Geothermal Power Generating Systems
There are several types of geothermal power generating plants. There is the single-flash, double-flash, dry-steam and binary cycle. These power plants can be converted into more advanced geothermal converting systems like hybrid single flash and double flash sytems, hybrid flash-binary systems, hybrid fossil-geothermal systems, hot dry rock (enhanced geothermal systems), Power plants for hypersalline brines, etc.. This paper will be focusing on Single-flash steam plants because it is the most commont type of geothermal power plant used. A single-flash steam plant is the mainstay of the geothermal industry. When a production well is drilled and it is found that it produces a two-phase mixture of vapour and liquid, single-flash steam plant will be installed to it. Single-flash steam plant is often the first power plant installed in a newly developed country. A unit power capacity of a single-steam power plant ranges from 3-90MW and has an average power rating of 25.3MW per unit. Before the single-steam plant can produce energy from the feed from the production wells, the feed must be separated first. The mixture of vapour and liquid feed from the production well are first put in a cylindrical cyclonic pressure vessel that is oriented vertically with its axis. The feed from the production well is transported to the cyclone separator via pipes. Transportation of the vapour-liquid mixture from the production well and separation of it in the cyclone separator can be done in several ways. These can be categorized through the piping lay-out of the plant. This paper will categorized the piping lay-outs from the location of the separators. •
Separator located at the powerhouse
Production wells are connected to a large cyclone separator located in the powerhouse via pipe. The steam separated from the feed in the separator enters the turbine through a short stream pipe while the separated liquid is sent to the injection wells through pipes.
Separator located at the satellite stations in the field
The feeds from 2-3 production wells are delivered to the separators in the satellite stations in the field. The separated steam from the different separators located in the different fields then flows through stream pipes and collected in the steam collector find near the powerhouse where it will be sent shortly to the turbine after collecting. The separated liquid is sent to injection wells from the separators through the pipe.
Separator located at the Wellheads
Every production well has a wellhead separator installed to it. Separated steam will flow through the individual stream lines attached to the powerhouse where the steam is collected in the collector. Separated liquids are then sent into the injection wells. An example of this can be found in Ahuachapan power station in El Salvador.
Equipment list for single-flash plants
Below is an outline of the important parts that can be seen in a single flash geothermal power plant.
Wellhead, brine and steam supply system
These are the parts where feed is produced and separated before flowing to the turbine. The feed that is in the well head is controlled so that the wanted amount only is pumped. After getting the desired amount, the feed is then separated in the separator vessels which can be found on the wellhead, satellite stations or in the powerhouse. The remaining condensate are then removed through other various methods/ equipment shown below. Some insulations are also found so that the steam would not condensate before entering the turbine. Below are the following parts in the wellhead, brine and steam supply system:
Wellhead, valves and controls
Blowout preventer (while drilling)
Vertical cyclone type
Bottom-outlet steam discharge
External or integral water collecting tank
Ball check valves
Steam piping, insulation and supports
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