Non-thermal plasma system for marine diesel engine emissions control

Air pollutants generated by ships in both gaseous and particulate forms, have a long term effect on the quality of the environment and cause a significant exposure risk to people living in proximities of harbors or in neighboring coastal areas. It was recently estimated, that ships produce at least 15% of the world’s NOx (more than all of the world’s cars, buses and trucks combined), between 2.5 - 4% of greenhouse gases, 5% black carbon (BC), and between 3-7% of global SO2 output. Estimation of contribution of maritime shipping to global emissions of VOC and CO is not yet available. In order to reduce the environmental footprint of ships, the International Maritime Organization (IMO) recently issued the legislation of Marpol Annex VI guidelines which implies especially the introduction of, inter alia, stricter sulphur limits for marine fuel in ECAs under the revised MARPOL Annex VI, to 3.50% (from the current 4.50%), effective from 1 January 2012; then progressively to 0.50 %, effective from 1 January 2020, subject to a feasibility review to be completed no later than 2018. The limits applicable in Emission Control Zones (ECAs) for SOx and particulate matter were reduced to 1.00%, beginning on 1 July 2010 (from the original 1.50%); being further reduced to 0.10 %, effective from 1 January 2015. The Tier III controls apply only to the specified ships built from 2016 while operating in Emission Control Areas (ECA) established to limit NOx emissions, outside such areas the Tier II controls apply. The United States and Canada adopted national regulations enforcing IMO Tier III equivalent limits within the North American ECA effective 2016. The US Environmental Protection Agency (EPA) rule for Category III ships, however, references the international IMO standards. If the IMO emission standards are indeed delayed, the Tier III standards would be applicable from 2016 only for US flagged vessels. One of the proposed solutions towards marine diesel emission control is the non-thermal plasma process. We designed and built a non-thermal plasma reactor (NTPR) using a combination of Microwave (MW) and Electron Beam (EB) for treatment of marine diesel exhaust gas. A numerical model has been developed to better understand the marine exhaust gas/plasma kinetics. The reactor modelling and design can sustain 10kW of combined MW and EB power with a gas flow rate of 200l/s. The removal of NOx and SOx was continuously monitored using a portable dual Testo gas analyzer system while all other parameters (MW power, EB power, gas temperature/flow rate, etc.) were remotely recorded & stored through a Labview DAQ system. The reactor performance in NOx and SOx removal will be tested on a 200 kW two stroke marine engine. This study is a part of the DEECON (Innovative After-Treatment System for Marine Diesel Engine Emission Control) FP7 European project.The work was supported by the European Commission under DEECON FP7 European Project "Innovative After-Treatment System for Marine Diesel Engine Emission Control", contract No. 284745

NO Abatement using Microwave Micro Plasma Generated with Granular Activated Carbon

The micro-plasma is generated using granular activated carbon (GAC) particles of size (2-3mm) in loosely fluidized bed in a microwave cavity operated at 2.45GHz. A single mode microwave cavity reactor (SMMCR) was constructed and microwave was injected through another slotted single mode waveguide in a sandwiched manner. COMSOL Multiphysics software was used to investigate the microwave electric field and the power density within the SMMCR. Gas mixture of air and 500 ppm NO (in N2) at the flow rate of 2 l/min was passed through a quartz tube centered within the SMMCR while the supplied microwave power was very low 10-80 W and corresponding NO reduction was greater than 98%. The mass of GAC used for generating the plasma was 5g. The efficiency of NO reduction is found to be 24.84 g(NO2)/kWh. When air is mixed with NO (in N2), the efficiency of NOx reduction achieved vary greatly with respect to the supplied microwave energy and behavior has become complex and is not predictable, which needs further investigation. A gas analyzer (testo 350) was used to measure the gas (NO, NO2, CO and O2) concentration and temperature.Marine Exhaust Gas Treatment System (MAGS) grant reference number 42471-295209

Temperature profile of packed-bed non-thermal plasma reactor and its effect on toluene decomposition

This study aims to profile real plasma temperature inside the packed-bed (PB) non-thermal plasma (NTP) reactor using a fiber Bragg gratings (FBG) and its effect on toluene decomposition efficiency. PB reactor was designed and fabricated by packing some dielectric material of barium titanate (BaTiO3) pellets between two stainless steel electrodes. The FBG was embedded inside the reactor to measure the plasma temperature within the plasma stream. Plasma temperatures for four carrier gases, helium (He), argon (Ar), nitrogen (N2), and air were profiled at different applied voltages ranging between 4 and 16 kV based on their breakdown voltage to determine suitable gases for toluene decomposition process that has good temperature stability and no arc formation. For noble gases He and Ar, the plasma temperatures are in the range of 25-80°C and 60-170°C, respectively, while those of N2 and air are in the range of 28-200°C. Air was selected as carrier gas for toluene decomposition process due to higher plasma temperature, no arc formation and higher free oxygen radicals in the plasma stream. The results show that the plasma temperature increases with the increase in applied voltage, and with the decrease in flow rate and toluene input concentration. The average plasma temperature for toluene decomposition in air is in the range of 100-260°C when measured under applied voltage of 14-19 kV, carrier gas flow rate of 1.0-2.0 L/min and toluene input concentration of 500-8400 ppm. Complete toluene decomposition efficiency has been achieved under plasma parameters of 18 kV, 2.0 L/min and 500 ppm. From this finding, plasma temperature profiling using FBG sensor can be used as plasma diagnostic tool to replace Fourier Transform Infrared spectroscopy (FTIR) instrument and as indicator when toluene decomposition process is complete

Investigation and optimisation of a plasma cathode electron beam gun for material processing applications

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.This thesis describes design, development and testing work on a plasma cathode electron beam gun as well as plasma diagnosis experiments and Electron Beam (EB) current measurements carried out with the aim of maximising the power of the EB extracted and optimising the electron beam gun system for material processing applications. The elements which influence EB gun design are described and put into practice in a thermionic EB gun case study. The relevant principles of plasma EB gun systems, such low-temperature, low-pressure, RF excitation, are described along with the test rigs developed to investigate different plasma cathode configurations. The first experimental setup was for optical spectroscopy measurements of the light emitted from the plasma and the second included current measurements from EBs generated at –30 and –60 kV as well as the spectroscopic measurements. Comparison of EB current measurements with different plasma cathode configurations and correlation with spectroscopic measurements are presented. The maximum current extracted from the Radiofrequency (RF) gun was 38 mA at –60 kV using a hollow cathode geometry and permanent magnets for electron confinement. The RF gun was compared to a Direct Current (DC) gun which generated higher currents. This was reflected in the spectra which indicated a higher ionisation level than in the RF plasma. Simulation work carried out using Opera-2d to model beam trajectories indicated that the beam shape is largely influenced by the plasma boundary. Particle In Cell (PIC) simulations of a parallel plate RF plasma cathode demonstrated that higher excitation frequencies produced higher ionisation, however the RF sheaths were larger and thus the current extracted may be limited in practice due to fewer electrons being available near the aperture. The sheath thickness decreased in the simulations as the discharge gap was increased. RF plasma also produced larger currents from larger plasma chambers.TWI Ltd