Mercury Removal via ORP Control in Scrubber Absorbing Solution
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Solution Overview
Problem
Existing methods for removing mercury from exhaust gas, such as the activated carbon adsorption method and chlorinating agent-based methods, face challenges in maintaining mercury chloride in a stable form due to reduction by SO2, leading to re-vaporization and inefficient mercury removal.
Innovation Solution
The method involves controlling the oxidation-reduction potential (ORP) in the absorbing solution by blowing air or adding an oxidizing agent into a scrubber, regulating the amount based on combustion equipment load and mercury concentration, to prevent reduction of mercury chloride back to metallic mercury, using a catalyst to convert metallic mercury to mercury chloride, and incorporating a gas-liquid contact process for enhanced removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic mercury is converted to mercury chloride by adding a chlorinating agent in a denitrification apparatus, then mercury can be removed by a downstream desulfurization apparatus, but mercury chloride is reduced back to metallic mercury by SO2 in the scrubber, leading to re-vaporization and discharge into the air
Solution Approach 1:
The invention changes the oxidation-reduction potential parameter of the absorbing solution in the scrubber by introducing an oxidizing agent or controlling aeration conditions. This parameter change prevents the reduction of mercury chloride back to metallic mercury, thereby eliminating re-vaporization while maintaining effective mercury removal through the desulfurization apparatus.
Solution Approach 2:
The invention applies preliminary anti-action by introducing an oxidizing agent into the scrubber before mercury chloride can be reduced by SO2. This preemptive measure maintains the oxidizing environment necessary to keep mercury in its chloride form, preventing the harmful re-vaporization that would otherwise occur.
2Ease of manufacture
If a mercury oxidation catalyst is installed separate from the denitrification catalyst at high temperature, then metallic mercury can be converted to mercury chloride without adding chlorinating agent, but the system complexity increases and mercury chloride stability is not ensured in the scrubber
Solution Approach 1:
The invention addresses the stability issue by changing the oxidation-reduction potential parameter in the scrubber through oxidizing agent addition or aeration control. This ensures mercury chloride remains stable throughout the system, combining the ease of separate catalyst installation with reliable mercury chloride stability.
3Reliability
If activated carbon adsorption method is used to remove metallic mercury, then mercury removal is achieved, but the device complexity increases and oxidizing agent consumption increases
Solution Approach 1:
The invention achieves high mercury removal rates while simplifying the system by changing the oxidation-reduction potential parameter in the scrubber. This allows conventional desulfurization apparatus to effectively remove mercury chloride, eliminating the need for separate activated carbon adsorption systems or additional oxidizing agent consumption.
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 ensures a higher mercury removal rate by stabilizing mercury chloride, reducing the need for specialized equipment and minimizing oxidizing agent consumption, resulting in a cost-effective and efficient mercury removal system.
Implementation Method 1
a mercury oxidation process in which mercury in the exhaust gas is converted to mercury chloride in the presence of a catalyst
Implementation Method 2
metallic mercury is converted to mercury chloride on a catalyst by adding a chlorinating agent
Implementation Method 3
a contact process in which the exhaust gas is brought into contact with an absorbing solution in a scrubber to absorb and remove mercury components from the exhaust gas
Implementation Method 4
controlling the oxidation-reduction potential (ORP) in the absorbing solution by the forced blowing of air into a scrubber or the addition of an oxidizing agent
Data Source
AI summary
The present invention provides a method for removing mercury in exhaust gas, in which mercury in exhaust gas discharged from combustion equipment is removed, characterized by including a mercury oxidation process in which mercury in the exhaust gas is converted to mercury chloride in the presence of a catalyst; a contact process in which the exhaust gas is brought into contact with an absorbing solution in a scrubber to absorb and remove mercury components from the exhaust gas; and a control process in which blowing of air or addition of an oxidizing agent into the scrubber is accomplished, and the amount of blown air or the added amount of oxidizing agent is regulated to control the oxidation-reduction potential of the absorbing agent, and a system for removing mercury in exhaust gas. According to the mercury removing method in accordance with the present invention, a phenomenon that mercury chloride is reduced into metallic mercury by SO2 etc. and the metallic mercury scatters in the exhaust gas can be prevented, and mercury in the exhaust gas can be decreased effectively.