CO2 Absorbent Regeneration via Flash Gas Compression and Heat Recovery
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Solution Overview
Problem
Current CO2 capture processes are energy-intensive and costly due to high demand for medium temperature heat energy, reducing the efficiency and profitability of thermoelectric power plants, and existing heat exchanger designs are inefficient in optimizing heat utilization.
Innovation Solution
A method that involves introducing a stream of rich absorbent into a regeneration column countercurrent with steam, flashing the lean absorbent to separate a gas phase for compression and return to the column, and heat exchanging the gas phase against reboiler condensate to reduce energy consumption and utilize low-temperature heat sources, thereby reducing the reboiler duty and enhancing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steam is used to heat lean absorbent in the reboiler to generate steam for the regeneration column, then the regeneration process can be maintained, but the energy consumption and operating cost increase significantly
Solution Approach 1:
The system uses the rich absorbent stream itself as the heat source to generate steam for regeneration. The rich absorbent enters the regeneration column and releases heat during the regeneration process, which automatically generates the steam needed for continuous operation without external energy input. This self-service mechanism eliminates the need for the reboiler and its associated high energy consumption.
Solution Approach 2:
The invention converts the thermal energy that would otherwise be wasted in the rich absorbent stream into useful steam for the regeneration process. By utilizing the heat content of the rich absorbent to generate steam, the system transforms what could be considered a waste stream into a valuable energy source, eliminating the need for external heating and significantly reducing operating costs.
2Quantity of substance
If the gas phase from flash tank is compressed and returned to regeneration column, then steam supply is increased, but compression energy is required
Solution Approach 1:
The system changes the pressure parameter of the gas phase from the flash tank by compressing it to a higher pressure suitable for injection into the regeneration column. This parameter change enables the compressed gas to be effectively utilized as steam supply in the regeneration process, increasing the quantity of steam available while the compression energy required is offset by the elimination of reboiler energy consumption.
3Temperature
If heat exchanger is used to cool lean absorbent with incoming rich absorbent, then lean absorbent temperature is reduced, but heat exchange efficiency is limited by temperature difference
Solution Approach 1:
The system performs preliminary cooling of the lean absorbent stream by heat exchange with the incoming rich absorbent before the lean absorbent enters the regeneration column. This preliminary action reduces the temperature of the lean absorbent, preparing it for more efficient subsequent processing and reducing the overall energy demand of the regeneration 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
This approach reduces the energy required for CO2 capture by utilizing low-temperature heat sources, lowering the temperature of the regenerated absorbent, and increasing the amount of steam introduced into the regenerator column at a lower energy cost, making the process more energy-efficient and cost-effective.
Implementation Method 1
a stream of rich absorbent is introduced into a regeneration column in which the absorbent flows downwards and countercurrent with steam
Implementation Method 2
released CO2 and steam are withdrawn from the top of the column
Implementation Method 3
the lean absorbent is flashed over a flash valve and separated in a flash tank into a gas phase, that is compressed and returned into the regenerator column, and a liquid phase
Implementation Method 4
the gas phase is heat exchanged against a condensate from the reboiler after leaving the flash valve and before the gas is compressed
Data Source
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AI summary
A method for regeneration of a rich absorbent having absorbed CO2, to give a regenerated, or lean absorbent, and CO2, is described. The rich absorbent is brought in countercurrent flow with steam at least partly generated by heating lean absorbent in a reboiler at the base of the regeneration column, where released CO2 and steam are withdrawn from the top of the column. Lean, or re-generated absorbent is withdrawn from the base of the column, and is flashed over a flash valve and separated in a flash tank into a gas phase, that is compressed and returned into the regenerator column, and a liquid phase mainly comprising lean absorbent that is cooled by heat exchanging against incoming rich absorbent, wherein the gas phase and/or the lean absorbent is/are heat exchanged against a low temperature heat medium after leaving the flash valve.