Utilizing from Low Pressured Waste Steam to Heat Injection Water by Using Direct Contact Steam Condenser: A Case Study

Abstract

Geothermal reservoir pressures which change due to interferences of wells, drilling of additional production wells, wrong re-injection strategy and reduction of NCGs content in reservoir, etc., drop in time . The decreasing in reservoir pressure results in more steam coming out of wells at less wellhead pressure than intial condition. Because of design parameter ranges of geothermal power plants, the most plants could not use the excess low pressure steam which is released to atmosphere at this point as a waste. The feasible ways must be sought after to recover this waste steam. Direct contact steam condenser (DCSC) is a system to recover for the waste steam. The idea behind the DCSC is to condense this waste steam which then can be send to the process to be used. It is different from shell and tube heat exchangers because there is no intermediate metal surface to transfer the heat from hot source to cold source. Hot and cold streams contact directly in the system which result in higher efficiency for the heat transfer then regular heat exchangers. There are several layers of equipment in the vessel to make this direct contact more evenly throughout the vessel. Cold source can be re-injection stream or process stream which is colder than the waste steam. DCSC is not just a pressured vessel but involves pumps, control valves, piping and instruments. This system is designed and implemented for 24 MW Kubilay Geothermal Power Plant of Bestepeler Enerji Üretim Tic. A.S in Aydın/Turkey to use their 139 °C waste steam at 2.7bar for heating up re-injection fluid. As a result, the temperature of re-injection water with 200 tons/hour flow rate increased from 60 °C to 135 °C by using 25 tons/hour unused waste steam at 139 °C. Then the new fluid at 135 °C with 220 tons/hour is used to generate 1500 kWe net electricity in Kubilay Geothermal Power Plant.