Page 89 - Chemical process engineering design and economics

74 Chapter 2

Propylene Heater

Table 2.9 contains the cost of process furnaces, also called process heaters. The
cost of a furnace with a heating rate of 20,000 kJ/s is $ 750,000 in mid 1982. Con-
verting the healing rate, 5.5xl0 6 Btu/h, given in Table 2.4.1, to kJ/s we obtain
3
1.612xl0 kJ/s. This heating rate is below the lower limit of the correlation range
given in Table 2.9. Because we have no other data, use the data in Table 2.9 to
estimate the heater cost. From Equation 2.15.1 in Table 2.15, we find that the base
cost,

( 1,612 V' 85
Cp B2i = 750,000 | ———— | =$88,200
I 20,000 )

Next, correct for inflation. Adjust the base cost from January 1990 to mid-1998
using Equation 2.15.2. The cost indexes for equipment are listed in Table 2.12,

436.0
Cp B i = 88,200 ——— = $ 114,400
336.2

To obtain the cost at design conditions, correct the base cost for temperature,
pressure, material of construction, and equipment design. In Table 2.4.1, the oper-
ating temperature is specified as 2,000 °F. From Table 2.10, the temperature is
between 600 and 5000 °C. Taking the high value, the temperature correction factor
is 1.2. The pressure is at base conditions, and therefore the pressure correction
factor is 1.0. Because the furnace is constructed of carbon steel the material
correction factor is also 1.0. In this case, the design factor is assume to be 1.0.
Thus, from Equation 2.15.3, the furnace cost at design conditions is

C PAi = 1.2 (1.0) (1.0) (1.0) (1.144x100 =$ 1.373xl0 3

From Table 2.8, the direct-cost factor for a furnace is 1.3, and from Equation
2.15.4 in Table 2.15, the indirect-cost factor is 1.34 for a fluid process, and the
factor for contingency and the contractor's fee is 1.18. Then, from Equation
2.15.4, the installation factor for the furnace,

f n= 1.3(1.34)(1.18) = 2.056

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