Flash Cooling Pretreated Biomass Slurry
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Solution Overview
Problem
The challenge in the production of second-generation biofuels from lignocellulosic biomass lies in efficiently cooling high consistency slurries post-pretreatment, as conventional methods require large, expensive equipment and excessive water usage, leading to increased energy costs and operational complexities.
Innovation Solution
A method involving the mixing of pretreated biomass with a cooling liquid to reduce viscosity, followed by solid-liquid separation, where the liquid stream is recycled and used to cool the biomass, thereby reducing the need for large equipment and water, and facilitating the use of standard pumps and piping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling methods are used for high consistency slurries, then cooling effectiveness is improved, but equipment size and cost increase significantly
Solution Approach 1:
The patent introduces a two-stage cooling approach where flash cooling acts as an intermediary step between pretreatment and final cooling. The slurry first undergoes rapid flash cooling to reduce temperature significantly, then proceeds to a second cooling stage. This intermediary flash cooling step enables the overall system to achieve effective cooling without requiring a single oversized heat exchanger.
2Temperature
If conventional cooling methods are used for high consistency slurries, then cooling effectiveness is improved, but water usage increases excessively
Solution Approach 1:
The patent utilizes flash cooling where high consistency slurry undergoes rapid phase change and temperature reduction. The slurry is flashed from pressurized conditions to atmospheric or reduced pressure, causing immediate cooling through adiabatic expansion and partial vaporization. This phase transition-based cooling achieves significant temperature reduction with minimal water addition, as the cooling energy comes from the slurry's own pressure energy rather than large volumes of cooling water.
3Temperature
If high consistency slurry is cooled using conventional methods, then cooling is achieved, but energy consumption increases
Solution Approach 1:
The patent converts the high pressure energy present in the pretreated slurry into useful cooling energy through flash cooling. The pressurized slurry from the pretreatment reactor is directly flashed to lower pressure without intermediate pressure reduction steps, transforming the pressure energy into thermal energy reduction. This approach turns what would otherwise be wasted pressure energy into the driving force for cooling, significantly reducing external energy input requirements.
4Productivity
If high consistency slurry is processed, then pretreatment effectiveness is improved, but pumping and handling become more difficult
Solution Approach 1:
The patent performs flash cooling as a preliminary action immediately after pretreatment and before the slurry enters pumping and handling systems. By reducing the temperature and adjusting the consistency of the slurry through flash cooling first, the subsequent pumping and handling operations become significantly easier. The slurry becomes less viscous and more pumpable after the flash cooling step, eliminating the need for specialized high-consistency pumping equipment.
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 allows for efficient cooling of high consistency slurries, reducing energy consumption and operational costs, while enabling the use of standard equipment and minimizing water usage, thus enhancing the overall efficiency of the biofuel production process.
Implementation Method 1
mixing the discharged pretreated biomass with a cooling liquid to form a slurry
Implementation Method 2
pumping the slurry to a solid-liquid separator, said solid-liquid separator for providing a first stream comprising a liquid component of the slurry and a second other stream comprising a solid component of the slurry
Data Source
AI summary
Discharging pretreated biomass from a pretreatment reactor and mixing the discharged pretreated biomass with a cooling liquid in a vessel provides a cooled slurry having a consistency that is less than about 12 wt %. Since the consistency is relatively low, the cooled slurry may be pumped to a higher elevation using standard pumping equipment. At the higher elevation, the cooled slurry may be separated into a first stream comprising a liquid component of the slurry and a second other stream comprising a solid component of the slurry (e.g., having a consistency between about 15 wt % and 40 about wt %). The solid component may be fed to an inlet of a hydrolysis reactor, while the liquid component may be fed to a cooling system that provides a cooled stream. The cooled stream may then be cycled back to the vessel.