Extended startup times

Under these conditions, copper and iron pickup (crud) may reach devastatingly high levels, cleaning requirements are frequent, and startup times are extended. Also, maintenance and repair costs are high. 

The dynamic model proposed proved to represent well the separation in a DWC of a ternary hydrocarbon mixture. The values of internal flows and temperature distributions along the trays reached at steady state were in good agreement with the simulations obtained in the frame of commercial simulators. The use as control variables the reflux ratio or the side-stream flowrate proved to enable a reduction of the startup time with about 70 % compared with classical startup procedures. The complex technique developed can be a useful tool in studying dynamic behavior and startup optimization for complex columns and can be easily extended to various mixtures. 

An additional capacity control method is the unloader. This method can be used in conjunction with clearance pockets to extend the range of control to zero capacity. On double-acting cylinders, unloading the individual sides one at a time will provide a two-step unloading of the cylinder. On multicylinder arrangements, the cylinders can be unloaded one at a time providing as many steps as cylinders operating in parallel. The unloaders can also be used to totally unload the compressor, as is necessary for electric motor driver startup. 

As pointed out by Liebman et al., given a perfect model, an ideal data reconciliation scheme would use all information (process measurements) from the startup of the process until the current time. Unfortunately, such a scheme would necessarily result in an optimization problem of ever-increasing dimension. For practical implementation we can use a moving time window to reduce the optimization problem to manageable dimensions. A window approach was presented by Jang et al. (1986) and extended later by Liebman et al. (1992). 

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. 

As formation of the innate acids requires acid catalysis, there is a problem in starting the reactor operation as initially the raw material does not contain any acid. Thus, unless the process is triggered by an initial addition of a foreign acid , the startup is very slow as it relies on the small effect of water to catalyze the formation of tiny quantities of carboxylic acids, which in turn improve the catalysis, thus making more earboxylic acids, and so forth, until steady state is reached. Such a startup can take days, and it must be realized that any major interruption of the process, due to lacking raw material or other causes, also requires such a startup as it is not admissible to leave the charge in the reactor for any extended period of time since this is known to result in a... 

Most necipFocating pump are capable of dry seif-priming which means that suction line doesn t have to be filled up with liquid during pump startup. However, except diaphragm pump, they will be damaged, if they are ninning diy extended time. 

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