Page 43 - Plant design and economics for chemical engineers

26 PLANT DESIGN AND ECONOMICS FOR CHEMICAL ENGINEERS

specifying plant operation for 300 calendar days per year. Assuming 90 percent
yield in the alkylator and a sodium dodecylbenzene sulfonate product to be 85
percent active with 15 percent sodium sulfate as inert, the overall material
balance is as follows:
Input components:
(15 x 106)(0.85)
Product (85% active) = (300)(348.5) = 122 lb mol/day

C6H6feed=(122)(&)(&)=142.71bmol/day

= (142.7X78.1) = 11,145 lb/day
C,,H,, feed = 142.7 lb mol/day
= (142.7X168.3) = 24,016 lb/day
20% oleum in = (1.25)(11,145 + 24,016) = 43,951 lb/day
Dilution H,O in = (0.244/1.25X43,951) = 8579 lb/day
20% NaOH in = (1.25)(43,951) = 55,085 lb/day
AlCl, catalyst in = (0.05)(11,145 + 24,016) = 1758 lb/day

Alkylation process:

Alkylate yield = (0.9X142.7X246.4) = 31,645 lb/day
Unreacted C,H, = (O.lXllJ45) = 1114 lb/day
Unreacted C,,H,, = (O.lX24,016) = 2402 lb/day

Sulfur balance:

Sulfur in = (43,951Xl.O45X32.1/98.1) = 15,029 lb/day
Sulfur out = sulfur in detergent + sulfur in spent acid
(50,000)(0.85)(32.1) (50,000)(0.15)(32.1)
Sulfur in detergent =
(348.5) + (142)
= 3915 + 1695 = 5610 lb/day
Sulfur out in acid = 15,029 - 5610 = 9419 lb/day

Weight of 78% H,SO, = (9419) (E)( &)= 36,861 lb/day

The weight of the heavy alkylaryl hydrocarbon is obtained by difference as 3516
lb/day.
The material balance summary made by the design group for the process
shown in Fig. 2-3 is given on a daily basis in Fig. 2-4. After a complete material 1 .
balance is made, the mass quantities are used to compute energy balances