Energy systems for a greener future

Areas of expertise

The Energy Technology and Catalysis Department at Fraunhofer ICT-IMM covers the entire technology chain, with expertise in the areas of catalyst development and stability testing, process simulation, system design and control, development of cheaper fabrication techniques, reactor construction and complete system integration and testing (Figure 1). With a staff of 20 people, the group can be considered as one of the largest for fuel processing development in Europe.

Figure 1

Complete portfolio of services provided.

In addition to the development of single components and complete fuel processing systems for conventional and regenerative fuels, other business interests lie in the fields of liquid hydrogen technology, exhaust gas treatment systems and biofuel syntheses. The microstructured and microchannel reactors, together with the integrated catalysts therein, allow for the realization of compact and consolidated systems, which is crucial for both mobile and stationary applications. A performance range from 100 W to over 100 kW can be covered.

Microstructured plate heat exchanger reactors open new opportunities for heterogeneously catalyzed gas phase reactions with respect to enhanced heat and mass transfer, resulting in shorter residence times via an intelligent coupling of endothermic and exothermic reactions, or even cooling functions. However, processing steps other than the generation of hydrogen can benefit from this integrated coupling. Process steps further downstream, such as water gas shift, preferential oxidation and selective methanation of carbon monoxide, are required to yield hydrogen to the required level of (hydrogen) purity. Meanwhile, the number of successfully demonstrated applications is numerous, especially when one includes bio-based feedstocks as potential, processable feedstock, as illustrated in Figure 2. Of course, processing of logistic fuels such as methane, methanol, ethanol, Liquefied Petroleum Gas (LPG) and diesel are also very active working fields.

Figure 2

Renewable routes for energy and fuel production based on chemical synthesis routes.

Power supply of recreational vehicles by LPG based fuel cell auxiliary power units (APUs)

In such applications, the major technical challenges are the compactness and reliability of the fuel processor, which is a combination of several catalytic processes. The system works as a battery charger for recreational vehicles with a maximum electrical power output of 250 W (Figure 3). LPG consumption is in the range of 90–100 g/h. The system is characterized by an efficient demand-oriented charging and load management, as well as an autonomous fully automatic operation. Due to its efficient power conversion, low exhaust emission and low noise operation, the technology is environmental friendly.

Figure 3

LPG based power supply (A) APU for recreational vehicles; (B) 250 W complete fuel processor.

Development of a compact plant for the production of biodiesel from different feedstocks under supercritical reaction conditions

Today, biodiesel is blended with diesel fuel at an amount of 7% and heating oil at an amount of 20%. In diesel fuel, it replaces the previously lubricating sulfur compounds and leads to a significant reduction of CO₂ emission by almost 70%. The production of biodiesel from vegetable oils according to the conventional, homogeneously base catalyzed process has a number of drawbacks, such as large reactor size, sensitivity against free fatty acids and water, low purity of the side product glycerol (further use, e.g., in cosmetics industry), complicated wastewater treatment, large wastewater quantities and product separation issues. By applying microstructured reactors to a heterogeneously catalyzed process operated under supercritical conditions, decentralized production can be realized reducing the wastewater generation compared to conventional technology, while minimizing the energy demand.

The basic fabrication techniques

The fabrication of the fuel processor begins with the introduction of microchannels into stainless steel metal foils. For rapid prototyping, microstructuring techniques such as micromilling can be used. However, for future mass production, the application of more established and cheaper techniques, such as wet chemical etching embossing, punching and rolling are preferred.

In the sense of an ongoing optimization and automation of individual manufacturing processes, the fabrication of catalyst coatings needs to be improved. Whereas wash-coating of catalysts or wash-coating of the carrier with subsequent wet impregnation, chemical and physical vapor deposition are well-established techniques, higher throughput has been achieved by the establishment of screen printing techniques (Figure 4A). The high temperatures required for the catalytic conversion of hydrocarbons to hydrogen demand for stainless steel as construction material. Thus, mechanical precision engineering and laser welding play important roles in the fabrication process.

Whereas the delivery of highly precise microstructured elements by means of 3D CNC/Ultra Precision (UP) machining, wire and bulk electro discharge machining, as well as wet chemical etching, is to a large extent straightforward, high standard localized welding seams allowing for sealing of a reactor consisting of catalyst coated plates and capable of operation at high temperatures have proven to be a major challenge. For this purpose, a specially adopted laser welding process has been developed at Fraunhofer ICT-IMM. Connections and tubings are later attached. A 50/150 W pulsed Nd:YAG laser as well as a 1 kW CW disc laser are the core machines in this regard (Figure 4B).

The integration of these techniques for complete system production paves the ground for the mass production of microreactors. While many steps still need to be optimized, the outlook is encouraging. However, only with the active cooperation of strategic partners can a real increase in production volumes be achieved via the ensuing benefits accruing from economies of scale. In all probability, this will involve the continued targeting of important and financially viable early and niche markets for implementation.

Figure 4

Fabrication techniques (A) Production of catalytic coatings by screen printing; (B) 1 kW CW disc laser.

Selected currently active projects in the area of expertise

BIOGO: Catalytic Partial Oxidation of Bio Gas and Reforming of Pyrolysis Oil (Bio Oil) for an Autothermal Synthesis Gas Production and Conversion into Fuels; FP7-NMP-2013-LARGE-7; Grant 604296-2 (coordinated by Fraunhofer ICT-IMM).

FCGEN: Fuel Cell Based On-board Power Generation; FCH-JU-2010-1; Grant 277844.

SUPRA-BIO: Sustainable products from economic processing of biomass in highly integrated biorefineries; FP7-2009-BIOREFINERY-CP; Grant 241640-2.

IRMFC: Development of a Portable Internal Reforming Methanol High Temperature PEM Fuel Cell System; FCH-JU-2012-1; Grant 325358.

About Fraunhofer ICT-IMM

On September 18, 2013, the former Institut für Mikrotechnik Mainz GmbH became part of the Fraunhofer Gesellschaft zur Förderung der angewandten Forschung e.V. Since the beginning of 2014, the new name is Fraunhofer ICT-IMM. Although the general framework and appearance have changed, the mission remains the same: developing together with and for industry customized system technology solutions in complex problem areas, thus, building a bridge between basic research and application. Pursuing well-proven strengths and identifying new trends at an early stage have been the guarantors of success since the foundation. Main areas of expertise are decentralized and mobile energy technology, continuous chemical process technology (flow chemistry), microfluidic analytical systems, medical probes, technical sensors and microtechnology for nanoparticles.