CHE 441 ______

LAST NAME, FIRST

Problem set #4

(1)1 You are asked to design a flash drum without a mesh pad for a mixed feed with a low vapor flow rate. The design surge time is 2 minutes. The design liquid flow rate is 500 gpm. What are your recommended dimensions of the tank? Design a vertical and a horizontal tank and choose one. State the reason for your choice. Sketch the tank and put in all critical dimensions including feed location, LLL, NLL and HLL. State all assumptions in your calculations.

(2)1 Design a vertical knock-out drum without mesh pads which will remove 200 microns liquid droplets. The vapor flow rate is 2000 ft3/min. The liquid flow rate is 500 gpm and surge time (LLL-NLL) is 2 minutes. Density of liquid = 60 lbs/ft3. Density of vapor = 0.1 lbs/ft3. Viscosity of vapor = .05 c.p.

(3)1 Your boss asked you to design an accumulator for a partial condenser with vapor product and reflux. The reflux ratio is about 1.0. The design surge time between LLL and NLL for the accumulator is 5 minutes. The design liquid flow rate is 1000 gpm. You found in storage two vessels with the following dimensions:

Vessel # /

Orientation

/ Diameter, ft / Tangent-to Tangent Length, ft
1 / Horizontal / 9 / 25
2 / Vertical / 12 / 30

You are eager to tell your boss that he may not have to purchase a new vessel. But you must make a logical recommendation. You also notice that the plot space where the vessel is to be placed is rather tight. Support your recommendation with appropriate calculations, drawings and arguments.

(4)1 Design a steam system for an ammonia manufacturing process. The system generates three level of steam at 1500 psia, 600 psia, and 50 psia for heating and power generation. The 1500 psia steam is superheated to 1000oF. A compressor system totaling 40,000 hp is driven by steam turbines with adiabatic efficiencies of 60% operating between 1500 and 600 psia steam. Two pumps totaling 1,400 hp are driven by steam turbines with adiabatic efficiency of 60% operating between 600 psia and 50 psia. Two exchangers requiring 600 psia steam for heating are rated at 1.0´107 Btu/hr each. One exchanger (E-4) requiring 50 psia steam for heating is rated at 2.0´107 Btu/hr. Excess 600 psia steam can be sold to neighboring plant. All the condensate from heat exchangers and turbine condenser is pumped to a boiler maintained at 1500 psia from which steam is generated. All condensate is saturated at 50 psia. Make-up water is available at 50 psia saturated.

A process flow diagram (PFD) for the team system is show in Figure 1. Put flow rates, temperatures, and pressures on all streams. Calculate flow rates, duties, and horsepower on all equipment listed in the table below the PFD. Include all calculations using Mollier chart or CATT2 (Computer-Aided Thermodynamic Table 2).

Figure 1 Three level steam system.

E-1 duty (Btu/hr)
E-5 duty (Btu/hr)
P-1 horsepower
Flow rate through T-2 (lb/hr)
Flow rate through E-1 (lb/hr)
Flow rate through E-2 (lb/hr)
Flow rate through E-3 (lb/hr)
Flow rate through E-4 (lb/hr)
Flow rate of excess 600 psia steam (lb/hr)


(5)[1] You are asked to design a flash drum without a mesh pad for a mixed feed with a high vapor flow rate. The design surge time is 10 minutes. The design liquid flow rate is 200 gpm. What are your recommended dimensions of the tank? State whether the tank is horizontal or vertical. Sketch the tank and put in all critical dimensions including feed location, LLL, NLL, and HLL. State all assumptions in your calculations.

(6)1 Calculate the horsepower for compressing 5,000 lbs/hr of ethylene from 100 psia, - 40oF to 200 psia. The adiabatic efficiency of the compressor is 75%. Include your calculations and Mollier chart.

Figure 1a PFD for the Production of Acrylic Acid from Propylene

(7) For the accrylic process shown in Figure 1a (Turton et al, Analysis, Synthesis, and Design of Chemical Processes), check the design specifications for the inlet air blower C-301 (power = 2260 kW) against the heuristics in Table 3.6 (Lecture Notes). The air flow rate is 1362.9 kmol/h.

(8) A reciprocating compressor has been selected to compress 0.085 m3/s of 25oC methane gas from 100 to 6200 kPa. Assuming that the heat capacity remains constant at 2433 J/(kg∙K) over the temperature range of compression and that the ratio of Cp/Cv remains constant at 1.31. How many stages of compression should be used if the compression ratio is smaller or equal to 5. What is the power requirement if the compressor exhibits an efficiency of 80 percent? What is the exit temperature of the gas at the exit from the first stage? If the temperature of the cooling water can only increase by 15oC, how much water is required for the intercoolers and aftercooler to ensure that the compressed gas from each stage after cooling is again returned to 25oC?


[1] Dr. Pang's Notes