KNF Recirculation Pumps for Efficient Fuel Cell Operation

The Benefits of Recirculation

Fuel cells and fuel cell systems are highly versatile and their actual power requirement varies depending on their intended area of use. However, fluctuating power loads harbor the risk of the anode being supplied with an insufficient amount of hydrogen.

This is where recirculation comes in. In this operating mode, the anode is steadily supplied with more hydrogen than it can consume. The unused hydrogen is recirculated and made available for the electrochemical reaction again. The anode receives a constant sufficient supply of hydrogen.

KNF Recirculation Pumps are Gastight

Each and every KNF recirculation pump is airtight as standard because they are manufactured without any dynamic seals. As an important and inherent part of the recirculation pump’s design, this gas tightness can be increased and adapted to individual requirements. Selecting metallic materials for the pump head is one way of improving the gas tightness. An excellent option for optimizing gas tightness offers the way how the KNF recirculation pump is connected to the anode inlet or anode outlet. KNF recirculation pumps can be connected to the fuel cell without hoses. Typical points of leakage are thus eliminated from the outset. In addition to increased gas tightness, the use of a manifold connection brings further advantages:

• saves space and as a result facilitates the integration of the gas-tight recirculation pump

• no material costs for hoses

Back to the list of benefits

KNF Recirculation Pumps are Maintenance Free

Fuel cells are so versatile that some of the places where they are used are difficult to access, making maintenance-free operation even more beneficial.

KNF’s range of recirculation pumps takes scenarios like this into account and features a selection of maintenance-free gas pumps for different flow rates.

At KNF, we place immense value on minimizing our products’ total cost of ownership (TCO). This means that whenever we configure recirculation pumps for high flow rates and the associated greater level of stress, we take care to ensure that they have long maintenance intervals and just a few wear parts that are easy to replace.

Back to the list of benefits

KNF Recirculation Pumps are Resistant to Hydrogen – Even When it is Moist

The materials used in KNF recirculation pumps – 316L stainless steel, anodized aluminum, EPDM and Viton – prevent the pumps from becoming brittle when in contact with hydrogen.

The recirculating excess gas has a different composition compared to the gas entering the anode path. Due to the electrochemical process, the gas needing to be recirculated comprises a mixture of hydrogen, nitrogen and water vapor. The materials used in KNF recirculation pumps enable them to withstand the high moisture this mixture contains.

Back to the list of benfits

KNF Recirculation Pumps are Energy Saving

As balance-of-plant components, recirculation pumps play a significant role in helping fuel cells to run economically. KNF recirculation pumps have been proven worldwide to only make a very low contribution to a fuel cell system’s overall power consumption.

This is due in particular to our own Digital Customization series brushless DC motors. These allow us to offer uniquely efficient drive solutions that work together with our pump components to achieve maximum performance. Current peaks, which are very stressful for the fuel cell system, can be avoided by using suitable motor parameters.

Back to the list of benefits

KNF Recirculation Pumps are Fully Parametrizable for Efficient Pump Curves

Fuel cell systems vary so significantly that there is no one-size-fits-all recirculation pump. KNF recirculation pumps feature our Digital Customization series motors, making them the ideal solution for the variety of conditions in which fuel cells are operated. At KNF, we develop and produce these brushless DC motors in house, allowing us to design our drive systems with our pumps’ requirements in mind right from the start of the process. We believe that motor performance is integral to the efficiency of our pumps, which is why we pay so much attention to getting our motors just right.

KNF recirculation pumps featuring our Digital Customization series motors are fully parametrizable:

• customized rotational speed control and control characteristics

• analog/digital on/off switch (remote on/off)

• communication via UART (digital), PWM signal or analog control voltage

• customized motor acceleration (start-up ramp)

KNF recirculation pumps provide a whole host of benefits for the efficient operation of fuel cells, including the following features to name just a few:

• application-specific current limit

• retrieval of real-time data and error messages

• blocking protection for the motor

Back to the list of benefits

KNF Recirculation Pumps are Customizable

Each of our series models can be custom-fit to the operating conditions thanks to KNF’s modular system. This also allows the IP protection class specified on the data sheets to be modified. In addition to the motors and materials, the connections and connecting systems are customizable. This also applies to conditions with which the KNF recirculation pump is to be tested before it is delivered to you.

Talk to our experts about your options! Moreover, we would be happy to provide you with a completed KNF recirculation pump assembly suitable for rapid installation.

We can also make the purchasing process easier by tailoring the packaging and logistics to your requirements.

Back to the list of benefits