Vintage Tailgas Treatment Unit, new Performance

Transcription

1 Vintage Tailgas Treatment Unit, new Performance Middle East Sulphur Plant Operations, Network 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

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? MESPON 2016, G. Vorberg 2

3 Question / Task How to improve the Performance of an existing Tail Gas Treatment Unit? Definitions/Abbreviations: H 2 S Amine Loading mol H2S /mol amine H 2 S Partial Pressure (mbar) Gas Pressure x H 2 S conc. Steam/Circ. Rate Ratio kg/h steam per tons/h circulated amine solution H 2 S Isotherm vapour liquid equlibrium (VLE) Disclaimer: Assumptions/rules of thumb refer to individual cases and marked with! MESPON 2016, G. Vorberg 3

4 Boundaries in Tail Gas Treatment Feedgas Pressure 1.2 bara / 17.4 PSI Feedgas Temperature C / F Lean Amine Temperature C / F H 2 S Feed Concentration 1 vol% (0.8 6vol%) CO 2 Feed Concentration vol% (5 50 vol%) H 2 S Treated Gas Specification < 5 / < 50 / < 100 vppm (250 vppm) CO 2 Treated Gas Specification maximum slip MESPON 2016, G. Vorberg 4

5 Constraints in Tail Gas Treatment Lean Amine Temperature strong impact on H 2 S selectivity H 2 S Feed Gas Partial Pressure low amine acid gas capacity Low Amine Acid Gas Capacity high liquid / gas ratio High Liquid / Gas Ratio lower CO 2 slip H 2 S Treated Gas Partial Pressure high steam / circ. rate ratio MESPON 2016, G. Vorberg 5

6 Improvement Approach for a TGTU! Lean Amine Temperature > 45 C/113 F H 2 S selectivity decreases significantly Lean amine temperature has a strong impact on H 2 S treated gas specification (Fig.) Heat transfer is affected by fouling in most lean amine air coolers H 2 S Treated Gas Specification vers. Lean Amine Temperature! Lower amine circulation rate may improve amine cooler performance in most cases* Example for a given MDEA design *trade off between heat transfer coefficient and fluid heat capacity MESPON 2016, G. Vorberg 6

7 Improvement Approach for a TGTU H 2 S Partial Pressure Feed Gas ph 2 S ~ 12 mbar 1) relatively low acid gas capacity of MDEA based solvents! Treated Gas ph 2 S ~ mbar 2) ultra low amine lean loading required Up to 2/3 of rich amine solvent loaded with CO 2 / ~ 1/3 of strip steam is used to heat up solvent rather than reversing the H 2 S absorption reaction (reaction enthalpy)! Lower amine circulation rate allows an increase of steam / circulation rate ratio (Fig.) H 2 S Treated Gas Specification vers. Lean Amine Temperature Steam/Circ. Rate Ratio for a given MDEA based design at 35 C 1 ) pp H2S : 1vol% x 1.2 bara=12 mbar / 2) pp H2S : 50 vppm x 1.1 bara=0.055 mbar MESPON 2016, G. Vorberg 7

8 Improvement Approach for a TGTU 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 H 2 S in treated gas Slight increase of CO 2 slip in treated gas Positive effect on heat exchangers MESPON 2016, G. Vorberg 8

9 Solvents in TGTU Service Amine Mechanism Specifics Generic MDEA Methyldiethanolamine CO 2 reaction kinetically hindered, H 2 S react. nearly instantaneous H 2 S + R1R2R3N HS - + R1R2R3NH + CO 2 + 2H 2 O HCO H 3 O + H 2 S amine rich loading around mol/mol Strip Steam Ratio kg/to solvent! Acidified MDEA Methyldiethanolamine +H + Addition of acid shifts equilibrium in stripper towards H 2 S lower regeneration energy +H + MDEAH + + HS - MDEA + H 2 S H 2 S amine rich loading around mol/mol Strip Steam Ratio kg/to solvent! Severely hindered Amine H 2 S Selectivity due to (severely) steric hinderance of N-group H 2 S amine rich loading at least double of MDEA! Fast kinetics for H 2 S Examples for severely hindered Amines MESPON 2016, G. Vorberg 9

10 Further Aspects H 2 S Amine Lean Loading H 2 S forms a protective layer Carbonic acid at top of the absorber H 2 S 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 H 2 S Isotherm / VLE at given temp. Generic MDEA Reflux Rate vers. Circulation Rate At a fixed steam feed rate ~50 vppm Promoted MDEA MESPON 2016, G. Vorberg 10

11 Trial Vintage Tailgas Treatment Unit, new Performance - Plant Trial at BP Gelsenkirchen - MESPON 2016, G. Vorberg 11

12 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 MESPON 2016, G. Vorberg 12

13 The TGTU TGTU design based on generic MDEA H 2 S Spec. ~ 100 vppm Aim of the test reduction of H 2 S emissions (SO 2 at stack) at minimal costs process optimization TGTU 1 Basic Set Up Revamp 1995 Absorber 12 Trays Desorber 16 Trays Feedgas: Temperature C H 2 S conc v% CO 2 conc v% Picture granted by BP MESPON 2016, G. Vorberg 13

14 Improvement Strategy Idea Increase of amine acid gas capacity by 60% Decrease in circulation rate by 30 to 40% Constant steam feed rate Treated Gas Acid Offgas Prerequisites - Utilize existing MDEA inventory - Uninterrupted operation ( on the fly ) - Smooth changes of parameters - No negative impact on existing equipment - No equipment modifications Feed Gas MESPON 2016, G. Vorberg 14

15 Test Procedure Milestones & Considerations Milestones: Status Quo Evaluation Feasibility Plant Test Design Review Data Collection Modelling of Status Quo Operational Scenarios System Variables Optimization Strategy Risk Assessment Expected Results Planning of Test Procedure Prior-Test Optimization Onsite Measures Data Evaluation Considerations: Circulation Rate Tray Hydraulics System Set Points Acid Gas Lean Loading Impact on Equipment current operation at 68 75% at equilibrium allow reduction in circulation rate by 70% is possible circulation reduction by 40% is feasible should not be too low (protective Fe X S X layer) reflux stream backwash efficiency, heat exchangers MESPON 2016, G. Vorberg 15

16 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) Total Promoter Concentration (Percentage of Target Concentration) Component A Component B Component B Component A MESPON 2016, G. Vorberg 16

17 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 Amine Circulation Rate (Percentage of Design) Total Promoter Concentration (Percentage of Target Concentration) MESPON 2016, G. Vorberg 17

18 Plant Trial Results Treated gas was analyzed online by Micro-GC H 2 S concentration dropped, CO 2 slip slightly increased Test results matched with simulation model Additional parametric testing was carried out 83 vppm Amine Circulation Rate (Percentage of Design) H 2 S Conc. CO 2 Conc. Parametric Testing 15 vppm MESPON 2016, G. Vorberg 18

19 Plant Trial Parametric Results 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 Generic MDEA New Promoted MDEA MESPON 2016, G. Vorberg 19

20 Plant Trial Parametric Results Displayed parametric studies are only for this particular plant Promoted solvent achieves much lower H 2 S spec. at similar temperature Changed isotherm provides much lower H 2 S specification Very low H 2 S specifications possible, even at high lean amine temperatures Generic MDEA New Promoted MDEA MESPON 2016, G. Vorberg 20

21 Plant Trial Parametric Results Displayed parametric studies are only for this particular plant Reduction in solvent circulation rate allows an increase of steam/circ. rate ratio This means H 2 S spec. will be lowered if steam feed rate is kept constant Proof of concept! Generic MDEA New Promoted MDEA MESPON 2016, G. Vorberg 21

22 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 H 2 S 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 SO 2 emissions by 40%! MESPON 2016, G. Vorberg 22

23 Rules of Thumb for an existing Unit? MDEA performance can be improved without changing inventory / equipment Promoter Yellow T will be added to existing MDEA inventory H 2 S treated gas concentration can be reduced by at least 60 vppm Stringent H 2 S possible at high amine temperatures - 30% circ. rate - 60 vppm H 2 S - 30% circ. rate + 35 K amine temp. MESPON 2016, G. Vorberg 23

24 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 MESPON 2016, G. Vorberg 24

25 Thank You!