LNG AGRU Designs for feed es with low CO 2 content Dr. Torsten Katz Justin Hearn
Common OASE unit setup for CO 2 removal also best suited for low CO 2 containing feed es? Water make-up Older LNG plants CO 2 content > 4 % Most recent plants Shale / coal seam / pipeline: CO 2 content < 2% Absorber vessel Regenerator 2
Where is the coming from? Gas from the grid is dehydrated shows a low water content may contain traces of glycols From the well Often water saturated May contain hydrate inhibitors (MeOH, MEG, ) 3
How glycols affect operations In Salah sales plant, Algeria 350 ppbv TEG 52 C Glycol build-up in amine Due to glycol vapor pressure + liquid entrainment Limitation of plant throughput Dr. Torsten Katz, Dr. Georg Sieder, Justin Hearn LRGCC February 2013 Operational countermeasure Partial change-out of amine solution at 6 wt.% TEG in amine 4
How glycols affect operations In Salah sales plant, Algeria treated TEG free In Salah AGRU 1000 MMSCFD 350 ppbv TEG Dr. Torsten Katz, Dr. Georg Sieder, Justin Hearn LRGCC February 2013 Proposed countermeasure during design phase Install water wash-column upstream AGRU to minimize glycol contamination 5
Number of glycol-affected OASE reference units in LNG and Sales Gas applications 34 16 13 5 3 < 0.5 wt% 0.5-1 wt% 1-4 wt% 4-10 wt% > 10 wt% As is view by BASF September 2016 Capacity constraints Likely for plants with more than 4 wt.% glycol in the OASE solution 6
Minimizing OASE solvent losses for a water saturated feed Water make-up 0 X Solvent loss [% of an initial solvent fill / year] > 300% 35 C / 95 F 1 vol% CO 2 H 2 O saturated 7
Minimizing OASE solvent losses for a water saturated feed Skimming! Propane chiller Water bleed Solvent loss [% of an initial solvent fill / year] 53% 35 C / 95 F 1 vol% CO 2 H 2 O saturated 8
Solvent loss Minimizing OASE solvent losses for a water saturated feed Skimming! Propane chiller Water bleed Solvent loss [% of an initial solvent fill / year] < 5% possible (4-6 backwash trays) 35 C / 95 F 1 vol% CO 2 H 2 O saturated No. of stripper backwash trays 9
Temperatures inside the absorber in summer DH R 35 C / 95 F CO 2 content 2% 0.7% 0.2% 10
Temperatures inside the absorber in winter DH R 35 C 95 F 8 C 46 F CO 2 content 2% 0.7% 0.2% 11
Low temperatures lead to OASE solvent precipitation Solvent precipitates at T < 15 C 35 C 95 F 8 C 46 F Formation of precipitates 12
Proposed temperature control concept pre-heating e.g. plate and shell exchanger Minor impact Major impact Courtesy of GESMEX bypass around lean/rich exchanger Lean cooler only relevant for CO 2 feed content > 1.5% 13
Hydrocarbon and BTEX co-absorption depend strongly on operating conditions Case1 Case 2 CO 2 mol% 99.41 95.05 C1-C5 mol% 0.41 2.73 Benzene ppmv 868 9938 Toluene ppmv 865 11087 C6+ ppmv 8 80 Case1 Case 2 CO 2 mol% 2.0 0.2 C1-C5 mol% rest Benzene ppmv 400 Toluene ppmv 400 C6+ ppmv 2000 at 50% solvent flow 14
Hydrocarbon and BTEX co-absorption causes and consequences HC, BTEX C6, BTEX High caloric acid off Severe foaming High BTEX emissions Foaming starts here Heavy hydrocarbon and BTEX co-absorption increases with Partial feed flow rate Partial feed CO 2 content Low temperatures 15
Measures for minimizing BTEX and C6+ co-absorption C6, BTEX Skimming C6, BTEX 37 C 113 C 99 F 235 F T Skimming Skimming X A/B/C/D 16
Measures for minimizing BTEX and C6+ co-absorption C6, BTEX C6, BTEX Case 2 Case 3 CO 2 mol% 95.05 97.89 C1-C5 mol% 2.73 1.15 Benzene ppmv 9938 4565 Toluene ppmv 11087 4970 C6+ ppmv 80 23 8 C 46 F 35 C 95 F X A/B/C/D 25% turndown or lower 17
Summary AGRU designs for treating low CO 2 containing es (< 2 vol%) must address: The source of the feed effect of glycols water saturation / amine losses Partial load conditions Winter/summer or day/night temperature changes in the feed Proper heavy hydrocarbon and BTEX handling 18
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Understanding the water balance for a pipline feed in water make up AGRU wet treated D E H Y mole sieve cooler/ chiller acid off dry treated water bleed out
Understanding the water balance for a pipline with Dehydration-water-recycle loop feed in water make up AGRU wet treated D E H Y mole sieve cooler/ chiller acid off dry treated out recycle water
Understanding the water balance for a water saturated natural water bleed in feed AGRU wet treated D E H Y mole sieve cooler/ chiller acid off dry treated mole sieve bleed out recycle water