• Energy Research

AbstractDesulfurization of biogas is essential for its application in solid oxide fuel cells. The influence of CH4, CO2, H2, and O2 as well as the effect of moisture onto desulfurization performance of an activated carbon, an adsorbent based on a CuO‐MnO mixture, and a zeolite adsorbent were analyzed. The use of moisturized gas had no negative influence on the H2S adsorption performance of activated carbon. The CuO‐MnO sorbent showed the best performance, but the presence of moisture had a negative influence. The performance of zeolite dropped for three gas mixtures, while for two other mixtures moisture had little to no influence on H2S adsorption performance.

This paper presents the development of the subsystems for stationary biogas powered solid oxide fuel cell (SOFC)-based combined cooling, heat and power (CCHP). For certain applications, such as buildings, a heat-driven operation mode leads to low operating hours per year for conventional combined heat and power (CHP) systems due to the low heat demand during the summer season. The objectives of this study are the evaluation of an adsorber, a steam reformer, a SOFC, and an absorption chiller (AC). Biogas, however, contains impurities in the form of hydrogen sulfide (H2S), hydrogen chloride (HCl), and siloxanes in different concentrations, which have a negative effect on the performance and durability of the SOFC and, in the case of H2S, also on the catalyst of the steam reformer. This paper describes different experimental sections: (i) the biogas treatment with its main focus on H2S separation and steam reforming, (ii) the setup and start-up of a 10 cell SOFC stack, and (iii) test runs with an AC using a mixture of NH3 (ammonia)/H2O (water). The components required for the engineering process of the subsystem's structure are described in detail and possible options for system design are explained. The evaluation is the basis to reveal the improvement potentials, which have to be considered in future product developments. This paper aims at comparing experimental data of the test rigs to develop an understanding of the requirements for a stable and continuous operation of a SOFC-based CCHP operated by biogas.

AbstractThe generation of electrical energy from biogas is state of the art. One option is the application of fuel cells for generating electrical energy. Due to their construction, the materials used and their mode of operation, solid oxide fuel cells (SOFCs) are particularly suitable. The primary problem in the operation of SOFCs using biogas is H2S. The goal of this work is to investigate the possible effects of ammonia on different sorbents that have already successfully been used for the desulfurization of biogas. The H2S adsorption capacity of four commercially available sorbents in the presence of NH3 was investigated as well as the influence of an upstream NH3 removal. The CuO‐MnO‐based sorbent showed the best performance related to sulfur uptake.

The desulfurization of biogas is essential for the successful operation of solid oxide fuel cells. H2S is one of the main components in biogas. In order to feed a solid oxide fuel cell, the contaminated gas has to be reduced to a certain degree. In this work, different parameters onto the desulfurization performance of commercially available desulfurization adsorbents were investigated. The experiments were carried out using a custom made lab-scale unit. Synthetic biogas was passed through the sorbent bed and the outlet H2S concentration was measured. Experimental runs in a fixed bed reactor were conducted to monitor H2S removal efficiency of a zinc oxide adsorbent, an adsorbent based on a mixture of manganese and copper oxide and a zeolite adsorbent. H2S removal efficiency was monitored under various operating conditions such as different temperatures, space velocities and inlet concentrations. This work provides useful data for adsorption tower design and process optimization.

In order to reduce the toxic effect on solid oxide fuel cells performance caused by biogas contaminated with hydrogen chloride and hydrogen sulphide, the purification of biogas is essential. Adsorptive gas purification is a highly auspicious technology to provide pollution-free biogas for solid oxide fuel cell-based power units. In this work the authors examined the influence of different parameters onto the adsorption capacity of three commercially available sorbents. Experimental runs in a laboratory glass downflow fixed-bed reactor were carried out to analyse the adsorption capacity of a potassium carbonate impregnated activated carbon and two sorbents based on a mixture of aluminium oxide and silicon dioxide. Hydrogen chloride removal was accomplished with the impregnated activated carbon and metal oxide-based sorbents. Hydrogen chloride adsorption capacity was analysed under space velocities 8000 and 16,000 h−1. In addition, the effect of a hydrogen chloride inlet concentration of 100 and 1000 ppmv was investigated. Furthermore, pellets in the size of 3–4 mm in diameter were crushed into a fraction between 500 and 1000 µm to investigate the influence of particle size on hydrogen chloride adsorption capacity. Additionally, the combined adsorption of hydrogen chloride and hydrogen sulphide was realized using the impregnated activated carbon. The experimental runs and the results obtained in this work provide useful data for designing an adsorption reactor to clean up biogas and optimizing the process.