Author(s):
Robert Hamburger -
Bloomy Controls
Establishing System Requirements for Fuel Processing Systems
A fuel cell is an electrochemical device that combines hydrogen and oxygen (from air) to produce electricity, heat, and water. Fuel cells operate without combustion, making them virtually pollution free. Because hydrogen is not yet easily accessible for these applications, catalyst-based fuel processing systems (FPS) are necessary to create hydrogen from fuels commonly available today such as gasoline and natural gas.
HydrogenSource, a joint venture between United Technologies Fuel Cells Corp. (UTCFC) and Shell Oil Company, develops, manufactures, and sells fuel processors and hydrogen generation systems for the fuel cell and hydrogen fuel markets. Currently, HydrogenSource is involved in research and engineering efforts to evaluate the performance of FPS catalysts and related components.
These studies employ experimental chemical reactors that require the control and monitoring of a large number of process parameters, such as temperature, flow, pressure, and gas composition, for periods ranging from a few minutes to several months. Previous manual monitoring methods proved extremely labor-intensive, with susceptibility to human error and the inability to provide either the quantity or quality of data required.
We at Bloomy Controls specified, designed, and implemented a series of systems that would facilitate automated operation and data collection to support HydrogenSource’s newly constructed FPS laboratory. This lab is a research facility that requires flexible instrumentation and controls because the tests performed in each reactor significantly vary from one experiment to another, and at the time we designed the system, we had not defined all of the planned experiments fully. The application was especially challenging because the requirements demanded that pairs of reactors share crucial pieces of expensive analytical instrumentation.
We successfully fulfilled the requirements of a system design capable of easy reconfiguration for different experiments, collection of large volumes of data while maintaining continuous process control, and accommodating a wide range of sensors, transducers, and controls.
Implementing a Flexible, Efficient SCXI Platform
Our dual reactor hardware configuration is representative of a typical component layout for controlling a pair of catalyst reactors. Each reactor has its own control PC, and inside each reactor is an E-Series DAQ card interfaced to an associated SCXI chassis. Through these SCXI capabilities, we acquire a combination of temperatures, pressures, flow rates, and process alarms. The relatively large number of various parameters, each requiring different methods of signal conditioning, combined with the need to capture signals at fast acquisition speeds for transient measurements, made SCXI the ideal platform for these systems. DIN rail mounted connector and terminal blocks provide easy-to-wire connection points for the various types of sensors, transducers, and actuators.
Through an RS-485 interface, we control a high-power PID temperature controller, and a series of intelligent mass flow controllers via serial communications commands. A third PC acts as a shared resource server, communicating through RS-485 with a 32-loop PID temperature controller, motion control module, NDIR spectrometer, and motorized sampling valve. We employ a combination of LabVIEW Datalogging and Supervisory Control (DSC) Module network tags and VI server links, communicating via the lab’s conventional Ethernet connections, so each of the individual reactor PCs acts as a client by sending commands to and receiving data from the server.
Through our architecture, HydrogenSource can control each reactor independently, while simultaneously sharing common lab resources.
Using the LabVIEW DSC Module to Design Flexible Software Components
FPS catalyst experiments typically include a sequence of timed steps, with process parameters either held at constant values or linearly ramped to desired settings, while data reflecting the system’s performance is collected. We created a sophisticated recipe-driven architecture to give experimenters the flexibility to define and run a wide range of test protocols. Using the LabVIEW DSC Module, we wrote the two major software components comprising this system, Recipe Editor and Automation Engine.
The first component of the system is a Recipe Editor with a front panel. Each step in an experimental test includes attributes, such as the duration of the step in seconds, set points to each controlled process parameter, definitions of high and low alarm values, and recipe sequence controls such as holding and looping. In any step, if the user executes the Hold function, the recipe pauses at the end of the step. Pressing the Continue button resumes automatic recipe sequencing. With the capability for program looping, the user can select the desired step to which to loop back, as well as the number of loop repetitions. Additionally, we designed the system so users can enter simple descriptive text for each step for documentation. Intuitive editing commands, including Insert, Delete, Go To Next Step, Go To Previous Step, provide fast and easy recipe editing. The recipe stores in a modified Windows style .ini format – a header section contains keys describing overall system settings, including number and kind of each type of parameter, number of steps, etc, while sections of the format each contain the detailed values for the respectively numbered recipe step.
The second major software component is the Automation Engine. This VI’s front panel includes all current values of the various parameters in the system, along with descriptive recipe information previously listed. With mode control buttons, users can easily operate the system – start execution of the selected recipe, pause in the current recipe step, immediately advance to next step, or abort execution of the current recipe. In addition, the Automation Engine contains a virtual manual controls panel, providing manual set point overrides on a channelper- channel basis for all controlled values. With this function, users have the option of modifying individual parameter values, independent of the current formula, to fine tune or interact manually with the process. We also use a mixture of acquisition methods to make efficient use of the available hardware resources. We wrote a custom serial server to control the mass flow controllers and other analytical instrumentation, while Lookout protocol drivers facilitate serial Modbus RTU communication with the external PID controllers. All set point and measured parameters log to a Citadel database through the LabVIEW DSC Module tag engine. We manage the SCXI hardware through programmatic DAQ commands to accommodate both slow and fast acquisition modes. During steady-state experiments, users can write SCXI channels to memory tags. If users need sampling rates in excess of 100 Hz, they can write data directly to a conventional spreadsheet file. With the flexible extraction tools and the LabVIEW DSC Module native historical trend viewer, users benefit from straightforward data mining and viewing of collected data. These utilities complement the automation system’s capabilities for managing and examining data.
Delivering Increased Efficiency
Several versions of this system have operated successfully at HydrogenSource for more than a year, and researchers now are conducting complex and lengthy experiments with minimum of user intervention. We estimate that these automation systems using National Instruments products have cumulatively saved in excess of 10,000 man hours of manual control, monitoring, and data collection. Our Bloomy Controls solution has helped HydrogenSource to stay in the forefront in the development of fuel processing technologies for fuel cells, leading to the next generation of clean and efficient electrical power sources.
For more Information on this case study, contact:
Peter Blume, President
Bloomy Controls, Inc.
839 Marshall Phelps Road
Windsor, CT 06095
Tel: (860) 298-9925
Fax: (860) 298-9535
E-mail: info@bloomy.com
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