Flash Cooler Direct Contact Condenser Heat Recovery
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Solution Overview
Problem
Conventional heat exchangers are inefficient and costly for recovering heat from high slurry streams in biomass pretreatment processes, facing issues with high viscosity, pressure drops, scaling, and maintenance, and fail to effectively regenerate heat energy, leading to economic unfeasibility.
Innovation Solution
A multi-staged flash cooler-direct contact condenser system is employed to transfer heat directly between incoming and outgoing biomass streams, utilizing flashed vapors to condense onto cold biomass, thereby recovering heat energy efficiently and reducing operational complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional heat exchangers (shell-and-tube, spiral, plate and frame) are used to recover heat from high slurry streams, then heat recovery is attempted, but the system experiences high pressure drops, scaling in tubes, difficulty pumping high viscosity slurry, and requires expensive backup equipment for maintenance
Solution Approach 1:
The invention extracts the heat transfer function from conventional heat exchanger surfaces and implements it through direct contact between vapor and slurry streams. The heat recovery device eliminates the need for tube surfaces by allowing flashed vapor to directly contact and heat the incoming slurry stream, thereby removing the source of scaling and tube fouling problems.
Solution Approach 2:
The system uses the hot slurry stream itself as both the process fluid and the heat transfer medium. The hot slurry is flashed to generate vapor, which then directly heats the incoming cold slurry through condensation, making the system self-sufficient without requiring external cooling fluids or complex heat exchanger surfaces.
2Loss of energy
If conventional heat exchangers are used, then heat exchange surfaces are provided, but they foul and require regular chemical cleaning, producing downtime and requiring expensive backup equipment
Solution Approach 1:
The invention removes the heat exchange surfaces that cause fouling and scaling by implementing direct contact heat transfer. The vapor stream directly contacts the slurry stream without requiring tube surfaces, thereby eliminating the source of maintenance problems and allowing continuous operation without chemical cleaning downtime.
3Loss of energy
If conventional heat exchangers are used with cooling working fluid on the shell side, then heat exchange is achieved, but additional process costs are incurred and heat energy is not regenerated to other process fluids
Solution Approach 1:
The system eliminates the need for external cooling working fluids by using the slurry stream itself as the heat transfer medium. The hot slurry is flashed to generate vapor, which then directly heats the incoming cold slurry, making the system self-sufficient and regenerating heat energy within the process without requiring additional cooling water or external utilities.
Solution Approach 2:
The hot slurry stream serves multiple functions: it is both the process fluid undergoing treatment and the heat source for heating incoming slurry. The flashed vapor serves as both a cooling medium for the hot slurry and a heating medium for the cold slurry, eliminating the need for separate cooling working fluids.
4Loss of energy
If high cellulosic slurry loading is required at the inlet of conventional heat exchangers, then heat recovery potential is maximized, but slurry handling problems occur and pumping becomes difficult due to high viscosity
Solution Approach 1:
The invention segments the slurry stream into two separate streams: a hot slurry stream that is flashed to generate vapor, and a cold slurry stream that is heated by the vapor. This segmentation allows each stream to be handled separately with appropriate viscosity characteristics, avoiding the pumping difficulties associated with high viscosity concentrated slurry in conventional heat exchangers.
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 system effectively recovers heat energy from hot biomass streams, improving process efficiency and reducing energy costs by handling high slurry streams with minimal operating parameters, thus enhancing the economic feasibility of the pretreatment process.
Implementation Method 1
Upon entering the flash cooler, a portion of the liquid flash vaporizes
Implementation Method 2
The flashed vapor contacts the cold biomass causing heat transfer to occur from the flashed vapor to the cold biomass
Implementation Method 3
Absorption of the heat by the cold biomass condenses the vapor onto the surface of the cold biomass
Data Source
AI summary
A method and system for recovering heat from a pretreated hot biomass stream is described. The method and system for heat recovery includes a flash cooler connected to a direct contact condenser. A liquid portion of the hot biomass stream flashes into vapors upon the hot biomass stream entering the flash cooler. The flashed vapors are transferred to the direct contact condenser. The flashed vapors and an incoming cold biomass stream subsequently come into contact with each other in the direct contact condenser, thereby causing heat to be transferred from the hot biomass stream to the cold biomass stream. As the heat transfer occurs, the flashed vapors condense onto the surface of the cold biomass.