Emission Control System Using HBr for Mercury Removal
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Solution Overview
Problem
Current methods for treating mercury-contaminated gases in flue gases from coal combustion are inefficient in removing mercury, with existing technologies failing to effectively oxidize elemental mercury (Hg0) and capture it without re-emission, especially in systems with high chlorine content and varying temperature conditions.
Innovation Solution
Introducing a hydrogen halide, such as HBr, into the mercury-contaminated gas stream to create a doped particulate matter that coats filtration media, allowing for the removal of mercury through electrostatic forces and oxidation of Hg0 to Hg2+, which binds with fly ash, thereby reducing mercury emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to treat mercury-contaminated gas, then the system structure remains simple, but mercury removal efficiency is low and re-emission occurs
Solution Approach 1:
The patent introduces HBr as an intermediary substance that facilitates mercury oxidation and capture. HBr acts as a mediator between the flue gas and the filtration system, enabling effective mercury removal without requiring fundamental changes to the existing electrostatic precipitator structure. This resolves the contradiction by adding a chemical intermediary rather than complex mechanical systems.
Solution Approach 2:
The patent changes the chemical parameters of the flue gas by injecting HBr, which alters the oxidation state of mercury from elemental (Hg0) to oxidized forms (Hg2+). This parameter change enables the existing filtration system to capture mercury effectively, improving removal efficiency without increasing structural complexity.
2Reliability
If HBr injection is used to oxidize Hg0, then mercury oxidation efficiency improves, but the system becomes more complex and requires additional injection equipment
Solution Approach 1:
The patent employs HBr injection that leverages the existing thermal energy and flow conditions of the flue gas to achieve spontaneous oxidation of mercury. The system uses the natural characteristics of the flue gas stream to facilitate the chemical reaction, reducing the need for additional heating or pressurization equipment and minimizing overall system complexity while maintaining high oxidation efficiency.
3Productivity
If filtration media is coated with doped particulate matter, then mercury capture effectiveness increases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies doped particulate matter to the filtration media in advance, creating a pre-conditioned surface that is optimized for mercury capture. This preliminary coating action ensures that when flue gas passes through the filter, mercury is immediately captured by the bromine-containing particulate layer, enhancing capture effectiveness without requiring complex real-time processing.
4Productivity
If electrostatic forces are used to remove doped particulate matter, then mercury removal efficiency improves, but energy consumption increases
Solution Approach 1:
The patent replaces mechanical collection methods with electrostatic forces for removing doped particulate matter containing mercury. The electrostatic precipitation process uses electric fields to attract and collect charged particles, achieving high removal efficiency with lower energy consumption compared to mechanical filtration or centrifugal separation methods.
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 method achieves greater than 50% mercury removal and maintains effectiveness across varying temperature conditions, with residual effects lasting beyond the initial HBr injection period, demonstrating improved mercury control and reduced re-emission.
Implementation Method 1
oxidation of Hg0 to Hg2+
Implementation Method 2
binds with fly ash
Implementation Method 3
removing greater than 50% of the doped particulate matter from the mercury contaminated gas stream
Data Source
AI summary
Methods of treating mercury contaminated gas comprising: introducing a hydrogen halide selected from HBr and HI into a mercury contaminated gas stream containing a quantity of particulate matter at an introduction rate sufficient to create a concentration of at least 0.1 ppmvd; wherein greater than 50% of all particulate matter in the mercury contaminated gas stream is a native particulate matter; contacting a quantity of active bromine with the native particulate matter; creating a doped particulate matter; coating a filtration media with the doped particulate matter; and passing a portion of the mercury contaminated gas stream through the doped particulate matter on the filtration media and other related methods are disclosed herein.