SNCR Reducing Nitrogen Dioxide in PDH Exhaust Gas

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Solution Overview

Problem

The olefin production process, particularly in propane dehydrogenation (PDH), generates high levels of nitrogen dioxide during catalyst regeneration, leading to yellow plumes and environmental concerns, for which existing techniques like SCR are costly and inefficient, while SNCR methods are not effectively applied in continuous PDH processes.

Innovation Solution

A method using selective non-catalytic reduction (SNCR) with a mixed reducing agent comprising glycerin and ethylene glycol injected into the exhaust gas at specific temperatures and ratios in a waste heat boiler to reduce nitrogen dioxide content below 15 ppm, eliminating the need for additional reactors and catalyst replacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If selective catalytic reduction (SCR) is used to remove nitrogen dioxide, then nitrogen dioxide removal efficiency is improved, but facility size and investment cost increase

Engineering Contradiction:

Improvenitrogen dioxide contentVSAvoidfacility size

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts the catalyst from the reduction process, using only the reducing agent (ammonia or urea) injected directly into the exhaust gas flow. This eliminates the need for complex catalyst apparatus while maintaining nitrogen dioxide removal effectiveness through thermal decomposition reactions at elevated temperatures.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces ammonia or urea as an intermediary substance that mediates the reduction of nitrogen dioxide. These compounds react with nitrogen dioxide in the exhaust gas to form nitrogen and water vapor, serving as a simple yet effective mediator without requiring additional catalyst materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If selective catalytic reduction (SCR) is used to remove nitrogen dioxide, then nitrogen dioxide removal efficiency is improved, but installation cost increases

Engineering Contradiction:

Improvenitrogen dioxide contentVSAvoidinstallation cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent employs inexpensive ammonia or urea as disposable reducing agents that are continuously injected into the exhaust stream. These cheap chemicals decompose and react to remove nitrogen dioxide, eliminating the need for expensive catalyst materials and reducing overall installation and operational costs.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent replaces the mechanical catalyst-based system with a chemical injection system. By substituting the physical catalyst apparatus with a simpler injection mechanism that delivers ammonia or urea, the system achieves nitrogen dioxide removal at significantly lower installation and maintenance costs.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If selective non-catalytic reduction (SNCR) is used to remove nitrogen dioxide, then installation cost is reduced, but nitrogen dioxide removal efficiency decreases

Engineering Contradiction:

Improveinstallation costVSAvoidnitrogen dioxide content

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes the temperature parameter of the exhaust gas, maintaining it within the range of 350-450°C to maximize the effectiveness of ammonia or urea injection. By controlling this thermal parameter, the system achieves efficient nitrogen dioxide removal through SNCR without requiring catalysts, thus reducing installation costs while maintaining removal effectiveness.

Inventive Principle:

Principle #35Parameter changes

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 efficiently reduces nitrogen dioxide in the PDH process, preventing yellow plumes and offering economic benefits by integrating with existing heat exchange processes, reducing installation and maintenance costs, and maintaining continuous operation without catalyst degradation.

Implementation Method 1

reducing nitrogen dioxide by injecting a mixed reducing agent to the exhaust gas, the mixed reducing agent comprising glycerin and ethylene glycol

Methodology Applied

Scientific EffectSelective non-catalytic reduction: Reduction

Data Source

PatentUS11484834B2Method for reducing nitrogen dioxide in exhaust gas generated during olefin production process

Publication Date: 2022.11.01 GAS CO

AI summary

Provided is a method for using selective non-catalytic reduction to reduce nitrogen dioxide in exhaust gas generated during an olefin production process. Nitrogen dioxide generated in a catalyst regeneration step of a continuous PDH process can be efficiently removed by the method of the present disclosure. Ultimately, the generation of visible fumes can be prevented through the removal of nitrogen dioxide.