High Carbon Fly Ash Thermal Gasification for Cementitious Materials
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Solution Overview
Problem
High carbon coal fly ash, contaminated with toxic elements, is unusable in concrete due to excessive carbon content, leading to environmental hazards and increased disposal costs, as it interferes with air entrainment and exceeds regulatory limits.
Innovation Solution
A thermal process converts the high carbon coal fly ash into synthesis gas to generate steam for electricity and produces cementitious materials by adding oxides, allowing for the production of hydraulically active cement with enhanced compressive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If activated carbon is used to absorb SOx and NOx from flue gas, then harmful emissions are reduced, but the carbon content of recovered CFA increases beyond acceptable limits
Solution Approach 1:
The patent converts the harmful effect of carbon contamination in CFA into a beneficial resource by gasifying the carbon to produce syngas for electricity generation. The thermal reactor gasifies the carbon at high temperatures, transforming it from a contaminant that renders CFA unusable into a valuable fuel source, while the resulting ash meets cementitious material specifications.
Solution Approach 2:
The patent changes the physical and chemical parameters of the CFA through thermal processing. By controlling temperature, oxygen partial pressure, and residence time in the thermal reactor, the carbon content is reduced from above 6% to below 6%, transforming the material from unusable to usable for cement production.
2Reliability
If high carbon CFA is disposed of in landfills or wet impoundments, then regulatory compliance is achieved, but environmental hazards increase and disposal costs rise
Solution Approach 1:
Instead of discarding high carbon CFA in landfills or impoundments, the patent recovers value from it by processing it in a thermal reactor. The carbon is gasified to produce electricity, and the resulting ash is recovered as a usable cementitious material, eliminating the need for harmful disposal methods while maintaining regulatory compliance.
Solution Approach 2:
The high carbon CFA serves its own remediation by providing the carbon necessary to fuel the thermal reactor. The material essentially pays for its own processing by generating the syngas needed for electricity production, while simultaneously being converted from a hazardous waste into a valuable resource.
3Ease of operation
If carbon content in CFA exceeds 6%, then air entrainment in concrete is interfered with, but the CFA cannot be used as supplemental cementitious material
Solution Approach 1:
The patent converts the harmful carbon content that interferes with air entrainment into a beneficial fuel source. By gasifying the carbon in the thermal reactor, the process eliminates the air entrainment interference while capturing the carbon's energy value as syngas for electricity generation, resulting in ash suitable for cement production.
Solution Approach 2:
The thermal processing fundamentally changes the carbon content parameter of the CFA from above 6% to below 6%, transforming it from an unusable material that interferes with concrete properties into a usable supplemental cementitious material that meets all specifications for concrete applications.
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 recycles high carbon fly ash into usable cementitious materials, reducing environmental hazards, lowering disposal costs, and generating additional energy, while enhancing concrete strength and reducing the need for limestone and clay in cement production.
Implementation Method 1
Gasification is a process wherein organic carbonaceous (mainly organic) materials are dissociated at high temperatures in an oxygen-starved environment to form a gas known as synthesis gas, or syngas, or producer gas.
Implementation Method 2
The synthesis gas includes mainly carbon dioxide, carbon monoxide, hydrogen, methane and water vapor, as well as trace amounts of sulfur and other oxides.
Implementation Method 3
The present invention uses thermal treatment to remove carbon from high carbon coal fly ash.
Data Source
AI summary
A method is provided of thermally processing carbonaceous ash and ancillary carbonaceous material to produce a carbon-free inert, pozzolanic, or cementitious material and synthesis gas. The carbonaceous ash and ancillary fuels are fed into a thermal reactor along with oxides provided in the ash or in additives including limestone or glass. Carbon in the ancillary fuel and coal fly ash is converted to synthesis gas that is combusted to generate process steam and electricity. Remaining ash exits the thermal reactor chamber for processing at high temperature in a kiln gasifier to react the remaining fixed carbon and produce carbon-free partially-fused nodules or clinker that are cooled and ground to a desired fineness for cementitious or aggregate material in concrete. Carbonaceous ash, especially high carbon coal fly ash and other carbonaceous waste, are converted to energy and non-toxic, carbon-free aggregate or cementitious material used as architectural fill or in concrete mixes.