Aluminum Separation in Calcium Silicate Calcination
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Solution Overview
Problem
The production of calcium silicate from mineral feedstocks containing calcium, silicon, and aluminum is hindered by the formation of undesirable calcium-aluminum-silicon mineral phases, which reduces the yield and quality of dicalcium silicate, especially at high temperatures used in existing processes, and requires inefficient energy consumption and gas cleaning.
Innovation Solution
A method involving calcination of comminuted starting materials with alkali metal carbonates in a CO2-containing gas atmosphere at lower temperatures (850-1050°C) to convert aluminum compounds into water-soluble forms, followed by aqueous elution to separate aluminum, allowing for the use of aluminum-containing raw materials and residues while maintaining calcium silicate quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high sintering temperatures (1250-1400°C) are used to separate aluminum from calcium silicate, then aluminum separation efficiency is improved, but energy consumption increases and calcium silicate yield decreases
Solution Approach 1:
The patent changes the temperature parameter from conventional high sintering temperatures (1250-1400°C) to a lower temperature range (850-1050°C). This parameter change enables aluminum separation through a different mechanism (formation of water-soluble aluminum compounds that can be leached) while significantly reducing energy consumption and preventing the formation of unwanted calcium-aluminum-silicon phases that occur at higher temperatures.
Solution Approach 2:
The patent utilizes phase transition by converting aluminum compounds into water-soluble forms (such as aluminum hydroxide or aluminum carbonate) at lower temperatures, which can then be separated from the calcium silicate matrix through aqueous leaching. This phase change approach replaces the need for high-temperature separation and enables efficient aluminum recovery without energy-intensive processes.
2Productivity
If high sintering temperatures (1250-1400°C) are used to separate aluminum, then aluminum separation is achieved, but the yield of dicalcium silicate decreases significantly
Solution Approach 1:
By changing the temperature parameter to the lower range of 850-1050°C, the patent prevents the formation of unwanted calcium-aluminum-silicon phases (such as katoite and hibshite) that would consume calcium and reduce dicalcium silicate yield. Simultaneously, this temperature range is sufficient to convert aluminum compounds into water-soluble forms for effective separation, thus achieving both aluminum recovery and high dicalcium silicate yield.
3Productivity
If high sintering temperatures are used, then aluminum separation is possible, but thermal and chemical stress on reactor materials increases considerably
Solution Approach 1:
The patent reduces the operating temperature from 1250-1400°C to 850-1050°C, which dramatically decreases the thermal stress on reactor materials. This temperature reduction also lowers the chemical reactivity and volatility of components, reducing chemical stress and the decomposition of reactor materials, thereby extending equipment lifespan and reducing maintenance requirements.
4Adaptability or versatility
If aluminum-containing raw materials are used, then the raw material base is expanded, but formation of unwanted calcium-aluminum-silicon phases increases
Solution Approach 1:
The patent employs a two-stage approach: first, low-temperature treatment (850-1050°C) converts aluminum compounds into water-soluble forms while preventing the formation of unwanted calcium-aluminum-silicon phases; second, aqueous leaching removes the converted aluminum compounds. This enables the use of aluminum-containing raw materials such as coal ash and metallurgical slag without compromising calcium silicate quality, thus expanding the raw material base while maintaining product quality.
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 process efficiently produces high-quality calcium silicate with adjustable α'- and β-C2S yields, enables the separation of aluminum, and reduces energy consumption and thermal load, making it suitable for hydrothermal cement production and material recycling.
Implementation Method 1
calcination of comminuted starting materials with alkali metal carbonates in a CO2-containing gas atmosphere at lower temperatures (850-1050°C) to convert aluminum compounds into water-soluble forms
Implementation Method 2
followed by aqueous elution to separate aluminum
Data Source
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AI summary
The invention relates to a method for separating aluminum during calcium silicate production from mineral feed materials (3) comprising mineral raw materials and residual materials, comprising the comminution and mixing (1) of the feed materials with alkali carbonates (2) to form a material mixture (4), calcination (5) of the material mixture with a CO2 partial pressure between 0.05 and 0.2 MPa at 850 to 1100°C, wherein CO2 (6) is released and a calcined product (7) consisting of water-insoluble calcium silicates and water-soluble aluminum compounds is formed, a first elution (8) of the calcined product with water (9) or a liquid aqueous alkali hydroxide and/or alkali carbonate solution in a temperature range of between 0 and 100°C, wherein aluminum in the form of alkali aluminates (alkali Al (OH)4) is dissolved, solid/liquid separation of the dissolved alkali aluminates into a solution (10) rich in alkali Al (OH)4 and an alkali-containing solid (11a) rich in calcium silicate, and precipitation (12) and separation of aluminum hydroxide Al (OH)3 (13) from the solution rich in alkali Al (OH)4 by adding seed crystals and/or by adding CO2 or a gas containing CO2, wherein alkali hydroxides and/or alkali carbonates (14) are formed and remain in the solution.