Mercury Reduction System Using Gaseous NH3 and HCl Injection
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Solution Overview
Problem
Existing mercury reduction systems face challenges in simultaneously and uniformly supplying reducing agents and mercury chlorinating agents in any proportion, leading to inefficiencies and potential damage from thermal shock when using liquid NH4Cl solutions, which results in fluctuating concentrations and equipment damage.
Innovation Solution
A mercury reduction system that employs a liquid material spraying unit to inject a mixed solution of oxidation-reduction agents as a liquid and a gaseous material spraying unit to inject reducing agents and mercury chlorinating agents as gases, using a denitration catalyst to reduce NOx and oxidize mercury, with a two-fluid nozzle for precise delivery, allowing for adjustable ratios of NH3 and HCl based on flue gas conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If liquid NH4Cl solution is sprayed into the flue, then the reducing agent and mercury chlorinating agent can be supplied, but thermal shock damages equipment and concentration distribution becomes non-uniform
Solution Approach 1:
The patent changes the physical state parameter of the reducing agent and mercury chlorinating agent from liquid to gas. By supplying NH3 and HCl as gaseous materials instead of liquid NH4Cl solution, the system eliminates thermal shock damage to equipment while maintaining the chemical functions of reducing NOx and chlorinating mercury.
Solution Approach 2:
The patent introduces a denitration catalyst as an intermediary substance that facilitates the reduction of NOx by NH3 and the oxidation of Hg by HCl. The catalyst enables these reactions to proceed efficiently at lower temperatures, avoiding the need for high-temperature liquid spraying that causes thermal shock.
2Ease of operation
If liquid NH4Cl solution is sprayed, then agents can be supplied, but concentration distribution fluctuates and becomes non-uniform
Solution Approach 1:
The patent changes the physical state from liquid to gas, which improves concentration distribution uniformity. Gaseous NH3 and HCl mix more uniformly with the flue gas flow compared to liquid droplets, eliminating the concentration fluctuations and non-uniform distribution problems associated with liquid spraying.
3Measurement precision
If separate gas supply equipment is used for NH3 and HCl, then precise control of agent ratios is possible, but device complexity increases
Solution Approach 1:
The patent segments the supply system into separate injection points for NH3 and HCl gases, allowing independent control of each agent's flow rate. This segmentation enables precise adjustment of the NH3/HCl ratio according to the specific NOx and Hg concentrations in the flue gas, while keeping the equipment relatively simple through separate but coordinated injection systems.
4Reliability
If liquid material is sprayed, then equipment damage is reduced, but uniform supply of agents in any proportion becomes difficult
Solution Approach 1:
The patent changes the physical state to gas, which simultaneously achieves both equipment durability and supply ratio flexibility. Gaseous NH3 and HCl can be supplied in any proportion through independent flow control, and since they are already in gaseous form, no liquid spraying is required, thus avoiding thermal shock and equipment damage while maintaining flexibility in agent ratio adjustment.
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 uniform supply of reducing and mercury chlorinating agents, reducing equipment damage and fluctuating concentrations, while maintaining effective NOx and mercury reduction performance.
Implementation Method 1
a reduction denitration apparatus that includes the denitration catalyst reducing nitrogen oxide in the flue gas with ammonia
Implementation Method 2
oxidizing mercury in the presence of the hydrogen chloride
Implementation Method 3
spraying a liquid material obtained by dissolving an oxidation-reduction agent reducing nitrogen oxide in the flue gas by a denitration catalyst and oxidizing mercury in a presence of hydrogen chloride, into a flue of the boiler in a liquid state
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 an NH4Cl solution spraying unit that sprays an NH4Cl solution into a flue of the boiler in a liquid state, a mixed gas spraying unit that is provided downstream of the NH4Cl solution spraying unit and sprays mixed gas containing NH3 gas and HCl gas into the flue, 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 a limestone-gypsum slurry.