Content area
Full Text
Coso Operating Co. LLC operates a 300-MW electricity generation facility at the China Lake Naval Weapons Station, approximately 170 mi northeast ofLos Angeles, California, at Coso Junction. After steam wells are tapped and gathered, they produce electricity from the renewable geothermal energy source. The produced steam is passed through a set of turbines/ generators. Non-condensable vapors are separated from the condensed steam (water) at low pressure. Finally, the brine is reinjected into the geothermal field.
The non-condensable vapors cannot be vented to the atmosphere until small amounts of hydrogen sulfide (H2S) are removed. When the plant was started up initially, the H2S-laden vapors were reinjected into the geothermal field with water (H2O). Over time, this H2S abatement method became costlier, mostly due to compressor maintenance. In 1993, the first of three LO-CAT units was installed. After startup, the non-condensable carbon dioxide (CO2) and H2S were flashed, compressed and routed to the LO-CAT unit for sulfur removal before being emitted into the atmosphere.
The LO-CAT process has been removing H2S at the site for the past 22 yr. This technology greatly reduced sulfur emission exceedances and operating costs relative to technologies used prior to installing the LO-CAT unit.1
The site has a total of four power generation facilities, with two of them containing LO-CAT units: the Navy 1 power plant and Navy 2 power plant. The site has a total of three LO-CAT units (TABLES 1 and 2). The Navy 2 site has two LO-CAT units, the Navy 2 unit and the Navy 210 unit. Only the Navy 210 is discussed here, since the Navy 2 unit is only periodically operated.
Overall, the units have operated well throughout their history.
LO-CAT process description and process flow. The LO-CAT process converts H2S contained in the raw feed gas into elemental sulfur (FIG. 1).
Before entering the LO-CAT unit, raw feed gas passes through an activated carbon bed to absorb mercury and other heavy metals. The raw gas then enters the autocirculation vessel where the H2S is absorbed into a proprietary LO-CAT catalyst solution. The catalyst is deactivated in the absorber section where H2S is converted into elemental sulfur. Subsequently, the catalyst is regenerated...