Feed mixing board

The heart of the system is a microreactor packaging scheme that is based upon a commercially available microchip socket. This approach allows the silicon-based reactor die, which contains dual parallel reaction channels with more than 100 electrical contacts, to be installed and removed in a straightforward fashion without removing any fluidic and electronic connections. Various supporting microreactor functions, such as gas feed flow control, gas feed mixing, and various temperature control systems, are mounted on standard CompactPCI electronic boards. The boards are subsequently installed in a commercially available computer chassis. Electrical connections between the boards are achieved through a standard backplane and custom-built input-output PC boards. A National Instruments embedded real-time processor is used to provide closed-loop process control and... 

Metering of the individual reactor feed gas constituents to generate the desired feed gas composition actually occurs on dedicated feed gas mixing boards located within the AIMS chassis. The process elements contained on this board are shown within the dashed sub-region in Fig. 12.6. 

The feed gas mixing board indicated in Fig. 12.6 actually contains three parallel manifolds that control the process gas flow rates using a Redwood Microsystems (Redwood MicroSystems, Inc., 959 Hamilton Ave., Menlo Park, CA, 94025) MEMS-Flow MFC and three Redwood Microsystems normally closed Shut-Off... 

Fig. 12.7 (a) Right-hand side of the feed gas mixing board, showing the cables for the feed gas controls, (b) Left-hand side of the feed gas mixing board, which shows the various feed gas manifolds. 

Each reactor board has two separate connections where reactor feed gas can be introduced from the feed manifold. These connections serve as independent feed inlet points for two parallel Redwood Flow Manifolds (RFMs) that are used to control the gas flow rate to each channel of the microreactor die. A total of four microreactors can be operated since each die has two independently controlled reaction channels. The RFMs are identical to those used for the feed gas mixing board except for their inlet and exit operating pressures. 

The raw GC data was converted into compositional data using the internal standard method with either N2 or Kr as the reference species. Once the species compositions were determined, values for the reactant conversion, product selecti-vities, and product yields were evaluated using the standard expressions. Errors in these parameters were calculated by closing the mass balance on the reaction. This was done by comparing the feed gas composition with the measured product gas compositions. Large errors in the mass balance (> 5%) were indicative of physical problems with the system, which were typically attributed to leaks. Smaller errors (< 5%) were caused by uncertainties in the GC molar response factors as well as fluctuations in flow rates of the MFCs on the Feed Gas Mixing Board. 

---