Ionic Liquid Scrubber for Selective Mercury Oxidation
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Solution Overview
Problem
Existing methods for removing mercury from flue gases are hindered by the presence of sulfur dioxide, which interferes with the oxidation process by reducing the oxidizer in ionic liquids, necessitating a solution to minimize sulfur dioxide absorption while maintaining effective mercury removal.
Innovation Solution
The use of an ionic liquid with a large, non-electronegative anion and the addition of a polar protic organic solvent in a wet scrubber, which reduces sulfur dioxide affinity without affecting mercury absorption, allowing for selective mercury oxidation even at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If sulfur dioxide is absorbed by ionic liquid in the wet scrubber, then sulfur dioxide removal is achieved, but the oxidizer is reduced and mercury oxidation capability is lost
Solution Approach 1:
The patent changes the chemical composition parameters of the ionic liquid by selecting specific anions (BF4-, PF6-, Tf2N-) that have low affinity for sulfur dioxide. This parameter change allows the ionic liquid to maintain its oxidizer capability while still providing some sulfur dioxide removal, resolving the contradiction between sulfur dioxide removal and mercury oxidation capability
Solution Approach 2:
The patent introduces a two-stage process where a first ionic liquid (with anions like Cl-, Br-, I-) acts as an intermediary to capture sulfur dioxide, then transfers it to a second ionic liquid (with BF4-, PF6-, Tf2N- anions) for storage. This intermediary mechanism allows effective sulfur dioxide removal while preserving the mercury oxidation capability of the second ionic liquid stage
2Object-generated harmful factors
If temperature is increased to reduce sulfur dioxide affinity, then sulfur dioxide absorption is minimized, but energy consumption increases
Solution Approach 1:
Instead of changing temperature parameters, the patent changes the chemical composition parameters of the ionic liquid by selecting anions (BF4-, PF6-, Tf2N-) with inherently low sulfur dioxide affinity. This allows the system to operate at lower temperatures while still minimizing sulfur dioxide absorption, thus resolving the contradiction between sulfur dioxide control and energy consumption
Solution Approach 2:
The patent converts the naturally low sulfur dioxide affinity of certain ionic liquid anions into a beneficial feature. By selecting BF4-, PF6-, or Tf2N- anions, the system automatically achieves reduced sulfur dioxide absorption without requiring additional energy input for temperature control, turning a chemical property into an operational advantage
3Productivity
If conventional ionic liquid is used for mercury oxidation, then mercury removal is effective, but sulfur dioxide interference reduces oxidizer availability
Solution Approach 1:
The patent changes the anion composition parameter of the ionic liquid from traditional halides (Cl-, Br-, I-) to non-coordinating anions (BF4-, PF6-, Tf2N-). This parameter change reduces the ionic liquid's tendency to react with and reduce the oxidizer, thereby maintaining oxidizer availability while preserving mercury oxidation efficiency
Solution Approach 2:
The patent creates a composite absorption system using two different ionic liquids with complementary properties. The first ionic liquid (with halide anions) is optimized for sulfur dioxide capture, while the second ionic liquid (with BF4-/PF6-/Tf2N- anions) is optimized for mercury oxidation with stable oxidizer availability. This composite approach allows both functions to operate effectively without mutual interference
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 minimizes sulfur dioxide absorption while maintaining high mercury removal efficiency, enabling the operation of the scrubber at lower temperatures and improving the overall process efficiency.
Implementation Method 1
sulfur dioxide present in the flue gas is also absorbed by ionic liquids
Implementation Method 2
the use of halide-containing ionic liquids combined with oxidizers such as iodine was disclosed for absorbing and oxidizing mercury
Implementation Method 3
sulfur dioxide reduces the oxidizer associated with the ionic liquid through the following chemical reaction: SO2+Ox+2H2O→H2SO4+2H++Ox2−
Data Source
AI summary
The invention is a process for absorbing sulfur dioxide from a gaseous stream with the aid of an ionic liquid, followed by the release of sulfur dioxide from the ionic liquid on addition of a polar solvent and the regeneration of the ionic liquid.