Halogen Stabilizer Blends for Biocide Stability in Pulp Water
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Solution Overview
Problem
Biological activity in process streams, particularly in papermaking processes, is challenging due to the instability of oxidant biocides, leading to ineffective microbial control, corrosion of equipment, and adverse effects on paper quality, with existing stabilization methods being either ineffective or too rigid in dosage requirements.
Innovation Solution
A composition comprising a halogen source, urea, and a sulfur-bearing stabilizer, such as sulfamic acid, with a molar ratio of halogen to sulfur exceeding 2:1, is used to stabilize biocides, maintaining effectiveness while minimizing chlorine usage and avoiding adverse effects on paper additives and equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxidant biocides are introduced into process water systems to kill microorganisms, then microbial control effectiveness is improved, but the biocides are not naturally stable and oxidize rapidly, losing effectiveness over time
Solution Approach 1:
The patent applies preliminary action by pre-stabilizing the oxidant biocide with a stabilizer compound before introduction into the process water system. This preliminary stabilization prevents rapid oxidation and maintains biocide effectiveness over extended periods, allowing the biocide to remain active throughout the intended treatment duration without rapid degradation
Solution Approach 2:
The patent uses a stabilizer compound as an intermediary substance that mediates between the oxidant biocide and the process water environment. This intermediary protects the biocide from premature oxidation while still allowing it to function as intended, bridging the gap between biocide introduction and its intended microbial killing action
2Reliability
If sufficient levels of oxidant biocide are maintained to combat periodic spikes in biological activity, then microbial control is improved, but the biocide causes adverse effects on paper brighteners, dyes, and other additives
Solution Approach 1:
The patent applies parameter changes by modifying the chemical stability parameter of the biocide through stabilizer addition. This changes the biocide's oxidation rate and persistence in the system, allowing it to maintain effectiveness longer without requiring repeated high-level applications that would harm paper additives and equipment
Solution Approach 2:
The patent enables periodic action by creating a biocide program that can operate at lower, more stable levels over extended periods. The stabilized biocide provides continuous baseline protection while maintaining the capability to respond to periodic biological activity spikes without requiring aggressive dosing that would damage paper quality
3Reliability
If repeated applications of oxidant biocides are made to maintain microbial control, then biocide effectiveness is improved, but corrosion of papermaking machinery increases
Solution Approach 1:
The patent applies preliminary action by pre-stabilizing the biocide to reduce its aggressive oxidative properties. This preliminary modification allows the biocide to be introduced at lower concentrations and applied less frequently, reducing cumulative exposure of equipment to corrosive oxidizing conditions while maintaining microbial control effectiveness
4Duration of action of stationary object
If halogen stabilizer is added to stabilize oxidant biocides, then biocide persistence is improved, but the stabilizer is consumed by sulfite post bleaching/processing of recycled fibers, reducing available chlorine
Solution Approach 1:
The patent applies parameter changes by optimizing the halogen-to-stabilizer molar ratio to exceed 2:1. This parameter adjustment ensures that sufficient halogen remains available for biocidal action even after stabilizer consumption by sulfite, maintaining both persistence and adequate chlorine levels simultaneously
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 composition provides sustained microbial control with reduced chlorine usage, maintaining biocide efficacy and compatibility with papermaking processes, reducing equipment corrosion and preserving paper quality.
Implementation Method 1
A composition comprising a halogen source, urea, and a sulfur-bearing stabilizer, such as sulfamic acid, with a molar ratio of halogen to sulfur exceeding 2:1, is used to stabilize biocides
Implementation Method 2
oxidant biocides are not naturally stable and they tend to oxidize rapidly and over time lose their effectiveness
Implementation Method 3
Oxidant biocides such as peroxide acid and halogen chemicals like sodium hypochlorite have been widely used in the pulp and paper industry. These oxidant biocides are highly effective at immediately killing large numbers of microorganisms
Data Source
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AI summary
A composition and methods of its use, the composition comprising: a halogen source, urea, and an additional halogen stabilizer excluding urea, optionally an alkali in a concentration sufficient to provide said composition with a pH of greater than 10; and optionally excluding a stabilized bromine compound from said composition is disclosed. Additionally, a method for reducing biological activity in a process stream is disclosed. The method comprises: providing a composition to a process stream, wherein said composition contains: a halogen, urea, and an additional halogen stabilizer excluding urea, optionally an alkali in a concentration sufficient to provide said composition with a pH of greater than 10; and optionally excluding a stabilized bromine compound from said composition. The invention is also directed to compositions and methods of their use as effective biocidal agents for water streams. The composition comprises a halogen source, halogen stabilizers containing a sulfur bearing species and ammonium salts/urea, and an alkali. The sulfur bearing species includes sulfamic acid or its salt equivalent. The ratio between nitrogen mixture of sulfur bearing species and ammonium salts or urea can be optimized at any rate. By having optimized mixing ratio of halogen to stabilizer and that of ammonium salts to sulfamic acid or sulfamate, a synergistic effect occurs which both increases the efficacy of the composition as a biocide and it avoids adverse impacts on other chemicals that are present in the water stream (such as paper additives in pulp and papermaking water streams). Best of all the composition is easy to form and easy to introduce into a water stream of concern. Its introduction can be as simple as mixing two containers of reagent prior to introduction to the water process stream.