Fly Ash Reforming Process for Cement Admixture
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Solution Overview
Problem
Existing methods face challenges in efficiently reducing unburned carbon in fly ash to a suitable level for use as a cement or concrete admixture, as high temperatures required for carbon removal lead to lump formation and heat balance issues, making it difficult to maintain the necessary temperature range for effective processing.
Innovation Solution
A process involving heating fly ash to 780-1000°C, followed by classification into coarse and fine powders, milling the coarse powder, and recovering the fine powder to achieve a reformed fly ash with reduced unburned carbon, using a combination of heating, classifying, milling, and dust-collecting apparatuses to ensure efficient processing and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fly ash is heated at high temperature (not lower than 700°C) to remove unburned carbon quickly, then the unburned carbon content decreases significantly in short time, but the fly ash grains melt-adhere together and form lumps
Solution Approach 1:
The patent segments the heating process into multiple stages with different temperature zones. The fly ash is heated in a first heating zone at a lower temperature to prevent lump formation, then in a second heating zone at a higher temperature to remove carbon efficiently. This segmentation allows the process to achieve both quick carbon removal and prevent lumping by separating the heating functions spatially.
2Productivity
If the heating temperature is elevated above 780°C to remove carbon quickly, then the carbon removal efficiency increases, but the fly ash grains tend to melt-adhere together and turn into lumps
Solution Approach 1:
The heating furnace is divided into multiple heating zones with different temperature characteristics. The first heating zone operates at a lower temperature range that prevents lump formation, while the second heating zone operates at a higher temperature optimized for carbon removal. This spatial segmentation of temperature zones allows the system to achieve high carbon removal efficiency without requiring precise control of a single high temperature, thus resolving the contradiction between productivity and manufacturing precision.
3Shape
If the temperature range is limited to 700-780°C to prevent lump formation, then lump formation is suppressed, but it becomes very difficult to maintain the temperature in such a limited range due to heat balance loss and oxygen supply issues
Solution Approach 1:
By dividing the heating process into multiple zones with different temperature ranges, the system eliminates the need to maintain a single narrow temperature range. Each zone can operate independently at its optimal temperature, making temperature control much easier. The first zone maintains lower temperature to prevent lumping, while the second zone operates at higher temperature for efficient carbon removal, thus resolving the contradiction between lump suppression and ease of operation.
Solution Approach 2:
The patent introduces an intermediary heating zone that acts as a transition between the low-temperature first heating zone and the high-temperature second heating zone. This intermediary zone helps stabilize the temperature profile and facilitates smooth heat and mass transfer between zones, making temperature maintenance easier while still preventing lump formation in the first zone and enabling efficient carbon removal in the second zone.
4Adaptability or versatility
If diverse fly ashes with varying unburned carbon content are heated, then the process must be highly adaptable, but it becomes very difficult to set the temperature to lie in a very limited range of 700 to 780°C
Solution Approach 1:
The multi-zone heating system with different temperature ranges provides inherent adaptability to process diverse fly ashes. Each zone can be independently adjusted to optimize performance for different feedstock characteristics. The first zone prevents lumping across all feed types, while the second zone efficiently removes carbon regardless of initial content variations, thus resolving the contradiction between adaptability and temperature control precision.
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 allows for the continuous and efficient reduction of unburned carbon in fly ash, enabling its use as a suitable admixture by maintaining stability and preventing lump formation, even with varying carbon content, and ensures the reformed fly ash can be effectively used in cement or concrete applications.
Implementation Method 1
the heating step that heats a raw fly ash powder containing the unburned carbon at a temperature of 780 to 1000° C. to decrease the amount of the unburned carbon contained in the raw fly ash powder
Implementation Method 2
the classifying step that introduces the heat-treated fly ash containing the unburned carbon in decreased amounts obtained through the heating step into a classifying apparatus in the state of being heated at a high temperature so as to separate the fly ash into a coarse powder and a fine powder
Implementation Method 3
the fine powder recovering step that recovers the fine powder of the heat-treated fly ash obtained through the classifying step by using a dust-collecting apparatus
Data Source
AI summary
A process for reforming the fly ash, including the heating step that heats a raw fly ash powder containing the unburned carbon at a temperature of 780 to 1000° C. to decrease the amount of the unburned carbon contained in the raw fly ash powder; the classifying step that introduces the heat-treated fly ash containing the unburned carbon in decreased amounts obtained through the heating step into a classifying apparatus in the state of being heated at a high temperature so as to separate the fly ash into a coarse powder and a fine powder; the fine powder recovering step that recovers the fine powder of the heat-treated fly ash obtained through the classifying step by using a dust-collecting apparatus; and the milling step that mills the coarse powder of the heat-treated fly ash obtained through the classifying step until a 45 μm sieve residue becomes not more than 34% by mass, and then recovers the milled powder.