Ionic Liquid Absorbent for Mercury Removal in Flue Gas
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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 oxidizing capacity of ionic liquids used in mercury absorption processes, leading to reduced mercury removal efficiency.
Innovation Solution
The use of a wet scrubber process with a liquid absorbent comprising an ionic liquid and an oxidizer, where a polar protic organic solvent is added to minimize sulfur dioxide absorption and maintain mercury oxidation efficiency, even at lower operating temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ionic liquid and oxidizer are used to remove mercury from flue gas, then mercury removal efficiency is improved, but sulfur dioxide absorption increases which interferes with the oxidizing capacity
Solution Approach 1:
A polar aprotic solvent is introduced as an intermediary substance to modify the ionic liquid's properties. The solvent acts as a mediator that reduces the ionic liquid's affinity for sulfur dioxide while preserving its mercury oxidation capability, thereby resolving the interference problem without sacrificing mercury removal efficiency
Solution Approach 2:
The chemical composition parameters of the liquid absorbent are changed by adding a polar aprotic solvent. This parameter modification alters the absorbent's selectivity characteristics, decreasing sulfur dioxide absorption affinity while maintaining mercury oxidation functionality, thus resolving the technical contradiction
2Use of energy by stationary object
If operating temperature is reduced to enhance process efficiency, then energy consumption is lowered, but sulfur dioxide absorption increases interfering with mercury oxidation
Solution Approach 1:
The polar aprotic solvent serves as a mediator that decouples the relationship between temperature and sulfur dioxide absorption. It allows the system to operate at lower temperatures without the penalty of increased sulfur dioxide absorption, effectively resolving the contradiction between energy efficiency and oxidation capacity
Solution Approach 2:
The addition of polar aprotic solvent changes the thermal-response characteristics of the ionic liquid. This parameter change makes sulfur dioxide absorption less sensitive to temperature reductions, enabling low-temperature operation while preventing harmful sulfur dioxide absorption interference
3Quantity of substance
If ionic liquid affinity towards sulfur dioxide is high, then sulfur dioxide is absorbed more, but this reduces the oxidizing capacity needed for mercury removal
Solution Approach 1:
The polar aprotic solvent acts as a selective intermediary that modifies the ionic liquid's interaction preferences. It reduces the affinity between the ionic liquid and sulfur dioxide while preserving the oxidizer's ability to react with mercury, thus resolving the contradiction between sulfur dioxide absorption quantity and oxidizing capacity reliability
Solution Approach 2:
The polar aprotic solvent creates local chemical environment modifications within the ionic liquid system. It selectively alters the local affinity characteristics toward sulfur dioxide without affecting the local oxidizing capacity toward mercury, thereby resolving the contradiction through localized property modification
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 selectively removes mercury from flue gases while minimizing sulfur dioxide absorption, allowing for effective mercury removal at temperatures lower than those required without the solvent, thus enhancing the process's efficiency and operational flexibility.
Implementation Method 1
a liquid absorbent comprising an ionic liquid and an oxidizer
Implementation Method 2
Sulfur dioxide present in the flue gas is also absorbed by ionic liquids
Implementation Method 3
wherein a polar protic organic solvent is added to minimize sulfur dioxide absorption
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Provided is a process for controlling heavy metal (e.g., mercury) emission in S02-containing flue gas, comprising passing a stream of the flue gas (2) through a wet scrubber (1) where it is brought into contact with a liquid absorbent (8) comprising an ionic liquid, an oxidizer (11) and polar protic organic solvent, wherein the amount of said organic solvent is adjusted such that the SO2 absorption is minimized while operating said wet scrubber at a temperature lower than the normal working temperature that would be used in the absence of said solvent. The process may be preceded by an initial stage where a fluoride-containing liquid is used for reducing the amount of sulfur dioxide in the flue gas stream; the sulfur dioxide can be subsequently desorbed from the fluoride-containing liquid upon the addition of a polar solvent.