Interstate Power and Light pursues oil-to-gas conversion project in Iowa

Interstate Power and Light applied Feb. 20 at the Iowa Utilities Board for a non-approval of a plan to convert three oil-fired units at its Marshalltown Generating Station (MGS) site to natural gas.

What this Alliant Energy (NYSE: LNT) subsidiary asked for was a decision by the board to not require a certificate for this project. IPL owns three 63-MW combustion turbine units in Marshalltown, Iowa, that began operating in 1978. IPL plans to convert the CTs from No. 2 fuel oil to natural gas. The fuel conversion of a facility is defined as a “significant alteration” under Iowa Code, which subjects the filer to certain siting and construction requirements. IPL wants a waiver of those requirements.

The CTs are located between IPL’s existing Sutherland Generating Station (SGS) and IPL’s gas-fired, combined-cycle MGS, which is currently under construction. During the MGS approval proceedings before the board earlier this decade, IPL signaled its intention that converting the CTs was part of its long-term plan following the approval of MGS.

In preparation to build MGS, IPL obtained the necessary air permits from the Iowa Department of Natural Resources (IDNR). As a condition to the operating air permits for MGS, the IDNR required that all generation at the site be fueled by natural gas before commercial operation begins at MGS.This means that the CTs must be converted to run on natural gas by the second quarter of 2017 or retired.

The cost of the facility fuel conversion and associated overhaul work is estimated at approximately $39 million, which is more cost effective than building new generation, the utility noted. Conversion of these units, along with the associated overhaul work, will reduce air emissions (principally nitrogen dioxide, particulate matter, and sulfur dioxide) while maintaining current reliability and capacity. The conversion will allow IPL to mitigate future load forecast and market price uncertainty and support existing renewable energy generation through quick-start capabilities, while preserving the existing transmission interconnection. Removal of fuel oil-related infrastructure from the site and cessation of fuel oil handling will also result in other positive environmental impacts.

The fuel conversion requires a new natural gas supply, including new dew point heaters, instrumentation, meters, regulators, valves, and piping, as well as the removal of the liquid fuel components on the CTs and their replacement with dual-fuel components so that water injection can be used in conjunction with the new fuel to reduce emissions. The CTs have an aero-derivative configuration, allowing them to start quickly and operate at low loads.

The new natural gas pipeline serving MGS will provide a reliable fuel supply to both the Marshalltown CTs and SGS. The pipeline is already sized to accommodate the operational needs of the converted CTs, so only a short lateral – that will be located entirely on IPL property – is required to connect the the CTs to the new MGS natural gas pipeline.

The CTs must be taken out of service in order to perform the fuel conversions. IPL said it will use this chance to perform overhaul work on the CTs that can only be done when they are out of service. CT auxiliaries – including controls, starting air compressors, electrical components, and other miscellaneous equipment – will be replaced in order to support remote operation and control from MGS. All of this work will be completed with the goal of achieving a reliable, 20-plus year service life for the converted CTs.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.