Exhaust Gas Treatment with Upstream Reductant Removal for NOx Control

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Solution Overview

Problem

The unburned content of reductants in combustion exhaust gas leads to imbalanced ratios with specific substances, making it difficult to adjust the supply amount of reductants effectively for reducing NOx in combustion exhaust gases.

Innovation Solution

An exhaust gas treatment apparatus with a first reductant decreasing part upstream of the second reductant supply part to decrease the unburned reductant content, combined with a second reductant supply part to adjust the supply amount based on specific substance concentration, using catalysts and neutralizers to facilitate balanced reductant ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a reductant-containing fuel is used to reduce NOx, then the reduction effect is achieved, but the unburned reductant content causes imbalanced ratios and control difficulties

Engineering Contradiction:

ImproveNOx reduction effectVSAvoidadjustment of reductant supply amount

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent segments the reductant supply into two distinct sources: (1) first reductant contained in the fuel itself, and (2) second reductant supplied separately through a dedicated supply device. This segmentation allows independent control of the second reductant supply amount based on actual NOx concentration, while the first reductant from fuel provides baseline reduction, thereby resolving the control difficulty caused by unburned reductant interference

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary control mechanism that measures NOx concentration in the exhaust gas and uses this information to adjust the supply amount of the second reductant. This intermediary feedback loop enables precise control of the total reductant effect (first reductant from fuel + second reductant from supply device), overcoming the inability to control reductant supply when using reductant-containing fuel

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the supply amount of reductant is adjusted based on NOx concentration, then precise control is achieved, but unburned reductant concentration distribution causes imbalanced ratios

Engineering Contradiction:

ImproveNOx concentration measurementVSAvoidreductant to NOx ratio

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent applies preliminary action by supplying the second reductant through a dedicated supply device positioned upstream, allowing the reductant to mix and react before the exhaust gas reaches the measurement point. This ensures that the NOx concentration measured reflects the actual reaction conditions, and the control system can adjust the second reductant supply to maintain stable reductant to NOx ratios despite variations in first reductant from fuel

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback control system where NOx concentration is continuously measured in the exhaust gas, and this measurement is used to adjust the supply amount of the second reductant. This closed-loop feedback ensures that the total reductant effect (first reductant from fuel + second reductant from supply device) maintains a stable and appropriate ratio to NOx concentration, overcoming the compositional instability caused by unburned reductant distribution

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

Enables precise adjustment of reductant supply amounts, reducing NOx concentrations in the exhaust gas, minimizing variations in reductant ratios, and maintaining optimal exhaust gas treatment efficiency.

Implementation Method 1

using catalysts and neutralizers to facilitate balanced reductant ratios

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 2

supplying a second reductant for reducing the specific substance in the combustion exhaust gas

Methodology Applied

Scientific EffectReduction reaction: Reduction

Data Source

PatentUS20250249406A1Exhaust gas treatment apparatus, combustion facility, and exhaust gas treatment method

Publication Date: 2025.08.07 MITSUBISHI HEAVY IND LTD

AI summary

An exhaust gas treatment apparatus includes: a second reductant supply part, disposed in a flow path of combustion exhaust gas of a fuel containing a first reductant that is capable of reducing a specific substance, for supplying a second reductant for reducing the specific substance in the combustion exhaust gas to the combustion exhaust gas; and a first reductant decreasing part, disposed upstream of the second reductant supply part in the flow path, for decreasing the first reductant in the combustion exhaust gas.