Dry Arsenic Removal from NOx Catalysts
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Solution Overview
Problem
Current methods for removing arsenic from NOx removal catalysts in coal-fired boilers are either ineffective, require large amounts of water for wet-washing, or degrade the catalyst at high temperatures, leading to disposal of used catalysts and loss of rare metals.
Innovation Solution
A low-temperature, dry process involving heat treatment of the NOx removal catalyst in a reducing atmosphere with hydrocarbon or oxygen-containing carbon compounds to separate and remove arsenic compounds, allowing for catalyst regeneration and recycling of rare metals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wet-washing method is used to remove arsenic from NOx removal catalyst, then arsenic removal is achieved, but large amounts of water are required and water disposal becomes a problem
Solution Approach 1:
The patent replaces the wet-washing mechanical system with a thermal processing system. By heating the catalyst to 500-900°C in an oxygen-containing atmosphere, arsenic is oxidized and volatilized, eliminating the need for water-based washing and disposal systems.
Solution Approach 2:
The patent utilizes phase transitions of arsenic compounds. Arsenic on the catalyst surface is oxidized to As2O5 which then volatilizes (solid to gas phase transition) at elevated temperatures, enabling easy separation from the catalyst without water consumption.
2Reliability
If high temperature treatment is used to remove arsenic from NOx removal catalyst, then arsenic removal is achieved, but the catalyst is degraded
Solution Approach 1:
The patent optimizes the temperature parameter to a specific range (500-900°C) where arsenic effectively volatilizes but the catalyst structure remains stable. This parameter optimization allows arsenic removal while preserving catalyst integrity, resolving the contradiction between removal effectiveness and catalyst strength.
Solution Approach 2:
The patent uses an oxygen-containing atmosphere during heat treatment that is controlled to oxidize arsenic without degrading the catalyst. The specific atmospheric composition enables selective oxidation of arsenic while maintaining catalyst structural integrity.
3Reliability
If conventional methods are used to remove arsenic, then some arsenic is removed, but rare metals in the catalyst are lost
Solution Approach 1:
The patent selectively extracts only the arsenic component from the catalyst through controlled oxidation and volatilization. The rare metals remain on the catalyst support structure, achieving arsenic removal without loss of valuable rare metal components.
Solution Approach 2:
The patent converts the harmful arsenic component into a beneficial separated product. By oxidizing arsenic to As2O5 and volatilizing it, the harmful substance is transformed into a removable gas phase product, while the valuable catalyst components are preserved and can be reused.
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
Enables the practical separation and removal of arsenic from NOx removal catalysts at a low temperature, preventing catalyst degradation and allowing for the recycling of rare metals like titanium dioxide, tungsten, and vanadium, without the need for extensive water disposal.
Implementation Method 1
CO and hydrocarbons are oxidized to CO2 and H2O by reaction with oxygen over a NOx removal catalyst
Implementation Method 2
heat-treating a NOx removal catalyst contaminated with the arsenic compound at a predetermined temperature in a reducing atmosphere while exposing the catalyst to hydrocarbon compounds except CH4 or oxygen-containing carbon compounds
Data Source
AI summary
Provided is a practical method for dry-separating arsenic compounds from a used NOx removal catalyst contaminated with arsenic. The method for removing arsenic compounds comprises heat-treating a NOx removal catalyst contaminated with arsenic compounds at a predetermined temperature in a reducing atmosphere while exposing the catalyst to hydrocarbon compounds (except CH4) or oxygen-containing carbon compound.