Silicon Carbide Membrane Supports Using Fly Ash for Strength and Permeability
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Solution Overview
Problem
The disposal of activated coke fly ash, a hazardous waste containing high concentrations of SO2 and metal catalysts, poses environmental and economic challenges, and existing methods for preparing silicon carbide membrane supports using rice husk ash and straw ash result in uneven particle size distribution and environmental pollution.
Innovation Solution
A method utilizing activated coke fly ash as a pore-forming agent, combined with silicon carbide aggregate and sintering aids, to prepare silicon carbide membrane supports through mixing, extrusion, drying, and sintering, leveraging the ash's uniform particle size and sintering properties to achieve high mechanical strength and gas permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If activated coke fly ash is directly used to prepare ammonium sulfate or sulfuric acid, then the disposal cost is reduced, but the product purity becomes low
Solution Approach 1:
The patent converts the harmful activated coke fly ash containing high concentrations of SO2 and metal catalysts into a valuable pore-forming agent for silicon carbide membrane supports. The fly ash is classified as hazardous waste but is transformed into a functional material that provides both porosity and sintering aid properties, simultaneously solving the disposal problem and creating economic value.
Solution Approach 2:
The patent introduces a high-temperature silicon carbide membrane support as an intermediary device between the activated coke fly ash and the downstream chemical processes. The membrane support filters and purifies the flue gas, enabling the production of high-purity ammonium sulfate or sulfuric acid while disposing of the fly ash beneficially.
2Loss of substance
If rice husk ash and straw ash are used as pore-forming agents, then the cost is reduced, but the particle size distribution becomes uneven and environmental pollution occurs
Solution Approach 1:
The patent changes the key parameter of particle size distribution by selecting activated coke fly ash, which naturally possesses a uniform particle size distribution due to its formation process in fluidized bed reactors. This eliminates the need for additional size classification processes and ensures uniform pore structures in the membrane support.
Solution Approach 2:
The patent transforms the hazardous waste activated coke fly ash into a beneficial pore-forming agent. The fly ash's uniform particle size and porous structure, resulting from its generation process, are leveraged to create high-quality membrane supports, converting an environmental liability into a technical advantage.
3Productivity
If a large number of pore-forming agents are used to achieve high porosity, then the gas permeability is improved, but the mechanical strength deteriorates
Solution Approach 1:
The patent creates a composite material system where activated coke fly ash particles are embedded in a silicon carbide matrix. The fly ash particles serve as pore-forming agents that create a interconnected porous structure for high gas permeability, while the silicon carbide binder provides mechanical strength and structural integrity to the membrane support.
Solution Approach 2:
The patent utilizes the inherent porous structure of activated coke fly ash to create a porous membrane support. The uniform particle size distribution of the fly ash ensures consistent pore formation throughout the matrix, achieving high porosity and gas permeability while maintaining structural integrity through the silicon carbide binding phase.
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 effectively reduces costs, enhances mechanical strength and gas permeability of silicon carbide membrane supports, making them suitable for high-temperature flue gas purification with improved product purity and reduced environmental impact.
Implementation Method 1
The activated coke fly ash, classified as hazardous waste according to national hazardous waste management regulations, has a complicated disposal procedure and high costs. Through energy spectrum analysis, the main elements in the activated coke fly ash are C, N, O, S, Cu, and Zr, which is suitable as a pore-forming agent in the preparation of a silicon carbide membrane support.
Implementation Method 2
The activated coke fly ash, classified as hazardous waste according to national hazardous waste management regulations, has a complicated disposal procedure and high costs. Through energy spectrum analysis, the main elements in the activated coke fly ash are C, N, O, S, Cu, and Zr, which is suitable as a pore-forming agent in the preparation of a silicon carbide membrane support. At the same time, the metal oxides in the activated coke fly ash may serve as sintering aids for the silicon carbide membrane support.
Data Source
AI summary
Embodiments of the present disclosure provide a method for preparing silicon carbide membrane supports using activated coke fly ash. Using activated coke fly ash as a pore-forming agent, micro-sized silicon carbide powder as the primary aggregate, nano-zirconia, alumina, and/or magnesia as sintering aids, and polyvinyl alcohol aqueous solution as a binder. The components are uniformly mixed to obtain a premixed material. The premixed material is extruded via mechanical extrusion to form support green bodies, which are then dried at a constant temperature in a drying oven. Finally, the dried green bodies undergo programmed sintering in a muffle furnace to produce the silicon carbide membrane supports.