Combined heat & power generation from natural gas is already a standard practice in the energy sector. What distinguishes your system from these conventional plants?
Combined heat & power plants convert natural gas into electricity using a combustion engine with additional utilization of the resulting waste heat. This task can be fulfilled much better in a coupled reformer-fuel cell system with modern catalytic converter technology:
- Without the emission of NOx
- Without the use of large moving engine components
- With lower maintenance
- With reduced noise emissions
Engine-based combined heat & power units have an optimum operating point, beyond which efficiency drops drastically. Unfortunately, many CHP units do not run at this load point. Because a fuel cell is less dependent on the system load, our system can work at partial load at high efficiency, unlike engine-based systems.
We are also highly focused on optimum performance combining the smallest possible size and the highest system efficiency by utilizing the energy contained in all process flows.
How do you achieve the high-power densities in your reformers?
The internal design of our reactors is optimized down to the last detail. The basic structure of an IMM reactor for steam reforming is that of a plate-heat exchanger. Its unique feature is that each plate is coated with a catalyst on both sides: biogas reforming takes place on one side, while heat recovery through catalytic combustion takes place on the other. The two reactions run in parallel, separated only by a thin metal layer—a few tenths of a millimeter. This leads to an extremely high heat transfer in the smallest possible space, supplying the energy for biogas reforming. As we know, this reaction is endothermic.
Catalysts are at the heart of every reformer - What makes the IMM catalyst different from conventional catalysts?
Nickel-based catalysts used in conventional natural gas reformers are inexpensive and available on a large scale. However they are only of limited use for small, decentralized systems. These catalysts are not particularly active - only a tiny proportion of the catalyst takes part in the reforming reaction, which is why large quantities are required.
In addition, these types of catalysts suffer from attrition when exposed to vibrations (such as those which occur when mobile systems are moving). Furthermore, they lose activity when not operated for long periods and tend to ignite spontaneously in contact with air. These characteristics make them unsuitable for decentralized, non-permanent applications. The IMM catalytic for biogas reforming has none of the problems. Moreover, it can convert biogas, synthetic and fossil natural gas. Not even the carbon dioxide contained in raw biogas needs to be separated, which also means that direct, efficient utilization is possible without the costly separation of carbon dioxide.
Fraunhofer Institute for Microengineering and Microsystems IMM