Multi-functional Sorbent for Mercury Removal in Flue Gas
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Solution Overview
Problem
Conventional sorbents used in activated carbon injection for mercury removal from flue gas streams are inefficient in contacting, oxidizing, and sequestering mercury due to high velocity and short residence time in coal-fired power plants, failing to meet stringent emission regulations.
Innovation Solution
A multi-functional composition comprising fixed carbon, minerals, and a halogen, with a controlled particle size and pore structure, that synergistically enhances mercury oxidation and capture by increasing contact probability, reducing oxidation time, and solubilizing oxidized mercury, thereby improving mercury removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional powdered activated carbon is used for mercury removal, then the sorbent can be injected into flue gas, but the residence time is insufficient (1-2 seconds) to complete oxidation and sequestration steps efficiently
Solution Approach 1:
The invention segments the mercury removal process into three distinct functional components within a single injection: (1) oxidation catalyst to convert Hg0 to oxidized mercury, (2) sorbent material to adsorb the oxidized mercury, and (3) solubilizing medium to enhance mass transfer. This segmentation allows each function to be optimized independently while completing the entire process within the 1-2 second residence time constraint.
Solution Approach 2:
The invention uses a composite sorbent composition that integrates multiple materials with different functions into a single injectable product. The composite includes catalytic materials for oxidation, adsorbent materials for capture, and solubilizing agents for enhanced mass transfer, all working synergistically to achieve rapid mercury removal within the limited residence time.
2Speed
If the flue gas velocity is high (in excess of 25 feet/second), then the flue gas can be processed through the system, but the contact time between sorbent and mercury is insufficient for efficient removal
Solution Approach 1:
The invention changes the chemical parameters of the sorbent composition to enable rapid reaction kinetics. By incorporating catalysts that accelerate mercury oxidation and solubilizing agents that enhance mass transfer coefficients, the system achieves efficient mercury capture even at high flue gas velocities where traditional sorbents would fail due to insufficient contact time.
3Ease of operation
If conventional sorbents are used, then injection is simple, but the sorbent cannot simultaneously act as catalyst, solvent, and sorbent efficiently
Solution Approach 1:
The invention creates a universal sorbent composition that performs multiple functions simultaneously: catalyzing mercury oxidation, solubilizing mercury species to enhance mass transfer, and adsorbing captured mercury. This multi-functionality is achieved by integrating catalysts, solubilizing agents, and adsorbents into a single injectable composition that maintains operational simplicity while dramatically improving performance.
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 multi-functional composition achieves significant reductions in mercury emissions, requiring less sorbent injection while meeting or exceeding regulatory limits, as demonstrated by beta tests in coal-fired power plants, with improved reaction kinetics and mass diffusional kinetics.
Implementation Method 1
contact of the injected sorbent with the mercury species, which is typically present in very dilute concentrations in the flue gas (e.g., Hg0), which is relatively inert and not easily adsorbed, into an oxidized mercury species (e.g., Hg+ and Hg+2)
Implementation Method 2
which is significantly more soluble in an aqueous solubilizing medium such as water
Implementation Method 3
the diffusion of the oxidized mercury species into pores where it is held tightly (e.g., sequestered) without being released
Data Source
AI summary
A multi-functional composition of matter that is useful for injection into a flue gas stream to rapidly and efficiently remove mercury from the flue gas stream. The multi-functional composition of matter may include a fixed carbon sorbent and minerals, halogens in the form of halide salts, as well as other physical and chemical properties to enhance (1) the oxidation reaction kinetics for the oxidation of mercury species and (2) the mass diffusion kinetics of the mercury species.