CO2 Stripper Heat Utilization via Parallel Low-Grade Heating
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Solution Overview
Problem
Existing CO2 capture processes are capital intensive and consume significant amounts of electricity, heat, and cooling water, with inefficiencies in heat utilization and thermal instability of amine solvents.
Innovation Solution
A method and system that efficiently strip CO2 from CO2-rich solutions using partially low-grade waste heat, where the CO2-rich solution is heated by both the CO2-lean solution and external low-grade heat sources in parallel, significantly reducing the reboiler heat duty and potentially eliminating it altogether.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If conventional amine systems use saturated steam for reboiler heating, then CO2 stripping is achieved, but capital expenditure and heat consumption are high
Solution Approach 1:
The patent merges multiple heat sources (CO2-lean solution heat and external low-grade heat sources) to provide the required heating duty, replacing the conventional single high-grade steam source. This combination allows efficient utilization of low-grade heat that would otherwise be wasted, reducing both energy consumption and capital expenditure on steam generation equipment
Solution Approach 2:
The patent changes the temperature parameter of the heating source by utilizing low-grade heat sources with lower temperatures than conventional steam. By accepting lower temperature heating and compensating through increased heat transfer area in the regenerative heat exchangers, the system reduces energy consumption and equipment costs
2Reliability
If amine solvents are used for CO2 capture, then CO2 absorption is effective, but thermal instability limits heat source temperature to less than 150 degrees Celsius
Solution Approach 1:
The patent introduces a regenerative heat exchanger as an intermediary device that transfers heat from the CO2-lean solution to the CO2-rich solution. This intermediary allows heat transfer at controlled temperatures that protect the amine solvent from thermal degradation while still achieving effective CO2 stripping
Solution Approach 2:
The system performs preliminary heating of the CO2-rich solution in the regenerative heat exchanger before it enters the stripper. This preliminary action reduces the temperature requirement for the final stripping process, protecting the amine solvent from excessive temperatures while maintaining absorption effectiveness
3Loss of energy
If CO2-rich solution is heated in counterflow regenerative heat exchanger, then heat recovery is achieved, but evaporation is minimal and reboiler heat duty remains high
Solution Approach 1:
The regenerative heat exchanger is designed to perform multiple functions: heat recovery from CO2-lean solution, preheating of CO2-rich solution, and enabling evaporation of CO2. By making the heat exchanger multi-functional, the system reduces the burden on the reboiler and lowers overall heat duty requirements
Solution Approach 2:
The system uses a composite heating approach combining internal heat recovery (from CO2-lean solution) and external low-grade heat sources. This composite heating strategy enables significant evaporation in the heat exchanger, reducing the reboiler heat duty while maintaining energy 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 achieves high-efficiency CO2 stripping with reduced energy consumption and capital expenditures, allowing for smaller reboilers or their elimination in certain applications, thereby optimizing heat utilization and operational costs.
Implementation Method 1
the CO2-rich solution, collected at the bottom of the absorber, flows through counterflow Regenerative Heat Exchanger (RHE) where the CO2-rich solution is heated by the CO2-lean solution from the bottom of the stripper
Implementation Method 2
the desired specie, such as CO2 in the CO2—NH3—H2O system, starts evaporating at relatively low temperature including in the regenerative heat exchanger
Data Source
AI summary
In stripping volatile species in multi-species solutions. e.g. a CO2-rich solution in a CO2—NH3—H2O and CO2—H2S—NH3—H2O, evaporation starts at relatively low temperature depending on the pressure of the system. As CO2 evaporates the boiling temperature of the solution increases. In current CO2 stripper systems, all the external heat is provided at the high temperature in the reboiler. In this invention, external heat is provided to the solution at lower than the reboiler temperature through heat exchangers constructed in parallel to the regenerative heat exchanger. As a result, a much smaller heat input is required at the high temperature of the reboiler and, depending on the quality of the heat source, the reboiler may even be eliminated altogether. This allows for efficient use of various heat sources such as syngas, flue gas and hot oil from thermal solar collectors down to a lot lower temperature than achieved in a conventional system.