BCTMP Filtrate Recycling Segmentation
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Solution Overview
Problem
Conventional countercurrent filtrate recycling in bleached chemical thermomechanical pulp (BCTMP) processes faces inefficiencies due to accumulation of contaminants, high chemical consumption, and operational issues like pH buffering and scale formation, which affect pulp brightness and bleaching efficiency.
Innovation Solution
A process involving multiple recycled filtrate loops for bleaching and dewatering stages, where filtrates are circulated to control fluid levels and dilute residual bleaching agents, reducing contaminant accumulation and optimizing bleaching chemical usage by recycling and reusing filtrates strategically across different stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional countercurrent filtrate recycling is used in BCTMP processes, then filtrate is recycled to maintain fluid levels, but contaminant accumulation occurs and chemical consumption increases
Solution Approach 1:
The patent divides the filtrate recycling system into multiple separate loops (first recycled filtrate loop and second recycled filtrate loop) with different functions. The first loop handles filtrate from the first dewatering stage while the second loop handles filtrate from the second dewatering stage, allowing selective recycling and preventing contaminant accumulation by targeting specific contaminant sources to appropriate disposal or treatment locations.
Solution Approach 2:
The patent extracts and removes filtrate streams at specific points where contaminant accumulation becomes problematic. By taking out filtrate from the second dewatering stage and directing it to discharge or treatment rather than recycling it back to the first dewatering stage, the system prevents excessive contaminant buildup while maintaining adequate fluid levels through controlled recycling of cleaner filtrate streams.
2Stability of the object's composition
If conventional countercurrent filtrate recycling is used, then fluid levels are maintained, but pH buffering and scale formation occur
Solution Approach 1:
The patent segments the filtrate recycling into distinct loops that handle different stages of dewatering separately. This allows independent control of pH and scaling issues in each loop, enabling targeted treatment of filtrate streams to prevent pH buffering and scale formation while maintaining overall fluid level stability through coordinated recycling.
3Productivity
If conventional countercurrent filtrate recycling is used, then bleaching process continues, but bleaching efficiency decreases due to contaminant accumulation
Solution Approach 1:
The patent segments the bleaching process into distinct stages with separate dewatering and filtrate recycling loops. The first dewatering stage serves the first bleaching stage while the second dewatering stage serves the second bleaching stage, allowing each stage to operate with optimized filtrate quality and preventing contaminant accumulation from affecting overall bleaching efficiency.
Solution Approach 2:
The patent extracts and discharges filtrate from the second dewatering stage where contaminant accumulation is most severe, preventing these contaminants from returning to earlier bleaching stages. This maintains bleaching efficiency by removing the most contaminated stream while preserving the continuity of the overall bleaching process through controlled recycling of cleaner filtrate.
Data Source
AI summary
A process for making bleached pulp comprises contacting an unbleached pulp mixture with a first recycled filtrate obtained from a first location (3) of a first recycled filtrate loop, to obtain a first pulp mixture having a first consistency; bleaching the first pulp mixture, to obtain a first bleached pulp mixture; pressing or dewatering the first bleached pulp mixture, to obtain a first pressed bleached pulp mixture and a second filtrate; sending at least a portion of the second filtrate to a second location (5) of the first recycled filtrate loop, wherein the second location (5) is downstream of and in fluid communication with the first location (3); contacting the first pressed bleached pulp mixture with a second recycled filtrate obtained from a third location (6) of the first recycled filtrate loop, to obtain a second pulp mixture having a second consistency, wherein the second consistency is greater than the first consistency, and wherein the third location (6) is downstream of and in fluid communication with the second location (5); bleaching the second pulp mixture, to obtain a second bleached pulp mixture; pressing or dewatering the second bleached pulp mixture, to obtain a second pressed bleached pulp mixture and a third filtrate; sending at least a portion of the third filtrate to a fourth location (8) of the first recycled filtrate loop, wherein the fourth location (8) is downstream of and in fluid communication with the third location (6); and recycling at least a portion of the third filtrate in the first recycled filtrate loop to the first location (3); to obtain the bleached pulp.