Startup heating system

The AFWS is a 2 division and 4 train system. The AFWS is designed to supply feedwater to the SGs for RCS heat removal in case of loss of main/startup feedwater systems. The reliability of the AFWS has been increased by use of two 100% motor-driven pumps, two 100% turbine-driven pumps and two independent safety-related auxiliary feedwater storage tanks as a water source instead of condensate storage tank. 

At this point in time, the temperature of the reformer feed amounted to about 110 ° C and the reformate left the reactor at a temperature of220 °C. The full reformate flow was achieved after 30 s and the temperature of the reformate was then 500 °C. After 60 s the steam left the evaporator at a temperature of400 °C and the reformate outlet temperature was already 700 °C. The total mass of a future 50 kW fuel processor was estimated to be 55 kg, which corresponded to a total energy demand of 7 MJ for startup heating. From this value, the power demand of an air blower, which had to provide some 22 m min air to the system during start-up, was calculated to about 1 kW. As this power would have been required only during the rapid system start-up (60 s) a normal battery would have been sufficient as the power supply. An efficiency of 78% was calculated for the entire future fuel processor. 

The FWS, which provides feedwater via the startup feedwater system for heat removal from the reactor coolant system, in the event of a feedwater system failure. See subsection 6.6.5 for a description of the operation of the FWS. The startup feedwater is also automatically actuated on signals which indicate a loss of water inventory or heat sink in the secondary side of the steam generator (see subsection 7.7.1.8.2 of Reference 6.1). 

Startup heating switch gear, gas heating and cooling systems for the reactor and dump tanks, inert gas storage systems, control rooms, and other auxiliaries are located relative to the above systems as logically as possible in the light of their functional requirements. 

The high temperatures involved preclude the use of larger SOFC systems for transient applications. Also, the electrolyte is not conductive until an elevated temperature is reached, so that some kind of prebumer heating system is needed for startup. 

The redesigned system is schematically described in Fig. 5.69. The startup bypass system in the original design is replaced by the separate recirculation system that consists of a steam drum, a heat exchanger, a circulation pump, and pipes. Neither the inlet nor outlet of the recirculation system are connected to the main lines, rather they are directly connected to the reactor vessel in order to form a closed space for pressurization like the recirculation system of BWRs. 

A typical lubrication oil system is shown in Figure 15-1. Oil is stored in a reservoir to feed the pumps and is then cooled, filtered, distributed to the end users, and returned to the reservoir. The reservoir can be heated for startup purposes and is provided with local temperature indication, a high-tempera-ture alarm and high/low level alarm in the control room, a sight glass, and a controlled dry nitrogen purge blanket to minimize moisture intake. 

One of the major funetions of the eombined eontrol-proteetion system is to perform the startup sequenee. This sequenee ensures that all subsystems of the gas turbine perform satisfaetorily, and the turbine does not heat too rapidly or overheat during startup. The exaet sequenee will vary for eaeh manufaeturer s engine, and the owner s and operator s manual should be eonsulted for details. 

J. E. Troyan s series of articles on plant startup has a cause/effect table on instrumentation in Part II. This article also has troubleshooting hints for distillation, vacuum systems, heat transfer, and filtration. Here is the table on instrumentation. 

A flow direction switch occurs at r/2 for a cycle period r set by the plant operator, or it may be initiated by the reactor or recuperator outlet temperature. Startup of the flow-reversal system requires a heating device to bring the catalyst bed or at least the frontal portion up to ignition temperature. This temperature is about 350°C for S02 oxidation using conventional catalysts. 

SJi. The initial startup of an adiabatic, gas-phase packed tubular reactor makes a good example of how a distributed system can be lumped into a series of CSTRs in order to study the dynamic response. The reactor is a cylindrical vessel (3 feet ID by 20 feet long) packed with a metal packing. The packing occupies 5 percent of the total volume, provides 50 ft of area per of total volume, weighs 400 ib yft and has a heat capacity of 0.1 Btu/lb °F. The heat transfer coefficient between the packing and the gas is 10 Btu/h It "F. 

Thermocouples and wire leads require constant maintenance due to wire breaks and malfunctioning thermocouples. In most cases, the root cause of the problem is easy to determine. When a thermocouple loses continuity the instrument panel typically reports either an open circuit or a very negative temperature. A more difficult but also common problem occurs when the control thermocouple is not located close to the heating element on the control system. In this case, it is possible for the thermocouple to be influenced by another heated control zone while allowing its control zone to operate at temperatures that can be either very hot or very cold. Such cold conditions can cause the polymer to solidify in the transfer line while a hot condition can cause the resin to degrade. During the installation and startup of new equipment, it is important that the thermocouples are matched with the proper controller and control zone. 

The heat transfer piping system is not simple. There were three reactors and the heat transfer system is used for both heating and cooling the reactor. The circulating fluid heats the reactor to several hundred degrees Fahrenheit to startup the reaction. Once the very exothermic reaction is under way, the circulating heat fluid removes heat from this reactor. (See Figure 8—1.)... 

The entire 8-inch (20 cm) piping system was insulated and steam traced except for the heater tubes within the heater. Operations assumed the heat transfer fluid froze in the four heater tube passes. Each pass was a bare 4-inch (10 cm) diameter heater tube with 5 bends and the equivalent of 72 ft. (22 m) of straight pipe. The foreman and the operations team discussed the situation and decided to light and maintain a small fire on the burner to slowly thaw the material in the heater tubes. This method had been successful for a startup several weeks earlier. 

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