Vintage Tailgas Treatment Unit, new Performance Two... · Vintage Tailgas Treatment Unit, new Performance M iddle E ast S ... circulated amine solution ... Vintage Tailgas Treatment

Vintage Tailgas Treatment Unit, new Performance Middle East Sulphur Plant Operations, Network 2016 9-11 October in Abu Dhabi, United Arab

BP Gelsenkirchen GmbH Pamela d‘Anterroches

Stefan Below Sebastian Kordes

OASE® Gas Treatment Harish Khajuria Thomas Ingram Gerald Vorberg

MESPON 2016, G. Vorberg 2

Agenda Fundamentals

Boundaries / Constraints in Tail Gas Treatment

Improvement Approach for a TGTU

Solvents in TGTU Service

Further Aspects

Plant trial at BP Gelsenkirchen

The BP Gelsenkirchen Refinery / The TGTU

Improvement Strategy / Test Procedure

The Plant Trial

Outline of the Parametric Studies

Summary

Rules of Thumb for an existing Unit?


Question / Task

How to improve the Performance of an existing Tail Gas Treatment Unit?

Definitions/Abbreviations:

H2S Amine Loading → molH2S/molamine

H2S Partial Pressure (mbar) → Gas Pressure x H2S conc.

Steam/Circ. Rate Ratio → kg/hsteam per tons/hcirculated amine solution

H2S Isotherm → vapour liquid equlibrium (VLE)

Disclaimer: Assumptions/rules of thumb refer to individual cases and marked with !


Boundaries in Tail Gas Treatment Feedgas Pressure → 1.2 bara / 17.4 PSI

Feedgas Temperature → 35 – 45 °C / 95 – 113 °F

Lean Amine Temperature → 35 – 55 °C / 95 – 131 °F

H2S Feed Concentration → 1 vol% (0.8 – 6vol%)

CO2 Feed Concentration → 20 – 30 vol% (5 – 50 vol%)

H2S Treated Gas Specification → < 5 / < 50 / < 100 vppm (250 vppm)

CO2 Treated Gas Specification → maximum slip


Lean Amine Temperature → strong impact on H2S selectivity

H2S Feed Gas Partial Pressure → low amine acid gas capacity

Low Amine Acid Gas Capacity → high liquid / gas ratio

High Liquid / Gas Ratio → lower CO2 slip

H2S Treated Gas Partial Pressure → high steam / circ. rate ratio

Constraints in Tail Gas Treatment


Lean Amine Temperature

> 45 °C/113 °F → H2S selectivity decreases significantly

Lean amine temperature has a strong impact on H2S treated gas specification (Fig.)

Heat transfer is affected by fouling in most lean amine air coolers


H2S Treated Gas Specification vers. Lean Amine Temperature

!

!

*trade off between heat transfer coefficient and fluid heat capacity

Example for a given MDEA design

Lower amine circulation rate may improve amine cooler performance in most cases*


H2S Partial Pressure

Feed Gas pH2S ~ 12 mbar1) → relatively low acid gas capacity of MDEA based solvents

Treated Gas pH2S ~ 0.055 mbar2) → “ultra low“ amine lean loading required

Up to 2/3 of rich amine solvent loaded with CO2 / ~ 1/3 of strip steam is used to heat up solvent rather than reversing the H2S absorption reaction (reaction enthalpy)

Steam/Circ. Rate Ratio for a given MDEA based design at 35°C

!


! Lower amine circulation rate allows an increase of steam / circulation rate ratio (Fig.)

H2S Treated Gas Specification vers. Lean Amine Temperature

1)ppH2S: 1vol% x 1.2 bara=12 mbar / 2) ppH2S: 50 vppm x 1.1 bara=0.055 mbar

MESPON 2016, G. Vorberg

Approach for an existing TGTU

Increase / double acid gas capacity of existing MDEA based solvent

Decrease solvent circulation rate at same steam feed rate

Expected Results

Substantial decrease of H2S in treated gas

Slight increase of CO2 slip in treated gas

Positive effect on heat exchangers


8


Solvents in TGTU Service

„Generic MDEA“ Methyldiethanolamine

CO2 reaction kinetically hindered, H2S react. nearly instantaneous

H2S + R1R2R3N ⇄ HS- + R1R2R3NH+

CO2 + 2H2O ⇄ HCO3- + H3O+

H2S amine rich loading around 0.03 – 0.1 mol/mol

Strip Steam Ratio 85 – 130 kg/tosolvent

„Acidified MDEA“ Methyldiethanolamine

Addition of acid shifts equilibrium in stripper towards H2S → lower regeneration energy

MDEAH+ + HS- ⇄ MDEA + H2S

H2S amine rich loading around 0.03 – 0.1 mol/mol

Strip Steam Ratio 75 – 100 kg/tosolvent

„Severely hindered Amine“ H2S Selectivity due to (severely) steric hinderance of N-group

Fast kinetics for H2S

H2S amine rich loading at least double of MDEA

+H+

Amine Mechanism Specifics

!

!

!

Examples for severely hindered Amines

+H+


Further Aspects

H2S Amine Lean Loading

H2S forms a protective layer

Carbonic acid at top of the absorber

H2S isotherm critical for individual solvent

Stripper Backwash Section

Condenser reflux depends on steam/circ. rate ratio

Reflux prevents from amine losses

Increased steam/circ. rate ratio beneficial for condenser reflux

H2S Isotherm / VLE at given temp.

Generic MDEA

Promoted MDEA

Reflux Rate vers. Circulation Rate

At a fixed steam feed rate

~50 vppm


Trial

Vintage Tailgas Treatment Unit, new Performance - Plant Trial at BP Gelsenkirchen -


The BP Gelsenkirchen Refinery

• The BP Gelsenkirchen site processes around 12 Mio tons crude oil per year

• Approx. 9 Mio tons/a are refined for fuel

• The site operates four CLAUS SRU trains incl. SCOT and Tail Gas Treatment

• Annual Sulfur production approx. 100,000 tons Picture & Scheme Courtesy of BP


The TGTU

TGTU 1 Basic Set Up

Revamp 1995 Absorber 12 Trays Desorber 16 Trays Feedgas: Temperature 35 – 40°C H2S conc. 0.8 – 1.3 v% CO2 conc. 22 – 35 v%

• TGTU design based on generic MDEA → H2S Spec. ~ 100 vppm

• Aim of the test → reduction of H2S emissions (SO2 at stack) at minimal costs

→ process optimization

Picture granted by BP


Improvement Strategy

Idea Increase of amine acid gas capacity by 60% Decrease in circulation rate by 30 to 40% Constant steam feed rate

Prerequisites - Utilize existing MDEA inventory - Uninterrupted operation (“on the fly”) - Smooth changes of parameters - No negative impact on existing equipment - No equipment modifications

Acid Offgas

Feed Gas

Treated Gas


Test Procedure Milestones & Considerations

Status Quo Evaluation Feasibility Plant Test

Design Review

Data Collection

Modelling of Status Quo

Operational Scenarios

System Variables

Optimization Strategy

“Prior-Test

Optimization”

Onsite Measures Data Evaluation

Risk Assessment

Expected Results

Planning of Test Procedure

Milestones:

Circulation Rate current operation at 68 – 75% at equilibrium Tray Hydraulics allow reduction in circulation rate by 70% is possible System Set Points circulation reduction by 40% is feasible Acid Gas Lean Loading should not be too low (protective FeXSX layer) Impact on Equipment reflux stream→ backwash efficiency, heat exchangers…

Considerations:


Plant Trial Promoter Dosage

Promotor components were dosed to the existing MDEA inventory 100% of target promoter concentration was reached after 70 hours Promoter components and solvent were analysed

100% of Promoter Target Concentration (NOT real concentration)

Component B

Component A

Component B

Component A Total Promoter Concentration (Percentage of Target Concentration)


Plant Trial Adjustment of Amine Circulation Rate

During promoter dosage, circulation rate was gradually decreased Steam feed rate and all other parameters were kept constant (steam/solvent ratio increased)

Each phase was controlled by simulation

Total Promoter Concentration (Percentage of Target Concentration)

Amine Circulation Rate (Percentage of Design)


Plant Trial Results

Treated gas was analyzed online by Micro-GC H2S concentration dropped, CO2 slip slightly increased Test results matched with simulation model Additional parametric testing was carried out

Parametric Testing

H2S Conc.

CO2 Conc.

83 vppm

15 vppm

Amine Circulation Rate (Percentage of Design)


Displayed parametric studies are only for this particular plant Steam feed rate and lean amine temperature were kept constant (steam/solvent ratio increased)

Parameter variation of circulation rate shows substantial improvement Promoted MDEA based solvent now allows a wide range in operational flexibility

Plant Trial Parametric Results

Generic MDEA

New Promoted MDEA


Displayed parametric studies are only for this particular plant Promoted solvent achieves much lower H2S spec. at similar temperature Changed isotherm provides much lower H2S specification Very low H2S specifications possible, even at high lean amine temperatures


Generic MDEA

New Promoted MDEA


Displayed parametric studies are only for this particular plant Reduction in solvent circulation rate allows an increase of steam/circ. rate ratio This means H2S spec. will be lowered if steam feed rate is kept constant Proof of concept!


Generic MDEA

New Promoted MDEA


Summary

A new promoter system was added to MDEA during operation

The increased acid gas capacity allowed an amine circulation reduction of 30%!

All other operational parameters were kept constant

H2S treated gas specification dropped from 83 vppm to 15 vppm

Parametric studies for this plant confirmed simulation model

Solvent is successfully in operation since March 2016

Proof of concept for this improvement strategy was made

New solvent allows even more stringent specifications in grassroots designs

Together with other measures BP Gelsenkirchen lowered SO2 emissions by 40%!

Rules of Thumb for an existing Unit? MDEA performance can be improved without changing inventory / equipment

Promoter will be added to existing MDEA inventory

H2S treated gas concentration can be reduced by at least 60 vppm

Stringent H2S possible at high amine temperatures


- 30% circ. rate + 35 K amine temp.

- 30% circ. rate - 60 vppm H2S

Yellow T


Acknowledgment Pamela d‘Anterroches, BP Gelsenkirchen, Germany

Technology / Ops. Experts / Site Development

Stefan Below, BP Gelsenkirchen, Germany

Technology / Ops. Experts / Energy Efficiency

Sebastian Kordes, BP Gelsenkirchen, Germany

Technology / Ops. Experts / Site Development

Thomas Ingram, BASF SE, Germany OASE® Gas Treatment

Gas Treatment Research

Thank You!

Documents

Vintage Tailgas Treatment Unit, new Performance Two... · Vintage Tailgas Treatment Unit, new Performance M iddle E ast S ... circulated amine solution ... Vintage Tailgas Treatment