Organic Rankine Cycle Thermal Recovery via Intermediate Steam Loops
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Solution Overview
Problem
Current energy recovery systems for beam reheating furnaces face inefficiencies and safety risks due to fluctuations in flue gas temperature and power variations, particularly when using organic Rankine cycles with molten salt cooling systems, which can lead to overheating and fire hazards.
Innovation Solution
Implementing an energy recovery installation with separate intermediate recirculation loops for steam and flue gas circuits, isolated from the organic fluid loop by heat exchangers, to stabilize energy input and prevent contact risks, while using an organic Rankine cycle to generate electricity from both sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If flue gas is used directly to heat the organic fluid in the ORC system, then energy recovery efficiency is improved, but temperature fluctuations cause unstable ORC operation and potential overheating
Solution Approach 1:
A water/steam intermediate loop is introduced between the flue gas and the organic fluid. The flue gas heats water in a heat exchanger, generating steam that then heats the organic fluid. This intermediary system buffers temperature fluctuations, stabilizing the heat input to the ORC while maintaining high energy recovery efficiency
Solution Approach 2:
The system utilizes phase change of water (liquid to steam) as an intermediate heat transfer mechanism. The phase transition absorbs and releases large amounts of latent heat, effectively stabilizing the temperature profile and providing consistent thermal energy to the ORC system despite variable flue gas conditions
2Loss of energy
If molten salt cooling system is used for beam cooling, then heat recovery from beams is improved, but overheating and fire hazards occur due to temperature fluctuations
Solution Approach 1:
The system uses water/steam as an intermediary cooling medium instead of molten salt. Water circulates through the beam cooling system, absorbing heat and generating steam that is then used to heat the organic fluid. This eliminates the fire hazards associated with molten salt while maintaining effective heat recovery from the beams
Solution Approach 2:
The system exploits the phase transition of water from liquid to steam during the cooling process. This phase change provides a safe, controlled mechanism for heat absorption and transfer, replacing the hazardous molten salt system while enabling efficient thermal energy recovery from the beam structure
3Reliability
If separate intermediate loops for steam and flue gas are implemented, then safety is improved by preventing contact, but system complexity increases
Solution Approach 1:
The thermal energy transfer system is segmented into distinct loops: flue gas loop, water/steam intermediate loop, and organic fluid loop. Each loop is separated by heat exchangers, preventing direct contact between incompatible substances while maintaining efficient heat transfer. This segmentation ensures safety by isolating flue gas and organic fluid from each other
Solution Approach 2:
The water/steam intermediate loop serves multiple functions simultaneously: it acts as a heat transfer medium from flue gas, provides phase change for thermal buffering, and safely isolates the organic fluid from flue gas contamination. This multi-functionality reduces the need for additional complex safety systems
4Productivity
If stable energy input to ORC is ensured, then electricity generation consistency is improved, but investment costs increase due to additional heat exchangers and loops
Solution Approach 1:
The system utilizes the latent heat of vaporization and condensation of water/steam as a natural thermal buffer. This phase transition mechanism provides stable energy input to the ORC without requiring complex active control systems or additional expensive equipment, achieving consistency through passive thermal physics
Solution Approach 2:
The system recovers thermal energy that would otherwise be wasted (flue gas heat and beam cooling heat) and converts it to useful electricity through the ORC system. By discarding nothing and recovering all available thermal energy, the system achieves consistent electricity generation while the heat exchangers represent a one-time capital investment with long-term operational benefits
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 configuration enhances safety, increases annual electricity generation, reduces investment costs, and ensures consistent operation by stabilizing the energy input to the ORC machine, allowing it to operate efficiently across a wide range of heat source variations.
Implementation Method 1
The structure of the beams is made up of tubes or hollow profiles which are cooled by circulating heat transfer fluid
Implementation Method 2
The cooling of the structure of the beams by a mixture of saturated water and steam is advantageous, particularly because this makes it possible to ensure the operation of the structure of the beams at a stable temperature. Indeed, since the phase transition from the liquid phase to the vapour phase takes place at a substantially constant temperature
Implementation Method 3
at least heat exchangers functionally arranged so as to transfer to said organic fluid, at least a portion of the calories contained in flue gases of the burners, via a heat transfer fluid, and at least part of the calories contained in the vapour, via a heat transfer fluid
Implementation Method 4
said installation comprising a turbine arranged to generate electricity by implementing a Rankine cycle on an organic fluid
Implementation Method 5
an expansion cycle turbine using a fluid other than water vapour
Data Source
AI summary
A heat energy recovery installation installed on a beam reheating furnace equipped with burners includes a turbine that generates electricity by implementing a Rankine cycle on an organic fluid coming from calories derived partly from the fluid used for cooling the tubular beams via a first intermediate circuit, and in part from flue gases from the burners by way of a second intermediate circuit.