to the filter bag and causing blockage.
2、 The core working principles of the three mainstream modes
Scheme 1: Positive pressure dilute phase pneumatic conveying
Core power: Relying on the kinetic energy of the airflow, it pushes the calcium hydroxide particles to be transported in a suspended state.
Working logic: The power source provides positive pressure airflow at the starting point, and the feeding device continuously feeds the material into the pipeline. The airflow carries the material forward at high speed and reaches the receiving bin at the end point.
Adaptation logic: Calcium hydroxide is lightweight and easy to transport. The dilute phase mode can meet the needs of medium to short distance and continuous feeding. The equipment structure is simple and easy to maintain, suitable for scenarios such as dry desulfurization tower calcium spraying and sewage treatment dosing.
Option 2: Positive pressure dense phase pneumatic conveying
Core power: Relying on the static pressure energy of the airflow, it drives the formation of loose material plugs in calcium hydroxide to move forward.
Working logic: Using intermittent feeding from the sending tank, high-pressure airflow causes the material in the pipeline to alternate between "material plugs+gas plugs". The material is pushed forward at low speed by the pressure difference between the material plugs, and the end is discharged to the receiving bin.
Adaptation logic: Low speed transportation can reduce the frictional heat generation and agglomeration between calcium hydroxide particles, while reducing pipeline wear. It is suitable for long-distance, high concentration transportation, such as centralized feeding from raw material warehouses to multiple production workshops in the factory area.
Plan 3: Negative pressure pneumatic conveying
Core power: Relying on the negative pressure difference inside the pipeline, the external air and materials are sucked into the pipeline together.
Work logic: The power source forms negative pressure at the endpoint, and the material is simultaneously sucked into the pipeline from multiple feeding points, transported through the main pipe to the endpoint separator, completing the separation of gas and material.
Adaptation logic: Negative pressure environment can prevent the leakage of calcium hydroxide dust, suitable for centralized recovery or transportation of calcium hydroxide powder in multiple storage warehouses, and can avoid the entry of humid air from the outside into the system.
3、 Core principles and key points of calcium hydroxide transportation
Preventing moisture absorption is a prerequisite: the entire process is enclosed and sealed, isolating the outside humid air to prevent calcium hydroxide from reacting and clumping, which is the core of smooth transportation;
Preventing agglomeration is key: by breaking the arch, replenishing air, optimizing flow rate, breaking the material agglomeration structure, and avoiding pipe blockage;
Low abrasion adaptation: Calcium hydroxide has weak abrasion resistance and does not require wear-resistant pipes. The focus is on the smoothness of the pipes to reduce particle adhesion.
Case 1: Dry desulfurization system in thermal power plant | Calcium hydroxide powder from raw material warehouse to desulfurization tower injection port
Industry:Electricity
Core requirements:Continuous and stable feeding, precise control of calcium sulfur ratio in the desulfurization tower is required; The material is dry calcium hydroxide powder, with a medium conveying distance, requiring a simple system and easy maintenance to avoid a decrease in desulfurization efficiency due to pipe blockage.
Core requirements:Continuous and stable feeding, precise control of calcium sulfur ratio in the desulfurization tower is required; The material is dry calcium hydroxide powder, with a medium conveying distance, requiring a simple system and easy maintenance to avoid a decrease in desulfurization efficiency due to pipe blockage.
System configuration:Raw material warehouse+arch breaking device+air lock feeder+positive pressure dilute phase conveying pipeline+desulfurization tower top spraying device+end exhaust dust removal.
Workflow:
1. The calcium hydroxide powder in the raw material warehouse is dispersed by the arch breaking device to prevent bridging, and is uniformly and continuously fed into the positive pressure conveying pipeline through the air lock feeder;
2. Positive pressure airflow wraps the material into a suspended state and transports it along the pipeline to the top of the desulfurization tower;
3. The material is directly sent into the desulfurization tower reaction zone through the injection device to participate in the flue gas desulfurization reaction;
4. A small amount of unreacted fine dust at the end is collected by the exhaust dust removal device to avoid polluting the environment.
Application effectiveness:
Realize continuous and uniform supply of desulfurizer, stable reaction efficiency of desulfurization tower, precise control of calcium sulfur ratio, and reduce waste of calcium hydroxide;
The system structure is simple, without complex pressure vessels, and daily maintenance only requires checking the feeder and pipeline air supply device, with low operation and maintenance costs;
Fully enclosed transportation throughout the process, completely solving the dust problem in the desulfurizer feeding process and meeting the environmental protection requirements of power plants.
Case 2 Large Chemical Industrial Park | Calcium Hydroxide Powder from Centralized Raw Material Warehouse to Multiple Workshops
Industry:chemical industry
Core requirements:Long distance and multi unloading point transportation, with the raw material warehouse located at the edge of the park, requires feeding to reaction vessels in three different workshops; Require low energy consumption and low material damage, avoid excessive energy consumption and pipeline blockage caused by long conveying distances, and adapt to the intermittent feeding needs of multiple workshops.
System configuration:Centralized raw material warehouse (equipped with arch breaking and insulation devices)+sending tank (warehouse pump)+positive pressure dense phase conveying main pipe+pipeline distributor+indirect collection of each vehicle+exhaust dust removal system.
Workflow:
1. After arch breaking and insulation treatment, the calcium hydroxide powder in the raw material warehouse is loaded into the sending tank in batches;
2. After the tank is pressurized, the material is formed into loose material plugs by high-pressure and low-speed airflow, and the material plugs are pushed along the main pipe by static pressure energy;
After the materials arrive at the distributor, they are switched to the corresponding receiving warehouse for unloading according to the feeding instructions of each workshop;
4. The receiving warehouse completes the separation of gas and material, and the material falls into the workshop buffer hopper. The exhaust gas is discharged after dust removal to meet the standard.
Application effectiveness:
Adopting dense phase plug flow transportation, with low wind speed and much lower energy consumption than dilute phase systems, suitable for long-distance transportation needs;
By using pipeline distributors to achieve "one warehouse for multiple workshops", there is no need to separately configure conveying systems for each workshop, greatly reducing equipment investment;
Low speed transportation reduces the frictional heat generation and agglomeration between calcium hydroxide particles, ensuring the quality of the material is not compromised. Additionally, the pipeline has no wear and tear, resulting in a long service life.
Case Three: Calcium Hydroxide Production Plant | Dust Recovery from Finished Product Storage Bin Discharge Port+Return Transportation of Unqualified Materials
Industry:Calcium processing
Core requirements:Multi point material collection and low dust recycling. The discharge ports of the three finished product silos in the production workshop are prone to dust generation, and the screened unqualified fine powder needs to be collected from the three screening stations and recycled to the raw material reprocessing silo; Require no dust leakage throughout the entire process to avoid polluting the production workshop, while also preventing external humid air from entering the system and causing material clumping.
System configuration:3 negative pressure suction nozzles at the discharge port+3 suction points at the screening station+negative pressure conveying branch/main pipe+final separator+negative pressure fan+recycling bin.
Workflow:
1. Start the negative pressure fan to create a negative pressure field inside the main pipe;
2. The dust from the discharge port of the silo and the unqualified materials from the screening station are respectively sucked into the branch pipe through their respective suction nozzles/suction points and merged into the main pipe;
3. The gas mixture is separated in the final separator, and the calcium hydroxide powder settles in the recycling bin and is then sent back to the production system for processing;
4. The purified exhaust gas is discharged through a negative pressure fan, and there is no dust leakage in the workshop.
Application effectiveness:
Under negative pressure, dust is only inhaled into the pipeline, and there is no dust at the discharge port and screening station in the workshop. The production environment has been greatly improved and meets occupational health standards;
Realize "3 discharge ports+3 screening stations" for simultaneous feeding at 6 points and centralized unloading at 1 point, without the need for manual cleaning of dust and unqualified materials, saving labor costs;
The system only inhales a small amount of air at the material collection point. By setting a dry air supply port at the suction nozzle, it effectively prevents moist air from entering and causing material clumping, ensuring smooth and unobstructed transportation.