Ammonia Decomposition in Fly Ash Using Controlled Thermal Processing
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Solution Overview
Problem
Current methods for reducing NOx emissions in industrial boilers lead to ammonia slip, contaminating fly ash with high ammonia concentrations, making it unsuitable for reuse and causing environmental concerns, as they often require excessive ammonia use and introduce additional chemicals or water emissions.
Innovation Solution
A system and method involving a fluidized bed process that maintains ammonia-laden fly ash at a temperature between 500° F. and 842° F. for ammonia decomposition, using a temperature control unit with thermocouples and heat sources like hot fly ash, exhaust gas, or a liquefied petroleum gas burner to achieve ammonia removal without introducing additional chemicals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If SCR or SNCR systems are used to reduce NOx emissions, then nitrogen oxide emissions are reduced, but ammonia slip occurs and contaminates fly ash with high ammonia concentrations
Solution Approach 1:
The patent extracts and removes ammonia from fly ash through a thermal decomposition process. The fly ash is heated to temperatures between 700-900°F to decompose ammonium compounds and release ammonia, which is then captured and removed from the fly ash stream, separating the harmful ammonia from the reusable fly ash material.
Solution Approach 2:
The patent recovers ammonia from contaminated fly ash through thermal decomposition and captures it for potential reuse. The process converts ammonium compounds in the fly ash back into ammonia gas, which is then condensed and collected, allowing the fly ash to be discarded of its ammonia contamination while the ammonia is recovered for beneficial use.
2Object-generated harmful factors
If excess ammonia is introduced in SNCR systems, then NOx reduction is achieved, but ammonia slip increases and fly ash becomes unsuitable for reuse
Solution Approach 1:
The patent extracts and removes ammonia from fly ash through a thermal decomposition process. The fly ash is heated to temperatures between 700-900°F to decompose ammonium compounds and release ammonia, which is then captured and removed from the fly ash stream, separating the harmful ammonia from the reusable fly ash material.
Solution Approach 2:
The patent changes the temperature parameter of the fly ash from ambient conditions to elevated temperatures (700-900°F) to induce thermal decomposition of ammonium compounds. This parameter change transforms the stable ammonium salts in the fly ash into decomposable forms that release ammonia, enabling removal and restoration of the fly ash for reuse.
3Object-affected harmful factors
If fly ash is washed with water to remove ammonia, then ammonia is removed from fly ash, but additional water emissions and chemical contamination occur
Solution Approach 1:
The patent replaces the mechanical/chemical washing process with a thermal processing system. Instead of using water and chemicals to leach ammonia from fly ash, the patent uses controlled thermal decomposition at 700-900°F to break down ammonium compounds and release ammonia as gas, which is then captured and removed, eliminating the need for water washing and associated emissions.
Solution Approach 2:
The patent utilizes phase transitions of ammonia from solid/liquid bound state in ammonium compounds to gaseous state through thermal decomposition. The ammonium salts in fly ash are heated to decompose and release ammonia gas, which is then condensed back to liquid or solid form for removal, using phase change rather than chemical washing to achieve separation.
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
Effectively decomposes ammonia from fly ash, reducing ammonia content to acceptable levels for reuse in concrete applications while minimizing NOx emissions and avoiding chemical contamination, with the process being efficient and adaptable for various types of fly ash.
Implementation Method 1
a temperature control unit, such as a thermocouple
Implementation Method 2
a heated flighted auger conveys and mixes the fly ash while heating it to a temperature between 500° F. and 842° F.
Implementation Method 3
maintains the supply of ammonia-laden fly ash at a decomposition temperature greater than 500° F. and less than 842° F. to decompose the ammonia in the ammonia-laden fly ash
Implementation Method 4
A system and method involving a fluidized bed process that maintains ammonia-laden fly ash at a temperature between 500° F. and 842° F.
Data Source
AI summary
A system and method for decomposing ammonia from fly ash contaminated with ammonia is provided which includes maintaining the temperature of a bed of ammonia-contaminated fly ash at a decomposition temperature greater than 500° F. and less than 842° F. to decompose the ammonia from the fly ash. In a preferred embodiment, the ammonia-laden fly ash is maintained at a temperatures less than a lowest carbon combustion temperature at which substantial combustion of carbon in fly ash begins to occur. A preferred embodiment includes a first chamber operating at a decomposition temperature greater than 500° F. and less than 842° F. followed by a second chamber operating at a higher carbon combustion temperature for carbon burn-out.