Fluidized-Bed Calcining Apparatus for Wasted Gypsum
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Solution Overview
Problem
Fluidized-bed calcining apparatuses face challenges in calcining gypsum granular solid from crushed wasted gypsum boards due to wide particle size distribution caused by starch and binders, leading to instability and inefficient production of hemihydrate or anhydrous type III gypsum, with existing methods either scattering small particles or leaving large particles in the apparatus.
Innovation Solution
A method and apparatus where gypsum granular solid is fed and discharged without a barrier plate, using a controller to maintain the amount within a predetermined range, and a cyclone to collect and return large particles, ensuring stable operation and reducing dihydrate gypsum content to less than 5% by adjusting airflow and particle movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a barrier plate is used to control the amount of powder in the fluidized-bed, then large size particles can pass over the barrier plate, but small size particles are quickly scattered toward the exhaust line and discharged in large amounts (40-60 mass %)
Solution Approach 1:
The invention removes the barrier plate from the fluidized-bed calcining apparatus. By taking out the barrier plate that was causing the scattering of small particles toward the exhaust line, the system eliminates the harmful effect while maintaining the ability to discharge large particles through controlled airflow. This extraction of the problematic component resolves the contradiction between discharging large particles and preventing small particle loss.
2Speed
If air velocity is increased to discharge large particles, then large size particles can pass over the barrier plate, but small size particles are scattered and discharged in large amounts
Solution Approach 1:
The invention removes the barrier plate that was causing small particles to scatter when air velocity was increased. Without the barrier plate, the increased air velocity can be used effectively to discharge large particles without the harmful scattering effect on small particles, thus resolving the contradiction between achieving sufficient air velocity for discharge and preventing small particle loss.
3Loss of substance
If air velocity is reduced to reduce scattering of small particles, then small particle loss is decreased, but particles with large diameters do not pass over the barrier and remain in the calcining apparatus
Solution Approach 1:
The invention removes the barrier plate that prevented large particles from being discharged when air velocity was reduced. Without the barrier plate, large particles can be discharged through the fluidized-bed outlet even at lower air velocities, while small particles are not scattered, thus resolving the contradiction between reducing small particle loss and maintaining large particle discharge.
4Reliability
If the amount of gypsum granular solid in the fluidized-bed is not controlled, then the operation of the fluidized-bed becomes unstable and eventually becomes inoperable, but controlling it requires precise feeding and discharging mechanisms
Solution Approach 1:
The invention implements a control system that monitors the amount of gypsum granular solid in the fluidized-bed and adjusts the feeding and discharging rates accordingly. This feedback mechanism maintains the amount within a predetermined range, ensuring stable operation without requiring overly complex manual control. The controller receives information about the current state and automatically adjusts parameters to maintain reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for efficient calcination of gypsum granular solid into hemihydrate and anhydrous type III gypsum, maintaining a steady-state operation of the calcining apparatus and reducing the amount of dihydrate gypsum to less than 5%, thereby improving the quality and stability of the calcination process.
Implementation Method 1
Fluidized-bed calcining apparatuses introduce hot air into the fluidized-bed from below and heat powder in the fluidized-bed by the hot air
Implementation Method 2
a cyclone to collect and return large particles
Implementation Method 3
Fluidized-bed calcining apparatuses introduce hot air into the fluidized-bed from below and heat powder in the fluidized-bed by the hot air. The granular solid moves from the inlet to the outlet of the fluidized-bed while flowing by the hot air
Data Source
AI summary
Gypsum granular solid obtained by crushing wasted gypsum boards is calcined and converted to hemihydrate and/or anhydrous type III gypsum. The gypsum granular solid is fed by a feeding device from a feed port into a fluidized-bed of a calcining apparatus. The gypsum granular solid after calcination is discharged by a discharging device from a discharge port of the fluidized-bed. The amount of the gypsum granular solid in the fluidized-bed is maintained within a predetermined range by controlling the feeding device and the discharging device. The generation of anhydrous type II gypsum is reduced, and the calcining apparatus can be operated stationarily.