Red Mud Wet Grinding CO2 Sequestration Alkali Activation
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Solution Overview
Problem
Current methods for utilizing red mud and carbide slag are inefficient, leading to low utilization rates and environmental pollution, with a need for effective carbon sequestration and compound alkali activation to address high alkalinity and energy consumption.
Innovation Solution
A method involving red mud-based wet grinding and carbon sequestration, where CO2 is introduced during wet grinding to reduce red mud alkalinity and react with dissolved ions to form stable carbonates, combined with wet-ground carbide slag for compound activation of slag powder, increasing its strength and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If red mud is stockpiled in open air for waste management, then storage is simple and low cost, but environmental pollution increases and resource utilization remains at only 4%
Solution Approach 1:
The patent converts the harmful high-alkalinity red mud waste into a beneficial alkali activation material by reacting it with CO2 during wet grinding. The harmful alkalinity (pH 11-13) is transformed into useful alkaline components that activate slag powder, while simultaneously sequestering CO2. This resolves the contradiction by turning the polluted waste into a valuable resource for producing high-strength construction materials.
Solution Approach 2:
The patent changes the chemical parameters of red mud through wet grinding with CO2 introduction, transforming it from a high-alkalinity waste product into a controlled-alkalinity activation material. The process modifies pH, particle size distribution, and chemical composition to create a material suitable for alkali activation, thereby converting waste into a functional building material that eliminates pollution while maintaining ease of handling.
2Reliability
If chemical reagents are added for system activation in red mud-slag geopolymer preparation, then activation effectiveness improves, but additional energy consumption increases and cost rises
Solution Approach 1:
The patent employs self-service activation where the wet-ground red mud itself provides the alkaline environment needed for geopolymer formation. The red mud, after CO2 treatment, generates sufficient alkalinity to activate the slag powder without requiring additional chemical reagents like NaOH or KOH. This eliminates the energy consumption and costs associated with producing and adding external activators, while maintaining reliable activation effectiveness.
Solution Approach 2:
The red mud serves multiple functions: it acts as both the alkaline activator and the source of binding materials for the geopolymer. The wet grinding process with CO2 introduces carbonate ions that modify the red mud's chemical composition, enabling it to simultaneously provide alkalinity for activation and contribute to the geopolymer matrix, thereby eliminating the need for separate activator chemicals and reducing overall energy consumption.
3Strength
If high temperature activation and calcination are used in geopolymer grouting material preparation, then material strength improves, but process complexity increases and energy consumption rises
Solution Approach 1:
The patent replaces thermal activation (high-temperature calcination) with mechanical activation through wet grinding. The wet grinding process with CO2 introduction achieves activation at ambient or low temperatures by mechanically breaking down the red mud structure and introducing carbonate ions, eliminating the need for high-temperature furnaces and complex thermal processing equipment while maintaining material strength.
Solution Approach 2:
The patent changes the activation mechanism from thermal to chemical-mechanical. Instead of using high temperature to activate the materials, the process uses wet grinding with controlled CO2 introduction to modify the chemical composition and physical structure of red mud, creating an activated state at low temperature. This simplifies the equipment requirements and reduces energy consumption while achieving the necessary material strength for geopolymer applications.
4Strength
If high pressure molding is applied in red mud-fly ash building block production, then product strength improves, but large-scale utilization fails due to complex molding and curing conditions
Solution Approach 1:
The patent replaces high-pressure mechanical molding with low-pressure or ambient-pressure molding enabled by the chemically activated slurry. The wet-ground red mud with introduced CO2 creates a highly reactive slurry that sets and hardens through chemical reaction rather than requiring high-pressure compaction. This eliminates complex high-pressure molding equipment and simplifies the curing process, enabling easy large-scale production while maintaining product strength.
Solution Approach 2:
The patent changes the setting mechanism from physical compression to chemical bonding. The wet grinding process with CO2 introduces carbonate ions that modify the slurry's chemical reactivity, enabling it to set and gain strength through chemical precipitation and polymerization at ambient pressure. This transformation from pressure-dependent to chemistry-dependent setting simplifies the molding operation and curing conditions, making the process suitable for large-scale utilization.
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
This method achieves permanent CO2 sequestration, increases the utilization rate of red mud and carbide slag, and produces an alkali activation material with high strength and stability, effectively controlling waste in an environmentally friendly manner.
Implementation Method 1
introducing CO2 at a flow rate of 0.1 to 0.25 L/min, and keeping a pressure of 0.2 to 0.5 MPa until a slurry pH reaches 7 to 7.5
Implementation Method 2
performing wet grinding on water, red mud, a crystalline control agent, and a grinding aid
Implementation Method 3
the red mud has the characteristics of high alkalinity, complex chemical composition, low permeability, high dispersity
Implementation Method 4
compound alkali activation on the slag powder in cooperation with wet-ground carbide slag and the red mud
Data Source
AI summary
The present invention discloses a method of preparing an alkali activation material by using red mud-based wet grinding and carbon sequestration and an application thereof. The preparation method includes: (1) adding water, red mud, a crystalline control agent, and a grinding aid into a wet grinding carbon sequestration apparatus to perform wet grinding, and simultaneously introducing CO2 until a slurry pH reaches 7 to 7.5; and removing wet grinding balls by a sieve to obtain a slurry A; (2) adding carbide slag, water and a water reducer to a wet planetary ball grinder tank for wet grinding, and removing wet grinding balls by a sieve to obtain a slurry B; (3) taking 50 to 80 parts of the slurry A and 20 to 50 parts of the slurry B and mixing them to obtain an alkali activation material.