Load Optimization By Steam And Blade Washing In A Flash Type Power Plant-A Case Study Of Olkaria Ii Geothermal Power Plant

Abstract

Generator load is the key focus of a power plant which is significantly affected by its generating equipment which can be determined by both maintenance and the running parameters. The pa-rameters of interest for this study were turbine inlet pressure, steam flow rate, steam chest pres-sure (Bowl pressure) and Generator Loading. The operation of Olkaria II power plant was started in the year 2002, with Unit I turbine taking steam at a flow rate of 62.5 Kg/Sec (225 ton/hr). Af-ter operating for 2 years, steam chest pressure increased from 2.5 bar g to 4.1 bar g and steam consumption increased to 72.2 kg/s (260 T/hr.) with the turbine power generation capacity de-creased to 26.4 MW out of the rated capacity of 35.0 MW. After dismantling and inspecting for the purpose of this study in 2015 the turbine and its major auxiliary equipment, it was found that significant Sulphur deposition, scaling and related compounds had occurred on the turbine shroud, the turbine nozzles and the cooling tower, reducing their efficiency and leading to re-duced power generation. The purpose of this research was to explore blade washing and steam washing operation procedures for removal of silica scaling and deposition at the Turbine blades and nozzles, improving the geothermal power plant efficiency through addressing scales and mineral deposition for improvement of plant performance and productivity. The method em-ployed was the use of steam and blade washing technique. Condensate water is tapped and pumped through spray nozzles to the main steam line while in operation mode (power genera-tion).The pump discharge pressure to the main steam line is 14 bar g and this is above the main steam line pressure of 4.2 bar g. This sprayed water atomizes and increases the density of the steam in the localized area of the main steam line. This mixture then hits the silica deposits around the Turbine blades and nozzles and over a period of time the silica scaling is washed away under pressure. In real time data analysis, the study realized that steam and blade washing have positive effects on load optimization. Once the turbine blade washing was introduced, the steam flow rate needed to generate 1Mwe of power was reduced from a high of 7.9Kg/s to a mean value of 7.24Kg/s. This therefore makes this study conclude that blade washing and steam washing programs improves on turbine efficiency hence optimizes load in a geothermal power plant from silica dominated systems. The research analysis therefore enhances the study of the effects of steam and blade washing on the silica scaling, steam chest pressure, and power plant efficiency.