PREVENTING FOULING IN THE DEGASSING TOWER
By: Patrick Lucas Mike Hong GE Water & Process Technologies
Typical NMP Process
P red i lati n stil o (F ro nt E nd D e- P ro p ynei zer) R ecti er fi D eg assi ng To w er B utad i ene C ol n um
C 3 /C 4 R affi nate
C 4 A cetyl ene
B utad i ene
C 4 /C 5
C rud e C 4
W aste W ater
M ai n W asher
A fter W ash
A cetyl ene W asher Sol vent R eg enerati n o
R esi ue d
BASF NMP Process
Fouling Mechanisms
Free Radical Polymerization initiated by: -- Alkyl Free Radicals usually heat and metals induced -- Peroxy Free Radicals originate from peroxide decomposition Aldol Condensation: -- Acetaldehyde, most common carbonyl -- BD copolymer formation Diels Alder Reaction: VCH Inorganics deposition (Sodium/Silicons/Corrosion products)
Fouling Mechanisms Free Radical Generation
O2 R-H
Mn+ O2 ,
RH
R OO
R-O + OH
R-OOH
R-H
Factors Influencing Fouling
Feedstock Quality (diolefin concentration) Extraction Solvent Quality Operating Temperature Residence time Oxygen / Peroxides Catalytic Metals Polymer Seeds Design (high dead spaces/stagnant areas,) Inhibitor system employed -- kinetics -- concentration required
Butadiene BASF Design FOULING TEST/INHIBITION TEST ON NMP TO DEGASSING COLUMN
Objectives
Evaluate the ability of the NMP to polymerize (foul) at different temperatures 150/170 & 190C using the High Temperature Corrosion test apparatus. Evaluate efficiency of GE W&PT antifoulants
Fouling Test Protocol
Sample: N-methyl-2-pyrrolidone (NMP) Transfer to the Vessel Tester 3 mild steel coupons passivated with Sodium nitrite during 24 hours Coupons introduction to the test vessel, 2 in the liquid and 1 in the vapour/head space Stirring (60rpm) and Nitrogen purge to adjust oxygen level at 10ppm Nitrogen Pressurisation to 200 psi Heat at different temperatures: 150/170/190C After 7 days test, check fouling and/or corrosion. If no Corrosion/Fouling, 14 days more test Evaluation of GE W&PT antifoulants
Results
Test 1 Blank - 150 0C.
Coupon Number Starting weight (g) Fouling on coupon (mg) 1.2 Coupon weight loss (mg) Corrosion rate (mpy)
1 (liquid)
6.8950
0.3
<0.1
2 (liquid)
6.7046
0.9
<0.1
3 (vapour)
6.7712
<0.1
Total filterable solids (ppm)
As received
10
21 days at 150 0C
83
Results
Test 2 Blank - 170 0C.
Coupon Number Starting weight (g) Fouling on coupon (mg) 1.3 Coupon weight loss (mg) 0.7 Corrosion rate (mpy)
1 (liquid)
6.6092
<0.1
2 (liquid)
6.7033
1.1
0.7
<0.1
3 (vapour)
6.8278
2.5
2.7
<0.1
Total filterable solids (ppm)
As received
10
14 days at 170 0C
122
Results
Test 3 Blank - 190 0C.
Coupon Number Starting weight (g) Fouling on coupon (mg) 10.6 Coupon weight loss (mg) Corrosion rate (mpy)
1 (liquid)
6.7341
0.9
<0.1
2 (liquid)
6.7905
11.8
0.7
<0.1
3 (vapour)
6.8666
3.5
<0.1
Total filterable solids (ppm)
As received
10
7 days at 190 0C
478
Results
Test 4 190 0C with 100ppm Petroflo 20Y14 added.
Coupon Number Starting weight (g) Fouling on coupon (mg) 2.1 % Inhibition Coupon weight loss (mg) 0.7 Corrosion rate (mpy)
1 (liquid)
6.7164
80.2
<0.1
2 (liquid)
6.3358
1.9
83.9
0.4
<0.1
3 (vapour)
6.7820
2.3
34.2
<0.1
Total filterable % Total (ppm) solidsfilterable % Inhibition solids (ppm) Inhibition As received 10
7 days at 190 0C
92
80.8
Results
Test 5 190 0C with 50ppm Petroflo 20Y14 added.
Coupon Number Starting weight (g) Fouling on coupon (mg) 4.9 % Inhibition Coupon weight loss (mg) 0.6 Corrosion rate (mpy)
1 (liquid)
3.2195
53.8
<0.1
2 (liquid)
3.1853
4.5
61.9
1.1
<0.1
3 (vapour)
3.2264
2.5
28.8
<0.1
Total filterable % Total (ppm) solidsfilterable % Inhibition solids (ppm) Inhibition As received 10
7 days at 190 0C
246
48.5
Results
Test 6 190 0C with 100ppm Petroflo 20Y3151 added.
Coupon Number Starting weight (g) Fouling on coupon (mg) 0.2 % Inhibition Coupon weight loss (mg) 0.3 Corrosion rate (mpy)
1 (liquid)
3.2121
98.1
<0.1
2 (liquid)
3.2037
0.2
98.3
0.2
<0.1
3 (vapour)
3.2254
1.4
60
1.4
<0.1
Total filterable % Total (ppm) solidsfilterable % Inhibition solids (ppm) Inhibition As received 10
7 days at 190 0C
80
83.3
Results
Test 7 190 0C with 50ppm Petroflo 20Y3151 added.
Coupon Number Starting weight (g) Fouling on coupon m(g) 0.4 % Inhibition Coupon weight loss (mg) 0.5 Corrosion rate (mpy)
1 (liquid)
3.2427
96.2
<0.1
2 (liquid)
3.1929
0.4
96.6
0.5
<0.1
3 (vapour)
3.1243
1.9
45.7
1.5
<0.1
Total filterable % Total (ppm) solidsfilterable % Inhibition solids (ppm) Inhibition As received 10
7 days at 190 0C
82
82.8
Butadiene Inhibitor for Extractive Distillation Section (BASF Design)
Best Product
Petroflo 20Y3151: Antioxidants + Antipolymerant, NMP based Features NMP based No risk of solvent contamination - Minimize foaming
Benefits
Prevent both polybutadiene and popcorn formation in the EDS Increase equipment runlength and production Reduce foaming and maintenance cost
GE W&PT Best Practices
Minimize oxygen and peroxides NaNO2 Wash (Oxygen scavenger) Control operating temperatures Minimize C5+ contamination Reduce dead space Passivate before start-up Minimize corrosion by-products Use an adapted treatment program
PREVENTING FOULING IN THE DEGASSING TOWER
By: Patrick Lucas Mike Hong GE Water & Process Technologies
