1. The overhead composition of a distillation column is made up of components C-10 (16%), C-20 (1%), and C-30 (1%) which should always add up to 100%. 2. Process variables such as pressure drop, reflux rate, and reboiler temperature can be used to detect flooding on distillation trays. An increase in reflux rate with the reboiler on automatic temperature control would cause the cooling water outlet temperature to rise, indicating higher vapor flow through the trays. 3. If the reflux control valve fails open, the column pressure will stay the same, reflux flowrate will increase, column top temperature will go down, and the level

1. Test 1
1. What is the overhead composition?
 Matter is neither created nor destroyed, so the starting and ending
percentages should all add to 100%
1. C-10: 16%
2. C-20: 1%
3. C-30: 1%
4. List three process variables that can be used to break a flood and
explain why:
a) Performa pressure drop survey across the tower. If the P (pressure drop) istoolow,
it meansthe distillationtraysare dumpingorweeping. If the Pis toohigh,it means
the trays are floodedorentraining.
b) See if an increase in the refluxrate (with the reboileronautomatic temperature
control – TRC) causesthe coolingwater outlettemperature to rise. The higherreflux
rate increasesthe reboilerdutywhichwill increasethe vaporflow throughthe trays.
c) Determine whetheran increase in temperature in the reboilercausesthe steam flow
to the reboilerto increase.
5. In the following graphic, EXPLAIN what would happen if the reflux
control valve fails to close (FAILED OPEN)?
 The pointwhere more reflux hurtsdistillationinsteadof helpingiscalledthe “incipientflood
point”. Beyondthispoint, the distillationtoweris operatingin a positive feedbackmode
of processcontrol. That means that tray floodingreducestray fractionation efficiency.
a) Columnpressure willSTAYTHE SAME…
b) Reflux flowrate willINCREASE…
c) Columntoptemperature willGODOWN…
d) The level inD-100 will DECREASE
6. Explain what happens when FIC-203 fails Closed
 The reflux rate dependsonthe amountof steambeingcondensedtowaterinthe overhead
condenser. Havingthe flowcontrol valve shutwillpreventthisfromhappening.
7. Explain what happens with Ti-204
 Temperature will STAYTHE SAME…

2. 8. Explain what happens with PIC-204
 Pressure fromthe reflux drumwill INCREASE…
9. Explain what happens with TIC-203
 Temperature will DECREASE…
10. Explain what happens when FIC-300 fails Closed
 Reducingcoolingwaterflowwill INCREASEthe temperature inthe condenserandreduce its
duty. The vaporpressure of the liquidinthe reflux drumwill INCREASE.
11. Explain what happens with LIC-204
 The level of the reflux drumwill DECREASE
12. Explain what happens with AT-2
 It will receiveasignal thatButane reflux flow has DECREASED
13. Explain what happens with LIC-204A
 Level will DECREASE…
14. Explain what happened when CV-15 FAILS OPEN?
 It will continuouslyINCREASEthe temperature of the Kettle Reboiler,sendinghotvaporto
bottomof distillationcolumnandincreasingthe temperaturegradientupwards.
a) Why has Tray 8 temperature INCREASED?
o An excessof heathasrisenthe temperature fromthe bottomtothe top.
b) Why has the Reflux flow rate INCREASED?
o More hot gasespushedupwardsandenteringthe overheadcondenser
continuously.
c) Why has P-104flow rate DECREASED?
o There islessbottomsproductto be cycleddownto the pumpsince
d) Why has P-103flow rate INCREASED?
o More of the lighterproductleavingthe overheadcondenserisheadedtothe reflux
drum andraisingthe level of accumulatedproductsothatthe excessneedstobe
continuouslypumpedoutof the drum.

3. 15. Explain what happens when FIC-205 FAILS OPEN?
 An excessof heatstreamstill overheatbottomsproductandreflow itbackto column.
16. Explain why AT-3 goes DOWN?
 Since the mayorportionof mixture inheat exchangerisbeingredirectedtocolumn,there is
lesscirculatingproductsenttotanks.
17. Explain why LIC-205 goesDOWN?
 The product isemptyingfromexchangerintocolumn.
18. Explain why TIC-205 goes UP?
 Since FIC-205 failsopen,anexcessof heatbringsup the temperature insidevessel.
19. Explain what happens when LIC-205 FAILS OPEN?
 It followsthe same principle aswhendrainingyourbathtub:the liquidpumpsoutof heat
exchangertothe tanks.
20. Explain why Li-205 goes DOWN?
 The level of productwithinthe vesselflowsouttoheatexchangerEx-202.
21. Explain why AT-3 goes UP?
 A surplusof overflowcomingfromheatexchangerEx-205is redirectedtoEx-202.
22. Explain why TIC-205 goes DOWN?
 Since lessvaporfromheatexchangerEx-205 iscomingintothe column,the heatand
pressure are reduced.