SCR under pressure - pre-turbocharger NOx abatement for marine 2-stroke diesel engines

Transcription

1 SCR under pressure - pre-turbocharger NOx abatement for marine 2-stroke diesel engines CIMAC Congress paper no.: 111, Helsinki 2016, prepared by Sandelin/Peitz

2 Emission control areas for sea going vessels SOx limits established, NOx limits only in some ECAs 2 Source: DNV GL

3 Emission control areas for sea going vessels New ECAs are under consideration 3 Source:

4 Emission control for 2-stroke diesel engines a multi-variable equation Operation profile: Fuel flexibility: Fuel availability: Common approach: Sailing pattern Running hours (ECA/non-ECA) Sulphur limit Scrubber or low sulphur fuels New fuel properties with < 0.1% S fuels What and where to bunker Same solution to be used for propulsion engine and gen sets? Picture: Langh Tech 4

5 NOx control solutions for 2-stroke engines Exhaust gas recirculation (EGR) + Low space requirement + Can be designed for fuel flexibility + Yards choice with respect to installation space - Limited suppliers - Common technology with gen sets - By-products 5

6 Different NOx control solutions for 2-strokes Low pressure SCR is installed down stream turbo. picture: Doosan + Conventional selective catalytic reduction (SCR) technology + Equipment common with gen sets + No space requirement in engine room - Only low sulphur fuels - Requires urea decomposition unit and a heating/regenerating device/strategy 6

7 Different NOx control solutions for 2-strokes High pressure SCR is installed upstream turbo. + Fuel flexible. It can be combined with scrubbers. + Reducing agent system common for gen sets + Part of the engine - Challenging pressurized piping - Sophisticated temperature control - Multi turbocharging a challenge 7

8 High pressure pre-turbo SCR systems WinGD s HP-SCR references available source: ferrypics.com 1999, 2000 M/V Spaarneborg M/V Schieborg M/V Slingeborg 3x7RTA-52U kw each 2015 M/V Papuan Chief 5RT-flex58T-D kw 2016 «Suezmax tankers» 2xW6X kw each Lesson learned: exhaust temperature the most important process parameter for the operation of the HP-SCR 8

9 Exhaust temperatures before and after turbo Variable temperatures before turbo Exhaust gas temperature before turbocharger Property/Load % Pressure before turbine bar Temperature [ C] Exhaust gas temperature after turbocharger Temperature before turbine Pressure after turbine Temperature after turbine C bar C Exhaust pressure before turbine [bar absolute] Source: GTD, W6X72 9

10 SCR limiting temperatures Many factors influence the temperature window for operation 1. Limit due to reducing agent decomposition (min) 2. DeNOx catalyst performance limits (min, max) 3. Catalyst endurance limit (max) 4. Stickiness of soot, lubrication oil residues and unburned hydrocarbons (min) 5. Stickiness of ash (min, max) 6. Dew point of ammonium sulphate salts (min) 7. Deactivation limit due to ammonium sulphate salts (min) TI Lee et al 2015 TI TI 10

11 Ammonium sulphates The bulk dew point can be calculated. It is changing with pressure Gas 4.3 bar 1.0 bar Condensed 11

12 Ammonium sulphates Pore condensation decreases activity, bulk condensation «fouls» it Catalyst cell opening: typically 3 to 5 mm Pore size: extent of 10-5 mm Catalyst channel Catalyst wall 0.5 mm Picture: T. N. White: Duke / WPCA NOx Seminar

13 Ammonium sulphates Catalyst activity decreases if the exhaust temperature is too low k = ln(m out /m in )/residence time pcat=2.6 bar Trec=345C Tcat_in=330C Tcat_out=336 Deactivation Pressure [bar] [bar] 13

14 Ammonium sulphates Catalyst activity restored when temperature is increased k = ln(m out /m in )/residence time pcat=2.6 bar Trec=345C Tcat_in=330C Tcat_out=336 pcat=3.3 bar Trec=380C Tcat_in=370C Tcat_out=373C Deactivation Reactivation Pressure [bar] [bar] 14

15 Ammonium sulphates SCR pore condensation/deactivation temperature can be calculated -6-7 in condensed form Operation point Deactivation Operation point Reactivation -8 log K in gas form Temperature [ C] Rule of thumb: T bulk = 310 * 14 * ln (S fuel *p 2 ) T pore = 340 * 14 * ln (S fuel *p 2 ) 15

16 Summary NOx abatement for Marine 2-stroke Diesel Engines available NOx legislation is in place since January 2016 New ships with two-stoke engines sailing in NECA areas need to control their NOx emissions according to Tier III SOx limits are in place at the same time in the NECA Exhaust gas recirculation, low- and high pressure SCR are potential NOx abatement technologies High pressure pre-turbo SCR is fuel flexible and is suitable when burning residual fuels. Good engine temperature management and prediction of ammonium sulphate salt condensation allow successful operation of the engine together with HP-SCR: With distillate and residual fuels and At high and low engine loads 16

17 Thank you! Co-Author: Daniel Peitz of WinGD; Martin Elsener and Oliver Kröcher of the Paul Scherrer Institute for the good collaboration. This project has received funding from the European Union s Horizon 2020 research and innovation programme under grant agreement No , HERCULES II. 17

18 Ammonium sulphates Bulk and pore condensation temperature change along the catalyst Dew point [ C] NH 3 [ppm] Reducing agent concentration Catalyst length Exhaust flow direction 18

19 Emissions regulation by IMO Table 1 Emission standards, geographic areas and emission limits that apply to low speed two stroke engines. Pollutant Area Rule Geographic area Emission limit NOx NECA Marpol Annex VI Tier III SOx SECA Marpol Annex VI North America US Caribbean North Sea Baltic Sea North America US Caribbean 3.4 g/kwh 0.1 % Sulphur fuel INTERNAL/EXTERNAL USE 19 WinGD, January 2016, SCR under pressure CIMAC Paper 111/2016 / Sandelin, Kristoffer

20 SCR under pressure Figure 2 5RT-flex58T two stroke engines test bed results 25 NOx as NO 2 [g/kwh] NOx after engine NOx after SCR E3 weighted Test points [% load] INTERNAL/EXTERNAL USE 20 WinGD, June 2016, SCR under pressure CIMAC Paper 111/2016 / Sandelin, Kristoffer

21 SCR under pressure Figure1 5RT-flex58T two stroke engines. 21 WinGD, June 2016, SCR under pressure CIMAC Paper 111/2016 / Sandelin, Kristoffer