560 580

Figure 3 - Carbon Monoxide and Air vs Record No.

The ATR been tested at pressures from 1 to 2.5 atm.

Most of our operations have used low steam to carbon ratios because of the heat loss from the ATR. Heat loss limits the ATR's capacity to heat steam and air to partial oxidation temperatures. While the condition can be remedied by elevating the oxygen to carbon ratio, this hurts efficiency. Low hydrogen to carbon ratios in the ATR enhances coke formation, especially at elevated pressure., No coke formation has been experienced at low pressure. Since the ATR was rebuilt and the insulation was replaced, heat loss has been greatly reduced and operation at elevated pressure has been improved. The new USMC ATR design is expected to greatly reduce heat loss.

Figure 4 - ATR based Fuel Processor

We are concentrating on selective oxidation to reduce the carbon monoxide level from the fuel processor. Both the USN and USMC cell stacks have been operated successfully on the effluent from a natural gas fuel processor. However, the performance is somewhat erratic because of the relatively high levels of carbon monoxide leaving the sclcctivc oxidizer. Our most rcccnt results show improved selective oxidizer performance at temperatures of 350°F rather than the 180 to 250° F which were originally used. The higher temperature necessitates relocating the selective oxidizer from the position shown in Figure 4 to a point between the shift converter and condcnser. A sample of the effluent composition at various points in the fuel processor is presented in Table 1. The table shows the gas compositions from a diesel fuel reforming test, analyzed at the ATR or shift converter exit. The gas compositions, which are on a dry basis, were obtained with a gas Chromatograph which is part of the USN fuel processor test stand instrumentation.

The oxygen to carbon ratios shown in the table are quite high while the steam to carbon ratios are low. These conditions generally result in a reactor inlet temperature of about 2000°F. The high inlet temperature is required to get high conversions of diesel fuel to carbon oxides. The present system also suffers from a shift converter inlet temperature and, consequently, a high shift converter exit temperature. This results in a high carbon monoxide concentration at the shift converter exit.

Table 1

Fuel Processor Effluent Composition

Table 1

Fuel Processor Effluent Composition

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