TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: If the controller determines that the concentration of the sulfur-containing compounds in the fuel exceeds first predetermined concentration based on temperature outputs from the first and second temperature sensors, the controller determines whether the concentration of the sulfur-containing compounds in the fuel exceeds a second predetermined concentration (800 ppb), greater than the first predetermined concentration, based on whether the difference between temperature outputs from the first and second temperature sensors decreases at a second predetermined rate (4.4 degrees C/day) greater than the first predetermined rate. If the controller determines that the concentration of the sulfur containing compounds in the fuel exceeds the second predetermined concentration, the controller activates an escalated alarm and performs predetermined escalated actions. The predetermined escalated actions include controlling the flow of fuel to components of the fuel utilization system to inhibit the fuel flow, controlling the flow of fuel to the fuel utilization system to inhibit the fuel flow and ceasing operation of the fuel utilization system. The fuel flow controller and the water flow controller control the flow of fuel and water to provide humidified fuel with a steam to carbon (S/C) ratio of 1.3-3.0 to the sulfur breakthrough detector. The controller further controls the flow of the humidified fuel so that space velocity of the humidified fuel through the reforming catalyst bed is 30,000-120,000/hr and superficial velocity of the humidified fuel through the reforming catalyst bed is 7-60 cm/sec. The third temperature sensor is designed for sensing the temperature of the fuel after the fuel is conveyed through the reforming catalyst bed. The controller further receives temperature outputs from the second and third temperature sensors, and determines whether the humidified fuel flow through the sulfur breakthrough detector is sufficiently high and stable by determining whether the difference between the temperature outputs from the second and third temperature sensors is smaller than the first predetermined amount and whether the difference between the temperature outputs from the second and third temperature sensors varies by more than the second predetermined amount. The controller further determines whether concentration of the sulfur-containing compounds in the fuel exceeds the first predetermined concentration only if the controller determines that the difference between the temperature outputs from the second and third temperature sensors is smaller than the first predetermined amount and that the difference between the temperature outputs from the second and third temperature sensors does not vary by more than the second predetermined amount. The deoxidizing catalyst bed is disposed in series with the reforming catalyst bed so that the fuel is first conveyed through the deoxidizing catalyst bed and then through the reforming catalyst bed. The controller includes: a first temperature controller for receiving the temperature output from the temperature sensor in the heater and outputting a first control variable output; a second temperature controller for receiving the temperature output from the first temperature sensor and outputting a second control variable output; and a low selector for receiving the first and second control variable outputs and selecting a lower first and/or second control variable outputs, and further controls the heating of the heater based on the selected lower the first and/or second control variable outputs. The space velocity of the fuel is 90,000/hr. The superficial velocity is 25 cm/sec. An INDEPENDENT CLAIM is included for a method of detecting sulfur-containing compounds in desulfurized fuel.