In the solid-liquid separation processes of the mining, chemical, and environmental protection industries, the selection of the appropriate thickener is a critical step. In traditional design, to ensure operational safety and cope with fluctuations in ore throughput, feed concentration, and varying operator skill levels, there is a tendency to select a larger thickener size. This “better oversize than undersize” philosophy, while ensuring short-term production stability, brings significant drawbacks: large equipment footprint, substantially increased capital costs, and during operation, issues such as energy waste due to an “overpowered” setup, difficulty in controlling underflow concentration, and increased flocculant consumption. So, how can we break the deadlock of oversized selection while ensuring processing capacity? The key lies in how flocculants are used.
Ⅰ. Flocculants: The “Catalyst” for Efficient Thickener Operation
To solve the problem of oversized thickener selection, we must first understand how to enhance the unit-area processing capacity of existing equipment. Flocculants are precisely the key to achieving this.
Flocculants (typically high-molecular-weight polyacrylamides) are chemical aids that promote the aggregation and settling of suspended particles. Their working principle is based on “adsorption bridging” and “charge neutralization.” When a flocculant is added to the pulp, long-chain polymer molecules adsorb onto the surfaces of multiple fine particles, linking them like ropes into larger flocs. These flocs settle much faster than individual particles, significantly reducing the settling time required in the thickener tank.
By adding flocculants, the unit-area settling flux is greatly increased. This means that the throughput originally requiring a larger thickener area can now be achieved with a smaller unit, provided efficient flocculation reactions. Therefore, the addition of flocculants essentially provides a “technical capacity expansion” for the thickener, making it possible to move away from relying on oversized equipment.
Ⅱ. Dosing System: From “Empirical Dosing” to “Precision Control”
Although flocculants are highly effective, their use presents a core contradiction: too little flocculant results in poor settling, failing to achieve clear overflow and target underflow concentration, thus limiting capacity; too much flocculant not only wastes chemicals but can also lead to flocs that are too loose or sticky, increasing rake torque and even causing “rake burial” accidents.
To resolve this contradiction, ZJH Company has introduced the Automatic Flocculant Dosing Device. As a core auxiliary equipment in modern solid-liquid separation processes, it transforms traditional “manual empirical dosing” into “data-driven precision dosing.”
- Working Principle
(1) Feeding System:
A large-capacity hopper with a specially designed feed screw ensures smooth material delivery. The screw conveyor provides uniform discharge and easy adjustment. An electric heater inside the dosing funnel prevents dry powder from caking due to moisture, and a vibration device prevents clogging, ensuring optimal conditions for thorough mixing of powder and water. A filter screen at the top of the hopper automatically removes lumps or other impurities from the dry powder.
(2) Automatic Water Supply System:
Comprising a solenoid valve, flow meter, and piping. When the level sensor detects a low liquid level, it sends a signal to the PLC. The PLC calculates the required concentration ratio based on the existing solution concentration and preset target concentration, then automatically opens and adjusts the solenoid valve flow rate and the feeder rate accordingly. The flow meter can display real-time flow and accumulate monthly, quarterly, annual, and total flow data.
(3) Automatic Mixing System:
Mainly composed of three tanks, three dissolution agitators, and a premixer. The screw feeder discharges dry powder into the premixer for thorough mixing before entering the solution tank for agitation. This prevents powder agglomeration and ensures complete dissolution without waste. The agitators continuously mix the powder in the dissolution tank to ensure full dissolution. The dissolved solution then enters the aging tank, where continuous stirring completes the aging process. The aged, fully prepared solution enters the third tank (storage tank) for use by the dosing system.
(4) Automatic Dosing System:
Consists mainly of a metering pump, safety valve, and backpressure valve. The control system automatically collects wastewater treatment flow data via sensors and adjusts the dosing rate (i.e., metering pump flow) in real time. The safety valve, backpressure valve, and damper ensure safe and stable operation of the dosing system.
(5) Automatic Control System (PLC):
Composed of a PLC, touch screen, and electrical components (remote network connection and remote monitoring available upon request). Two control modes: manual and automatic. Parameters such as real-time liquid level, prepared solution concentration, solution volume, inlet water flow, feeder rate, hopper material level, and metering pump flow can be transmitted to the upper computer. Remote start/stop, water feed rate adjustment, and feeder rate adjustment are possible, enabling true remote monitoring and control. The entire process—from water intake, powder feeding, dilution, aging, storage, to dosing—operates unattended with remote automated control, significantly reducing operating costs.
- Core Advantages
(1) Highly Integrated, Small Footprint:
The device is an integrated unit that combines mixing, aging, storage, and control systems into a compact structure. Compared to traditional decentralized dosing systems, the footprint is greatly reduced, making it especially suitable for retrofit projects or new projects with space constraints.
(2) High Degree of Automation, Intelligent Control:
The entire system is operated by a PLC intelligent control center with inverters and various electrical components, achieving fully automatic operation from water intake, powder feeding, mixing, aging, to dosing. The liquid level sensing system provides real-time feedback on the chemical storage tank level. The PLC automatically starts or stops preparation based on preset parameters, requiring no manual attendance. It offers high operational sensitivity and simple operation.
(3) Easy Installation, Simple Maintenance:
The modular design allows the equipment to be operational on site with only water and power connections, requiring a short installation period. The user-friendly interface and control panel allow parameter adjustments via button settings, reducing technical requirements for operators.
(4) Reliable Operation, Good Safety Performance:
The equipment has an extremely low failure rate. In case of abnormal conditions, the system automatically shuts down and triggers an alarm, effectively preventing equipment damage and chemical leakage. Key operational parameters can be controlled locally or remotely to meet different management needs.
(5) Strong Corrosion Resistance, Suitable for Harsh Conditions:
All components in contact with the chemical medium are made of stainless steel, offering excellent corrosion resistance. This ensures long-term stable operation in complex environments such as mining, metallurgy, and chemical industries, extending the equipment’s service life.
III. Conclusion
In summary, during thickener selection and operation, relying solely on enlarging equipment size to cope with process uncertainties is a high-cost, low-efficiency traditional approach. By introducing flocculants, we leverage chemical settling principles to greatly enhance physical settling efficiency. Furthermore, the application of the Automatic Flocculant Dosing Device maximizes the effectiveness of this chemical enhancement.
Through precise dynamic control, it not only resolves the capital waste problem caused by oversized equipment selection but also fundamentally optimizes thickener operating performance, achieving an optimal balance between settling efficiency and chemical consumption.
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