Total plant shutdown

Total Plant Shutdown A total plant BSD effectively shuts down the total plant or facihty under emergency conditions. Isolation valves are closed to stop the flow of combustible, flammable, or potentially toxic fluids and to stop heat input to process heaters or reboilers, and rotating equipment. Activation of a total plant BSD should not stop or impede the operation of fire protection or suppression systems, deluge systems, sump pumps, or critical utilities such as instrument or process air. 

Although it would be easy to institute a total plant shutdown for every incident, it would not be cost effective, as many small incidents occur relative to large incidents, which do not warrant the shutdown of the entire facility and would reduce the economic return on the investment. 

Rating 4 = Catastrophic (Destraction of equipment - total plant shutdown)... 

Continuous catalyst addition and withdrawal Is probably the most practicaf means to maintain constant production in a slurry methanol reactor. It gives the plant operator the flexibility to trade off catalyst replacement cost against methanol production rate, and It avoids the total reactor shutdown that is required to change Out a deactivated fixed-bed catalyst. 

Totally 104 failures have occurred over a total operation period. The abnormal operation events due to equipment and system failures resulted in 28 plant shutdowns of which 18 shutdowns involved reactor scrams (5 events involved manual reactor emergency shutdowns). In the remainder the plant power reductions took place. 

The unexpected vibration problems and severe bearing damages were a large part of the cause of the unplanned plant shutdowns. However, the countermeasures taken were so effective that the problem of the rotor oscillations is considered solved. After having carried out the above modifications new measurements were taken for the total turboset and especially for the HP-set. 

Total amount of sulfur issued in the last year (name of sulfur supplier, quantity obtained, average analysis) or in the period since the last plant shutdown/since the last time the pit was cleaned. 

Most of the modifications were implemented during the 2005 turnaround. Tie-ins were also put in place to install the remaining modifications early in 2006 without a plant shutdown. The plant is now fuUy operating at the target production rate of 470 Mt/year. The economic success has also been very satisfying. The total annual profits were estimated by the plant engineers from production increase and energy reduction at 16.1 million with a 15.7-month payback. 

Another problem of the MSR process is the formation of coke, which negatively affects catalyst performance (Rostrup-Nielsen, Sehested, Norskov, 2002). Indeed, it can lead to breakdown of the catalyst and the build-up of carbon deposits. Moreover, degraded catalyst may cause partial or total blockage of reformer tubes, resulting in the development of hot spots or hot tube and, in some cases, it can lead to plant shutdown (Rostmp-Nielsen, 1993). However, this problem can be reduced or controlled... 

In order to estimate the flared quantity for the normal case, two main assumptions are made 1) in Normal Startup, it is assumed that the plant is operated with minimum load of two furnaces in cracking mode. The minimum load of the fiimace is 26.5 T/h, which is 80 T/h for the three fiimaces. Thus, the flared quantity in 7-8 days is around 15,360 T of gas. 2) In normal shutdown, the fiimace throughput is reduced to 30% of total plant load, which is equivalent to 96 T/h. Thus, the flared quantity in 7-8 days is around 18,432 T of gas. 

Failure related maintenance demands Whenever a repair is made on a piece of equipment, a complete functional check-out is usually performed on it and the other equipment in the functional loop. Consequently, the number of shutdown and startup demands to repair degraded and incipient failures must be added to the number of catastrophic demand failures to determine total maintenance-related demands. These numbers are gathered from the encoded failure data that are in turn extracted from the raw plant records. 

Production of hypochlorite takes place in a two-step absorption unit in which 23% caustic solution is fed counter-currently to the chlorine feed-stream. In the first step -the liquid jet-loop reactor - about 90% of the chlorine is converted to hypochlorite. In step two - a packed column - a very efficient absorption [1-3] is carried out in which the chlorine concentration in the off-gas is reduced to <1 ppm. The operating window of this apparatus with respect to chlorine load is quite large and varies from 100 to 6000 kg h-1 of chlorine. This high capacity is necessary for the consumption of peak loads from the electrolysis plant during short time periods. During start-up or shutdown of one electrolyser the total chlorine peak load can vary from 100 to 300 kg in just a few minutes. 

The total investment expenditures incurred at a site have to be calculated in two steps. Equation (3.10) calculates the investments per plant. These are aggregated to the site level and adjusted for government investment incentives, defined as percentage of total investments, in equation (3.11). Investment expenditures are allocated to the time period preceding the commissioning of the technical capacity. A non-negativity constraint (3.54) ensures that plant/production line shutdowns do not lead to negative investment expenditures. 

Ash fouling, the accumulation of deposits on boiler tube surfaces in utility boilers, is a severe operating problem in many power plants fired with low-rank coals. Ash fouling is a complex phenomenon the extent of which is related to the boiler design, the method of operating the boiler, and the coal properties. In extreme cases it is necessary to schedule frequent shutdowns for removing the deposits or to derate the boiler. A recent survey of six power plants estimated that total costs of curtailments due to ash-related problems were 20.6 million over a six-month period (20). 

Standardized protection actions include shutdown of the reactor, of the main cooling system (which is not required for keeping the reactor within safe limits) and of the reformer plant. The two (required) shutdown systems consist of in total 18 absorber rods which are moved in the side reflector. Diversity is given by the employment of different propulsion systems. In particular, the active cooling of the core by the main cooling system is not required because fuel temperatures remain within the safety limits. Only for reactor vessel protection purposes, the surface cooling system in the reactor is necessary which alone is able to account for heat removal. 

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