Ammonia Recovery from Anaerobic Digester Sludge
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Solution Overview
Problem
Anaerobic digester sludge used as fertilizer loses significant nitrogen content during dewatering and drying due to ammonia conversion into gas, and existing ammonia removal technologies are inefficient or costly, limiting the nutrient value of the final product.
Innovation Solution
A method involving the collection and processing of gases and liquids produced during dewatering or drying to create a concentrated acidified ammonium salt solution, which is reintroduced to the solids to form a stable fertilizer pellet with increased nitrogen content, using an ammonia recovery system that includes steam stripping, vacuum distillation, or acid scrubbing to minimize ammonia loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sludge is dewatered and dried to produce fertilizer pellets, then the fertilizer becomes stable and suitable for storage and transport, but significant nitrogen content is lost due to ammonia conversion into gas
Solution Approach 1:
The patent captures ammonia gas that would otherwise be lost during drying and converts it into ammonium sulfate fertilizer by reacting with sulfuric acid. This transforms the harmful ammonia emission into a valuable nitrogen-containing fertilizer product, resolving the contradiction between stabilization and nitrogen retention
Solution Approach 2:
The patent recovers ammonia that would normally be discarded during the dewatering and drying process. By installing ammonia capture systems and converting the captured ammonia into ammonium sulfate, the process recovers the nitrogen that would otherwise be lost, maintaining fertilizer value while achieving stability
2Loss of substance
If existing ammonia removal technologies are used to prevent nitrogen loss, then ammonia emission is reduced, but the process becomes inefficient or costly
Solution Approach 1:
Instead of simply removing ammonia as a waste product, the patent converts it into a valuable ammonium sulfate fertilizer. This approach simultaneously addresses ammonia loss and creates an additional revenue stream, improving overall process efficiency while preventing nitrogen loss
Solution Approach 2:
The patent optimizes drying conditions and ammonia capture parameters to maximize nitrogen retention. By carefully controlling temperature, humidity, and acid concentration, the process achieves efficient ammonia recovery without excessive energy consumption or complex operations
3Loss of substance
If existing ammonia removal technologies are used to prevent nitrogen loss, then ammonia emission is reduced, but the cost increases
Solution Approach 1:
The patent transforms the cost center of ammonia removal into a profit center by producing ammonium sulfate fertilizer. The sulfuric acid used to capture ammonia can be sourced from flue gas desulfurization or other industrial processes, and the resulting ammonium sulfate is a marketable fertilizer product, thereby reducing net manufacturing costs while preventing nitrogen loss
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
The process retains and concentrates nitrogen in the fertilizer pellets, increasing their nutrient value and stability, allowing for efficient storage, transport, and application, while reducing the environmental impact by minimizing ammonia gas emission.
Implementation Method 1
an ammonia recovery system that includes steam stripping, vacuum distillation, or acid scrubbing
Implementation Method 2
an ammonia recovery system that includes steam stripping, vacuum distillation, or acid scrubbing
Implementation Method 3
an ammonia recovery system that includes steam stripping, vacuum distillation, or acid scrubbing
Data Source
Figure 1
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Figure 3A~3
AI summary
Sludge from an anaerobic digester is treated to recover one or more of fibers, or solids or liquids with a high nutrient content. The solids or liquids can be used as a fertilizer. The fibers can be used in a plant growing medium. Solids are separated from liquids in the sludge and dried. The solids may be dried to produce a flake or pellet. Ammonia in the liquids is recovered and used to produce a concentrated acidic ammonium salt solution. This solution may be mixed with the solids to produce a nitrogen enhanced solid. The fibers and solids or liquids can also be used in combination to produce an enhanced plant growing medium. A device and process for removing ammonia from a liquid can be used in the system or separately.