Rotary Kiln Calcined Clay Process With Oxygen-Based Color Control
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Solution Overview
Problem
Existing calcined clay production processes result in undesired color changes during calcination, affecting its suitability for cement and concrete applications, and contribute to high CO2 emissions and production costs.
Innovation Solution
A manufacturing process involving mixing raw clays with a reducing agent, controlling particle size and moisture, calcining at specific temperatures and oxygen concentrations, and cooling under low oxygen conditions to maintain color control and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If calcined clay is produced using traditional high-temperature limestone decarbonation processes, then cement clinker is obtained, but CO2 emissions and production costs increase significantly
Solution Approach 1:
The patent changes the chemical composition parameters of the calcined clay by controlling iron oxide content (0.5-5% Fe2O3) and applying specific calcination temperatures (900-1000°C) with controlled atmosphere (1-5% oxygen). These parameter changes enable the clay to develop pozzolanic properties that allow it to replace traditional clinker, thereby reducing CO2 emissions while maintaining cement production efficiency
Solution Approach 2:
The patent uses calcined clay as an intermediary material that bridges the gap between traditional cement production and low-carbon alternatives. By treating clay with specific reducing agents and controlling the calcination atmosphere, the clay acquires pozzolanic properties that enable it to function as a clinker substitute, thus mediating the transition to lower-carbon cement formulations
2Manufacturing precision
If reducing agents are added to control clay color during calcination, then desired grayish color is achieved, but process complexity increases
Solution Approach 1:
The patent controls clay color by precisely adjusting process parameters: adding reducing agents in specific quantities (1-10% by weight relative to clay), maintaining oxygen concentration between 1-5% during calcination, and controlling temperature at 900-1000°C. These parameter changes enable consistent grayish color production without requiring complex additional equipment
Solution Approach 2:
The patent creates a controlled reducing atmosphere during calcination by limiting oxygen concentration to 1-5% and introducing reducing agents. This controlled inert-like environment prevents oxidation of iron compounds, thereby controlling the clay color to the desired grayish shade while keeping the process relatively simple
3Object-affected harmful factors
If calcined clay is used as a clinker replacement material, then CO2 emissions are reduced, but the availability and feasibility of suitable materials are limited
Solution Approach 1:
The patent transforms ordinary clay into a suitable clinker replacement by changing its chemical and physical parameters through controlled calcination. By adjusting iron oxide content to 0.5-5%, controlling particle size distribution, and applying specific thermal treatment conditions, the clay acquires the necessary pozzolanic properties and physical characteristics to be a viable and widely available alternative to traditional clinker materials
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
Produces calcined clay with superior performance for cement and concrete, reducing CO2 emissions and production costs while achieving desired grayish color and maintaining performance comparable to traditional materials.
Implementation Method 1
dosing a reducing agent to the mixed raw clays... calcining the dried mixture from 600 to 900° C., maintaining an oxygen concentration between 1 and 5%
Implementation Method 2
heating the mixture in a flash dryer or flash calciner until the mixture has between 0% and 5% moisture
Implementation Method 3
calcining the dried mixture from 600 to 900° C.
Data Source
AI summary
A method for manufacturing calcined clays comprising extracting and mixing raw clays; dosing a reducing agent to the mixed raw clays and homogenizing the resulting mixture; reducing the particle size of the mixture to less than 10 mm; heating the mixture in a flash dryer or flash calciner until the mixture has between 0% and 5% moisture; calcining the dried mixture from 600 to 900° C., maintaining an oxygen concentration between 1 and 5%; and cooling the calcined clay from 900° C. to 120° C., and uses of such calcined clay resulting from the claimed method in cement and/or a cementitious material for preparing concrete.