By Joanne Liou, associate editor
Increasing emissions regulations and access to low-cost fuels are driving innovations in engine manufacturing. Requirements set by the US Environmental Protection Agency (EPA), as well as the designation of International Maritime Organization Emission Control Areas in the US and Europe, are raising the bar for lower emissions, stated Mikael Troberg, Wartsila, director of testing and performance, at the 2013 IADC Environmental Conference in New York City on 8 April. Due to variances among the fuels available in the market, it will take multiple technologies to help the industry reduce emissions across its global operations, he added.
Mr Troberg was joined on a panel at the conference by Aaron P. Trexler, power generation product line director, GE Oil & Gas; and Will Watson, offshore product marketing manager, Caterpillar Marine & Petroleum Power Division. Together, the experts shared insights into new engine technologies and advances in emissions control. Rhett Winter, IADC director onshore operations, moderated the session.
Panelists appeared to agree on the benefits of switching to natural gas from diesel. “We have 20% reduction in CO2, NOx is down 80% and SOx and particulates goes to 0%,” Mr Troberg stated. Further reduction in CO2 emissions is possible as engine efficiency improves, he added.
GE’s rich-burn Waukesha engine, for example, can run on any field gas, from propane to pipeline gas, according to Mr Trexler. This is important considering the varying gas quality across the US. “There’s a lot of varying gases throughout – from the Marcellus, Eagle Ford, Barnett and Bakken… A rich-burn engine allows you to run all those gases with very minimal treatment to the gas,” Mr Trexler explained. A rich-burn engine operates with a wide timing range to keep the engine running and prevent detonation, allowing for the higher tolerance and fuel composition. The engine also claims 95% lower emissions compared with diesel and 80% lower fuel cost.
As the price of diesel has continued to increase in the past few years, the delta is significant compared with LNG, CNG and field gas, Mr Trexler continued. Considering per-day fuel cost on a 1,500-hp rig site, it can cost upward of $4,500/day for diesel; that same amount of fuel to run the rig on LNG would be just over $2,500, or 41% less, he explained. “On CNG, it’s a little over $2,000, a 54% savings, and on field gas or associated petroleum gas, it’s a little less than $1,000.”
Caterpillar is focusing on engine performance to improve selective catalytic reduction (SCR) systems. “In this case, smaller is better, and we also need to maintain operating cost and performance,” Mr Watson stated. “The challenge we’ve had in our industry is trying to understand how to make this technology work with transient load applications.” Catalyst material has been refined to improve efficiency, not only in emission reduction but also in size reduction for the catalyst. “The engine itself remains unchanged; thus, existing proven engine parts can continue to be used, and for this particular solution, the SCR will meet Tier 4 interim and final regulations for EPA emission levels.”
Mr Watson reiterated the benefits of natural gas engines and further pointed to regulations around gas flaring, globally and in the US, which are “making people think, what are they going to do with that associated gas? It would be a crime to waste it,” he said. “Combined with the cost of diesel, you would get quick payback for a gas engine.”
Caterpillar is combining the power of diesel engines with the benefits of natural gas with dynamic gas-blending technology. The core of the technology is a compression engine that uses up to 70% natural gas. “It automatically adjusts the gas ratio to maintain performance of a diesel engine, maintains transient performance and also adjusts depending on the gas entering engine,” Mr Watson explained. “It monitors gas makeup to maintain that performance.”
Each technology has its own distinct advantages, but there is no silver bullet that meets the need for every application and every emissions regulation, Mr Watson said. “We are certainly doing our best to pair those solutions up and continue on with some of the cards we’re dealt with on the emission regulations side.”