Clay-Coated Boiler Sand to Prevent Bed Sintering
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Solution Overview
Problem
The reaction between silica in natural sand and alkalis in biofuel ash causes sintering of the sand, leading to weakened or stopped bed material floating in power plant boilers, necessitating frequent replacement.
Innovation Solution
Using discarded foundry sand with a clay-based binder film on its surface to prevent or reduce the reaction between silica and alkalis, thereby inhibiting sand sintering and extending the sand's working life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural sand is used as bed material, then the sand layer forms properly for fuel combustion, but the silica in natural sand reacts with alkalis in biofuel ash causing sintering and reducing bed material floating capability
Solution Approach 1:
A clay-based binder coating is applied to the surface of sand grains to act as an intermediary barrier. This coating prevents direct contact and chemical reaction between the silica in natural sand and alkalis in biofuel ash, thereby eliminating the sintering problem while maintaining the sand's structural integrity and floating capability throughout its service life.
Solution Approach 2:
The bed material is transformed from pure natural sand to a composite structure consisting of sand grains coated with clay-based binder. This composite material combines the beneficial properties of natural sand (proper sand layer formation) with the protective properties of clay coating (resistance to alkali-silica reaction), resolving the contradiction between initial reliability and long-term durability.
2Duration of action of stationary object
If furnace slag is used as bed material to reduce alkali reactions, then sintering is reduced and replacement frequency decreases, but crystallization heat accumulates causing intense temperature rises that may sinter the entire bed
Solution Approach 1:
The clay-based binder coating serves as a thermal buffer and heat distribution medium on the sand grain surfaces. It moderates the release of crystallization heat from furnace slag components, preventing sudden intense temperature spikes while maintaining the low-alkali benefits of slag-based materials, thus extending service life without compromising temperature stability.
3Duration of action of stationary object
If discarded foundry sand with clay-based binder is used, then the clay coating prevents silica-alkali reactions extending working life, but the fine fraction separation process is required
Solution Approach 1:
The invention recovers and reuses discarded foundry sand that would otherwise be waste material. The clay-based binder that was originally used in foundry applications is retained and repurposed as a protective coating for boiler bed material, transforming a waste stream into a valuable resource with extended service life while requiring only fine fraction separation for quality control.
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 clay-based binder film prevents or reduces sand sintering, allowing the sand to be used longer without replacement and reducing the risk of bed material sintering due to crystallization heat.
Implementation Method 1
there is, as shown in FIG. 2, on the surface of the grain of sand 2 a clay-based binder film 3 by means of which a mould made of sand may be hardened. It has been established that the clay-based binder film 3 on the surface of the grain of sand 2 prevents the reaction between the silica in the grain of sand and the compounds of alkalis
Implementation Method 2
furnace slag that is quickly pre-cooled with water is in amorphous form and includes incrystallized energy which is released at approximately 860° C. The crystallization heat temporarily raises the bed temperature intensely, exceeding one thousand degrees
Data Source
AI summary
Power plant boiler sand comprising a clay-based binder film (3) on the surface of a grain of sand (2). In addition, a method and apparatus for producing power plant boiler sand.