Homework Set No. 1ChE 473KSpring 2018R.B. Eldridge

Problem No. 1 (Aspen based design and cost estimate )

A feed of 7500 std bbl / day of a four component mixture is to be separated into three streams usingtwo fractionation columns. The feed to both towers is at 120 °F. Cooling water is fed to the overhead condenser at 110 °F and 100 psia saturated steam is available to heat the reboiler. Feed and product data is given below:

Component / Feed (mole %) / Product A (mole %) / Product B (mole %) / Product C (mole %)
2-methylpentane / 35.6 / 93.8 / 3.4
cyclohexane / 33.1 / 6.2 / 86.4
toluene / 3.8 / 10.2 / 0.7
m-xylene / 27.5 / 99.3

Obtain:

1)The separation sequence for the two columns that produces the lowest energy consumption and capital cost.

2)The required reflux ratio for the towers (based on the optimum sequence) which contain75 actual stages plus a total condenser and reboiler.

3)The detailed equipment list (based on the optimum sequence) including bare equipment cost for each column system (column, reboiler, condenser, overhead accumulator, and reflux pump).

The columns containtwo pass sieve trays with a measured 80 percent tray efficiency. Obtain the column diameter at 80 percent of flood. The reflux and overhead product streams are subcooled to 120 F. The system is carbon steel. Use the RK-Soave model for the VLE prediction.

Problem No. 2(Capital cost)

Determine the installed cost in 2020 for a jacketed / agitated stainless steel reactor to be used for the neutralization of 200 tons per day of a 20 wt. percent H2SO4 solution (sp.gr. = 1.15) using a 40 wt. percent NaOH solution (sp.gr. = 1.50). Holding time in the tank should be one hour based on the total flow to the tank. Assume the tank level is held at 80 percent of the tank height. Procurement for the process is being done in the US Gulf Coast.

Reactor Bare Equipment Cost Equation (s = volume in m3)

Ce = a + b s n

a = 30,500b = 16,500n = 0.8

Cost basis: US Gulf Coast -January 2016, carbon steel vessel.

Problem No. 3 (Optimization)

In a plastic pipe manufacturing operation, 50,000 lb/hr of air (Cp = 0.24 BTU / lb F) must be cooled form 300 F to 50 F. This can be done in a single heat exchanger using refrigerant. However, in another part of the process, a large quantity of acetone (Cp = 0.50 BTU / lb F) is being heated from 55 F to 105 F using steam. You suggest to your boss a scheme to use the cold acetone in a pre-cooler to save some money. Your proposed process is shown below:

Data:

Heat transfer coefficient for each exchanger: U = 15 BTU / hr ft2 F (assume perfect countercurrent flow)

Heat exchanger bare equipment cost = $ 100,000 * (Area / 2000) 0.8 where area = ft2

Refrigeration unit bare equipment cost = $ 2000 * (Q refrigeration in BTU / hr / 12,000) 0.8

Determine the intermediate temperature Ti that will minimize the FCI of the air cooling process.