Air Separation Unit Heat Integration in Oxy-Fired Steam Cycles
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Solution Overview
Problem
Existing coal-fired oxy-combustion steam plants face challenges in optimizing the integration of thermal sinks such as the Air Separation Unit, Flue Gas Heat Recovery System, Flue Gas Condenser, and Gas Processing Unit within the steam power cycle, leading to inefficiencies and energy wastage.
Innovation Solution
The integration of the Air Separation Unit heat exchanger with the condensate system, allowing for thermal and fluid parallel connections with low-pressure heaters, and the inclusion of a Flue Gas Heat Recovery System heat exchanger to recover heat from the flue gas, enabling flexible plant operation and improved thermal efficiency across varying load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the Air Separation Unit heat exchanger is integrated with the condensate system in parallel with low pressure heaters, then thermal efficiency is improved through better heat recovery, but device complexity increases due to additional thermal integration connections
Solution Approach 1:
The Air Separation Unit heat exchanger is thermally integrated with the condensate system by connecting it in parallel with the low pressure heaters. This merging of previously separate thermal systems allows heat recovery from the air separation process to directly preheat condensate, improving overall thermal efficiency while utilizing existing system components
Solution Approach 2:
The condensate system is designed to serve multiple functions: it not only heats condensate through the low pressure heaters but also receives thermal energy from the Air Separation Unit heat exchanger. This multi-functionality allows the same system to handle different heat sources and optimize energy utilization across varying plant load conditions
2Use of energy by moving object
If the Flue Gas Heat Recovery System heat exchanger is connected to the condensate system, then energy recovery is maximized, but device complexity increases due to additional heat exchanger connections
Solution Approach 1:
The Flue Gas Heat Recovery System heat exchanger is integrated with the condensate system, merging the flue gas heat recovery function with the condensate heating function. This allows simultaneous heat recovery from flue gases and condensate preheating through coordinated thermal connections, maximizing energy recovery from available heat sources
3Object-generated harmful factors
If the plant operates in oxy-mode at part load conditions, then emission reduction is maintained, but thermal efficiency decreases due to reduced heat recovery opportunities
Solution Approach 1:
The thermal integration system is designed with dynamic adaptability to operate effectively across varying load conditions including part load oxy-mode operation. The parallel connections and multiple heat recovery paths allow the system to maintain optimal thermal efficiency by dynamically adjusting heat flow distribution according to available heat sources and plant operating conditions
Solution Approach 2:
The integrated heat recovery system ensures continuous useful thermal action by providing multiple parallel heat transfer paths. The Air Separation Unit heat exchanger and Flue Gas Heat Recovery System work continuously to recover thermal energy, ensuring that emission reduction benefits are maintained without significant thermal efficiency loss even at reduced plant loads
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 thermal integration, allowing the plant to operate efficiently at part load conditions and ensures maximum net energy transfer, optimizing heat recovery and reducing energy wastage by matching temperatures and recovery duties.
Implementation Method 1
an Air Separation Unit heat exchanger as part of the compressed air stream used for oxygen stream production
Implementation Method 2
Exhaust steam from the last low pressure steam turbine (LP) is condensed in a condenser (2)
Implementation Method 3
a plurality of low pressure heaters arranged in series and configured and arranged to receive the condensate from the condenser
Implementation Method 4
a Flue Gas Heat Recovery System heat exchanger to recover heat from the flue gas
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A coal fired Oxy boiler power plant having a combustion system adapted to burn coal using an oxygen stream to produce a flue gas stream, a CO2 capture system connected to the flue gas stream and a steam cycle with serially arranged low pressure heaters (6,7,8,9,31) forming part of a condensate system. The combustion system comprises an Air Separation Unit for removing N2 from air to produce the oxygen stream for the boiler (42). The Air Separation Unit includes an Air Separation Unit heat exchanger (11) that is thermally and fluidly connected to the condensate system so as to be fluidly parallel to at least one serial low pressure heater and fluidly parallel to at least one less that the total number of serial low pressure heaters. Flue Gas Heat Recovery System, Flue Gas Condenser and Gas Processing unit are thermally integrated into the condensate system.