Flue Gas Heat Recovery Using Exothermic Brine Absorption
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Solution Overview
Problem
Conventional technologies face challenges in efficiently extracting heat and water from flue gases, particularly in water-constrained environments, as excessive heat extraction can lead to corrosion and the economic viability of water recovery is limited due to water availability in inhabited areas.
Innovation Solution
A process involving the introduction of moist flue gas to a brine that exothermically absorbs moisture, producing heat, and recovering the brine through multiple-effect distillation to generate steam, with heat pipes operating within a packed absorption column to facilitate efficient heat transfer and moisture absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heat is extracted from flue gas to pre-heat boiler feed water, then energy efficiency is improved, but the amount of extractable heat is limited and condensation can cause corrosion
Solution Approach 1:
The patent introduces brine as an intermediary substance between the flue gas and the heat recovery system. The brine absorbs moisture from the flue gas exothermically, acting as a mediator that enables heat recovery without direct contact between flue gas and water, thus preventing condensation corrosion while improving energy efficiency
Solution Approach 2:
The patent changes the physical and chemical parameters of the absorption process by using brine instead of conventional absorbents. The exothermic absorption reaction changes the temperature and concentration parameters, enabling efficient heat recovery while maintaining conditions that prevent condensation and corrosion
2Quantity of substance
If water is recovered from flue gas in water-constrained environments, then water availability is improved, but the economic viability is reduced due to water availability in inhabited areas
Solution Approach 1:
The patent changes the economic parameters by producing positive pressure steam as a valuable byproduct. This transforms the water recovery process from a low-value operation to a high-value operation that generates usable steam for industrial processes, thereby improving economic viability while maintaining water recovery capabilities
3Power
If brine is used to exothermically absorb moisture from flue gas, then heat production is improved, but the brine temperature must be maintained within a narrow range
Solution Approach 1:
The patent implements a self-regulating temperature control system where the brine circulation and heat exchange processes automatically maintain the brine temperature within the optimal range. The system uses the inherent thermal properties of the brine and the heat exchange dynamics to self-regulate, reducing the need for complex external temperature control mechanisms
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 process effectively recovers heat and water from flue gases, reducing corrosion risks and improving economic viability by producing positive pressure steam while maintaining efficient heat exchange and water conservation.
Implementation Method 1
introducing said moist flue gas to a flow of brine, said brine being adapted to exothermically absorb moisture from the flue gas to produce heat
Implementation Method 2
the withdrawal of heat is associated with the phase change of a working fluid from the liquid state to a gaseous state; the terminus of the heat flow is associated with the phase change of the working fluid from the gaseous state to the liquid state
Implementation Method 3
a plurality of heat pipes each leading between the flow channel and the interior of the vessel, the surfaces of the heat pipes operating in use in the manner of packing in a packed absorption column, thereby to facilitate the absorption of moisture from the flue gas and the generation of heat
Implementation Method 4
the brine is recovered through multiple-effect distillation of the water-enriched brine
Data Source
AI summary
Disclosed is a process for use with flue gas having a moisture content M. The flue gas is introduced to strong brine adapted to exothermically absorb moisture. Simultaneously, heat is withdrawn. This produces heat, water-enriched brine and a gas having a moisture concentration less than M. The strong brine can be recovered by distillation from enriched brine to produce water. The brine temperature throughout absorption can remain within 2° F. of a temperature T in the range 220° F.-300° F. The heat withdrawal can be associated with gas-liquid phase change of a working fluid. The terminus of the heat flow can be associated with gas-liquid phase change of the working fluid. The working fluid can: as liquid, flow only by gravity, convection or wicking; and, as gas, flow only by diffusion or convection. The heat flow can drive a boiler producing steam. M can be greater than 15 wt. % water.