Flash Flashed Steam Power Plants

The flash plant schematic in Figure 1 was simplified from diagrams of the CalEnergy Company, Inc. (CECI) Salto n Sea Unit 2 power plant [4]. Technical descriptions of recently-built flashed-steam power systems can be found i n descriptions of the Magma Power Company Salton Sea units [5]; CECI Salton Sea Unit 3 [6,7]; CECI Coso units [8,9]; and GEO East Mesa units [10]. The NGGPP report [1] provides a range of process and cost information.

Equipment present in all or most flashed-steam systems includes:

a. One or two large vessels, flash tanks, wherein part of the geothermal fluid vaporizes ("flashes") into steam a t pressures less than the pressure in the reservoir. This steam, typically 18 to 25 percent of the mass of the fluid from the reservoir (for double flash plants), is sent to the high-pressure (HP) and low-pressure (LP) inlets of a turbin e or turbines. The amount of steam depends on conditions in the reservoir and the designs of the production well s and power plant. The remaining liquid ("brine") from the second flash tank (75 to 82 percent of mass) is disposed of in the injection wells. The turbine in the dual flash system shown has dual inlets to admit high pressure stea m from the first flash tank, and low pressure steam from the second flash tank.

b. Special features related to minimizing the deposition of silicate scale. For the plant depicted in the system diagram (but not at most U.S. flash plants), the geothermal brine contains substantial amounts of dissolved silica, whic h tends to precipitate upon equipment walls as hard scale if not treated. The ameliorating features may include : (a) Elevation of the conversion cycle's brine exit temperature above that optimal for maximum power production. This tends to keep some of the silica in solution. This is the method of choice when silica problems are small t o moderate. (b) A "crystallizer-clarifer" system. This consists of a brine solids clarifer, and a return line from the clarifier that injects silica seeds into the first flash tank. In that case, the flash tanks are called "crystallizers " because the silica seeds prevent the precipitation of amorphous silica on the walls of the vessels and connectin g pipes. The liquid from the second crystallizer is sent to a third large vessel, the "clarifier," in which th e precipitation, flocculation, and removal of solid silica are completed. (c) A "pH-modifcation" system (shown i n the flash-system schematic in Figure 1). This provides the same functions as the crystallizer-clarifier system b y injecting small quantities of acid upstream of the first flash tank to reduce the pH of the geothermal fluid.

c. Gas ejection equipment. At reservoirs where the concentration of noncondensible gases (e.g., CO 2) is high, substantial gas ejection equipment is attached to the condenser. The ejectors are driven by steam or electricity . If hydrogen sulfide in the gases require abatement, H 2S control equipment is attached downstream of the ejectors.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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