PONSSE FOREST MACHINES AND SCR ENGINE TECHNOLOGY

Transcription

1 PONSSE FOREST MACHINES AND SCR ENGINE TECHNOLOGY

2 CONTENTS 1. Emission standards tighten machines improve 2. Emission standards schedule 3. PONSSE SCR solution 4. Benefits of the SCR system 5. Performance and fuel efficiency 6. Customer comments

3 EMISSION STANDARDS TIGHTEN MACHINES IMPROVE New technology In brief, EGR (exhaust gas recirculation) involves recirculating a portion of an engine s exhaust gas back into the intake air and then to the engine cylinders. Fewer oxides are formed as exhaust gas replaces some of the oxygen, reducing the temperature of the combustion process. The drawback is poorer fuel economy in the combustion process. In addition to the EGR system, a diesel particulate filter (DPF) is needed for the exhaust system. The SCR (selective catalytic reduction) system, in turn, is based on the injection of DEF (diesel exhaust fluid) into the exhaust gas in the catalyst. In the SCR system, a chemical reaction reduces nitrogen oxide to harmless nitrogen and water vapour. The next Euromot and Tier levels will take effect in 2014, when the emission standards will be further lowered. This will require even more advanced technical solutions, such as combining the EGR and SCR systems. Emission standard schedule Euromot 3B / Tier 4i 130kW <130kW Euromot 4 / Tier 4 Final 130kW <130kW EPA <130kW EU FUTURE EMISSION STANDARDS For kw ( HP) engines Almost uniform legislation on emission standards in Europe and North America NOx Phase II EPA = North America EU = Europe Phase III a Phase III b Phase IV New standards The EU Euromot and North American Tier have set emission standards for nonroad diesel-powered work machines. The Euromot and Tier systems are harmonised in terms of emission standards, but they also differ in some significant respects. The main concern for emission standards are nitrogen oxides (NOx) and particulates. Phase I of Euromot and Tier 1 took effect in 1999 and 1996, respectively. The implementation of phase III and Tier 3 began in These levels were attained by adjusting the fuel injection and combustion of engines, which reduced the engine s efficiency and performance. The introduction of Euromot III b and Tier 4 in 2011 lowered NOx emissions by 50% and particle emissions by 90% from the previous Euromot III a and Tier 3 levels. These NOx levels necessitate new engine technology usually either an EGR or SCR system. Particle Phase II ja III a 50% decrease Phase III b ja IV 90% decrease % decrease

4 PONSSE SCR SOLUTION NH 3 + NOx >N 2 + H 2 O Motor Exhaust Catalytic converter Control unit Urea Air SCR technology (Selective Catalytic Reduction) SCR is a means to reduce the amount of nitrogen oxide (NOx) in exhaust gas. In the SCR system, the exhaust gas is mixed with air and a DEF (Diesel Exhaust Fluid) solution. DEF is a solution consisting of water and urea which, due to the heat of the exhaust gas, reduces nitrogen oxides (NOx) to harmless nitrogen and water vapour. The SCR system requires a catalyst, which is located in the exhaust silencer. Components of an SCR system: A heated DEF tank (heats up with the Webasto engine pre-heater thru engine coolant) A compressed air system comprising a compressor, tanks and a drier A DEF dosing unit A DEF injection system A catalytic converter (placed in the exhaust silencer) Piping 1. The pump unit injects the DEF using pressurised air. 2. The dosing unit mixes the DEF and pressurised air, and injects it in the exhaust gas system. 3. The heating valve lets the engine s radiator liquid to heat up the DEF tank. 4. The 25-litre DEF tank also has a temperature sensor and a level sensor. 5. Air compressor system, consisting of a dryer and two compressed air tanks.

5 BENEFITS OF THE SCR SYSTEM Better engine performance Excellent response to sudden loading of the engine. Engine reliability SCR reduces the engine s thermal load with a more optimal combustion process, which extends the service life of many engine components. Longer service intervals Servicing costs are reduced as the more optimised engine allows a longer service interval as compared with competing systems. Improved tolerance to fluctuations in fuel quality Easy to use and maintain Just add DEF when necessary. Neutralises harmful nitrogen oxides A significantly reduced climate impact Provides operators with a cleaner and safer work environment as well. Most large manufacturers of nonroad diesel engines have chosen the SCR method as the future technology with which to achieve the emission levels of Euromot 4 and Tier 4. Other aspects of the SCR system: The SCR system brings new components to the engine, which need to be serviced (change of filters). Diesel exhaust fluids (DEF) cost although not as much as fuel. The overall effect is positive, since the reduction in fuel consumption is greater than the consumption of DEF. The freezing point of DEF is -11 C, which should be remembered in relation to storage, transportation, and handling. Performance and fuel efficiency In addition to reduced emissions, the SCR system allows tuning the engine performance for optimal power, torque and fuel economy. Machine operators testify that an SCR engine responds much better to sudden loading, for example, when feeding a large tree. Nm RPM g/kwh Euromot 3A Euromot 3A Euromot 3B Euromot 3B RPM In an SCR engine, torque is greater than in an older engine of the same power. An SCR engine also responds to loading much better, which makes work smoother and faster when handling, for example, large trees. Nominal fuel consumption (grams of fuel consumed to produce one kwh of power) is lower for an SCR engine, thanks to its improved efficiency. This gives better fuel economy compared to Euromot III a and Tier 3 engines in similar conditions.

6 Customer comments The Savukoski-based company A&L Harju Oy was among the first to test Ponsse s SCR system also in winter conditions. It felt natural to start testing the new system in conjunction with a new machine. So far, the experiences have been quite positive indeed, says Lauri Harju. We ve had the new machine since December 2009, and for what amounts to approximately 7,500 hours. According to Lauri Harju, estimating the volume of fuel consumption is a very challenging task and it depends on a variety of factors. This machine is used mainly for clear cutting, in which case the consumption is approximately 14 litres an hour. But we cannot really compare fuel consumption as such, since our other machines have a different harvester head. The engine s improved efficiency, however, does receive praise. There seems to be more power. In other words, the stress is not as great as with a traditional engine. Whereas an SCR engine s power and consumption are praised, its capacity to withstand winter conditions has been questioned, since the urea solution added to the fuel freezes at -11 C. Having tested the SCR system in winter conditions, Lauri Harju s comments are frank. It does cause extra work. The solution has to be brought on site in an unfrozen and warm state. Outdoor storing is out of the question during winter. We add the AdBlue in the tank in conjunction with refuelling once a day, meaning that, thankfully, it does not require any separate work stages. Despite the required effort, Lauri Harju feels comfortable with the new system. I wouldn t go so far as to criticise the system. After all, we will all face this sooner or later, as the standards become tougher. The additional refuelling requires some extra work and the additional cost brought on by AdBlue is not welcome either. On the other hand, the engine s maintenance and other servicing has not changed. A&L Harju Oy Lauri Harju, entrepreneur PONSSE Ergo 6w, ajettu 7500 h C4 crane, H6 harvester head Hannu Liikanen ja and Jussi Tenhunen Karttulan Metsätyö has positive experiences with the SCR engine. Engine operators are particularly pleased with the delivery of power and the difference to the previous engine is considerable. The machine s wood intake is much better than before. There is also plenty of power to be found when smoke prevention no longer diminishes power when the engine is loaded. The engine doesn t sputter and feeds very well, even with big trees the run to the cutting point is a quick job, says Jussi. Consumption does not differ considerably from previous engines in other respects, but the old engine used to consume about one litre more per hour when clear-cutting and handling big trees. The fuel consumption of the new engine is about ,5 l/h when clear-cutting, and l/h when thinning. The engine is run on relatively high rpm s ( rpm) Hannu states that this way the consumption per hour might be higher, but calculated per produced cubic meters it is lower. The customer find the power delivery so much better that the next machine that the company will buy will also have an SCR engine. Karttulan Metsätyö Hannu Liikanen (entrepreneur, operator) Jussi Tenhunen (operator) PONSSE Ergo 6w, 1200 h C4 crane, H6 harvester head

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