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Special Systems
Published in Carl Bozzuto, Boiler Operator's Handbook, 2021
The most common engine in a boiler plant is normally the emergency generator. Environmental regulations, developed under Environmental Protection Agency’s (EPA) Tier 4 requirements, have changed the procedures for operating engines. Those requirements apply to all land-based equipment, whether stationary or mobile. Some operators are bound to be familiar with requirements for adding diesel exhaust fluid (DEF) into a separate reservoir of a diesel engine powered pickup truck. New emergency generators and stationary diesel engines will also have that requirement. They will be fitted with catalyzed diesel particulate filters (CDPFs) that capture the engine’s particulate emissions, which are principally unburned hydrocarbons. Then they burn off the carbon while simultaneously reacting to break down nitrogen oxides using a catalyst alone or the DEF. To achieve the emission limits now established, engines will also have control features added to augment positive crankcase ventilation (PCV) and exhaust gas recirculation (EGR) valves. Because the implementation of Tier 4 regulations are progressing, there will likely be additional modifications to normal engines that will become normal in the coming years. Once again, read the instruction manual. Additional environmental requirements may be dictated by the US EPA regulations under the reciprocating internal combustion engine (RICE) maximum achievable control technology (MACT) rules. Be sure to understand all of the requirements, including reporting and documentation.
Special Systems
Published in Kenneth E. Heselton, Boiler Operator’s Handbook, 2020
Environmental regulations developed under EPA’s Tier 4 requirements have changed the procedures for operating engines. Those requirements apply to all land based equipment whether stationary or mobile. Some of you are bound to be familiar with requirements for adding DEF (diesel exhaust fluid) into a separate reservoir of your diesel engine powered pickup truck. New emergency generators and stationary diesel engines will also have that requirement. They will be fitted with CDPFs (catalyzed diesel particulate filters) that capture the engine’s particulate emissions, which are principally unburned hydrocarbons, then burn off the carbon while simultaneously reacting to break down nitrogen oxides using a catalyst alone or the DEF. To achieve the emission limits now established engines will also have control features added to augment PCV and EGR valves. Because the implementation of Tier 4 regulations are progressing as I work on this edition I can’t tell you about all the modifications to normal engines that will become normal in the coming years. Once again, read your instruction manual.
Sustainable Heavy Construction Equipment
Published in J.K. Yates, Daniel Castro-Lacouture, Sustainability in Engineering Design and Construction, 2018
J.K. Yates, Daniel Castro-Lacouture
In 2014, the EPA fully implemented its Tier Four Final Standards, which were part of the phase in of the multi-tiered emissions reduction process that started in 1996 to reduce PM and NOx emissions by 90%. As of result of the Tier Four requirements, manufacturers have created CEGR and SCR systems for heavy construction equipment. Selective catalytic reduction systems use higher combustion temperatures and urea-based diesel exhaust fluid (DEF) after treatment. Cooled exhaust gas recirculation systems mix the exhaust gases with fresh air before recirculating it. A DPF is still required to filter soot. Meeting Tier Four requirements adds an additional 25% to the cost of the equipment. In addition, the engines are more sensitive to water, dust, and extreme temperatures. They may require low-ash engine oil, ULSD fuel, and an extra fuel filtration system (Engineering News Record 2014a).
Evaluation of heavy-duty vehicle emission controls with a decade of California real-world observations
Published in Journal of the Air & Waste Management Association, 2021
Chris Ruehl, Chandan Misra, Seungju Yoon, Jeremy D. Smith, Mark Burnitzki, Shaohua Hu, John Collins, Yi Tan, Tao Huai, Jorn Herner
In contrast to DPFs, SCRs have not reduced NOx emissions to levels expected based on in-use compliance thresholds (Figure 4b) under the Not-to-Exceed (NTE) regulation. This threshold typically applies to less than a third of all NOx emissions and about a tenth of all engine operation time (Dixit et al. 2017; Tan et al. 2019), however, as the NTE limits only apply under certain operating conditions, e.g., when exhaust temperature is below 250°C, or when engine power or torque is below certain thresholds. There are many possible reasons for this lower-than-expected NOx reduction, including low SCR temperature (e.g., Misra et al. 2013), insufficient dosing of diesel exhaust fluid (Opitz et al. 2015), poor maintenance/tampering (e.g., Belser 2020), and catalyst deterioration (Schmeig et al. 2012).
Experimental mitigation of NO x emission in exhaust gases of CI engine fuelled with methyl ester of cottonseed oil blend
Published in International Journal of Ambient Energy, 2020
G. Balaji, K. Suresh Kumar, M. Cheralathan
The Vanadium-based catalyst with 100 CPSI is used in this present study. Medium-temperature V2O5-based catalysts will be operating in between the temperature range of 260°C and 450°C. This has the obvious advantage of a wider temperature window compared to other catalyst like Platinum (Pt). NOx alteration happened at about 225°C, rises to about 400°C, and then falls as the degree of ammonia oxidation begins to dominate. The discrimination is gone above about 425°C. Ad Blue solution is a non-toxic liquid and colourless in appearance and is a solution of water and urea. Ad Blue (Urea) is a 32.5% by weight solution of urea and water combined. It is non-explosive, non-flammable and will not affect the environment. Ad Blue is also called as Diesel Exhaust Fluid or aqueous urea. Ad Blue solution changes the harmful NOx from diesel vehicle exhaust and converts into nitrogen and steam vapour which is harmless gas to the environment. Reducing the nitrogen oxides (NOx) from emissions is the major achievement to avoid atmospheric pollution. Ad Blue solution is produced from a high purity urea. Ad Blue solution requires a corrosion resistant plastic tank and it is separate from diesel tank. This Ad Blue solution tank with injector was installed before the SCR catalyst and mixer is also incorporated to mix the injected urea with the exhaust gases together (Cho et al. 2017).
Trends in onroad transportation energy and emissions
Published in Journal of the Air & Waste Management Association, 2018
Higher NO2/NOx ratios favor lower temperature SCR conversion of NOx to N2. A urea solution, referred to as “diesel exhaust fluid” (DEF), is injected upstream of the SCR reactor, which releases ammonia (and some CO2) that mixes with the exhaust gas. Ammonia reacts with NO and NO2 to form N2 and H2O. The ASC is designed to selectively oxidize ammonia to N2 without creating excessive amounts of N2O or NOx (Walker 2016).