# Development of a Novel De-NOX Technology for the Aftertreatment of Ship Exhaust Gases
## 2 Materials and Methods
### Pilot Unit Description  
The ship's exhaust gaseous stream consisted of (on average) 380 ppm SO\({}_{2}\), 623 ppm NO and 250 mg/m\({}^{3}\) of PM while its temperature (at the inlet of the sea-water scrubber) was approximately 120 \({}^{\circ}\)C. The pilot unit was designed in such a way in order to use an exhaust gaseous feed stream of 10 L/min (taken directly from the main exhaust pipe of the ship, after the turbocharger). The pilot unit was installed at the upper part of the funnel (top deck) of the ship. Figure 1 shows the exact position of the installed integrated pilot unit. Figure 2 presents a flowchart of the treatment units used for the ship's gaseous stream. As can be seen in Figure 2, the ship's exhaust feed stream is lead to the first stage of gas treatment which is the Sea Water Absorption (SWA) unit. The purpose of this unit is to remove SO\({}_{2}\) from the feed stream. The unit's operation is considered to be of great significance since SO\({}_{2}\) is considered to be a strong catalytic poison, as it chemisorbs irreversibly on the catalytic active sites blocking the supported met \begin{table}
\begin{tabular}{c c c} \hline \hline
**Property** & **Units** & **Value** \\ \hline Density @15 \({}^{\circ}\)C & kg/m\({}^{3}\) & 977.4 \\ Viscosity @ 50 \({}^{\circ}\)C & mm\({}^{2}\)/s & 99.8 \\ Water & vol.\% & 0.1 \\ Micro Carbon Residue & wt.\% & 11 \\ Sulfur & wt.\% & 1.47 \\ Ash & wt.\% & 0.05 \\ Vanadium & mg/kg & 77 \\ Sodium & mg/kg & 20 \\ Aluminum & mg/kg & 11 \\ Silicon & mg/kg & 15 \\ Iron & mg/kg & 29 \\ Nickel & mg/kg & 29 \\ Calcium & mg/kg & 17 \\ Magnesium & mg/kg & 4 \\ Lead & mg/kg & \textless{}1 \\ Zinc & mg/kg & 1 \\ Flash Point & Deg. C & \textgreater{}70 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Fuel quality analysis for the HFO used by MS Sapphire during the experiments of the present work. Figure 1: Position of the pilot-unit installed on MS Sapphire. A schematic representation of the SO\({}_{2}\) scrubber (SWA) unit used in the present work is shown in Figure 3.  
After the SWA treatment, the gaseous stream is lead to a mist eliminator where the removal of water vapor occurs. The stream is then reheated to 300 \({}^{\circ}\)C (with the use of heating tapes) and led to the third stage of gaseous treatment which involves the removal of PM with the use of an oxidative catalyst (a metallic universal oxidation catalyst provided by \"Cats & Pipes Ltd.--Holywell, UK\"). The removal of PM from the feed stream is an important step in order to protect the catalytic surface (de-NO\({}_{\rm x}\) catalyst) from the deposition of particulates (mainly soot) and thus maintain a high catalytic activity. The gaseous stream resulted from the latter treatment process was then mixed with H\({}_{2}\) which was produced by a distilled water electrolysis unit (Parker Balston 100 cc/min UHP Hydrogen Gas Generator--H2 PEM-100, 99.995% H\({}_{2}\) purity). The water consumption of the electrolysis unit was 0.75 L/week (water quality--ASTM2). The hydrogen production from the unit was 100 cc/min, which was fed to the reaction stream at the inlet of the SCR unit. The whole unit was designed in such a way so as to have the temperature of the inlet gas to the SCR unit reach about 200 \({}^{\circ}\)C. The H\({}_{2}\)-SCR reactor temperature is of great importance since, according to the literature, the supported catalyst used presents the highest selectivity towards N\({}_{2}\) and significant NO conversion at temperatures within the range of 150-400 \({}^{\circ}\)C [10]. The solid catalyst used in the de-NO\({}_{\rm x}\) unit was in the form of  
Figure 3: Schematic representation of the scrubber (Sea Water Absorption (SWA) unit), used on board for the reduction of SO\({}_{2}\). (1) Exhaust gas stream outlet, (2) sea water inlet, (3) the SWA tower, (4) exhaust gas stream inlet, (5) sea water outlet, (6) filling material. Figure 2: Flowchart showing the separate sub-units used for the complete depollution of examined ship’s gaseous emissions.