Yanaizu-Nishiyama Geothermal Power Station H2S Abatement System

Abstract

Tohoku Electric Power Co., Inc.ís Yanaizu-Nishiyama Geothermal Power Station (Fukushima Prefecture, Japan) started commercial operation in May 1995. At 65 MW it has the largest geothermal power output from a single unit in Japan.

Since the start of test operations in December 1994, some people have complained about an odor in the air. To evaluate this, Tohoku Electric Power measured and analyzed the possible sources of the odor using air sampling bags and continuous hydrogen sulfide (H2S) monitoring equipment. The source of the odor was identified as the H2S that was released from our geothermal station at a very low concentration range of 6-60 ppb. Based on the results of an odor survey, we decided, from various anti-odor countermeasure options, to install an H2S abatement system as the most effective way to resolve the odor problem. An H2S abatement system had not been installed in Japan before, but we selected this method with environmental protection as the primary goal. The system is a dry-type that oxidizes H2S gas with a catalyst and generates by-product molten sulfur. It is the worldís first application with this type of system in a geothermal power station. The H2S abatement efficiency is high (over 90%) and the system is easy to operate. The system was completed in July 1998 and is now operating satisfactorily.