Duty specifications

Type of equipment Suitable for duty specification f Required slurry-separation characteristics ... 

The multiple separation duty specifications can be made in several ways. Two of which are ... 

Equality constraints h(D°, D°) = 0 may include, for example, a ratio between the amounts of two products, etc. Inequality constraints g(u, D°) < 0 for the overall operation include Equations 7.14-7.18 (the first two of which are easily eliminated when m and H are specified) and possibly bounds on total batch time for individual mixtures, energy utilisation, etc. Any variables of D° and D° which are fixed are simply dropped from the decision variable list. Here, Strategy II was adopted for the multiple duty specification, requiring B0 to be fixed a priori. Similar considerations hold for V, the vapour boilup rate. The batch time is inversely proportional to V for a specified amount of distillate. Also alternatively, for a given batch time, the amount of product is directly proportional to V. This can be further explained through Equations 7.24-7.26) ... 

The dependent variables are the pressure or temperature, the vapor fraction, and the vapor and liquid compositions. In a truly adiabatic process Q = 0 (or h2 + H2 = the term adiabatic flash is generally applied to a process where the heat duty is specified. The problem is to determine a temperature (or pressure if the temperature is specified) at which the total enthalpy of the products satisfies the heat duty specification. Once and are known, the problem is handled as an isothermal flash. Again, in this case, the solution could result in a single phase or a mixed phase, and any set of temperature (or pressure) and heat duty specification is feasible. 

The typical duty specification required for this service is of high deUvery head and very low flow capacities. Sulfur has a melting point of 119 °C and a peculiar characteristic of a sharp rise in viscosity at a temperature above 150 C. It becomes extremely difficult to pump liquid sulfur above this temperature. The practical range for operating a sulfur pump is 125-135 °C. 

In the author s experience, failure by process technologists to specify the full range of operation is the most frequent cause of the selection of inappropriate equipment, especially for turbo-compressors. The duty specifications should be proactively cross-examined. 

Equipment Suitable for Duty Specification Slurry Characteristics ... 

The principles involved in duty specification are shown in Figure 5.3. Each specification is identified by a characteristic letter, so that a group of letters define the nature of a problem. For example, a large scale batch operated system for the recovery of untreated solids would be coded as adg. 

Figure 5.3 Coding the duty specification (adapted from Purchas and Wakeman, 1986).

The duty specification, jar sedimentation and filtration tests enable the slurry settling and filtering characteristics to be broadly classified, and a selection problem to be specified through a series of letter codings. In order to select and rank equipment from this information it is necessary to provide charts and/or tables which relate equipment performance to the letter codings. Comparisons between the user defined specifications and the tables/charts enable the selection process. 

Section 5.1.1 detailed the charts and data tables which exist in the public domain. While they provide an insight into the application and operation of particular classes of equipment, they rarely address the problem of how a class of equipment is correctly chosen in the first instance. Generic classes of equipment have been described in Chapter 1 and previously identified by Davies (1965), Moos and Dugger (1979), Purchas (1981), Purchas and Wakeman (1986), Tarleton and Wakeman (1991) and Wakeman and Tarleton (1991a). In Table 5.1 these generic classes are reiterated and associated with the letter codings for duty specification, jar sedimentation and... 

Design a lesson plan for teaching ROTC cadets how to stay safe while performing parking lot duty. Specifically, you should consider how they will... 

Duty Specific controller functions. Continuous constant load, indefinitely long time period. Short time constant load, short or specified time period. Intermittent varying load, alternate intervals, specified time periods. Periodic intermittent duty with recurring load conditions. Varying varying loads, varying time intervals, wide variations. 

The last step in building the column model is adding the pumparounds for each product draw. We re-enter the Side-Ops tab and create the pumparounds for each product. The draw and return stages are the typically the same as side-stripper draw and return stages. Kaes [3] documents some alternative configurations, but the difference for simulation is often small when compared to errors in the other simulation assumptions. We note that we have two specifications for each pumparound a flow specification and a duty specification in Figure 2.42. 

Figure 2.42 Specifying flow and duty specifications for the pumparound.

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