Plant operation shutdown

Thermal power plant components operated at high temperatures (>500°C) and pressures, such as superheater headers, steamline sections and Y-junctions, deserve great attention for both operation safety and plant availability concerns. In particular, during plant operation transients -startups, shutdowns or load transients - the above components may undergo high rates of temperature / pressure variations and, consequently, non-negligible time-dependent stresses which, in turn, may locally destabilize existing cracks and cause the release of acoustic emission. 

The results of over 1 year of continuous, on-line acoustic emission (AE) structural surveillance of high temperature / high pressure steam headers, gained on 2 M-scale 600MW supercritical multifuel ENEL power units in normal operation, are presented in the paper. The influence of background noise, the correlation between plant operating conditions (steady load, load variations, startup / shutdown transients) and AE activity and the diagnostic evaluation of recorded AE events are also discussed. 

Steam headers and steamline sections may undergo high rates of temperature / pressure variations during plant operation transients - startups, shutdowns or load transients - and are... 

Different plant operating conditions (steady load, load variations, startups / shutdowns) have been encountered during the monitoring period. Electrical load, steam pressure and steam temperature values vs time have been acquired and stored during the entire period. At the same time, the RMS values of the acoustical background noise were have been continuously checked and stored, thus providing a quick check of proper instrumentation condition and a correlation between variations of plant parameters and the acoustical behaviour of the components. 

Should plant be shutdown for any deviation beyond the operating limits ... 

Flashback protection is required for H2S flaring systems, either by water seal or continuous gas purge. If a water seal is used, special requirements apply to the disposal of the effluent seal water. In the case of an HjS flaring system handling a flow of HjS which in uninterrupted throughout the period that a plant is in operation, and which stops only when the producing plant is shutdown, then flashback protection is not required. However, steam or inert gas connections are required to permit purging the flare line startup and shutdown. 

Table 4.1-3 NFDRS Contents [. Plant Operating mode i.c., c shutdown),...

Trips should normally be designed so that they operate if the power supply is lost. If this will cause a dangerous upset in plant operation, then an alarm should sound when power is lost. Trips should be tested at startup if they have been worked on during a shutdown. Particularly important trips, such as those on furnaces and compressors and high-oxygen concentration trips, should always be tested after a major shutdown. 

The persoimel at an industrial plant who me trained in tlie operation of die facility arc critical to proper emergency response. They must be taught to recognize abnormalities in operations mid to report tliem immediately. Plant operators should be taught how to respond to various types of accidents. Internal emergency squads also can be trained to contain the emergency until outside help arrives, or, if possible, to tenninate tlie emergency. It is especially important to train plant persomiel in shutdown and evacuation procedures. 

While startup and shutdown occur relatively infrequently in large continuous plants, they are inherent in batch plant operation. Most startup and shutdown procedures, whether devised empirically or theoretically, are designed to follow a recipe of actions with no feedback. Thus, if upsets occur, there is often no way to change the startup or shutdown in time to avoid imwanted process exclusions. Procedures are needed that incorporate feedback and adaptive techniques to the problem of plant startup and shutdown. 

Industrial H2 production plants operate at steady state. They were not designed either for numerous start-ups and shutdowns or for the cycling in load. The catalyst and other reformer materials can be chemically and physically damaged. 

Modern data acquisition and evaluation help to optimise the plant under review within a short period of time, to eradicate faults in plant operation and to determine the best materials for the operation of the chlorine electrolysis plant being examined. In this way, inter-relationships are examined between the energy consumption and variables such as membrane types, anode and cathode coatings, temperature, pressure, and concentrations as well as plant shutdowns, brine impurities, materials of construction and manufacturers. It is conceivable that other inter-relationships will come to light that have so far not been considered. 

Commercial operation of sulfuric acid alkylation plants has been relatively trouble-free and shutdowns for reasons other than normal inspection and maintenance are seldom required. Many plants operate on a one-year regular shutdown and high on-stream efficiencies are obtained. In spite of the fact that a strong acid is used as catalyst, corro-... 

Carefully review startup and shutdown procedures and the consequence of a time delay in any step of the process. Evaluate the consequences of an extended hold or shut down period on plant operation. 

The plant manager will assess the effect of the proposals on all plant operations, including normal and routine operations, startup, shutdown and emergency actions. He must also check that hazardous conditions cannot arise due to mal-operation. 

The top temperature of a FFB regenerator should not be more than 730°C unless specified for special occasions. Superficial gas velocity is 1.2-1.8 m/s. Normal operation is quite flexible, and control is easy during plant startup, shutdown and upset. 

Unsteady-state or dynamic simulation accounts for process transients, from an initial state to a final state. Dynamic models for complex chemical processes typically consist of large systems of ordinary differential equations and algebraic equations. Therefore, dynamic process simulation is computationally intensive. Dynamic simulators typically contain three units (i) thermodynamic and physical properties packages, (ii) unit operation models, (hi) numerical solvers. Dynamic simulation is used for batch process design and development, control strategy development, control system check-out, the optimization of plant operations, process reliability/availability/safety studies, process improvement, process start-up and shutdown. There are countless dynamic process simulators available on the market. One of them has the commercial name Hysis [2.3]. 

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