Some Distillation Column Remaining Design Issues
1. Feed tray and concentration, expected rate. Do both a) ideal for continuous
column making necessary assumptions, and b) from data last week on approx.
concentrations in column.
2. Reboiler and feed heater (reflux heater also?) design:
a. Heating element: power needed (expected vapor flow x delta H, vap +
heat losses + reflux.- heat provided by feed heater and any reflux
heating.). . .at 2 ml/min need extra approx. 70 watts to boil the feed. If we
reflux at expected ratios, will we need the heating tape to also provide
additional heating to upper part of column? Or will we be able to operate
at reasonable SST with higher vapor loads below the feed and higher
liquid loads above, etc. (Can we model this in ASPEN?)
b. Watt density for pool boiling, not exceeding max. leading to burnout in
film boiling regime.
c. Diameter. To fit in glass pipe. If we use the 1” thermosyphon design, will
the expected vapor flow exceed what is feasible given annulus area
(superficial velocity too high?).
d. Length. Availability in time frame. To fit in thermosyphon such that we
have most of surface above inlet tee. To have correct watt density at the
point of correct amount of power to provide expected vapor flow rate at
SST.
e. If thermosyphon not practical at this point, go to simple boiler design? If
so, size so that the bottoms volume changes concentration in reasonable
time frame so that we can get to SST at several operating conditions in the
3 hours (or 3 hrs by 2 lab periods) provided for in 4860 course. Also
design so that volume changes can be seen for adjustment of bottoms for
rate to sst (need to measure) distillate rate, feed rate, and bottoms rate to
get to approx. SST from mass balance.
f. Provide sampling point for bottoms, keeping in mind safety, etc.
g. Mechanical issues for reboiler: will it fit in compartment on the bottom of
the column?
h. Design boiler tests prior to final design and mount to determine some of
the above.
i. How will be mount the reboiler so as to be mechanically stable?
What hardware will we need to order?
ii. How will we adapt the SST flange with the ½” NPT fitting, to the
glass column flanges?
iii. How will we either drain or pump the bottoms out?
i. Electrical Issues:
i. Adequate ventilation and sealed connections to prevent fire.
ii. Locate so as to unlikely be exposed to flammable liquid
iii. Combine connections so that we have master stop switch in case of
emergency.
iv. How to best combine control of boiler and feed heat input.
3. Feed pump. Need to select and purchase the appropriate feed tubing. Select on
basis of:
a. Chemical compatibility
b. Strength and compression resistance
c. Diameter to give design flows at reasonable RPM.
d. Is it possible to:
i. Set the feed rate of the pump
ii. Measure distillate rate
iii. Determine bottoms rate from mass balance (or watching bottoms
level)
iv. Pump out with same peristaltic pump as the feed? Would expect
that the bottoms flow will be less than the feed so we will need to
select the ratio of diameter of feed tubing to the ratio of the
diameter of the bottoms tubing so that it is approximate and then
set up recycle system so that we can take off some and return some
to keep balance (really can’t use valve on the positive displacement
peristaltic pump).
e. Feed pump safety:
i. Needs new cord
ii. Pinch hazard? Design cover?
iii. Location so as not to be hazard (fire) but to be easy access to feed
location?
4. From above:
a. Select and order all parts
b. Plan and test
c. Design/redesign
d. Assemble and test
e. Dismantle and make changes
f. Retest
g. Repeat a through f if necessary.
5. Temperature Measurement
a. Have ordered 3 hypodermic probes to replace 3 of the sample/feed ports
b. Mount T-type at top?
c. Mont T-type at bottom?
d. Design and hardware order for b and c.
e. Set up PC and data acquisition system
f. Write software
g. Set up mechanical/ physical location of the PC for safety/convenience and
incorporate in final location selection in W191 bay.
6. Test column and select experiments for class.
7. Analyze data.
8. Retest and analyze data: iterate on 6 and 7 to final experiment design.
9. Write out SOP and student instructions for experiment.
10. Write lecture notes to prep. Students for Exp.