Mercury Removal Reagent Dosing and Reactivation
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Solution Overview
Problem
Existing dry demercurization processes face challenges in reacting quickly to mercury peaks in flue gas, leading to potential emissions exceeding regulatory limits and overconsumption of demercurization reagents, with issues of diffuse mercury release and re-emission due to recirculation of solids and adsorption characteristics of catalytic denitrification units.
Innovation Solution
A process that recirculates and reactivates a fraction of solids collected by the gas-solid separator, controlling mercury emissions by slowing down the dosage of demercurization reagent post-peak and using reactivation to enhance the efficiency and sustainability of demercurization, including the use of chemically impregnated activated carbon and additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dosage of demercurization reagent is increased rapidly to respond to mercury peaks, then mercury emissions are controlled, but reagent consumption increases excessively
Solution Approach 1:
The system performs preliminary detection of mercury peaks using a measurement device and predicts their occurrence. Based on this advance information, the control unit prepares to adjust reagent dosage appropriately, rather than reacting blindly to concentration changes. This allows the system to apply reagent more strategically - increasing dosage only when and where needed to control emissions, rather than continuously over-dosing, thus reducing overall reagent consumption while maintaining emission control reliability
Solution Approach 2:
The system implements a closed-loop feedback mechanism where the measurement device continuously monitors mercury concentration in real-time, and the control unit adjusts reagent dosage based on this feedback signal. When mercury concentration exceeds a threshold or a peak is detected, the system increases reagent dosage; when concentration returns to normal, dosage is reduced. This feedback-based adaptive control ensures emissions are controlled reliably while avoiding excessive reagent consumption during normal operating conditions
2Quantity of substance
If the dosage of demercurization reagent is reduced to save costs, then reagent consumption decreases, but mercury emissions may exceed regulatory limits during peaks
Solution Approach 1:
The measurement device detects mercury peaks in advance, providing early warning before emissions can exceed regulatory limits. The control unit uses this advance information to proactively increase reagent dosage only during peak events, rather than maintaining high dosage continuously. This preliminary detection and response mechanism ensures emission compliance is maintained during critical peak periods while allowing reagent dosage to be reduced during normal periods, thus balancing cost savings with regulatory compliance
Solution Approach 2:
The system dynamically adjusts reagent dosage based on real-time mercury concentration conditions rather than using a static dosage rate. The control unit modifies the injection rate adaptively - increasing dosage when mercury peaks are detected and decreasing dosage when concentrations are normal. This dynamic control strategy ensures emission compliance is maintained during variable operating conditions while optimizing reagent consumption to avoid unnecessary waste during low-risk periods
3Productivity
If solids are recirculated to enhance pollutant capture, then residence time of reagents increases, but diffuse mercury release and re-emission occur
Solution Approach 1:
The system extracts and removes the problematic recirculated solids containing adsorbed mercury from the recirculation loop using a separation device. By taking out these solids before they can release mercury back into the flue gas, the system prevents the diffuse release and re-emission problem while maintaining the benefits of recirculation during normal operation. The separated solids are disposed of or treated separately, breaking the cycle of mercury release that would otherwise occur during recirculation
Solution Approach 2:
The system converts the harmful effect of recirculated solids releasing mercury into a benefit by using the measurement device to detect when these solids become saturated with mercury. Once saturation is detected, the control unit stops recirculation and triggers solid removal. Thus, the very recirculation process that causes diffuse release is used beneficially to concentrate mercury onto solids, which are then removed in a controlled manner, transforming the harm into an effective capture mechanism
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
Effectively neutralizes diffuse mercury release, reduces emissions, and prevents uncontrolled re-emission, ensuring compliance with regulatory limits while optimizing reagent usage and extending reagent residence time for enhanced pollutant capture.
Implementation Method 1
the mercury is captured by a demercurization reagent, such as adsorbents, typically activated carbon, lignite coke, halogenated additives, and sulfur additives
Implementation Method 2
subsequently separated from the fumes by a gas-solid separator, such as bag filters or electrostatic precipitators
Data Source
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AI summary
In this process, flue gases to be treated are sent to a gas-solid separator upstream of which a mercury removal reagent is introduced. A recycled fraction of the solids collected by the separator is sent to a treatment device for reactivation before being reintroduced upstream of the separator. The mercury removal reagent is dosed by carrying out the following operations at each time step: a) a mercury concentration value is determined from (i) the mercury concentration in the flue gases upstream of the points of introduction of the mercury removal reagent and the output stream of the treatment device and/or (ii) the mercury concentration in the flue gases downstream of the separator;and b) the occurrence of mercury peaks is taken into account so that (i) outside a period, which begins substantially at the apogee of each mercury peak, the demercurizing reagent is titrated by applying to the mercury concentration value a first titration function increasing with the mercury concentration value, and (ii) during the period, the demercurizing reagent is titrated by applying to the mercury concentration value a second titration function which titrates the demercurizing reagent at a value greater than that titrated by the first function at the time considered, the second titration function being decreasing with time until it titrates at a value equal to or less than that titrated by the first function at a time when the period ends.;