scholarly journals Performance and Regeneration of Methane Oxidation Catalyst for LNG Ships

2021 ◽  
Vol 9 (2) ◽  
pp. 111
Author(s):  
Kati Lehtoranta ◽  
Päivi Koponen ◽  
Hannu Vesala ◽  
Kauko Kallinen ◽  
Teuvo Maunula
Keyword(s):  
Methane Oxidation ◽  
Sulfur Poisoning ◽  
Oxidation Catalyst ◽  
Lean Burn ◽  
Marine Fuel ◽  
Efficient Catalyst ◽  
Worst Case ◽  
Exhaust Temperature ◽  
Unintended Effect ◽  
Methane Slip

Liquefied natural gas (LNG) use as marine fuel is increasing. Switching diesel to LNG in ships significantly reduces air pollutants but the methane slip from gas engines can in the worst case outweigh the CO2 decrease with an unintended effect on climate. In this study, a methane oxidation catalyst (MOC) is investigated with engine experiments in lean-burn conditions. Since the highly efficient catalyst needed to oxidize methane is very sensitive to sulfur poisoning a regeneration using stoichiometric conditions was studied to reactivate the catalyst. In addition, the effect of a special sulfur trap to protect the MOC and ensure long-term performance for methane oxidation was studied. MOC was found to decrease the methane emission up to 70–80% at the exhaust temperature of 550 degrees. This efficiency decreased within time, but the regeneration done once a day was found to recover the efficiency. Moreover, the sulfur trap studied with MOC was shown to protect the MOC against sulfur poisoning to some extent. These results give indication of the possible use of MOC in LNG ships to control methane slip emissions.

Dynamic Estimation Method of Effective Active Site on Palladium Methane Oxidation Catalyst in Exhaust Gas of Marine Lean Burn Gas Engine

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Yoshifuru Nitta ◽  
Yudai Yamasaki
Keyword(s):  
Active Sites ◽  
Oxidation Process ◽  
Estimation Method ◽  
Oxidation Catalyst ◽  
Pd Catalyst ◽  
Exhaust Gas ◽  
Maritime Industry ◽  
Ch4 Oxidation ◽  
Lean Burn ◽  
Exhaust Temperature

Abstract Lean-burn gas engines have recently attracted attention in the maritime industry, because they can reduce NOx, SOx, and CO2 emissions. However, since methane (CH4) is the main component of natural gas, the slipped methane, which is the unburned methane, likely contributes to global warming. It is thus important to make progress on exhaust after-treatment technologies for lean-burn gas engines. A Palladium (Pd) catalyst for CH4 oxidation is expected to provide a countermeasure for the slipped methane, because it can activate at lower exhaust temperature comparing with platinum. However, a de-activation in higher water (H2O) concentration should be overcome because H2O inhibits CH4 oxidation. This study was performed to investigate the effects of exhaust temperature or gas composition on active Pd catalyst sites to clarify CH4 oxidation performance in the exhaust gas of lean-burn gas engines. The authors developed the method of estimating effective active sites for the Pd catalyst at various exhaust temperatures. The estimation method is based on the assumption that active sites used for CH4 oxidation process can be shared with the active sites used for carbon mono-oxide (CO) oxidation. The molecular of chemisorbed CO on the active sites of the Pd catalyst can provide effective active sites for CH4 oxidation process. This paper introduces experimental results and verifications of the new method, showing that chemisorbed CO volume on a Pd/Al2O3 catalyst is increased with increasing Pd loading in 250–450 °C, simulated as a typical exhaust temperature range of lean-burn gas engines.

Sulfation of a PdO(101) methane oxidation catalyst: mechanism revealed by first principles calculations

2019 ◽  
Vol 9 (1) ◽  
pp. 232-240 ◽  
Author(s):  
Ryan Lacdao Arevalo ◽  
Susan Meñez Aspera ◽  
Hiroshi Nakanishi
Keyword(s):  
Catalytic Activity ◽  
Methane Oxidation ◽  
First Principles ◽  
Sulfur Poisoning ◽  
Oxidation Catalyst ◽  
First Principles Calculations ◽  
Oxidation Of Methane

PdO efficiently catalyzes the oxidation of methane but suffers tremendously from sulfur poisoning that lowers its catalytic activity.

scholarly journals Study with Micro-reactor on Deactivation of Pd Methane Oxidation Catalyst for Marine Lean Burn Gas Engines

2019 ◽  
Vol 54 (5) ◽  
pp. 765-772
Author(s):  
Yoshifuru Nitta ◽  
Yasuhisa Ichikawa ◽  
Koichi Hirata ◽  
Yudai Yamasaki
Keyword(s):  
Methane Oxidation ◽  
Oxidation Catalyst ◽  
Lean Burn ◽  
Micro Reactor

Investigation of the Combustion Performance in a Three-Nozzle RQL Combustor

2016 ◽  
Author(s):  
Bing Ge ◽  
Yongbin Ji ◽  
Shusheng Zang ◽  
Yongwen Yuan ◽  
Jianhua Xin
Keyword(s):  
Air Flow ◽  
Lean Burn ◽  
Uniformity Coefficient ◽  
Performance And Emission ◽  
Combustion Performance ◽  
Sector Model ◽  
Exhaust Temperature ◽  
Whole Process ◽  
Axial Temperature ◽  
Two Peaks

RQL (Rich-burn/Quick-quench/Lean-burn) is a candidate to support fuel flexible stationary power generation. The equivalence ratio of rich-burn zone (Φr) and the quench air flow are paramount for implantation of the whole process. In this paper, an experimental test stand with multi-sector model combustor was established. Rich premixed combustion were used in rich zone. The experiments which pay attention to the impacts of Φr and quench air flow on the combustion performance and emission are conducted. The results show that the flame in RQL combustor is segmented when Φr >1.4, presenting flameless combustion in rich zone and a pale blue flame in lean zone. Axial temperature distribution is M-type. Two peaks appear at the head and tail of the combustion chamber, and the valley is located in the quench zone. The concentration of CO decreases rapidly in quench zone because of the injection of quench air. However, the concentration of NOx increases quickly at the same time. The outlet emissions of CO and NOx in RQL combustor are maintained at low level (<20ppm@15%O2). With a decrease of Φr from 1.4 to 1.2, the emission of NOx increases, and the emission of CO decreases. With jet-to-mainstream mass-flow ratio increases from 1.28 to 2.22., the concentration of NOx in outlet declines gently, but the CO emission increase. The average exhaust temperature depresses gradually, and the uniformity coefficient of exhaust temperature increases.

scholarly journals Development of Pre-Turbo Catalyst for Natural Gas Engines

2003 ◽  
Author(s):  
Thierry Leprince ◽  
Joe Aleixo ◽  
Kamal Chowdhury ◽  
Mojghan Naseri ◽  
Shazan Williams
Keyword(s):  
Natural Gas ◽  
Greenhouse Gas ◽  
Turbine Blades ◽  
Catalyst Design ◽  
Oxidation Catalyst ◽  
Sudden Increase ◽  
Natural Gas Engines ◽  
Exhaust Temperature ◽  
Distributed Power Generation ◽  
Conversion Efficiencies

Distributed power generation is an efficient method for reducing CO2 emissions through the elimination of transmission losses. Co-generation has similar benefits with higher thermal efficiency. Natural gas engines are very popular for these applications. Unfortunately, these engines emit significant levels of methane, which is a greenhouse gas. Reduction of methane emissions would greatly improve the environment and provide greenhouse gas emissions credits. The exhaust temperature downstream of the turbocharger in a natural gas engine is typically below 500°C. At these temperatures, methane is difficult to oxidize with current oxidation catalysts. It would be a much better option to install the oxidation catalyst before the turbocharger where temperatures are 100–150°C higher. Pressures upstream of the turbocharger are higher than downstream and also affect catalyst conversion efficiencies. Misfiring events are common in natural gas engines. During misfiring events, the catalyst will see a sudden increase in hydrocarbon (methane). When this pulse of hydrocarbon hits the catalyst, it will be oxidized and generate a large exotherm which could lead to catalyst failure (mechanical and/or chemical). This issue is critical for a pre-turbo catalyst: 1) Mechanical failure of the catalyst could lead to catastrophic turbocharger failure, a result of the turbine blades being damaged. 2) Misfiring with catalyst installed before the turbocharger is more likely to ignite the methane pulse because of the higher temperatures in this location. High exotherms from ignition could negatively affect catalyst performance. Through careful catalyst design, one can minimize this risk and this paper will address these issues.

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