Staged Heat Exchanger Networks for Hydrothermal Liquefaction Slurries
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Solution Overview
Problem
Existing hydrothermal liquefaction systems face challenges in efficiently pressurizing and heating biomass slurries to high temperatures and pressures due to high viscosity, requiring robust and expensive pumps and heat exchangers that suffer from poor thermal efficiency and significant pressure drops.
Innovation Solution
The system employs multiple discrete pressurization and heating steps to manage changes in biomass slurry viscosity, using heat exchanger networks with series, parallel, and series-parallel arrangements to reduce viscosity and pressure drops, and incorporates a heat transfer liquid circuit for heat recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If robust pumps and heat exchangers are used to handle high viscosity biomass slurry, then the system can maintain required pressure and temperature, but the system cost increases and thermal efficiency decreases
Solution Approach 1:
The heating process is divided into multiple stages with intermediate pumping steps. The slurry is heated to an intermediate temperature, pumped to high pressure, then heated to the final temperature. This segmentation allows each heat exchanger to operate at lower pressure differentials, improving thermal efficiency while maintaining the required final pressure and temperature conditions.
Solution Approach 2:
The slurry is preheated to an intermediate temperature before being pressurized to the final operating pressure. This preliminary heating reduces the viscosity of the slurry before high-pressure pumping, making the subsequent pressurization more efficient and reducing the energy loss in the pumping process.
2Device complexity
If single-stage pressurization and heating is used, then the system complexity is reduced, but pumping efficiency and thermal efficiency deteriorate due to high viscosity
Solution Approach 1:
The system uses multiple heat exchangers arranged in series with intermediate pumping stages. This segmentation allows the slurry to be heated in increments, reducing viscosity at each stage and improving the overall efficiency of both pumping and heating operations, while maintaining a manageable system structure.
Solution Approach 2:
The system changes the temperature parameter incrementally through multiple heating stages rather than attempting single-stage heating. This parameter change approach reduces slurry viscosity progressively, enabling more efficient pumping and heating operations throughout the process.
3Stress or pressure
If heat exchangers operate at high pressure differentials, then the required pressure is achieved, but pressure drops and thermal efficiency are significantly reduced
Solution Approach 1:
The high pressure differential required for hydrothermal liquefaction is achieved through multiple pumping stages rather than a single high-differential pump. Each pump operates at a lower differential, reducing pressure drops across heat exchangers and improving thermal efficiency while achieving the required final pressure.
Solution Approach 2:
The slurry is preheated to an intermediate temperature before the final pressurization stage. This preliminary heating reduces viscosity, allowing the subsequent high-pressure pumping to occur more efficiently with reduced pressure losses, thereby improving overall thermal efficiency.
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 enhances pumping and thermal efficiency, reduces system costs, and improves heat transfer efficiency by handling biomass slurries at specific temperature, pressure, and viscosity ranges, resulting in more efficient biocrude production.
Implementation Method 1
A first heat exchanger network downstream of the first pump(s) can heat the incoming feed stream in a series of increments to a first temperature. A second heat exchanger network downstream of the second pump(s) can heat the feed stream in a series of increments to a second temperature.
Implementation Method 2
one or a plurality of first pumps that pressurize the incoming slurry stream to a first, intermediate pressure. One or a plurality of second pumps downstream of the first heat exchanger network can pressurize the feed stream to a second pressure.
Implementation Method 3
A heat transfer liquid circuit can heat the incoming feed stream, either by heat recovery from the product stream or with heat from other sources such as oil-fired heaters.
Data Source
AI summary
A hydrothermal liquefaction (HTL) system has a biomass slurry flow path with a first pump and a first heat exchanger network downstream of the first pump. The first heat exchanger network includes plurality of heat exchangers in a parallel, series, and/or series-parallel flow arrangement. The biomass slurry flow path extends through cold flow sides of the heat exchangers of the first heat exchanger network. The biomass slurry flow path includes a second pump downstream of the first heat exchanger network, and a second heat exchanger network downstream of the second pump. The biomass slurry flow path extends through cold flow sides of the heat exchangers of the second heat exchanger network. A hydrothermal liquefaction (HTL) reactor is downstream of the second heat exchanger network. Heat transfer liquid in a heat transfer liquid circuit flows through hot flow sides of the heat exchangers of the second heat exchanger network.