| Title | Metal Silicate Formation at Tuzla Geothermal Brine Lines |
|---|---|
| Authors | Mustafa Inanli & Vedat Atilla |
| Year | 2011 |
| Conference | Western Pacific Regional Branch |
| Keywords | Silicate, scale, geothermal scaling, Tuzla, metal silicate, iron magnesium silicate, silica inhibitor, calcite inhibitor |
| Abstract | Tuzla Geothermal Power Plant is an Ormat manufactured ORC binary plant that is located in Northwestern part of Turkiye, in the city of Canakkale. The plant has been in operation since January 2010. The two-phase geothermal fluid coming from two production wells by artesian flow is separated as steam and brine at the wellhead horizontal separators and brine is pumped to the ORC Plant by booster pumps, while steam reaches the plant naturally. Separation pressure is 3bar.g and temperature of separated brine is 143Cdeg. Tuzla Geothermal brine is highly saline, with 32.000ppm Cl and 22.400ppm Na content, and has a conductivity of almost 100.000 ìs, with the total hardness around 9.000ppm. Although the hardness is high, Calcium Carbonate Scale has been successfully prevented in the wells by commercial inhibitors. The focus of this paper is mostly the metal silicate scale which precipitated in the separated brine lines and in the heat exchanger (Vaporizer & Preheater) tubes, where the brine is passing through (Brine Pressure at Vaporizer inlet is 3,5 – 4,25 bar.g, brine temperature is 142 Cdeg). The scale formation at the binary plant Vaporizer tubes not only decrease the heat transfer from the brine to the motive fluid n-pentane, but also decrease the volume of the brine flow passing through the Vaporizer, causing reduction in the energy output of the power plant. The scale analysis shows that the composition of the scale is mostly silis, iron and magnesium. To mitigate the silicate scaling problem various chemical inhibitors were tested. Effectiveness was evaluated both by the analysis of accumulated scale on coupons distributed in many locations along the brine line from Wellheads to the Vaporizer inlet, and analysis of PH, silis, iron and hardness levels at site laboratory. We also monitored the process parameters such as “brine inlet pressure” and “Vaporizer Motive Fluid Pressure” to get an indication on the effectiveness of the inhibitors. In search of the solution to the Scaling Problem, we continued in 4 lanes. 1. Testing local and international commercial inhibitors and dispersants that are not hazardous to the environment. 2. Studying the process (e.g. BOP design) and its effect on scaling such as Changing Separation Pressure, PH Adjustment with acid injection, Employing Lineshaft pumps in the production wells, Rerouting condensate in brine line upstream the Vaporizer inlet. 3. Keep on producing energy, by periodically cleaning HX tubes, pipe spools, pumps, valves, filters etc. Taking mechanical measures such as installing filtration systems upstream of the Vaporizer, and scale traps along the brine pipeline. 4. Ongoing research on the net, fairs, university visits etc. One year after the commissioning of the power plant, the Mg/Fe Metal Silicate scale formation rate has been reduced almost 6 times by using inhibitor. Further studies will be focused on the process and/or applications to go beyond the point that has been reached by inhibitors, so that we can start the investment of new modular units for bottoming cycle option, and later the second power plant. |