Stabilized Chlorine Biocide for Pulp and Paper Corrosion Control

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Solution Overview

Problem

Existing methods for controlling microbial growth in paper making systems using oxidants like chlorine are ineffective in stabilizing chlorine, leading to negative impacts on optical brighteners and dyes, and cause corrosion in metal components, with low yield of stabilized chlorine species.

Innovation Solution

A composition comprising a free chlorine-generating biocide, urea, and an alkali source is used to stabilize chlorine, allowing for controlled release and improved microbial control, reducing corrosion and preserving additives, with the alkali increasing the pH to enhance reaction yield.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If oxidants such as chlorine are used to control microbial growth, then microbial control is improved, but negative effects on optical brighteners and dyes occur

Engineering Contradiction:

Improvemicrobial controlVSAvoidimpact on optical brighteners and dyes

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Urea acts as an intermediary substance that reacts with chlorine to form stabilized chlorine species (chloramines). This mediator allows chlorine to maintain its antimicrobial function while reducing direct contact between free chlorine and sensitive additives like optical brighteners and dyes, thereby resolving the contradiction between effective microbial control and preservation of additives

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical form and release kinetics of chlorine by converting it from free chlorine to stabilized chlorine species through reaction with urea. This parameter change in chlorine's chemical state and release rate allows for sustained microbial control while reducing peak concentrations that would otherwise damage optical brighteners and dyes

Inventive Principle:

Principle #35Parameter changes

2Reliability

If chlorine is used to control microbial growth, then microbial control is improved, but corrosion of metal components occurs

Engineering Contradiction:

Improvemicrobial controlVSAvoidcorrosion of metal components

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Urea serves as a protective intermediary that reacts with chlorine to form less corrosive stabilized chlorine species. This intermediary reaction reduces the direct corrosive interaction between free chlorine and metal components while maintaining the antimicrobial effectiveness through controlled chlorine release

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful corrosive action of free chlorine into a beneficial controlled release mechanism. By reacting chlorine with urea, the potentially harmful free chlorine is transformed into stabilized species that release chlorine gradually, converting a corrosive hazard into a sustained antimicrobial benefit while reducing corrosion

Inventive Principle:

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

3Reliability

If more chlorine-generating agent is added to improve microbial control, then antimicrobial efficacy is improved, but negative impacts on additives and corrosion increase

Engineering Contradiction:

Improveantimicrobial efficacyVSAvoidimpact on additives and corrosion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The stabilized chlorine species formed by reacting chlorine with urea provide continuous, controlled release of active chlorine over time. This continuous action maintains effective antimicrobial concentrations throughout the papermaking process without requiring excessive initial chlorine doses, thereby preventing both additive damage and corrosion that would result from high chlorine concentrations

Inventive Principle:

Principle #20Continuity of useful action

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

The stabilization of chlorine using urea and an alkali source improves microbial control, reduces the need for chlorine, minimizes corrosion, and maintains the effectiveness of additives, achieving higher antimicrobial efficacy and reduced corrosion of metal components.

Implementation Method 1

the reaction yield is significantly improved, to provide stabilized halogen (particularly chlorine) in a treated system. Because of the stabilizing action of urea exerted on a free chlorine-generating biocide agent such as sodium hypochlorite

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

the alkali increasing the pH to enhance reaction yield

Methodology Applied

Scientific EffectpH adjustment:

Implementation Method 3

less chlorine-generating agent is required to be added, because of its stabilized form and consequent more gradual release of chlorine, providing a greater antimicrobial effect

Methodology Applied

Scientific EffectControlled release:

Data Source

PatentEP1976802B1Suppressing microbial growth in pulp and paper

Publication Date: 2016.10.12 NALCO CO

AI summary

A composition for anti-microbial effect in a water system such as a pulp and paper processing line with an aqueous slurry. The composition comprises a free chlorine-generating biocide comprising a chlorine source, urea, and an alkali in a concentration sufficient to provide a pH greater than 10, and typically at least pH 11.