1.Consider the following rea3ction:CO +2H2⇒CH3OH
The feed enters the reactor in stoichiometric amounts at 25°C and 1 atm, total flow: 30kmol/h.
The conversion with respect to CO is 100 %.
Step 1: Drawing the flow sheet(Feed, Stoichiometric Reactor, Product, Streams) /
Step 2: Setting engineering units: Format>Engineering Units
Step 3: Selecting components: Termophysical/Select Components menu item or .
Step 4: Entering the feed stream composition
Step 5: Entering the Reactor specs (double click on reactor)
Step 6: Running the simulation: Run>Runall or toolbar icon
Step 7: Retrieving the results: double clicking on the product stream.
Questions:
a. Calculate the standard heat of reaction and the adiabatictemperature.
b. Using the molar ratios of 2, 5 and 10 for the ratio of H2/CO findthe reactor effluent temperature as a function of these ratios.
c. For H2/CO ratio 2:1add 5, 10 and 100 kmole of n-dodecaneand find the change in the reactor effluent temperature.
2.A 10 kmol/h stream consisting of 60% n-octane and 40% n-hexadecane (mole basis) at 5 bar and500K is separated into vapor and liquid streams. The feed pressure is first reduced to1 bar in a valve before the separation in a flash column. Use the inlet T and P in the flash column.
Questions:
Determine the stream flows, compositions and temperatures of the vapour and liquid streams.
Temperature: ………. °C
Vapor: Flow rate ...... kmol/h; Composition: ...... % n-octane, ...... % n-hexadecane
Liquid: Flow rate ...... kmol/h; Composition: ...... % n-octane, ...... % n-hexadecane
3. Water is to be pumped for 0.8 km along a 50 mm internal diameter pipe at the rate of 3.0 kg/s, and then raised vertically 15 m. The pipe roughness is 0.045 mm. What is the pressure drop in the pipe?
Pressure drop: ………………….
If the pump has an efficiency of 50%, what power will be required?
Power: ………………..
4. Water is transported in a 40 mm pipe, 240 m long with 2.55 m lift. The pipe roughness is 5·10-5 m. If the pressure drop across this length of pipe is not to exceed 1.2 bar, what is the maximum allowable water mass rate?
5.Water is pumped from a 5 m deep well along a 25 mm diameter, 6 m long pipe at the rate of 1000 kg/h. The pipe roughness is 0.045 mm. The vendor of the pump requires 2.5 m NPSHr. Does the pump work well if the water temperature is a,20 °C b, 70 °C?(Feed pressure: 1 bar, pump output pressure: 3 bar)
6. A water pump was tested and the following data was obtained. (Qis quantity of flow, His head of water, is efficiency).
Pump characteristics:
Q (l/s) / 10 / 20 / 30 / 40 / 50H (m) / 10.5 / 10.0 / 8.5 / 6.0 / 2.5
/ 0.40 / 0.64 / 0.72 / 0.64 / 0.40
It is proposed to use this pump to draw water from an open sump to an elevation 5.5 m above. The delivery pipe is commercial steel, 20.0 m long and 100 mm diameter.
Find:
(a) the discharge that the pump can provide;
(b) the pump efficiency at this discharge;
(c) the input power required.
(On paper calculation: 111 m3/h; 72%; 3.5 kW)
7. Water is to be pumped from tank A to tank B (see figure below). The relative heights of free surfaces and the pump are shown in the figure, whilst pump characteristics at the operational speed are given below.
Q (l/s) / 3 / 6 / 9 / 12 / 18 / 21H (m) / 29.5 / 27.6 / 24.4 / 19.7 / 13.5 / 5.9
/ 29 / 54 / 73 / 80 / 70 / 38
The pipe is 10 m long before the pump and 30 m long after it. The pipe diameter is 0.06 m. The pipe roughness is 0.046 mm.
Find:
(a) the discharge that the pump can provide;
(b) the pump efficiency at this discharge;
(c) the input power required.
(On paper calculation: 38.7 m3/h; 77%; 2.98 kW; )
8. A 100 kmol/hr stream of 30 mol% n-pentane and 70 mol% n-heptane is fed to a continuous distillation column at bubble point and atmospheric pressure. 96 mol% of n-pentane in feed and 1 mol% of n-heptane in feed is desired to be present in the distillate stream. Determine the number of stages, if R/Rmin = 1.5
Design a continuous distillation column to meet the desired specifications using Shortcut columnin CHEMCAD.
9. A 100 kmol/hr stream of ethanol (50 mol%) and n-propanol (50 mol%) is fed to a continuous distillation column 1. at bubble point; 2. at dew point and atmospheric pressure. The pressure drop across the column is negligible and R/Rmin = 1.5is used. 93 mol% of ethanol in feed and 5 mol% of n-propanol in feed is desired to be present in the distillate stream.
Design a continuous distillation column to meet the desired specifications using Shortcut columnin CHEMCAD and report the
total number of stages: ………..
minimum number of stages: …………..
feed stage location: …………….
minimum and calculated reflux ratios: ……………. …………
final distillate stream concentrations: ……………….
final bottom stream concentrations:
reboiler heat duty: ……………..
condenser heat duty: ……………..
10. A 100 kmol/hr stream of ethanol (50 mol%) and n-propanol (50 mol%) is fed to a continuous distillation column at room temperature (25 °C) and atmospheric pressure. The column has 20 trays and the feed enters at the 10th tray. A reflux ratio of 1.5 is used for the column and a bottom stream with 93% n-propanol is desired.(K-value: NRTL)
Set up a distillation column simulation using SCDS columnin CHEMCAD and report the final a,distillate and b,bottom stream concentrations and the c,reboiler and d,condenser heat duties.
a:
b:
c:d:
11.Simulate the recovery of dimethylformamide form water solution by distillation. A 10000 kg/hr stream of water (42.5 m/m%) and DMF (57.5 m/m%) is fed to a continuous distillation column (SCDS column) at boiling point and atmospheric pressure. A bottom stream with 99.99 m/m% DMF is desired, the distillate will be with 98 m/m% water. (K-value: UNIQUAC) Run the simulation with 10 and 20 stages (the feed stage will be the 5th and 10th , respectively).
Which is the more preferable regarding to the heat duty of the reboiler? ……….
12. A gas mixture of air (4 kmol/hr) and hydrogen sulfide (2 kmol/hr) is to be absorbed by water so that hydrogen sulfide is recovered from the bottom stream. The absorber has 10 trays (SCDS column). Water (145 kmol/h) enters the absorber from 1st tray at 25 °C and 1 atm and gas feed enters from 10th tray at the same temperature and pressure as those of water. Simulate this absorber in CHEMCAD to determine the hydrogen sulfide recovery in the bottom stream.(K-value: Wilson)
Recovery: ……………..%
13.A gas mixture (20 L/min) of air (15.5 mol %) and carbon dioxide (4.5 mol %) is to be absorbed by water (4 L/min). The absorber is a packed column (SCDS column). The column has an inner diameter of 80 mm, and a packed height of 1.27 m. The packing material consists of dumped 3/8” Raschig rings. Water enters the absorber from the top at 25 oC and 1 bar and the gas feed enters from the bottom at the same temperature and pressure as those of water. Simulate this absorber and determine the composition of the gas leaving the absorber.
CO2: …………… mol%
14.Water is used as a solvent to extract ethanol from an ethanol-heptane mixture. For a ternary mixture containing water, ethanol, and n-heptane, simulate the Extraction experiment using LL Extractor in CHEMCAD. The extractor has 3 trays.For runs 1-3 use solvent flow rates of 25 g/min, 50 g/min, and 100 g/min respectively. Calculate the compositions of the Extract for each run. (K-value: UNIFAC LLE)
Temperature = 25 C; Pressure = 1 atm; Feed: 40 g/min ethanol, 60 g/min n-heptane.
25 g/min:50 g/min:
100 g/min: /
15. The “Condensate Stabilizer” Problem
It is a condensate stabilizer plant which is typical in the oil industry.
The feed is at 25C and 13.8 bars with the following flows in kg per hr:N2:1271, C1:32783; C2:7011; C3:4280; iC4:501; nC4: 475; iC5:655; nC5:458; nC6:547.
The design requirement:
The stabilized condensate (stream 9) must have a maximum propane content of 1mole%.
Design settings:
- K-Value: Peng-Robinson
- Heat exchanger 1: Pressure Drop: Stream 1 = 0.34 bars, Stream 4 = 0.34,
Specify Stream 2 @ dew point => V/F of stream 2 = 1.
- Heat exchanger 2: Pressure Drop = 0.34,
Temp Out Stream 3 = -20 °C. (Note: T=-20 °C determines V/F for flash unit 3).
- The flash (Unit op. 3) is a VL separator so it needs no extra specification; the defaults apply.
- Valve: Pressure Out = 8.6 bar.
- SCDS column (Unit. op 5):No condenser, 12 trays with Feed stage 1, Pdrop=0.34 bar. Specification for the reboiler (maximum propane content of 1 mole%).
Viewing Results
Determine the composition of
Stream 5: ………………………………………………..
Stream 9: ………………………………………………..