Grain unloading ship pneumatic conveying
Grain unloading ship pneumatic conveying
The essence of grain unloading pneumatic conveying is negative pressure suction pneumatic conveying, which uses air as the conveying medium and utilizes the airflow generated by negative pressure in the pipeline to "suck" grain particles from the ship to the dock side, and then completes the unloading operation through gas-solid separation and unloading buffer. The entire process relies on closed pipelines for operation, which can not only avoid the scattering and loss of grain, but also control dust from the source, making it the mainstream environmental protection solution for grain unloading in ports.
The overall workflow operates in a closed-loop system consisting of four stages: material retrieval, transportation, separation, and unloading. At the same time, a dedicated adaptation mechanism is designed to prevent breakage and blockage based on the characteristics of grain particles. The specific principle is as follows:
1、 Core workflow
1. Negative pressure field construction: Establishing a power foundation
The system power source is arranged at the end of the dock shore, and after starting, it creates a negative pressure environment inside the entire conveying pipeline that is lower than the external atmospheric pressure. At this point, a pressure difference is formed between the external atmosphere and the interior of the pipeline, which is the core driving force for the movement of grain particles and the essence of "suction".
2. In ship material retrieval: gas material mixing startup
The dock operators operate the adjustable and extendable unloading arm, and insert the front suction nozzle into the grain pile inside the cabin. Due to the negative pressure inside the pipeline, external air will pass through the suction nozzle at high speed, and at the same time, it will "wrap" the grain particles around the suction nozzle, completing the initial mixing of gas and material at the suction nozzle, forming a two-phase flow of gas and grain, and entering the conveying pipeline. For the leftover materials in the corners of the cabin, they can be collected from the entire cabin without blind spots by moving the suction nozzle or using an auxiliary scraping device.
3. Pipeline transportation: Collaborative migration of gas and materials
Under the driving force of negative pressure airflow, the two-phase flow of gas and grain flows along the unloading arm pipeline and the shore side fixed pipeline towards the end of the shore side. During the transportation process, the kinetic energy of the airflow is transferred to the grain particles, pushing them forward along with the airflow. Grain particles move in a suspended or slightly sliding state inside the pipeline, completely enclosed in a closed space, with no grain leakage or dust flying.
4. Shore separation: effective separation of gas and grain
When the two-phase flow of gas and grain reaches the separation equipment on the shore, the velocity of the airflow slows down, and the grain particles separate from the air under the action of gravity and centrifugal force:
Grain particles: They settle from the airflow and fall into the storage bin or unloading equipment below;
Dust laden air: continues to enter the subsequent dust removal system, completes dust purification, and meets emission standards.
5. Unloading buffer: connecting subsequent processes
The separated grains are temporarily stored in the buffer warehouse, and then transported to the dock yard, silo or subsequent transport vehicles through the unloading device, completing the entire unloading process.
2、 Exclusive adaptation principle of grain materials
Grain belongs to granular materials, which are brittle, easy to break, and have the characteristics of good fluidity and poor adhesion. Therefore, the pneumatic conveying of grain unloading ships has added two key adaptive designs on the basis of the universal negative pressure principle:
Low crushing design: By optimizing the structure of the suction nozzle and controlling the flow rate of the pipeline, it avoids severe collisions and friction of grain particles during suction and transportation, minimizes the generation of crushed grains, and ensures grain quality;
Anti clogging design: Grain particles have no adhesion and are not easily blocked by sedimentation. The system will also install a supplementary air device at key positions in the pipeline. If material accumulation occurs locally, it can be eliminated by supplementary air flow to ensure smooth transportation.
3、 Core Features
Thorough dust control: In a negative pressure environment, even if there is a small leak in the pipeline, it will only inhale external air and will not leak food or dust, which is suitable for port environmental protection requirements;
Flexible homework: The unloading arm can be flexibly raised, retracted, and adapted to different ship types, different draft depths, and the material retrieval needs at different positions inside the cabin;
Low grain loss: Closed conveying avoids the scattering loss of grain caused by traditional grab bucket unloading ships, while low crushing design reduces the quality loss of grain itself.
Case 1: Application of Mobile Negative Pressure Ship Unloader
Applicable scenarios:Inland ports and ships ranging from thousand to ten thousand tons are mainly used for corn and wheat, with a variety of ship types, multiple batches, unstable berths, and narrow land areas at the docks, making it impossible to arrange large fixed corridors.
materialCorn and wheat
System configuration:Adopting a mobile negative pressure pneumatic ship unloader. The equipment integrates a suction nozzle, telescopic arm, separator, dust collector, and fan, and can move along the dock front track or use tire type movement.
Workflow:
1. The equipment is docked at the edge of the work vessel and the suction nozzle is placed in the cabin.
2. Start the negative pressure system to suck the grain ashore and complete the gas grain separation in this machine.
3. The separated grains are directly fed into the mobile belt conveyor at the dock through the discharge port at the tail of the machine.
4. Short distance transportation by belt conveyor to the rear silo or loading point.
Addressing pain points:Solved the problem of high investment and poor flexibility in fixed equipment.
Application effectiveness:Flexible equipment transfer, one device can serve multiple berths; Equipped with dust removal function, meeting the environmental protection requirements of inland ports; Low initial investment, suitable for small and medium-sized terminals with diverse cargo types.
Case 2: Fixed Negative Pressure Unloading System
Applicable scenarios:Coastal deep-water berths, ocean going giant ships of over 100000 tons, with long continuous operation time and large unloading volume, mainly for unloading soybeans and corn, requiring high efficiency and automation, and supporting large silos in the rear.
materialsoybeans, corn
System configuration:Adopting a fixed double tube negative pressure pneumatic ship unloader combined with a shore side long-distance conveying system. The ship unloader is fixed at the forefront of the dock, equipped with a huge cantilever that can pitch and retract, and connected to buried or elevated pipelines at the rear.
Workflow:
1. Use the mobile scraper (auxiliary equipment) in the cabin to scrape the grain towards the suction nozzle.
2. The negative pressure system sucks the grain into the separator at the head of the unloader, completing the preliminary separation.
3. Grain falls into a large capacity buffer bucket on the shore.
4. The feeder under the buffer hopper feeds the grain into the positive pressure conveying pipeline or large angle belt conveyor, and transports it to the silo group several kilometers away from the rear.
Addressing pain points:Solved the problems of high dust, high losses, and the need for extensive manual cleaning in traditional grab bucket unloading ships.
Application effectiveness:Realize fully enclosed transportation, with almost no dust in the dock operation area; High degree of automation, reducing cabin cleaning workload by over 80%; The system runs stably and can meet the 24-hour continuous unloading requirements.
Case 3: Negative pressure dust removal funnel system
Applicable scenarios:There is an existing bulk cargo terminal equipped with grab bucket unloaders. Due to stricter environmental policies, the dust generated during grab bucket unloading exceeds the standard, requiring low-cost and rapid environmental upgrades without changing the original unloading process.
materialRice and miscellaneous grains
System configuration:Install a sealed cover and negative pressure pneumatic dust removal system above the hopper of the original grab bucket unloader. This is a hybrid solution of "pneumatic conveying+mechanical conveying".
Workflow:
1. The grab bucket continues to grab grain and unload it into the hopper as usual.
2. The dust generated during unloading is strongly sucked away by the negative pressure cover above the hopper.
3. The dusty airflow enters the negative pressure system, and the dust is separated and collected.
4. The collected materials are sent back to the main material flow through a small conveying device.
Addressing pain points:Solved the dust pain point of the grab bucket operation at the old dock with minimal renovation cost.
Application effectiveness:The dust concentration at the dock has significantly decreased and passed the environmental protection inspection; The original unloading efficiency is basically not affected; The collected dust is recycled into the feed stream, reducing food loss.