PREVENTING FOULING IN THE DEGASSING TOWER

By: Patrick LucasMike Hong

GE Water & Process Technologies

C 3/C 4

C 4 A cetylene

B utadiene

R affinate

C rude C4

R esidue

C 4/C 5

W aste W ater

P redistillation(Front End

D e-P ropyneizer)

M ainW asher

R ectifier

A fter W ash

D egassingTow er

A cetyleneW asher

B utadieneC olum n

SolventR egeneration

Typical NMP Process

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…)

Free Radical Generation

R - H

+

R

OH R-OOHR-O

O2, ΔMn+

R OO

R-H

O2

R H

Δ

I

Fouling Mechanisms

Factors Influencing Fouling

Feedstock Quality (diolefin concentration)Extraction Solvent QualityOperating Temperature Residence timeOxygen / PeroxidesCatalytic MetalsPolymer SeedsDesign (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 & 190°C using the High Temperature Corrosion test apparatus.

Evaluate efficiency of GE W&PT antifoulants

Fouling Test ProtocolSample: N-methyl-2-pyrrolidone (NMP) – Transfer to the

Vessel Tester3 mild steel coupons passivated with Sodium nitrite during 24

hoursCoupons introduction to the test vessel, 2 in the liquid and 1 in

the vapour/head spaceStirring (60rpm) and Nitrogen purge to adjust oxygen level at

10ppmNitrogen Pressurisation to 200 psiHeat at different temperatures: 150/170/190°CAfter 7 days test, check fouling and/or corrosion. If no Corrosion/Fouling, 14 days more testEvaluation of GE W&PT antifoulants

ResultsTest 1 – Blank - 150 0C.

Coupon Number

Starting weight (g)

Fouling on coupon

(mg)

Coupon weight loss (mg)

Corrosion rate (mpy)

1 (liquid) 6.8950 1.2 0.3 <0.1

2 (liquid) 6.7046 0.9 2 <0.1

3 (vapour) 6.7712 2 2 <0.1

Total filterable solids (ppm)

As received 10

21 days at 150 0C 83

ResultsTest 2 – Blank - 170 0C.

Coupon Number

Starting weight (g)

Fouling on coupon

(mg)

Coupon weight loss

(mg)

Corrosion rate (mpy)

1 (liquid) 6.6092 1.3 0.7 <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

ResultsTest 3 – Blank - 190 0C.

Coupon Number

Starting weight (g)

Fouling on coupon

(mg)

Coupon weight loss (mg)

Corrosion rate (mpy)

1 (liquid) 6.7341 10.6 0.9 <0.1

2 (liquid) 6.7905 11.8 0.7 <0.1

3 (vapour) 6.8666 3.5 4 <0.1

Total filterable solids (ppm)

As received 10

7 days at 190 0C 478

ResultsTest 4 – 190 0C with 100ppm Petroflo 20Y14 added.

Coupon Number

Starting weight (g)

Fouling on coupon

(mg)

% Inhibition Coupon weight

loss (mg)

1 (liquid) 6.7164 2.1 80.2 0.7

2 (liquid) 6.3358 1.9 83.9 0.4

3 (vapour) 6.7820 2.3 34.2 2

Corrosion rate (mpy)

<0.1

<0.1

<0.1

Total filterablesolids (ppm)

As received 10

7 days at 190 0C 92 80.8

% InhibitionTotal filterable solids (ppm)

% Inhibition

ResultsTest 5 – 190 0C with 50ppm Petroflo 20Y14 added.

Coupon Number

Starting weight (g)

Fouling on coupon

(mg)

% Inhibition Coupon weight

loss (mg)

1 (liquid) 3.2195 4.9 53.8 0.6

2 (liquid) 3.1853 4.5 61.9 1.1

3 (vapour) 3.2264 2.5 28.8 3

Corrosion rate (mpy)

<0.1

<0.1

<0.1

Total filterablesolids (ppm)

As received 10

7 days at 190 0C 246 48.5

% InhibitionTotal filterable solids (ppm)

% Inhibition

ResultsTest 6 – 190 0C with 100ppm Petroflo 20Y3151 added.

Coupon Number

Starting weight (g)

Fouling on coupon

(mg)

% Inhibition Coupon weight

loss (mg)

1 (liquid) 3.2121 0.2 98.1 0.3

2 (liquid) 3.2037 0.2 98.3 0.2

3 (vapour) 3.2254 1.4 60 1.4

Corrosion rate (mpy)

<0.1

<0.1

<0.1

Total filterablesolids (ppm)

As received 10

7 days at 190 0C 80 83.3

% InhibitionTotal filterable solids (ppm)

% Inhibition

ResultsTest 7 – 190 0C with 50ppm Petroflo 20Y3151 added.

Coupon Number

Starting weight (g)

Fouling on coupon

m(g)

% Inhibition Coupon weight

loss (mg)

1 (liquid) 3.2427 0.4 96.2 0.5

2 (liquid) 3.1929 0.4 96.6 0.5

3 (vapour) 3.1243 1.9 45.7 1.5

Corrosion rate (mpy)

<0.1

<0.1

<0.1

Total filterablesolids (ppm)

As received 10

7 days at 190 0C 82 82.8

% InhibitionTotal filterable solids (ppm)

% Inhibition

Petroflo 20Y3151: Antioxidants + Antipolymerant, NMP based

FeaturesNMP based – No risk of solvent contamination - Minimize foaming

Butadiene Inhibitor for Extractive Distillation Section

(BASF Design)Best Product

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 peroxidesNaNO2 Wash (Oxygen scavenger)Control operating temperaturesMinimize C5

+ contaminationReduce dead spacePassivate before start-upMinimize corrosion by-productsUse an adapted treatment program

PREVENTING FOULING IN THE DEGASSING TOWER

By: Patrick LucasMike Hong

GE Water & Process Technologies