Water Selective Separators for Flue Gas Heat Recovery
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Solution Overview
Problem
The high water vapor content in flue gas from syngas combustors in IGCC plants prevents the recovery of heat for power generation due to the need to maintain temperatures above the dew point, leading to energy inefficiency and potential corrosion issues.
Innovation Solution
Implementing a power plant with a combustor and downstream water selective separators to remove water from the flue gas, allowing for heat recovery and reusing the separated water in the syngas production process to increase hydrogen content without increasing water consumption, using membranes like hydrophilic stainless steel or ceramic filters to achieve high water recovery efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If water selective separators are used to remove water from flue gas, then heat recovery efficiency is improved, but device complexity increases
Solution Approach 1:
The patent extracts water vapor from the flue gas stream using water selective separators (membranes) positioned downstream of the combustor. By removing water before the heat exchanger, the flue gas temperature can be reduced more effectively without condensing water, enabling更高效 heat recovery while preventing corrosion.
Solution Approach 2:
The water selective separator acts as an intermediary component between the combustor and heat exchanger. It selectively removes water vapor from the flue gas, allowing the system to achieve lower temperatures in the heat exchanger without water condensation, thus enabling more efficient heat recovery while protecting against corrosion.
2Reliability
If flue gas temperature is maintained above dew point to prevent corrosion, then equipment reliability is improved, but heat recovery efficiency deteriorates
Solution Approach 1:
The patent extracts water vapor from the flue gas using water selective separators before the gas enters the heat exchanger. This removal of water allows the flue gas temperature to be reduced below the original dew point without causing water condensation and corrosion, thereby improving heat recovery efficiency while maintaining equipment reliability.
Solution Approach 2:
The patent changes the composition parameter of the flue gas by removing water vapor. This parameter change effectively lowers the dew point temperature of the flue gas, allowing the system to operate at lower temperatures in the heat exchanger without water condensation, thus improving heat recovery while preventing corrosion.
3Loss of energy
If hydrogen content in syngas is increased through water-gas shift reaction, then energy yield is improved, but water consumption increases
Solution Approach 1:
The patent recovers water vapor that would otherwise be discarded in the flue gas by using water selective separators to extract it. The recovered water is then fed back to the gasifier and/or CO shift cell, reducing the need for fresh water input while maintaining the water-gas shift reaction for hydrogen production, thus improving energy yield without increasing net water consumption.
Solution Approach 2:
The patent implements a feedback loop where water vapor separated from the flue gas is returned to the gasifier and CO shift cell. This feedback mechanism ensures that water consumed in the water-gas shift reaction for hydrogen production is replenished by recovered water, maintaining sustainable operation with reduced net water consumption.
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 the recovery of about 70% of the flue gas water, which can be reused, reducing energy consumption and improving overall power generation efficiency by enabling more heat recovery and reducing the need for fresh make-up water preparation, while maintaining equipment integrity.
Implementation Method 1
downstream of the flue gas outlet water selective separators are provided to separate water from the flue gas
Implementation Method 2
using membranes like hydrophilic stainless steel or ceramic filters to achieve high water recovery efficiency
Implementation Method 3
The hydrogen content in the syngas can be increased by the water-gas shift reaction. With this reaction carbon monoxide reacts with water to form carbon dioxide and hydrogen: CO(g) + H2O(l) → CO2(g) + H2(g)
Implementation Method 4
Heat can be extracted from the flue gas discharged from the combustor to be used for generating power, typically via a steam cycle
Implementation Method 5
Heat can be extracted from the flue gas discharged from the combustor to be used for generating power
Data Source
Figure 1
AI summary
A process and a power plant (1) comprising a combustor (7) with a flue gas outlet (8) and one or more water selective separators (9) downstream the flue gas outlet to separate water from the flue gas. Optionally, a water return line (11) returns separated water from the water selective separator (9) to a water inlet of a CO shift cell (5) with an outlet feeding H2 enriched syngas to the combustor.