Thermomechanical Pulp Refining Energy Reduction
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Solution Overview
Problem
The thermomechanical and chemi-thermomechanical pulp refining processes require significant energy due to high frictional heat losses, with less than 10-15% of electric energy directly applied to refining, necessitating a reduction in specific energy demand to enhance energy efficiency.
Innovation Solution
A process involving high consistency refining followed by alkaline peroxide treatment and subsequent low consistency refining, with optional chelating agent application and latency removal, to reduce energy consumption and improve pulp quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high consistency refining is used to process pulp, then pulp processing capacity is improved, but energy consumption increases due to high frictional heat losses
Solution Approach 1:
The refining process is segmented into two distinct stages: high consistency refining for capacity and low consistency refining for energy efficiency. This segmentation allows each stage to operate under optimized conditions, with the second stage consuming significantly less energy while maintaining pulp quality.
Solution Approach 2:
The process changes the consistency parameter of the pulp suspension between stages, transitioning from high consistency (20% or more) to low consistency. This parameter change enables the use of pumps instead of pressurized blowlines, reducing the energy required for transport and processing.
2Use of energy by moving object
If low consistency refining is added after high consistency refining, then energy efficiency is improved, but process complexity increases
Solution Approach 1:
The low consistency refining stage is merged with the existing high consistency refining line, utilizing the same refiner equipment for both stages. This merging approach avoids adding separate dedicated equipment, thereby limiting the increase in process complexity while achieving energy savings.
3Strength
If alkaline peroxide treatment is applied to pulp, then brightness and tensile strength are improved, but chemical processing steps increase
Solution Approach 1:
The alkaline peroxide treatment serves multiple functions simultaneously: it brightens the pulp, enhances tensile strength, and can be integrated with the refining process. This multi-functionality reduces the need for separate chemical processing steps, as one treatment achieves multiple desired outcomes.
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 reduces specific energy demand by 10-30% and achieves desired pulp quality with increased tensile strength, brightness, and fiber flexibility, diverting energy from high friction losses to low consistency refining steps.
Implementation Method 1
treating the stabilized or first pulp with an alkaline-peroxide liquor to produce a treated pulp
Implementation Method 2
Mechanically refining pulp at a high consistency requires a large amount of energy that is expended primarily in frictional heat losses associated with viscoelastic deformations of the pulp in the refining zone
Implementation Method 3
frictional heat losses associated with viscoelastic deformations of the pulp in the refining zone
Data Source
AI summary
A method for producing thermomechanical or chemi-thermomechanical pulp is provided. The process is characterized as having a reduced specific energy demand during refining. The process involves processing a pretreated wood material using one or more high consistency refining steps to produce a first pulp, optionally applying a chelating agent to the first pulp during HC refining to produce a stabilized pulp and treating the first or stabilized pulp with an alkaline-peroxide liquor to produce a treated pulp. The treated pulp is then processed by one or more second low consistency refining steps. Alternatively, the first pulp or stabilized pulp may be divided into a primary and secondary stream. The primary stream is treated with alkaline-peroxide liquor to produce a treated pulp. The secondary stream is processed using a secondary HC refining step to produce a partially refined pulp, and removing latency of the partially refined pulp and the treated pulp is removed in a common location. The treated pulp and the partially treated pulp is processed by one or more than one second low consistency refining step to produce a final pulp. The methods utilize less energy when compared with a method for producing pulp that requires both primary and secondary high consistency refining stages.