Si-V Catalyst Selective Mercury Oxidation High-Temperature Exhaust
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Solution Overview
Problem
Existing mercury removal techniques for thermal power plants face challenges in efficiently oxidizing elemental mercury at high temperatures and preventing the oxidation of sulfur dioxide, especially in high-temperature exhaust gases with high SO2 concentrations, using traditional Ti-V catalysts.
Innovation Solution
A Si-V catalyst with a specific Si/V atomic ratio is developed, which exhibits high mercury-oxidizing activity while maintaining low SO2-oxidizing activity, allowing for effective mercury removal in high-temperature exhaust gases without enhancing SO2 oxidation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Ti-V catalyst is used to oxidize mercury metal, then mercury oxidation efficiency is improved, but SO2 oxidation activity increases at high temperatures
Solution Approach 1:
The patent changes the compositional parameters of the catalyst by replacing Ti with Si in the Ti-V catalyst system, creating a Si-V catalyst with specific Si/V atomic ratio (90-99.5:0.5-10). This parameter change fundamentally alters the catalyst's selectivity, enabling high mercury oxidation efficiency while suppressing SO2 oxidation activity even at high temperatures (200-400°C).
Solution Approach 2:
The patent employs a composite catalyst material system consisting of SiO2 and VO2 in specific proportions. This composite structure combines the mercury-oxidizing capability of vanadium with the sulfur-selective properties of silicon, creating a synergistic effect that achieves selective oxidation of mercury over sulfur at high temperatures.
2Productivity
If vanadium concentration is increased to enhance mercury-oxidizing activity, then mercury oxidation efficiency is improved, but SO2-oxidizing efficiency increases
Solution Approach 1:
Instead of increasing vanadium concentration to improve mercury oxidation, the patent changes the compositional ratio parameter by using high Si/V atomic ratio (90-99.5:0.5-10). This reverse approach—using excess silicon with controlled vanadium—achieves mercury oxidation efficiency without the accompanying increase in SO2 oxidation activity that would result from high vanadium loading.
3Adaptability or versatility
If a catalyst is used for mercury oxidation at high temperatures, then mercury removal is enabled in high-temperature exhaust gases, but catalyst selectivity for mercury over sulfur decreases
Solution Approach 1:
The patent modifies the catalyst composition parameters by substituting Ti with Si and adjusting the Si/V atomic ratio to 90-99.5:0.5-10. This compositional parameter change enables the catalyst to maintain high selectivity for mercury oxidation even at high temperatures (200-400°C), making it adaptable to high-temperature exhaust gases while preserving reliable selective performance.
Solution Approach 2:
The patent develops a composite SiO2-VO2 catalyst material with specific compositional ratios that provides both high-temperature stability and selective mercury oxidation activity. The composite structure allows the catalyst to function effectively in high-temperature environments while maintaining selectivity against sulfur oxidation.
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 Si-V catalyst achieves high mercury oxidation efficiency at temperatures up to 350°C while minimizing SO2 oxidation, reducing operational costs and eliminating the need for additional catalyst towers, thus downsizing exhaust gas-purifying apparatuses.
Implementation Method 1
a catalyst for oxidizing mercury metal... a Si-V catalyst with a specific Si/V atomic ratio is developed, which exhibits high mercury-oxidizing activity
Implementation Method 2
oxidize mercury metal into mercury in an oxidized form... high mercury oxidation efficiency at temperatures up to 350°C
Implementation Method 3
maintaining low SO2-oxidizing activity... minimizing SO2 oxidation... low SO2-oxidizing efficiency
Data Source
Figure 1~2
Figure 3~4
AI summary
A catalyst mainly containing silicon oxide and vanadium oxide and having an Si/V atomic ratio within the range from 99.5/0.5 to 85/15 is obtained by gelatinizing a liquid mixture of a colloidal silica and a vanadium compound in advance, then mixing the thus-obtained slurry by heating, and finally drying and/or firing the resulting mixture. As a catalyst for oxidizing mercury metal, this catalyst is brought into contact with an exhaust gas containing mercury metal, thereby oxidizing mercury metal.