Plant shut-down

Rarely in the pharmaceutical industry is a new plant built to accommodate a new process or product It may happen in the petrochemical industry, where economies of scale mean that product-specific plants are designed from scratch and then continuously de-bottlenecked over a number of years to increase and optimize productivity, but it is not the case in the pharmaceutical industry, where the number of types of unit operations in use is generally fairly small and fixed. Within a multi-purpose chemical plant commonly found in the batch chemical industry, it is common practice for process designers to make do with what is available on a given site to avoid capital expenditure and plant shut-down for modifications. 

Many plants shut down for 1 days per week. Failure to factor this in the chemical consumption calculations may render any proposal offered to appear to be uneconomic. 

The total capital cost consists of the depreciable capital cost, land cost, land or site development cost, startup cost, and working capital. In theory, land cost is completely recoverable when a plant shuts down, and Uherefore is not depreciable. Land cost varies from 0.01 to 0.02 times the depreciable capital cost. Use an average value of 0.015. 

This thermal behaviour of the biomass ash results in a number of technical problems, such as lowering of the heat transfer coefficient value, restricting the gas flow through the reactor due to increased deposits, and an eventual decline of the conversion efficiency. Large-scale fouling, deposition and/or agglomeration can lead to unscheduled plant shut-downs and subsequent deterioration of the plant economics. 

A cyclone on a cement plant suddenly malfunctions. By the time the plant shuts down, some dust has accumulated on parked cars and other buildings in the plant complex. The nearest affected area is 700 ft from the cyclone location, and the furthest affected area measurable on plant grounds is 2500 ft from the cyclone. What is the particle size range of the dust that has landed on plant grounds ... 

The practical application of this reaction, conducted by Shell Chemical on an industrial scale in its Norco. Louisiana, plant, shut down in 1980, is much more complex. Indeed, the initial objective was to symhdfe.gjycerin from propylene, with the production of acetone (or methyl ethyl ketone)asasubsitiiary product. The general scheme of this operation is as follows ... 

Developed in Germany during the Second World War, this process was used in Japan by Mitsubishi in a 25,000 t/year plant, shut down in 1976. It is based on the disproportionation reaction of benzoic add to terephthalic add and benzene. Starting with toluene, it involves the following reactions ... 

The production of phosphorus trichloride from phosphorus and chlorine is an important step in the manufacture of a number of agrochemical products. Raman spectroscopy has been used to monitor the reaction and control the raw material feed rates. This maximises production of phosphoras trichloride, minimizes the formation of phosphorus pentachloride and ensures safe operation when plant shut-down periods are needed. Remote analysis is achieved using optical fibers to provide a safer operation and a more rapid analysis than was previously possible [29, 30]. 

An on-site Plant shut-down project, responsible for co-ordination, planning of the works and logistics for contractors. It was itself divided into several projects ... 

Result. Eventually cause located, plant shut down and repaired but later dismantled. 

When carrying out a rigorous profitability analysis, some design teams adopt the convention of reducing the process yield by a small amount, such as 2%, to account for the loss of raw materials and products during startups, shutdowns, and periods when there are malfunctions. Often, raw materials are vented or flared during startup. In other cases, one part of the plant shuts down while the remainder continues to operate, with small amounts of intermediate products vented when they are nontoxic and not easily stored, until the idle portion of the plant is restarted. 

If a plant leaves its range of specified operation because one or several process variables have left their nominal range the PCE equipment intervenes at the limit between specified operation and tolerable fault conditions, unless there is a reason for plant shut-down. 

Primary explosion protections means also that in case of an unintentimial escape of gas this event is detected in due time and the gas is removed as quickly and as safely as possible, for example through self-opening windows or fans, before the mixture concentration exceeds the lower explosion limit. The necessary air intake must be calculated on the basis of the amount of gas which can escape during incidents or accidents like leaks or pipe ruptures. Diffuse leaks should also be taken into account. For such leaks and also for gas trapped during plant shut down ventilation should be provided which is appropriate to handle the gas volumes which could escape. 

Better scrubber designs, especially to take care of heavy pollution loads at startup of the plant or after a long plant shut down. 

AR436 1.167 Restart of a nuclear power plant shut down by a seismic event (ML003740093) (Draft... 

The main features of the control system of the plant are reported here. A dedicated programmable logic controller (PLC) handles both regulation loops and an alarms-interlocks system. If any process condition exceeds the design values, a trip system is activated and an interlock sequence restores a safe state. The control panel operator monitors alarm indicators and may take appropriate action when needed to avoid a plant shut-down. 

Cost analyses also need to be extended from a reactor engineering level to process engineering issues. This includes provision of modularity, easier scalability (quantifying time-to-market), reduced plant footprint, easier legislation/fast authority approval and high shares of operation compared with plant shut-down. Full process simulations, such as done currently with ASPEN for conventional processes, are needed as a base for economical investigations. 

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. 

The major problem under this heading is whether the necessary actions have been learned and are available when needed. The latter point is particularly crucial in emergencies, such as evacuation, plant shut-down and first aid treatment. Considerable investment in refresher training, sometimes on simulators, is needed to keep rarely used skills available enough to be deployed accurately when they are wanted. 

At plant shut-downs the catalyst should be purged with dry process air for half an hour to remove the SO3 absorbed by the catalyst itself. After the cleaning with air, care must be taken that moist air does not enter the converter tower. Therefore all valves must be closed to prevent ambient air coming into contact with the catalyst. The catalyst is hygroscopic especially when it has been used for the SO2 SO3 conversion. Catalyst handling and sieving instruction are found in Appendix 3. 

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