Removal of H2S and Siloxane D5 by adsorption method from anaerobic digestion gas for solid oxide fuel cell

Abstract

Global warming and depletion of fossil fuel enhances people to obtain alternative clean source of energy. The purpose of this Master's Thesis was to study the sulphur and siloxanes removal by an adsorption method from the anaerobic digestion gas (ADG) by adsorbents for a solid oxide fuel cell (SOFC) application. The target limit for removal of H2S and siloxane compounds were less than 1 ppmv and 100ppbv respectively for the SOFC application.

Based on the results of this thesis work (this thesis is a part of a European Union project named SOFcom) and some other projects of SOFcom. a pilot plant of SOFC (capacity is 100 kW fuel energy) will attempt to operate using the ADG produced from the Torino Sewage Plant, Italy. As the temperature of raw biogas from the anaerobic digester of waste water treatment plant-was 40"C and atmospheric pressure, the literature review was also performed to obtain the best adsorbents to remove these impurities in the target condition (40°C and 1 atmosphere) and level.

From literature review, ZnO, zeolite 4A and impregnated AC were determined the best adsorbents for H2S removal and molecular sieve, activated carbon and silica gel were the best adsorbents for siloxane removal. Different types of siloxanes were available in the ADG, among them D5 was chosen as representative for their higher concentrations (1200ppbv). Commercially available adsorbents such as Activated Carbon (sigma), Zeolite 5A, FCOS GS-1 (ZnO) and FCDS GS6. Active carbon (Norit RST3) and Soxsia were used in this thesis.

The best adsorption capacity for sulphur and siloxane removal were 48 mgs / gFCDS GS1 and 55.7 mgD5 / gNorit RST3 found in this research. The diameter and bed height of the two adsorber bed for the pilot plant for producing 100 kW fuel energy ZnO and active carbon will be 19 cm/ 0.5m and 35 cm/1m respectively.