Debutanizer reboiler duty

FIGURE 4.3. Correlations of debutanizer reboiler duty and other parameters. 

Example Part 2 Now, having the debutanizer tower answers, material balance, determine the condenser and reboiler duties using Table 1.10. Remember, you may opt to use mixture average molecular weight basis to interpolate enthalpy values in Table 1.10. 

N Newton Tomich 132) Holland (8) Narrow- or middle-boiling systems Nearly ideal, many trays a problem Debutanizers, demethanizers Two of condenser duty, reboiler duty, reflux, and boilup plus all side product flows, one purily allowed... 

Later, I met with unit operating personnel. They were more specific. They observed that the pumparound circulating pump (see Fig. 1.1a) was defective. Whenever they raised hot oil flow to the debutanizer reboiler, the gas plant would become destabilized. Reboiler heat-duty and reflux rates would become erratic. Most noticeably, the hot-oil circulating pump s discharge pressure would fluctuate wildly. They felt that a new pump requiring less net positive suction head was needed. 

When dealing with correlations involving multiple variables, economic sensitivity analysis is essential to determine the most influential parameters. For example, feed preheat and 4% in the bottom are very sensitive to reboiling duty more than other operating parameters for the debutanizer. Getting the most sensitive parameters right in operation can get the greatest economic and technical response. 

Figure 12-4 illustrates the operation of a debutanizer equipped with a kettle reboiler. The liquid level in the bottom of the lower is determined by the pressure difference between the reboiler and the tower. (As the reboiler vapors vent back to the tower, the reboiler must be at the higher pressure.) The plant operators observed that when they increased the reboiler heat duty beyond a certain point, the lower s AP gauge reading would dramatically increase, indicating flooding. They therefore erroneously concluded that the trays were overloaded. 

---