Replacing Steam Jet Air Ejector By Vacuum Pump-in Garri 4 Power Plant-Case Study

Abstract

Garri4 Steam Power Plant works with regeneration Rankine cycle, It consists of two steam turbines each one generates 55 MW. In the Rankine cycle the steam jet air ejector or vacuum pump are utilized to generate and preserve vacuum in the condenser. Steam jet air ejector is simpler, lower cost, more reliable than vacuum pump , and does not consists of moving parts that need to be adjusted or repaired. Steam jet air ejector was installed in Garri4 but in commissioning operation ejector failed and did not satisfy the vacuum requirement for proper operation. To solve this problem two solutions were suggested and worked out, the first one is to replace the condensate water by fresh cooling water in the ejector’s cooler, but also it still failed and the second is to replace air ejector by vacuum pump which made vacuum sufficient to run the plant at full load. In this thesis, the problem of the air ejector had been studied; also reasons of its failure, the effect of replacing air ejector by vacuum pump on plant efficiency, selection and the necessary modifications for the pump had been attained. The research method in this thesis is a theoretical survey case study. It was found that the main air ejector failure is due to design calculations errors of the ejector inner cooler, the pump was selected according to the capacity required of (1550. The pump type is two stage, liquid ring vacuum Pump. The replacing steam jet air ejector by vacuum pump allows the plant to run at full load (55MW), with high performance and a considerable efficiency of (25.46%) and a few required modifications. It is observed that the vacuum pump's running and maintenance cost are higher than ejector's that consumes (55 kWh) more than ejector's (36.86 kWh).The pump works permanently so, the power loss is (18.14 kWh) equivalent to (156.73 MW) per year; then the cost is about (109711 SDG) per year. From these calculations and considerations, it is obvious that recalculation, redesigning and installing of air ejector are convenient enough because of the lower costs. It is recommended to redesign and use the air ejector instead of vacuum pump utilization.