UV Absorption Sensor for Mercury Vapor Monitoring
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Solution Overview
Problem
Conventional methods for monitoring elemental mercury in coal-furnace flue gases are slow, expensive, and poorly suited for real-time measurement due to the need for physical gas sample extraction, which results in delayed responses and is not suitable for continuous emission monitoring.
Innovation Solution
An optical sensor system that measures ultraviolet light absorption in the 254 nm wavelength range to determine elemental mercury concentrations in situ within coal-furnace flue gas flows, compensating for light absorption by other gases like sulfur dioxide to provide real-time monitoring and correction for accurate mercury vapor measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional wet chemistry analysis with physical gas sample extraction is used, then mercury monitoring can be performed, but the response time is delayed and the system is not suitable for real-time measurement
Solution Approach 1:
The patent replaces the mechanical gas sample extraction system with an optical measurement system. Instead of physically extracting gas samples through conduits for remote analysis, the system uses optical sensors to directly measure mercury concentrations in the flue gas stream, eliminating the time delay associated with sample transport and enabling real-time monitoring.
Solution Approach 2:
The patent introduces light absorption as an intermediary measurement method. By measuring the absorption of light at specific wavelengths by mercury vapor in the flue gas, the system can determine mercury concentrations without direct physical contact or sample extraction, thereby achieving continuous real-time monitoring.
2Ease of operation
If physical gas sample extraction via conduit pipe is used, then mercury analysis can be performed remotely, but the transfer of gas samples provides inherent delayed response
Solution Approach 1:
The patent eliminates the mechanical conduit system for gas sample transport by using optical measurement techniques. The optical sensor measures mercury concentrations directly in the flue gas stream at the point of emission, removing the need for physical sample extraction and subsequent transport to a remote analysis location.
Solution Approach 2:
The system performs self-measurement at the source without requiring external sample transport infrastructure. The optical sensor continuously monitors mercury levels in the flue gas stream directly where emissions occur, providing immediate data without relying on sample extraction and transfer processes.
3Measurement precision
If conventional mercury monitoring methods are used, then analysis can be performed, but the system is expensive and requires highly trained staff
Solution Approach 1:
The patent replaces complex chemical analysis systems with optical measurement technology. Instead of requiring wet chemistry laboratories, extraction equipment, and highly trained analytical chemists, the system uses optical sensors that can be installed directly in the flue gas stream to continuously monitor mercury concentrations.
Solution Approach 2:
The patent creates an optical copy or signature of the mercury vapor in the flue gas by measuring light absorption characteristics. This optical signature allows for continuous, non-intrusive monitoring without requiring physical extraction or complex chemical processing, simplifying the overall system operation.
4Productivity
If optical sensor measures UV light absorption at 254 nm, then real-time mercury monitoring is achieved, but other gases like sulfur dioxide also absorb UV light causing interference
Solution Approach 1:
The patent segments the UV spectrum into multiple wavelength regions. By measuring light absorption at multiple specific wavelengths (including 254 nm and other wavelengths where sulfur dioxide absorbs), the system can distinguish between the absorption contributions of different gases and calculate accurate mercury concentrations through differential analysis.
Solution Approach 2:
The patent changes the measurement parameters by using multiple wavelength values instead of a single wavelength. By varying the wavelength parameter across multiple points in the UV spectrum, the system can differentiate between the absorption characteristics of mercury vapor and sulfur dioxide, enabling accurate mercury measurement even in the presence of interfering gases.
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
Enables continuous, real-time monitoring of elemental mercury in coal-fired power plant flue gas emissions, improving operational efficiency and environmental control by providing immediate feedback on mercury capture and emission levels without the drawbacks of traditional extraction methods.
Implementation Method 1
measuring ultraviolet (UV) light absorption in the 254 nm+/−1 nm, (253-255 nm) wavelength range
Data Source
AI summary
An apparatus and method operable for the continuous monitoring of a gas stream including an optical sensor operable to monitor and/or measure Hg concentrations in a flue gas by calculating the absorbance of the ultraviolet light thereby at a range of wavelength 253.7 nm+/−0.05 nm. The apparatus therefore provides as a spectrally narrow UV light source, a mercury lamp. The spectrally broad UV light source includes a UV LED. A 2×2 coupler is provided to mix the narrow and broad UV light energy which is propagated through the gas stream. The invention recognizes that measurement of radiation absorption at the 254 nm+/−1.5 nm range will result in not only from Hg0, but also from the SO2 component in the flue gas. To compensate for sulphur dioxide, measurement of energy absorption for both specially narrow radiant energy in the 253.7 nm+/−0.5 nm range, as well as ultraviolet (UV) light at a comparatively spectrally broad range of 254 nm+/−20 nm is performed recognizing that sulphur dioxide in the emitted flue gas will tend to absorb the ultraviolet light over the broader UV range. Ultraviolet light absorption over the broader range is calculated to provide a correction factor used to correct energy absorption values over the narrow radiant energy range, providing more accurate measurement of the absorption caused by the presence of mercury.