Medium Consistency Refining Pulp Process Energy Reduction

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Solution Overview

Problem

Thermomechanical pulping (TMP) processes face inefficiencies in energy consumption and pulp quality due to high energy expenditure in high consistency refining, with limited energy application and excessive fiber damage in low consistency refining, necessitating a more efficient refining method.

Innovation Solution

Implementing a novel TMP process with an initial high consistency refining (HCR) stage followed by one or more medium consistency refining (MCR) stages, which dilutes the pulp to 5-14% consistency, reducing energy consumption and enhancing pulp quality by shifting refining activity from HCR to MCR stages, and using preconditioning treatments to improve fiber development.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high consistency refining is used, then pulp quality and fiber development are improved, but energy consumption increases significantly

Engineering Contradiction:

Improvepulp qualityVSAvoidenergy consumption

Core Design Contradiction:

StrengthVSUse of energy by moving object

Solution Approach 1:

The refining process is divided into multiple stages with different consistency levels. The first stage refines at high consistency (20-50%) for initial fiber development, then dilutes to medium consistency (5-14%) for subsequent refining stages. This segmentation allows energy-efficient refining while maintaining pulp quality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the consistency parameter during the refining process. By diluting the pulp from high consistency to medium consistency between refining stages, the process reduces frictional heat losses and energy consumption while continuing to develop fiber quality.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If low consistency refining is used, then energy consumption is reduced, but fiber damage and shearing increase

Engineering Contradiction:

Improveenergy consumptionVSAvoidfiber strength

Core Design Contradiction:

Use of energy by moving objectVSStrength

Solution Approach 1:

The patent performs preliminary fiber development in a high consistency refiner before diluting to medium consistency. This preliminary action strengthens fibers and reduces their susceptibility to damage in subsequent low-energy refining stages.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The refining process continues across multiple stages with continuous fiber development. By maintaining refining action across HCR and MCR stages, the process achieves cumulative fiber development without excessive shearing that would occur in a single low consistency stage.

Inventive Principle:

Principle #20Continuity of useful action

3Use of energy by moving object

If multiple stages of low consistency refining are used, then energy consumption is reduced, but equipment complexity and number of refiners increase

Engineering Contradiction:

Improveenergy consumptionVSAvoidnumber of refiners

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent combines high consistency and medium consistency refining stages into an integrated process flow. A single MCR unit performs the function that would otherwise require multiple LCR stages, reducing equipment complexity while maintaining energy efficiency.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8734611B2Medium consistency refining method of pulp and system

Publication Date: 2014.05.27 ANDRITZ INC

AI summary

A thermomechanical pulping method including: refining pulp with a high consistency refining stage, and a medium consistency refining stage processing the refined pulp discharge from the high consistency refining stage. Chemical pretreatments for improving pulp quality development during medium consistency refining can be optionally added at the pressurized chip press, fiberizer pre-refining step, primary high consistency refining step, and/or the standpipe feeding the medium consistency refiner.