Biotrickling Filter for High-Load SO2 and NOx Removal

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Solution Overview

Problem

Existing biological flue gas treatment methods for simultaneously removing sulfur dioxide and nitrogen oxides face challenges with low treatment concentration and removal rates, particularly due to the adverse effects of acid flue gas on microbial growth and the need for pH adjustment, which increases operational costs and complexity.

Innovation Solution

A method utilizing a specific molar concentration ratio of sulfur dioxide and nitrogen oxides in waste gas, combined with a microbial flora comprising Arthrobacter, Nitrospira, Flavobacterium, Pseudomonas, Rhodococcus, and other species, within a biotrickling-filter system, operates under acidic conditions without pH adjustment, using acid-resistant packings and a nutrient solution to enhance microbial activity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional biological flue gas treatment methods are used to simultaneously remove sulfur dioxide and nitrogen oxides, then the treatment process can operate continuously, but the removal efficiency is low and the treatment capacity is limited due to adverse effects of acid flue gas on microbial growth

Engineering Contradiction:

Improvecontinuous operation capabilityVSAvoidremoval efficiency and treatment capacity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent converts the harmful acidic environment (which previously inhibited microbial growth) into a beneficial condition by selecting and cultivating acid-resistant microbial strains that thrive in low pH conditions (pH 2.0-4.0). The acid flue gas that was damaging to conventional microbes now serves as the operating condition for specialized acid-tolerant strains, enabling high removal efficiency while maintaining continuous operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the pH parameter from the conventional neutral range (pH 6.5-7.5) to an acidic range (pH 2.0-4.0), which fundamentally alters the microbial ecosystem to favor acid-resistant strains. This parameter change enables the system to handle high concentrations of SO2 and NOx (up to 3000 mg/m3 and 2000 mg/m3 respectively) while maintaining high removal efficiency and continuous operation.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If pH adjustment is implemented to protect microorganisms from acid flue gas, then microbial growth is protected, but operational costs and system complexity increase

Engineering Contradiction:

Improvemicrobial growth stabilityVSAvoidpH control system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of adjusting pH to protect microbes from acid (conventional approach), the patent inverts the strategy by selecting microbes that are naturally resistant to acid and thriving in acidic conditions. This eliminates the need for pH adjustment systems, reducing operational costs and system complexity while maintaining microbial stability.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The acid-resistant microbial strains self-adapt to and thrive in the acidic flue gas environment without external pH control intervention. The system serves itself by utilizing the acidic condition rather than requiring external correction, eliminating the need for pH monitoring and adjustment equipment.

Inventive Principle:

Principle #25Self-service

3Device complexity

If conventional biofilters are used for flue gas treatment, then the system is simple in structure, but the treatment load capacity is insufficient to meet increasing emission standards

Engineering Contradiction:

Improvesystem structure simplicityVSAvoidtreatment load capacity

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent changes the pH parameter to acidic conditions (pH 2.0-4.0), which enables the conventional biofilter structure to handle much higher treatment loads (SO2 up to 3000 mg/m3, NOx up to 2000 mg/m3). The acid-resistant microbial strains allow the simple biofilter structure to achieve high removal efficiency (SO2 >90%, NOx >80%) without increasing system complexity.

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 method achieves high removal efficiencies of sulfur dioxide (100%) and nitrogen oxides (78%) at concentrations up to 2700-3600 mg/m3 and 1680-2300 mg/m3, respectively, without additional chemical enhancers or pH control, facilitating continuous and stable operation with acid recovery.

Implementation Method 1

Methodology Applied

Scientific EffectBiological oxidation: Oxidation

Implementation Method 2

Methodology Applied

Scientific EffectBiological reduction: Reduction

Implementation Method 3

operates under acidic conditions without pH adjustment, using acid-resistant packings and a nutrient solution to enhance microbial activity

Methodology Applied

Scientific EffectAcid resistance:

Data Source

PatentUS12569807B2Method for simultaneously removing high-load sulfur dioxide and nitrogen oxide in waste gas

Publication Date: 2026.03.10 NANJING UNIV

AI summary

A method for simultaneously removing high-load sulfur dioxide and nitrogen oxide in waste gas, relating to the technical field of industrial waste gas purification by biological methods. According to the method, the waste gas is led into a simultaneous desulfurization and denitrification packing tower and removed, microbial floras for simultaneously removing the sulfur dioxide and the nitrogen oxide are loaded on fillers of the packing tower, and the molar concentration ratio of the sulfur dioxide to the nitrogen oxide in the waste gas is (0.76˜1.06):1.