Experimental and theoretical studies on adsorbed natural gas storage system using activated carbons 2

Appendix A Appendix A Determination of Regeneration Temperature for the Activated Carbons The regeneration temperature is applied to the adsorbent sample during the evacuation process to desorb the pre-adsorbed adsorbate molecules. The temperature has to be reasonably higher to provide enhancement in desorption process, although the maximum possible regeneration temperature depends on the adsorbent material properties particularly the burn off temperature. Generally the carbon materials burn out at temperatures from (650 to 750) °C in presence of air. However, the regeneration temperature for the activated carbons is observed to be much lower because of their porous surface structure. In this study, the regeneration temperature is determined experimentally for the activated carbon (AC) samples used in the experiments. The Computrac Max 5000 Moisture Analyzer is used for this purpose where the AC sample pre-adsorbed with methane is heated up at different higher temperatures. RTD mounted near the Heater to measure Oven Temperature Ceramic Oven Sample Holder Display Figure A.1 Computrac Max 5000 Moisture Analyzer 185 Appendix A This moisture analyzer operates for the temperature range of (25 to 600) °C and it takes only (2 to 3) minutes to reach the set temperature. The operating range is (0.2 to 600) g with an accuracy of 0.1 mg in mass measurement. Figure A.1 shows the pictorial view of the moisture analyzer indicating the ceramic oven, sample holder, RTD for temperature measurement, and the display. The AC samples pre-adsorbed with methane are heated up at different temperatures ranging from (100 to 300) °C, and the adsorbate removal rates are recorded as function of time. Figure A.2 provides typical plots for the percentage of adsorbate removed and the removal rate at temperatures 160 °C and 200 °C, respectively for the AC sample type Maxsorb III. In these plots, the “% Moisture” of the vertical axis should be considered as “the percentage of adsorbate removal”. It can be seen that the percentage of adsorbate removal from the AC sample becomes steady after about 20 minutes of heating at temperature 160 °C whereas it is gradually increasing in case of temperature 200 °C. These observations confirm that there is no significant adsorbate removal in the extended period of heating at 160 °C. However, the gradual increase of the percentage in case of heating at 200 °C is not exactly due to the adsorbate removal rather it is because of burn out of the AC sample. % of adsorbate removal is constant (a) 160 °C Figure A.2 % of adsorbate removal is gradually increasing (b) 200 °C The percentage and the rate of adsorbate removal as function of time 186 Appendix A Figure A.3 shows the bar plot for the ratio of final mass and initial mass of the Maxsorb III sample at different temperatures. It can be seen that the changes in mass ratio are sharp below 120 °C and they are very close (indicated by red circle) for the temperatures (140 to 180) °C. Again, the sharp changes in mass ratio (indicated by blue circle) are observed for temperatures above 200 °C which indicates the possibility of burn out of the AC sample at higher temperatures above 200 °C. Therefore, the regeneration temperature is estimated at temperatures (140 to 160) °C for the AC samples and this temperature range is also maintained in other studies (Himeno et al., 2002; Saha et al., 2007; Akkimaradi et al., 2009; Wang et al., 2010) when activated carbons are used as adsorbents. 0.992 Mass Ratio (mfinal/minitial) 0.990 0.9894 0.9877 0.988 0.9870 0.9867 0.9863 0.986 0.9858 0.9846 0.9840 0.984 0.9823 0.982 0.9800 0.980 0.978 100 120 140 160 180 200 220 240 260 280 Temperature ( °C) Figure A.3 The ratios of final mass and initial mass of the Maxsorb III sample at different higher temperatures 187 Appendix B Appendix B Experimental Adsorption Uptake Data Table B.1 Experimental uptake data for adsorption of methane onto Maxsorb III Pressure (MPa) Uptake (kg/kg) Temperature = ºC 0.050 0.127 0.217 0.310 0.411 0.510 0.646 0.784 0.934 1.138 1.340 1.550 1.754 1.949 2.158 0.015 0.033 0.050 0.066 0.080 0.093 0.109 0.123 0.136 0.152 0.167 0.180 0.191 0.201 0.211 Temperature =45 ºC 0.061 0.148 0.248 0.348 0.445 0.540 0.665 0.815 0.966 1.170 1.368 1.585 1.777 1.975 0.008 0.019 0.029 0.039 0.048 0.056 0.065 0.076 0.086 0.099 0.110 0.121 0.130 0.139 Pressure (MPa) Uptake (kg/kg) Temperature=15 ºC 0.050 0.135 0.233 0.331 0.429 0.526 0.655 0.800 0.946 1.155 1.354 1.561 1.762 1.968 2.166 0.012 0.029 0.045 0.059 0.071 0.082 0.096 0.109 0.121 0.137 0.150 0.163 0.174 0.184 0.193 Temperature=55 ºC 0.065 0.160 0.255 0.354 0.458 0.555 0.680 0.823 0.974 1.204 1.389 1.593 1.799 1.984 2.203 0.008 0.017 0.026 0.035 0.043 0.050 0.059 0.069 0.078 0.091 0.100 0.110 0.120 0.127 0.136 Pressure (MPa) Uptake (kg/kg) Pressure Uptake (MPa) (kg/kg) Temperature=25 ºC Temperature=35 ºC 0.057 0.140 0.234 0.331 0.428 0.526 0.652 0.792 0.948 1.157 1.344 1.563 1.756 1.960 2.157 0.011 0.025 0.038 0.050 0.061 0.071 0.083 0.095 0.108 0.122 0.134 0.147 0.157 0.167 0.176 Temperature=65 ºC 0.067 0.157 0.254 0.350 0.456 0.555 0.681 0.826 0.978 1.188 1.393 1.589 1.795 1.990 2.187 0.007 0.015 0.023 0.030 0.038 0.045 0.053 0.061 0.070 0.081 0.091 0.100 0.108 0.116 0.124 0.060 0.152 0.245 0.344 0.443 0.543 0.678 0.820 0.974 1.175 1.373 1.571 1.771 1.975 2.178 0.010 0.022 0.034 0.045 0.055 0.064 0.076 0.087 0.098 0.111 0.122 0.133 0.143 0.153 0.161 Temperature=75 ºC 0.071 0.162 0.263 0.362 0.464 0.561 0.686 0.835 0.987 1.198 1.401 1.603 1.806 2.015 2.198 0.006 0.013 0.020 0.027 0.034 0.040 0.047 0.055 0.063 0.073 0.083 0.091 0.099 0.107 0.114 188 Appendix B Table B.2 Experimental uptake data for adsorption of methane onto ACF (A20) Pressure Uptake Pressure Uptake Pressure Uptake Pressure Uptake (MPa) (kg/kg) (MPa) (kg/kg) (MPa) (kg/kg) (MPa) (kg/kg) Temperature = ºC 0.057 0.128 0.218 0.332 0.437 0.549 0.672 0.855 0.981 1.162 1.358 1.572 1.780 1.981 2.202 2.412 0.012 0.022 0.034 0.045 0.055 0.063 0.072 0.082 0.089 0.097 0.105 0.113 0.120 0.126 0.132 0.137 Temperature=45 ºC 0.062 0.157 0.261 0.354 0.452 0.561 0.694 0.845 1.001 1.206 1.414 1.602 1.804 2.038 2.230 2.394 0.006 0.014 0.021 0.027 0.032 0.038 0.044 0.051 0.057 0.065 0.072 0.078 0.083 0.090 0.094 0.098 Temperature=15 ºC 0.056 0.143 0.242 0.343 0.443 0.550 0.699 0.838 0.997 1.205 1.401 1.601 1.799 2.008 2.207 2.406 0.010 0.022 0.032 0.041 0.049 0.057 0.066 0.074 0.082 0.091 0.099 0.106 0.112 0.118 0.123 0.128 Temperature=55 ºC 0.051 0.157 0.254 0.360 0.453 0.562 0.711 0.854 1.005 1.200 1.407 1.609 1.803 1.995 2.198 2.416 0.004 0.012 0.018 0.024 0.029 0.034 0.041 0.047 0.053 0.059 0.066 0.072 0.077 0.082 0.087 0.091 Temperature=25 ºC 0.059 0.144 0.252 0.350 0.451 0.550 0.688 0.838 0.999 1.199 1.401 1.605 1.805 2.000 2.206 2.402 0.008 0.018 0.028 0.036 0.043 0.050 0.058 0.066 0.073 0.081 0.089 0.095 0.101 0.107 0.112 0.117 Temperature=65 ºC 0.067 0.147 0.249 0.358 0.457 0.551 0.702 0.861 1.009 1.203 1.403 1.599 1.833 2.005 2.236 2.403 0.004 0.009 0.015 0.020 0.025 0.029 0.035 0.041 0.047 0.053 0.059 0.064 0.070 0.074 0.080 0.083 Temperature=35 ºC 0.059 0.146 0.247 0.352 0.445 0.545 0.694 0.846 0.998 1.204 1.404 1.599 1.820 2.034 2.201 2.433 0.007 0.015 0.023 0.031 0.037 0.043 0.051 0.058 0.065 0.073 0.080 0.086 0.092 0.098 0.102 0.108 Temperature=75 ºC 0.059 0.151 0.249 0.346 0.445 0.544 0.723 0.850 1.027 1.198 1.403 1.603 1.825 2.001 2.199 2.402 0.003 0.008 0.013 0.017 0.021 0.025 0.032 0.037 0.042 0.048 0.053 0.058 0.064 0.068 0.072 0.075 189 Appendix B Table B.3 Pressure (MPa) Experimental uptake data for adsorption of methane onto Chemviron Uptake (kg/kg) Temperature = ºC 0.048 0.146 0.268 0.390 0.516 0.672 0.826 0.987 1.184 1.386 1.607 1.795 2.035 2.269 2.535 0.017 0.033 0.045 0.054 0.061 0.068 0.073 0.078 0.083 0.087 0.089 0.092 0.094 0.094 0.095 Temperature =45 ºC 0.060 0.157 0.292 0.413 0.527 0.684 0.875 1.066 1.276 1.462 1.705 1.925 2.141 2.374 2.609 0.009 0.018 0.028 0.034 0.039 0.045 0.051 0.056 0.060 0.063 0.067 0.071 0.073 0.075 0.077 Pressure Uptake Pressure Uptake Pressure Uptake (MPa) (kg/kg) (MPa) (kg/kg) (MPa) (kg/kg) Temperature=15 ºC 0.059 0.148 0.262 0.382 0.494 0.641 0.800 0.953 1.189 1.405 1.678 1.886 2.103 2.333 2.552 0.016 0.028 0.039 0.048 0.054 0.060 0.066 0.070 0.076 0.080 0.084 0.087 0.089 0.091 0.092 Temperature=55 ºC 0.069 0.178 0.264 0.394 0.503 0.664 0.836 0.998 1.230 1.438 1.688 1.906 2.127 2.343 2.575 0.008 0.017 0.022 0.029 0.033 0.042 0.047 0.051 0.055 0.058 0.063 0.066 0.068 0.071 0.073 Temperature=25 ºC 0.052 0.152 0.272 0.391 0.530 0.691 0.851 0.996 1.180 1.393 1.572 1.780 1.976 2.164 2.361 0.012 0.024 0.035 0.042 0.049 0.056 0.061 0.065 0.069 0.073 0.077 0.079 0.082 0.084 0.085 Temperature=65 ºC 0.064 0.177 0.288 0.388 0.508 0.668 0.814 0.998 1.227 1.565 1.857 2.136 2.399 2.614 0.006 0.015 0.021 0.025 0.030 0.035 0.039 0.043 0.049 0.055 0.060 0.063 0.066 0.068 Temperature=35 ºC 0.066 0.169 0.290 0.394 0.514 0.680 0.859 0.977 1.182 1.356 1.600 1.831 2.052 2.272 2.548 0.011 0.022 0.031 0.037 0.043 0.050 0.055 0.059 0.063 0.068 0.072 0.074 0.078 0.081 0.084 Temperature=75 ºC 0.072 0.180 0.285 0.385 0.504 0.632 0.775 0.950 1.193 1.410 1.647 1.882 2.132 2.356 2.624 0.006 0.013 0.018 0.022 0.027 0.031 0.037 0.041 0.046 0.050 0.053 0.057 0.060 0.062 0.065 190 Appendix C Appendix C Drawings and Dimensions of the Cryostat Figure C.1 Cryostat for the Adsorption Cell (Top View) The detail drawings and dimensions of the cryostat, which was built to maintain constant low temperature of the adsorption cell, are given below. Liq.N2 inlet line  130φ  Flange: ISO NW16KF Liq.N2 outlet line  All dimensions are in mm 191 Figure C.2 Cryostat for the Adsorption Cell (Front Sectional View) Appendix C 192 Figure D.1 SS 316L Top/Bottom Flange ASME DN300 CL300# S0.RF Water Inlet/Outlet Tube DN25 SCH40S Feed Through 3000# DN15 NPT Gas Inlet/Outlet Tube DN8 SCH80S Tube DN10 SCH80S SS 316L SS 316L SS 316L 32 SS 316L SS 316L Stud Bolts and Nuts 1-1/8" UNC 200mmL Paper based Rings Gasket Top/Bottom Cover ASME DN300 CL300# .RF SS 316L Asbestos Shell : Pipe DN300 SCH40S 1000mmL SS 316L Description Item Qty Material Appendix D Appendix D Drawings and Dimensions of the Storage Cylinder and AC Bed Heat Exchanger All dimensions are in mm Design Pressure 40 bar.g Design Temperature 90 °C Drawings and dimensions of the Storage Cylinder 193 Figure D.2 SS 316L Bottom Header (173mmx157mmx48mm) 5mmT SS 316L Divider at Top Header (147mm x 43mm) 5mmT SS 316L Water In/Out Tube (OD26mm x 2mmT) Header Flange and HX End Plate Connected with bolts and nuts SS 316L Top Header (173mm x 157mm x 48mm) 5mmT SS 316L Tube OD10mm x 1.0mm T x 810mmL Cu/Ni 20 x Fins (112 mmx112mm) x 0.1mmT Cu/Ni 94 Description Item Qty Material All dimensions are in mm Design Pressure 40 bar.g Design Temperature 90 °C Appendix D y z Drawings and dimensions of the AC Bed Heat Exchanger 194 Appendix E Appendix E Details of Leak Test of the Storage Cylinder and AC Bed Heat Exchanger The below is the Pressure Test Certificate provided by the manufacturer for the Storage Cylinder and the AC Bed Heat Exchanger 195 Appendix E The storage cylinder was tested in our laboratory for pressure keeping the heat exchanger inside the cylinder before activated carbon was packed. After the end covers bolted with the flanges, the cylinder was filled with water and pressurized up to 40 bar using the hydraulic pump. A slight pressure drop was observed after long hours which could be due to the room temperature fluctuations and also because of the sieving effect of water through the asbestos gaskets. Figure E.1 shows the pressure test arrangement for the storage cylinder. Figure E.1 Pressure test arrangement for the Storage Cylinder Figure E.2 Pressure test arrangement for the AC Bed Heat Exchanger 196 Appendix E Similarly, the AC bed heat exchanger was also tested for pressure in the laboratory after the activated carbon was packed. The heat exchanger was internally pressurized up to bar using the hydraulic pump and no pressure drop was observed for more than 12 hours. Figure E.2 shows the pressure test arrangement for the AC bed heat exchanger. To determine the leak rate, the storage cylinder assembly was pressurized with pure helium gas with the AC bed heat exchanger inside the cylinder. The pressure readings were recorded with time and the pressure versus time plot is shown in Figure E.3 which shows a slight pressure drop of about 0.1 bar in 16 hours. Since the charge and discharge processes are continued only for three hours, this leaking rate is considered negligible. However, it is taken into consideration in the simulation of the cyclic processes for the ANG storage system. Figure E.3 Leak test report of the Storage Cylinder charged with pure helium 197 [...]... with time and the pressure versus time plot is shown in Figure E.3 which shows a slight pressure drop of about 0.1 bar in 16 hours Since the charge and discharge processes are continued only for three hours, this leaking rate is considered negligible However, it is taken into consideration in the simulation of the cyclic processes for the ANG storage system Figure E.3 Leak test report of the Storage. .. with water and pressurized up to 40 bar using the hydraulic pump A slight pressure drop was observed after long hours which could be due to the room temperature fluctuations and also because of the sieving effect of water through the asbestos gaskets Figure E.1 shows the pressure test arrangement for the storage cylinder Figure E.1 Pressure test arrangement for the Storage Cylinder Figure E .2 Pressure... pressure in the laboratory after the activated carbon was packed The heat exchanger was internally pressurized up to 6 bar using the hydraulic pump and no pressure drop was observed for more than 12 hours Figure E .2 shows the pressure test arrangement for the AC bed heat exchanger To determine the leak rate, the storage cylinder assembly was pressurized with pure helium gas with the AC bed heat exchanger...Appendix E Appendix E Details of Leak Test of the Storage Cylinder and AC Bed Heat Exchanger The below is the Pressure Test Certificate provided by the manufacturer for the Storage Cylinder and the AC Bed Heat Exchanger 195 Appendix E The storage cylinder was tested in our laboratory for pressure keeping the heat exchanger inside the cylinder before activated carbon was packed After the end covers bolted with . 0. 120 1.799 0.1 12 1.805 0.101 1. 820 0.0 92 1.981 0. 126 2. 008 0.118 2. 000 0.107 2. 034 0.098 2. 2 02 0.1 32 2 .20 7 0. 123 2. 206 0.1 12 2 .20 1 0.1 02 2. 4 12 0.137 2. 406 0. 128 2. 4 02 0.117 2. 433 0.108 Temperature=45. 1. 825 0.064 2. 038 0.090 1.995 0.0 82 2.005 0.074 2. 001 0.068 2. 230 0.094 2. 198 0.087 2. 236 0.080 2. 199 0.0 72 2. 394 0.098 2. 416 0.091 2. 403 0.083 2. 4 02 0.075 Appendix B 190 Table B.3 Experimental. Temperature =25 ºC Temperature=35 ºC 0.057 0.0 12 0.056 0.010 0.059 0.008 0.059 0.007 0. 128 0. 022 0.143 0. 022 0.144 0.018 0.146 0.015 0 .21 8 0.034 0 .24 2 0.0 32 0 .25 2 0. 028 0 .24 7 0. 023 0.3 32 0.045