Regenerating Spent Sulfuric Acid with Excess SO2

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for regenerating spent sulfuric acid containing peroxy acids, such as Caro's acid, are either expensive and produce toxic waste through neutralization or require significant energy and result in air emissions through decomposition.

Innovation Solution

Contacting spent acid with excess SO2 to convert peroxy acids to sulfuric acid, followed by catalytic conversion of excess SO2 to SO3 and absorption into the acid stream, bypassing the decomposition step in the regeneration process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If neutralization is used to treat spent acid containing peroxy acids, then the spent acid is disposed of, but expensive base materials are consumed and toxic sulfate salt waste is produced

Engineering Contradiction:

Improvetoxic wasteVSAvoidbase materials

Core Design Contradiction:

Object-affected harmful factorsVSLoss of substance

Solution Approach 1:

The invention converts the harmful peroxy acids (H2SO5) in spent sulfuric acid into useful sulfuric acid by reacting them with SO2. The reaction H2SO5 + SO2 + H2O → 2H2SO4 transforms the hazardous oxidizing agent into the desired product, eliminating toxicity while recovering valuable material rather than requiring neutralization with expensive bases.

Inventive Principle:

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

Solution Approach 2:

Instead of discarding the spent acid through neutralization, the invention recovers sulfuric acid from the spent solution by removing peroxy acids via SO2 treatment. The sulfuric acid is then concentrated and reused, creating a circular process that eliminates waste production and base material consumption.

Inventive Principle:

Principle #34Discarding and recovering

2Productivity

If standard acid regeneration is used to treat spent acid, then sulfuric acid is recovered, but significant energy is required for decomposition and air emissions are produced

Engineering Contradiction:

Improveacid recoveryVSAvoidenergy consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The invention extracts and removes the harmful peroxy acids from spent sulfuric acid using SO2 treatment, separating the problematic components from the valuable sulfuric acid. This extraction approach allows direct recovery of sulfuric acid without requiring high-energy decomposition processes, significantly reducing energy consumption while maintaining high productivity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the chemical parameters of the spent acid by introducing SO2, which reacts with peroxy acids to form sulfuric acid. This parameter change (chemical composition modification) enables direct acid recovery without thermal decomposition, avoiding the high energy input required by conventional regeneration methods while preventing air emissions.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If spent acid containing Caro's acid is reused, then resource efficiency improves, but unwanted and uncontrollable side reactions may be triggered

Engineering Contradiction:

Improveresource efficiencyVSAvoidprocess control

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention performs preliminary removal of peroxy acids from spent sulfuric acid before reuse by treating with SO2. This preliminary action eliminates the hazardous H2SO5 that could cause uncontrollable side reactions, ensuring process reliability and safety while maintaining resource efficiency through acid reuse.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention uses SO2 as an intermediary substance to remove peroxy acids from spent sulfuric acid. The SO2 acts as a mediator that reacts with H2SO5 to form sulfuric acid, thereby eliminating the harmful oxidizing agent that could trigger unwanted side reactions while enabling safe reuse of the treated acid in subsequent processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively eliminates H2SO5 and H2O2 from spent acids, producing high-quality sulfuric acid with reduced energy consumption and minimal waste, avoiding air emissions and neutralization requirements.

Implementation Method 1

a spent acid containing H2SO5 and/or H2O2 is reacted with a quantity of SO2 in excess of a stoichiometric quantity required to convert the H2SO5 and/or H2O2 to sulfuric acid

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

The excess SO2 is catalytically converted to SO3

Methodology Applied

Scientific EffectCatalysis: Catalysis

Implementation Method 3

the SO3 is absorbed into the sulfuric acid stream

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentUS11345594B2Regeneration of acid containing peroxy acids of sulfur

Publication Date: 2022.05.31 VEOLIA NORTH AMERICA REGENERATION SERVICES LLC

AI summary

A method of treating a spent oxidizing acid is provided comprising the steps of contacting a spent acid containing peroxy acids of sulfur with a quantity of SO2 in excess of an equilibrium quantity required to convert the peroxy acids to sulfuric acid. The excess SO2 is catalytically converted to SO3, and the SO3 is absorbed into the sulfuric acid stream essentially free of H2SO5 and H2O2 to make product sulfuric acid.