Plant start up, shut down

Although continuous stirred-tank reactors (Fig. 3.12) normally operate at steady-state conditions, a derivation of the full dynamic equation for the system, is necessary to cover the instances of plant start up, shut down and the application of reactor control. 

In certain situations the plant operator may wish to override the automatic mode and adjust the controller output manually. In this case there is no feedback loop. This manual mode of operation is very useful during a plant start-up, shut-down, or emergency situation. Testing of a process to obtain a mathematical model is also sometimes carried out in the manual mode. Commercial controllers have a manual/automatic switch for transferring from the automatic mode to the manual mode or vice versa. Bumpless transfers that do not upset the process can be achieved with commercial controllers. 

PLANT START-UP/SHUT-DOWN AND OPERATIONAL CONDITIONS SULPHONATION/NEUTRALISATION... 

Plant start-up/shut-down and operational conditions sulphonation/neutrali- ... 

Emissions occurring during plant start ups, shut downs and emergency stops are sent to a containment system to avoid their emission to the environment. The contained material, which can be unreacted monomers, solvents, polymers, etc. are recycled if possible or used as fuel, e.g. in the case of polymers of undefined quality. 

Other than an important and far-reaching guide word, but consequently more vague in its application. It covers all conceivable situations other than that intended such as, start-up, shut-down, maintenance, catalyst regeneration and charging, failure of plant services. 

Intermediate products Equipment Instrumentation Plant layout Start-up Shut down... 

Signals to the Plant Protection and Instrumentation System (PPIS) and the NSSS Control Subsystem (NCS) are supplied by neutron detectors. During power operation, the neutron flux levels are monitored by detectors located in wells between the reactor vessel and the concrete cavity wall. These detectors are distributed symmetrically around the reactor vessel at about the core midplane. During low power operation, starting up, shutting down, and while shut down, the neutron flux levels are monitored by source-range detectors, located in selected side reflector elements near the bottom of the active core. 

What are the effects of changes of state of the media in case of deviations from nominal operating conditions (e.g. state of aggregation, viscosity, interfacial tension) Are the plant and its parts designed properly as to process conditions, structural strength and materials for the cases normal operation, start-up, shut-down and emergency shut-down ... 

The basic principle for a computer-aided start-up (shut-down) is to present the operator with a checklist of procedures that he or she must undertake either just prior to or during the 2 hour pre-heat cycle of the gas-raising plant. Where possible the computer will cross-check the operator actions by ... 

Where it is necessary to follow a fixed sequence of operations—for example, during a plant start-up and shut-down, or in batch operations — interlocks are included to prevent operators departing from the required sequence. They may be incorporated in the control system design, as pneumatic or electric relays, or may be mechanical interlocks. Various proprietary special lock and key systems are available. 

Gaming process know-how (dynamic behavior of the plant, start-up and shut-down procedures)... 

The risk-informed P-T limits were developed using PFM analyses to determine the coefficients a and p that would ensure that the CPF did not exceed 2E-7 during normal plant start-up and shut-down. The PFM analysis results indicated that a=l and j8= 61 °C (110°F) would ensure compliance with CPF = 2E-7 during normal plant start-up and shut-down (EPRI, 2009). 

Prior to discussing the flare reduction case study, it is important to introduce the plant shut-down and start up procedures as these accounts for a significant extent to the overall flaring in the ethylene plant. The Normal shut down procedure involved initially the reduction of all equipment operating levels. 

A major potential source of discontinuous emissions in the polymer production processes is the reactor system. Discontinuous emissions from reactor systems occur during plant start ups (for instance purging), shut downs and emergency stops. 

Thus six atoms of iron will produce nine molecules of water compared with six atoms of zinc, which only produce six. Furthermore iron sulfide can release hydrogen sulfide by reaction with hydrogen and steam during plant start-up or shut-down conditions. In practice, therefore, when iron oxide is used it is always followed by a guard bed of zinc oxide. 

The KDF filter was first tested in prototype on a coal mine in northern Germany. It was installed in parallel with existing vacuum filters and it produced filter cakes consistendy lower in moisture content by 5 to 7% than the vacuum filters. Two production models have been installed and operated on a coal mine in Belgium. The filter is controlled by a specially developed computer system this consists of two computers, one monitoring the function of the filter and all of the detection devices installed, and the other controlling the filtration process. The system allows optimization of the performance, automatic start-up or shut-down, and can be integrated into the control system of the whole coal washing plant. 

Data for the production and sales of maleic anhydride and fumaric acid ia the United States between 1979 and 1992 are shown ia Table 5. Production of maleic anhydride during this time grew - 2% on average per year. Production of fumaric acid has declined during the same period as customers have switched to the less cosdy maleic anhydride when possible. All production of maleic anhydride in the United States in 1992 was from butane-based plants which used fixed-bed reactor technology as shown in Table 6. The number of fumaric acid producers has been reduced considerably since the early 1980s with only two producers left in the United States in 1992 as shown in Table 6. Pfizer shut down its fumaric acid plant at the end of 1993. However, Bartek of Canada will start up an expanded fumaric acid faciUty to supply the North American market for both their own and Huntsman s requirements. 

Eight years went by before another bad leak occurred. When it did occur, the area around the pumps w as filled with a visible cloud of propylene vapor 1 m deep. Instead of using the emergency equipment, which would have stopped the flow of propylene and shut down the plant, two very experienced foremen went into the compound, shut down the leaking pump, and started the spare up in its place. Fortunately the leak did not fire. 

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