Phosphorus Recovery from Sewage Sludge Ash via Rapid Acid Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for recovering phosphorus from sewage sludge ash often result in the undesirable extraction of metals along with phosphorus, making it challenging to achieve a favorable ratio between phosphorus release and metal release, especially due to longer extraction times.
Innovation Solution
The method involves reacting sewage sludge ash with phosphoric acid for a shorter duration than conventional processes, typically less than 2 minutes, to quickly release phosphorus while minimizing the release of metals like chromium, copper, iron, nickel, and zinc, which are released more slowly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional extraction methods are used with longer extraction times (3-8 hours), then complete phosphorus release is achieved, but metal release increases significantly
Solution Approach 1:
The patent applies the 'Skipping (Rushing through)' principle by drastically reducing the extraction time from conventional 3-8 hours to just 1-2 minutes. This rapid extraction allows phosphorus to be released quickly into the phosphoric acid solution before metals have time to dissolve significantly, thereby achieving high phosphorus recovery while minimizing metal contamination. The key insight is that phosphorus extraction kinetics are much faster than metal extraction kinetics, allowing selective extraction through time control.
2Productivity
If extraction time is extended to ensure complete phosphorus release, then phosphorus recovery efficiency improves, but the ratio of phosphorus to metal release deteriorates
Solution Approach 1:
The patent applies the 'Parameter changes' principle by fundamentally changing the extraction time parameter from hours to minutes. This parameter change exploits the difference in extraction kinetics between phosphorus and metals. By setting the extraction time to 1-2 minutes, the process achieves both high phosphorus recovery efficiency (90% or more) and favorable phosphorus-to-metal release ratio, as metals require longer contact time to dissolve appreciably.
3Object-generated harmful factors
If short extraction times are used to minimize metal release, then metal contamination is reduced, but phosphorus extraction completeness may be compromised
Solution Approach 1:
The patent applies the 'Preliminary action' principle by using phosphoric acid pre-treated with sewage sludge ash to create an optimized extraction solution. This preliminary conditioning of the phosphoric acid enhances its phosphorus extraction capability while maintaining selectivity. The pre-treated phosphoric acid contains dissolved phosphorus from previous extraction cycles, creating a synergistic effect that accelerates further phosphorus extraction during the brief 1-2 minute contact time, ensuring complete extraction without requiring longer durations that would increase metal release.
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 approach allows for a high percentage of phosphorus extraction from sewage sludge ash while maintaining a low metal load in the enriched phosphoric acid, resulting in a high-quality product with reduced contamination.
Implementation Method 1
the combustion residue is brought into contact with an acidic, phosphorus-containing extraction solution, causing phosphorus to be released from the ash and accumulate in the extraction solution
Data Source
Figure 1a~1b
Figure 1c~2
Figure 3
AI summary
The present invention relates to a process and a device for recovering phosphorus from phosphorus-containing sludge ash. Sludge ash is reacted with phosphoric acid of a first concentration. First solids are then separated and phosphoric acid of a second concentration remains. The second concentration is higher than the first concentration. The reaction time of the reaction of the sludge ash with the phosphoric acid is less than 2 minutes.