Does GE offer specific HRSG solutions for improved combined-cycle power plant performance and flexibility? What is GE’s standard approach for increasing the HRSG and combined-cycle power plant efficiency? How would you evaluate the lifetime of an HRSG if you have to change its operation mode from base load to cycling operation? How could HRSGs be improved such that they can work at maximum efficiency as soon as possible?
GE offers a variety of engineered solutions that are tailored to meet customers’ operating flexibility and performance requirements. One of these solutions is GE’s proven inhouse Once Through (OT) HRSG technology, which is a key enabler in advanced water-steam cycles, delivering higher combined-cycle efficiency with high cyclic capability.
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GE’s whole system approach is possible because our portfolio of products and services includes the engineering and manufacturing of all the major components of a CCPP—inhouse—to improve combined-cycle efficiency. In general, higher efficiency comes at a higher price, so our efficiency solution starts with a project-specific economic evaluation to help ensure that we’re balancing performance and capex. To achieve maximum efficiency, we try to extract as much of the exhaust gas energy as possible. With tighter pinches in the evaporators, less subcool leaves the economizers, and we are able to achieve an optimal feedwater temperature and higher steam temperatures and pressures.
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To perform a lifetime assessment we would typically look into the number of hot/cold/warm starts of the unit since the beginning of commercial operation. We would also look into the number of hours operated at base load and part load every year and compare those to the original specification of the unit. Then we would calculate the stresses on the most critical components, such as Superheater and Reheater headers, and would evaluate the theoretical lifetime consumed.
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In order to reduce boiler startup times while mitigating the effects of fatigue damage to the critical components (such as HPSH and RHTR outlet manifolds), it's necessary to reduce the strain range during the cycle between startups. This can be accomplished by increasing the initial boundary conditions at startup (for instance, changing "cold starts" into "warm starts") and/or by controlling the temperature ramp rate and peak temperature of the gas turbine. For new units, we can also supply manifolds that are enhanced for fatigue life.
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