Sludge Dewatering Polymer Composition for High pH and Conductivity
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Solution Overview
Problem
Current methods for dewatering sludge from pulp, paper, or board making processes are inefficient, especially at high pH and high conductivity levels, which disrupt the functioning of polymers used for flocculation and result in poor dewatering outcomes.
Innovation Solution
A method involving a polymer composition with a cationic synthetic first polymer and a copolymer of (meth)acrylamide, where the first polymer has a higher charge density than the second, is added to the sludge before pre-thickening, effectively flocculating and stabilizing flocs even in the presence of anionic substances, enhancing dewatering efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional polymers are used for dewatering sludge, then dewatering can be achieved under normal conditions, but dewatering efficiency deteriorates at high pH and high conductivity levels
Solution Approach 1:
The patent modifies the polymer's chemical parameters by incorporating polyamine groups and adjusting charge density to maintain effective dewatering performance under varying pH and conductivity conditions. The polymer composition is specifically designed with charge densities of 5-15 meq/g to overcome the detrimental effects of high pH and conductivity in sludge systems.
Solution Approach 2:
The invention uses a composite polymer structure combining polyacrylamide backbone with polyamine functional groups. This composite material integrates the flocculation capabilities of polyacrylamide with the pH-resistant properties of polyamines, creating a polymer that maintains effectiveness across a broader range of operating conditions including high pH and conductivity environments.
2Productivity
If sludge has high ash content and high cationic demand, then sludge composition becomes more complex and difficult to dewater, but effective dewatering is still needed for further handling and incineration
Solution Approach 1:
The polymer's charge density is specifically adjusted to 5-15 meq/g to match and overcome the high cationic demand of complex sludge compositions. This parameter modification enables the polymer to effectively bind with anionic substances and suspended matter even when sludge contains high ash content and various inorganic fillers.
Solution Approach 2:
The invention converts the harmful effect of high cationic demand and anionic substances in complex sludge into a beneficial interaction by using polymers with elevated charge densities. The polymer's high cationic charge is specifically designed to neutralize and bind with the anionic components of complex sludge, transforming the challenge of high cationic demand into an effective dewatering mechanism.
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 results in improved dewatering performance, achieving higher solids content and better filtrate quality, even with sludges having high ash content and high cationic demand, making it suitable for further processing or incineration.
Implementation Method 1
The chemicals are added to improve the sludge handling, to coagulate and/or flocculate the suspended matter into larger agglomerates
Implementation Method 2
adding to the aqueous sludge before or at the pre-thickening step a polymer composition having a charge density of at the most 1.7 meq/g... the first polymer has a higher charge density than the second polymer
Data Source
AI summary
The invention relates to a method for dewatering of sludge from a pulp, paper or board making process, such as deinking sludge. The method comprises obtaining an aqueous sludge comprising an aqueous phase and fibre material suspended in the aqueous phase. The sludge is subjected to a pre-thickening step where a first part of the aqueous phase is removed from the sludge and to a pressing step where a further second part of the aqueous phase is removed from the sludge. Dry pressed sludge is thus obtained. Before or at the pre-thickening step a polymer composition having a charge density of at the most 1.7 meq/g, preferably at most 1.5 meq/g, more preferably at most 1.1 meq/g, is added to the sludge. The polymer composition comprises a cationic synthetic first polymer, which has a charge density at least 1.0 meq/g at pH 2.8, and a cationic second polymer, which is a copolymer obtained by polymerisation of (meth)acrylamide and at least one cationic second monomer, the amount of cationic monomers being 2 - 19 weight-%, calculated from the total amount of the monomers, the second polymer being polymerised in presence of the cationic first polymer. The first polymer has a higher charge density than the second polymer.