Stucco Cooling and Healing with Countercurrent Humid Air
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Solution Overview
Problem
Existing methods for cooling and stabilizing calcined gypsum stucco (beta-calcium sulfate hemihydrate) are inefficient, leading to quality degradation due to aging and temperature issues, which affect pouring consistency, hydration rate, and mechanical properties.
Innovation Solution
A process and apparatus using a countercurrent flow of humid air and water to cool and heal stucco particles within a vessel, where the stucco is uniformly distributed by a rotating spreader and contacted with a gas stream containing air and water to encapsulate and cool the particles below the calcination temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If stucco is stored in containers without proper cooling, then storage is simplified, but the stucco ages over time and quality deteriorates
Solution Approach 1:
The patent applies preliminary cooling action by cooling the stucco immediately after calcination before it enters storage. The cooling system reduces the temperature from calcination levels (140-170°C) to below 121°C, preventing subsequent aging during storage. This preliminary treatment ensures quality stability without complicating the storage operation itself.
2Reliability
If stucco is cooled quickly after calcination, then quality stability is improved, but additional cooling equipment and process complexity are required
Solution Approach 1:
The patent employs pneumatic cooling using a stream of air to cool the stucco particles after calcination. The air stream flows through the calcined stucco in a counter-current direction, efficiently removing heat without requiring complex mechanical cooling systems. This hydraulic/pneumatic approach simplifies the cooling equipment while achieving the required temperature reduction to below 121°C.
3Manufacturing precision
If mechanical energy from tube mill grinding is applied to stucco, then particle size is reduced, but additional heat is generated and temperature requirements for bagging cannot be met
Solution Approach 1:
The patent implements continuous cooling action immediately following the grinding operation. The air stream cooling system operates continuously as stucco moves from the tube mill to storage or bagging, constantly removing the heat generated by mechanical grinding. This continuous cooling maintains particle size reduction benefits while keeping temperature below the 121°C threshold for proper bagging.
4Productivity
If hot calcined stucco is stored, then storage capacity is maximized, but pouring consistency, hydration rate, and set time are adversely affected
Solution Approach 1:
The patent applies preliminary cooling treatment to reduce stucco temperature below 121°C before storage or bagging. This preliminary action prevents the adverse effects of high temperature storage on pouring consistency, hydration rate, and set time. The cooling occurs upfront, allowing full storage capacity utilization without compromising product quality attributes.
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 process effectively stabilizes stucco by sealing crystal cracks and reducing temperature to below 121°C, preventing aging and improving storage and manufacturing performance, while reducing water and additive requirements.
Implementation Method 1
contacting the stucco particles with a rotating spreader in the upper portion of the vessel to homogenize or substantially uniformly distribute the stucco particles within the vessel and passing the stucco particles downwardly from the rotating spreader
Implementation Method 2
feeding gas comprising air and water into the vessel from a side in a lower portion of the vessel and/or bottom of the vessel with positive or negative pressure, wherein the air is about 0° to 50° C. and the water is at 5 to 80° C. before combining with the air
Implementation Method 3
the gas in the vessel cools and substantially fully encapsulates the stucco particles within the vessel for a time of 5 seconds to 2 minutes
Implementation Method 4
During healing, the invention employs humid air to coat the particle with moisture which repairs cracks in crystals of beta-calcium sulfate hemihydrate by sealing the cracks formed during the prior calcination of gypsum to form the stucco
Data Source
AI summary
The present invention relates to a process and an apparatus to cool and heal calcined stucco particles. The process includes feeding stucco particles into an upper portion of a vessel, and feeding a gas comprising air and water into the lower portion of a vessel, wherein the gas cools and substantially fully encapsulates the stucco particles. The apparatus includes a vessel with a rotating spreader for homogenizing the stucco particles, for use in the process described.