Time filter

Source Type

Dietrich R.-U.,CUTEC Institute | Oelze J.,CUTEC Institute | Lindermeir A.,CUTEC Institute | Spitta C.,Zentrum fur BrennstoffzellenTechnik GmbH | And 5 more authors.
Journal of Power Sources

The transfer of high electrical efficiencies of solid oxide fuel cells (SOFC) into praxis requires appropriate system concepts. One option is the anode-offgas recycling (AOGR) approach, which is based on the integration of waste heat using the principle of a chemical heat pump. The AOGR concept allows a combined steam- and dry-reforming of hydrocarbon fuel using the fuel cell products steam and carbon dioxide. SOFC fuel gas of higher quantity and quality results. In combination with internal reuse of waste heat the system efficiency increases compared to the usual path of partial oxidation (POX). The demonstration of the AOGR concept with a 300 Wel-SOFC stack running on propane required: a combined reformer/burner-reactor operating in POX (start-up) and AOGR modus; a hotgas-injector for anode-offgas recycling to the reformer; a dynamic process model; a multi-variable process controller; full system operation for experimental proof of the efficiency gain. Experimental results proof an efficiency gain of 18 percentage points (η·POX = 23%, η·AOGR = 41%) under idealized lab conditions. Nevertheless, further improvements of injector performance, stack fuel utilization and additional reduction of reformer reformer O/C ratio and system pressure drop are required to bring this approach into self-sustaining operation. © 2010 Elsevier B.V. All rights reserved. Source

Dietrich R.-U.,CUTEC Institute | Lindermeir A.,CUTEC Institute | Oelze J.,CUTEC Institute | Spieker C.,Zentrum fur BrennstoffzellenTechnik GmbH | And 2 more authors.
ECS Transactions

Biogas is a renewable energy of growing importance to reduce greenhouse gas emissions of electricity generation. Solid oxide fuel cell (SOFC) systems can improve the efficiency of electrical power generation from biogas, especially at fluctuating biogas qualities and if the SOFC waste heat is used to produce high caloric SOFC fuel gas (hydrogen and carbon monoxide). This paper describes the system approach, upfront analysis, biogas monitoring results, process unit evaluation and system setup to demonstrate a high efficient biogas to electricity route using a commercial 1 kW SOFC stack. Dry reforming of methane with the carbon dioxide contained in biogas is a promising approach to produce high caloric SOFC fuel gas by using waste heat for additional SOFC power input. However, to avoid carbon formation during and downstream the reforming reaction additional supply of steam is essential. Efficient reforming catalysts for the combined dry and steam reforming process together with an appropriate reformer/burner-reactor design for adequate heat transfer from the anode offgas oxidation to the endothermic reforming reaction are required. Biogas of a sugar plant wastewater treatment facility will be used to demonstrate the feasibility of this new approach. The biogas has to be cleaned from sulfur components to avoid the poisoning of the reformer and fuel cell catalysts. The SOFC stack operates with the product gas from biogas dry and steam reforming. The appropriate system design has to be evaluated and later be implemented in the biogas plant. ©The Electrochemical Society. Source

Straczewski G.,Karlsruhe Institute of Technology | Voller-Blumenroth J.,RWTH Aachen | Beyer H.,Zentrum fur BrennstoffzellenTechnik GmbH | Pfeifer P.,Karlsruhe Institute of Technology | And 5 more authors.
Chemical Engineering and Processing: Process Intensification

Palladium membranes were prepared on large tubes (80mm diameter and 150mm length) of porous stainless steel supports (PSS) using a modified electroless plating technique. The morphology of the palladium layer was found to be depending on the container material of the coating apparatus. The use of PMMA resulted in compact palladium layers with smooth surfaces whereas PTFE led to inhomogeneous palladium coating with rough surface. Two different ceramic materials and coating methods were used to prepare an intermediate layer needed to prevent intermetallic diffusion between the palladium and the support at elevated temperatures. Wet powder spraying of TiO2 followed by sintering resulted in a smoother surface than atmospheric plasma spraying of YSZ, thus allowing for a thinner palladium coating. Pd/TiO2/PSS membranes showed about 4 times higher hydrogen permeances than Pd/YSZ/PSS membranes as a consequence of higher palladium thickness and lower porosity of the ceramic intermediate layer. The selectivity against nitrogen was comparable for both membranes. However, the YSZ intermediate layer showed better stability at elevated temperatures. Two membrane tubes were applied in the membrane reformer, which produced hydrogen successfully from a gas-to-liquid (GtL) fuel. © 2014 Elsevier B.V. Source

Dietrich R.-U.,CUTEC Institute | Oelze J.,CUTEC Institute | Lindermeir A.,CUTEC Institute | Spieker C.,Zentrum fur BrennstoffzellenTechnik GmbH | And 2 more authors.
Fuel Cells

A stand-alone system for power generation from biogas-based on a commercial SOFC module in the 1kWe range shall demonstrate its applicability to biogas, quantify the efficiency gain compared to conventional combined heat and power technology and justify further development toward SOFC modules in the hundreds of kilowatt range. The system includes biogas cleaning, combined dry and steam reforming, electrochemical oxidation of synthesis gas, offgas burning, and heat usage for steam generation and support of the endothermic reforming reaction. The system demonstrated a performance of 1kWe at 52% gross efficiency for a synthetic biogas containing 55vol.% CH4 during 500h in the lab. In addition, the performance using real biogas derived from the wastewater treatment process of a sugar plant was demonstrated for different operating points. Based on the experimentally validated results, it is possible to predict the benefit of operating larger SOFC biogas systems. Investment costs of 2.5 times compared to the conventional technology of a 75kWe biogas unit get paid off due to higher electricity revenues over time. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Schoemaker M.,Zentrum fur BrennstoffzellenTechnik GmbH | Misz U.,Zentrum fur BrennstoffzellenTechnik GmbH | Beckhaus P.,Zentrum fur BrennstoffzellenTechnik GmbH | Heinzel A.,Zentrum fur BrennstoffzellenTechnik GmbH
Fuel Cells

Gas crossover is an unavoidable phenomenon in proton exchange fuel cell membranes. Nitrogen and oxygen from the cathode pass through the membrane to the anode, while hydrogen crosses from the anode to the cathode. The hydrogen crossover leads to a reduction in efficiency due to parasitic hydrogen consumption and mixed potentials on the cathode electrode. Furthermore it causes degradation effects and pinhole formation. Hence the hydrogen crossover represents a fundamental factor for the lifetime of a fuel cell and quantification of the crossover is a key factor for membrane qualification. In this article two in situ electrochemical techniques to evaluate the hydrogen crossover are described, cyclic voltammetry and potential step method. Both methods and the achieved results are compared to each other. Finally the potential step method is applied to evaluate the hydrogen crossover as a function of the anode pressure and the hydrogen permeability coefficients are determined. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Discover hidden collaborations