The buffering equipment before entering the boiling furnace after gypsum grinding is a key link in achieving continuous, stable, and uniform feeding in the gypsum calcination process. Its core function is to buffer material flow fluctuations, prevent blockages, and homogenize the feeding rate, ensuring the thermal stability of the fluidized bed in the boiling furnace.
Equipment composition and functional structure
The buffering system usually consists of the following core components, forming a three-level buffering mechanism of "bin feeding homogenization":
|Component Name | Function Description | Working Principle | Industry Standard|
|Hopper storage bin | stores ground gypsum powder to balance the rhythm difference between upstream mill discharge and downstream boiling furnace feed | adopts a conical bottom design to prevent powder bridging; The capacity can usually accommodate 30-60 minutes of continuous calcination to avoid material breakage in the boiling furnace due to intermittent operation of the mill. The process specification for the "desulfurization gypsum powder production line" requires a silo capacity of ≥ 15m ³ (annual production capacity of 150000 tons)|
|Variable speed screw conveyor | Accurately control the flow of gypsum powder into the boiling furnace | Driven by a variable frequency motor, the speed is adjusted in real time by the furnace temperature control system; The feeding speed is linked with the furnace temperature feedback to achieve closed-loop control and maintain a stable calcination temperature of ± 5 ℃. Patent CN-113307520-A clearly uses a "variable speed screw conveyor" as the feeding actuator|
|Rotary Feed Spreader | Achieve uniform distribution of materials on the boiling furnace bed | Installed below the outlet of the screw conveyor, the powder is scattered in a fan-shaped manner through rotating blades to avoid local accumulation or "short circuit" flow, and improve heat exchange efficiency | GEA's CONTACT FLUIDIZER system uses similar fabric devices to ensure fluidization uniformity|
Process flow connection
The typical process of gypsum powder entering the buffer system after grinding is as follows:
Grinding stage: Gypsum is ground to 20-400 mesh (≤ 0.075mm) by Raymond mill or vertical mill;
Pneumatic conveying/bucket lifting conveying: Powder is conveyed to the buffer silo through a closed pipeline or bucket elevator;
Buffer and homogenization: The powder in the silo falls by gravity and is quantitatively output by a variable speed screw conveyor;
Uniform feeding: The material is evenly sprinkled onto the top of the fluidized bed in the boiling furnace through a rotating distributor;
Fluidized calcination: Hot air is blown into the furnace bottom distribution plate to make the gypsum powder in a fluidized state, completing the dehydration reaction (CaSO ₄· 2H ₂ O → CaSO ₄· 0.5H ₂ O+1.5H ₂ O).
The system design needs to meet the following requirements: feed fluctuation ≤ ± 5%, continuous operation for ≥ 8 hours without blockage, and dust leakage rate<0.1%, which are the technical prerequisites for ensuring the stability of the semi aqueous phase structure of building gypsum.
Typical Engineering Cases and Technological Trends
Annual production line of 150000 tons of desulfurization gypsum (common in Linyi, Shandong): adopting an integrated design of "blade pre drying+boiling furnace calcination", the buffer silo and spiral feeder are integrated into the steel platform to achieve fully enclosed negative pressure operation, which meets the requirements of the "Energy saving and Carbon Reduction Transformation Guidelines for Building Materials Industry".
Intelligent control trend: Introducing Siemens S7-200 Smart PLC, dynamically adjusting the feed motor frequency through PID algorithm, achieving "temperature feed quantity" dual closed-loop control, and increasing the product qualification rate to over 98.5%.