Alkaline Ionic Liquid Absorbent for Flue Gas Mercury and NOx Removal
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Solution Overview
Problem
Conventional methods for treating flue gases from fossil fuel combustion struggle to effectively remove elemental mercury (Hg0), sulfur dioxide (SO2), and oxides of nitrogen (NOx) without requiring acidic conditions, which complicates the absorption process and pH management.
Innovation Solution
An acid-free liquid absorbent comprising an aqueous solution of chlorite as a precursor to chlorine dioxide and an organic ionic liquid, which forms chlorine dioxide in situ, allowing for the oxidation and absorption of Hg0, SO2, and NOx without the need for added acids, with the oxidized products being separable into distinct phases for recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods use acidic conditions to oxidize nitrogen oxide, then oxidation efficiency is improved, but pH management complexity increases and absorption effectiveness decreases
Solution Approach 1:
The invention changes the pH parameter from acidic to alkaline conditions. The absorbent maintains pH 9-13, fundamentally altering the operating conditions from conventional acidic methods. This parameter change enables both efficient oxidation of nitrogen oxide and effective absorption of oxidation products without the complexity of pH management required in acidic systems
Solution Approach 2:
The invention uses a composite absorbent system combining sodium chlorite (chlorite source) with a specific alkaline ionic liquid. This composite material generates chlorine dioxide in situ under alkaline conditions and simultaneously provides the alkaline environment needed for effective absorption of oxidation products, resolving the contradiction between oxidation efficiency and absorption effectiveness
2Productivity
If acidic conditions are used to form chlorine dioxide from chlorite, then chlorine dioxide generation is improved, but absorption of oxidation products becomes less effective
Solution Approach 1:
The invention reverses the conventional pH approach by operating at alkaline pH 9-13 instead of acidic conditions. This parameter change enables the absorbent to both generate chlorine dioxide from chlorite and effectively absorb oxidation products like nitric acid and sulfur trioxide, eliminating the trade-off present in acidic systems
Solution Approach 2:
The alkaline ionic liquid acts as an intermediary that facilitates chlorine dioxide generation from chlorite while simultaneously serving as the absorbing medium for oxidation products. The ionic liquid's alkaline nature allows it to neutralize and absorb acidic oxidation products effectively, bridging the gap between oxidant generation and product absorption
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 enables efficient removal and recovery of pollutants from flue gases, maintaining an alkaline initial pH and adjusting to acidic conditions during use, facilitating the oxidation and separation of pollutants, thereby meeting stringent environmental regulations.
Implementation Method 1
the powerful oxidant chlorine dioxide is formed upon combining together aqueous chlorite and an ionic liquid... capable of effectively oxidizing and absorbing Hg0, SO2 and NOx
Implementation Method 2
treating the flue gas with a liquid absorbent comprising (i) a precursor of chlorine dioxide and (ii) an ionic liquid... capable of effectively oxidizing and absorbing Hg0, SO2 and NOx
Data Source
AI summary
A process for removing impurities from a flue gas, comprising treating the flue gas with a liquid absorbent comprising (i) a precursor of chlorine dioxide and (ii) an organic ionic liquid, and releasing a purified flue gas into the atmosphere. The process is useful for removing Hg, SO2 and NOx.