Influence of Maintenance Intervals on Performance and Emissions of a 192 kWel Biogas Gas Otto CHP Unit and Results of Lubricating Oil Quality Tests—Outcome from a Continuous Two-Year Measuring Campaign

Abstract

Abstract:In the present work, we focus on long-term and permanent measurements of approximately two years on a 192 kW el Gas Otto CHP (combined heat and power) unit at a full-scale research biogas plant. In detail the influence of 600 h and 1800 h maintenance intervals on electrical efficiency consumption and exhaust gas emissions such as NO x and CO have been studied under real life conditions. Lubricating oil quality analyses throughout the CHP operation time are presented to show the destructive changes in property and its influence on condition based maintenance. The results confirm the well-known fact that after readjustment of the air-fuel ratio after 1800 h maintenance the emission values for NO x decline while CO increases. The emission-optimized operation mode leads to lower engine efficiency. The maintenance tasks carried out at 600 h intervals lead to lower NO x emissions in nine cases while in 14 cases the emissions remained unchanged. The permanent measurements proved their legitimacy showing various emission deviations from the limiting values prior and post maintenance. The results show that by monitoring the lubricating oil quality, the oil change intervals can be maximized while ensuring that engine performance is not endangered, and a longer engine lifespan can be expected. The OPEN ACCESSEnergies 2013, 6 2820 oil analyses allow the operator to reduce maintenance expenditures while minimizing wear.

<b>Analysis of lubricant oil contamination and degradation and wear of a biogas-fed otto cycle engine

“…This behavior of variation (increase and decrease) of the total base number and of the viscosity at 100°C was also verified in the experiment of Naegele et al (2013), in which an MTU engine was assessed, model MDE MB 3066 L4, operating on rigorously filtered biogas (approximately 0 ppmv of hydrogen sulfide); however, there was an increase in oil viscosity in that engine. As for the experiment of Nédic et al (2009), using an engine similar to the one of this study, operating only on diesel, the behavior of the total base number was of continuous decrease, without the sharp reduction in the first hours of oil utilization that occurred in the present study.…”

“…Oxidation Naegele et al (2013) recommend 25 A cm; thus, the value on the second stage after 525 EOH is 12% higher than the limit recommended by Naegele et al (2013) although it is within the limit recommended by Oelcheck (2010).…”

“…Nédic et al (2009) and Naegele et al (2013) states that the total base number must be higher than 50% of the value of the new oil only if this value is higher than 2.0 mg KOH g -1…”

“…Aluminum is not added to lubricants as additive, so its presence in the sample of the new lubricant oil (3 ppm) must have come from the own oil used or caused by some type of contamination, possibly during transportation, storage or sampling. The limit value of aluminum for Otto cycle engines and gas Otto cycle engines listed in Naegele et al (2013) is 10 ppm; as for diesel cycle engines the value is 40 ppm. Therefore, all samples were under the limit for both specifications.…”

How Efficient are Agitators in Biogas Digesters? Determination of the Efficiency of Submersible Motor Mixers and Incline Agitators by Measuring Nutrient Distribution in Full-Scale Agricultural Biogas Digesters

“…Under mesophilic conditions, around 96 m 3 /h [standard temperature and pressure (STP)] of biogas are produced, with a composition of approximately 52% CH 4 , 48% CO 2 and 500 ppm hydrogen sulfide (H 2 S). This allows operation of the combined heat and power (CHP)-unit (six cylinder gas engine MDE MB3066 L4, MTU onsite energy, Augsburg, Germany) at nominal 192 kW electrical and 214 kW thermal power as described by Naegele [36]. After transformation, the electrical power is fed into the local energy grid.…”