Sulfur Determination In LPG And Gases By Antek

Question 1

2. Initial operating conditions

Answer 1

• check compressed gas cylinder pressure for argon and oxygen. Cylinder should be at a minimum of 400-500 psi. If below this level, cylinder should be changed out before beginning analysis.
• slowly turn Argon gas regulator valve up to ~45-46psi (mark on gauge). This increases the flow to membrane drier. Oxygen regulator pressure should never be changed
• open front door and check furnace temp. According to ASTM, it must be 1075+/-25*C
• turn the Gas box on and allow it to warm up for 15 minutes
• check moisture traps which are by the Argon gauge
• if Antek technician not logged on instrument, log on PC using your PIC code and password.
• system should be in shutdown method of instrument has been idle for a few hours
• go to main screen, select method tab and load proper method. This will increase gas flows of argon and oxygen to pyrolysis tube. Allow 30 minutes warm-up time
• after clicking “file”, click open file to load method for LPG
• the method for LPG samples is 734. Be sure the drop down is on 734. Check the post-it in instrument for last calibration date and match it to file with that date. Click open
• after losing method, gas flows will be reset for selected method. At any time. Press F7 to view instrument parameters using the mass flow controllers. Toggle this key to close mass flow controller screen. Losing method will increase flows to pyro tube.

Question 2

3. Sample preparation

Answer 2

• place cylinder in vertical position for a few minutes
• in hood, attach grounding strap. Slightly open bottom valve and dispense LPG sample on piece of HDPE to verify no particulates or water. If black particulates are evident, do not analyze sample. Call for resample because it failed workmanship. If water present, leave in vertical position drain off water and check again.
• in hood with grounding strap still attached bleed liquid from top valve until vapor appears
• detach grounding strap and pressure up cylinder with helium to liquefy LPG sample. Should be pressured at ~400psi

Question 3

4. Creating a Sample File

Answer 3

• it is necessary to create a sample file for LPG run. Decide whether a New File must be created if it exceeds the 24 he period from when last file created. If it doesn’t exceed 24 hr period, then run can piggyback on last file.
• select sample tab and either open file or new file. If it is same 24 hr period, load file. If it exceeds 24 hrs, create new file.
• depending on whether you chose new file or open file a list of samples and standards or a blank page appears. Select Run from bottom menu

Question 4

5. Initiation a Run Sequence

Answer 4

• after cylinder pressured with helium, attach grounding strap. Outage tube should be at top of cylinder
• be sure to click sound is heard that verifies quick connect is securely attached. Excessive force does not have to be exerted to “snap” the cylinder in place
• open bottom valve of sample cylinder and open front valve on injection strip. Increase in pressure should be on gauge. If gas box valve open, you will hear sample going to vent. Verify good sample flow.
• if not open, slowly open silver needle valve on gas box. When opening valve watch in sight glass to verify no bubbles present. Gently close needle valve. DO NOT tightly close this valve. Verify flow ball is a t mark on left yellow sight glass above the on knob.
• after previously clicking “sample”, it will ask you to select either New Sample for first run of a new sample or insert after to run another injection of same sample. When selecting new sample name it
• be sure the line is flushed and gas box valve closed before clicking “start run”. You can set up sample info first and then open cylinder and gas box valves. The order does not matter. You can even click start run and open gas box valves as long as it is closed before gas box sampling valve switched. 30 second delay before valve switches

Question 5

6. Interpreting the Results

Answer 5

• check plot to be sure peak did not flat top. Also, check baseline for excessive baseline noise and peak has been properly integrated
• sample should be analyzed minimum 3 times. If you see run that is much different than previous run, it may be necessary to run fourth time.
• to view all injections at one time, select view from bottom buttons, then “Sample Chart”
• if you select “injection chart” it will show the injections one at a time. Verify the peak has been properly integrated and baseline noise not excessive. Peak integration should be on same line as baseline. If you notice peak was not properly integrated, run another injection. If same problem exists on next run, notify a chemist
• if you don’t want to use a result, highlight the injection and select the B Use box.
• if a flat-top occurs it would indicate the sample is over the detection limit of calibration
• tank or sample density should be used to calculate the Wt. ppm. Data from Antek is in Vol. ppm and is converted to Wt ppm by dividing sulfur result by density to get answer in Wt ppm
• density for Butane is 0.58 and for Propane/Propylene is 0.51
• at least 3 injections must be used, and the RSD target is

Question 6

7. Data reporting

Answer 6

• be sure to record values in Vol. ppm and Wt ppm on sheet in Antek lab. Be sure to record data in BLISS and also on Finished Tank sheet
• limits for sulfur on propane and propylene are 80 wt ppm and butane is 200 wt ppm

Question 7

8. Conditioner

Answer 7

• it is necessary to run conditioner at beginning of each shift that you run a Finished Tank. Good idea to invert conditioner a few times before analyzing. Be sure attach grounding clamp before injecting
• place on Antek worksheet to record standard value. If you do not get finished LPG during your shift make sure you put NA in BLISS and add comment no finished LPG
• if cylinder low in volume get new cylinder with comparable range
• if LPG instrument down, it is expected the standard should be analyzed on backup instrument (#1)
• value for conditioner is written on cylinder
• no calculation based on density, answer reported in vol ppm. Should run +/- 1 vol ppm of what is written on cylinder. If conditioner does not hit after changing voltage, contact chemist over instrument before marking down
• if conditioner values low, conditioner cylinder may need to be repress used with helium. Do not exceed ~200psi

Question 8

9. Voltage adjustments

Answer 8

• when running conditioner, if value to high, lower voltage 3-5. Rerun conditioner to verify adjustment was correct. Antek technician and chemist should be notified regarding changes made. If answer to low, raise voltage 3-5. If you have to increase voltage large amount, indicates could be other issues , so contact chemist if this happens as well
• raise or lower voltage, go to Method tab, go to edit, edit hardware settings and raise or lower voltage. When you go back to sample tab, it will ask if you want to save settings and exit. Do that, then run conditioner

Question 9

10. Troubleshooting

Answer 9

• verify compressed cylinders are at proper pressure and not below ~500psi, if so they need changed
• verify argon has been turned up before beginning analysis
• DO NOT run analysis in shutdown method
• if conditioner is not within range after making voltage adjustments, it will be necessary to use backup instrument (Antek #1)
• pressing F7 key at any time will give you status of mass flow controllers. This could provide system operating conditions
• verify counts and values for sample make sense compared to calibration standards

Question 10

11. Instrument shutdown

Answer 10

• when analysis is complete, turn gas box off
• go to method tab, select file, open file, load 734 Shut down method and click open
• reduce the Argon gas to membrane drier by slowly turning regulator valve below the mark (~10psi) and raising it back to mark
• verify instrument is in shutdown method

Question 11

1. Purpose

Answer 11

Determine total sulfur content of LPG and gaseous hydrocarbon samples using ASTM D6667. It is primarily for determining total Sulfur content in Propane, Propylene, Butane, and Olefin samples. A heated sample valve used to inject gaseous samples, and LPG samples into a heated expansion chamber. Gaseous samples enter s high temperature oxygen rich combustion tube where sulfur compounds oxidized to SO2. Water produced from reaction is removed by membrane drier. Gas is subjected to UV light and enters less stable higher energy state. Fluorescence emitted from excited SO2 as it returns to ground state is detected by a photomultiplier tube. Resulting signal is proportional to sulfur concentration in original sample. Signal strength converted to total sulfur value.