Nutrient Recovery from Sewage Sludge via Thermal Gasification
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Solution Overview
Problem
Current methods for processing sewage sludge and animal manure fail to efficiently recover nutrients like nitrogen and phosphorus while minimizing environmental impact, as they often result in water contamination and loss of ammonia during incineration, and incomplete nutrient recovery in gasification processes.
Innovation Solution
A method combining dewatering, thermal gasification, and ammonia and phosphorus recovery from sewage sludge and animal manure, followed by fertilizer production with a tailored N/P ratio, utilizing fluidized bed gasification and scrubbing to achieve nearly complete nitrogen and phosphorus recovery and energy utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If incineration is used to process sewage sludge, then water evaporation and volume reduction are achieved, but ammonia is lost and nitrous oxides are formed requiring NOx removal equipment
Solution Approach 1:
The patent extracts ammonia from the gasification product gas through a dedicated ammonia stripping unit, separating it from the combustion gases before they are released or further processed. This prevents ammonia loss to the atmosphere and eliminates the need for NOx removal equipment while achieving volume reduction through gasification.
2Object-affected harmful factors
If incineration is used to process sewage sludge, then harmful organic contaminants are eliminated, but phosphorus is oxidized forming compounds difficult to utilize as fertilizer
Solution Approach 1:
The patent changes the thermal processing parameters by using gasification at controlled temperatures with limited oxygen instead of complete combustion. This parameter change preserves phosphorus in a reduced, fertilizer-utilizable form while still eliminating harmful organic contaminants through thermal decomposition.
3Loss of substance
If ammonia stripping is used to recover ammonia from liquid sludge, then ammonia recovery is achieved, but direct stripping is efficient only for ammonia removal not for example organic nitrogen
Solution Approach 1:
The patent performs preliminary thermal gasification of the sludge to convert organic nitrogen and other compounds into gaseous form before ammonia stripping. This preliminary action ensures that all nitrogen-containing compounds are vaporized and can be recovered as ammonia in the stripping unit, not just dissolved ammonia.
4Temperature
If dewatering and drying is used to prepare sludge for gasification, then moisture content is reduced to suitable levels, but energy consumption increases and process complexity increases
Solution Approach 1:
The patent merges the dewatering and drying operations into a single integrated thermal gasification process. The sludge is gasified directly from its dewatered state without separate drying, as the gasification process itself provides the thermal energy needed to vaporize moisture, eliminating the need for additional drying energy input.
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 enables almost complete utilization of sewage sludge and manure, with high nitrogen recovery as ammonia, phosphorus recovery, and energy recovery, producing a tailored fertilizer, while reducing transportation costs and environmental contamination.
Implementation Method 1
thermal gasification of the dewatered sewage sludge and/or animal manure to produce gaseous and solid fractions
Implementation Method 2
utilizing fluidized bed gasification
Implementation Method 3
ammonia, phosphorus, heat and cleaned gas recovery from the gasified fractions
Implementation Method 4
cooling of the gas and recovering heat
Data Source
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AI summary
According to an example aspect of the present invention, there is provided a method for recovering nutrients and energy from sewage sludge and animal manurein an efficient manner by combining unit operations of drying, thermal gasification and ammonia and phosphorus recovery.In addition, a tailored fertilizer is provided from the recovered ammonia and phosphorus.