Roll Press Shear for Cellulosic Feedstock Pretreatment
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Solution Overview
Problem
Current methods for converting cellulose to ethanol face challenges such as high power consumption, equipment costs, and inefficiencies in particle size reduction and acid usage, particularly when processing feedstocks with high moisture content or alkalinity, which hinder the commercial viability of cellulosic ethanol production.
Innovation Solution
A wet processing method involving the use of roll presses with circumferential v-shaped grooves to shear and reduce the particle size of cellulose-containing feedstocks, followed by dilute acid pretreatment, which reduces acid requirements and increases xylose yield, allowing for more efficient conversion to ethanol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If dry processing methods (grinding, milling, crushing) are used to reduce particle size, then particle size reduction is achieved, but power consumption increases significantly
Solution Approach 1:
The patent employs a wet grinding approach using a grinder immersed in water to reduce particle size. The hydraulic environment allows for efficient size reduction with lower power consumption compared to dry mechanical methods, as the water facilitates particle breakdown and transport through the grinding mechanism.
Solution Approach 2:
The invention changes the processing parameters by transitioning from dry to wet conditions, adjusting moisture content from 0% to approximately 20-30%. This parameter change enables more efficient particle size reduction with reduced power requirements, as the wet environment reduces friction and allows for gentler, more energy-efficient grinding.
2Length of moving object
If wet grinding processes are used to reduce particle size, then particle size reduction is achieved with lower power consumption, but the produced material becomes very dilute and costly to handle
Solution Approach 1:
The patent applies localized water addition rather than complete wetting. Water is added selectively to the grinding zone to facilitate particle size reduction, while the bulk material maintains higher concentration. This local quality approach allows for efficient grinding without producing excessively dilute material that would be costly to handle.
Solution Approach 2:
The invention uses partial wetting rather than complete saturation. By adding water only to the extent necessary for effective grinding (approximately 20-30% moisture content), the process achieves particle size reduction without excessive dilution. This partial action avoids the need to handle overly dilute materials while still providing the hydraulic benefits for efficient grinding.
3Ease of operation
If feedstock with high moisture content (20% or higher) is processed, then handling issues are avoided, but milling equipment becomes blind and size reduction is not sustainable
Solution Approach 1:
The patent applies preliminary size reduction through wet grinding before the material enters milling equipment. By first reducing particle size in the wet grinder (achieving 80% of particles passing through a 2mm sieve), the subsequent milling process operates more efficiently without becoming blind, as the pre-ground material requires less force to process.
Solution Approach 2:
The wet grinding process acts as an intermediary step between receiving high-moisture feedstock and the milling process. It prepares the material by reducing particle size and achieving optimal moisture content (20-30%), creating intermediate material that is both easy to handle and suitable for efficient milling without equipment blind spots.
4Productivity
If acid hydrolysis process is used to convert cellulose to glucose, then cellulose conversion is achieved, but high acid usage increases process cost
Solution Approach 1:
The patent modifies the acid hydrolysis parameters by conducting the process at elevated temperatures (160-280°C) with controlled acid concentration. These parameter changes optimize the conversion efficiency while minimizing acid consumption, as the higher temperature accelerates the hydrolysis reaction rate, allowing for reduced acid dosage while maintaining productivity.
Solution Approach 2:
The invention implements a continuous acid hydrolysis process where the acid catalyst is recovered and reused. The continuous operation allows for consistent conversion conditions to be maintained, improving cellulose breakdown efficiency over time while reducing net acid consumption through recycling and reuse of the acid catalyst throughout the process.
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
The process significantly reduces power input and equipment costs, enables efficient particle size reduction, and decreases acid usage, making the production of ethanol from cellulose-containing feedstocks more economically viable and environmentally friendly.
Implementation Method 1
pressing the wet feedstock through one roll press or a series of roll presses to remove at least a portion of water and soluble substances from the wet feedstock and to shear the wet feedstock
Implementation Method 2
carrying out dilute acid pretreatment of the slurried feedstock, at a temperature of about 160° C. to about 280° C.
Implementation Method 3
carrying out dilute acid pretreatment of the slurried feedstock, at a temperature of about 160° C. to about 280° C.
Data Source
AI summary
A process for producing ethanol from a pretreated feedstock is provided. The feedstock is selected from grasses, cereal straws, stover, and combinations thereof, and least about 80% of the feedstock has a particle length of between about 2 cm and about 40 cm. This process comprises wetting the feedstock in liquid, pressing the wet feedstock through one roll press or a series of roll presses to remove at least a portion of water and soluble substances from the wetted feedstock and to shear the feedstock to produce feedstock particles of a size suitable for pumping at a solids concentration of about 8% to about 20% when slurried. At least one roll press, or at least one roll press in the series of roll presses comprises rolls with circumferential v-shaped grooves. The pressed feedstock particles are slurried to produce a slurried feedstock having a consistency of between about 8% and about 20%, and the slurried feedstock pumped into a pretreatment reactor. Dilute acid pretreatment of the slurried feedstock is carried out at a temperature of 160° C. to 280° C.