Modifications of Sub-components in Thermal Power Plants for Exergetic Efficiency

Exergy analysis gaining importance as an engineering analysis tool for energy systems. This paper explores the possibility of decreasing exergy reduction in thermal power plant components like boiler, turbine and condenser and thus increasing exergetic efficiency of Power plants by redesigning the existing design of some important components like platen super heater, final super heater, re heater, condenser, so that resource sustainability improves. The method suggested for exergy destruction in condenser is by using Heat pipes and application of heat pipes for steam condensation has been validated with experimental results.

Organic Rankine Cycle Optimization Performance Analysis Based on Super-Heater Pressure: Comparison of Working Fluids

The organic Rankine cycle (ORC) is widely accepted to produce electricity from low-grade thermal heat sources. In fact, it is a developed technology for waste-heat to electricity conversions. In this paper, an ORC made up of super-heater, turbine, regenerator, condenser, pump, economizer and evaporator is considered. An optimization model to obtain the maximum performance of such ORC, depending on the super-heater pressure, is proposed and assessed, in order to find possible new working fluids that are less pollutant with similar behavior to those traditionally used. The different super-heater pressures under analysis lie in between the condenser pressure and 80% of the critical pressure of each working fluid, taking 100 values uniformly distributed. The system and optimization algorithm have been simulated in Matlab with the CoolProp library. Results show that the twelve working fluids can be categorized into four main groups, depending on the saturation pressure at ambient conditions (condenser pressure), observing that the fluids belonging to Group 1, which corresponds with the lower condensing pressure (around 100 kPa), provide the highest thermal efficiency, with values around η=23−25%. Moreover, it is also seen that R123 can be a good candidate to substitute R141B and R11; R114 can replace R236EA and R245FA; and both R1234ZE and R1234YF have similar behavior to R134A.

INFLUENCE OF DEPOSITION AND FOULING ON WALL TEMPERATURE DISTRIBUTION IN CONVECTIVE PATH

To develop a method of controlling the deposit tube surface temperature, the rules of deposition and fouling on the fireside, and the influence factors of the surface distribution were determined through experiments and theoretical calculations. The surface temperature distribution of a clean tube was compared with that of a deposit tube. Through theoretical calculations, the influence factors of the deposit tube surface temperature were evaluated. Based on the investigation, surface temperature control technology applicable to a super-heater was proposed and the feasibility of this heater was determined. A bimodal distribution was obtained when the temperature distribution of the deposit tube was plotted as a function of the angle, whereas a unimodal distribution was obtained for the clean tube. The results revealed that the heat exchange tube surface temperature is most effectively controlled by controlling the flue gas temperature. Prior to the development of higher performance materials (compared with conventional materials), surface temperature control technology can be used to ensure that the super-heater surface temperature lies below the allowable temperature of existing super-heater materials.

Study on Fracture Failures of the Super Heater Water Pipe Boiler

The purpose of this study was to analyse the failure of the super heater pipe of the Heat Recovery Steam Boiler Generator (HRSG), which had broken. Investigations are carried out in several stages. First of all, the microstructure of the pipe was observed using an Optic Olympus GX71 Microscope and a Scanning Electron Microscope (SEM) was used to observe the fracture surface to find the initial crack. Thereafter, chemical composition testing, to determine the type of material used in the super heater pipe. The presence of deformation by creep was due to overheating seen on the super heater pipes. Moreover, It was due to operating at elevated temperatures and pressures with long operating times. This condition caused the thickness of the pipe to thin so that it would break due to crack propagation which penetrated the wall of the pipe until breaking as the material was no longer able to withstand the steam pressure inside the pipe. Obviously that this condition indicates that the crack propagation occurred until final failure.

Analysis of Weld Cracking in a Low-Pressure Steam Pipe

A weld cracking of the outlet pipe occurred during the operation of a low-pressure steam super-heater in the purification device. It was found that many cracks were perpendicular to the weld, which affected the equipment safe operation. In order to investigate the failure cause, the samples containing weld and cracks in the outlet pipe were cut. The experiments, including chemical composition analysis, mechanical properties testing, scanning electron microscope observation, energy spectrum analysis and metallographic analysis, were performed. The results showed that the corrosion products had loose structure, mainly consisting of iron, sodium and phosphorus oxides. The metallographic results of the fracture section indicated that there existed a mixed cracks of trans-granular and inter-granular mode, along with stepped crack characteristics. Therefore, it is believed that the weld transverse cracking in the outlet pipe may be resulted by both of alkali stress corrosion cracking and the hydrogen induced cracking. According to the failure cause analysis, the corresponding suggestions are given, such as welding, operation process and inspection.

General Regression Neural Network versus Back Propagation Neural Network for Prediction of Reheater and Super Heater Sprays in Thermal Power Plants

Neural Network models are used for Reheater and Super heater spray prediction in Thermal Power Plants. This paper makes a comparative study of the General Regression Neural Network (GRNN) model versus the Back propagation Neural Network (BPNN) model for the quality and accuracy of prediction of Reheater and Super heater Sprays in Thermal Power Plants. It proves that GRNN is better and gives more stable prediction within range; the glitches between the predicted and actual values being less in number as well as value

An option for integration of Carnot Battery into a small Nuclear Power Plant

This article proposes a combination of nuclear power plant and grid-scale energy storage, classified as Carnot battery. The electric heater heats molten salts when excess electricity is available in the grid. The steam that is produced in a small modular nuclear reactor is heated with hot molten salts in the external super-heater. For continuous superheating to be ensured, the plant is equipped with molten salt thermal energy storage. The combined plant and reference NPP are modelled and simulated at steady-state conditions. Due to the higher turbine inlet temperature, the efficiency of the combined generation-storage nuclear plant is substantially improved. The proposed concept makes the co-location of NPP and Carnot Battery more attractive than the separate plants. The integrated thermal storage acts as secondary electricity storage. As such, it surpasses compressed air storage and is competitive with the pumped hydro storage, in the absence of their geographical and environmental constraints.