SCR Catalyst Protection via Metal-Bearing Halogen Conversion
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Solution Overview
Problem
SCR catalysts in emission control systems for boilers and kilns face contamination and deactivation due to halogen compounds, leading to reduced catalytic activity and lifespan, and increased emissions of mercury and selenium, which are challenging to manage effectively.
Innovation Solution
The method involves adding metal-bearing compounds to the combustion zone or flue gas stream to convert halogen-containing compounds into elemental halogens, which then oxidize mercury, and using iron compounds to bind phosphorus and reduce its deactivation effects on the SCR catalyst, thereby reducing halogen levels and enhancing catalytic activity and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If halogen-containing compounds are used to control mercury emissions, then mercury control is improved, but halogen levels increase which reduces SCR catalyst activity and lifespan
Solution Approach 1:
The patent introduces metal-bearing compounds (such as iron compounds) as intermediary substances that facilitate the conversion of halogen-containing compounds into elemental halogens. These intermediaries enable mercury oxidation without requiring high concentrations of halogen compounds that would harm the SCR catalyst, thus mediating between mercury control requirements and catalyst protection needs.
Solution Approach 2:
The patent changes the chemical form and concentration parameters of halogen compounds in the flue gas stream. By converting halogen-containing compounds into elemental halogens through metal-bearing compound reactions, the system achieves effective mercury oxidation at reduced halogen levels, thereby changing the parameter of halogen concentration to resolve the contradiction between mercury control and catalyst protection.
2Duration of action of stationary object
If halogen levels are reduced to protect SCR catalyst, then catalyst lifespan is improved, but mercury control effectiveness decreases
Solution Approach 1:
The patent converts the potentially harmful effect of metal-bearing compounds (which could poison the catalyst) into a beneficial function by utilizing their ability to catalyze the conversion of halogen-containing compounds into elemental halogens. This conversion process enables effective mercury oxidation at lower halogen concentrations, turning what could be harmful into a protective mechanism for the SCR catalyst while maintaining mercury control effectiveness.
3Quantity of substance
If metal-bearing compounds are added to convert halogen compounds, then halogen levels are reduced, but system complexity increases
Solution Approach 1:
The patent employs metal-bearing compounds that perform multiple functions: they convert halogen-containing compounds into elemental halogens for mercury oxidation, and simultaneously catalyze the reduction of halogen levels in the flue gas. This multi-functionality reduces the need for separate treatment stages and minimizes system complexity while achieving the desired reduction in halogen levels.
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 effectively reduces halogen levels, prevents catalyst contamination, increases catalytic activity and lifespan, and controls mercury and selenium emissions, leading to improved emission control and reduced operational costs.
Implementation Method 1
providing one or more metal-bearing compounds to a combustion zone or flue gas stream of a furnace, or boiler, at a point that is both prior to entry of the flue gas into an SCR as well as after a point that where the majority of the one or more halogen-bearing compounds have been converted to the corresponding gaseous hydrogen halides; permitting one or more metal-bearing compounds to catalyze the conversion of the corresponding one or more hydrogen halides to one or more corresponding elemental halogen compounds
Implementation Method 2
permitting the resulting one or more corresponding elemental halogen compounds to react with gaseous mercury present in the combustion zone or flue gas stream of the furnace, or boiler, thereby resulting in oxidation of the gaseous mercury so as to convert the gaseous mercury into one or more corresponding mercury halides
Implementation Method 3
using iron compounds to bind phosphorus and reduce its deactivation effects on the SCR catalyst
Data Source
AI summary
The present invention relates generally to the field of emission control equipment for boilers, heaters, kilns, or other flue gas-, or combustion gas-, generating devices (e.g., those located at power plants, processing plants, etc.) and, in particular to a new and useful method and apparatus for: (i) reducing halogen levels necessary to affect gas-phase mercury control; (ii) reducing or preventing the poisoning and/or contamination of an SCR catalyst; and/or (iii) controlling various emissions. In still another embodiment, the present invention relates to a method and apparatus for: (A) simultaneously reducing halogen levels necessary to affect gas-phase mercury control while achieving a reduction in the emission of mercury; and/or (B) reducing the amount of selenium contained in and/or emitted by one or more pieces of emission control equipment for boilers, heaters, kilns, or other flue gas-, or combustion gas-, generating devices (e.g., those located at power plants, processing plants, etc.).