Mercury Reduction System with Liquid Chemical Supply
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Solution Overview
Problem
Existing mercury reduction systems face challenges in simultaneously controlling the supply of reducing agents and mercury chlorinating agents in flue gas, leading to imbalances in NH3 and HCl ratios, which affect the efficiency of NOx and Hg removal, and require separate gas supply equipment and complex control systems.
Innovation Solution
A mercury reduction system that mixes ammonia, hydrogen chloride, and ammonium chloride in liquid or gaseous states, using a chemical supplying unit with a two-fluid nozzle to spray the mixed solution into the flue gas, allowing for adjustable ratios of NH3 and HCl to be supplied in a simple and efficient manner, utilizing a denitration catalyst for NOx reduction and mercury oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate gas supply equipment is used for NH3 and HCl, then the supply of reducing agent and mercury chlorinating agent can be controlled, but the equipment complexity and control system complexity increase
Solution Approach 1:
The patent combines the supply of NH3 and HCl into a single liquid injection system. The chemical supplying unit injects a liquid mixture containing both ammonia and hydrogen chloride precursors, which then mix and react in the flue gas. This merging of previously separate gas supply systems into one integrated liquid injection system reduces equipment complexity while maintaining reliable supply control of both reducing agent and mercury chlorinating agent.
Solution Approach 2:
The chemical supplying unit is designed to perform multiple functions: it supplies both the reducing agent (NH3) and the mercury chlorinating agent (HCl) through a single device. The unit can adjust the ratio of NH3 to HCl in the liquid mixture, providing universal control over both chemical supplies that previously required separate specialized equipment.
2Device complexity
If NH4Cl solution is used as both reducing agent and mercury chlorinating agent, then equipment complexity is reduced, but the ratio control of NH3 and HCl becomes imbalanced
Solution Approach 1:
The chemical supplying unit incorporates dynamic adjustment capabilities to control the ratio of NH3 to HCl in the liquid mixture. The system can vary the injection rates or concentrations of the liquid precursors based on process conditions, enabling precise ratio control despite using a unified liquid injection approach. This dynamic control mechanism resolves the imbalance issue while maintaining equipment simplicity.
Solution Approach 2:
The patent changes the physical state parameters of the chemicals from separate gases to a liquid mixture form. By controlling the concentration and injection parameters of the liquid precursors, the system achieves precise ratio control of NH3 and HCl. The liquid state allows for easier proportioning and mixing control compared to separate gas supplies, while the adjustable injection parameters enable fine-tuning of the NH3:HCl ratio.
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 enables simultaneous and efficient reduction of NOx and mercury in flue gas with precise control over NH3 and HCl ratios, reducing equipment complexity and operational costs, while maintaining high denitration and oxidation performance.
Implementation Method 1
NH3 promotes the reduction reaction of nitrogen oxide NOx in the flue gas on a denitration catalyst
Implementation Method 2
HCl promotes the oxidation reaction of Hg as the following formula (2): Hg+1/2O2+2HCl→HgCl2+H2O
Implementation Method 3
using a chemical supplying unit with a two-fluid nozzle to spray the mixed solution into the flue gas
Data Source
AI summary
A mercury reduction system according to the present embodiment is a mercury reduction system that reduces NOx and Hg in flue gas discharged from a boiler, and includes a chemical supplying unit that mixes an NH4Cl solution, an NH3 solution, and an HCl solution in liquid states, and supplies a mixed solution into a flue provided downstream of the boiler, a reduction denitration apparatus that includes a denitration catalyst reducing NOx in the flue gas with NH3 and oxidizing Hg in the presence of HCl, and a wet desulfurization apparatus that reduces Hg oxidized in the reduction denitration apparatus with limestone-gypsum slurry.