Startup time

WU lowest cost SO2 produced in situ catalyst requires startup time higher most every sulfonation and sulfation ... 

Besides being slower, anaerobic treatment is more difficult to manage and can generate by-products that are more mobile or toxic than the original compound, for example, the daughter products of TCE, ie, dichloroethenes and vinyl chloride. It requires a longer acclimation period which means slower startup times in the field. The microbial processes are less well understood, and hence, ate less controlled than for aerobic systems. 

Startup time may be defined as the time span between the end of construction and the beginning of normal operation. Hence it should start when the contractor finishes the whole plant or a specified section of it to enable comparisons to be made with other startup times. It is usual to define normal operation as (1) operations at a certain percentage of design capacity, (2) a specified number of days of continuous operation, or (3) the capabihiy of making products of a specified purity. 

Startup time tsu fof these plants may be estimated from construction time tc by developing an equation similar to Eq. (9-260) ... 

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. 

Solution The surface is estimated to contain 0.067mol of A in adsorbed form. The inlet gas contains 1.6 mol of A per cubic meter and is flowing at 150cm /s so that A is entering the reactor at a rate of 0.00024 mol/s. Five minutes are needed to supply the surface if all the incoming gas were adsorbed. Fifteen to thirty minutes would be a reasonable startup time. Recall that the reactor has a gas-phase residence time VjQout of only 1.5 s The residence time of the adsorbed species is 700 times larger than the average (nonadsorbed) molecule. 

The construction costs were incurred before the plant began operating and are spread unevenly over a number of years. Assume that on the average they date from a year before the plant startup. Time zero is assumed to be the beginning of the initial plant startup. 

Startup time, from cold start at -25°F (—32°C), with 28 V power and vehicle interior temp, rises to above 32°F (0°C) in 10 min. 

Operate the chemostat initially as a batch reactor with D = 0, and then switch to chemostat operation with D [Pg.541]

Cost reductions usually arise out of improvements to the control of the process for both continuous processes and batch processes. Process analyzers enable chemical composition to be monitored in essentially real time. This in turn allows control of the process to be improved by shortening startup times and transition times (for continuous processes) or batch cycle times (for batch processes), by improving the ability to respond to process disturbances, by enabling process oscillations to be detected and corrected, and by reducing product variability. Real-time monitoring of chemical composition in a process allows a manufacturing plant to ... 

Ohmic heating of catalyst is often used as a simple method of igniting the chemical reaction during reactor startup, for instance, in the oxidation of ammonia on platinum-rhodium gauze catalysts. Another application is the prevention of cold-start emissions from automotive catalysts responsible for much of the residual pollution still produced from this source (21). The startup times needed for the catalyst to attain its operating temperature can be cut by a factor of 5 or more by installing an electrically heated catalyst element with a metallic support upstream of the main catalyst unit. Direct electrical catalyst heating permits facile temperature control but requires a well-defined catalyst structure to function effectively. 

In order to compare investments having different lives or with variations in return during their operating fives, it is necessary to convert rates of return to a common time basis for comparison. Although any time may be used for the comparison, the plant startup time is usually the most satisfactory. Expenditures prior to startup, and income and expenditures after startup, are converted to their worth at startup. The discussion that follows is based on the predicted startup time as the basis of calculation. 

Expenditures prior to startup. The expenditures prior to startup can be placed in two categories (1) those that occur uniformly over the period of time before startup and (2) lump-sum payments that occur at some point before the startup time. 

Construction costs are generally assumed to be disbursed uniformly between the start of construction and the startup time, although equivalent results can be obtained if they are considered to be a lump-sum disbursement taking place hallway between the start of construction and startup. The present worth of construction costs that are assumed to occur uniformly over a period of years T prior to startup can be calculated using either continuous interest compounding or discrete (annual) interest compounding. 

T = years before startup time that payment was made i = annual interest rate... 

Expenditures at startup. Any costs that arise at startup time do not have to be factored, but have a present worth equal to their cost. The major investment at this time is the working capital, but there also may be some costs involved with the startup of the plant that would be invested at this time. 

There are certain costs that are assumed not to depreciate and that are recoverable at the end of the normal service life of the project. Among these are the cost of land, working capital, and salvage value of equipment. These recoverable values must be corrected to their present worth at the startup time. 

It is necessary to use a trial-and-error solution to calculate the discounted cashflow rate of return, because the interest rate must be determined that will make the present value at the startup time of all earnings equal to that of all investments. An example of a typical balance for continuous-income and continuous-interest with uniform annual net income follows. 

Land value. The in-an-instant value of the land is 200,000 one year before the zero reference point of plant startup time. The land value at zero time, therefore, is the future worth of this 200,000 after one year with continuous interest compounding. Thus, by Eq. (36) of Chap. 7 or part (e) of Table 3 in Chap. 7. 

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