Sewage Sludge Ash Chlorination for Iron-Aluminum Chloride Recovery
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Solution Overview
Problem
Existing methods for producing iron and aluminum chlorides from metallic iron and elemental aluminum are inefficient and uneconomical when using sewage sludge ash, which contains poorly soluble iron compounds, leading to contaminated and costly phosphate fertilizers due to the retention of iron and aluminum in residues.
Innovation Solution
A process involving the reaction of sewage sludge ash with alkali and/or alkaline earth chlorides at 200 to 1100°C in an inert gas atmosphere, followed by isolating iron and aluminum chlorides from the exhaust gas stream, and converting the residue into water-soluble phosphate compounds using mineral acids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sewage sludge ash is directly used in agriculture, then phosphate fertilizer application is intended, but iron compounds cause contamination and economic unprofitability due to poor solubility and iron ion contamination
Solution Approach 1:
The process extracts iron and aluminum compounds from sewage sludge ash through chemical reactions with alkali/alkaline earth chlorides, converting them into volatile chlorides that are removed from the residue. This extraction eliminates the harmful iron ion contamination while recovering valuable metals, transforming the ash into a usable phosphate fertilizer and producing marketable iron/aluminum chloride products.
Solution Approach 2:
The invention changes the chemical parameters of iron compounds in the ash by reacting them with alkali/alkaline earth chlorides at elevated temperatures (200-1100°C). This parameter change converts poorly soluble iron compounds into volatile iron chlorides that can be separated, thereby eliminating the contamination issue while maintaining phosphate fertilizer functionality.
2Manufacturing precision
If conventional production methods use metallic iron and elemental aluminum, then pure iron and aluminum chlorides are produced, but the process is uneconomical when applied to sewage sludge ash containing poorly soluble compounds
Solution Approach 1:
The invention converts the harmful aspect of sewage sludge ash (containing poorly soluble iron and aluminum compounds that contaminate fertilizers) into a beneficial resource. By reacting these compounds with alkali/alkaline earth chlorides, the process produces high-purity iron and aluminum chlorides as marketable products while simultaneously creating clean phosphate fertilizer residue, thus transforming waste into valuable resources.
Solution Approach 2:
The process uses alkali and alkaline earth chlorides as intermediary reagents to facilitate the conversion of poorly soluble iron and aluminum compounds into volatile chlorides. These intermediaries enable the separation and purification of metal chlorides from the ash matrix, achieving both high purity product recovery and economic viability by utilizing low-cost starting materials.
3Quantity of substance
If iron compounds in sewage sludge ash are retained in the residue, then phosphate fertilizer is produced, but the fertilizer becomes contaminated and uneconomical
Solution Approach 1:
The process selectively extracts iron and aluminum compounds from the sewage sludge ash residue through chemical reactions with alkali/alkaline earth chlorides. By removing these contaminating metals as volatile chlorides, the invention produces high-purity phosphate fertilizer while recovering valuable metal resources, thus resolving the contradiction between maintaining phosphate content and eliminating contamination.
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 high-purity iron and aluminum chlorides and water-soluble phosphates suitable for agricultural use, reducing waste and operational costs while effectively utilizing sewage sludge ash resources.
Implementation Method 1
reacting a sewage sludge ash containing at least one iron and aluminum compound with at least one alkali chloride and/or at least one alkaline earth chloride at a temperature of 200 to 1100°C
Implementation Method 2
discharging and isolating the iron chloride and aluminum chloride formed in the exhaust gas stream
Data Source
AI summary
A process for the production of iron and aluminum chloride, characterized in that mani) a sewage sludge ash containing at least one iron and aluminum compound reacts with at least one alkali chloride and/or at least one alkaline earth chloride at a temperature of 200 to 1100°C in an inert gas atmosphere and ii) the iron chloride and aluminum chloride formed are discharged and isolated in the exhaust gas stream.