Conversion of natural gas and other light hydrocarbons via steam reforming is currently the major process for hydrogen production. However, conventional hydrogen production technologies are not cost effective and therefore, cost is the biggest impediment to use hydrogen in fuel cell applications. In order to optimize and overcome cost problems in hydrogen production, sorption and membrane enhanced reaction processes are the two novel technologies for in situ operation of reforming and removal of carbon dioxide.
Adsorption of carbon dioxide onto activated hydrotalcite and activated soda, obtained from either trona or NaHCO3, had been studied using a stainless steel packed bed tubular reactor as a function of temperature. Adsorption of CO2 in the presence and absence of steam onto activated hydrotalcite was conducted in the temperature range of 400-527 oC, whereas sorption studies with activated soda were performed for 80 to 152 oC in the presence of steam. Also, two-parameter deactivation model was developed to justify the experimental data and predictions of the breakthrough curves by deactivation model indicated a good agreement with the experimental results. In order to obtain physical properties of the sorbents, untreated and calcined sorbents were characterized by using TGA, B.E.T (N2 adsorption), and Hg porosimetry techniques.
When hydrotalcite was used as the sorbent, total adsorption capacity of the material reduced from 1.18 mol/kg to 0.66 mol/kg as the temperature was increased from 400 oC to 527 oC. On the other hand, activated soda exhibited a total adsorption capacity 1.15 to 0.68 mol/kg for a temperature change from 80 to 152 oC.
For high temperature removal of CO2, hydrotalcite and its promoted forms (using K2CO3 or Na2CO3) are pretty good sorbents to be used in single step hydrogen production processes, such as SERP. On the other hand, activated soda could also be used for CO2 abatement of the effluent gas from the reformer only when the temperature is lowered enough to obtain efficient adsorption capacity within the multi-bed adsorbers.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12605346/index.pdf |
| Date | 01 August 2004 |
| Creators | Ficicilar, Berker |
| Contributors | Dogu, Timur |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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