Temperature once-through balanced

Figure 9.19 Batch crystallizer with once-through balanced temperature control.

The pyrolysis experiments were conducted in an electrically heated, once-through tubular flow reactor, designed to simulate the time-temperature history experienced in commercial steam-cracking operations. Reactor effluent compositions were ascertained by gas chromatograph and mass spectrometer analyses. Material and hydrogen balances could always be effected, with typical closures of 98 2 wt %. 

The tubes in the steam generators are of a once-through type. The primary Pb-Bi flows on the shell side, while the secondary (water) coolant flows on the tube side. Table XXIV-12 lists the inlet and outlet temperatures calculated using the energy balance equation and the thermal efficiency for the steam generator spanning from 5 MPa to 15 MPa. 

Energy balance calculations for a system (a process unit or combination of units) are conveniently organized through the construction of an inlet-outlet internal energy table (or enthalpy table). The table lists n (or h) and U (or ft) for each species at each state (phase, temperature, pressure) in which the species is found in process streams. Once all of these variable values have been determined and inserted in the table, the subsequent evaluation of AC,. AH. or AH is straightforward. 

Konig created a heat balance by assuming that the heat flux into the refractory surface must equal the heat flux through the furnace shell. If the heat flux into the refractory surface exceeds the heat flux out of the shell, the interface temperature (Tr) must increase, causing increased corrosion rates until the heat balance is maintained once again. Terms used in Konig s analysis are given in Table 1. 

Once the composition of synthesis gas and carbon conversion are known, the moles of each compound produced per mole of vacuum residue (Wi-ng) are calculated so that the enthalpy balance equation for adiabatic operation can be solved (Equation 4.60), in which the temperature is the only unknown. By this way, the new temperature of the system is calculated. The outlined procedure is repeated until the temperature value converges. Einally, by knowing the final composition of the synthesis gas, it is possible to calculate its calorific value and energy efficiency of gasification with Equations 4.66 through 4.68. Figure 4.3 shows schematically this iterative method. 

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