Montana-Dakota wins permit for new gas-fired capacity at Lewis & Clark

The Montana Department of Environmental Quality has set a Feb. 5 deadline for any party to request a hearing on its Jan. 6 final decision to grant an air permit revision to Montana-Dakota Utilities Co. for new gas-fired capacity at the coal-fired Lewis and Clark Station in Richland County, Montana.

“On November 7, 2014, the Department received an application to modify Montana Dakota’s air quality permit MAQP#0691-01 to construct, operate and maintain two 20V34SG Wärtsilä (or W20V34SG) natural gas RICE generator sets, an indirect fired fuel heater (gas line heater) and associated building heating, ventilating and air condition (HVAC) units for the purpose of generating electricity at the Lewis & Clark Station,” said a DEQ approval document.

Each of the engines will have a lean-burn four-stroke design, with a nominal gross output of approximately 9.3 MW. Under the revised permit, Montana-Dakota needs to limit gas consumption during normal operation of the two Wärtsilä natural gas RICE to a maximum of 530.8 MMscf per rolling 12-month period. Emissions from the RICE generator sets shall be controlled with a selective catalytic reduction (SCR) system using urea as the reaction agent, and an oxidation catalyst capable of maintaining the required emission limits.

Montana-Dakota needs to limit the total start-up operation (cold, warm and hot) of the two RICE units to a maximum of 500 hours per rolling 12-month period combined. Montana-Dakota has to operate a natural gas line heating unit and natural gas HVAC units with a maximum combined heat input not to exceed 4.2 MMBtu/hr.

The permit document noted: “For peaking units, startup emissions are a more frequent occurrence than for baseload facilities. One reason engines such as the Wärtsilä RICE are chosen as peaking units is because the RICE have a fast startup profile. The Wärtsilä RICE can achieve full load within approximately 10 minutes and emission controlled load within approximately 30 minutes from a cold start. However, the fast startup of the RICE results in varying exhaust flow, non-stable temperature, and a range of emission and oxygen levels. The emission control performance and emissions estimates during startup are based on Wärtsilä estimates and laboratory data.

“Montana-Dakota anticipates a maximum of 1000 startups per year for the two engines combined (equating to 500 startup events under cold start conditions). During startup, emissions controls (SCR and catalytic oxidation) are not up to temperature, and the full-load emissions limits are not applicable. Wärtsilä characterizes three types of startup for the RICE: cold, warm, and hot startups. Cold startups are described as starting up when the temperature of the SCR catalyst material inside the reactor is close to ambient temperature. These cold catalyst starts are generally expected when the engine has not operated in the previous 2-3 days. To fit in the framework of emissions, a cold start would be defined as starting up following a downtime of greater than 10 hours. A warm start would be defined as starting up following a downtime of between 6 and 10 hours. A hot start would be defined as starting up following a downtime of less than 6 hours. Shorter downtime periods are associated with shorter startup periods and lower emissions.”

The Lewis & Clark Station currently has a tangential coal-fired boiler (Unit 1) capable of burning coal or natural gas and associated equipment for generation of electricity.

Said the DEQ about the new plant capacity: “The Montana-Dakota Lewis & Clark Station shall operate two Wärtsilä natural gas RICE generator sets as peaking units to provide Montana-Dakota with additional generating resources to help meet its customers peak load requirements as well as providing reliability support to the region as a result of the increased peak electric demand in the areas around the Bakken oilfields in Eastern Montana and Western North Dakota.”

Basin Electric plans similar new capacity at Pioneer plant in North Dakota

Notable is that Basin Electric Power Cooperative is currently before the North Dakota Public Service Commission seeking a Certificate of Site Compatibility for the Pioneer Generation Station (PGS) Phase III Project. This project involves 12 Wartsila engines that are needed for about the same reason as the two engines that Montana-Dakota plans for Lewis & Clark – support for growing Bakken shale demand.

“The Basin Electric service area in northwestern North Dakota is experiencing a rapid increase in development as a result of the activities associated with oil and gas extraction from the Bakken shale formation, currently concentrated in McKenzie, Mountrail, and Williams Counties,” said the Basin Electric application, filed on Dec. 1. “The development that has already occurred and additional development planned for the future require numerous infrastructure upgrades throughout the region, including an increase in electrical generation capacity and reliability. Through load forecast studies, it has been determined that up to 12 reciprocating internal combustion engines (RICE or gas engines) are needed to serve the needs of northwestern North Dakota by increasing the power generation capacity, increasing voltage support for the electricity transmission system, and enhancing the reliability of the electrical system in the region.”

PGS currently consists of three General Electric LM6000PC natural gas-fired simple-cycle combustion turbines (SCCTs)—Units 1, 2, and 3—each with a nominal generation capacity of 45 MW. PGS is located in Williams County, North Dakota. Basin Electric proposes, under PGS Phase III, to construct, operate, and maintain up to 12 new RICE or gas engines. The proposed project would have the capability of generating up to 111 MW and would be designed to produce electricity at levels ranging from 3 MW to 111 MW. 

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.