Mercury Removal Device Using In-Situ Chlorine Gasification

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Solution Overview

Problem

Existing methods for removing mercury from exhaust gases, such as those generated by coal or heavy oil combustion, are costly and inefficient, particularly when using chlorinating agents which can cause corrosion and are not economically viable for large-scale treatment, and neutral salt slurries fail to achieve desired effects at high temperatures.

Innovation Solution

Converting a non-gaseous mercury-chlorinating agent into a gaseous form using hot air from an air heater within the flue, then using this gaseous agent in combination with a solid catalyst for selective catalytic reduction and alkali absorption for mercury removal, thereby improving thermal efficiency and reducing operational costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If highly-pure hydrochloric gas is directly used as the chlorinating agent, then mercury removal efficiency is improved, but operational cost increases significantly

Engineering Contradiction:

Improvemercury removal efficiencyVSAvoidoperational cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention changes the physical state parameter of the chlorinating agent from gaseous (highly-pure hydrochloric gas) to non-gaseous (liquid or solid form), which maintains mercury removal efficiency while dramatically reducing operational costs for large-scale exhaust gas treatment

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces expensive highly-pure hydrochloric gas with a cheaper non-gaseous chlorinating agent that can be converted to gas form in situ, making the treatment economically viable for large-scale applications

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Device complexity

If neutral salt slurry such as sodium chloride is sprayed, then equipment simplicity is improved, but treatment effectiveness deteriorates at high temperatures

Engineering Contradiction:

Improveequipment simplicityVSAvoidtreatment effectiveness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The invention changes the chemical composition parameter of the sprayed material from neutral salt slurry (sodium chloride) to a non-gaseous chlorinating agent that decomposes at high temperatures to release active chlorine species, thereby maintaining treatment effectiveness at denitration equipment operating temperatures

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention performs preliminary decomposition of the non-gaseous chlorinating agent in the high-temperature environment to generate active chlorine species before they contact the mercury-containing exhaust gas, ensuring effective mercury removal

Inventive Principle:

Principle #10Preliminary action

3Reliability

If chlorinating agent is added in surplus to ensure mercury removal, then mercury removal efficiency is improved, but equipment corrosion increases

Engineering Contradiction:

Improvemercury removal efficiencyVSAvoidequipment corrosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention implements a feedback control system that monitors mercury concentration in the exhaust gas and adjusts the amount of non-gaseous chlorinating agent added accordingly, ensuring optimal mercury removal while minimizing corrosion-causing surplus agent addition

Inventive Principle:

Principle #23Feedback

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 method enables efficient and cost-effective mercury removal from exhaust gases with improved thermal efficiency and longer equipment lifespan, avoiding corrosion issues and the need for expensive steam heat exchangers, while maintaining economic viability for large-scale applications.

Implementation Method 1

converting a non-gaseous-mercury-chlorinating agent, which is non-gaseous at room temperature and normal pressure, into gaseous-mercury-chlorinating agent by heating

Methodology Applied

Scientific EffectPhase change (solid to gas): Phase Change

Implementation Method 2

heating the non-gaseous-mercury-chlorinating agent with heat of hot air generated by using the exhaust gas or hot air generated by using an air heater

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

performing selective catalytic reduction on the agent-added exhaust gas by using a solid catalyst

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 4

performing wet desulfurization on the denitrated exhaust gas by using an alkali absorbing solution

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentUS7622092B2Method and device for removing mercury

Publication Date: 2009.11.24 MITSUBISHI POWER LTD

AI summary

A mercury removing device includes a gasification unit that converts a non-gaseous-mercury-chlorinating agent, which is non-gaseous at room temperature and normal pressure, into gaseous-mercury-chlorinating agent by heating the non-gaseous-mercury-chlorinating agent with heat of hot air generated by using the exhaust gas or hot air generated by using an air heater installed in a flue that conveys the exhaust gas. The gaseous-mercury-chlorinating agent produced in this manner is supplied to the exhaust gas in the flue.