Semichemical Pulping Process for High-Yield Biomass Conversion
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Solution Overview
Problem
Current semichemical pulping processes are costly due to high washing and chemical recovery costs, with inefficiencies in energy recovery and pulp yield, which affects the production of strong and durable paper products.
Innovation Solution
A process involving the digestion of lignocellulosic biomass with steam and/or hot water to generate an intermediate pulp and liquid phase, followed by mechanical refining, which eliminates the need for separate washing and chemical recovery, retaining lignin and cellulose for improved pulp yield and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical pulping methods are used to delignify biomass, then cellulose can be released, but about half of the original material dissolves and must be burned to recover chemicals, increasing cost and energy consumption
Solution Approach 1:
The patent extracts hemicelluloses from the pulp using a specific solvent system (alkyl phenol and/or alkyl alcohol) after the pulping process. This extraction is performed to remove unwanted components that would otherwise remain in the pulp, improving pulp quality and yield without requiring energy-intensive burning processes to recover chemicals.
Solution Approach 2:
The patent employs specific pulping conditions including controlled temperature (100-200°C), pH levels (4-10), and residence time (1-60 minutes) to optimize the delignification process. These parameter changes enable efficient cellulose release while minimizing material dissolution, reducing the need for energy-consuming chemical recovery operations.
2Quantity of substance
If mechanical pulping is used to grind wood, then nearly 100% yield is achieved, but large amounts of electricity are required (1500 to 2500 kWh per ton of wood)
Solution Approach 1:
The patent applies a pre-steaming step before mechanical refining to soften the wood chips. This preliminary thermal treatment reduces the mechanical force required during disk refining, thereby decreasing electricity consumption while maintaining high pulp yield. The softening of wood fibers before mechanical processing is key to reducing energy requirements.
Solution Approach 2:
The patent replaces intensive mechanical grinding with a combination of thermal softening (steaming) and mild mechanical refining. This substitution reduces the mechanical energy input required for pulping while achieving similar or better pulp yield, directly addressing the high electricity consumption issue.
3Strength
If hemicelluloses are retained in the pulp, then bonding strength increases, but chemical consumption increases during pulping and bleaching
Solution Approach 1:
The patent selectively extracts hemicelluloses using a solvent system (alkyl phenol and/or alkyl alcohol) after pulping. This extraction removes excess hemicelluloses that would otherwise require chemical treatment during bleaching, reducing chemical consumption while maintaining sufficient bonding strength through controlled retention of essential hemicellulose components.
Solution Approach 2:
The patent optimizes pulping parameters (pH, temperature, time) to control hemicellulose retention at levels that provide adequate bonding strength without excessive chemical consumption during subsequent bleaching. The controlled delignification process preserves essential hemicellulose-bonding components while removing excess that would increase chemical requirements.
4Loss of substance
If washing stages are used to remove dissolved solids, then 70-95% of dissolved solids can be removed, but the digester and washers represent approximately half of the pulp plant cost
Solution Approach 1:
The patent uses a selective extraction process with solvent systems (alkyl phenol and/or alkyl alcohol) to remove dissolved solids and unwanted compounds. This extraction method achieves effective removal of dissolved solids (70-95%) while using simpler, less expensive equipment compared to traditional multi-stage washing systems, reducing capital costs.
Solution Approach 2:
The patent employs a versatile extraction solvent system that performs multiple functions: removing dissolved solids, separating unwanted compounds, and concentrating desirable components. This multi-functional approach eliminates the need for separate dedicated washing stages, reducing equipment complexity and plant cost while achieving effective dissolved solids removal.
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 costs, increases pulp yield, and maintains the strength of paper products by minimizing hemicellulose extraction and eliminating the need for chemical recovery, while enhancing the energy efficiency of the pulping process.
Implementation Method 1
digesting the biomass in the presence of steam and/or hot water to generate an intermediate pulp material and a liquid phase, wherein the liquid phase contains extracted hemicelluloses
Implementation Method 2
mechanically refining the intermediate pulp material, to generate a refined pulp material
Data Source
AI summary
An improved semichemical pulping process is disclosed to reduce washing costs and recovery process costs, while producing equivalent pulp and paper products. In some variations, the invention provides a process for producing a paper product from biomass, comprising: digesting lignocellulosic biomass in the presence of steam and/or hot water to generate an intermediate pulp material and a liquid phase containing extracted hemicelluloses; mechanically refining the intermediate pulp material, to generate a refined pulp material; and introducing the refined pulp material, the liquid phase, and optionally a separate solid material to a paper machine, to produce a paper product. The process optionally employs no washing step. When the liquid phase is washed from the intermediate pulp material or the refined pulp material using an aqueous wash solution, the wash filtrate may be introduced directly or indirectly to the paper machine.