Absorption Chiller Cooling Exhaust Gas for SCR Systems
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Solution Overview
Problem
Heavy-duty gas turbine systems face challenges in cooling exhaust gases to suitable temperatures for selective catalytic reduction (SCR) systems, requiring significant tempering air that reduces efficiency and increases energy input, especially due to high exhaust gas temperatures exceeding acceptable operating ranges for SCR catalysts.
Innovation Solution
The implementation of an absorption chiller that utilizes exhaust gas heat to drive a cooling process, cooling a portion of the exhaust gas and reintroducing it to reduce overall exhaust gas temperature, potentially eliminating the need for tempering air by using an exhaust gas heat exchanger and absorption chiller configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If tempering air is used to cool exhaust gas, then exhaust gas temperature is reduced to SCR operating range, but system efficiency decreases and energy input increases
Solution Approach 1:
The exhaust gas itself is used as the cooling medium through the absorption chiller system. The high-temperature exhaust gas drives the absorption cooling process, and the cooled exhaust gas is then reused to cool remaining exhaust gas, making the system self-sufficient without requiring external tempering air
Solution Approach 2:
The absorption chiller utilizes phase transition of the refrigerant (evaporation and condensation) to absorb heat from the exhaust gas, converting thermal energy into useful cooling effect while maintaining system efficiency
2Temperature
If tempering air is injected into exhaust gas, then exhaust gas temperature is reduced, but exhaust gas flow rate increases
Solution Approach 1:
A portion of the high-temperature exhaust gas is extracted and routed through the absorption chiller to be cooled, then returned to the main exhaust stream. This avoids introducing external air while still achieving temperature reduction
3Use of energy by moving object
If absorption chiller is used to cool exhaust gas, then tempering air requirement is reduced, but device complexity increases
Solution Approach 1:
The absorption chiller is integrated with the exhaust gas cooling system, combining the cooling function with the existing exhaust infrastructure. The chilled fluid path connects the absorption chiller to the exhaust duct assembly, creating a unified system that reduces overall complexity despite adding absorption cooling components
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 enhances the efficiency of gas turbine systems by reducing the reliance on tempering air, achieving effective cooling of exhaust gases within acceptable temperature ranges for SCR systems, thereby improving plant efficiency and potentially eliminating the need for tempering air, while maintaining homogeneity and reducing energy input.
Implementation Method 1
The absorption chiller is configured to use the take-off stream of exhaust gas to drive at least a portion of an absorption cooling process to generate a cooled take-off stream of exhaust gas
Implementation Method 2
The heat exchanger is positioned within the exhaust duct assembly or is part of a tempering air injection system configured to provide tempering air to the exhaust duct assembly
Data Source
AI summary
A gas turbine system includes a gas turbine engine configured to combust a fuel and produce an exhaust gas. An exhaust duct assembly is coupled to the gas turbine engine and is configured to receive the exhaust gas. An absorption chiller is fluidly coupled to the exhaust duct assembly and is configured to receive a take-off stream of the exhaust gas. The absorption chiller is configured to use the take-off stream to drive at least a portion of an absorption cooling process to generate a cooled take-off stream of exhaust gas. The exhaust duct assembly is configured to receive the cooled take-off stream of exhaust gas from the absorption chiller and to mix the cooled take-off stream with exhaust gas present within the exhaust duct assembly to cool the exhaust gas.