Development & Field Verification Testing of an Oxidizing Converter & a Compatible Lube Oil for Two-Stroke, Lean-Burn Gas Engines
Because of the increasing emphasis on achieving low exhaust emissions for stationary gas engines, an oxidizing converter was developed for Ajax two-stroke lean burn (2SLB) engines in 2004. A few months prior to the effective compliance date for the ICE MACT rules which require large reductions in the formaldehyde levels for engines rated at >500 BHP, these converters were placed into service with two 710 BHP engines at a gas compression plant in Colorado. To assure continuous compliance with the emissions regulations, it was guaranteed that the CO removal efficiency with the original catalyst elements would not fall below 60% during the first six months of operation. Oxidizing converters have been proven highly effective for many years for four-stroke stationary engines. However, previous efforts to establish successful use of oxidizing converters for 2SLB engines had not produced adequate long term emissions removal efficiencies. There are several challenges associated with the use of converters on 2SLB engines which include: catalyst fouling from the products of combustion of the force fed cylinder oil, relatively low exhaust temperatures, and occasional rapid pressure fluctuations in the exhaust system. After confirming successful emissions removal efficiencies during a 500-hour R&D lab test, two of these converters were placed into service in the field. This paper focuses on the subsequent monitoring of the field performance during the first two years of operation and on several improvements which were implemented to enhance the commercial viability for the converters. These improvements include two major advancements to this technology: (1) The development of a catalyst box that can be retrofitted to existing exhaust silencers. (2) The formulation of a lube oil that avoids catalyst fouling and which can be successfully used for cylinder and crankcase lubrication.