Hazardous Materials and Waste
HAZARDOUS MATERIALS-RELATED PERMITS [Table E-1]
HAZARDOUS WASTE QUANTITIES [Table E-2]
HAZARDOUS WASTE STREAMS [Table E-3]
HANDLING OF HAZARDOUS CONSTITUENTS OF GEOTHERMAL STEAM
GEYSERS GEOTHERMAL POWER PLANT
The Geysers Power Plant has 14 generating units (at 11 sites) with a total net installed design capacity of 1,224 MW. Several characteristics of the Geysers plant make its operations, potential associated environmental impacts, and regulatory system different from PG&E’s fossil-fueled plants. For example, because these units use naturally heated geothermal steam as their energy source, the plant does not require the use of a fuel (e.g., natural gas) for steam generation, as do PG&E’s fossil plants. The Geysers plant, therefore, does not have emissions from boilers (such as nitrogen oxides, sulfur oxides and carbon monoxide) that occur as a byproduct of combustion at the fossil-fueled plants. (4) Instead, the air emissions from the Geysers plant are principally due to naturally occurring constituents of the geothermal steam released to the air during condensation of the steam after it passes through the turbine. One significant constituent is hydrogen sulfide (H2S), and all the units are equipped with hydrogen sulfide abatement systems.
The geothermal steam contains small amounts of "non-condensable gases." These gases are removed from the condenser and transferred to a H2S abatement system. The various H2S abatement systems at the Geysers plant are described below. After converting the H2S component to other sulfur species, the non-condensable gases are routed into the cooling tower and exit to the atmosphere.
Geysers Geothermal Power Plant Flow Diagram [Figure E-1]
Hydrogen Sulfide Abatement Systems
Several different systems are used to remove most of the non-condensable H2S at the Geysers Plant. These systems are:
Incinerator: This system burns H2S to form sulfur dioxide, which is then scrubbed in a quench tower and dissolved into the quench water. The quench water is transferred to the cooling tower basin.
Caustic: Sodium hydroxide, which absorbs H2S, is added to the cooling water at the inlet of the condenser.
Stretford: This system chemically oxidizes the H2S to elemental sulfur.
Metal Chelate: An iron chelate solution and air are added to the circulating water. The solution, oxygen, and hydrogen sulfide react to produce elemental sulfur, which is suspended in the circulating water. (5)
The H2S abatement systems employed at the various units are given in [Table E-4]
HAZARDOUS MATERIALS-RELATED CONDITIONS OF CERTIFICATION FOR GEYSERS PLANT [Table E-5]
4. The Geysers plant does have relatively minor emissions of nitrogen oxides, sulfur oxides and carbon monoxide that result primarily from the use of a burner/scrubber system for the abatement of hydrogen sulfide. (back)
5. Some of the chelate solution comes from PG&E’s fossil plants which use EDTA (Ethylene Diamine Triacetic Acid) solution to clean boiler tubes. EDTA combines with iron to form a metal chelate. (back)
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